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Systematic optimization of resonance parameters in a transport approach
No full textThis study optimizes resonance parameters responsible for strangeness production in the SMASH (Simulating Many Accelerated Strongly-interacting Hadrons) transport model using a genetic algorithm. By fitting resonance parameters to experimental data on exclusive strangeness cross sections at low energies, we significantly improve the model's accuracy, notably in pion-proton interactions. Our approach explores how machine-learning tools can be used for precise resonance tuning in transport approaches
Medium-induced modification of groomed and ungroomed jet mass and angularities in Pb-Pb collisions at TeV
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Study of and its higher moments, and extraction of the speed of sound in Pb-Pb collisions with ALICE
No full textUltrarelativistic heavy-ion collisions produce a state of hot and dense strongly interacting QCD matter called quark-gluon plasma (QGP). On an event-by-event basis, the volume of the QGP in ultracentral collisions is mostly constant, while its total entropy can vary significantly due to quantum fluctuations, leading to variations in the temperature of the system. Exploiting this unique feature of ultracentral collisions allows for the interpretation of the correlation of the mean transverse momentum of produced charged hadrons and the number of charged hadrons as a measure for the speed of sound, c. This speed is related to the rate at which compression waves travel in the QGP and is determined by fitting the relative increase in with respect to the relative change in the average charged-particle density measured at mid-rapidity. This study reports the event-average of charged particles as well as the variance, skewness, and kurtosis of the event-by-event transverse momentum per charged particle distribution in ultracentral Pb-Pb collisions at a center-of-mass energy of 5.02 TeV per nucleon pair using the ALICE detector. Different centrality estimators based on charged-particle multiplicity or the transverse energy of the event are used to select ultracentral collisions. By ensuring a pseudorapidity gap between the region used to define the centrality and the region used to perform the measurement, the influence of biases and their potential effects on the rise of the mean transverse momentum is tested. The measured is found to strongly depend on the exploited centrality estimator and ranges between 0.1146±0.0028 (stat.)±0.0065 (syst.) and 0.4374±0.0006 (stat.)±0.0184 (syst.) in natural units. The self-normalized variance shows a steep decrease towards ultracentral collisions, while the self-normalized skewness variables show a maximum, followed by a fast decrease. These non-Gaussian features are understood in terms of the vanishing of the impact-parameter fluctuations contributing to the event-to-event [p] distribution
Measurement of meson production in pp and p-Pb collisions at TeV
No full textWe present the measurement of the -differential production cross section of mesons in pp and p--Pb collisions at TeV at midrapidity by ALICE. In addition, the first measurement of the nuclear modification factor for mesons at LHC energies is presented, complementing the existing measurements of lighter neutral mesons such as the and . Within the measured -range, the of mesons shows no cold nuclear matter effects within the uncertainties, consistent with previous measurements at lower energies. The ratio is presented for both collision systems, showing no collision system dependence within the uncertainties. The comparison to previously published ratios at lower and higher collision energies in pp collisions suggests a decreasing trend of the ratio above = 4GeV/ with increasing collision energy. The data in both collision systems are compared to predictions from PYTHIA 8, EPOS LHC and DPMJET event generators, revealing significant shortcomings in these models' ability to describe the production of mesons
Clues on the (supernovae or non-supernovae) Origins of the Elements from Galactic Archeology
No full textLow-metallicity stars are witnesses of the first stellar nucleosynthesis events in the Galaxy, as their surface abundances reflect the composition of the interstellar medium from which they were born. Aside from the primordial Big Bang nucleosynthesis, massive stars, due to their short lifetimes, dominate the wind and explosive ejecta into the interstellar medium of the early Galaxy. Most of them will end as core-collapse supernova (CCSN) explosions, and typical abundance patterns reflect their influence. Essentially all CCSNe eject Fe (decaying from radioactive 56Ni). Therefore, it is interesting to test whether other elements found in low-metallicity stars are correlated with Fe, i.e. whether they have been co-produced in the contributing sources or require either different or additional astrophysical origins. We concentrate in our analysis on stars with [Fe/H
High-throughput data distribution for online computing in the CBM Experiment
No full text(EDP Sciences)The CBM experiment, a fixed-target heavy-ion experiment at the upcoming GSI/FAIR SIS100 facility, aims to investigate QCD at high baryon densities. The CBM First-level Event Selector (FLES) serves as the central event selection system of the experiment. It functions as a high-performance computer cluster tasked with the online analysis of physics data, including full event reconstruction, at an incoming data rate of up to 1 TB/s. The CBM detector systems operate in a free-running and self-triggered manner, delivering time-stamped data streams. Without inherent event separation, timeslice building replaces global event building. The FLES online data distribution integrates data from around 5000 input links into self-contained, overlapping processing intervals and distributes these to the compute nodes. Using a combination of RDMA and zero-copy techniques, timeslices can be built efficiently over a high-throughput InfiniBand network and distributed to available online computing resources for full online event reconstruction and analysis in a heterogeneous HPC cluster system. A new IPC online interface to timeslice data utilizes Posix shared memory governed by a referencecounting item distributor. This design combines maximum performance and flexibility with minimum memory consumption. These developments have been successfully field-tested in production at the CBM predecessor experiment mCBM at the GSI/FAIR SIS18
