Calculation of the pentaquark width using QCD sum rules

Abstract

The pentaquark width is calculated in QCD sum rules. Result for Γ Θ show, that Γ Θ can vary in the region less than 1M eV . The main conclusion is, that if pentaquark is genuine states then sum rules really predict the narrow width of pentaquark θ + , and the suppression of the width is both parametrical and numerical.PACS: 12.39 Dc, 12.38 In this paper we will discuss the the narrow exotic baryon resonance Θ + with quark content Θ + = uudds and mass 1.54 GeV. This resonance had been discovered by two groups [1,2]. Later, the existence of this resonance was confirmed by many other groups, although some searches for it were unsuccessful. Moreover, last year some groups, which have seen pentaquark, in the new experiments with higher statistics. reported null result for pentaquark signal (CLAS experiments on hydrogen and deuterium [3], BELLE [4]) but at the same time DIANA [5], and also LEPS, SVD-2 confirm their results with higher statistic(see [6] for the review).So the status of Θ + , predicted in 1997 by D.Diakonov, V.Petrov and M.Polyakov [7] in the Chiral Soliton Model, till now is doubtful. (Some theoretical reviews are given in [8,9]).One of the most interesting features of Θ + is its very narrow width. Experimentally, only an upper limit was found, the stringer bound was presented in [2]: Γ < 9MeV . The phase analysis of KN scattering results in the even stronger limit on Γ [10], Γ < 1MeV . A close to the latter limitation was found in [11] from the analysis of Kd → ppK reaction and in [12] from K + Xe collisions data [2]. Also [4] from the negative result of the experiment give the upper limit for pentaquark width less than 640KeVSuch extremely narrow width of Θ + (less than 1MeV ) seems to be very interesting theoretical problem. In the paper [13], [14] it was shown, that if pentaquark is genuine 1

Is there any "LSND anomaly"?

“…Hadron production has been simulated by Geant4 [3] and FLUKA [4] codes. Then, pion production by protons has been adjusted to the HARP-CDP data, and pion production by neutrons has been tuned according to the results of other experiments [5]. In addition, we "emulated" the LSND procedure of neutrino flux calculation using the LSND's pion production parametrization [6], to demonstrate understanding of the LSND geometry.…”