Abstract
We investigate the possibility to constrain the intrinsic charm probability w_{mathrm{c} {bar{{mathrm{c}}}}}= P_{{mathrm{c}{bar{mathrm{c}}}} /mathrm{p}} using first ATLAS data on the associated production of prompt photons and charm-quark jets in pp collisions at sqrt{s} = 8 TeV. The upper limit w_{mathrm{c} {bar{{mathrm{c}}}}}< 1.93 % is obtained at the 68 % confidence level. This constraint is primarily determined from the theoretical scale and systematical experimental uncertainties. Suggestions for reducing these uncertainties are discussed. The implications of intrinsic heavy quarks in the proton for future studies at the LHC are also discussed.
Highlights
One of the fundamental predictions of quantum chromodynamics is the existence of Fock states containing heavy quarks at large light-front (LF) momentum fraction x in the LF wavefunctions of hadrons [1,2]
The results for the ETγ spectra in the central and forward regions obtained by using CT14nnloIC parton distribution function (PDF) without the intrinsic charm (IC) contribution are presented in Fig. 1
We are unable to determine a precise value of the IC probability from recent ATLAS data
Summary
One of the fundamental predictions of quantum chromodynamics is the existence of Fock states containing heavy quarks at large light-front (LF) momentum fraction x in the LF wavefunctions of hadrons [1,2]. The xF of the produced forward heavy hadron in the pp → c reaction is equal to the sum xF = xu + xd + xc of the light-front momentum fractions of the three quarks in the five-quark Fock state. The normalization of the production cross section has sizable uncertainties, and one cannot obtain precise quantitative information on the intrinsic charm contribution to the proton charm parton distribution function (PDF) from the ISR and SELEX measurements [10,11]. Another important way to identify IC utilizes the single and double J/ψ hadroproduction at high xF as measured by the NA3 fixed
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