Attention:The NSF Public Access Repository (PAR) system and access will be unavailable from 5:00 PM ET until 8:00 PM ET on Friday, September 11 due to maintenance. We apologize for the inconvenience.


Title: Azimuthal correlations of heavy-flavor hadron decay electrons with charged particles in pp and p–Pb collisions at $$\pmb {\sqrt{s_{\mathrm{{NN}}}}}$$ = 5.02 TeV
Abstract The azimuthal ($$\Delta \varphi $$ Δφ ) correlation distributions between heavy-flavor decay electrons and associated charged particles are measured in pp and p–Pb collisions at$$\sqrt{s_{\mathrm{{NN}}}} = 5.02$$ sNN =5.02 TeV. Results are reported for electrons with transverse momentum$$4 4<pT<16 $$\textrm{GeV}/c$$ GeV/c  and pseudorapidity$$|\eta |<0.6$$ |η|<0.6 . The associated charged particles are selected with transverse momentum$$1 1<pT<7 $$\textrm{GeV}/c$$ GeV/c , and relative pseudorapidity separation with the leading electron$$|\Delta \eta | < 1$$ |Δη|<1 . The correlation measurements are performed to study and characterize the fragmentation and hadronization of heavy quarks. The correlation structures are fitted with a constant and two von Mises functions to obtain the baseline and the near- and away-side peaks, respectively. The results from p–Pb collisions are compared with those from pp collisions to study the effects of cold nuclear matter. In the measured trigger electron and associated particle kinematic regions, the two collision systems give consistent results. The$$\Delta \varphi $$ Δφ distribution and the peak observables in pp and p–Pb collisions are compared with calculations from various Monte Carlo event generators.  more » « less
Award ID(s):
1719759 2208883 2012154
PAR ID:
10487454
Author(s) / Creator(s):
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; more » ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; « less
Corporate Creator(s):
Publisher / Repository:
Springer
Date Published:
Journal Name:
The European Physical Journal C
Volume:
83
Issue:
8
ISSN:
1434-6052
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. Abstract Differential two-particle normalized cumulants ($$R_2$$ R2 ) and transverse momentum correlations ($$P_2$$ P2 ) are measured as a function of the relative pseudorapidity and azimuthal angle difference$$( \Delta \eta , \Delta \varphi )$$ (Δη,Δφ) of charged particle pairs in minimum bias pp collisions at$$\sqrt{\textit{s}}$$ s = 13 TeV. The measurements use charged hadrons in the pseudorapidity region of$$|\eta | < 0.8$$ |η|<0.8 and the transverse momentum range 0.2$$< \textit{p}_{\mathrm T} < $$ <pT< 2.0$$\textrm{GeV}/\textit{c}$$ GeV/c in order to focus on soft multiparticle interactions and to complement prior measurements of these correlation functions in p–Pb and Pb–Pb collisions. The correlation functions are reported for both unlike-sign and like-sign pairs and their charge-independent and charge-dependent combinations. Both the$$R_2$$ R2 and$$P_2$$ P2 measured in pp collisions exhibit features qualitatively similar to those observed in p–Pb and Pb–Pb collisions. The$$\Delta \eta $$ Δη and$$\Delta \varphi $$ Δφ root mean square widths of the near-side peak of the correlation functions are evaluated and compared with those observed in p–Pb and Pb–Pb collisions and show smooth evolution with the multiplicity of charged particles produced in the collision. The comparison of the measured correlation functions with predictions from PYTHIA8 shows that this model qualitatively captures their basic structure and characteristics but feature important differences. In addition, the$$R_2^{\textrm{CD}}$$ R2CD is used to determine the charge balance function of hadrons produced within the detector acceptance of the measurements. The integral of the balance function is found to be compatible with those reported by a previous measurement in Pb–Pb collisions. 
    more » « less
  2. Abstract The azimuthal-correlation distributions between electrons from the decays of heavy-flavor hadrons and associated charged particles in Pb–Pb collisions at$$\sqrt{s_{\textrm{NN}}} = 5.02$$ sNN =5.02 TeV are reported for the 0–10% and 30–50% centrality classes. This measurement provides access to the jet-like correlation observables in the heavy-flavor sector in Pb–Pb collisions. The analysis is performed for trigger electrons from heavy-flavor hadron decays with transverse momentum$$4< p_\textrm{T}^\textrm{e} < 16~\textrm{GeV}/c$$ 4<pTe<16GeV/c , considering associated particles within the transverse-momentum range$$1< p_\textrm{T}^\textrm{assoc} < 7$$ 1<pTassoc<7 $$\textrm{GeV}/c$$ GeV/c , and a pseudorapidity difference of$$|\Delta \eta |<1$$ |Δη|<1 between the trigger electron and associated particles. The per-trigger nuclear modification factor ($$I_\textrm{AA}$$ IAA ) is calculated to compare the near- and away-side peak yields to those in pp collisions at$$\sqrt{s} = 5.02$$ s=5.02 TeV. In 0–10% central collisions, the$$I_\textrm{AA}$$ IAA indicates a hint of enhancement of associated-particle yields with$$p_\textrm{T}<3$$ pT<3 GeV/con the near side, and a suppression of yields with$$p_\textrm{T}>4$$ pT>4 GeV/con the away side. The$$I_\textrm{AA}$$ IAA for electron triggers from heavy-flavor hadron decays is compared with that for light-flavor and strange-particle triggers to investigate the dependence on different fragmentation processes and parton-medium dynamics, and is found to be the same within uncertainties. 
    more » « less
  3. Abstract Event-by-event fluctuations of the event-wise mean transverse momentum,$$\langle p_{\textrm{T}}\rangle $$ pT , of charged particles produced in proton–proton (pp) collisions at$$\sqrt{s}$$ s = 5.02 TeV, Xe–Xe collisions at$$\sqrt{s_{\textrm{NN}}}$$ sNN = 5.44 TeV, and Pb–Pb collisions at$$\sqrt{s_{\textrm{NN}}}$$ sNN = 5.02 TeV are studied using the ALICE detector based on the integral correlator$$\langle \!\langle \Delta p_\textrm{T}\Delta p_\textrm{T}\rangle \!\rangle $$ ΔpTΔpT . The correlator strength is found to decrease monotonically with increasing produced charged-particle multiplicity measured at midrapidity in all three systems. In Xe–Xe and Pb–Pb collisions, the multiplicity dependence of the correlator deviates significantly from a simple power-law scaling as well as from the predictions of the HIJING and AMPT models. The observed deviation from power-law scaling is expected from transverse radial flow in semicentral to central Xe–Xe and Pb–Pb collisions. In pp collisions, the correlation strength is also studied by classifying the events based on the transverse spherocity,$$S_0$$ S0 , of the particle production at midrapidity, used as a proxy for the presence of a pronounced back-to-back jet topology. Low-spherocity (jetty) events feature a larger correlation strength than those with high spherocity (isotropic). The strength and multiplicity dependence of jetty and isotropic events are well reproduced by calculations with the PYTHIA 8 and EPOS LHC models. 
    more » « less
  4. Abstract This paper presents the measurement of the isolated prompt photon inclusive production cross section in pp and p–Pb collisions by the ALICE Collaboration at the LHC. The measurement is performed in p–Pb collisions at centre-of-mass energies per nucleon pair of$$\sqrt{s_{\text {NN}}}={5.02}\,\textrm{TeV}$$ sNN =5.02TeV and 8.16 TeV, as well as in pp collisions at$$\sqrt{s}={5.02}\,\textrm{TeV}$$ s=5.02TeV and 8 TeV. The cross section is obtained at midrapidity$$(|y|<0.7)$$ (|y|<0.7) using a charged-track based isolation momentum$$p_\textrm{T}^{\text {iso,~ch}}<{1.5}\,\textrm{GeV}/c$$ pTiso, ch <1.5GeV/c in a cone with radius$$R=0.4$$ R=0.4 . The data for both collision systems are well reproduced by perturbative QCD (pQCD) calculations at next-to-leading order (NLO) using recent parton distribution functions for free (PDF) and bound (nPDF) nucleons. Furthermore, the nuclear modification factor$$R_{\text {pA}}$$ RpA for both collision energies is consistent with unity for$$p_{\textrm{T}}$$ pT $$>{20}\,\textrm{GeV}/c$$ >20GeV/c . However, deviations from unity ($$R_\textrm{pA}<1$$ RpA<1 ) of up to 20% are observed for$$p_{\textrm{T}}$$ pT $$<{20}\,\textrm{GeV}/c$$ <20GeV/c with limited significance, indicating the possible presence of nuclear effects in the initial state of the collision. The suppression increases with decreasing$$p_{\textrm{T}}$$ pT with a significance of$$2.3\upsigma $$ 2.3σ for a non-zero slope and yields$$R_{\textrm{pA}}<1$$ RpA<1 with a significance of$$1.8\upsigma $$ 1.8σ at$$\sqrt{s_{\textrm{NN}}}={8.16}\,\textrm{TeV}$$ sNN =8.16TeV for$$p_{\textrm{T}}$$ pT $$<{20}\,\textrm{GeV}/c$$ <20GeV/c . In addition, a significance of$$1.1\upsigma $$ 1.1σ is observed for$$R_{\textrm{pA}}<1$$ RpA<1 at the lower collision energy$$\sqrt{s_{\textrm{NN}}}={5.02}\,\textrm{TeV}$$ sNN =5.02TeV for$$p_{\textrm{T}} < {14}\,\textrm{GeV}/c$$ pT<14GeV/c . The magnitude and shape of the suppression are consistent with pQCD predictions at NLO using nPDFs that incorporate nuclear shadowing effects in the Pb nucleus. 
    more » « less
  5. Abstract The ALICE Collaboration at the CERN LHC has measured the inclusive production cross section of isolated photons at midrapidity as a function of the photon transverse momentum ($$p_{\textrm{T}}^{\gamma }$$ pTγ ), in Pb–Pb collisions in different centrality intervals, and in pp collisions, at centre-of-momentum energy per nucleon pair of$$\sqrt{s_{\textrm{NN}}}~=~5.02$$ sNN =5.02  TeV. The photon transverse momentum range is between 10–14 and 40–140 GeV/$$c$$ c , depending on the collision system and on the Pb–Pb centrality class. The result extends to lower$$p_{\textrm{T}}^{\gamma }$$ pTγ than previously published results by the ATLAS and CMS experiments at the same collision energy. The covered pseudorapidity range is$$|\eta ^{\gamma } | <0.67$$ |ηγ|<0.67 . The isolation selection is based on a charged particle isolation momentum threshold$$p_{\textrm{T}}^\mathrm{iso,~ch} = 1.5$$ pT iso,ch =1.5  GeV/$$c$$ c within a cone of radii$$R=0.2$$ R=0.2 and 0.4. The nuclear modification factor is calculated and found to be consistent with unity in all centrality classes, and also consistent with the HG-PYTHIA model, which describes the event selection and geometry biases that affect the centrality determination in peripheral Pb–Pb collisions. The measurement is compared to next-to-leading order perturbative QCD calculations and to the measurements of isolated photons and Z$$^{0}$$ 0 bosons from the CMS experiment, which are all found to be in agreement. 
    more » « less