HAL Mines Nantes
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    7271 research outputs found

    Design and performance of the field cage for the XENONnT experiment

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    HAL CCSD
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    International audienceThe precision in reconstructing events detected in a dual-phase time projection chamber depends on an homogeneous and well understood electric field within the liquid target. In the XENONnT TPC the field homogeneity is achieved through a double-array field cage, consisting of two nested arrays of field shaping rings connected by an easily accessible resistor chain. Rather than being connected to the gate electrode, the topmost field shaping ring is independently biased, adding a degree of freedom to tune the electric field during operation. Two-dimensional finite element simulations were used to optimize the field cage, as well as its operation. Simulation results were compared to 83mKr{}^{83m}\mathrm{Kr} calibration data. This comparison indicates an accumulation of charge on the panels of the TPC which is constant over time, as no evolution of the reconstructed position distribution of events is observed. The simulated electric field was then used to correct the charge signal for the field dependence of the charge yield. This correction resolves the inconsistent measurement of the drift electron lifetime when using different calibrations sources and different field cage tuning voltages

    Real-time Monitoring for the Next Core-Collapse Supernova in JUNO

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    HAL CCSD
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    International audienceCore-collapse supernova (CCSN) is one of the most energetic astrophysical events in the Universe. The early and prompt detection of neutrinos before (pre-SN) and during the SN burst is a unique opportunity to realize the multi-messenger observation of the CCSN events. In this work, we describe the monitoring concept and present the sensitivity of the system to the pre-SN and SN neutrinos at the Jiangmen Underground Neutrino Observatory (JUNO), which is a 20 kton liquid scintillator detector under construction in South China. The real-time monitoring system is designed with both the prompt monitors on the electronic board and online monitors at the data acquisition stage, in order to ensure both the alert speed and alert coverage of progenitor stars. By assuming a false alert rate of 1 per year, this monitoring system can be sensitive to the pre-SN neutrinos up to the distance of about 1.6 (0.9) kpc and SN neutrinos up to about 370 (360) kpc for a progenitor mass of 30M⊙M_{\odot} for the case of normal (inverted) mass ordering. The pointing ability of the CCSN is evaluated by using the accumulated event anisotropy of the inverse beta decay interactions from pre-SN or SN neutrinos, which, along with the early alert, can play important roles for the followup multi-messenger observations of the next Galactic or nearby extragalactic CCSN

    Multiplicity and event-scale dependent flow and jet fragmentation in pp collisions at s\sqrt{s} = 13 TeV and in p−-Pb collisions at sNN\sqrt{s_\mathrm{NN}} = 5.02 TeV

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    Springer
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    International audienceLong- and short-range correlations for pairs of charged particles are studied via two-particle angular correlations in pp collisions at s=13\sqrt{s}=13 TeV and p−-Pb collisions at sNN=5.02\sqrt{s_\mathrm{NN}} = 5.02 TeV. The correlation functions are measured as a function of relative azimuthal angle Δφ\Delta\varphi and pseudorapidity separation Δη\Delta\eta for pairs of primary charged particles within the pseudorapidity interval ∣η∣<0.9|\eta| < 0.9 and the transverse-momentum interval 1<pT<41 < p_{\rm T} < 4 GeV/cc. Flow coefficients are extracted for the long-range correlations (1.6<∣Δη∣<1.81.6 < |\Delta\eta| <1.8) in various high-multiplicity event classes using the low-multiplicity template fit method. The method is used to subtract the enhanced yield of away-side jet fragments in high-multiplicity events. These results show decreasing flow signals toward lower multiplicity events. Furthermore, the flow coefficients for events with hard probes, such as jets or leading particles, do not exhibit any significant changes compared to those obtained from high-multiplicity events without any specific event selection criteria. The results are compared with hydrodynamic-model calculations, and it is found that a better understanding of the initial conditions is necessary to describe the results, particularly for low-multiplicity events

    Multiplicity-dependent production of Σ(1385)±\Sigma(1385)^{\pm} and Ξ(1530)0\Xi(1530)^{0} in pp collisions at s=13\sqrt{s}=13 TeV

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    Springer
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    International audienceThe production yields of the Σ(1385)±\Sigma(1385)^{\pm} and Ξ(1530)0\Xi(1530)^{0} resonances are measured in pp collisions at s=13\sqrt{s}=13 TeV with ALICE. The measurements are performed as a function of the charged particle multiplicity ⟨dNch/dη⟩\langle \mathrm{d}N_\mathrm{ch}/\mathrm{d}\eta \rangle, which is related to the energy density produced in the collision. The results include transverse momentum (pTp_{\rm T}) distributions, pTp_{\rm T}-integrated yields, mean transverse momenta of Σ(1385)±\Sigma(1385)^{\pm} and Ξ(1530)0\Xi(1530)^{0}, as well as ratios of the pTp_{\rm T}-integrated resonance yields relative to yields of other hadron species. The Σ(1385)±/π±\Sigma(1385)^{\pm}/\pi^{\pm} and Ξ(1530)0/π±\Xi(1530)^{0}/\pi^{\pm} yield ratios are consistent with the trend of the enhancement of strangeness production from low to high multiplicity pp collisions, which was previously observed for strange and multi-strange baryons. The yield ratio between the measured resonances and the long-lived baryons with the same strangeness content exhibits a hint of a mild increasing trend at low multiplicity, despite too large uncertainties to exclude the flat behaviour. The results are compared to predictions from models such as EPOS-LHC and PYTHIA 8 with Rope shoving. The latter provides the best description of the multiplicity dependence of the Σ(1385)±\Sigma(1385)^{\pm} and Ξ(1530)0\Xi(1530)^{0} production in pp collisions at s=13\sqrt{s}=13 TeV

    Skewness and kurtosis of mean transverse momentum fluctuations at the LHC energies

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    HAL CCSD
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    International audienceThe first measurements of skewness and kurtosis of mean transverse momentum (⟨pT⟩\langle p_\mathrm{T}\rangle) fluctuations are reported in Pb−-Pb collisions at sNN\sqrt{s_\mathrm{NN}} = 5.02 TeV, Xe−-Xe collisions at sNN\sqrt{s_\mathrm{NN}}== 5.44 TeV and pp collisions at s=5.02\sqrt{s} = 5.02 TeV using the ALICE detector. The measurements are carried out as a function of system size ⟨dNch/dη⟩∣η∣<0.51/3\langle \mathrm{d}N_\mathrm{ch}/\mathrm{d}\eta\rangle_{|\eta|<0.5}^{1/3}, using charged particles with transverse momentum (pTp_\mathrm{T}) and pseudorapidity (η\eta), in the range 0.2<pT<3.00.2 < p_\mathrm{T} < 3.0 GeV/cc and ∣η∣<0.8|\eta| < 0.8, respectively. In Pb−-Pb and Xe−-Xe collisions, positive skewness is observed in the fluctuations of ⟨pT⟩\langle p_\mathrm{T}\rangle for all centralities, which is significantly larger than what would be expected in the scenario of independent particle emission. This positive skewness is considered a crucial consequence of the hydrodynamic evolution of the hot and dense nuclear matter created in heavy-ion collisions. Furthermore, similar observations of positive skewness for minimum bias pp collisions are also reported here. Kurtosis of ⟨pT⟩\langle p_\mathrm{T}\rangle fluctuations is found to be in good agreement with the kurtosis of Gaussian distribution, for most central Pb−-Pb collisions. Hydrodynamic model calculations with MUSIC using Monte Carlo Glauber initial conditions are able to explain the measurements of both skewness and kurtosis qualitatively from semicentral to central collisions in Pb--Pb system. Color reconnection mechanism in PYTHIA8 model seems to play a pivotal role in capturing the qualitative behavior of the same measurements in pp collisions

    Multi-Calorimetry in Light-based Neutrino Detectors

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    HAL CCSD
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    International audienceNeutrino detectors are among the largest photonics instruments built for fundamental research. Since its inception, neutrino detection has been inexorably linked to the challenging detection of scarce photons in huge instrumented volumes. Many discoveries in neutrino physics, including the neutrino itself, are inseparable from the evolution of the detector photonics interfaces, i.e. photo-sensors and readout electronics, to yield ever higher precision and richer detection information. The measurement of the energy of neutrinos, referred to as calorimetry, is pursued today to reach permille level systematics control precision, thus leading to further innovation in specialised photonics. This publication describes a novel articulation that detectors may be endowed with multiple photonics interfaces for simultaneous light detection to yield unprecedented high-precision calorimetry. This multi-calorimetry approach opens the novel notion of dual-calorimetry detectors as an evolution from the single-calorimetry setups used over several decades for most experiments so far. The dual-calorimetry design exploits unique response synergies between photon counting and photon-integration detection systems, including correlations and cancellations between calorimetric responses, to yield the unprecedented mitigation of the dominant response systematic effects today for the possible improved design of a new generation of neutrino experiments

    Multiplicity dependence of charged-particle intra-jet properties in pp collisions at s\sqrt{s} = 13 TeV

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    HAL CCSD
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    International audienceThe first measurement of the multiplicity dependence of intra-jet properties of leading charged-particle jets in proton-proton (pp) collisions is reported. The mean charged-particle multiplicity and jet fragmentation distributions are measured in minimum-bias and high-multiplicity pp collisions at s\sqrt{s} = 13 TeV using the ALICE detector. Jets are reconstructed from charged particles produced in the midrapidity region (∣η∣<0.9|\eta| < 0.9) using the sequential recombination anti-kTk_{\rm T} algorithm with jet resolution parameters RR = 0.2, 0.3, and 0.4 for the transverse momentum (pTp_{\rm T}) interval 5−-110 GeV/cc. High-multiplicity events are selected by the forward V0 scintillator detectors. The mean charged-particle multiplicity inside the leading jet cone rises monotonically with increasing jet pTp_{\rm T} in qualitative agreement with previous measurements at lower energies. The distributions of jet fragmentation functions zchz^{\rm ch} and ξch\xi^{\rm ch} are measured for different jet-pTp_{\rm T} intervals. Jet-pTp_{\rm T} independent fragmentation of leading jets is observed for wider jets except at high- and low-zchz^{\rm ch}. The observed "hump-backed plateau" structure in the ξch\xi^{\rm ch} distribution indicates suppression of low-pTp_{\rm T} particles. In high-multiplicity events, an enhancement of the fragmentation probability of low-zchz^{\rm ch} particles accompanied by a suppression of high-zchz^{\rm ch} particles is observed compared to minimum-bias events. This behavior becomes more prominent for low-pTp_{\rm T} jets with larger jet radius. The results are compared with predictions of QCD-inspired event generators, PYTHIA 8 with Monash 2013 tune and EPOS LHC. It is found that PYTHIA 8 qualitatively reproduces the jet modification in high-multiplicity events except at high jet pTp_{\rm T}. These measurements provide important constraints to models of jet fragmentation

    A numerical algorithm for solving the coupled Schrödinger equations using inverse power method

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    HAL CCSD
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    International audienceThe inverse power method is a numerical algorithm to obtain the eigenvectors of a matrix. In this work, we develop an iteration algorithm, based on the inverse power method, to numerically solve the Schrödinger equation that couples an arbitrary number of components. Such an algorithm can also be applied to the multi-body systems. To show the power and accuracy of this method, we also present an example of solving the Dirac equation under the presence of an external scalar potential and a constant magnetic field, with source code publicly available

    Heavy ion collisions from 62.4 AGeV down to 4 AGeV in the EPOS4 framework

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    HAL CCSD
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    International audienceThe EPOS4 project is an attempt to construct a realistic model for describing relativistic collisions of different systems, from proton-proton (pppp) to nucleus-nucleus (AAAA), at energies from several TeV per nucleon down to several GeV. We argue that a parallel scattering formalism (as in EPOS4) is relevant for primary scatterings in AA collisions above 4 AGeV, whereas sequential scattering (cascade) is appropriate below. We present briefly the basic elements of EPOS4, and then investigate heavy ion collisions from 62.4 AGeV down to 4 AGeV, to understand how physics changes with energy, studying in particular the disappearance of the fluid component at low energies

    Double-graviton production from Standard Model plasma

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    Institute of Physics (IOP)
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    International audienceThe thermal plasma filling the early universe generated a stochastic gravitational wave background that peaks in the microwave frequency range today. If the graviton production rate is expressed as a series in a fine-structure constant, α\alpha, and the temperature over the Planck mass, T2/mpl2T^2_{ } / m_{\rm pl}^2, then the lowest-order contributions come from single (∼αT2/mpl2\sim \alpha T^2_{ }/m_{\rm pl}^2) and double (∼T4/mpl4\sim T^4_{ }/m_{\rm pl}^4) graviton production via 2→22\to 2 scatterings. We show that in the Standard Model, single-graviton production dominates if the maximal temperature is smaller than 4×10184\times 10^{18}_{ } GeV. This justifies previous calculations which relied solely on single-graviton production. We mention Beyond the Standard Model scenarios in which the single and double-graviton contributions could be of comparable magnitudes. Finally, we elaborate on what these results imply for the range of applicability of General Relativity as an effective theory

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    HAL Mines Nantes
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