Search for jet quenching effects in high-multiplicity pp collisions at $\sqrt{s}$ = 13 TeV via di-jet acoplanarity

Abstract

The ALICE Collaboration reports a search for jet quenching effects in high-multiplicity (HM) proton$-$proton collisions at $\sqrt{s}$ = 13 TeV, using the semi-inclusive azimuthal-difference distribution $\Delta \phi$ of charged-particle jets recoiling from a high transverse momentum (high-$p_{\mathrm{T},\mathrm{trig}}$) trigger hadron. Jet quenching may broaden the $\Delta \phi$ distribution measured in HM events compared to that in minimum bias (MB) events. The measurement employs a $p_{\mathrm{T},\mathrm{trig}}$-differential observable for data-driven suppression of the contribution of multiple partonic interactions, which is the dominant background. While azimuthal broadening is indeed observed in HM compared to MB events, similar broadening for HM events is observed for simulations based on the PYTHIA 8 Monte Carlo generator, which does not incorporate jet quenching. Detailed analysis of these data and simulations show that the azimuthal broadening is due to bias of the HM selection towards events with multiple jets in the final state. The identification of this bias has implications for all jet quenching searches where selection is made on the event activity.

27 pages, 6 captioned figures, 2 tables, authors from page 21, published version, figures at http://alice-publications.web.cern.ch/node/9593

References in corpus (9)

• Matching NLO QCD computations with Parton Shower simulations: the POWHEG method
• Glauber Modeling in High Energy Nuclear Collisions
• Tuning PYTHIA 8.1: the Monash 2013 Tune
• Pileup subtraction using jet areas
• The Catchment Area of Jets
• The theory and phenomenology of perturbative QCD based jet quenching
• Soft Gluon Resummations in Dijet Azimuthal Angular Correlations at the Collider
• Collectivity from interference
• Next-to-leading order QCD corrections to hadron+jet production in pp collisions at RHIC

Cited by in corpus (7)

• Properties of the QCD Matter: A Review of Selected Results from the ALICE Experiment
• Selection bias effects on high-$p_{\mathrm{T}}$ yield and correlation measurements in Oxygen+Oxygen collisions
• Probing strangeness with event topology classifiers in pp collisions at energies available at the CERN Large Hadron Collider with the rope hadronization mechanism in PYTHIA
• Particle production as a function of charged-particle flattenicity in pp collisions at $\sqrt{s}$ = 13 TeV
• Thermodynamical string fragmentation and string density effects in jets
• Investigating the most active pp collisions (top 0.1%) using the tools developed by experiments at the LHC
• Topological production of charmonia with event-shape engineering in $pp$ collisions at $\sqrt{s}=13$ TeV using PYTHIA8