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Form Factors from Light-Cone Sum Rules with -Baryon Distribution Amplitudes
No full textInternational audienceWe compute the transition form factors using light-cone sum rules based on -baryon distribution amplitudes, including contributions up to twist--6. The analysis is performed for pseudoscalar, vector, and axial-vector currents and for different choices of the interpolating current. We find that only the pseudoscalar interpolating current leads to numerically stable and phenomenologically viable form factors. The resulting form factors are parametrised using a -expansion and applied to the rare decay , yielding predictions for branching ratios in the low- region
First evidence of the decay
No full textInternational audienceThe first search for the decay in the range is performed using data from proton-proton collisions collected by the LHCb experiment at centre-of-mass energies of 7, 8, and 13 TeV, corresponding to an integrated luminosity of 9 fb. The photons are reconstructed through their conversion into an electron-positron pair, which significantly improves the mass resolution of the reconstructed decays with respect to decays with an unconverted photon. A signal excess with a significance of 3.5 standard deviations is measured, constituting the first experimental evidence for this decay. In the range , the ratio between the branching fractions of the signal decay and the favoured decay is measured to be where the first uncertainty is statistical and the second is systematic. This measurement is consistent with the value predicted in the Standard Model. In the range , the ratio is measured
Characterization of the quantum state of top quark pairs produced in proton-proton collisions at = 13 TeV using the beam and helicity bases
No full textInternational audienceMeasurements of the spin correlation coefficients in the beam basis are presented for top quark-antiquark () systems produced in proton-proton collisions at = 13 TeV collected by the CMS experiment in 20162018, and corresponding to an integrated luminosity of 138 fb. The system is reconstructed from final states containing an electron or muon, and jets. Together with the previously reported results in the helicity basis, these measurements are used to decompose the system into the Bell and spin eigenstates in various kinematic regions. The spin correlation coefficients are also used to evaluate properties of the quantum state, such as the purity, von Neumann entropy, and entanglement. All results are consistent with standard model predictions
Influence of Radiation and AC Coupling on Time Performance of Analog Pixels Test Structures in 65 nm CMOS technology
No full textInternational audienceMonolithic Active Pixel Sensors (MAPS) in advanced CMOS imaging technologies are key to next-generation tracking systems for high-energy physics, where radiation hardness and precise vertex reconstruction are essential. As part of the ALICE ITS3 R&D program in synergy with the CERN R&D, we evaluated the performance of the Analog Pixel Test Structures (APTS) fabricated in the TPSCo 65 nm CMOS imaging process. The prototypes employ 10 um pitch pixels with a fast operational amplifier-based buffering stage at the output, enabling direct characterization of intrinsic sensor response. Beam tests with minimum ionizing particles assessed the timing and charge collection of DC- and AC-coupled designs, including devices exposed to 10^14 NIEL and 10^15 NIEL non ioninsing energy loss. DC-coupled sensors demonstrated stable performance, maintaining time resolution lower than 70 ps and >99% detection efficiency up to 10^15 NIEL. AC-coupled sensors demonstrated a wide operational margin, with efficiencies above 99% for clusterization thresholds below 150 electrons. Even though the AC coupling allows higher reverse bias than DC-coupled sensors, the reduced signal amplitude lowers the signal-to-noise ratio, increasing the jitter contribution. At high reverse bias, the AC-coupled sensors achieve time resolutions comparable to the DC-coupled version, demonstrating the viability of both approaches. These results also suggest that combining the low capacitance of DC-coupled designs with the high-bias capability of AC coupling could further enhance time resolution. These results confirm the suitability of 65 nm MAPS for future collider detectors requiring high radiation tolerance, efficiency, and timing precision
Testable Inverse Seesaw Motivated from a High Quality QCD Axion
No full textInternational audienceThe QCD axion remains one of the most compelling solutions to the strong CP problem. Meanwhile, the type-I seesaw mechanism offers an elegant explanation for the lightness of the observed neutrino masses; however, its extremely heavy Majorana states place it far beyond experimental reach. Low-scale alternatives such as the inverse seesaw improve testability but typically lack a strong theoretical motivation. In this paper we bridge this gap by showing that gauging the discrete symmetry -motivated by the internal structure of the Standard Model-naturally yields a QCD axion with a high-quality Peccei-Quinn symmetry solving the strong CP problem, while simultaneously enforcing the field content and hierarchy required for a natural inverse seesaw. The resulting model is highly predictive and has the potential to be fully tested by future experiments. Beyond addressing the strong CP problem and the origin of neutrino masses, our scenario also contains a viable dark-matter candidate and offers potential mechanisms for generating the baryon asymmetry of the Universe
Assessment of the tritium analysis performance of a nonylphenol-ethoxylate-free liquid scintillator by interlaboratory comparison
No full textInternational audienceWith a view to using liquid scintillators compliant with the REACH (Registration, Evaluation, Authorisation and Restriction of Chemicals) regulations, some laboratories have expressed an interest in testing the ProSafe LT+ , a liquid scintillator without nonylphenol-ethoxylates (NPE). In order to evaluate the impact of using this new liquid on the analysis results, the CETAMA consortium organised two interlaboratory comparisons. Two ranges of tritium activity were selected to meet the needs of environmental and waste monitoring. 23 laboratories took part in these exercises, comparing results obtained with Prosafe LT+ to those obtained with NPE-containing liquid scinitllators. From the results it was seen that the background and the background noise obtained with the nonylphenol-ethoxylates-free liquid scintillator are not significantly different from that of the usual liquid scintillator, whether for the waste or environmental domain, over short (15 min) or long (200 min) counting times. Furthermore, the decision threshold and the detection limit values estimated with ProSafe LT+ were no different from those of usual scintillators. However, for the measurement of samples, and particularly for samples with a tritium activity above 15 Bq/kg, the ProSafe LT+ presented a reduced measurement quality compared to the nonylphenol-ethoxylates-containing LS i.e. the measurement uncertainty obtained with ProSafe LT+ is systematically higher. In light of the results obtained through this study, the authors recommend the use of the ProSafe LT+ with the proviso that the deterioration in measurement uncertainty be taken into account and found to be compatible with a laboratory’s individual needs
Pure rare earth oxides as high-performance gamma, neutron, and charged particles shielding materials: A comparative study of Ho2O3, Er2O3, Yb2O3, and Y2O3
No full textInternational audienceWe investigated the ionizing radiation shielding properties of four prepared rare-earth element oxide samples. The Rietveld refinement of the X-ray diffraction (XRD) patterns of all studied samples confirmed a pure cubic structure with the Ia-3 space group. Various attenuation parameters were assessed and analyzed using Phy-X and SRIM software within the energy range of 5 keV-15 MeV. The parameters evaluated included several shielding metrics such as the linear attenuation coefficient (mu), mass attenuation coefficient (mu m), mean free path (A), half-value layer (A1 2 range. The results show that all oxides demonstrate excellent attenuation properties. Specifically, at 15 keV, mu ranged from 780.5 to 966.7 cm-1, while mu m ranged from 92.809 to 104.971 cm2/g, and 21/2 values were near 0.001 cm for most oxides, indicating outstanding performance compared to conventional shielding materials. Furthermore, at lower energy levels (0.005-0.2 MeV), the RPE consistently remained high (nearly 100 %) for most of the oxide samples, illustrating effective shielding performance. In addition, the results show that the oxides exhibit a high neutron removal cross-section (ER), ranging from 0.128 to 0.137, compared to conventional shielding materials. Conversely, protons exhibited efficient charge collection at energies below 0.1 MeV, whereas alpha particles showed similar behavior near 0.7 MeV. Moreover, protons possessed a greater penetration depth than alpha particles. These findings support the conclusion that the investigated oxide-based samples serve as effective materials for radiation shielding applications. ), radiation protection efficiency (RPE), transmission factor (TF%), stopping power-dE dx , and io
New opportunities for rare charm from decays
No full textInternational audienceWe analyze the potential of rare charm decays as probes of new physics at a high-luminosity flavor facility operating at the pole, such as the FCC-ee or CEPC. In particular, we identify clean null-test observables in and in polarized decays with . Complementarity with the LHC and HL-LHC flavor programs arises from the characteristic features of a Tera- environment: the capability to study missing-energy modes and charm production with significant polarization. We improve the theoretical description of decays and work out the phenomenology of polarization-induced null-test observables in decays. In regions of dilepton mass near the resonance, polarization asymmetries can reach for muons and for electrons times the polarization. We also point out synergies between the dineutrino and the dilepton modes using the SMEFT framework of heavy new physics. Using the IDEA detector concept at FCC-ee, we find in simulation studies that dineutrino branching fractions as low as can be probed, which reaches well into the parameter space of new physics, and also allows for discrimination of lepton flavor structures. Furthermore, the measurement of asymmetries in at will be possible. Similar sensitivities are expected for dielectron final states, although robust predictions will require further dedicated studies
Digital electronics upgrade of the INDRA <math altimg="si2.svg" display="inline" id="d1e354"><mrow><mn>4</mn><mi>π</mi></mrow></math> charged particle detection array and resulting performance improvements
No full textInternational audienceINDRA is a 4π charged particle detection array in use since 1993 for the study of nuclear collisions at bombarding energies from a few 10s to a few 100s of MeV/nucleon. Originally equipped with custom electronics using the VXI standard, the entire acquisition system was recently upgraded to a fully digital system using commercially-available modules supplied by mesytec GmbH & Co. KG. At the same time, both low and high voltage supplies and all cabling and signal routing outside of the reaction chamber have also been replaced. The new electronics were used for the first time in 2022 in an experiment at GANIL coupling INDRA with 12 blocks of FAZIA telescopes placed at forward angles. The full details of the upgraded system, and the resulting improvements in performance, stability, dead time and identification capabilities are presented in this article
In-beam angular distribution and linear polarization measurements with GRETINA using a simple energy-ordering approach
No full textInternational audienceAngular distribution and linear polarization measurements are powerful tools for inferring the spins and parities of nuclear levels. In this work, the performance of the Gamma-Ray Energy Tracking In-beam Nuclear Array (GRETINA) as a Compton polarimeter was characterized in a fusion-evaporation reaction experiment using a simple energy-ordering approach for the interaction points assigned in the signal decomposition process. A variety of multipolarities and characters for γ-ray transitions in the reaction products 25Mg, 25Na, and 22Ne, formed from fusion-evaporation of an 18O beam on a 9Be target, were examined. The experimental angular distributions and linear polarization asymmetries were consistent with predictions using the theoretical formalism accounting for the Lorentz boost