Significance of nonperturbative input to the transverse momentum dependent gluon density for hard processes at the LHC

Abstract

We study the role of the non-perturbative input to the transverse momentum dependent (TMD) gluon density in hard processes at the LHC. We derive the input TMD gluon distribution at a low scale µ 2 0 ∼ 1 GeV 2 from a fit of inclusive hadron spectra measured at low transverse momenta in pp collisions at the LHC and demonstrate that the best description of these spectra for larger hadron transverse momenta can be achieved by matching the derived TMD gluon distribution with the exact solution of the BalitskyFadin-Kuraev-Lipatov (BFKL) equation obtained at low x and small gluon transverse momenta outside the saturation region. Then, we extend the input TMD gluon density to higher µ 2 numerically using the Catani-Ciafoloni-Fiorani-Marchesini (CCFM) gluon evolution equation. Special attention is paid to phenomenological applications of the obtained TMD gluon density to some LHC processes, which are sensitive to the gluon content of a proton.

Significance of gluon density for soft and hard processes at LHC

“…Once again, we conclude that the best description of the LHC data [14,15] is achieved with the proposed MD'2015 gluon density. More detailed results of the suggested approach represented in our paper [10].…”

“…(2) he CCFM-evolved TMD gluon densities in the proton calculated as a function of the gluon transverse momentum k 2 T at x = 10 −4 and two values of µ 2 is presented. The details of the calculation are presented in [10].…”

“…As for example, we presented here the results on the inclusive production of b-jets and correlation between two b-jets produced in pp collision. In [10] PoS(DIS2016)038…”

“…Significance of gluon density for soft and hard processes at LHC G. I. Lykasov where ρ q is the quark contribution calculated within the quark-gluon string model (QGSM) and ρ g is the gluon contribution, see [10], which can be calculated using the proposed TMD gluon density (1) and (2). (1/σ) dσ/dy dp (1/σ) dσ/dy dp…”

Summary of WG1: Structure functions and parton densities

“…Saturation effects in the same framework were discussed [32], and TMDlib libraries and a plotter were introduced for the first time [33], also produced by the same group. There was also a contribution studying the role of the nonperturbative input to the (TMD) gluon density in hard processes at the LHC, and deriving the input distribution from a fit of inclusive hadron spectra measured at low transverse momenta in pp collisions at the LHC [34].…”