In:
Journal of High Energy Physics, Springer Science and Business Media LLC, Vol. 2024, No. 1 ( 2024-01-11)
Abstract:
Measurements of charged-particle production in pp, p–Pb, and Pb–Pb collisions in the toward, away, and transverse regions with the ALICE detector are discussed. These regions are defined event-by-event relative to the azimuthal direction of the charged trigger particle, which is the reconstructed particle with the largest transverse momentum $$ \left({p}_{\textrm{T}}^{\textrm{trig}}\right) $$ p T trig in the range 8 〈 $$ {p}_{\textrm{T}}^{\textrm{trig}} $$ p T trig 〈 15 GeV /c . The toward and away regions contain the primary and recoil jets, respectively; both regions are accompanied by the underlying event (UE). In contrast, the transverse region perpendicular to the direction of the trigger particle is dominated by the so-called UE dynamics, and includes also contributions from initial- and final-state radiation. The relative transverse activity classifier, $$ {R}_{\textrm{T}}={N}_{\textrm{ch}}^{\textrm{T}}/\left\langle {N}_{\textrm{ch}}^{\textrm{T}}\right\rangle $$ R T = N ch T / N ch T , is used to group events according to their UE activity, where $$ {N}_{\textrm{ch}}^{\textrm{T}} $$ N ch T is the charged-particle multiplicity per event in the transverse region and $$ \left\langle {N}_{\textrm{ch}}^{\textrm{T}}\right\rangle $$ N ch T is the mean value over the whole analysed sample. The energy dependence of the R T distributions in pp collisions at $$ \sqrt{s} $$ s = 2 . 76, 5.02, 7, and 13 TeV is reported, exploring the Koba-Nielsen-Olesen (KNO) scaling properties of the multiplicity distributions. The first measurements of charged-particle p T spectra as a function of R T in the three azimuthal regions in pp, p–Pb, and Pb–Pb collisions at $$ \sqrt{s_{\textrm{NN}}} $$ s NN = 5 . 02 TeV are also reported. Data are compared with predictions obtained from the event generators PYTHIA 8 and EPOS LHC. This set of measurements is expected to contribute to the understanding of the origin of collective-like effects in small collision systems (pp and p–Pb).
Type of Medium:
Online Resource
ISSN:
1029-8479
DOI:
10.1007/JHEP01(2024)056
Language:
English
Publisher:
Springer Science and Business Media LLC
Publication Date:
2024
detail.hit.zdb_id:
2027350-2
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