Charm-anticharm baryon production asymmetries in photon-nucleon interactions
نویسندگان
چکیده
We report measurements of the charm-anticharm production asymmetries for Λc , Σ c , Σ 0 c , Σ ++∗ c , Σ 0∗ c , and Λ + c (2625) baryons from the Fermilab photoproduction experiment FOCUS (E831). These asymmetries are integrated over the region where the spectrometer has good acceptance. In addition, we have obtained results for the photoproduction asymmetries of the Λc baryons as functions of pL, p 2 T , and xF . The integrated asymmetry for Λ + c production, (σΛ+ c − σΛ− c ) / (σΛ+ c + σΛ− c ), is 0.111 ± 0.018 ± 0.012, significantly different from zero. The asymmetries of the excited states are consistent with the Λc asymmetry. The FOCUS experiment uses a photon beam on a Beryllium Oxide target to produce charm particles. In high energy photon-hadron interactions, pairs of charm-anticharm quarks are produced predominantly through photon-gluon fusion [1]. At leading order in Quantum Chromodynamics (QCD), the produced charm and anticharm particles are identically distributed in the kinematic variables. At next-to-leading order, small asymmetries are expected between charm and anticharm production [2,3,4]. However, these predicted asymmetries would be too small to be measured at the current level of experimental statistics. Interactions between the produced charm quarks and those
منابع مشابه
Charm-Anticharm Asymmetries in Photoproduction from Perturbative Recombination
The asymmetries between charm and anticharm mesons observed in fixedtarget photoproduction experiments are an order of magnitude larger than the asymmetries predicted by conventional perturbative QCD. We show that these charm meson asymmetries can be explained by a perturbative recombination mechanism for heavy meson production. In this process, a charm quark combines with a light antiquark fro...
متن کاملΛ + c − Λ − c production asymmetries in two component models
Experiments on charm hadroproduction have shown a substantial difference in the production of charm and anticharm hadrons. In this work we study Λ+ c and Λ c inclusive production in p−N interactions in the framework of two component models. We show that the recombination two component model gives a qualitatively and quantitatively good description of Λ c production while the intrinsic charm mod...
متن کاملLeading charm in hadron-nucleus interactions in the intrinsic charm model
Leading charm hadrons produced in hadron-nucleus interactions cannot be adequately described within the parton fusion model. Recent results on charm baryon production in X A interactions at 330 GeV with the WA89 detector disagree with fusion predictions. Intrinsic heavy quark pairs in the Z (dds) wavefunction provide a simple mechanism for producing fast charm hadrons. We calculate leading char...
متن کاملThe Quark / Antiquark Asymmetry of the Nucleon Sea ∗
Although the distributions of sea quarks and antiquarks generated by leadingtwist QCD evolution through gluon splitting g → qq are necessarily CP symmetric, the distributions of nonvalence quarks and antiquarks which are intrinsic to the nucleon’s bound state wavefunction need not be identical. In this paper we investigate the sea quark/antiquark asymmetries in the nucleon wavefunction which ar...
متن کاملThe Quarkkantiquark Asymmetry of the Nucleon Sea
Although the distributions of sea quarks and antiquarks generated by leadingtwist QCD evolution through gluon splitting g ! qq are necessarily CP symmetric, the distributions of nonvalence quarks and antiquarks which are intrinsic to the nucleon's bound state wavefunction need not be identical. In this paper we investigate the sea quark/antiquark asymmetries in the nucleon wavefunction which ar...
متن کامل