Delineating the saturation boundary: linear vs non-linear QCD evolution from HERA data to LHC phenomenology

Quiroga-Arias, Paloma; Milhano, J.Guilherme; Rojo, Juan; Albacete, Javier L.

doi:10.1016/j.nuclphysa.2012.12.078

Article
Report number	arXiv:1208.6246
Title	Delineating the saturation boundary: linear vs non-linear QCD evolution from HERA data to LHC phenomenology
Author(s)	Quiroga-Arias, Paloma (Paris, LPTHE) ; Albacete, Javier L. (Orsay, IPN ; IPhT, Saclay) ; Milhano, J.Guilherme (Lisbon, CENTRA ; CERN) ; Rojo, Juan (CERN)
Publication	2013
Imprint	31 Aug 2012
Number of pages	4
Note	Comments: to appear in the proceedings of the 5th international Conference on Hard and Electromagnetic Probes of High-Energy Nuclear Collisions (Hard Probes 2012) to appear in the proceedings of the 5th international Conference on Hard and Electromagnetic Probes of High-Energy Nuclear Collisions (Hard Probes 2012)
In:	Nucl. Phys. A 910-911 (2013) 446-449
DOI	10.1016/j.nuclphysa.2012.12.078
Subject category	Particle Physics - Phenomenology
Abstract	The forthcoming p+Pb run at the LHC will provide crucial in formation on the initial state effects of heavy ion collisions and on the gluon saturation phenomena. In turn, most of the saturation inspired phenomenology in heavy ion collisions borrows substantial empiric information from the analysis of e+p data, where abundant high quality data on the small-x kinematic region is available. Indeed, the very precise combined HERA data provides a testing ground in which the relevance of novel QCD regimes, other than the successful linear DGLAP evolution, in small-x inclusive DIS data can be ascertained. We present a study of the dependence of the AAMQS fits, based on the running coupling BK non-linear evolution equations (rcBK), on the fitted dataset. This allows for the identification of the kinematical region where rcBK accurately describes the data, and thus for the determination of its applicability boundary. It also set important constraints to the saturation models used to model the early stages of heavy ion collisions. Finally we compare the rcBK results with NNLO DGLAP fits, obtained with the NNPDF methodology with analogous kinematical cuts. Further, we explore the impact on LHC phenomenology of applying stringent kinematical cuts to the low-x HERA data in a DGLAP fit.
Copyright/License	Copyright © unknown. Published by Elsevier B.V.

$\small Sketch of the kinematic plane with cuts for DGLAP and rcBK fits. The arrows indicate backwards evolution in either formalism to the unfitted {\it test} region. This method provides a direct test of fit stability under changes in the boundary conditions.$ $(\emph{left}) Comparison of the result for reduced cross section obtained with rcBK fits with different cuts and HERA data for four different bins in $Q^{2}$. (\emph{right}) rcBK cut fit with $x_{\rm cut}=10^{-4}$ and the DGLAP fit with $A_{\rm cut}=1.5$, compared to the experimental HERA-I data. The comparison is shown in four different bins in $Q^{2}$. In the DGLAP case the band corresponds to the PDF uncertainties.$ $(\emph{left}) Comparison of the result for reduced cross section obtained with rcBK fits with different cuts and HERA data for four different bins in $Q^{2}$. (\emph{right}) rcBK cut fit with $x_{\rm cut}=10^{-4}$ and the DGLAP fit with $A_{\rm cut}=1.5$, compared to the experimental HERA-I data. The comparison is shown in four different bins in $Q^{2}$. In the DGLAP case the band corresponds to the PDF uncertainties.$ Show more plots

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Journalen skapades 2012-08-31, och modifierades senast 2024-05-08

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