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Search for jet quenching effects in high-multiplicity pp collisions at = 13 TeV via di-jet acoplanarity
No full textInternational audienceThe ALICE Collaboration reports a search for jet quenching effects in high-multiplicity (HM) protonproton collisions at = 13 TeV, using the semi-inclusive azimuthal-difference distribution of charged-particle jets recoiling from a high transverse momentum (high-) trigger hadron. Jet quenching may broaden the distribution measured in HM events compared to that in minimum bias (MB) events. The measurement employs a -differential observable for data-driven suppression of the contribution of multiple partonic interactions, which is the dominant background. While azimuthal broadening is indeed observed in HM compared to MB events, similar broadening for HM events is observed for simulations based on the PYTHIA 8 Monte Carlo generator, which does not incorporate jet quenching. We elucidate the origin of the broadening by comparing biases induced by HM selection in the data and simulations, and discuss its implications for the study of jet quenching in small collision systems
Search for Daily Modulation of MeV Dark Matter Signals with DAMIC-M
No full textInternational audienceDark Matter (DM) particles with sufficiently large cross sections may scatter as they travel through Earth's bulk. The corresponding changes in the DM flux give rise to a characteristic daily modulation signal in detectors sensitive to DM-electron interactions. Here, we report results obtained from the first underground operation of the DAMIC-M prototype detector searching for such a signal from DM with MeV-scale mass. A model-independent analysis finds no modulation in the rate of 1 events with periods in the range 1-48 h. We then use these data to place exclusion limits on DM in the mass range [0.53, 2.7] MeV/c interacting with electrons via a dark photon mediator. Taking advantage of the time-dependent signal we improve by 2 orders of magnitude on our previous limit obtained from the total rate of 1 events, using the same data set. This daily modulation search represents the current strongest limit on DM-electron scattering via ultralight mediators for DM masses around 1 MeV/c
Freezing-In Gravitational Waves
No full textInternational audienceThe thermal plasma in the early universe produced a stochastic gravitational wave (GW) background, which peaks today in the microwave regime and was dubbed the cosmic gravitational microwave background (CGMB). In previous works only single graviton production processes that contribute to the CGMB have been considered. Here we also investigate graviton pair production processes and show that these can lead to a significant contribution if the maximum temperature of the universe in units of Planck mass divided by the internal coupling in the heat bath is large enough. As the dark matter freeze-in production mechanism is conceptually very similar to the GW production mechanism from the primordial thermal plasma, we refer to the latter as "GW freeze-in production". We also show that quantum gravity effects arising in single graviton production are smaller than the leading order result by a factor of the square of the ratio between the maximum temperature and the Planck mass. In our work we explicitly compute the CGMB spectrum within a scalar model with quartic interaction
Production cross section measurements of the natPd(α,x)111Ag reaction
No full textInternational audienceThe radionuclides used in targeted radionuclide therapy emit charged particles, such as α, β- and Auger electron, that makes possible the delivery of a significant dose to the tumour cells while sparring the healthy tissues surrounding them. The radioisotope 111Ag (t1/2 = 7.45 days, Emax,β- = 1.04 MeV) is a β- emitter that is promising for this kind of application. Its low energy β- have a medium tissue penetration of average 1.8 mm which enables the targeting of medium tumours. Additionally, its γ-rays at 245 keV (1.3 %) and 342 keV (6.7 %) are well suited for SPECT imaging which is helpful for monitoring more precisely the in vivo dose delivered. Several routes have been studied to produce 111Ag either with research reactors, cyclotrons or photonuclear reactions. The use of helium ions (alpha route) has not been studied yet. Only two teams have made measurements for the production cross sections of the reaction natPd(α,x)111Ag and none for 110Pd(α,x)111Ag. For this reason, several measurements for natPd(α,x)111Ag have been performed at the GIP Arronax with an α beam of 68 MeV to get experimental data above 50 MeV to better define the peak region between 40 and 50 MeV. The “stacked-foils” method has been used during our experiments. The intensity of the beam has been monitored through the natAl(α,x)24Na nuclear reaction. A HPGe detectors was used to perform the γ-spectrometry of each foil: short acquisition were done directly after the irradiation to measure 110m,110Pd and longer ones days after to measure 111Ag. The experimental data obtained will be confronted with the literature and with TENDL 2023. The indirect production of 111Ag with 110m, 110Pd will also be studied to try to assess their contribution
EPOS4: New theoretical concepts for modeling proton-proton and ion-ion scattering at very high energies
No full textInternational audienceWe discuss the new concepts behind EPOS4, a new theoretical framework for modeling hadronic interactions at ultrarelativistic energies. It amounts to reconciling a multiple scattering picture (with parallel scatterings) and factorization, the standard tool for high-energy scattering
PRODUCTION DE PLOMB-203 DÉDIÉE À L'IMAGERIE MÉDICALE
No full textInternational audienceLe plomb-212 (t1/2 = 10,6 h) et le plomb-203 (t1/2 = 51,9 h) peuvent être utilisés comme une paire d'isotopes pour des applications théranostiques en médecine nucléaire. Pb-212 peut être obtenu à partir de la décroissance du thorium-232 et est utilisé pour l'alpha-thérapie [1] alors que Pb-203 peut être produit par irradiation de protons ou de deutérons sur une cible de thallium et permet la tomographie à émission monophotonique (TEMP).La production actuelle de Pb-203 utilise des Tl naturels, Tl-203 enrichi ou Tl-205 enrichi bombardés par un faisceau de protons à une énergie en-dessous de 24 MeV. Cette énergie ne peut être délivrée au GIP ARRONAX. Nous avons alors examiné d’autres voies de production et Pb-203 peut être produit en utilisant un faisceau de deutérons à une énergie de 31 MeV [2] [3]. Pour produire Pb-203 à l’échelle industrielle, un dépôt de Tl-205 enrichi d’une surface de 14 cm2 et d’épaisseur de 40 µm est fabriqué par une technique appelée électrodéposition. C’est une technique qui permet de réduire les cations Tl+ en Tl sur la plaque en or en appliquant les courants entre deux électrodes. Pendant le tir, la cible est inclinée d'un angle de 15° afin d’optimiser la production et elle est refroidie grâce à la circulation de l’eau. Après le tir, la cible est envoyée à l’enceinte blindée pour réaliser les séparations chimiques. Deux résines appelés résine Pb sont utilisées pour à la fois recycler la matière première, Tl-205, et obtenir un produit purifiée contenant Pb-203 dans une solution d’acétate d’ammonium 1 mol/l à pH 5. Depuis septembre 2023, Pb-203 est produit une fois par mois pour une durée de tir de 1h à 1h30 et à une intensité de 60 μA à 70 µA. Au temps de calibration (TC) qui est fixé 2 jours après le tir, la pureté de Pb-203 était supérieure à 99,5% et toutes les radio-impuretés étaient en dessous de la limite de détection de γ-spectrométrie, à l'exception de Pb-201 (moins de 0,5%). En outre, au TC, en moyenne 1500 MBq d'activité de Pb-203 était produite. Cette activité peut être augmentée en augmentant la durée de tir. Le rendement de la séparation chimique de Pb-203 variait de 80% à 90%. Dans la solution purifiée de Pb-203, tous les métaux qui sont susceptibles d’être présents dans la solution (Tl, Pb, Fe, Ni, Au) étaient en dessous de la limite de détection de ICP-OES. Parallèlement, le rendement de la récupération de Tl-205 était supérieur à 90%, ce qui lui permet de recycler plusieurs mois après la décroissance complète de Tl-202. En outre, le radiomarquage a été testé avec le peptide DOTATATE utilisant 250 MBq de Pb-203 par 100 μg de peptide, comparable aux conditions des essais cliniques. Les premiers résultats ont montré que la pureté radiochimique à la fin de la synthèse était de 99% et que la stabilité de l'environnement réactif après 12 heures, 24 heures et 96 heures était supérieure à 98%.Toutes ces valeurs sont prometteuses pour la production à l’échelle industrielle de Pb-203 de haute pureté, et les résultats seront discutés au cours de ma présentation. Notre spécification du produit Pb-203 sera également montrée.[1]B. L. McNeil et al., “Production, purification, and radiolabeling of the 203Pb/212Pb theranostic pair,” EJNMMI radiopharm. chem., vol. 6, no. 1, p. 6, Feb. 2021, doi: 10.1186/s41181-021-00121-4.[2]T. Sounalet et al., “Manufacture of Tl targets by electrodeposition for the study of excitation functions of 203Pb,” EPJ Web Conf., vol. 285, p. 09001, 2023, doi: 10.1051/epjconf/202328509001.[3]T. Sounalet, A. Guertin, F. Haddad, K. Kamalakannan, and E. Nigron, “Production of 203Pb from enriched 205Tl using deuteron beams,” Applied Radiation and Isotopes, p. 111190, Jan. 2024, doi: 10.1016/j.apradiso.2024.111190
Charged-particle production as a function of the relative transverse activity classifier in pp, pPb, and PbPb collisions at the LHC
No full textInternational audienceMeasurements of charged-particle production in pp, pPb, and PbPb collisions in the toward, away, and transverse regions with the ALICE detector are discussed. These regions are defined event-by-event relative to the azimuthal direction of the charged trigger particle, which is the reconstructed particle with the largest transverse momentum () in the range GeV. The toward and away regions contain the primary and recoil jets, respectively; both regions are accompanied by the underlying event (UE). In contrast, the transverse region perpendicular to the direction of the trigger particle is dominated by the so-called UE dynamics, and includes also contributions from initial- and final-state radiation. The relative transverse activity classifier, , is used to group events according to their UE activity, where is the charged-particle multiplicity per event in the transverse region and is the mean value over the whole analysed sample. The energy dependence of the distributions in pp collisions at , 5.02, 7, and 13 TeV is reported, exploring the Koba-Nielsen-Olesen (KNO) scaling properties of the multiplicity distributions. The first measurements of charged-particle spectra as a function of in the three azimuthal regions in pp, pPb, and PbPb collisions at TeV are also reported. Data are compared with predictions obtained from the event generators PYTHIA 8 and EPOS LHC. This set of measurements is expected to contribute to the understanding of the origin of collective-like effects in small collision systems (pp and pPb)
Measurements of jet quenching using semi-inclusive hadron+jet distributions in pp and central PbPb collisions at TeV
No full textInternational audienceThe ALICE Collaboration reports measurements of the semi-inclusive distribution of charged-particle jets recoiling from a high transverse momentum (high ) charged hadron, in pp and central PbPb collisions at center of mass energy per nucleonnucleon collision TeV. The large uncorrelated background in central PbPb collisions is corrected using a data-driven statistical approach, which enables precise measurement of recoil jet distributions over a broad range in and jet resolution parameter . Recoil jet yields are reported for , 0.4, and 0.5 in the range GeV and , where is the azimuthal angular separation between hadron trigger and recoil jet. The low reach of the measurement explores unique phase space for studying jet quenching, the interaction of jets with the quark-gluonnplasma generated in high-energy nuclear collisions. Comparison of distributions from pp and central PbPb collisions probes medium-induced jet energy loss and intra-jet broadening, while comparison of their acoplanarity distributions explores in-medium jet scattering and medium response. The measurements are compared to theoretical calculations incorporating jet quenching
K(892) resonance production in PbPb collisions at = 5.02 TeV
No full textInternational audienceThe production of K(892) meson resonance is measured at midrapidity ( GeV/, consistent with measurements for other light-flavored hadrons. The smallest values are observed in most central collisions, indicating larger energy loss of partons traversing the dense medium
Sydnone-based prosthetic groups for radioiodination
No full textInternational audienceThe potential of Strained-Promoted Sydnone-Alkyne Cycloaddition (SPSAC) for radioiodination was evaluated with model cyclooctyne-conjugated peptides. Starting with a series of sydnones with varying N 3 and C 4 substitution, a preliminary kinetic study with nonradioactive iodinated compounds highlighted the superiority of an arylsydnone substituted by a chlorine atom in C 4 position. Interestingly, reaction rate up to 11 times higher than using an azide was achieved with the best system. Access to 125 I-labelled sydnones was granted with high efficiency from arylboronic acid precursors by copper catalyzed nucleophilic substitution. Application of SPSAC on the model peptide in radiotracer conditions showed the same trend than in non-radioactive kinetic study and complete reactions could be achieved within less than an hour for the best systems. These results are favorable for use in the production of radiopharmaceuticals with heavy halogens and increase the diversity of available bioorthogonal reaction for nuclear imaging and therapy