2003/01/31 by Jian-Ping Ma, J. P. Ma
Mathematics · Physics and Astronomy · #Charm (quantum number) #Geometry #Gluon #Hadron #High-Energy Particle Collisions Research #Inverse #Mathematics #Operator (biology) #Particle physics #Particle physics theoretical and experimental studies #Perturbative QCD #Physics #Quantum Chromodynamics and Particle Interactions #Quantum chromodynamics #Quark #hep-ex #hep-ph
paper · pdf · doi:10.1016/j.nuclphysa.2003.08.016
published as Nucl.Phys.A727:333-352,2003 · 20 pages with 3 figures. Text improved
arxiv created 2003/08/06 · openalex publication_date 2003/09/17 · arxiv updated 2009/11/30 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
Diffractive photoproduction of ηc is an important process to study the effect of Odderon, whose existence is still not confirmed in experiment. A detailed interpretation of Odderon in QCD, i.e., in terms of gluons is also unclear.Taking charm quarks as heavy quarks, we can use NRQCD and take ηc as a c c bound state. Hence, in the production of ηca free c c pair is first produced and this pair is transformed into ηc subsequently.In the forward region of the kinematics, the c c pair interacts with initial hadron through exchanges of soft gluons. This interaction can be studied with HQET, which provides a systematic expansion in the inverse of the c-quark mass mc. We find that the calculation of the S-matrix element in the forward region can be formulated as the problem of solving a wave function of a c-quark propagating in a background field of soft gluons. At leading order we find that the differential cross-section can be expressed with four functions, which are defined with a twist-3 operator of gluons. The effect of exchanging a Odderon can be identified with this operator in our case. We discuss our results in detail and compare them with those obtained in previous studies. Our results and those from other studies show that the differential cross-section is very small in the forward region. We also show that the production through photon exchange is dominant in the extremely forward region, hence the effect of Odderon exchange can not be identified in this region.For completeness we also give results for diffractive photoproduction of J/Ψ.