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Measurements of differential two-particle number and transverse momentum correlation functions in pp collisions at = 13 TeV
No full textDifferential two-particle normalized cumulants () and transverse momentum correlations () are measured as a function of the relative pseudorapidity and azimuthal angle difference of charged particle pairs in minimum bias pp collisions at = 13 TeV. The measurements use charged hadrons in the pseudorapidity region of and the transverse momentum range 0.2 2.0 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 and measured in pp collisions exhibit features qualitatively similar to those observed in p–Pb and Pb–Pb collisions. The and 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 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
Interplay of prompt and non-prompt photons in photon-triggered jet observables
No full textPrompt photons are important yet challenging to observe in relativistic heavy-ion collisions, as they are produced in the early stages and traverse almost the entire QGP medium without interaction. Experimental analyses typically employ isolation cuts, in the hope to identify prompt photons. Most theoretical studies consider only events with actual prompt photons, assuming no contribution from isolated non-prompt photons to reduce computational cost. For the first time, we present a study that compares simulation results generated using inclusive (bremsstrahlung) and prompt-photon events with multiple experimental observables for both p − p and Pb − Pb collisions at 5.02 TeV. Simulations are carried out using the multi-stage JETSCAPE framework tuned to describe the quenching of jets and hadrons. Isolated non-prompt photons are generated in hard photon bremsstrahlung, where the photon is radiated at a sufficient angle to the jet. Several photon triggered jet and jet substructure observables show significant contributions from inclusive photons, yielding an improvement in comparison with experimental data. Novel photon triggered jet substructure observables are also expected to show new structures, yet to be detected in experiment. This effort examines the significance of isolated nonprompt photons using parameters tuned for a simultaneous description of the leading hadron and jet spectrum, and thus provides an independent verification of the multistage evolution framework
Proton emission in ultraperipheral Pb-Pb collisions at =5.02 TeV
No full textThe first measurements of proton emission accompanied by neutron emission in the electromagnetic dissociation (EMD) of Pb nuclei in the ALICE experiment at the Large Hadron Collider are presented. The EMD protons and neutrons emitted at very forward rapidities are detected by the proton and neutron zero degree calorimeters of the ALICE experiment. The emission cross sections of zero, one, two, and three protons accompanied by at least one neutron were measured in ultraperipheral Pb - Pb collisions at a center-of-mass energy per nucleon pair =5.02 TeV. The 0p and 3p cross sections are described by the RELDIS model within their measurement uncertainties, while the 1p and 2p cross sections are underestimated by the model by 17–25%. According to this model, these 0p, 1p, 2p, and 3p cross sections are associated, respectively, with the production of various isotopes of Pb, Tl, Hg, and Au in the EMD of Pb. The cross sections of the emission of a single proton accompanied by the emission of one, two, or three neutrons in EMD were also measured. The data are significantly overestimated by the RELDIS model, which predicts that the (1p,1n), (1p,2n), and (1p,3n) cross sections are very similar to the cross sections for the production of the thallium isotopes TI
Exploring nuclear structure with multiparticle azimuthal correlations at the LHC
No full textThis Letter presents systematic measurements of various flow observables using charged particles from XeXe collisions at ~TeV and PbPb collisions at ~TeV recorded by the ALICE detector. Flow coefficients, flow fluctuations, nonlinear flow modes, and correlations between flow coefficients are measured as a function of centrality. Charged-particle tracks in the pseudorapidity region $|\eta
Free-Streaming Online Tracking in CBM
No full textA free-streaming track reconstruction method has been developed for the CBM experiment at GSI. As a reconstruction core, it uses the existing singleevent tracking based on the Cellular Automaton, but the approach to the freestreaming tracking is generic and can be can be used with various core algorithms without modification.The method processes free-streaming data by manipulating the data at the input and output of the tracking core, leaving the reconstruction core unchanged. Data is fed into the tracking algorithm in small portions in a special way that avoids any track merging between the portions. A novel algorithm enables reading data portions without explicit time sorting, ensuring efficient processing.The approach has been validated on simulated data at collision rates up to 10 MHz and was successfully applied online for the mCBM test setup during the March 2024 and February 2025 data-taking campaigns
