Gluon shadowing in the Glauber–Gribov model

Abstract

Abstract. New data from HERA experiment on (diffractive) deep inelastic scattering has been used to parameterize nucleon and Pomeron structure functions. Within the Gribov theory, the parameterizations were employed to calculate gluon shadowing for various heavy ions and compared our results with predictions from other models. Calculations for d+Au collisions at forward rapidities at ultra-relativistic energies have been made and are compared to RHIC data on the nuclear modification factor. Results for gluon shadowing are also confronted with recent data on the nuclear modification factor at √ s = 17.3 GeV at various values of the Feynman variable xF , and the energy dependence of the effect is discussed.PACS. 12.40.Nn Regge theory, duality, absorptive/optical models -13.60.Hb Total and inclusive cross sections (including deep inelastic processes) -13.85.-t Hadron-induced high-and super-high-energy interactions (energy > 10 GeV) -25.75.-q Relativistic heavy-ion collisions

Gluon density and functions from BK equation with local impact parameter dependence in DIS on nuclei

“…The closeness of all curves at the initial point of small x evolution (x = 0.045), shows that we indeed matched the small x evolution of the BK equation with the DGLAP framework of [21][22][23][24] in this point. This justifies the form of our initial conditions for the BK equation and the assumption (24). It is also clear, that all parameterizations [21][22][23][24] are based on the low energy data, whereas the high energy parts of the curves are the extrapolation of the established formulae into the region of small x.…”

“…Namely, obtained in absolutely different framework, our results interpolate between [22,23] parameterization of the ratio and stay in the "window" defined at low x by "extremal" parameterizations of the [21,24]. The closeness of all curves at the initial point of small x evolution (x = 0.045), shows that we indeed matched the small x evolution of the BK equation with the DGLAP framework of [21][22][23][24] in this point. This justifies the form of our initial conditions for the BK equation and the assumption (24).…”

“…The precise form of the initial conditions for the case of DIS on the proton was obtained in the paper [20] with the help of F 2 HERA data fit and we considered the DIS process on nuclei targets using the same functional form of the initial conditions. Surprisingly, in the given framework we obtained the integrated gluon density function which stays in the window of values defined by calculations [21][22][23][24], see Figs. 2 and 3.…”

“…The need of the comparison of our results for the integrated gluon density with the calculations from the [21][22][23][24] arises due the following reasons. The numbers, obtained for the DIS on nuclei in our approach, could not be directly compared with experimental data due a lack of the high energy DIS process data for the nuclei targets.…”

“…The procedure used for the determination of the parameters of the initial condition for the DIS on the proton could not be used therefore. Fortunately, the existing models of the integrated gluon density, [21][22][23][24], allow to extrapolate the integrated gluon density function till very small values of x, x ≈ 10 −7 . It gives to us a possibility to check how good (or bad) our calculations are and, therefore, the possibility to check how good (or bad) our initial conditions are.…”