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Register a new userSearch for Exotic Baryons with Hidden Strangeness in the Experiments of the Sphinx Collaboration in Diffractive and Coulomb Production Processes
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L. G. Landsberg
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Experimental results of the SPHINX Collaboration on studying proton diffractive production processes are presented. Evidences for new baryon states with masses >1.8 GeV were obtained in hyperon-kaon effective mass spectra in several reactions. New data for the diffractive reaction p+N->[Sigma0 K+]+N at Ep=70 GeV were obtained with partially upgraded SPHINX setup. The data are in a good agreement with the results of our previous study of this reaction. In the mass spectrum M(Sigma0 K+) a structure at the threshold region with a mass about 1800 MeV and a distinct X(2000) peak with M=1989+/-6 MeV and Gamma=91+/-20 MeV are observed. Unusual features of the massive X(2000) state (narrow decay width, anomalously large branching ratio for the decay channel with strange particle emission) make it a serious candidate for a cryptoexotic pentaquark baryon with hidden strangeness |qqqs sbar>. We also present new results on the narrow threshold structure X(1810) with M=1807+/-7 MeV and Gamma=62+/-19 MeV which is produced in the region of very small pt**2<0.01 GeV**2. The possibility of the Coulomb production mechanism for X(1810) is discussed.
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Evidences for new baryon states with mass >1.8 GeV were obtained in the experiments of the SPHINX Collaboration in studying hyperon-kaon mass spectra in several proton diffractive reactions. The main result of these experiments is the observation of X(2000)->SIGMA K state with unusual dynamical features (narrow width, anomalously large branching ratios for the decay channels with strange particle emission). The possibility of the interpretation of this state as cryptoexotic pentaquark baryon with hidden strangeness is discussed. The additional data which are supported the real existence of X(2000) baryon are also presented.
We report the results of a high-statistics, sensitive search for narrow baryon resonances decaying to $Xi^-pi^-$, $Xi^-pi^+$, $bar{Xi}^+pi^-$, and $bar{Xi}^+pi^+$. The only resonances observed are the well known $Xi^0(1530)$ and $bar{Xi^0}(1530)$. No evidence is found for a state near 1862 MeV, previously reported by NA49cite{NA49}. At the 95% confidence level, we find the upper limit for the production of a Gaussian enhancement with $sigma=7.6$ MeV in the $Xi^-pi^-$ effective mass spectrum to be 0.3% of the number of observed $Xi^0(1530)toXi^-pi^+$. We find similarly restrictive upper limits for an enhancement at 1862 MeV in the $Xi^-pi^+$, $bar{Xi}^+pi^-$, and $bar{Xi}^+pi^+$ mass spectra.
The role of Strangeness as a signal of the Quark Gluon Plasma in relativistic heavy ion experiments is discussed. The current experimental status is briefly presented. Several scenarios which explain the CERN data are discussed.
In the experiment with the SPHINX spectrometer in 1995-99 a new baryon state X(2000) -> Sigma^0K^+ was observed in the proton diffractive reactions p + N(C) -> Sigma^0K^+ + N(C). The main parameters of X(2000)^+ baryon are M = 1986 +- 6 MeV, Gamma = 98 +- 21 MeV. Unusual features of massive X(2000) state (narrow decay width Gamma/M simeq 0.05, anomalously large branching ratio with strange particle emission) make it serious candidate for cryptoexotic pentaquark baryon with hidden strangeness. New data on the SPHINX with by an order of magnitude enlarge statistics are in agreement with previous data and are supported our conclusions. We propose further studies X(2000) baryon production in the meson reactions with baryon exchange: pi^{+-} + p -> X(2000)^+ + pi^{+-} OZI - forbidden suppressed reaction for the state |qqqsbar{s}>) and K^{+-} + p -> X(2000)^+ + K^{+-} (OZI - allowed reaction). If the value of R=BR[pi^{+-} + p -> X(2000)^+ + pi^{+-}]/BR[K^{+-}+p -> X(2000)^+ + K^{+-}]<<1 it will be the crucial argument in favor of X(2000)= |qqqsbar{s}>) structure. These experiments may be done on IHEP separated kaon beam with OKA spectrometer.
If light hidden sector photons exist, they could be produced through kinetic mixing with solar photons in the eV energy range. We propose to search for this hypothetical hidden photon flux with the Super-Kamiokande and/or upgraded CAST detectors. The proposed experiments are sensitive to mixing strengths as small as 10^-9 for hidden photon masses in the sub eV region and, in the case of non-observation, would improve limits recently obtained from photon regeneration laser experiments in this mass region.
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