摘要:

The DIRAC experiment aims to measure the lifetime of &pgr;+&pgr;−atoms in the ground state with 10&percent; precision, using the 24 GeV/cproton beam of the CERN Proton Synchrotron. As the value of the above lifetime of order 10−15s is dictated by a strong interaction at low energy, the precise measurement of this quantity enables to determine a combination of S‐wave pion scattering lengths to 5&percent;. Pion scattering lengths have been calculated in the framework of chiral perturbation theory with high precision. Thus the accurate measurement of these values would submit the understanding of chiral symmetry breaking of QCD to a crucial test. Some preliminary results from the analysis of a 2000 data sample are presented. © 2002 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1482531

出版商:AIP    

年代:1902

数据来源: AIP

摘要:

We have succeeded in observing the 1sand 2pbound pionic states in205Pb nucleus as well separated peaks in the excitation spectrum of the206Pb(d,3He) reaction. The observed spectrum agreed quite well with the theoretical prediction where the formation cross section was calculated for the deeply bound pionic states. These states are accommodated in proximity to the nuclear surface as halo states in a potential provided by the attractive Coulomb and the repulsive core. The binding energies and the widths were precisely determined, and the values were used to deduce the unknowns‐wave part of the &pgr;‐nucleus interaction and to translate it to the effective pion mass in nuclear matter. © 2002 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1482532

出版商:AIP    

年代:1902

数据来源: AIP

摘要:

We study a production of supernarrow dibaryons, the decay of which into two nucleons is forbidden by the Pauli exclusion principle, in the reactionspd→p+pX1andpd→p+dX2at Linear Accelerator of INR (Moscow). Dibaryons with masses 1904±2, 1926±2 and 1942±2 MeV have been observed in missing massMpX1spectra. In missing massMX1spectra, the peaks atMX1= 966±2, 986±2, and 1003±2 MeV have been found. The analysis of the data obtained leads to the conclusion that the observed dibaryons are supernarrow dibaryons. The possible interpretation of “exotic baryon states” with small masses is discussed. © 2002 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1482533

出版商:AIP    

年代:1902

数据来源: AIP

摘要:

The energy spectrum for high energy &ggr;‐rays (E&ggr;⩾ 10 MeV) from the processpp→ &ggr;&ggr;Xemitted at 90° in the laboratory frame has been measured at 216 MeV. The resulting photon energy spectrum extracted from &ggr; − &ggr; coincidence events consists of a narrow peak (5.3&sgr;) at a photon energy of about 24 MeV and a relatively broad peak (3.5&sgr;) in the energy range of (50 – 70) MeV. This behavior of the photon energy spectrum is interpreted as a signature of the exotic dibaryon resonanced1⋆with a mass of about 1956 MeV which is assumed to be formed in the radiative processpp → &ggr;d1⋆followed by its electromagnetic decay via thed1⋆ → pp&ggr;mode. The experimental spectrum is compared with those obtained by means of Monte Carlo simulations. © 2002 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1482534

出版商:AIP    

年代:1902

数据来源: AIP

摘要:

Narrow low mass exotic hadronic structures were recently observed in mesons, baryons and dibaryons. Narrow mesons, in the mass range 300⩽M⩽ 750 MeV, were observed using the pp → ppX reaction. Narrow baryons in the mass range 1000⩽M⩽ 1400 MeV were observed using the pp → p&pgr;+X and dp → ppX reactions. The statistical significances of these structures vary up to 4.6 standard deviations (S.D.) for mesons and up to 16.9 S.D. for baryons. These exotic states are associated with precursor quark deconfinement. © 2002 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1482535

出版商:AIP    

年代:1902

数据来源: AIP

摘要:

A manifestation of narrow diproton resonances in the early discovered global structure of proton‐proton total cross section (see [8, 9]) at low energies is discussed. It is also discussed the existence of new particle with the mass 1.833MeVpredicted early. © 2002 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1482536

出版商:AIP    

年代:1902

数据来源: AIP

摘要:

We report results of a high resolution search for the tensor glueball candidate &xgr;(2230) in a p¯p formation experiment. &pgr;0&pgr;0and &eegr;&eegr; decay channels were measured in a scan of the mass region 2220 MeV to 2240 MeV. No evidence for the existence of &xgr;(2230) was found. 95&percent; confidence upper limits for the possible existence of &xgr; are presented. © 2002 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1482537

出版商:AIP    

年代:1902

数据来源: AIP

摘要:

Recent experimental data on the antiproton in‐flight annihilation on light nuclei are analysed. The reasons of the observed equality of the p¯‐hydrogen, p¯‐deuterium, and p¯‐helium annihilation cross sections at low energies are discussed. The calculations within a simple optical model confirm that the S‐wave contribution to the antiproton‐nucleus annihilation cross section is approximately the same for all nuclei. © 2002 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1482538

出版商:AIP    

年代:1902

数据来源: AIP

摘要:

The preliminary results of the analysis ofp¯n→ &pgr;−3&pgr;° annihilation at rest are presented. About 205.520 events were taken with the Crystal Barrel Detector with a liquid deuterium target. A full four‐body‐partial wave analysis with the maximum likelihood method was applied for a part of this sample. The dominant intermediate states in the data consist of a &rgr;‐meson combined with the (&pgr;&pgr;) S‐wave or with the D‐wave (f2(1270)). Beneath the well established resonances the partial wave analysis yields a broad resonant structure in the exotic (&rgr;&pgr;) P‐wave at about 1500MeV/c2. In addition, the (&rgr;&pgr;)‐system is found in thea1(1260),a1(1640),a2(1320),a2(1650), &pgr;(1300) and &pgr;(1800) states. © 2002 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1482539

出版商:AIP    

年代:1902

数据来源: AIP

摘要:

To investigate the possible existence of an exoticJPC= 1−+‐wave decaying into &pgr;&eegr;′ in pp¯‐annihilation at rest, the reaction pp¯ → &pgr;+&pgr;−&pgr;+&pgr;−&eegr; was analysed. The data was taken with the Crystal Barrel experiment. The preliminary partial wave analysis requires a resonant (&eegr;′&pgr;)‐P‐wave, with a mass of 1555±50 MeV/c2and a width of 200±100 MeV/c2. © 2002 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1482540

出版商:AIP    

年代:1902

数据来源: AIP