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Register a new userEmploying RHIC and LHC data to determine TMD gluon density in a proton
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Transverse momentum dependent (TMD) parton distributions in a proton are important in high energy physics from both theoretical and phenomenological points of view. Using the latest RHIC and LHC data on the inclusive soft hadron production in $pp$ and $AA$ collisions at small transverse momenta, we determine the parameters of the initial TMD gluon density, derived in the framework of quark-gluon string model at the low scale $mu_0 sim 1 - 2$ GeV and refine its large-$x$ behaviour using the LHC data on the $t bar t$ production at $sqrt s = 13$ TeV. Then, we apply the Catani-Ciafaloni-Fiorani-Marchesini (CCFM) evolution equation to extend the obtained TMD gluon density to the whole kinematical region. In addition, the complementary TMD valence and sea quark distributions are generated. The latter are evaluated in the approximation where the gluon-to-quark splitting occurs at the last evolution step using the TMD gluon-to-quark splitting function. Several phenomenological applications of the proposed TMD quark and gluon densities to the LHC processes are discussed.
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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 low scale mu0^2 ~ 1 GeV^2 from the fit of the 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 Balitsky-Fadin-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 mu^2 numerically using the Catani-Ciafoloni-Fiorani-Marchesini (CCFM) gluon evolution equation. A special attention is put to the phenomenological applications of obtained TMD gluon density to some LHC processes, which are sensitive to the gluon content of a proton.
We calculate power corrections to TMD factorization for particle production by gluon-gluon fusion in hadron-hadron collisions.
The experimental data from the RHIC and LHC experiments of invariant pT spectra in A+A and p + p collisions are analysed with Tsallis distributions in different approaches. The information about the freeze-out surface in terms of freeze-out volume, temperature, chemical potential and radial flow velocity for different particle species are obtained. Further, these parameters are studied as a function of the mass of the secondary particles. A mass-dependent differential freeze-out is observed which does not seem to distinguish between particles and their antiparticles. Further a mass-hierarchy in the radial flow is observed, meaning heavier particles suffer lower radial flow. Tsallis distribution function at finite chemical potential is used to study the mass dependence of chemical potential. The peripheral heavy-ion and proton-proton collisions at the same energies seem to be equivalent in terms of the extracted thermodynamic parameters.
We revisit the model-independent decomposition of the gluon correlator, producing T-even and T-odd gluon transverse momentum distributions (TMDs), at leading twist. We propose an expansion of the gluon correlator, using a basis of four tensors (one antisymmetric and three symmetric), which are expressed through generators of the $U(2)$ group acting in the two-dimensional transverse plane. One can do clear interpretations of the two transversity T-odd TMDs with linear polarization of gluons: symmetric and asymmetric under permutation of the transverse spin of the nucleon and the transverse momentum of the gluon. Using light-front wave function (LFWF) representation, we also derive T-even and T-odd gluon TMDs in the nucleon at leading twist. The gluon-three-quark Fock component in the nucleon is considered as bound state of gluon and three-quark core (spectator). The TMDs are constructed as factorized product of two LFWFs and gluonic matrix encoding information about both T-even and T-odd TMDs. In particular, T-odd TMDs arise due to gluon rescattering between the gluon and three-quark spectator. Gluon rescattering effects are parametrized by unknown scalar functions depending on the $x$ and ${bf k}_{perp}$ variables. Our gluon TDMs obey the model-independent Mulders-Rodrigues inequalities. We also derive new sum rules (SRs) involving T-even TMDs. One of the SRs states that the square of the unpolarized TMD is equal to a sum of the squares of three polarized TMDs. Based on the SR derived for T-even gluon TMDs, we make a conjecture that there should two additional SRs involving T-odd gluon TMDs, valid at orders $alpha_s$ and $alpha_s^2$. Then, we check these SRs at small and large values of $x$. We think that our study could serve as useful input for future phenomenological studies of TMDs.
We study the rapidity evolution of gluon transverse momentum dependent distributions appearing in processes of particle production and show how this evolution changes from small to moderate Bjorken x.
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