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Physical Review D

(Particles, Fields, Gravitation, and Cosmology - 1)

November 2009

Volume 80, Number 9 , partial issue

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RAPID COMMUNICATIONS
Rapid

Measurement of the e+e--->D0D*-pi+ cross section using initial-state radiation
G. Pakhlova et al. (Belle Collaboration)
Published 16 November 2009 (7 pages)
091101(R)  Full Text: PDF (220 kB)  | Buy Article
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We report measurements of the exclusive cross section for e+e--->D0D*-pi+ as a function of center-of-mass energy from the D0D*-pi+ threshold to 5.2 GeV with initial-state radiation. No evidence is found for Y(4260)-->D0D*-pi+ decays. The analysis is based on a data sample collected with the Belle detector at or near a center-of-mass energy of 10.58 GeV with an integrated luminosity of 695 fb-1 at the KEKB asymmetric-energy e+e- collider.
Rapid

Confusing nonzero theta13 with nonstandard interactions in the solar neutrino sector
A. Palazzo and J. W. F. Valle
Published 16 November 2009 (5 pages)
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Solar and KamLAND data are in slight tension when interpreted in the standard two-flavor oscillations framework and this may be alleviated allowing for a nonzero value of the mixing angle theta13. Here we show that, likewise, nonstandard flavor-changing interactions (FCI), possibly intervening in the propagation of solar neutrinos, are equally able to alleviate this tension and therefore constitute a potential source of confusion in the determination of theta13. By performing a full three-flavor analysis of solar and KamLAND data in presence of FCI we provide a quantitative description of the degeneracy existing between theta13 and the vectorial coupling epsilone taudV characterizing the nonstandard transitions between nue and nutau in the forward scattering process with d-type quarks. We find that couplings with magnitude epsilone taudV~10%, compatible with the existing bounds, can mimic the nonzero values of theta13 indicated by the latest analyses.
Rapid

Evidence for mirror dark matter from the CDMS low energy electron recoil spectrum
R. Foot
Published 9 November 2009 (5 pages)
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We point out that mirror dark matter predicts low-energy (ER<~2 keV) electron recoils from mirror electron scattering as well as nuclear recoils from mirror ion scattering. The former effect is examined and applied to the recently released low-energy electron recoil data from the CDMS Collaboration. We speculate that the sharp rise in electron recoils seen in CDMS below 2 keV might be due to mirror electron scattering and show that the parameters suggested by the data are roughly consistent with the mirror dark matter explanation of the annual modulation signal observed in the DAMA/Libra and DAMA/NaI experiments. Thus, the CDMS data offer tentative evidence supporting the mirror dark matter explanation of the DAMA experiments, which can be more rigorously checked by future low-energy electron recoil measurements.
Rapid

Yukawa alignment in the two-Higgs-doublet model
Antonio Pich and Paula Tuzón
Published 19 November 2009 (5 pages)
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In multi-Higgs-doublet models the alignment in flavor space of the relevant Yukawa matrices guarantees the absence of tree-level flavor-changing couplings of the neutral scalar fields. We analyze the consequences of this condition within the two-Higgs-doublet model and show that it leads to a generic Yukawa structure which contains as particular cases all known specific implementations of the model based on [script Z]2 symmetries. All possible freedom in the Yukawa sector gets parametrized in terms of three complex couplings sigmaf. In spite of having flavor conservation in the neutral scalar couplings, the phases of these three parameters represent potential new sources of CP violation.
Rapid

Bounding isotropic Lorentz violation using synchrotron losses at LEP
Brett Altschul
Published 10 November 2009 (4 pages)
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Some deviations from special relativity—especially isotropic effects—are most efficiently constrained using particles with velocities very close to 1. While there are extremely tight bounds on some of the relevant parameters coming from astrophysical observations, many of these rely on our having an accurate understanding of the dynamics of these high-energy sources. It is desirable to have reliable laboratory constraints on these same parameters. The fastest-moving particles in a laboratory were electrons and positrons at LEP. The energetics of the LEP beams were extremely well understood, and measurements of the synchrotron emission rate indicate that the isotropic Lorentz violation coefficient | kappa-tildetr-(4/3)c00| must be smaller than 5×10-15.
Rapid

Supersymmetric lepton flavor violation in low-scale seesaw models
Amon Ilakovac and Apostolos Pilaftsis
Published 12 November 2009 (5 pages)
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We study a new supersymmetric mechanism for lepton flavor violation in µ and tau decays and µ-->e conversion in nuclei, within a minimal extension of the minimal supersymmetric standard model with low-mass heavy singlet neutrinos and sneutrinos. We find that the decays µ-->egamma, tau-->egamma and tau-->µgamma are forbidden in the supersymmetric limit of the theory, whereas other processes, such as µ-->eee, µ-->e conversion, tau-->eee and tau-->eµµ, are allowed and can be dramatically enhanced several orders of magnitude above the observable level by potentially large neutrino Yukawa coupling effects. The profound implications of supersymmetric lepton flavor violation for present and future experiments are discussed.

ARTICLES

Measurement of CP violation observables and parameters for the decays B±-->DK*±
B. Aubert et al.
Published 3 November 2009 (14 pages)
092001  Full Text: PDF (570 kB)  | Buy Article
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We study the decay B--->DK*- using a sample of 379×106 Upsilon(4S)-->B[overline B] events collected with the BABAR detector at the PEP-II B factory. We perform a Gronau-London-Wyler analysis where the D meson decays into either a CP-even (CP+) eigenstate (K+K-, pi+pi-), CP-odd (CP-) eigenstate (KS0pi0, KS0phi, KS0omega) or a non-CP state (K-pi+). We also analyze D meson decays into K+pi- from a Cabibbo-favored [overline D]0 decay or doubly suppressed D0 decay [Atwood-Dunietz-Soni (ADS) analysis]. We measure observables that are sensitive to the Cabibbo-Kobayashi-Maskawa angle gamma: the partial-rate charge asymmetries [script A]CP±, the ratios [script R]CP± of the B-decay branching fractions in CP± and non-CP decay, the ratio [script R]ADS of the charge-averaged branching fractions, and the charge asymmetry [script A]ADS of the ADS decays: [script A]CP+=0.09±0.13±0.06, [script A]CP-=-0.23±0.21±0.07, [script R]CP+=2.17±0.35±0.09, [script R]CP-=1.03±0.27±0.13, [script R]ADS=0.066±0.031±0.010, and [script A]ADS=-0.34±0.43±0.16, where the first uncertainty is statistical and the second is systematic. Combining all the measurements and using a frequentist approach yields the magnitude of the ratio between the Cabibbo-suppressed and favored amplitudes, rB=0.31 with a one (two) sigma confidence level interval of [0.24, 0.38] ([0.17, 0.43]). The value rB=0 is excluded at the 3.3 sigma level. A similar analysis excludes values of gamma in the intervals [0, 7]°, [55, 111]°, and [175, 180]° ([85, 99]°) at the one (two) sigma confidence level.

Prospects for the measurement of the unitarity triangle angle gamma from B0-->DK+pi- decays
Tim Gershon and Mike Williams
Published 5 November 2009 (12 pages)
092002  Full Text: PDF (3729 kB)  | Buy Article
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The potential for a precise measurement of the unitarity triangle angle gamma in future experiments from the decay B0-->DK*0 is well known. It has recently been suggested that the sensitivity can be significantly enhanced by analyzing the B0-->DK+pi- Dalitz plot to extract amplitudes relative to those of the flavor-specific decay B0-->D2*-K+. An extension to this method which includes the case where the neutral D meson is reconstructed in suppressed final states is presented. The sensitivity to gamma is estimated using this method and compared to that obtained using the B0-->DK*0 decay alone. Experimental effects, such as background contamination, are also considered. This approach appears to be a highly attractive addition to the family of methods that can be used to determine gamma.

Study of DsJ decays to D*K in inclusive e+e- interactions
B. Aubert et al. (BABAR Collaboration)
Published 9 November 2009 (12 pages)
092003  Full Text: PDF (570 kB)  | Buy Article
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We observe the decays Ds1*(2710)+-->D*K and DsJ*(2860)+-->D*K and measure their branching fractions relative to the DK final state. We also observe, in the D*K mass spectrum, a new broad structure at a mass of (3044±8stat(((+30)/(-5)))syst) MeV/c2 having a width Gamma=(239±35stat(((+46)/(-42)))syst) MeV. To obtain this result we use 470 fb-1 of data recorded by the BABAR detector at the PEP-II asymmetric-energy e+e- storage rings at the Stanford Linear Accelerator Center running at center-of-mass energies near 10.6 GeV.

Proton-air cross section measurement with the ARGO-YBJ cosmic ray experiment
G. Aielli et al. (ARGO-YBJ Collaboration)
Published 16 November 2009 (14 pages)
092004  Full Text: PDF (2212 kB)  | Buy Article
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The proton-air cross section in the energy range 1–100 TeV has been measured by the ARGO-YBJ cosmic ray experiment. The analysis is based on the primary cosmic ray flux attenuation for different atmospheric depths (i.e. zenith angles) and exploits the detector capabilities of selecting the shower development stage by means of hit multiplicity, density and lateral profile measurements at ground. The effects of shower fluctuations, the contribution of heavier primaries and the uncertainties of the hadronic interaction models, have been taken into account. The results have been used to estimate the total proton-proton cross section at center-of-mass energies between 70 and 500 GeV, where no accelerator data are currently available.

Measurements of the tau mass and the mass difference of the tau+ and tau- at BABAR
B. Aubert et al.
Published 20 November 2009 (13 pages)
092005  Full Text: PDF (630 kB)  | Buy Article
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We present the result from a precision measurement of the mass of the tau lepton, Mtau, based on 423 fb-1 of data recorded at the Upsilon(4S) resonance with the BABAR detector. Using a pseudomass endpoint method, we determine the mass to be 1776.68±0.12(stat)±0.41(syst) MeV. We also measure the mass difference between the tau+ and tau-, and obtain (Mtau+-Mtau-)/MAVGtau=(-3.4±1.3(stat)±0.3(syst))×10-4, where MAVGtau is the average value of Mtau+ and Mtau-.

Measurement of the top quark mass in final states with two leptons
V. M. Abazov et al. (D0 Collaboration)
Published 20 November 2009 (20 pages)
092006  Full Text: PDF (546 kB)  | Buy Article
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We present measurements of the top quark mass (mt) in t[overline t] candidate events with two final state leptons using 1 fb-1 of data collected by the D0 experiment. Our data sample is selected by requiring two fully identified leptons or by relaxing one lepton requirement to an isolated track if at least one jet is tagged as a b jet. The top quark mass is extracted after reconstructing the event kinematics under the t[overline t] hypothesis using two methods. In the first method, we integrate over expected neutrino rapidity distributions, and in the second we calculate a weight for the possible top quark masses based on the observed particle momenta and the known parton distribution functions. We analyze 83 candidate events in the data and obtain mt=176.2±4.8(stat)±2.1(sys) GeV and mt=173.2±4.9(stat)±2.0(sys) GeV for the two methods, respectively. Accounting for correlations between the two methods, we combine the measurements to obtain mt=174.7±4.4(stat)±2.0(sys) GeV.

Observation and polarization measurement of B0-->a1(1260)+a1(1260)- decay
B. Aubert et al. (BABAR Collaboration)
Published 20 November 2009 (8 pages)
092007  Full Text: PDF (170 kB)  | Buy Article
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We present measurements of the branching fraction [script B] and longitudinal polarization fraction fL for B0-->a1(1260)+a1(1260)- decays, with a1(1260)±-->pi-pi+pi±. The data sample, collected with the BABAR detector at the SLAC National Accelerator Laboratory, represents 465×106 produced B[overline B] pairs. We measure [script B](B0-->a1(1260)+a1(1260)-)×[[script B](a1(1260)+-->pi-pi+pi+)]2=  (11.8±2.6±1.6)×10-6 and fL=0.31±0.22±0.10, where the first uncertainty is statistical and the second systematic. The decay mode is measured with a significance of 5.0 standard deviations including systematic uncertainties.

C5A axial form factor from bubble chamber experiments
K. M. Graczyk, D. Kielczewska, P. Przewlocki, and J. T. Sobczyk
Published 2 November 2009 (14 pages)
093001  Full Text: PDF (494 kB)  | Buy Article
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A careful reanalysis of both Argonne National Laboratory and Brookhaven National Laboratory data for weak single pion production is done. We consider deuteron nuclear effects and normalization (flux) uncertainties in both experiments. We demonstrate that these two sets of data are in good agreement. For the dipole parametrization of C5A(Q2), we obtain C5A(0)=1.19±0.08, MA=0.94±0.03 GeV. As an application we present the discussion of the uncertainty of the neutral current 1pi0 production cross section, important for the T2K neutrino oscillation experiment.

Fermion masses and mixings in a minimal SO(10)×A4 supersymmetric grand unified theory
Abdelhamid Albaid
Published 12 November 2009 (9 pages)
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A supersymmetric SO(10)×A4 grand unified theory model is constructed for fermion masses and mixing by introducing a minimal set of low dimensional Higgs representations needed to break the gauge symmetry down to SU(3)c×U(1)em. The hierarchy of fermion masses can be understood in the framework of A4 symmetry. From the A4-invariant superpotential, the “double lopsided” mass matrices for the charged leptons and the down quarks are obtained. It is shown that this structure simultaneously leads to bi-large neutrino mixings and small Cabibbo-Kobayashi-Maskawa mixing angles. An excellent fit to the masses and mixings of the quarks and leptons as well as to the CP violation parameter is obtained. Moreover, the model predicts the neutrino mixing angle sintheta13[approximate]0.15.

Neutrino masses and heavy triplet leptons at the LHC: Testability of the type III seesaw mechanism
Tong Li and Xiao-Gang He
Published 13 November 2009 (24 pages)
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We study LHC signatures of the type III seesaw mechanism in which SU(2)L triplet leptons are introduced to supply the heavy seesaw masses. To detect the signals of these heavy triplet leptons, one needs to understand their decays to standard model particles which depend on how light and heavy leptons mix with each other. We concentrate on the usual solutions with small light and heavy lepton mixing of the order of the square root of the ratio of light and heavy masses, (mnu/MnuR)1/2. This class of solutions can lead to a visible displaced vertex detectable at the LHC which can be used to distinguish small mixing and large mixing between light and heavy leptons. We show that, in this case, the couplings of light and heavy triplet leptons to gauge and Higgs bosons, which determine the decay widths and branching ratios, can be expressed in terms of light neutrino masses and their mixing. Using these relations, we study heavy triplet lepton decay patterns and production cross section at the LHC. If these heavy triplet leptons are below a TeV or so, they can be easily produced at the LHC due to their gauge interactions from being nontrivial representations of SU(2)L. We consider two ideal production channels, (1) E+E--->[script-l]+[script-l]+[script-l]-[script-l]-jj ([script-l]=e, µ, tau) and (2) E±N-->[script-l]±[script-l]±jjjj in detail. For case 1, we find that with one or two of the light leptons being tau it can also be effectively studied. With judicious cuts at the LHC, the discovery of the heavy triplet leptons as high as a TeV can be achieved with 100 fb-1 integrated luminosity.

One vanishing minor in the neutrino mass matrix
E. I. Lashin and N. Chamoun
Published 20 November 2009 (17 pages)
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We study a specific texture of the neutrino mass matrix, namely the models with one 2×2 subdeterminant equal to zero. We carry out a complete phenomenological analysis with all possible relevant correlations. Every pattern of the six possible ones is found able to accommodate the experimental data, with three cases allowing also for noninvertible mass matrices. We present symmetry realizations for all the models.

Charm changing weak hadronic decays of triplet (C=1) baryons emitting axial-vector mesons including factorizable and pole contributions
Arvind Sharma and R. C. Verma
Published 4 November 2009 (7 pages)
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We investigate the weak nonleptonic decays of Lambdac+, Xic+, and Xic0 into the octet baryons (JP=1/2+) and axial-vector mesons (JP=1+) employing the factorization scheme for W-emission diagrams and the pole model for W-exchange contributions. Determining the baryon-baryon transition form factors in the nonrelativistic quark model and incorporating the constraints of heavy quark symmetry, we predict their branching ratios and asymmetry parameters.

W+3 jet production at the Tevatron
R. Keith Ellis, Kirill Melnikov, and Giulia Zanderighi
Published 4 November 2009 (8 pages)
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We compute the next-to-leading order QCD corrections to the production of W bosons in association with three jets at the Tevatron in the leading color approximation, which we define by considering the number of colors and the number of light flavors as being of the same order of magnitude. The theoretical uncertainty in the next-to-leading order prediction for the cross section is of the order of 15%–25% which is a significant improvement compared to the leading order result.

Cosmic ray interaction event generator SIBYLL 2.1
Eun-Joo Ahn, Ralph Engel, Thomas K. Gaisser, Paolo Lipari, and Todor Stanev
Published 4 November 2009 (17 pages)
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The cosmic ray interaction event generator Sibyll is widely used in extensive air shower simulations. We describe in detail the properties of Sibyll 2.1 and the differences with the original version 1.7. The major structural improvements are the possibility to have multiple soft interactions, introduction of new parton density functions, and an improved treatment of diffraction. Sibyll 2.1 gives better agreement with fixed target and collider data, especially for the inelastic cross sections and multiplicities of secondary particles. Shortcomings and suggestions for future improvements are also discussed.

Parton distribution function nuclear corrections for charged lepton and neutrino deep inelastic scattering processes
I. Schienbein, J. Y. Yu, K. Kovařík, C. Keppel, J. G. Morfín, F. I. Olness, and J. F. Owens
Published 5 November 2009 (8 pages)
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We perform a chi2 analysis of nuclear parton distribution functions (NPDFs) using neutral current charged-lepton ([script-l]±A) deeply inelastic scattering (DIS), and Drell-Yan data for several nuclear targets. The nuclear A dependence of the NPDFs is extracted in a next-to-leading order fit. We compare the nuclear corrections factors (F2Fe/F2D) for this charged-lepton data with other results from the literature. In particular, we compare and contrast fits based upon the charged-lepton DIS data with those using neutrino-nucleon DIS data.

X(3872) as a molecular DD* state in a potential model
Ian Woo Lee, Amand Faessler, Thomas Gutsche, and Valery E. Lyubovitskij
Published 9 November 2009 (10 pages)
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We discuss the possibility that the X(3872) can be a hadronic DD* bound state in the framework of a potential model. The potential is generated by the exchange of pseudoscalar, scalar, and vector mesons resulting from the Lagrangian of heavy hadron chiral perturbation theory. The hadronic bound state configuration contains charged and neutral DD* components, while orbital S and D waves are included. Isospin symmetry breaking effects are fully taken into account. We show that binding in the DD* system with JPC=1++ already exists for a reasonable value of the meson-exchange regularization parameter of Lambda~1.2 GeV. We also explore the possibility of hadronic BB* bound states and show that binding can be achieved in the isoscalar limit for JPC=1++ or 1+-.

Aspects of meson-baryon scattering in three- and two-flavor chiral perturbation theory
Maxim Mai, Peter C. Bruns, Bastian Kubis, and Ulf-G. Meißner
Published 9 November 2009 (21 pages)
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We analyze meson-baryon scattering lengths in the framework of covariant baryon chiral perturbation theory at leading one-loop order. We compute the complete set of matching relations between the dimension-two low-energy constants in the two- and three-flavor formulations of the theory. We derive new two-flavor low-energy theorems for pion-hyperon scattering that can be tested in lattice simulations.

Light vector meson and heavy baryon strong interaction
Peng-Zhi Huang, Hua-Xing Chen, and Shi-Lin Zhu
Published 11 November 2009 (9 pages)
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We calculate the coupling constants between the light vector mesons and heavy baryons within the framework of the light-cone QCD sum rule in the leading order of heavy quark effective theory. Most resulting sum rules are stable with the variations of the Borel parameter and the continuum threshold. The extracted couplings will be useful in the study of the possible heavy baryon molecular states.

Double charmonium production in exclusive bottomonia decays
V. V. Braguta, A. K. Likhoded, and A. V. Luchinsky
Published 11 November 2009 (13 pages)
094008  Full Text: PDF (228 kB)  | Buy Article
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This paper is devoted to the leading twist exclusive bottomonia decays with double charmonium in the final state. Using models of the twist-2 charmonia distribution amplitudes, the widths of these decays are calculated within light cone formalism. In addition, the processes under consideration are studied within nonrelativistic QCD. In our analysis we have found that the production of some of the P-wave charmonia mesons with Lz[not-equal]0 is allowed already at the leading twist approximation. This means that the selection rules which predict the suppression of such decays are violated. The mechanism which lies behind this violation is discussed.

Shape of pion distribution amplitude
A. V. Radyushkin
Published 13 November 2009 (9 pages)
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A scenario is investigated in which the leading-twist pion distribution amplitude phipi(x) is approximated by the pion decay constant fpi for all essential values of the light-cone fraction x. A model for the light-front wave function Psi(x,k[perpendicular]) is proposed that produces such a distribution amplitude and has a rapidly decreasing (exponential for definiteness) dependence on the light-front energy combination k[perpendicular]2/x(1-x). It is shown that this model easily reproduces the fit of recent large-Q2 BABAR data on the photon-pion transition form factor. Some aspects of the scenario with flat pion distribution amplitude are discussed.

O(alphas2) and O(alphas3) heavy flavor contributions to transversity at Q2>>m2
Johannes Blümlein, Sebastian Klein, and Beat Tödtli
Published 16 November 2009 (12 pages)
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In deep-inelastic processes the heavy flavor Wilson coefficients factorize for Q2>>m2 into the light-flavor Wilson coefficients of the corresponding process and the massive operator matrix elements (OMEs). We calculate the O(alphas2) and O(alphas3) massive OME for the flavor nonsinglet transversity distribution. At O(alphas2) the OME is obtained for general values of the Mellin variable N, while at O(alphas3) the moments N=1 to 13 are computed. The terms [proportional]TF of the 3-loop transversity anomalous dimension are obtained and results in the literature are confirmed. We discuss the relation of these contributions to the Soffer bound for transversity.

Multichannel calculation of excited vector phi resonances and the phi(2170)
Susana Coito, George Rupp, and Eef van Beveren
Published 16 November 2009 (8 pages)
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A multichannel calculation of excited JPC=1--phi states is carried out within a generalization of the resonance-spectrum expansion, which may shed light on the classification of the phi(2170) resonance, discovered by BABAR and originally denoted X(2175). In this framework, a complete spectrum of bare s[overline s] states is coupled to those Okubo-Zweig-Iizuka–allowed decay channels that should be most relevant for the considered energy range. The included S- and P-wave two-meson channels comprise the lowest pseudoscalar, vector, scalar, and axial-vector mesons, while in the q[overline q] sector both the 3S1 and 3D1 states are coupled. The only two free parameters are tuned so as to reproduce mass and width of the phi(1020), but come out reasonably close to previously used values. Among the model's T-matrix poles, there are good candidates for observed resonances, as well as other ones that should exist according to the quark model. Besides the expected resonances as unitarized confinement states, a dynamical resonance pole is found at (2186-i246) MeV. The huge width makes its interpretation as the phi(2170) somewhat dubious, but further improvements of the model may change this conclusion.

Y(4260) as a J/psiK[overline K] system
A. Martínez Torres, K. P. Khemchandani, D. Gamermann, and E. Oset
Published 17 November 2009 (8 pages)
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A study of the J/psipipi and J/psiK[overline K] systems, treating them as coupled channels, has been made by solving the Faddeev equations, with the purpose of investigating the possibility of generation of the JPC=1--, Y(4260) resonance due to the interaction between these three mesons. In order to do this, we start by solving the Bethe-Salpeter equation for the two pseudoscalar and for the vector-pseudocalar meson systems using the amplitudes obtained from the lowest order chiral Lagrangians as potentials. With the t- matrices generated from these potentials, which contain the poles of the sigma, f0(980), and a0(980) resonances for the pseudoscalar-pseudoscalar system and the pole of the X(3872), along with other new charmed resonant states, for the vector-pseudoscalar system, we solve the Faddeev equations. As a result, we get a peak around 4150 MeV with a width ~90 MeV when the invariant mass of the two pseudoscalars is close to that of the f0(980).

Factorization structure of gauge theory amplitudes and application to hard scattering processes at the LHC
Jui-yu Chiu, Andreas Fuhrer, Randall Kelley, and Aneesh V. Manohar
Published 19 November 2009 (43 pages)
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Previous work on electroweak radiative corrections to high-energy scattering using soft-collinear effective theory (SCET) has been extended to include external transverse and longitudinal gauge bosons and Higgs bosons. This allows one to compute radiative corrections to all parton-level hard scattering amplitudes in the standard model to next-to-leading-log order, including QCD and electroweak radiative corrections, mass effects, and Higgs exchange corrections, if the high-scale matching, which is suppressed by two orders in the log counting, and contains no large logs, is known. The factorization structure of the effective theory places strong constraints on the form of gauge theory amplitudes at high energy for massless and massive gauge theories, which are discussed in detail in the paper. The radiative corrections can be written as the sum of process-independent one-particle collinear functions, and a universal soft function. We give plots for the radiative corrections to q[overline q]-->WTWT, ZTZT, WLWL, and ZLH, and gg-->WTWT to illustrate our results. The purely electroweak corrections are large, ranging from 12% at 500 GeV to 37% at 2 TeV for transverse W pair production, and increasing rapidly with energy. The estimated theoretical uncertainty to the partonic (hard) cross section in most cases is below 1%, smaller than uncertainties in the parton distribution functions. We discuss the relation between SCET and other factorization methods, and derive the Magnea-Sterman equations for the Sudakov form factor using SCET, for massless and massive gauge theories, and for light and heavy external particles.

Baryon magnetic moments in large-Nc chiral perturbation theory
Rubén Flores-Mendieta
Published 20 November 2009 (34 pages)
094014  Full Text: PDF (436 kB)  | Buy Article
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The baryon magnetic and transition magnetic moments are computed in heavy baryon chiral perturbation theory in the large-Nc limit, where Nc is the number of colors. One-loop nonanalytic corrections of orders mq1/2 and mqlnmq are incorporated into the analysis, where contributions of both intermediate octet and decuplet baryon states are explicitly included. Expressions are obtained in the limit of vanishing baryon mass differences and compared with the current experimental data. Furthermore, a comparison with conventional heavy baryon chiral perturbation theory is carried out for three light quarks flavors and at the physical value Nc=3.

CP violation in Bq decays and final state strong phases
Fayyazuddin
Published 20 November 2009 (12 pages)
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Using the unitarity, SU(2) and C invariance of hadronic interactions, the bounds on final state phases are derived. It is shown that values obtained for the final state phases relevant for the direct CP asymmetries ACP(B0-->K+pi-,K0pi0) are compatible with experimental values for these asymmetries. For the decays B0-->D(*)-pi+(D(*)+pi-) described by two independent single amplitudes Af and A[overline f][prime] with different weak phases (0 and gamma) it is argued that the C invariance of hadronic interactions implies the equality of the final state phase deltaf and delta[overline f][prime]. This in turn implies that the CP asymmetry ((S[sub +] + S[sub -])/2) is determined by weak phase (2beta+gamma) only, whereas ((S[sub +]-S[sub -])/2)=0. Assuming factorization for tree graphs, it is shown that the B-->D(*) form factors are in excellent agreement with the heavy quark effective theory. From the experimental value for (((S[sub +] + S[sub -])/2))D*pi, the bound sin(2beta+gamma)>=0.69 is obtained and (((S[sub +] + S[sub -])/2))DS*-K+[approximate]-(0.41±0.08)singamma is predicted. For the decays described by the amplitudes Af[not-equal]A[overline f] such as B0-->rho+pi-: A[overline f] and B0-->rho-pi+: Af where these amplitudes are given by tree and penguin diagrams with different weak phases, it is shown that in the limit deltaf,[overline f]T-->0, rf,[overline f]cosdeltaf,[overline f]=cosalpha and (S[sub [overline f]]/S[sub f])=((S + Delta S)/(S-Delta S))=  -((sqrt(1-C[sub [overline f]][sup 2]))/(sqrt(1-C[sub f][sup 2]))).

Gribov's horizon and the ghost dressing function
Ph. Boucaud, J. P. Leroy, A. Le Yaouanc, J. Micheli, O. Pène, and J. Rodríguez-Quintero
Published 9 November 2009 (9 pages)
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We study a relation recently derived by K. Kondo at zero momentum between the Zwanziger's horizon function, the ghost dressing function and Kugo's functions u and w. We agree with this result as far as bare quantities are considered. However, assuming the validity of the horizon gap equation, we argue that the solution w(0)=0 is not acceptable since it would lead to a vanishing renormalized ghost dressing function. On the contrary, when the cutoff goes to infinity, u(0)-->[infinity], w(0)-->-[infinity] such that u(0)+w(0)-->-1. Furthermore w and u are not multiplicatively renormalizable. Relaxing the gap equation allows w(0)=0 with u(0)-->-1. In both cases the bare ghost dressing function, F(0,Lambda), goes logarithmically to infinity at infinite cutoff. We show that, although the lattice results provide bare results not so different from the F(0,Lambda)=3 solution, this is an accident due to the fact that the lattice cutoffs lie in the range 1–3 GeV-1. We show that the renormalized ghost dressing function should be finite and nonzero at zero momentum and can be reliably estimated on the lattice up to powers of the lattice spacing; from published data on a 804 lattice at beta=5.7 we obtain FR(0,µ=1.5 GeV)~=2.2.

Phase structure of thermal lattice QCD with Nf=2 twisted mass Wilson fermions
E.-M. Ilgenfritz, K. Jansen, M. P. Lombardo, M. Müller-Preussker, M. Petschlies, O. Philipsen, and L. Zeidlewicz
Published 9 November 2009 (13 pages)
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We present numerical results for the phase diagram of lattice QCD at finite temperature in the formulation with twisted mass Wilson fermions and a tree-level Symanzik-improved gauge action. Our simulations are performed on lattices with temporal extent Ntau=8, and lattice coupling beta ranging from strong coupling to the scaling domain. Covering a wide range in the space spanned by the lattice coupling beta and the hopping and twisted mass parameters kappa and µ, respectively, we obtain a comprehensive picture of the rich phase structure of the lattice theory. In particular, we verify the existence of an Aoki phase in the strong coupling region and the realization of the Sharpe-Singleton scenario at intermediate couplings. In the weak coupling region we identify the phase boundary for the physical finite temperature phase transition/crossover. Its shape in the three-dimensional parameter space is consistent with Creutz's conjecture of a cone-shaped thermal transition surface.

Nucleon strangeness form factors from Nf=2+1 clover fermion lattice QCD
Takumi Doi et al. (chiQCD Collaboration)
Published 10 November 2009 (6 pages)
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We present the Nf=2+1 clover fermion lattice QCD calculation of the nucleon strangeness form factors. We evaluate disconnected insertions using the Z(4) stochastic method, along with unbiased subtractions from the hopping parameter expansion. We find that increasing the number of nucleon sources for each configuration improves the signal significantly. We obtain GMs(0)=-0.017(25)(07), where the first error is statistical, and the second is the uncertainties in Q2 and chiral extrapolations. This is consistent with experimental values, and has an order of magnitude smaller error.

Evolution of the coupling constant in SU(2) lattice gauge theory with two adjoint fermions
Ari J. Hietanen, Kari Rummukainen, and Kimmo Tuominen
Published 11 November 2009 (7 pages)
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We measure the evolution of the coupling constant using the Schrödinger functional method in the lattice formulation of SU(2) gauge theory with two massless Dirac fermions in the adjoint representation. We observe strong evidence for an infrared fixed point, where the theory becomes conformal. We measure the beta function and the coupling constant as a function of the energy scale.

Limits of custodial symmetry
R. Sekhar Chivukula, Stefano Di Chiara, Roshan Foadi, and Elizabeth H. Simmons
Published 2 November 2009 (12 pages)
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We introduce a toy model implementing the proposal of using a custodial symmetry to protect the ZbL[overline b]L coupling from large corrections. This “doublet-extended standard model” adds a weak doublet of fermions (including a heavy partner of the top quark) to the particle content of the standard model in order to implement an O(4)×U(1)X~SU(2)L×SU(2)R×PLR×U(1)X symmetry in the top-quark mass generating sector. This symmetry is softly broken to the gauged SU(2)L×U(1)Y electroweak symmetry by a Dirac mass M for the new doublet; adjusting the value of M allows us to explore the range of possibilities between the O(4)-symmetric (M-->0) and standard-model-like (M-->[infinity]) limits. In this simple model, we find that the experimental limits on the ZbL[overline b]L coupling favor smaller M while the presence of a potentially sizable negative contribution to alphaT strongly favors large M. Comparison with precision electroweak data shows that the heavy partner of the top quark must be heavier than about 3.4 TeV, making it difficult to search for at LHC. This result demonstrates that electroweak data strongly limit the amount by which the custodial symmetry of the top-quark mass generating sector can be enhanced relative to the standard model. Using an effective field theory calculation, we illustrate how the leading contributions to alphaT, alphaS, and the ZbL[overline b]L coupling in this model arise from an effective operator coupling right-handed top quarks to the Z boson, and how the effects on these observables are correlated. We contrast this toy model with extradimensional models in which the extended custodial symmetry is invoked to control the size of additional contributions to alphaT and the ZbL[overline b]L coupling, while leaving the standard model contributions essentially unchanged.

Secluded U(1) below the weak scale
Maxim Pospelov
Published 2 November 2009 (8 pages)
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A secluded U(1) sector with weak admixture to photons, O(10-2-10-3), and the scale of the breaking below 1 GeV represents a natural yet poorly constrained extension of the standard model. We analyze g-2 of muons and electrons together with other precision QED data, as well as radiative decays of strange particles to constrain the mass-mixing angle (mV-kappa) parameter space. We point out that mV~=214 MeV and kappa2>3×10-5 can be consistent with the hypothesis of the HyperCP Collaboration, which seeks to explain the anomalous energy distribution of muon pairs in the Sigma+-->pµ+µ- process by a resonance, without direct contradiction to the existing data on radiative kaon decays. The same parameters lead to an O(few×10-9) upward correction to the anomalous magnetic moment of the muon, possibly relaxing some tension between the experimental value and theoretical determinations of g-2. The ultrafine energy resolution scan of the e+e--->µ+µ- cross section and dedicated analysis of lepton spectra from K+-->pi+e+e- decays should be able to provide a conclusive test of this hypothesis and improve the constraints on the model.

Dark matter in minimal supergravity with type-II seesaw mechanism
J. N. Esteves, S. Kaneko, J. C. Romao, M. Hirsch, and W. Porod
Published 2 November 2009 (12 pages)
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We calculate the relic density of the lightest neutralino in a supersymmetric seesaw type-II (“triplet seesaw”) model with minimal supergravity boundary conditions at the grand unified theory (GUT) scale. The presence of a triplet below the GUT scale, required to explain measured neutrino data in this setup, leads to a characteristic deformation of the sparticle spectrum with respect to the pure minimal supergravity (mSUGRA) expectations, affecting the calculated relic dark matter (DM) density. We discuss how the DM allowed regions in the (m0,M1/2) plane change as a function of the (type-II) seesaw scale. We also compare the constraints imposed on the models parameter space form upper limits on lepton flavor violating decays to those imposed by DM. Finally, we briefly comment on uncertainties in the calculation of the relic neutralino density due to uncertainties in the measured top and bottom masses.

Soft gluon resummation for the production of gluino-gluino and squark-antisquark pairs at the LHC
A. Kulesza and L. Motyka
Published 5 November 2009 (23 pages)
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We study the effect of soft gluon emission in the hadroproduction of gluino-gluino and squark-antisquark pairs at the next-to-leading logarithmic accuracy within the framework of the minimal supersymmetric model. We present the calculation of the one-loop soft anomalous dimension matrices controlling the color evolution of the underlying hard-scattering processes. The numerical results for resummed cross sections for proton-proton collisions at the Large Hadron Collider are discussed in detail.

Correlation between direct dark matter detection and Br(Bs-->µµ) with a large phase of Bs-[overline B]s mixing
Bhaskar Dutta, Yukihiro Mimura, and Yudi Santoso
Published 5 November 2009 (10 pages)
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We combine the analyses for flavor changing neutral current processes and dark matter solutions in minimal-type supersymmetric grand unified theory models, SO(10) and SU(5), with a large Bs-[overline B]s mixing phase and large tanbeta. For large tanbeta, the double-penguin diagram dominates the supersymmetry contribution to the Bs-[overline B]s mixing amplitude. Also, the Br(Bs-->µµ) constraint becomes important as it grows as tan6beta, although it can still be suppressed by a large pseudoscalar Higgs mass mA. We investigate the correlation between Bs-->µµ and the dark matter direct detection cross section through their dependence on mA. In the minimal-type of SU(5) with type I seesaw, the large mixing in neutrino Dirac couplings results in a large lepton flavor violating decay process tau-->µgamma, which in turn sets the upper bound on mA. In the SO(10) case, the large mixing can be chosen to be in the Majorana couplings instead, and the constraint from Br(tau-->µgamma) can be avoided. The heavy Higgs funnel region turns out to be an interesting possibility in both cases and the direct dark matter detection should be possible in the near future in these scenarios.

Protecting unparticles from the MSSM Higgs sector
Ann E. Nelson, Maurizio Piai, and Christopher Spitzer
Published 5 November 2009 (11 pages)
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We construct a model of an unparticle sector consisting of a supersymmetric SU(N) gauge theory with the number of flavors in the Seiberg conformal window. We couple this sector to the minimal supersymmetric standard model via heavy messengers. The resulting low energy theory has a Higgs coupling to unparticles. The Higgs vev drives the hidden Seiberg sector to a new conformal fixed point. The coupling to the Higgs mediates supersymmetry breaking to the Seiberg sector, and breaks conformal invariance at a lower scale. The low energy theory contains light stable and metastable mesons. Higgs decay into this sector gives signatures which are similar to those of “hidden valley” models. Decays of the lightest superpartner of standard model particles into the hidden sector reveal potentially observable unparticle kinematics.

Rapidity gap events in squark pair production at the LHC
Sascha Bornhauser, Manuel Drees, Herbert K. Dreiner, and Jong Soo Kim
Published 6 November 2009 (14 pages)
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The exchange of electroweak gauginos in the t or u channel allows squark pair production at hadron colliders without color exchange between the squarks. This can give rise to events where little or no energy is deposited in the detector between the squark decay products. We discuss the potential for detection of such rapidity-gap events at the Large Hadron Collider. Our numerical analysis is divided into two parts. First, we evaluate in a simplified framework the rapidity-gap signal at the parton level. The second part covers an analysis with full event simulation using PYTHIA as well as Herwig++, but without detector simulation. We analyze the transverse energy deposited between the jets from squark decay, as well as the probability of finding a third jet in between the two hardest jets. For the minimal supergravity benchmark point SPS1a we find statistically significant evidence for a color-singlet exchange contribution. The systematical differences between current versions of PYTHIA and HERWIG++ are larger than the physical effect from color-singlet exchange; however, these systematic differences could be reduced by tuning both Monte Carlo generators on normal QCD dijet data.

Dirac neutrinos from a second Higgs doublet
Shainen M. Davidson and Heather E. Logan
Published 9 November 2009 (7 pages)
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We propose a minimal extension of the standard model in which neutrinos are Dirac particles and their tiny masses are explained without requiring tiny Yukawa couplings. A second Higgs doublet with a tiny vacuum expectation value provides neutrino masses while simultaneously improving the naturalness of the model by allowing a heavier standard-model-like Higgs boson consistent with electroweak precision data. The model predicts a µ-->egamma rate potentially detectable in the current round of experiments, as well as distinctive signatures in the production and decay of the charged Higgs H+ of the second doublet which can be tested at future colliders. Neutrinoless double beta decay is absent.

Anomalous resonant production of the fourth-family up-type quarks at the LHC
I. T. Çakir, H. Duran Yildiz, O. Çakir, and G. Ünel
Published 9 November 2009 (12 pages)
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Considering the present limits on their masses from the Tevatron experiments, the fourth-family quarks are expected to have masses larger than the top quark. Because of their expected large masses, they could have different dynamics than the third-family quarks of the standard model. The resonant production of the fourth-family up-type quark t[prime] has been studied via the anomalous production subprocess gqi-->t[prime] (where qi=u, c) at the LHC, with center-of-mass energies of 10 TeV and 14 TeV. The signatures of such a process are discussed within the standard model decay modes. The sensitivity to the anomalous coupling kappa/Lambda=0.1 TeV-1 can be reached at sqrt(s)=10 TeV and Lint=100 pb-1.

Like-sign dilepton signals in Higgsless models at the LHC
Tao Han, Hai-shan Liu, Ming-xing Luo, Kai Wang, and Wei Wu
Published 9 November 2009 (6 pages)
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We study the potential LHC discovery of the Z1 Kaluza-Klein gauge boson unitarizing WL+WL- scattering amplitude. In particular, we explore the decay mode Z1-->t[overline t], along with Z1-->W+W-, without specifying the branching fractions. We propose to exploit the associated production pp-->WZ1 and select the final state of like-sign dileptons plus multijets and large missing energy. We conclude that it is possible to observe the Z1 resonance at a 5sigma level with an integrated luminosity of 100 fb-1 at the LHC up to 650 GeV for a dominant WW channel, and 560 GeV for a dominant t[overline t] channel.

Vacuum stability with tachyonic boundary Higgs masses in no-scale supersymmetry or gaugino mediation
Jason L. Evans, David E. Morrissey, and James D. Wells
Published 10 November 2009 (9 pages)
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No-scale supersymmetry or gaugino mediation augmented with large negative Higgs soft masses at the input scale provides a simple solution to the supersymmetric flavor problem while giving rise to a neutralino lightest superpartner particle. However, to obtain a neutralino lightest superpartner particle it is often necessary to have tachyonic input Higgs soft masses that can give rise to charge-and-color-breaking minima and unbounded-from-below directions in the low-energy theory. We investigate the vacuum structure in these theories to determine when such problematic features are present. When the standard electroweak vacuum is only metastable, we compute its lifetime under vacuum tunneling. We find that vacuum metastability leads to severe restrictions on the parameter space for larger tanbeta~30, while for smaller tanbeta~10, only minor restrictions are found. Along the way, we derive an exact bounce solution for tunneling through an inverted parabolic potential.

CP violation in three-body chargino decays
Makiko Nagashima, Ken Kiers, Alejandro Szynkman, David London, Jenna Hanchey, and Kevin Little
Published 10 November 2009 (10 pages)
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CP violation in supersymmetry can give rise to rate asymmetries in the decays of supersymmetric particles. In this work we compute the rate asymmetries for the three-body chargino decays chi-tilde2[plus-minus]-->chi-tilde1[plus-minus]HH, chi-tilde2[plus-minus]-->chi-tilde1[plus-minus]ZZ, chi-tilde2[plus-minus]-->chi-tilde1[plus-minus]W+W- and chi-tilde2[plus-minus]-->chi-tilde1[plus-minus]ZH. Each of the decays contains contributions mediated by neutral Higgs bosons that can possibly go on shell. Such contributions receive a resonant enhancement; furthermore, the strong phases required for the CP asymmetries come from the widths of the exchanged Higgs bosons. Our results indicate that the rate asymmetries can be relatively large in some cases, while still respecting a number of important low-energy bounds such as those coming from B meson observables and electric dipole moments. For the parameters that we consider, rate asymmetries of order 10% are possible in some cases.

Bayesian analysis of the constrained next-to-minimal supersymmetric standard model
Daniel E. López-Fogliani, Leszek Roszkowski, Roberto Ruiz de Austri, and Tom A. Varley
Published 12 November 2009 (16 pages)
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We perform a first global exploration of the constrained next-to-minimal supersymmetric standard model using Bayesian statistics. We derive several global features of the model and find that, in some contrast to initial expectations, they closely resemble those of the constrained minimal supersymmetric standard model. This remains true even away from the decoupling limit which is nevertheless strongly preferred. We present ensuing implications for several key observables, including collider signatures and predictions for direct detection of dark matter.

Flavor effects on the electric dipole moments in supersymmetric theories: A beyond leading order analysis
Junji Hisano, Minoru Nagai, and Paride Paradisi
Published 12 November 2009 (31 pages)
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The standard model predictions for the hadronic and leptonic electric dipole moments (EDMs) are considerably far from the present experimental resolutions; thus, the EDMs represent very clean probes of new physics effects. Especially, within supersymmetric frameworks with flavor-violating soft terms, large and potentially visible effects to the EDMs are typically expected. In this work, we systematically evaluate the predictions for the EDMs at the beyond leading order. In fact, we show that beyond-leading-order contributions to the EDMs dominate over the leading-order effects in large regions of the supersymmetric parameter space. Hence, their inclusion in the evaluation of the EDMs is unavoidable. As an example, we show the relevance of beyond-leading-order effects to the EDMs for a supersymmetric SU(5) model with right-handed neutrinos.

Heavy right-handed neutrinos and dark matter in the nuCMSSM
Kenji Kadota and Keith A. Olive
Published 13 November 2009 (10 pages)
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We perform a systematic study of the effects of the type-I seesaw mechanism on the dark matter abundance in the constrained minimal supersymmetric standard model (CMSSM) which includes three right-handed neutrinos (the nuCMSSM). For large values of m0, m1/2, we exploit the effects of large neutrino Yukawa couplings on the renormalization group evolution of the up-type Higgs. In particular, we show that the focus point scale can greatly exceed the electroweak scale resulting in the absence of a focus point region for which the relic density of neutralinos is within the range determined by WMAP. We also discuss the effects of the right-handed neutrinos on the so-called funnel region, where the relic density is controlled by s-channel annihilations through a heavy Higgs. For small values of m0, m1/2, we discuss the possibility of sneutrino coannihilation regions with an emphasis on the suppression of the left-handed slepton doublet masses due to the neutrino Yukawa coupling. We consider two types of toy models consistent with either the normal or inverted hierarchy of neutrino masses.

Coannihilation scenarios and particle spectroscopy in SU(4)c×SU(2)L×SU(2)R
Ilia Gogoladze, Rizwan Khalid, and Qaisar Shafi
Published 13 November 2009 (7 pages)
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We identify a variety of coannihilation scenarios in a supersymmetric SU(4)c×SU(2)L×SU(2)R model with discrete left-right symmetry. Nonuniversal gaugino masses, compatible with the gauge symmetry, play an essential role in realizing gluino and bino-wino coannihilation regions that are consistent with the WMAP dark matter constraints. We also explore regions of the parameter space in which the little hierarchy problem is partially resolved. We present several phenomenologically interesting benchmark points and the associated sparticle and Higgs mass spectra.

Light Higgs boson scenario in the supersymmetric seesaw model
Masaki Asano, Takayuki Kubo, Shigeki Matsumoto, and Masato Senami
Published 16 November 2009 (8 pages)
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It is demonstrated that the light Higgs boson scenario, in which the lightest Higgs mass is less than the LEP bound, mh>114.4 GeV, is consistent with the supersymmetric seesaw model. With the assumptions of the universal right-handed neutrino mass and the hierarchical mass spectrum of the ordinary neutrinos, the bounds for the right-handed neutrino mass are investigated in terms of lepton flavor violating charged lepton decays. We also discuss the effect of the modification of renormalization group equations by the right-handed neutrinos on the b-->sgamma process and the relic abundance of dark matter in the light Higgs boson scenario.

General features of supersymmetric signals at the ILC: Solving the CERN LHC inverse problem
C. F. Berger, J. S. Gainer, J. L. Hewett, B. Lillie, and T. G. Rizzo
Published 16 November 2009 (77 pages)
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We present the first detailed, large-scale study of the minimal supersymmetric standard model (MSSM) at the sqrt(s)=500 GeV International Linear Collider (ILC), including full standard model backgrounds and detector simulation. This is the first realistic study of the capabilities of the ILC examining the physics of many distinct points in MSSM parameter space which are not linked to a particular supersymmetry (SUSY) breaking mechanism. Specifically, we investigate 242 points in the MSSM parameter space, which we term models, that correspond to the 162 pairs of models that were found by Arkani-Hamed et al. to give indistinguishable signatures at the LHC. We first determine whether the production of the various SUSY particles is visible above the standard model background for each of these parameter space points, and then make a detailed comparison of their various signatures. Assuming an integrated luminosity of 500 fb-1 with 80% electron beam polarization, we find that only 82 out of 242 models lead to visible signatures of some kind with a significance >=5 and that only 57 (63) out of the 162 model pairs are distinguishable at 5 (3)sigma. Our analysis includes PYTHIA and CompHEP SUSY signal generation, full matrix element SM backgrounds for all 2-->2, 2-->4 and 2-->6 processes, ILC-specific initial state radiation and beamstrahlung generated via WHIZARD/GuineaPig, and employs the fast SiD detector simulation org.lcsim. If SUSY is light, the ILC will do a good job at examining its details.

Investigating light neutralinos at neutrino telescopes
V. Niro, A. Bottino, N. Fornengo, and S. Scopel
Published 16 November 2009 (13 pages)
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We present a detailed analysis of the neutrino-induced muon signals coming from neutralino pair annihilations inside the Sun and the Earth with particular emphasis for light neutralinos. The theoretical model considered is an effective minimal supersymmetric extension of the standard model without gaugino-mass unification, which allows neutralinos of light masses (below 50 GeV). The muon events are divided into through-going and stopping muons, using the geometry of the Super-Kamiokande detector. In the evaluation of the signals, we take into account the relevant hadronic and astrophysics uncertainties and include neutrino oscillation and propagation properties in a consistent way. We derive the ranges of neutralino masses which could be explored at neutrino telescopes with a low muon-energy threshold (around 1 GeV) depending on the category of events and on the values of the various astrophysics and particle-physics parameters. A final analysis is focused on the upward muon fluxes which could be generated by those neutralino configurations which are able to explain the annual modulation data of the DAMA/LIBRA experiment. We show how combining these data with measurements at neutrino telescopes could help in pinning down the features of the dark matter particle and in restraining the ranges of the many quantities (of astrophysics and particle-physics origins) which enter in the evaluations and still suffer from large uncertainties.

Hyperquarks and bosonic preon bound states
Michael L. Schmid and Alfons J. Buchmann
Published 16 November 2009 (17 pages)
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In a model in which leptons, quarks, and the recently introduced hyperquarks are built up from two fundamental spin-(1/2) preons, the standard model weak gauge bosons emerge as preon bound states. In addition, the model predicts a host of new composite gauge bosons, in particular, those responsible for hyperquark and proton decay. Their presence entails a left-right symmetric extension of the standard model weak interactions and a scheme for a partial and grand unification of nongravitational interactions based on, respectively, the effective gauge groups SU(6)P and SU(9)G. This leads to a prediction of the Weinberg angle at low energies in good agreement with experiment. Furthermore, using evolution equations for the effective coupling strengths, we calculate the partial and grand unification scales, the hyperquark mass scale, as well as the mass and decay rate of the lightest hyperhadron.

Positivity issues for the pinch-technique gluon propagator and their resolution
John M. Cornwall
Published 4 November 2009 (10 pages)
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Although gauge-boson propagators in asymptotically-free gauge theories satisfy a dispersion relation, they do not satisfy the Källen-Lehmann (KL) representation because the spectral function changes sign. We argue that this is a simple consequence of asymptotic freedom. On the basis of the QED-like Ward identities of the pinch technique (PT) we claim that the product of the coupling g2 and the scalar part d^(q2) of the PT propagator, which is both gauge invariant and renormalization-group invariant, can be factored into the product of the running charge [overline g]2(q2) and a term H^(q2) both of which satisfy the KL representation although their product does not. We show that this behavior is consistent with some simple analytic models that mimic the gauge-invariant PT Schwinger-Dyson equations (SDE), provided that the dynamic gauge-boson mass is sufficiently large. The PT SDEs do not depend directly on the PT propagator through d^ but only through H^.

Nf3g6 term in the pressure of hot QCD
A. Gynther, A. Kurkela, and A. Vuorinen
Published 5 November 2009 (9 pages)
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We determine the first independent part of the g6 coefficient in the weak coupling expansion of the QCD pressure at high temperatures, the one proportional to the maximal power of the number of quark flavors Nf. In addition to introducing and developing computational methods that can be used in evaluating other parts of the expansion, our calculation provides a result that becomes dominant in the limit of large Nf and a fixed effective coupling geff2[equivalent]g2Nf/2.

Pseudoscalar-meson decuplet-baryon coupling constants in light cone QCD
T. M. Aliev, K. Azizi, A. Özpineci, and M. Savci
Published 12 November 2009 (10 pages)
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Taking into account the SU(3)f breaking effects, the strong coupling constants of the pi, K, and eta mesons with decuplet baryons are calculated within the light cone QCD sum rules method. It is shown that all coupling constants, even in the case of SU(3)f breaking, are described in terms of only one universal function. It is shown that for Xi*0-->Xi*0eta, transition violation of SU(3)f symmetry is very large and for other channels when SU(3)f symmetry is violated, its maximum value constitutes 10%÷15%.

Violation of CP and T in semileptonic decays due to scalar interactions
G. López Castro, L. López-Lozano, and A. Rosado
Published 17 November 2009 (5 pages)
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Observing charge-parity (CP) or time-reversal (T) violations in the leptonic sector will give useful information to elucidate the nature of neutrinos. CP-violating couplings in charged leptonic currents carry out the weak phases necessary to break these symmetries. Here we study the interference of W± and H± boson mediated amplitudes as the origin of possible CP and T violation in semileptonic decays of K± mesons and tau± leptons. We use the experimental bound on the T-odd transverse polarization asymmetry in Kmu 3+ decays to predict an upper limit on the CP violating effects in tau-->Kpinu decays. In the framework of this model with scalar-mediated interactions, we find that current limits on the former process indicate that the CP violating effects in the latter are much smaller than the limits reported so far.

S4 as a natural flavor symmetry for lepton mixing
Federica Bazzocchi and Stefano Morisi
Published 19 November 2009 (10 pages)
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Group theoretical arguments seem to indicate the discrete symmetry S4 as the minimal flavor symmetry compatible with tribimaximal neutrino mixing. We prove in a model-independent way that indeed S4 can realize exact tribimaximal mixing through different symmetry breaking patterns. We present two models in which lepton tribimaximal mixing is realized in different ways and for each one we discuss the superpotential that leads to the correct breaking of the flavor symmetry.

On a CP anisotropy measurement in the Dalitz plot
I. Bediaga, I. I. Bigi, A. Gomes, G. Guerrer, J. Miranda, and A. C. dos Reis
Published 20 November 2009 (13 pages)
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Show Abstract
We describe a novel use of the Dalitz plot to probe CP symmetry in three-body modes of B and D mesons. It is based on an observable inspired by astronomers' practice, namely the significance in the difference between corresponding Dalitz plot bins. It provides a model-independent mapping of local CP asymmetries. We illustrate the method for probing CP symmetry in the two complementary cases of B and D decays: in the former sizable or even large effects can be expected, yet have to be differentiated against leading standard model contributions, while in the latter one cannot count on sizable effects, yet has to deal with much less standard model background.