Quarkonia production with the HERA-B experiment

Abstract

Abstract. Measurements of the dependence of the J/ψ production cross section on its kinematic variables as well as on the target atomic numbers for 920 GeV/c protons incident on different targets have been made with the HERA B detector. The large collected di-lepton sample allows to study the production ratio of ψ(2S) to J/ψ and of χ c to J/ψ. We also report on measurements of the bb and Υ production cross section.

J/ψProduction and Nuclear Effects ford+Auandp+pCollisions atAdler1, Afanasiev2, Aidala3 et al. 2006Phys. Rev. Lett.

“…These data provide the first measurement of the nuclear dependence of J/ψ production at this energy, a much higher energy than previous p + A measurements from fixed-target experiments at √ s N N < ∼ 40 GeV [9,10,11,12,13]. Although our measurements are for d + A, the nuclear effects on the J/ψ in deuterium were found to be small at lower energies [14].…”

Pentaquarks in chiral soliton models

“…There are different possibilities to have exotic baryon states: a) positive strangeness S > 0 (or negative charm C < 0, or positive beauty), since s-quark has S = −1 and c-quark C = +1, b) large (in modulus) negative strangeness S < −3B, B -baryon number; similar for charm or beauty, c) large enough isospin I > (3B + S)/2 , if −3B ≤ S ≤ 0, or charge Q > 2B + S or Q < −B in view of Gell-Mann -Nishijima relation Q = I 3 + Y /2. 1 Based partly on the talks presented at the International Seminar on High Energy Physics Quarks-2004, Pushkinogorie, Russia, May [24][25][26][27][28][29][30]2004; International Workshop on Quantum Field Theory and High Energy Physics QFTHEP-04, Saint-Petersburg, Russia, June [17][18][19][20][21][22][23]2004, and Symposium of London Mathematical Society "Topological Solitons and their Applications", Durham, UK, August 2- 12,2004. Slightly reduced version of this paper is available as E-print hep-ph/0507028.…”

“…However, this resonance is not confirmed by HERA-B, ZEUS, CDF, WA-89, COMPASS collaborations (see e.g. [16,22]), although there is no direct contradiction with NA49 experiment because other reactions have been used and mostly at higher energies, so, upper bounds on the production cross sections of Φ/Ξ 3/2 have been obtained in this way, see [22,23] for compilation of these results.…”

Improved measurement of thebb¯production cross section in 920 GeV fixed-target proton-nucleus collisions

“…Since these are available in the positive x F region only, we assume a symmetric x F distribution of prompt J= production: d=dx F 1 ÿ jx F j c where c 6:38 0:24 [36]. This extension conforms both to all the basic charmonium production models and to our own data on the J= differential cross sections [37]. The model dependence of the generated p T spectrum is of minor importance since the acceptance for the J= p T is essentially flat.…”