skip to main content
US FlagAn official website of the United States government
dot gov icon
Official websites use .gov
A .gov website belongs to an official government organization in the United States.
https lock icon
Secure .gov websites use HTTPS
A lock ( lock ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.

Attention:

The NSF Public Access Repository (PAR) system and access will be unavailable from 11:00 PM ET on Friday, July 11 until 2:00 AM ET on Saturday, July 12 due to maintenance. We apologize for the inconvenience.


Search for: All records

Creators/Authors contains: "Li, X. L."

Note: When clicking on a Digital Object Identifier (DOI) number, you will be taken to an external site maintained by the publisher. Some full text articles may not yet be available without a charge during the embargo (administrative interval).
What is a DOI Number?

Some links on this page may take you to non-federal websites. Their policies may differ from this site.

  1. A<sc>bstract</sc> The azimuthal anisotropy of particles associated with jets (jet particles) at midrapidity is measured for the first time in p-Pb and Pb-Pb collisions at$$ \sqrt{{\textrm{s}}_{\textrm{NN}}} $$ s NN = 5.02 TeV down to transverse momentum (pT) of 0.5 GeV/cand 2 GeV/c, respectively, with ALICE. The results obtained in p-Pb collisions are based on a novel three-particle correlation technique. The azimuthal anisotropy coefficientv2in high-multiplicity p-Pb collisions is positive, with a significance reaching 6.8σat lowpT, and its magnitude is smaller than in semicentral Pb-Pb collisions. In contrast to the measurements in Pb-Pb collisions, thev2coefficient is also found independent ofpTwithin uncertainties. Comparisons with the inclusive charged-particlev2and with AMPT calculations are discussed. The predictions suggest that parton interactions play an important role in generating a non-zero jet-particlev2in p-Pb collisions, even though they overestimate the reported measurement. These observations shed new insights on the understanding of the origin of the collective behaviour of jet particles in small systems such as p-Pb collisions, and provide significant stringent new constraints to models. 
    more » « less
    Free, publicly-accessible full text available August 1, 2025
  2. A<sc>bstract</sc> Measurements of inclusive charged-particle jet production in pp and p-Pb collisions at center-of-mass energy per nucleon-nucleon collision$$ \sqrt{s_{\textrm{NN}}} $$ s NN = 5.02 TeV and the corresponding nuclear modification factor$$ {R}_{\textrm{pPb}}^{\textrm{ch}\ \textrm{jet}} $$ R pPb ch jet are presented, using data collected with the ALICE detector at the LHC. Jets are reconstructed in the central rapidity region |ηjet|<0.5 from charged particles using the anti-kTalgorithm with resolution parametersR= 0.2, 0.3, and 0.4. ThepT-differential inclusive production cross section of charged-particle jets, as well as the corresponding cross section ratios, are reported for pp and p-Pb collisions in the transverse momentum range 10<$$ {p}_{\textrm{T},\textrm{jet}}^{\textrm{ch}} $$ p T , jet ch <140 GeV/cand 10<$$ {p}_{\textrm{T},\textrm{jet}}^{\textrm{ch}} $$ p T , jet ch <160 GeV/c, respectively, together with the nuclear modification factor$$ {R}_{\textrm{pPb}}^{\textrm{ch}\ \textrm{jet}} $$ R pPb ch jet in the range 10<$$ {p}_{\textrm{T},\textrm{jet}}^{\textrm{ch}} $$ p T , jet ch <140 GeV/c. The analysis extends thepTrange of the previously-reported charged-particle jet measurements by the ALICE Collaboration. The nuclear modification factor is found to be consistent with one and independent of the jet resolution parameter with the improved precision of this study, indicating that the possible influence of cold nuclear matter effects on the production cross section of charged-particle jets in p-Pb collisions at$$ \sqrt{s_{\textrm{NN}}} $$ s NN = 5.02 TeV is smaller than the current precision. The obtained results are in agreement with other minimum bias jet measurements available for RHIC and LHC energies, and are well reproduced by the NLO perturbative QCD Powhegcalculations with parton shower provided by Pythia8 as well as by Jetscapesimulations. 
    more » « less
  3. Recent measurements of charm-baryon production in hadronic collisions have questioned the universality of charm-quark fragmentation across different collision systems. In this work the fragmentation of charm quarks into charm baryons is probed, by presenting the first measurement of the longitudinal jet momentum fraction carried by Λ c + baryons, z ch , in hadronic collisions. The results are obtained in proton-proton ( p p ) collisions at s = 13 TeV at the LHC, with Λ c + baryons and charged (track-based) jets reconstructed in the transverse momentum intervals of 3 p T Λ c + < 15 GeV / c and 7 p T jet ch < 15 GeV / c , respectively. The z ch distribution is compared to a measurement of D 0 -tagged charged jets in p p collisions as well as to 8 simulations. The data hints that the fragmentation of charm quarks into charm baryons is softer with respect to charm mesons, in the measured kinematic interval, as predicted by hadronization models which include color correlations beyond leading-color in the string formation. © 2024 CERN, for the ALICE Collaboration2024CERN 
    more » « less
  4. The first measurement of the cross section for incoherent photonuclear production of J / ψ vector mesons as a function of the Mandelstam | t | variable is presented. The measurement was carried out with the ALICE detector at midrapidity, | y | < 0.8 , using ultraperipheral collisions of Pb nuclei at a center-of-mass energy per nucleon pair of s NN = 5.02 TeV . This rapidity interval corresponds to a Bjorken- x range ( 0.3 1.4 ) × 10 3 . Cross sections are given in five | t | intervals in the range 0.04 < | t | < 1 GeV 2 and compared to the predictions by different models. Models that ignore quantum fluctuations of the gluon density in the colliding hadron predict a | t | dependence of the cross section much steeper than in data. The inclusion of such fluctuations in the same models provides a better description of the data. © 2024 CERN, for the ALICE Collaboration2024CERN 
    more » « less
  5. The production of the ψ ( 2 S ) charmonium state was measured with ALICE in Pb-Pb collisions at s NN = 5.02 TeV , in the dimuon decay channel. A significant signal was observed for the first time at LHC energies down to zero transverse momentum, at forward rapidity ( 2.5 < y < 4 ). The measurement of the ratio of the inclusive production cross sections of the ψ ( 2 S ) and J / ψ resonances is reported as a function of the centrality of the collisions and of transverse momentum, in the region p T < 12 GeV / c . The results are compared with the corresponding measurements in p p collisions, by forming the double ratio [ σ ψ ( 2 S ) / σ J / ψ ] Pb Pb / [ σ ψ ( 2 S ) / σ J / ψ ] p p . It is found that in Pb-Pb collisions the ψ ( 2 S ) is suppressed by a factor of 2 with respect to the J / ψ . The ψ ( 2 S ) nuclear modification factor R AA was also obtained as a function of both centrality and p T . The results show that the ψ ( 2 S ) resonance yield is strongly suppressed in Pb-Pb collisions, by a factor of up to 3 with respect to p p . Comparisons of cross section ratios with previous Super Proton Synchrotron findings by the NA50 experiment and of R AA with higher- p T results at LHC energy are also reported. These results and the corresponding comparisons with calculations of transport and statistical models address questions on the presence and properties of charmonium states in the quark-gluon plasma formed in nuclear collisions at the LHC. © 2024 CERN, for the ALICE Collaboration2024CERN 
    more » « less
  6. Abstract The interactions of kaons (K) and antikaons ($$\mathrm {\overline{K}}$$ K ¯ ) with few nucleons (N) were studied so far using kaonic atom data and measurements of kaon production and interaction yields in nuclei. Some details of the three-body KNN and$$\mathrm {\overline{K}}$$ K ¯ NN dynamics are still not well understood, mainly due to the overlap with multi-nucleon interactions in nuclei. An alternative method to probe the dynamics of three-body systems with kaons is to study the final state interaction within triplet of particles emitted in pp collisions at the Large Hadron Collider, which are free from effects due to the presence of bound nucleons. This Letter reports the first femtoscopic study of p–p–K$$^+$$ + and p–p–K$$^-$$ - correlations measured in high-multiplicity pp collisions at$$\sqrt{s}$$ s = 13 TeV by the ALICE Collaboration. The analysis shows that the measured p–p–K$$^+$$ + and p–p–K$$^-$$ - correlation functions can be interpreted in terms of pairwise interactions in the triplets, indicating that the dynamics of such systems is dominated by the two-body interactions without significant contributions from three-body effects or bound states. 
    more » « less