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Unveiling hadronic resonance dynamics at LHC energies: insights from EPOS4
No full textInternational audienceHadronic resonances, with lifetimes of a few fm/\textit{c}, are key tools for studying the hadronic phase in high-energy collisions. This work investigates resonance production in pp collisions at TeV and in PbPb collisions at TeV using the EPOS4 model, which can switch the Ultra-relativistic Quantum Molecular Dynamics (UrQMD) ON and OFF, enabling the study of final-state hadronic interactions. We focus on hadronic resonances and the production of non-strange and strange hadrons, addressing effects like rescattering, regeneration, baryon-to-meson production, and strangeness enhancement, using transverse momentum () spectra and particle ratios. Rescattering and strangeness effects are important at low p_\rm{T}, while baryon-to-meson ratios dominate at intermediate p_\rm{T}. A strong mass-dependent radial flow is observed in the most central PbPb collisions. The average p_\rm{T}, scaled with reduced hadron mass (mass divided by valence quarks), shows a deviation from linearity for short-lived resonances. By analyzing the yield ratios of short-lived resonances to stable hadrons in pp and PbPb collisions, we estimate the time duration () of the hadronic phase as a function of average charged multiplicity. The results show that increases with multiplicity and system size, with a nonzero value in high-multiplicity pp collisions. Proton (p), strange (), and multi-strange (, ) baryon production in central PbPb collisions is influenced by strangeness enhancement and baryon-antibaryon annihilation. Comparing with LHC measurements offers insights into the dynamics of the hadronic phase
The High Voltage Splitter board for the JUNO SPMT system
No full textInternational audienceThe Jiangmen Underground Neutrino Observatory (JUNO) in southern China is designed to study neutrinos from nuclear reactors and natural sources to address fundamental questions in neutrino physics. Achieving its goals requires continuous operation over a 20-year period. The small photomultiplier tube (small PMT or SPMT) system is a subsystem within the experiment composed of 25600 3-inch PMTs and their associated readout electronics. The High Voltage Splitter (HVS) is the first board on the readout chain of the SPMT system and services the PMTs by providing high voltage for biasing and by decoupling the generated physics signal from the high-voltage bias for readout, which is then fed to the front-end board. The necessity to handle high voltage, manage a large channel count, and operate stably for 20 years imposes significant constraints on the physical design of the HVS. This paper serves as a comprehensive documentation of the HVS board: its role in the SPMT readout system, the challenges in its design, performance and reliability metrics, and the methods employed for production and quality control
Development of the Range Counter for the COMET Phase- Experiment
No full textInternational audienceThe COMET Phase- experiment aims to evaluate the novel muon transport beamline for the muon-to-electron conversion search at J-PARC, Japan. A dedicated Range Counter (RC) was developed to measure the momentum spectrum of transported negative muons with momenta of 30--100 MeV/. The RC consists of graphite momentum degraders, a muon absorber, and plastic scintillation counters (, , and ) to detect decay-in-orbit (DIO) electrons from stopped muons. The number of muons stopped in the absorber is reconstructed from the decay time distribution. A copper absorber was selected due to the short lifetime of muonic atoms in copper, which enhances signal separation. The counters' performance was evaluated experimentally. The Counter, made of a scintillator plate, achieved a muon-trigger efficiency exceeding 99.9%. The and Counters also demonstrated high electron-detection efficiencies of %. Based on these results, simulation studies estimate the acceptance for reconstructing the number of DIO electrons from the absorber to be approximately 47% with a corresponding signal purity of 60% against muon capture-induced backgrounds
Further Characterisation of Digital Pixel Test Structures Implemented in a 65 nm CMOS Process
No full textInternational audienceThe next generation of MAPS for future tracking detectors will have to meet stringent requirements placed on them. One such detector is the ALICE ITS3 that aims to be very light at 0.07% X/X per layer and have a low power consumption of 40 mW/cm by implementing wafer-scale MAPS bent into cylindrical half layers. To address these challenging requirements, the ALICE ITS3 project, in conjunction with the CERN EP R&D on monolithic pixel sensors, proposed the Tower Partners Semiconductor Co. 65 nm CMOS process as the starting point for the sensor. After the initial results confirmed the detection efficiency and radiation hardness, the choice of the technology was solidified by demonstrating the feasibility of operating MAPS in low-power consumption regimes, < 50 mW/cm, while maintaining high-quality performance. This was shown through a detailed characterisation of the Digital Pixel Test Structure (DPTS) prototype exposed to X-rays and ionising beams, and the results are presented in this article. Additionally, the sensor was further investigated through studies of the fake-hit rate, the linearity of the front-end in the range 1.7-28 keV, the performance after ionising irradiation, and the detection efficiency of inclined tracks in the range 0-45
Search for a boosted Higgs boson decaying to bottom quark pairs in association with a W or Z boson in proton-proton collisions at = 13 TeV
No full textInternational audienceA search is conducted for standard model Higgs bosons with large transverse momentum () decaying to bottom quark pairs and produced in association with a hadronically decaying W or Z boson at the LHC. The result is based on a dataset of proton-proton collisions at a center-of-mass energy of 13 TeV collected with the CMS detector in 20162018, corresponding to an integrated luminosity of 138 fb. Boosted Higgs, W, and Z boson decays are reconstructed using large-radius jets with 450 GeV and identified with heavy-flavor classifiers based on a graph convolutional neural network. The observed signal strength relative to the standard model expectation is = 0.7 including statistical and systematic uncertainties
Effects of small organic molecules on the retention of uranyl(VI) on clay surfaces: a molecular dynamics study
No full textCosmoglobe DR2. IV. Modelling starlight in DIRBE with Gaia and WISE
No full textInternational audienceWe present a model of starlight emission in the Diffuse Infrared Background Explorer (DIRBE) data between 1.25 and 25m based on \textit{Gaia} and WISE measurements. We include two classes of compact objects, namely bright stars with individual spectral energy densities (SEDs) measured by \textit{Gaia}, and a combined diffuse background of dim point source emission. Of the 424 829 bright sources that we fit, the number of stars with a flux density detected by WISE at Galactic latitudes at more than is 94 680, for an average of 1.36~stars per DIRBE beam area. For each star, we adopt physical parameters (, , and [M/H]) from \textit{Gaia}; use these to identify a best-fit effective SED with the PHOENIX stellar model library; convolve with the respective DIRBE bandpass; and fit an overall free amplitude per star within the Bayesian end-to-end \texttt{Cosmoglobe} DR2 framework. The contributions from faint sources are accounted for by coadding all 710 825 587 WISE sources not included as bright stars, and fit one single overall amplitude per DIRBE band. Based on this model we find that total star emission accounts for 91 % of the observed flux density at 2.2 m; 54 % at 4.9m; and 1 % at 25 m. As shown in companion papers, this new model is sufficiently accurate to support high-precision measurements of both the Cosmic Infrared Background monopole and zodiacal light emission in the three highest DIRBE frequencies
Exploring the effect of entrance channel mass asymmetry in the fission of Tl* nucleus
No full textInternational audienceFission fragment mass ratio distributions have been measured for the reactions 19F+178Hf and 16O + 181Ta, both leading to the same compound nucleus, 197Tl, at near-Coulomb barrier energies. The measured fission fragment mass width for both these systems does not show any substantial deviation from the statistical model predictions, which indicates the absence of non-compound nuclear reactions like quasi-fission. The measured mass widths of both the reactions at the same excitation energy are comparable within the experimental uncertainty and show a gradual increase with excitation energy. No noticeable influence of effect of entrance channel mass asymmetry on fragment mass distribution in these reactions, which differs from the previously reported entrance channel-dependent variation in average pre-scission neutron multiplicity
TXS 0506+056-like blazar sources and their role as possible neutrino emitters
No full textInternational audienceThe interest in blazars as candidate neutrino emitters grew after the 3 evidence for a contemporaneous joint photon and neutrino emission from the flaring blazar TXS 0506+056 in 2017. Blazars, a class of extragalactic sources with relativistic jets pointing toward Earth, present a broadband emission interpretable via leptonic and hadronic processes, the latter relevant for proton acceleration and neutrino production. Several emission models have been developed to explain this multi-messenger observation, but the details of the neutrino production and the nature of TXS 0506+056 are not yet fully understood. In this work we investigate the properties of sources similar to TXS 0506+056. We select a sample of blazars from the Fermi 4LAC-DR2 catalog by constraining a number of key parameters in ranges centered on TXS 0506+056 values. We estimate their disk accretion efficiency and model their spectral energy distribution (SED) in terms of lepto-hadronic emission, gaining information respectively on the potential similarity of their environment with that of TXS 0506+056 and on their neutrino flux and detectability prospects at TeV energies. Our study shows the candidates’ high energy emission to be dominated by leptonic processes. Part of them also show a high accretion rate, characteristic of FSRQs. For these sources, the very high energy (VHE) and neutrino fluxes appear undetectable by current and future instruments in an average emission state
Coexistence of shapes and octupole correlation in <math><mmultiscripts><mi>Kr</mi><mprescripts/><none/><mn>82</mn></mmultiscripts></math>
No full textInternational audienceLow- and intermediate-spin negative-parity band structures have been investigated in the Kr82 nucleus using the fusion-evaporation reaction Ge76 (Be9, 3n) at ELab≈31 MeV. Lifetimes of the states of interest in Kr82 have been measured using the Doppler shift attenuation method with the help of the Indian National Gamma Array, and the parity of the states has been confirmed from polarization measurements. The deduced B(M1) and B(E2) values from the lifetime measurements in comparison with the particle rotor model and the total Routhian surfaces calculations reveal that the bands DB1 and DB2 are based on the collective oblate and prolate deformed core, respectively. The enhanced electric dipole strengths, B(E1)s, and dipole moments, |D0|s, for the parity-changing transitions connecting the negative-parity bands DB1 and DB2 to the ground-state positive-parity band QB1 ensure the octupole correlation in Kr82