Estimating nonlinear effects in forward dijet production in ultra-peripheral heavy ion collisions at the LHC
| Autor: | Krzysztof Kutak, Anna Stasto, Piotr Kotko, Mark Strikman, Sebastian Sapeta |
|---|---|
| Jazyk: | angličtina |
| Rok vydání: | 2017 |
| Předmět: |
Particle physics
Physics and Astronomy (miscellaneous) FOS: Physical sciences lcsh:Astrophysics 01 natural sciences High Energy Physics - Experiment Color-glass condensate High Energy Physics - Experiment (hep-ex) High Energy Physics - Phenomenology (hep-ph) Factorization 0103 physical sciences lcsh:QB460-466 lcsh:Nuclear and particle physics. Atomic energy. Radioactivity Twist 010306 general physics Nuclear Experiment Engineering (miscellaneous) Physics 010308 nuclear & particles physics High Energy Physics::Phenomenology HERA Gluon High Energy Physics - Phenomenology Dipole DGLAP lcsh:QC770-798 High Energy Physics::Experiment Nucleon |
| Zdroj: | European Physical Journal C European Physical Journal C: Particles and Fields, Vol 77, Iss 5, Pp 1-15 (2017) |
| Popis: | Using the framework that interpolates between the leading power limit of the Color Glass Condensate and the High Energy (or $k_{T}$) factorization we calculate the direct component of the forward dijet production in ultra-peripheral $\mathrm{Pb}$-$\mathrm{Pb}$ collisions at CM energy $5.1\,\mathrm{TeV}$ per nucleon pair. The formalism is applicable when the average transverse momentum of the dijet system $P_{T}$ is much bigger than the saturation scale $Q_{s}$, $P_{T}\gg Q_{s}$, while the imbalance of the dijet system can be arbitrary. The cross section is uniquely sensitive to the Weizs\"acker-Williams (WW) unintegrated gluon distribution, which is far less known from experimental data than the most common dipole gluon distribution appearing in inclusive small-$x$ processes. We have calculated cross sections and nuclear modification ratios using WW gluon distribution obtained from the dipole gluon density through the Gaussian approximation. The dipole gluon distribution used to get WW was fitted to the inclusive HERA data with the nonlinear extension of unified BFKL+DGLAP evolution equation. The saturation effects are visible but rather weak for realistic $p_{T}$ cut on the dijet system, reaching about $20\%$ with the cut as low as $6\,\mathrm{GeV}$. We find that the LO collinear factorization with nuclear leading twist shadowing predicts quite similar effects. Comment: 20 pages, 9 figures |
| Databáze: | OpenAIRE |
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