Centrality and rapidity dependence of inclusive jet production in √sNN=5.02 TeV proton-lead collisions with the ATLAS detector

Measurements of the centrality and rapidity dependence of inclusive jet production in √sNN=5.02 TeV proton-lead (p+Pb) collisions and the jet cross-section in √s=2.76 TeV proton-proton collisions are presented. These quantities are measured in datasets corresponding to an integrated luminosity of 27.8 nb-1 and 4.0 pb-1, respectively, recorded with the ATLAS detector at the Large Hadron Collider in 2013. The p+Pb collision centrality was characterised using the total transverse energy measured in the pseudorapidity interval -4.9 < η < -3.2 in the direction of the lead beam. Results are presented for the double-differential per-collision yields as a function of jet rapidity and transverse momentum (pT) for minimum-bias and centrality-selected p+Pb collisions, and are compared to the jet rate from the geometric expectation. The total jet yield in minimum-bias events is slightly enhanced above the expectation in a pT-dependent manner but is consistent with the expectation within uncertainties. The ratios of jet spectra from different centrality selections show a strong modification of jet production at all pT at forward rapidities and for large pT at mid-rapidity, which manifests as a suppression of the jet yield in central events and an enhancement in peripheral events. These effects imply that the factorisation between hard and soft processes is violated at an unexpected level in proton-nucleus collisions. Furthermore, the modifications at forward rapidities are found to be a function of the total jet energy only, implying that the violations may have a simple dependence on the hard parton-parton kinematicsWe thank CERN for the very successful operation of the LHC,
as well as the support staff from our institutions without whom
ATLAS could not be operated efficiently.
We acknowledge the support of ANPCyT, Argentina; YerPhI,
Armenia; ARC, Australia; BMWFW and FWF, Austria; ANAS, Azerbaijan;
SSTC, Belarus; CNPq and FAPESP, Brazil; NSERC, NRC
and CFI, Canada; CERN; CONICYT, Chile; CAS, MOST and NSFC,
China; COLCIENCIAS, Colombia; MSMT CR, MPO CR and VSC CR,
Czech Republic; DNRF, DNSRC and Lundbeck Foundation, Denmark;
EPLANET, ERC and NSRF, European Union; IN2P3-CNRS,
CEA-DSM/IRFU, France; GNSF, Georgia; BMBF, DFG, HGF, MPG and
AvH Foundation, Germany; GSRT and NSRF, Greece; ISF, MINERVA,
GIF, I-CORE and Benoziyo Center, Israel; INFN, Italy; MEXT and
JSPS, Japan; CNRST, Morocco; FOM and NWO, Netherlands; BRF
and RCN, Norway; MNiSW and NCN, Poland; GRICES and FCT,
Portugal; MNE/IFA, Romania; MES of Russia and ROSATOM, Russian
Federation; JINR; MSTD, Serbia; MSSR, Slovakia; ARRS and
MIZŠ, Slovenia; DST/NRF, South Africa; MINECO, Spain; SRC and
Wallenberg Foundation, Sweden; SER, SNSF and Cantons of Bern
and Geneva, Switzerland; NSC, Taiwan; TAEK, Turkey; STFC, the Royal Society and Leverhulme Trust, United Kingdom; DOE and
NSF, United States of America.
The crucial computing support from all WLCG partners is acknowledged
gratefully, in particular from CERN and the ATLAS
Tier-1 facilities at TRIUMF (Canada), NDGF (Denmark, Norway,
Sweden), CC-IN2P3 (France), KIT/GridKA (Germany), INFN-CNAF
(Italy), NL-T1 (Netherlands), PIC (Spain), ASGC (Taiwan), RAL (UK)
and BNL (USA) and in the Tier-2 facilities worldwid