HADRON SPECTROSCOPY: Tenth International Conference on Hadron Spectroscopy
717(2004); http://dx.doi.org/10.1063/1.1799672View Description Hide Description
The investigation of the spectrum of mesons from light to heavy is still a very active field. Lattice gauge theory and many effective models provide a lot of insights into the believed structure of the spectrum of mesons. A lot of them have been found but many others remain to be seen. Although many states fit into the proposed scheme, but most mass predictions lack precision and estimates of the widths are usually missing. Some of them are key stone particles since they are exotic in the sense, that their quantum numbers show that they do not contain conventional qq̄‐pairs or qqq‐baryons. This report compares experimental approaches to find and investigate conventional and exotic mesons. It will be discussed how different experimental techniques can contribute to the puzzle and what else is needed to improve on the current situation.
717(2004); http://dx.doi.org/10.1063/1.1799673View Description Hide Description
Studies of meson production in nucleon‐nucleon collisions at threshold are characterised by few degrees of freedom in a configuration of well defined initial and final states with a transition governed by short range dynamics. Effects from low‐energy scattering in the exit channel are inherent to the data and probe the interaction in baryon‐meson and meson‐meson systems otherwise difficult to access.
From dedicated experiments at the present generation of cooler rings precise data are becoming available on differential and eventually spin observables allowing detailed comparisons between complementary final states. To discuss physics implications of generic and specific properties, recent experimental results on meson production in proton‐proton scattering obtained at CELSIUS and COSY serve as a guideline.
717(2004); http://dx.doi.org/10.1063/1.1799674View Description Hide Description
The KLOE experiment at the Frascati φ factory, DaΦne, has collected ∼500 pb −1, i.e. 1.5 × 109 φ decays. At the φ factory it is possible to select pure K L and K S beams. Although the integrated luminosity is insufficient for precision tests of the CP, T symmetries in kaon decays, a wide number of topics in kaon and hadronic physics are accessible from the largest sample of Φ decays at rest collected so far. The cross section σ(e+e− → π+π−γ) below 1 GeV, relevant for the precise evaluation of the muon magnetic moment, has been measured with a statistical accuracy better than 1%. For the K S , we obtained the ratio of the branching fractions Γ(KS → π+π−(γ))/Γ(KS → π0π0) = (2.239 ± 0.003 stat ± 0.015 syst ), fully inclusive of the ππγ final state. The analysis of the ∼20,000 K S semileptonic decays K S → πeν is being finalized providing precise measurements of both, the K S semileptonic branching ratio, and Re x +, i.e. the ΔS = ΔQ rule violation parameter. For the KL , we obtained the ratio Γ(KL → γγ)/Γ(KL → π0π0π0) = (2.80 ± 0.02 stat ± 0.02 syst ) × 10−3, of interest to Chiral Perturbation Theory (ChPT), as well as preliminary results on the branching ratios to other decay modes. In particular, our measurements of the semileptonic decays of both, neutral, and charged kaons will improve the precision of the CKM matrix element |Vus |, clarifying the present disagreement between different experiments. The φ radiative decays, both in scalar and pseudo‐scalar mesons, have been analyzed giving new measurements of the η − η′ mixing angle, and of the φ → a 0(980)γ, φ → f 0(980)γ branching ratios.
Contradictions about Fine Structures in Meson Spectra and Proposed High‐Resolution Hadron Spectrometer Using “Interactive” Solid‐State Hydrogen Target717(2004); http://dx.doi.org/10.1063/1.1799675View Description Hide Description
High resolution has been discouraged in meson spectrometry for 4 decades by the Doctrine of Experiments Incompatible with Theory (DEIT). DEIT a priori rejects narrow hadron resonances on the paradigm that only broad hadron peaks, Γ⩾ 100 MeV, can exist — in spite of the accumulated evidence to the contrary. The facts are: Mesons 2 orders of magnitude narrower than ‘allowed’ for hadrons, have been confirmed; a new one was announced at this conference. Narrow meson structures have been repeatedly reported at high momentum transfer, |t| >0.2, while they are absent at the low transfer, |t| ∼0.01, where 99% of the experiments are performed. Modification of meson mass and width as a function of the density of nuclear matter in which they are produced, have been recently reported.
We postulate for meson spectra: (1) Intrinsic (‘true’) width, Γ, is different from the observable (‘apparent’) width, Γ’: Γ< Γ’ (2) Γ of all meson states are narrow and can be observed only at or near the maximum |t| reachable in the reaction, and (3) Γ of all meson resonances are subject to broadening as |t| decreases. Since both Γ’ and the production σ are inversely proportional to |t|, most of the observed spectra are produced at the lowest |t| <0.01 and thus the peaks appear broad. We have conceptually designed a novel type hadron spectrometer with an order of magnitude better resolution (0.1 MeV). It would operate at 2 orders of magnitude higher |t| (0.3< |t| <1 (GeV/c)2, than most experiments to date (|t| <0.01). Mesons in the mass region 0.5 <Mx<5 GeV would be produced in πP→PX (baryons in PP→PP*) in a ‘solid state hydrogen target’ consisting of an array of plastic scintillator fibers, CH; collisions with C are electronically rejected. Missing mass of P is measured in the region of the maximum recoil angle.
Story of the suppression by DEIT for 17 years of the observation of a theoretically unexplained narrow peak, which turned out to be ω→2π, and the related correspondence between Werner Heisenberg and this author, is narrated.
717(2004); http://dx.doi.org/10.1063/1.1799676View Description Hide Description
An analysis of the processes with initial state radiation (ISR) has been performed using 90 fb −1 of BABAR data. The selection of μ+μ− and multi‐hadron final states has been demonstrated accompanied with the detected ISR photon. The invariant mass of hadronic final state determines the virtual photon energy and data can be compared with direct e+e− cross sections. The present BABAR data are already competitive with e+e− machine data in 0.28–3.0 GeV energy range and demonstrate many interesting details usefull for low energy hadron spectroscopy.
In addition to light meson spectroscopy these data can be used for calculation of R — the ratio of e+e− → hadrons cross section to e+e− → μ+μ− — and thereby to impact the (g − 2)μ measurement.
The ISR technic gives an access to J/ψ production. The J/ψ decays to μμ, 4π, 2K2π and 4K have been selected and new preliminary measurements of branching ratios performed with comparable or typically better accuracy than PDG.
Measurement of the e+e− → π+π−π+π−, K+K− π+π−, K+K−K+K− Cross Sections Using Initial State Radiation at BABAR717(2004); http://dx.doi.org/10.1063/1.1799677View Description Hide Description
First results of a study of the e+e− → π+π−π+π−γ process with hard photon emitted from initial state are presented. About 60000 fully reconstructed events have been selected based on 89.3 fb −1 of BABAR data. The invariant mass of the hadronic final state defines the effective collision c.m. energy, and so BABAR ISR data can be compared to the relevant direct e+e− measurements. From obtained 4π mass spectrum we evaluate e+e− → π+π−π+π− cross section for the range of c.m.s. energy from 0.6 to 4.5 GeV. The systematic error of the cross section measurement is 5% and comparable with the best e+e− data. The cross sections for identified 2K2π and 4K final states also have been presented.
717(2004); http://dx.doi.org/10.1063/1.1799678View Description Hide Description
The review of the SND results of the e+e− → π+π−π0 process study in the energy range at VEPP‐2M collider, based on about 2 × 106 selected events, is presented. The total cross section, parameters of the ρ, ω, φ, resonances, and ω′, ω″ states were obtained. It was found that ρπ and ωπ0 intermediate states describe the reaction dynamics. The experimental data cannot be described by a sum of only ω, φ, ω′ and ω″ resonances contributions. This can be interpreted as a manifestation of the ρ → 3π decay, suppressed by G‐parity, with relative probability .
717(2004); http://dx.doi.org/10.1063/1.1799679View Description Hide Description
We present the analysis of the data on reactions pp̄ annihilation into three pseudoscalar mesons. The combined analysis of the data taken with liquid hydrogen, gaseous hydrogen and deuteron targets shows an excellent agreement for the reactions investigated and allows to control the fraction of the P‐wave annihilation. The latter provides a better determination of tensor and vector states situated close to the edge of the phase volume. A possible presence of a 0(1290) is investigated.
717(2004); http://dx.doi.org/10.1063/1.1799680View Description Hide Description
The preliminary results of partial wave analysis of the Crystal Barrel data on p̄p annihilation at rest into π+π−π0η are presented. The data provide the information about production of meson channels, such as b 1π, h 1η from 1 S 0 and 3 S 1 p̄p state annihilation. The analysis shows the presence of the resonance and a possible presence of ρ2 in the mass region around 1600 MeV. The mass of was found to be 1620 ± 15 MeV.
717(2004); http://dx.doi.org/10.1063/1.1799681View Description Hide Description
Preliminary FOCUS results of the Dalitz‐plot analysis of and D + to three‐pion decays are presented. The K‐matrix formalism is applied for the first time to charm decays to fully exploit the already existing knowledge coming from the light‐meson spectroscopy experiments. In particular, all measured dynamics of S‐wave ππ scattering, characterized by broad/overlapping resonances and large non‐resonant background, can be properly accounted for. The results are discussed, along with their possible implications on the controversial nature of the σ meson.
717(2004); http://dx.doi.org/10.1063/1.1799682View Description Hide Description
We have measured the cross section σ(e+e− → π+π−γ) as a function of the π+π− invariant mass, M ππ, with the KLOE detector at DAΦNE ( W = m φ = 1.02 GeV ). The photon in the above process is due to Initial State Radiation. Dividing by a theoretical radiator function, we obtain the cross section σ(e+e− → π+π−) for the mass range . We extract the pion form factor and the hadronic contribution to the muon anomaly, a μ.
717(2004); http://dx.doi.org/10.1063/1.1799683View Description Hide Description
By scaling the parameters of meson‐meson unitarized Chiral Perturbation Theory amplitudes according to the QCD large Nc rules, one can study the spectroscopic nature of light meson resonances. The scalars σ, κ f 0(980) and, possibly, the a 0(980) do not seem to behave as q̄q states, in contrast to the vectors ρ(770) and K*(892). The behavior shown by the scalars is naturally explained in terms of diagrams with intermediate q̄q̄qq‐like states. Here we review our recent study and show how the results do not depend on the different fits to data.
717(2004); http://dx.doi.org/10.1063/1.1799684View Description Hide Description
Data from the Fermilab E835 experiment have been used to study the reaction p̄p → ηηπ0 at 5.2 GeV/c. A sample of 22 million six photons events has been analyzed to construct the Dalitz plot containing ∼ 80k ηηπ0 events. A partial wave analysis of the data has been done. At least five fJ ‐states decaying into ηη between ∼ 1.4 and 2.3 GeV are observed. Two f 0 states are identified with the popular candidates for the lightest scalar glueball, f 0(1500) and f 0(1710). In addition, at least five aJ ‐states decaying into ηπ0 up to 2.4 GeV are also observed. Masses, widths and spins of these resonances are determined by maximum likelihood analysis of the data and compared with the results in the literature.
717(2004); http://dx.doi.org/10.1063/1.1799686View Description Hide Description
Inclusive production in deep inelastic ep scattering at HERA has been studied with the ZEUS detector using an integrated luminosity of 120 pb−1. Two states are observed at masses of and 1726 ± 7 MeV, as well as an enhancement around 1300 MeV. The state at 1537 MeV is consistent with the well established . The state at 1726 MeV may be the glueball candidate f 0(1710). However, it’s width of is narrower than the PDG value of 125 ± 10 MeV for the f 0(1710).
717(2004); http://dx.doi.org/10.1063/1.1799687View Description Hide Description
Radiative decays of excited vector mesons are shown to provide good discrimination between the 23 S 1 and the 13 D 1 excitations of the ρ and ω and between these and a possible vector hybrid. Radiative decays of the 13 D 1 excitations of the ρ, ω and φ to the scalars f 0(1370), f 0(1500) and f 0(1710) provide a flavour filter, clarifying the extent of glueball mixing in the scalar states. A complementary approach to the latter is provided by the radiative decays of the scalars to the ρ, ω and φ.
717(2004); http://dx.doi.org/10.1063/1.1799688View Description Hide Description
The two‐photon reaction γγ → π+π−π0 was investigated using data collected with the Belle detector at KEKB. The spectrum was analyzed for resonance formation and interference between the dominant a 2(1320) and higher mass radial excitation tensor states. The observation includes the newly reported , and evidences for and .
717(2004); http://dx.doi.org/10.1063/1.1799689View Description Hide Description
Based on 5.8 × 107 J/ψ events collected by BESII, the mass and full width of ηc, as well as its decay branching ratios to K+K− π+π−, π+π−π+π−, , φφ and pp̄ are measured. Partial Wave Analysis (PWA) of J/ψ → γKK̄ and the study of J/ψ → γγV (V = ρ, φ) are performed. We also reported the measurements of J/ψ → pp̄ and J/ψ → π+π−π0.