The first measurement of the dijet transverse momentum balance xj in proton-lead (pPb) collisions at a nucleon-nucleon center-of-mass energy of = 8.16 TeV is presented. The xj observable, defined as the ratio of the subleading over leading jet transverse momentum in a dijet pair, is used to search for jet quenching effects. The data, corresponding to an integrated luminosity of 174.6 nb−1, were collected with the CMS detector in 2016. The xj distributions and their average values are studied as functions of the charged-particle multiplicity of the events and for various dijet rapidity selections. The latter enables probing hard scattering of partons carrying distinct nucleon momentum fractions x in the proton- and lead-going directions. The former, aided by the high-multiplicity triggers, allows probing for potential jet quenching effects in high-multiplicity events (with up to 400 charged particles), for which collective phenomena consistent with quark-gluon plasma (QGP) droplet formation were previously observed. The ratios of xj distributions for high- to low-multiplicity events are used to quantify the possible medium effects. These ratios are consistent with simulations of the hard-scattering process that do not include QGP production. These measurements set an upper limit on medium-induced energy loss of the subleading jet of 1.26% of its transverse momentum at the 90% confidence level in high multiplicity pPb events.
Search for jet quenching with dijets from high-multiplicity pPb collisions at √sNN = 8.16 TeV
Cappati, A.;Tornago, M.;Amapane, N.;Argiro, S.;Bellan, R.;Borca, C.;Costa, M.;Cotto, G.;Covarelli, R.;Grippo, M.;Kiani, B.;Luongo, F.;Markovic, L.;Mecca, A.;Menzio, L.;Meridiani, P.;Migliore, E.;Mulargia, R.;Obertino, M. M.;Pacher, L.;Siviero, F.;Sola, V.;Solano, A.;Tarricone, C.;Umoret, G.;Bellora, A.;Salvatico, R.;Shchelina, K.;Rumerio, P.;Ravera, F.;Vagnerini, A.;
2025-01-01
Abstract
The first measurement of the dijet transverse momentum balance xj in proton-lead (pPb) collisions at a nucleon-nucleon center-of-mass energy of = 8.16 TeV is presented. The xj observable, defined as the ratio of the subleading over leading jet transverse momentum in a dijet pair, is used to search for jet quenching effects. The data, corresponding to an integrated luminosity of 174.6 nb−1, were collected with the CMS detector in 2016. The xj distributions and their average values are studied as functions of the charged-particle multiplicity of the events and for various dijet rapidity selections. The latter enables probing hard scattering of partons carrying distinct nucleon momentum fractions x in the proton- and lead-going directions. The former, aided by the high-multiplicity triggers, allows probing for potential jet quenching effects in high-multiplicity events (with up to 400 charged particles), for which collective phenomena consistent with quark-gluon plasma (QGP) droplet formation were previously observed. The ratios of xj distributions for high- to low-multiplicity events are used to quantify the possible medium effects. These ratios are consistent with simulations of the hard-scattering process that do not include QGP production. These measurements set an upper limit on medium-induced energy loss of the subleading jet of 1.26% of its transverse momentum at the 90% confidence level in high multiplicity pPb events.| File | Dimensione | Formato | |
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JHEP07(2025)118.pdf
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