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Jet modification via -hadron correlations in AuAu collisions at GeV
No full textInternational audienceHigh-momentum two-particle correlations are a useful tool for studying jet-quenching effects in the quark-gluon plasma. Angular correlations between neutral-pion triggers and charged hadrons with transverse momenta in the range 4--12~GeV/ and 0.5--7~GeV/, respectively, have been measured by the PHENIX experiment in 2014 for AuAu collisions at ~GeV. Suppression is observed in the yield of high-momentum jet fragments opposite the trigger particle, which indicates jet suppression stemming from in-medium partonic energy loss, while enhancement is observed for low-momentum particles. The ratio and differences between the yield in AuAu collisions and collisions, and , as a function of the trigger-hadron azimuthal separation, , are measured for the first time at the Relativistic Heavy Ion Collider. These results better quantify how the yield of low- associated hadrons is enhanced at wide angle, which is crucial for studying energy loss as well as medium-response effects
Simultaneous impacts of nuclear shell structure and collectivity on -decay: evidence from Ga
No full textInternational audienceThe Gamow-Teller strength distribution covering the entire -decay window, up to 10.312(4) MeV, of Ga was measured for the first time in photo-fission of UC induced by 50 MeV electron beam. The new data show significant enhancement in the high-energy region with a jump-structure. Simultaneously, the de-exciting behavior of -populated states presents a competition between de-excitation to 2 [ = 0.155(9)] and to 2 [ = 0.053)] in Ge. Based on these facts and combined with a realistic shell model calculation and systematic analysis of logft ratio between precursor -decay to 2 and to 2 of Ga isotopes, we conclude that these phenomena evidence simultaneous impacts of nuclear shell structure and collectivity on B(GT) and its distribution and, therefore, the half-life of the precursor. These data prove that the nucleus as a multi-nucleon correlated quantum system reacts as a whole when -decay occurs in contrast to simple single-particle excitation. Additionally, the comparison with the theoretical results evidence how challenging is the description of the experimental data obtained, and render this experimental outcome a sound test for the theoretical models
Investigating strangeness enhancement in jet and medium via (1020) production in pPb collisions at = 5.02 TeV
No full textInternational audienceThis work aims to differentiate strangeness produced from hard processes (jet-like) and softer processes (underlying event) by measuring the angular correlation between a high-momentum trigger hadron (h) acting as a jet-proxy and a produced strange hadron ( meson). Measuring h correlations at midrapidity in pPb collisions at = 5.02 TeV as a function of event multiplicity provides insight into the microscopic origin of strangeness enhancement in small collision systems. The jet-like and the underlying-event-like strangeness production are investigated as a function of event multiplicity. They are also compared between a lower and higher momentum region. The evolution of the per-trigger yields within the near-side (aligned with the trigger hadron) and away-side (in the opposite direction of the trigger hadron) jet is studied separately, allowing for the characterization of two distinct jet-like production regimes. Furthermore, the h correlations within the underlying event give access to a production regime dominated by soft production processes, which can be compared directly to the in-jet production. Comparisons between h and dihadron correlations show that the observed strangeness enhancement is largely driven by the underlying event, where the ratio is significantly larger than within the jet regions. As multiplicity increases, the fraction of the total yield coming from jets decreases compared to the underlying event production, leading to high-multiplicity events being dominated by the increased strangeness production from the underlying event
Differential Sensitivity of the KM3NeT/ARCA detector to a diffuse neutrino flux and to point-like source emission: Exploring the case of the Starburst Galaxies
No full textInternational audienceKM3NeT/ARCA is a Cherenkov neutrino telescope under construction in the Mediterranean sea, optimised for the detection of astrophysical neutrinos with energies above ∼1 TeV. In this work, using Monte Carlo simulations including all-flavour neutrinos, the integrated and differential sensitivities for KM3NeT/ARCA are presented considering the case of a diffuse neutrino flux as well as extended and point-like neutrino sources. This analysis is applied to Starburst Galaxies demonstrating that the detector has the capability of tracing TeV neutrinos from these sources. Remarkably, after eight years, a hard power-law spectrum from the nearby Small Magellanic Cloud can be constrained. The sensitivity and discovery potential for NGC 1068 is also evaluated showing that KM3NeT/ARCA will discriminate between different astrophysical components of the measured neutrino flux after 3 years of data taking
Modification of charged-particle jets in event-shape engineered PbPb collisions at TeV
No full textInternational audienceCharged-particle jet yields have been measured in semicentral PbPb collisions at center-of-mass energy per nucleon-nucleon collision TeV with the ALICE detector at the LHC. These yields are reported as a function of the jet transverse momentum, and further classified by their angle with respect to the event plane and the event shape, characterized by ellipticity, in an effort to study the path-length dependence of jet quenching. Jets were reconstructed at midrapidity from charged-particle tracks using the anti- algorithm with resolution parameters 0.2 and 0.4, with event-plane angle and event-shape values determined using information from forward scintillating detectors. The results presented in this letter show that, in semicentral PbPb collisions, there is no significant difference between jet yields in predominantly isotropic and elliptical events. However, out-of-plane jets are observed to be more suppressed than in-plane jets. Further, this relative suppression is greater for low transverse momentum ( 50 GeV/) 0.2 jets produced in elliptical events, with out-of-plane to in-plane jet-yield ratios varying up to 5.2 between different event-shape classes. These results agree with previous studies indicating that jets experience azimuthally anisotropic suppression when traversing the QGP medium, and can provide additional constraints on the path-length dependence of jet energy loss
Swift-BAT GUANO follow-up of gravitational-wave triggers in the third LIGO-Virgo-KAGRA observing run
No full textInternational audienceWe present results from a search for X-ray/gamma-ray counterparts of gravitational-wave (GW) candidates from the third observing run (O3) of the LIGO-Virgo-KAGRA (LVK) network using the Swift Burst Alert Telescope (Swift-BAT). The search includes 636 GW candidates received in low latency, 86 of which have been confirmed by the offline analysis and included in the third cumulative Gravitational-Wave Transient Catalogs (GWTC-3). Targeted searches were carried out on the entire GW sample using the maximum--likelihood NITRATES pipeline on the BAT data made available via the GUANO infrastructure. We do not detect any significant electromagnetic emission that is temporally and spatially coincident with any of the GW candidates. We report flux upper limits in the 15-350 keV band as a function of sky position for all the catalog candidates. For GW candidates where the Swift-BAT false alarm rate is less than 10 Hz, we compute the GW--BAT joint false alarm rate. Finally, the derived Swift-BAT upper limits are used to infer constraints on the putative electromagnetic emission associated with binary black hole mergers
GRANDlib: A simulation pipeline for the Giant Radio Array for Neutrino Detection (GRAND)
No full textInternational audienceThe operation of upcoming ultra-high-energy cosmic-ray, gamma-ray, and neutrino radio-detection experiments, like the Giant Radio Array for Neutrino Detection (GRAND), poses significant computational challenges involving the production of numerous simulations of particle showers and their detection, and a high data throughput. GRANDlib is an open-source software tool designed to meet these challenges. Its primary goal is to perform end-to-end simulations of the detector operation, from the interaction of ultra-high-energy particles, through -- by interfacing with external air-shower simulations -- the ensuing particle shower development and its radio emission, to its detection by antenna arrays and its processing by data-acquisition systems. Additionally, GRANDlib manages the visualization, storage, and retrieval of experimental and simulated data. We present an overview of GRANDlib to serve as the basis of future GRAND analyses
Renormalized critical dynamics and fluctuations in model A
No full textInternational audienceIn the context of relativistic heavy-ion collisions, we explore the stochastic and dissipative relaxational dynamics of a non-conserved order parameter in a interaction. The cutoff of the theory is provided by the lattice spacing chosen for our numerical simulations. As a consequence, observables become dependent on that scale. We consider a possible first-order phase transition and an evolution close to a critical point. We demonstrate that using a lattice counterterm restores the expected behavior of the mean, variance and kurtosis: the mean and the variance become lattice spacing independent, and we recover the correct expectation value of the mean, the growth of the variance with the correlation length and the expected minimum in the kurtosis. Our findings hold true in equilibrium and during the dynamical relaxation, and therefore mark an important step towards a fully fluctuating fluid dynamical setup
