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We compute the cross section of inclusive dijet photoproduction in ultraperipheral Pb-Pb collisions at the CERN Large Hadron Collider using next-to-leading order perturbative QCD. We demonstrate that our theoretical calculations provide a good description of various kinematic distributions measured by the ATLAS Collaboration. We find that the calculated dijet photoproduction cross section is sensitive to nuclear modifications of parton distribution functions (PDFs) at the level of 10% to 20%. Hence, this process can be used to reduce uncertainties in the determination of these nuclear PDFs, whose current magnitude is comparable to the size of the calculated nuclear modifications of the dijet photoproduction cross section.

Ultraperipheral collisions (UPCs) of relativistic ions correspond to large impact parameters between the nuclei exceeding the sum of their radii, so that short-range strong interactions between the ions are suppressed and reactions proceed rather via the emission of quasireal photons by the colliding ions. Thus, UPCs allow one to study photon-photon and photon-hadron (proton, nucleus) interactions at high energies

Focusing on UPC studies of nuclear structure in QCD at the LHC, coherent

The program of UPC measurements continues with Run 2 at the LHC, where besides photoproduction of vector mesons, inclusive dijet photoproduction in Pb-Pb UPCs

In this work, we make predictions for the cross section of inclusive dijet photoproduction in Pb-Pb UPCs at the LHC using NLO perturbative QCD

The remainder of this paper is structured as follows. In Sec.

Typical leading-order (LO) Feynman diagrams for dijet photoproduction in UPCs of nuclei

Typical leading-order Feynman graphs for dijet photoproduction in UPCs of hadrons

Using the Weizsäcker-Williams method, which allows one to treat the electromagnetic field of an ultrarelativistic ion as a flux of equivalent quasireal photons

In our analysis, we used the following input for Eq.

The NLO calculation of the dijet photoproduction cross section using Eq.

The main goal of the present paper is the first NLO QCD calculation of the cross section of inclusive dijet photoproduction in Pb-Pb UPCs and concluding whether it can describe the results of the ATLAS measurement

the anti-

the leading jet has

all jets have rapidities

the combined mass of all reconstructed jets is

the parton momentum fraction on the photon side

the parton momentum fraction on the nucleus side

The ATLAS results are presented as distributions in terms of the total jet transverse momentum

Figures

NLO QCD predictions for the cross section of dijet photoproduction in Pb-Pb UPCs at

NLO QCD predictions for the cross section of dijet photoproduction in Pb-Pb UPCs at

NLO QCD predictions for the cross section of dijet photoproduction in Pb-Pb UPCs at

NLO QCD predictions for the cross section of dijet photoproduction in Pb-Pb UPCs at

A comparison of our results shown in Figs.

To assess the impact of measurements of the inclusive dijet photoproduction cross section on nPDFs, we focus on the

NLO QCD predictions for the ratio of the cross section of dijet photoproduction to that calculated in IA in Pb-Pb UPCs at

NLO QCD predictions for the cross section of dijet photoproduction in Pb-Pb UPCs at

Note that in spite of large values of the resolution scale probed in the considered kinematics,

In Fig.

The middle panel of Fig.

Note that in the future and if/when experimental data become available, to study nuclear modifications of nPDFs one can directly form the ratio of dijet cross sections measured in Pb-Pb and proton-proton (

Finally, the bottom panel of Fig.

In our calculations, following the standard prescription for setting the hard scale in QCD calculations, we used

In this work, we used the framework of collinear factorization and NLO perturbative QCD to examine the sensitivity of the dijet photoproduction cross section to nuclear modifications of PDFs. Alternatively, one can use this process to look for signs of the Balitsky-Fadin-Kuraev-Lipatov and gluon saturation dynamics in the high-energy (

In this work, we calculated the cross section of inclusive dijet photoproduction in Pb-Pb UPCs at the LHC using NLO perturbative QCD and nCTEQ15 nPDFs. We showed that our approach provides a good description of various cross section distributions measured by the ATLAS Collaboration. We found that the calculated dijet photoproduction cross section is sensitive to nuclear modifications of the PDFs. In particular, as a function of the nucleus momentum fraction

V.G. would like to thank A. Angerami, I. Helenius, K. Kovarik, H. Paukkunen, and M. Strikman for useful discussions and the Institut für Theoretische Physik, Westfälische Wilhelms-Universität Münster for hospitality. V.G.'s research is supported in part by RFBR, research Project No. 17-52-12070. The authors gratefully acknowledge financial support of DFG through the Grant No. KL 1266/9-1 within the framework of the joint German-Russian project “New constraints on nuclear parton distribution functions at small