Abstract
The exclusive photoproduction of vector mesons ( and ) is investigated by considering the next-to-leading order corrections in the framework of the color glass condensate. We compare the next-to-leading order modified dipole amplitude with the HERA data, finding a good agreement. Our studies show that the from the leading order, running coupling, and collinearly improved next-to-leading order dipole amplitudes are 2.159, 1.097, and 0.932 for the elastic cross-section, and 2.056, 1.449, and 1.357 for the differential cross-section, respectively. The results indicate that the higher-order corrections contribute significantly to the vector meson productions, and the description of the experimental data is dramatically improved once the higher order corrections are included. We extend the next-to-leading order exclusive vector meson production model to LHC energies using the same parameters obtained from HERA. We find that our model provides a rather good description of the and data in proton-proton collisions at 7 TeV and 13 TeV in LHCb experiments.
Highlights
Perturbative Quantum Chromodynamics predicts that the gluon density inside a hadron grows rapidly with increasing energy and saturates eventually at sufficiently high energies, forming a new state of high density gluonic matter called Color Glass Condensate (CGC)[1]
It was found that the experimental data of the total cross section of the electron-proton deep inelastic scattering (DIS) at HEAR in small x (x < 0.01) region shows a geometric scaling behavior[8], which give a strong evidence of the CGC theory
Our result shows that the rapidity evolution of the dipole scattering amplitude is still suppressed by the full NLO effects, but the evolution speed is rebound as compared to the running coupling case due to a compensation effect made by gluon loops
Summary
Perturbative Quantum Chromodynamics (pQCD) predicts that the gluon density inside a hadron grows rapidly with increasing energy (or decreasing Bjorken-x) and saturates eventually at sufficiently high energies, forming a new state of high density gluonic matter called Color Glass Condensate (CGC)[1]. The authors in Refs.[44, 45] used the dipole amplitude resulting from the rcBK equation to fit the inclusive small x HERA data They obtained a rather good description of the data since the running coupling effect significantly slows down the growth of the dipole amplitude with increasing energy. We find that the χ2/d.o.f for elastic cross section (2.159) and differential cross section (2.056) in the leading logarithmic approximation are greatly improved after including one of the NLO corrections, running coupling (1.097 for the elastic cross section and 1.449 for differential cross section) This outcome indicates that the higher order corrections play an important role in the quantitative description of the diffractive vector meson production data. We see that the high order corrections suppress the evolution of the dipole amplitude
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