HAL Mines Nantes
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Heavy flavour hadron production in relativistic heavy ion collisions at RHIC and LHC in EPOS4HQ
No full textInternational audienceEmploying the recently developed EPOS4HQ event generator, we study the production of different heavy-flavor mesons in relativistic heavy-ion collisions at RHIC and LHC energies. The transverse momentum spectra, yield ratio, nuclear modification factor, and elliptic flow can be well described in the EPOS4HQ framework. We furthermore analyze the processes which modify these observables as compared to collisions and are at the origin of the experimentally determined nuclear modification factor
Cosmogenic background simulations for the DARWIN observatory at different underground locations
No full textInternational audienceXenon dual-phase time projections chambers (TPCs) have proven to be a successful technology in studying physical phenomena that require low-background conditions. With 40t of liquid xenon (LXe) in the TPC baseline design, DARWIN will have a high sensitivity for the detection of particle dark matter, neutrinoless double beta decay (), and axion-like particles (ALPs). Although cosmic muons are a source of background that cannot be entirely eliminated, they may be greatly diminished by placing the detector deep underground. In this study, we used Monte Carlo simulations to model the cosmogenic background expected for the DARWIN observatory at four underground laboratories: Laboratori Nazionali del Gran Sasso (LNGS), Sanford Underground Research Facility (SURF), Laboratoire Souterrain de Modane (LSM) and SNOLAB. We determine the production rates of unstable xenon isotopes and tritium due to muon-included neutron fluxes and muon-induced spallation. These are expected to represent the dominant contributions to cosmogenic backgrounds and thus the most relevant for site selection
Measurement of the low-energy antitriton inelastic cross section
No full textInternational audienceIn this Letter, the first measurement of the inelastic cross section for antitritonnucleus interactions is reported, covering the momentum range of GeV/. The measurement is carried out using data recorded with the ALICE detector in pp and PbPb collisions at a centre-of-mass energy per nucleon of 13 TeV and 5.02 TeV, respectively. The detector material serves as an absorber for antitriton nuclei. The raw yield of (anti)triton nuclei measured with the ALICE apparatus is compared to the results from detailed ALICE simulations based on the GEANT4 toolkit for the propagation of (anti)particles through matter, allowing one to quantify the inelastic interaction probability in the detector material. This analysis complements the measurement of the inelastic cross section of antinuclei up to carried out by the ALICE Collaboration, and demonstrates the feasibility of the study of the isospin dependence of inelastic interaction cross section with the analysis techniques presented in this Letter
Parallel scattering, saturation, and generalized AGK theorem in the EPOS4 framework, with applications for heavy ion collisions at 5.02 ATeV and at 200 AGeV
No full textInternational audienceUltrarelativistic heavy ion collisions will first realize many nucleon-nucleon scatterings, happening instantaneously and therefore necessarily in parallel, due to the short collision time. An appropriate quantum mechanical tool to treat that problem is S-matrix theory, and it has been known for a long time how to derive a simple geometric probabilistic picture, still widely used, and here the ``AGK theorem'' plays a crucial role. All this is done in a scenario where energy conservation is not taken care of, but this is needed, in particular for Monte Carlo simulations. When introducing energy-momentum sharing properly, the AGK theorem does not apply anymore, nor do simple geometric concepts such as binary scaling. I will discuss this (very serious) problem, and how it can be solved, in the EPOS4 framework. When connecting the multiple Pomeron approach (for parallel scatterings) and pQCD, one is actually forced to implement in a very particular way saturation scales, in order to get an approach free of contradictions. One recovers a ``generalized AGK theorem'' (gAGK), valid at large (larger than the relevant saturation scales). I discuss how gAGK is related to factorization (in proton-proton scatterings) and binary scaling (in heavy ion collisions). I will show some applications, using this new approach as an initial condition for hydrodynamical evolutions, for heavy ion collisions at 5.02 ATeV and at 200 AGeV, to get some idea about the energy dependence
Prompt and non-prompt J production at midrapidity in PbPb collisions at = 5.02 TeV
No full textInternational audienceThe transverse momentum () and centrality dependence of the nuclear modification factor of prompt and non-prompt J, the latter originating from the weak decays of beauty hadrons, have been measured by the ALICE collaboration in PbPb collisions at = 5.02 TeV. The measurements are carried out through the decay channel at midrapidity ( 5 GeV/, which becomes stronger with increasing collision centrality. The results are consistent with similar LHC measurements in the overlapping intervals, and cover the kinematic region down to = 1.5 GeV/ at midrapidity, not accessible by other LHC experiments. The suppression of prompt J in central and semicentral collisions exhibits a decreasing trend towards lower transverse momentum, described within uncertainties by models implementing J production from recombination of c and quarks produced independently in different partonic scatterings. At high transverse momentum, transport models including quarkonium dissociation are able to describe the suppression for prompt J. For non-prompt J, the suppression predicted by models including both collisional and radiative processes for the computation of the beauty-quark energy loss inside the quarkgluon plasma is consistent with measurements within uncertainties
Embedded Software of the KM3NeT Central Logic Board
No full textInternational audienceThe KM3NeT Collaboration is building and operating two deep sea neutrino telescopes at the bottom of the Mediterranean Sea. The telescopes consist of latices of photomultiplier tubes housed in pressure-resistant glass spheres, called digital optical modules and arranged in vertical detection units. The two main scientific goals are the determination of the neutrino mass ordering and the discovery and observation of high-energy neutrino sources in the Universe. Neutrinos are detected via the Cherenkov light, which is induced by charged particles originated in neutrino interactions. The photomultiplier tubes convert the Cherenkov light into electrical signals that are acquired and timestamped by the acquisition electronics. Each optical module houses the acquisition electronics for collecting and timestamping the photomultiplier signals with one nanosecond accuracy. Once finished, the two telescopes will have installed more than six thousand optical acquisition nodes, completing one of the more complex networks in the world in terms of operation and synchronization. The embedded software running in the acquisition nodes has been designed to provide a framework that will operate with different hardware versions and functionalities. The hardware will not be accessible once in operation, which complicates the embedded software architecture. The embedded software provides a set of tools to facilitate remote manageability of the deployed hardware, including safe reconfiguration of the firmware. This paper presents the architecture and the techniques, methods and implementation of the embedded software running in the acquisition nodes of the KM3NeT neutrino telescopes
Investigating charm quark energy loss in medium with the nuclear modification factor of D-tagged jets
No full textInternational audienceThe nuclear modification factor of charm jets, identified by the presence of a D meson among the jet constituents, has been measured for the first time in Pb-Pb collisions at a centre-of-mass energy per nucleon pair TeV with the ALICE detector at the LHC. The D mesons and their charge conjugates are reconstructed from the hadronic decay D. Jets are reconstructed from D-meson candidates and charged particles using the anti- algorithm with jet resolution parameter , in the jet transverse momentum () range GeV/ and pseudorapidity . A hint of reduced suppression in the charm-jet is observed in comparison to inclusive jets in central Pb-Pb collisions with a significance of about 2 in GeV/, suggesting the in-medium energy loss to depend on both the difference between quark and gluon coupling strength (Casimir colour-charge effect) and quark mass (dead-cone effect). The data are compared with model calculations that include mass effects in the in-medium energy loss. Among these, LIDO provides the best description of the data, highlighting the role of mass effects in interpreting the results
Search for Very-Short-Baseline Oscillations of Reactor Antineutrinos with the SoLid Detector
No full textInternational audienceIn this letter we report the first scientific result based on antineutrinos emitted from the BR2 reactor at SCK CEN. The SoLid experiment uses a novel type of highly granular detector whose basic detection unit combines two scintillators, PVT and 6LiF:ZnS(Ag), to measure antineutrinos via their inverse-beta-decay products. An advantage of PVT is its highly linear response as a function of deposited particle energy. The full-scale detector comprises 12800 voxels and operates over a very short 6.3--8.9 m baseline from the reactor core. The detector segmentation and its 3D imaging capabilities facilitate the extraction of the positron energy from the rest of the visible energy, allowing the latter to be utilised for signal-background discrimination. We present a result based on 280 reactor-on days (55 MW mean power) and 172 reactor-off days, respectively, of live data-taking. A total of 29479 603 (stat.) antineutrino candidates have been selected, corresponding to an average rate of 105 events per day and a signal-to-background ratio of 0.27. A search for disappearance of antineutrinos to a sterile state has been conducted using complementary model-dependent frequentist and Bayesian fits, providing constraints on the allowed region of the Reactor Antineutrino Anomaly