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Register a new userSearch for Exotic Baryons in 800 GeV pp (rtarrow) pXiPiX
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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.
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The Fermilab E866/NuSea Collaboration has measured the Drell-Yan dimuon cross sections in 800 GeV/$c$ $pp$ and $pd$ collisions. This represents the first measurement of the Drell-Yan cross section in $pp$ collisions over a broad kinematic region and the most extensive study to date of the Drell-Yan cross section in $pd$ collisions. The results indicate that recent global parton distribution fits provide a good description of the light antiquark sea in the nucleon over the Bjorken-$x$ range $0.03 lesssim x < 0.15$, but overestimate the valence quark distributions as $x to 1$.
The recent search for non $q bar{q}$ mesons in $pi^{-}p$ interactions at Brookhaven National Laboratory is summarized. Many final states such as $eta pi$, $eta pi^{-}$, $a_{0} pi$, $f_{1} pi$, $a_{2} pi$, $b_{1} pi$, which are favored decay modes of exotics, are under investigation.
We present measurements of the polarization of the $ J/psi $ produced in 800-GeV proton interactions with a copper target. Polarization of the $ J/psi $ is sensitive to the $ c bar{c} $ production and hadronization processes. A longitudinal polarization is observed at large $ x_{F} $, while at small $ x_{F} $ the state is produced essentially unpolarized or slightly transversely polarized. No significant variation of the polarization is observed versus $ p_{T} $.
A search for centrally produced charmonium states has been presented. There is no significant evidence for any charmonium production. An upper limit of 2 nb is found for the cross section of chic production using the decay chic(1P)-> J/psi gamma.
One of the most intriguing puzzles in hadron spectroscopy are the numerous charmonium-like states observed in the last decade, including charged states that are manifestly exotic. The $BABAR$ and Belle experiments have extensively studied those in B meson decays, initial state radiation processes and two photon reactions. We can question what we have understood after 11 year search in this field, and try to combine results to conclude on what these new unpredicted resonant states are, and how they can be accommodated in the theory. Big effort has been made from theoretical and experimental point of view, as the potential models unlikely explain the presence of so many enhancements, for mass values above the $D bar D$ threshold. In this report the $BABAR$ and Belle results of the two invariant mass systems of $J/psi phi$ and $J/psi omega$ are put in comparison in a search for non-conventional charmonium states. This involves the study of the systems of $J/psi K^+ K^-$ and $J/psi pi^+ pi^- pi^0$, respectively. There are strong theoretical arguments in favor of the presence of hybrids or exotic states, in those invariant mass distributions. Remarks on these data analyses are given, based on the $BABAR$ and Belle experimental results.
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