Azimuthal correlations within exclusive dijets with large momentum transfer in photon-lead collisions

Abstract

The structure of nucleons is multidimensional and depends on the transverse momenta, spatial geometry, and polarization of the constituent partons. Such a structure can be studied using high-energy photons produced in ultraperipheral heavy-ion collisions. The first measurement of the azimuthal angular correlations of exclusively produced events with two jets in photon-lead interactions at large momentum transfer is presented, a process that is considered to be sensitive to the underlying nuclear gluon polarization. This study uses a data sample of ultraperipheral lead-lead collisions at $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV, corresponding to an integrated luminosity of 0.38 nb${}^{-1}$, collected with the CMS experiment at the LHC. The measured second harmonic of the correlation between the sum and difference of the two jet momenta is found to be positive, and rising, as the dijet momentum increases. A well-tuned model that has been successful at describing a wide range of proton scattering data from the HERA experiments fails to describe the observed correlations, suggesting the presence of gluon polarization effects.

Replaced with the published version. Added the journal reference and the DOI. All the figures and tables, including additional supplementary figures, can be found at http://cms-results.web.cern.ch/cms-results/public-results/publications/HIN-18-011 (CMS Public Pages)

References in corpus (11)

• Particle-flow reconstruction and global event description with the CMS detector
• The CMS trigger system
• Jet energy scale and resolution in the CMS experiment in pp collisions at 8 TeV
• The Physics of Ultraperipheral Collisions at the LHC
• Forward Neutral Pion Production in p+p and d+Au Collisions at sqrt(s_NN)=200 GeV
• Imaging the nucleus with high-energy photons
• Accessing the gluon Wigner distribution in ultraperipheral $pA$ collisions
• Diffractive Dijet Production and Wigner Distributions from the Color Glass Condensate
• The elliptic gluon GTMD inside a large nucleus
• Wigner, Husimi and GTMD distributions in the Color Glass Condensate
• Broadening and saturation effects in dijet azimuthal correlations in p-p and p-Pb collisions at $\sqrt{{\mathbf{s}}_{\mathbf{NN}}}=$ 5.02 TeV

Cited by in corpus (1)

• Measurement of the impact-parameter dependent azimuthal anisotropy in coherent ${\rho }^0$ photoproduction in Pb$-$Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV