HAL Mines Nantes
Not a member yet
7271 research outputs found
Sort by
Prospects for combined analyses of hadronic emission from -ray sources in the Milky Way with CTA and KM3NeT
No full textInternational audienceThe Cherenkov Telescope Array and the KM3NeT neutrino telescopes are major upcoming facilities in the fields of -ray and neutrino astronomy, respectively. Possible simultaneous production of rays and neutrinos in astrophysical accelerators of cosmic-ray nuclei motivates a combination of their data. We assess the potential of a combined analysis of CTA and KM3NeT data to determine the contribution of hadronic emission processes in known Galactic -ray emitters, comparing this result to the cases of two separate analyses. In doing so, we demonstrate the capability of Gammapy, an open-source software package for the analysis of -ray data, to also process data from neutrino telescopes. For a selection of prototypical -ray sources within our Galaxy, we obtain models for primary proton and electron spectra in the hadronic and leptonic emission scenario, respectively, by fitting published -ray spectra. Using these models and instrument response functions for both detectors, we employ the Gammapy package to generate pseudo data sets, where we assume 200 hours of CTA observations and 10 years of KM3NeT detector operation. We then apply a three-dimensional binned likelihood analysis to these data sets, separately for each instrument and jointly for both. We find that the largest benefit of the combined analysis lies in the possibility of a consistent modelling of the -ray and neutrino emission. Assuming a purely leptonic scenario as input, we obtain, for the most favourable source, an average expected 68% credible interval that constrains the contribution of hadronic processes to the observed -ray emission to below 15%
Measurements of long-range two-particle correlation over a wide pseudorapidity range in pPb collisions at TeV
No full textInternational audienceCorrelations in azimuthal angle extending over a long range in pseudorapidity between particles, usually called the "ridge" phenomenon, were discovered in heavy-ion collisions, and later found in pp and pPb collisions. In large systems, they are thought to arise from the expansion (collective flow) of the produced particles. Extending these measurements over a wider range in pseudorapidity and final-state particle multiplicity is important to understand better the origin of these long-range correlations in small-collision systems. In this Letter, measurements of the long-range correlations in pPb collisions at TeV are extended to a pseudorapidity gap of between particles using the ALICE, forward multiplicity detectors. After suppressing non-flow correlations, e.g., from jet and resonance decays, the ridge structure is observed to persist up to a very large gap of for the first time in pPb collisions. This shows that the collective flow-like correlations extend over an extensive pseudorapidity range also in small-collision systems such as pPb collisions. The pseudorapidity dependence of the second-order anisotropic flow coefficient, v2(η), is extracted from the long-range correlations. The results are presented for a wide pseudorapidity range of in various centrality classes in pPb collisions. To gain a comprehensive understanding of the source of anisotropic flow in small-collision systems, the measurements are compared to hydrodynamic and transport model calculations. The comparison suggests that the final-state interactions play a dominant role in developing the anisotropic flow in small-collision systems
EUSO-SPB1 mission and science
No full textInternational audienceThe Extreme Universe Space Observatory on a Super Pressure Balloon 1 (EUSO-SPB1) was launched in 2017 April from Wanaka, New Zealand. The plan of this mission of opportunity on a NASA super pressure balloon test flight was to circle the southern hemisphere. The primary scientific goal was to make the first observations of ultra-high-energy cosmic-ray extensive air showers (EASs) by looking down on the atmosphere with an ultraviolet (UV) fluorescence telescope from suborbital altitude (33 km). After 12 days and 4 h aloft, the flight was terminated prematurely in the Pacific Ocean. Before the flight, the instrument was tested extensively in the West Desert of Utah, USA, with UV point sources and lasers. The test results indicated that the instrument had sensitivity to EASs of ⪆3 EeV. Simulations of the telescope system, telescope on time, and realized flight trajectory predicted an observation of about 1 event assuming clear sky conditions. The effects of high clouds were estimated to reduce this value by approximately a factor of 2. A manual search and a machine-learning-based search did not find any EAS signals in these data. Here we review the EUSO-SPB1 instrument and flight and the EAS search
Comparing pion production in transport simulations of heavy-ion collisions at 270A MeV under controlled conditions
No full textInternational audienceWithin the Transport Model Evaluation Project (TMEP), we present a detailed study of Sn+Sn collisions at 270A MeV, which are representative reactions used to study the equation of state at suprasaturation densities. We put particular emphasis on the production of pions and resonances, which have been used as probes of the nuclear symmetry energy. In this study, we prescribe a common and rather simple physical model, and follow in detail the results of 4 Boltzmann-Uehling-Uhlenbeck (BUU) models and 6 quantum molecular dynamics (QMD) models. We find that the nucleonic evolution of the collision and the nucleonic observables in these codes do not completely converge, but that the differences among the codes can be understood as being due to several reasons: the basic differences between BUU and QMD models in the representation of the phase-space distributions, computational differences in the mean-field evaluation, and differences in the adopted strategies for the Pauli blocking in the collision integrals. For pionic observables, we find that a higher maximum density leads to an enhanced pion yield and a reduced yield ratio, while a more effective Pauli blocking generally leads to a slightly suppressed pion yield and an enhanced yield ratio, although differences in its implementations do not have a dominating role in the differences among the codes. We specifically investigate the effect of the Coulomb force, and find that it increases the total yield ratio but reduces the ratio at high pion energies. Using only the results of codes that strictly follow the homework specifications, we find a convergence of the codes in the final charged pion yield ratio to less than , while the uncertainty is expected to be reduced to about if the same or similar ingredients are incorporated in each code
New Constraint for Isotropic Lorentz Violation from LHC Data
No full textInternational audienceNew calculations for the kinematics of photon decay to fermions in vacuo under an isotropic violation of Lorentz invariance (LV), parameterized by the Standard-Model Extension (SME), are presented in this paper and used to interpret prompt photon production in LHC data. The measurement of inclusive prompt photon production at the LHC Run 2, with photons observed up to a transverse energy of 2.5 TeV, provides the lower bound on the isotropic coefficient at 95% confidence level. This result improves over the previous bound from hadron colliders by a factor of 55. The calculations for the kinematics of photon decay have further potential use to constrain LV coefficients from the appearance of fermion pairs, for instance, top-antitop
Hadronization of Heavy Quarks
No full textInternational audienceHeavy-flavor hadrons produced in ultra-relativistic heavy-ion collisions are a sensitive probe for studying hadronization mechanisms of the quark-gluon-plasma. In this work, we survey how different transport models for the simulation of heavy-quark diffusion through a quark-gluon plasma in heavy-ion collisions implement hadronization and how this affects final-state observables. Utilizing the same input charm-quark distribution in all models at the hadronization transition, we find that the transverse-momentum dependence of the nuclear modification factor of various charm hadron species has significant sensitivity to the hadronization scheme. In addition, the charm-hadron elliptic flow exhibits a nontrivial dependence on the elliptic flow of the hadronizing partonic medium
Multiplicity-dependent jet modification from di-hadron correlations in pp collisions at TeV
No full textInternational audienceShort-range correlations between charged particles are studied via two-particle angular correlations in pp collisions at TeV. The correlation functions are measured as a function of the relative azimuthal angle and the pseudorapidity separation for pairs of primary charged particles within the pseudorapidity interval and the transverse-momentum range GeV/. Near-side () peak widths are extracted from a generalised Gaussian fitted over the correlations in full pseudorapidity separation (), while the per-trigger associated near-side yields are extracted for the short-range correlations (). 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 ( GeV/). 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
System size dependence of energy loss and correlations of heavy mesons at LHC energies
No full textInternational audienceWe study the system size dependence of heavy quark (HQ) observables at a center of mass energy of TeV to explore whether it can provide further constraints on the physical processes which are involved: energy loss of HQs in the quark gluon plasma (QGP), hadronization and hadronic rescattering. We use the EPOS4HQ approach to study p-p and 0-10% central O-O, Ar-Ar, Kr-Kr and Pb-Pb reactions and investigate in detail the momentum change of heavy quarks from creation until their detection as part of a hadron as well as the enhancement of heavy baryon production at low . We investigate furthermore the origin and the system size dependence of the azimuthal correlations between the heavy quark and the heavy antiquark and how one can bypass the problem that correlations are washed out due to the combinatorial background. We conclude that a systematic study of the system size dependence of the momentum loss allows to separate the momentum loss due to the passage through the QGP from the momentum change due to hadronization and the correlations allow to gain inside into the different pQCD processes in which the heavy quarks are created
JRJC 2023 - Journées de Rencontres Jeunes Chercheurs. Book of Proceedings
No full textJournées de Rencontres Jeunes Chercheurs (JRJC2023). 22-28 octobre 2023, Saint Jean de Monts (France).International audienc
Measurement of the production and elliptic flow of (anti)nuclei in Xe-Xe collisions at = 5.44 TeV
No full textInternational audienceMeasurements of (anti)deuteron and (anti)He production in the rapidity range 0.5 as a function of the transverse momentum and event multiplicity in XeXe collisions at a center-of-mass energy per nucleonnucleon pair of = 5.44 TeV are presented. The coalescence parameters and are measured as a function of the transverse momentum per nucleon. The ratios between (anti)deuteron and (anti)He yields and those of (anti)protons and pions are reported as a function of the mean charged-particle multiplicity density, and compared with two implementations of the statistical hadronization model (SHM) and with coalescence predictions. The elliptic flow of (anti)deuterons is measured for the first time in XeXe collisions and shows features similar to those already observed in PbPb collisions, i.e., the mass ordering at low transverse momentum and the mesonbaryon grouping at intermediate transverse momentum. The production of nuclei is particularly sensitive to the chemical freeze-out temperature of the system created in the collision, which is extracted from a grand-canonical-ensemble-based thermal fit, performed for the first time including light nuclei along with light-flavor hadrons in XeXe collisions. The extracted chemical freeze-out temperature = (154.2 1.1) MeV in XeXe collisions is similar to that observed in PbPb collisions and close to the crossover temperature predicted by lattice QCD calculations