The production of isolated photons in PbPb and pp collisions at $\sqrt{s_{\mathrm{NN}}}=$ 5.02 TeV

Abstract

The transverse energy ($E_{\mathrm{T}}^{\gamma }$) spectra of photons isolated from other particles are measured using proton-proton (pp) and lead-lead (PbPb) collisions at the LHC at $\sqrt{s_{\mathrm{NN}}}=$ 5.02 TeV with integrated luminosities of 27.4 pb${}^{-1}$and 404 $\mu$b${}^{-1}$ for pp and PbPb data, respectively. The results are presented for photons with 25 $<$ $E_{\mathrm{T}}^{\gamma }$ $<$ 200 GeV in the pseudorapidity range $|\eta |$ $<$ 1.44, and for different centrality intervals for PbPb collisions. Photon production in PbPb collisions is consistent with that in pp collisions scaled by the number of binary nucleon-nucleon collisions, demonstrating that photons do not interact with the quark-gluon plasma. Therefore, isolated photons can provide information about the initial energy of the associated parton in photon+jet measurements. The results are compared with predictions from the next-to-leading-order JETPHOX generator for different parton distribution functions (PDFs) and nuclear PDFs (nPDFs). The comparisons can help to constrain the nPDFs global fits.

Replaced with the published version. Added the journal reference and the DOI. All the figures and tables can be found at http://cms-results.web.cern.ch/cms-results/public-results/publications/HIN-18-016 (CMS Public Pages)

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Cited by in corpus (8)

• The ALICE experiment: a journey through QCD
• Overview of high-density QCD studies with the CMS experiment at the LHC
• Strong constraints on jet quenching in centrality-dependent $p$+Pb collisions at 5.02 TeV from ATLAS
• $\gamma$-hadron spectra in p + Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV
• Flavor and path-length dependence of jet quenching from inclusive jet and γ-jet suppression
• Evidence of medium response to hard probes using correlations of Z bosons with hadrons in heavy ion collisions
• Hard processes in multi-TeV ion collisions
• Measurement of the inclusive isolated-photon production cross section in pp and Pb$-$Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV