Mon·Sep 9, 2024Monday·September 9, 2024

1. 01*

   Higher-order symmetry plane correlations in Pb$-$Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV

   ALICE Collaboration

   The correlations between event-by-event fluctuations of symmetry planes are measured in Pb--Pb collisions at a centre-of-mass energy per nucleon pair $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV recorded by the ALICE detector at the Large Hadron Collider. This analysis is conducted using the Gaussian Estimator technique, which is insensitive to biases from correlations between different flow amplitudes. The study presents, for the first time, the centrality dependence of correlations involving up to five different symmetry planes. The correlation strength varies depending on the harmonic order of the symmetry plane and the collision centrality. Comparisons with measurements from lower energies indicate no significant differences within uncertainties. Additionally, the results are compared with hydrodynamic model calculations. Although the model predictions provide a qualitative explanation of the experimental results, they overestimate the data for some observables. This is particularly true for correlators that are sensitive to the non-linear response of the medium to initial-state anisotropies in the collision system. As these new correlators provide unique information -- independent of flow amplitudes -- their usage in future model developments can further constrain the properties of the strongly-interacting matter created in ultrarelativistic heavy-ion collisions.

   nucl-exhep-exPRC(2025)·10 citations
2. 02*

   Exploring nuclear structure with multiparticle azimuthal correlations at the LHC

   ALICE Collaboration

   Details of the nuclear structure of ${}^{129}$Xe, such as the quadrupole deformation and the nuclear diffuseness, are studied by extensive measurements of anisotropic-flow-related observables in Xe--Xe collisions at a centre-of-mass energy per nucleon pair $\sqrt{s_{{}_{\mathrm{NN}}}}=5.44$ TeV with the ALICE detector at the LHC. The results are compared with those from Pb--Pb collisions at $\sqrt{s_{{}_{\mathrm{NN}}}}=5.02$ TeV for a baseline, given that the ${}^{208}$Pb nucleus exhibits a very weak deformation. Furthermore, comprehensive comparisons are performed with a state-of-the-art hybrid model using IP-Glasma+MUSIC+UrQMD. It is found that among various IP-Glasma+MUSIC+UrQMD calculations with different values of nuclear parameters, the one using a nuclear diffuseness parameter of $a_0=0.492$ and a nuclear quadrupole deformation parameter of ${\beta }_2=0.207$ provides a better description of the presented flow measurements. These studies represent the first systematic exploration of nuclear structure at TeV energies, utilizing a comprehensive set of anisotropic flow observables. The measurements serve as a critical experimental benchmark for rigorously testing the interplay between nuclear structure inputs and heavy-ion theoretical models.

   nucl-exhep-exPLB(2025)·19 citations
3. 03*

   J/$\psi$-hadron correlations at midrapidity in pp collisions at $\sqrt{s}$ = 13 TeV

   ALICE Collaboration

   We report on the measurement of inclusive, non-prompt, and prompt J/$\psi$-hadron correlations by the ALICE Collaboration at the CERN Large Hadron Collider in pp collisions at a center-of-mass energy of $13\text{TeV}$. The correlations are studied at midrapidity ($|y|<0.9$) in the transverse momentum ranges $p_{\mathrm{T}}<40\text{GeV}/c$ for the J/$\psi$ and $0.15<p_{\mathrm{T}}<10\text{GeV}/c$ and $|\eta |<0.9$ for the associated hadrons. The measurement is based on minimum bias and high multiplicity data samples corresponding to integrated luminosities of $L_{\text{int}}=34{\text{nb}}^{-1}$ and $L_{\text{int}}=6.9{\text{pb}}^{-1}$, respectively. In addition, two more data samples are employed, requiring, on top of the minimum bias condition, a threshold on the tower energy of $E=4$ and $9\text{GeV}$ in the ALICE electromagnetic calorimeters, which correspond to integrated luminosities of $L_{\text{int}}=0.9{\text{pb}}^{-1}$ and $L_{\text{int}}=8.4{\text{pb}}^{-1}$, respectively. The azimuthally integrated near and away side yields of associated charged hadrons per J/$\psi$ trigger are presented as a function of the J/$\psi$ and associated hadron transverse momentum. The measurements are discussed in comparison to PYTHIA calculations.

   nucl-exhep-exJHEP(2025)·4 citations
4. 04*

   Multiplicity-dependent jet modification from di-hadron correlations in pp collisions at $\sqrt{s}=13$ TeV

   ALICE Collaboration

   Short-range correlations between charged particles are studied via two-particle angular correlations in pp collisions at $\sqrt{\text{s}}=13$~TeV. The correlation functions are measured as a function of the relative azimuthal angle $\Delta \phi$ and the pseudorapidity separation $\Delta \eta$ for pairs of primary charged particles within the pseudorapidity interval $|\eta |<0.9$ and the transverse-momentum range $1<p_{\mathrm{T}}<8$ GeV/$c$. Near-side ($|\Delta \phi |<1.3$) peak widths are extracted from a generalised Gaussian fitted over the correlations in full pseudorapidity separation ($|\Delta \eta |<1.8$), while the per-trigger associated near-side yields are extracted for the short-range correlations ($|\Delta \eta |<1.3$). Both are evaluated as a function of charged-particle multiplicity obtained by two different event activity estimators. The width of the near-side peak decreases with increasing multiplicity, and this trend is reproduced qualitatively by the Monte Carlo event generators PYTHIA 8, AMPT, and EPOS. However, the models overestimate the width in the low transverse-momentum region ($p_{\mathrm{T}}<3$ GeV/$c$). The per-trigger associated near-side yield increases with increasing multiplicity. Although this trend is also captured qualitatively by the considered event generators, the yield is mostly overestimated by the models in the considered kinematic range. The measurement of the shape and yield of the short-range correlation peak can help us understand the interplay between jet fragmentation and event activity, quantify the narrowing trend of the near-side peak as a function of transverse momentum and multiplicity selections in pp collisions, and search for final-state jet modification in small collision systems.

   nucl-exhep-exJHEP(2025)·0 citations

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.