ISSN:0094-243X    

DOI:10.1063/1.1799671

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

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 conventionalqq¯‐pairs orqqq‐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. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1799672

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

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. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1799673

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

The KLOE experiment at the Frascati &fgr; factory, Da&Fgr;ne, has collected ∼500 pb−1, i.e. 1.5 × 109&fgr; decays. At the &fgr; factory it is possible to select pure KLand KSbeams. 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 &Fgr; decays at rest collected so far. The cross section &sgr;(e+e−→ &pgr;+&pgr;−&ggr;) below 1 GeV, relevant for the precise evaluation of the muon magnetic moment, has been measured with a statistical accuracy better than 1&percent;. For the KS, we obtained the ratio of the branching fractions &Ggr;(KS→ &pgr;+&pgr;−(&ggr;))/&Ggr;(KS→ &pgr;0&pgr;0) = (2.239 ± 0.003stat± 0.015syst), fully inclusive of the &pgr;&pgr;&ggr; final state. The analysis of the ∼20,000 KSsemileptonic decays KS→ &pgr;e&ngr; is being finalized providing precise measurements of both, the KSsemileptonic branching ratio, and Rex+, i.e. the &Dgr;S = &Dgr;Q rule violation parameter. For theKL, we obtained the ratio &Ggr;(KL→ &ggr;&ggr;)/&Ggr;(KL→ &pgr;0&pgr;0&pgr;0) = (2.80 ± 0.02stat± 0.02syst) × 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 &fgr; radiative decays, both in scalar and pseudo‐scalar mesons, have been analyzed giving new measurements of the &eegr; − &eegr;′ mixing angle, and of the &fgr; →a0(980)&ggr;, &fgr; →f0(980)&ggr; branching ratios. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1799674

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

High resolution has been discouraged in meson spectrometry for 4 decades by theDoctrine of Experiments Incompatible with Theory (DEIT). DEITa priorirejects narrow hadron resonances on the paradigm thatonly broadhadron peaks, &Ggr;⩾ 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&percent; 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, &Ggr;, is different from the observable (‘apparent’) width, &Ggr;’: &Ggr;< &Ggr;’ (2) &Ggr; of all meson states are narrow and can be observed only at or near the maximum |t| reachable in the reaction, and (3) &Ggr; of all meson resonances are subject to broadening as |t| decreases. Since both &Ggr;’ and the production &sgr; 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 &pgr;P→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 &ohgr;→2&pgr;, and the related correspondence between Werner Heisenberg and this author, is narrated. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1799675

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

An analysis of the processes with initial state radiation (ISR) has been performed using 90fb−1ofBABARdata. The selection of &mgr;+&mgr;−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 directe+e−cross sections. The presentBABARdata are already competitive withe+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 ofe+e−→ hadronscross section toe+e−→ &mgr;+&mgr;−— and thereby to impact the (g− 2)&mgr;measurement.The ISR technic gives an access toJ/&psgr; production. TheJ/&psgr; decays to &mgr;&mgr;, 4&pgr;, 2K2&pgr; and 4K have been selected and new preliminary measurements of branching ratios performed with comparable or typically better accuracy than PDG. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1799676

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

First results of a study of thee+e−→ &pgr;+&pgr;−&pgr;+&pgr;−&ggr; process with hard photon emitted from initial state are presented. About 60000 fully reconstructed events have been selected based on 89.3fb−1ofBABARdata. The invariant mass of the hadronic final state defines the effective collision c.m. energy, and soBABARISR data can be compared to the relevant directe+e−measurements. From obtained 4&pgr; mass spectrum we evaluatee+e−→ &pgr;+&pgr;−&pgr;+&pgr;−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&percent; and comparable with the beste+e−data. The cross sections for identified 2K2&pgr; and 4K final states also have been presented. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1799677

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

The review of the SND results of thee+e−→ &pgr;+&pgr;−&pgr;0process study in the energy ranges = 0.42 − 1.38 GeVat VEPP‐2M collider, based on about 2 × 106selected events, is presented. The total cross section, parameters of the &rgr;, &ohgr;, &fgr;, resonances, and &ohgr;′, &ohgr;″ states were obtained. It was found that &rgr;&pgr; and &ohgr;&pgr;0intermediate states describe the reaction dynamics. The experimental data cannot be described by a sum of only &ohgr;, &fgr;, &ohgr;′ and &ohgr;″ resonances contributions. This can be interpreted as a manifestation of the &rgr; → 3&pgr; decay, suppressed byG‐parity, with relative probabilityB(&rgr; → 3&pgr;) = (1.01 ±0.360.54±0.034) × 10−4. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1799678

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

We present the analysis of the data on reactionspp¯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 ofa0(1290) is investigated. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1799679

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

The preliminary results of partial wave analysis of the Crystal Barrel data onp¯pannihilation at rest into &pgr;+&pgr;−&pgr;0&eegr; are presented. The data provide the information about production of meson channels, such asb1&pgr;,h1&eegr; from1S0and3S1p¯pstate annihilation. The analysis shows the presence of theb1*resonance and a possible presence of &rgr;2in the mass region around 1600 MeV. The mass ofb1*was found to be 1620 ± 15 MeV. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1799680

出版商:AIP    

年代:1904

数据来源: AIP