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Charmonium production in a thermalizing heat bath
No full textInternational audienceUsing the Remler formalism for the creation of composed particles, we study charmonium production both in thermalized and thermalizing boxes, which contain charm and anticharm quarks. The thermalizing box studies include the lowering of the box temperature, the spatial diffusion of charm and anticharm quarks, which are initially confined in the central region, as well as the combination of both, what imitates heavy-ion collisions. Comparing numerical and analytical results we demonstrate that the rate of the original Remler formalism has to be supplemented by two rates to obtain, for , results, which are consistent with the statistical model predictions: i) a rate, which takes into account the temperature dependence of the Wigner density of the quarkonium during the expansion and, in the case that a heavy quark potential is not implemented in the Monte Carlo approach, ii) a rate which comes from the change of the relative distance between the heavy quark and antiquark. These results provide the basis for future applications of the Remler formalism to heavy-ion collisions
Transverse emittance measurement in 2D and 4D performed on a Low Energy Beam Transport line: benchmarking and data analysis
No full textInternational audience2D and 4D transverse phase-space of a low-energy ion-beam is measured with two of the most common emittance scanners. The article covers the description of the installation, the setup, the settings, the experiment and the benchmark of the two emittance meters. We compare the results from three series of measurements and present the advantages and drawbacks of the two systems. Coupling between phase-space planes, correlations and mitigation of deleterious effects are discussed. The influence of background noise and aberrations of trace-space figures on emittance measurements and RMS calculations is highlighted, especially for low density beams and halos. A new data analysis method using noise reduction, filtering, and reconstruction of the emittance figure is described. Finally, some basic concepts of phase-space theory and application to beam transport are recalled
New experimental bremsstrahlung cross-section for light ion beams up to 60 MeV and comparison to theoretical models
No full textInternational audienceRecent works focused on bremsstrahlung radiation as a non-invasive tool for monitoring proton beams used in radiobiology (>20 MeV). In order to study the validity of theoretical models of bremsstrahlung cross sections, bremsstrahlung X-rays between 4 keV and 15 keV coming from a carbon target irradiated by proton beams in the energy range from 15 MeV to 50 MeV were measured by a silicon drift detector. The obtained data vary from 10 mb keV−1 to 1000 mb keV−1 and fit well the literature and with theoretical model calculation. These results strongly support that bremsstrahlung X-rays models can be used to develop promising online tools for proton beam monitoring
Studies and optimization of scintillation light measurements for the development of the 3-gamma medical imaging XEMIS2 liquid xenon Compton camera
No full textInternational audienceWe report the studies and optimization of scintillation light measurements in an updated version of the XEMIS1 prototype for the development of the XEMIS2 camera. A novel monolithic liquid xenon Compton camera, named XEMIS2 (XEnon Medical Imaging System), attempts to achieve low-activity small-animal imaging using the 3-gamma imaging technique. This emerging detector relies on the time projection chamber technique: it will be able to perform a simultaneous detection of the three γ-rays emitted by a specific radionuclide, such as scandium-44, and to produce a good quality image with a remarkable diminution of radiopharmaceutical activity at the same time. Vacuum Ultraviolet (VUV) scintillation light and ionization charge carriers generated from the recoiling particles within the detector are detected and used to reconstruct the interaction position and deposited energy. A cost-effective self-triggering scintillation signal read-out and data acquisition (DAQ) system has been developed to achieve a continuous data read-out with negligible electronics dead time. The DAQ prototype has been installed and qualified in an updated version of the XEMIS1 detector. It reaches the performance specifications in scintillation light measurements. Moreover, scintillation signals can also be used for the virtual segmentation of the monolithic detection volume through the matching algorithm of the scintillation and ionization signals based on the Light Collection Map (LCM). This spatial pre-localization of the physical events, called the virtual fiducialization of the active volume, is used to lower the detector occupancy rate when the administered activity is increased to lessen the examination time. The XEMIS1 experimental LCMs indicate that each PMT owns an individual field of view so as to segment the active volume virtually. The preparation work for the XEMIS2 camera operation has been completed in the updated XEMIS1 detector while the XEMIS2 scintillation light measurement system is under commissioning in Nantes Centre Hospitalier Universitaire. •The XEMIS2 camera oriented to the whole-body small animal 3-gamma medical imaging is presented.•The XEMIS2 system is a monolithic liquid xenon Compton camera with a 24 cm axial field of view.•A cost-effective 16-channel self-triggering scintillation signal front-end read-out electronics named XSRETOT is reported.•The XEMIS1 experimental light collection maps can be used for the virtual segmentation of the monolithic detection volume
Back-to-back inclusive di-jets in DIS at small : Gluon Weizsäcker-Williams distribution at NLO
No full textInternational audienceIn JHEP 11 (2022) 169, we performed the first complete computation of the back-to-back inclusive di-jet cross-section in Deeply Inelastic Scattering (DIS) at small to next-to-leading order (NLO) in the Color Glass Condensate effective field theory (CGC EFT). We demonstrate here that for di-jets with relative transverse momentum and transverse momentum imbalance , to leading power in , the cross-section for longitudinally polarized photons can be fully factorized into the product of a perturbative impact factor and the nonperturbative Weizsäcker-Williams (WW) transverse momentum dependent (TMD) gluon distribution to NLO accuracy. The impact factor can further be expressed as the product of a universal soft factor which resums Sudakov double and single logs in and a coefficient function given by a remarkably compact analytic expression. We show that in the CGC EFT the WW TMD satisfies a kinematically constrained JIMWLK renormalization group evolution in rapidity. This factorization formula is valid to all orders in for , where is the semi-hard saturation scale that grows with rapidity
Geochemical and mineralogical characterization of streams and wetlands downstream a former uranium mine (Rophin, France)
No full textInternational audienceThe geochemical distribution of U and associated major and trace elements (As, Li, Pb, Sr, Zn) was studied at the former Rophin U mine (Puy-de-Dôme, France). Three zones of contrasting radiological settings were identified and sampled: a background area (1000 nSv·h−1). Sediment and water samples were collected both in a streambed located in the background area and in the streambed downslope the former mining area, and a soil sample was collected in the wetland downslope. Using both sequential and selective chemical extractions, and quantifying also the chemical reservoirs of As, Li, Pb, Sr, and Zn, it could be concluded that, in the streams, U was mainly bounded to primary ore minerals (phosphates) that were transported through particulate transport. It was also bound, to a lower extent, to clays, Mn oxyhydroxides and organic matter, certainly due to the sorption of aqueous U originating from partial dissolution or leaching of primary ore materials. Ore minerals remaining stable in the stream sediments were certainly included in a quartz matrix and hence were not in accessible for dissolution. In the wetland soil, selective extractions evidenced that U was about evenly distributed between humid/fulvic acids and organic matter unaffected by NH4OH 1M
Exclusive and dissociative <math display="inline"><mi>J</mi><mo>/</mo><mi>ψ</mi></math> photoproduction, and exclusive dimuon production, in p-Pb collisions at <math display="inline"><mrow><msqrt><mrow><msub><mrow><mi>s</mi></mrow><mrow><mi>NN</mi></mrow></msub></mrow></msqrt><mo>=</mo><mn>8.16</mn><mtext> </mtext><mtext> </mtext><mi>TeV</mi></mrow></math>
No full textInternational audienceThe ALICE Collaboration reports three measurements in ultraperipheral proton-lead collisions at forward rapidity. The exclusive two-photon process γγ→μ+μ- and the exclusive photoproduction of J/ψ are studied. J/ψ photoproduction with proton dissociation is measured for the first time at a hadron collider. The cross section for the two-photon process of dimuons in the invariant mass range from 1 to 2.5 GeV/c2 agrees with leading-order quantum electrodynamics calculations. The exclusive and dissociative cross sections for J/ψ photoproductions are measured for photon-proton center-of-mass energies from 27 to 57 GeV. They are in good agreement with HERA results
Examination of how properties of a fissioning system impact isomeric yield ratios of the fragments
No full textInternational audienceThe population of isomeric states in the prompt decay of fission fragments—so-called isomeric yield ratios (IYRs)—is known to be sensitive to the angular momentum J that the fragment emerged with, and may therefore contain valuable information on the mechanism behind the fission process. In this work, we investigate how changes in the fissioning system impact the measured IYRs of fission fragments to learn more about what parameters affect angular momentum generation. To enable this, a new technique for measuring IYRs is first demonstrated. It is based on the time of arrival of discrete γ rays, and has the advantage that it enables the study of the IYR as a function of properties of the partner nucleus. This technique is used to extract the IYR of Te134, strongly populated in actinide fission, from the three different fissioning systems: Th232(n,f), U238(n,f), at two different neutron energies, as well as Cf252(sf). The impacts of changing the fissioning system, the compound nuclear excitation energy, the minimum J of the binary partner, and the number of neutrons emitted on the IYR of Te134 are determined. The decay code talys is used in combination with the fission simulation code freya to calculate the primary fragment angular momentum from the IYR. We find that the IYR of Te134 has a slope of 0.004±0.002 with increase in compound nucleus (CN) mass. When investigating the impact on the IYR of increased CN excitation energy, we find no change with an energy increase similar to the difference between thermal and fast fission. By varying the mass of the partner fragment emerging with Te134, it is revealed that the IYR of Te134 is independent of the total amount of prompt neutrons emitted from the fragment pair. This indicates that neutrons carry minimal angular momentum away from the fission fragments. Comparisons with the freya+talys simulations reveal that the average angular momentum in Te134 following U238(n,f) is 6.0ℏ. This is not consistent with the value deduced from recent cgmf calculations. Finally, the IYR sensitivity to the angular momentum of the primary fragment is discussed. These results are not only important to help understanding the underlying mechanism in nuclear fission, but can also be used to constrain and benchmark fission models, and are relevant to the γ-ray heating problem of reactors
HEPScore: A new CPU benchmark for the WLCG
No full textInternational audienceHEPScore is a new CPU benchmark created to replace the HEPSPEC06 benchmark that is currently used by the WLCG for procurement, computing resource pledges, usage accounting and performance studies. The development of the new benchmark, based on HEP applications or workloads, has involved many contributions from software developers, data analysts, experts of the experiments, representatives of several WLCG computing centres and WLCG site managers. In this contribution, we review the selection of workloads and the validation of the new HEPScore benchmark
Quarkonia dynamics in the Quark-Gluon Plasma with a quantum master equation
No full textInternational audienceWe study the dynamics of a single quark-antiquark pair in the Quark-Gluon Plasma (QGP) within the open quantum system framework. The dynamics are governed by coupled partial differential equations describing the evolution of the pair density operator in the singlet and octet color channels. We study both the charmonium and bottomonium system in one dimension, using a one-dimensional potential specifically developed for this study and tailored to capture as best as possible characteristics of a full three-dimensional potential. A first study of the suppression of bottomonia as function of the centrality, using EPOS4 temperature profiles for the QGP medium is presented