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Lattice QCD estimates of thermal photon production from the QGP
No full textInternational audienceThermal photons produced in heavy-ion collision experiments are an important observable for understanding quark-gluon plasma (QGP). The thermal photon rate from the QGP at a given temperature can be calculated from the spectral function of the vector current correlator. Extraction of the spectral function from the lattice correlator is known to be an ill-conditioned problem, as there is no unique solution for a spectral function for a given lattice correlator with statistical errors. The vector current correlator, on the other hand, receives a large ultraviolet contribution from the vacuum, which makes the extraction of the thermal photon rate difficult from this channel. We therefore consider the difference between the transverse and longitudinal part of the spectral function, only capturing the thermal contribution to the current correlator, simplifying the reconstruction significantly. The lattice correlator is calculated for light quarks in quenched QCD at MeV (), as well as in 2+1 flavor QCD at MeV () with MeV. In order to quantify the non-perturbative effects, the lattice correlator is compared with the corresponding estimate of correlator. The reconstruction of the spectral function is performed in several different frameworks, ranging from physics-informed models of the spectral function to more general models in the Backus-Gilbert method and Gaussian Process regression. We find that the resulting photon rates agree within errors
The XENONnT Dark Matter Experiment
No full textInternational audienceThe multi-staged XENON program at INFN Laboratori Nazionali del Gran Sasso aims to detect dark matter with two-phase liquid xenon time projection chambers of increasing size and sensitivity. The XENONnT experiment is the latest detector in the program, planned to be an upgrade of its predecessor XENON1T. It features an active target of 5.9 tonnes of cryogenic liquid xenon (8.5 tonnes total mass in cryostat). The experiment is expected to extend the sensitivity to WIMP dark matter by more than an order of magnitude compared to XENON1T, thanks to the larger active mass and the significantly reduced background, improved by novel systems such as a radon removal plant and a neutron veto. This article describes the XENONnT experiment and its sub-systems in detail and reports on the detector performance during the first science run
Photoproduction of KK pairs in ultra-peripheral collisions
No full textInternational audienceKK pairs may be produced in photonuclear collisions, either from the decays of photoproduced mesons, or directly as non-resonant KK pairs. Measurements of KK photoproduction probe the couplings between the and charged kaons with photons and nuclear targets. We present the first measurement of coherent photoproduction of KK pairs on lead ions in ultra-peripheral collisions using the ALICE detector, including the first investigation of direct KK production. There is significant KK production at low transverse momentum, consistent with coherent photoproduction on lead targets. In the mass range GeV/ above the resonance, for rapidity and GeV/, the measured coherent photoproduction cross section is = 3.37 (stat.) (syst.) mb. The centre-of-mass energy per nucleon of the photon-nucleus (Pb) system ranges from 33 to 188 GeV, far higher than previous measurements on heavy-nucleus targets. The cross section is larger than expected for photoproduction alone. The mass spectrum is fit to a cocktail consisting of decays, direct KK photoproduction, and interference between the two. The confidence regions for the amplitude and relative phase angle for direct KK photoproduction are presented
Production Cross Section Measurements of the natNi(d,x)61Cu Reaction
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Performances of a radial TPC for the detection of neutrinoless double beta decay
No full textInternational audienceTo search for decay with unprecedented sensitivity, the R2D2 collaboration is developing a radial time projection chamber with a fiducial mass of half a ton of 136Xe at high pressure. The various approaches implemented to eliminate the radioactive background are presented in terms of detector design, topological recognition of interactions, and event energy reconstruction. The developed tools allow for the disentangling of the sought-after signal from the background, and the projected sensitivity after ten years of data taking yields a half-life limit exceeding years, along with a constraint on the effective neutrino mass , sufficient to exclude the inverted mass hierarchy region
Colloidal magnetic gels for the decontamination of limited access metallic surfaces
No full textInternational audienceHandling nuclear metallic waste is a crucial issue for the nuclear industry, notably by using adapted decontamination processes. Colloidal gels can be applied by spraying for nuclear decontamination of large and plane metallic surfaces, such as walls or floors. However, this implementation mode limits their use for the decontamination of inaccessible or complex geometries surfaces. For that purpose, decontamination magnetic gels have been formulated by incorporating magnetite particles in a pre-synthesized colloidal gel able to decontaminate stainless steel. Such gels can thus be attracted by a magnet, allowing remote application to surfaces with limited access. The presence of magnetite particles does not influence the inherent decontamination properties of the gel, but plays a significant role on the spreading properties by increasing the gel viscosity. Then, a linear relationship between the gel thickness and the decontamination possibilities has been highlighted. Furthermore, as the magnetite particles dissolve in the gel with time, spreading properties, and consequently the decontamination properties, are modified. Finally, a formulation compromise has to be found for a long-term storage of the gels, while maintaining their efficiency
Investigating the interplay between initial hard processes and final-state effects measuring prompt and non-prompt J/psi with ALICE
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Jet definition and TMD factorisation in SIDIS
No full textInternational audienceUsing the colour dipole picture of Deep Inelastic Scattering (DIS) and the Colour Glass Condensate effective theory, we study semi-inclusive jet production in DIS at small in the limit where the photon virtuality is much larger than the transverse momentum squared of the produced jet. In this limit, the cross-section is dominated by aligned jet configurations, that is, quark-antiquark pairs in which one of the fermions -- the would-be struck quark in the Breit frame -- carries most of the longitudinal momentum of the virtual photon. We show that physically meaningful jet definitions in DIS are such that the effective axis of the jet sourced by the struck quark is controlled by its virtuality rather than by its transverse momentum. For such jet definitions, we show that the next-to-leading order (NLO) cross-section admits factorisation in terms of the (sea) quark transverse momentum dependent (TMD) distribution, which in turn satisfies a universal DGLAP and Sudakov evolution
The DAMIC-M Low Background Chamber
No full textInternational audienceThe DArk Matter In CCDs at Modane (DAMIC-M) experiment is designed to search for light dark matter (m<10 GeV/c) at the Laboratoire Souterrain de Modane (LSM) in France. DAMIC-M will use skipper charge-coupled devices (CCDs) as a kg-scale active detector target. Its single-electron resolution will enable eV-scale energy thresholds and thus world-leading sensitivity to a range of hidden sector dark matter candidates. A DAMIC-M prototype, the Low Background Chamber (LBC), has been taking data at LSM since 2022. The LBC provides a low-background environment, which has been used to characterize skipper CCDs, study dark current, and measure radiopurity of materials planned for DAMIC-M. It also allows testing of various subsystems like readout electronics, data acquisition software, and slow control. This paper describes the technical design and performance of the LBC
Relationships between absorbed dose and proton energy with bremsstrahlung spectra for in vivo dosimetry of preclinical hadrontherapy
No full textInternational audienceContext: The ARRONAX cyclotron preclinical platform was upgraded to enable irradiations of mice with 70 MeV proton beams [1]. Currently, radiochomic films are used for online comparison with the simulated dose distribution after the irradiation but do not provide online verification. Hence, this study proposes to use the bremsstrahlung X-rays emitted by the medium as an in vivo dosimetry method. Previous studies have demonstrated the feasibility of using the bremsstrahlung yield to monitor the delivered dose at the entrance of a several-mm-thick PMMA phantom using a silicon drift detector SDD, with maximal intrinsic efficiency on the range 1-10 keV [2]. In addition, Ralite et al. have shown the yield's dependence on the beam energy and, therefore, the possibility of monitoring the incident beam energy.Material and Methods: In this work, an additional CdTe detector was used to detect X-ray energy up to 100 keV to access a broader spectrum, enabling a precise quantification of the main components of the bremsstrahlung, the Quasi Free Electron Bremsstrahlung (QFEB) (up to 37 keV for 70 MeV protons) and the Secondary Electron Bremsstrahlung (SEB) (mainly under 100 keV). Several calibrated tissue substitute cylinders (solid water, breast, lungs, bone - Gammex-RMI, WI, USA) were irradiated to investigate the spectrum dependencies on medium density and effective atomic number with proton energy. The information on dose and energy have been simulated with the code Monte Carlo GATE. The diameter of the cylinders is 28 mm, mimicking the mouse size, and the beam spot was 10 mm. The cylinders were positioned on a motorized translational axis in the beam propagation direction, and the detectors were shielded with lead to scan in depth by 5 mm slices.Results: Spectra at different depths and in various materials were acquired with both detectors. The method's sensitivity to dose was studied, and despite medium auto-attenuation, the bremsstrahlung X-rays were detected even in the Bragg peak region. Moreover, several characteristics of the bremsstrahlung spectrum (mean energy, FWHM, etc.) were studied to establish a direct link with the beam energy in the medium and its chemical composition.Conclusion and perspectives: This work is a comprehensive experimental study of bremsstrahlung spectra dependencies, for preclinical in vivo dosimetry verification. Analytical and Monte Carlo simulations will be used to optimize experimental set-up and to provide information on absorbed dose maps in mice, in relation to bremsstrahlung spectra, allowing the online comparison with treatment planning in a preclinical context.[1] M. Evin et al.,« Methodology for small animals targeted irradiations at conventional and ultra-high dose rates 65 MeV proton beam », Physica Medica, vol. 120, p. 103332, avr. 2024, doi: 10.1016/j.ejmp.2024.103332.[2] F. Ralite et al., « Bremsstrahlung X-rays as a non-invasive tool for ion beam monitoring », NIM-B, vol. 500-501, p. 76-82, août 2021, doi: 10.1016/j.nimb.2021.05.013