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Martinez-Cañadas, M. A., Porras, I., Macias, M., Praena, J., Fontana, C. L., Bonaldi, C., et al. (2026). First experimental validation of the MgF2 core of the Beam Shaping Assembly from the NeMeSiS project for Boron Neutron Capture Therapy. Radiat. Phys. Chem., 246, 113969–10pp.
Abstract: A Beam Shaping Assembly model was proposed by the Neutrons for Medicine and Scientific applications project for its application to Boron Neutron Capture Therapy. The first experimental test of the core moderator was performed at the MONNET facility at the Joint Research Centre in Geel, Belgium. To this end, the conducted experiment had three main goals: first, an energy and angular characterization of the 7Li(p,n) at 2.1 MeV; second, the validation of the magnesium fluoride (MgF2) total cross-section following transmission measurements through thin samples; third, the measurement of the moderation capabilities of MgF2 after irradiating several blocks of the material. All measurements used a lithium glass detectors with the time-of-flight technique. Monte Carlo simulations were done to calculate the necessary corrections, as well as several checks and further analysis. In this work we illustrate the chronology in all these sequential steps.
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LHCb Collaboration(Aaij, R. et al), Fernandez Casani, A., Jaimes Elles, S. J., Jashal, B. K., Libralon, S., Lucio Martinez, M., et al. (2026). Branching fraction measurement of the Λ → pμ- (v)over-barμ decay. J. High Energy Phys., 04(4), 096–27pp.
Abstract: A measurement of the branching fraction for the decay Lambda -> p mu(-) (v) over bar (mu) is presented using pp collision data collected by the LHCb experiment at a centre-of-mass energy of 13 TeV. The analysis is based on data recorded between 2016 and 2018, corresponding to an integrated luminosity of 5.4 fb(-1). The result is obtained using Lambda -> p mu(-) decays as a normalisation channel. The measured branching fraction is B(Lambda -> p mu(-) (v) over bar (mu)) = (1.462 +/- 0.016 +/- 0.100 +/- 0.011) x 10(-4), where the uncertainties are statistical, systematic, and due to the limited knowledge of the normalisation mode branching fraction, respectively. This result improves the precision of the branching fraction measurement by a factor of two compared to the previous best measurement and sets a more stringent bound on lepton flavour universality in s -> u quark transitions. It is consistent with previous measurements, and the extracted lepton flavour universality test observable, R-mu e = Gamma(Lambda -> p mu(-)(v) over bar (mu))/Gamma(Lambda -> pe(-)(v) over bar (e)) = 0.175 +/- 0.012, agrees with the Standard Model prediction.
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Martinez-Cañadas, M. A., Porras, I., Macias, M., Praena, J., Fontana, C. L., Bonaldi, C., et al. (2026). Measurement of neutron transmission of Mg and MgF2 at MONNET (JRC-Geel) with fine multi-scattering corrections. Appl. Radiat. Isot., 234, 112638–10pp.
Abstract: Neutron-transmission measurements through samples of magnesium fluoride (MgF2) and pure magnesium were performed to obtain neutron resonance parameters from all involved isotopes, 19F and 24-26Mg, in the range from 10 to 360 keV. Lithium-glass detectors were used in conjunction with the neutron Time of Flight technique. The measurement campaign was performed at the MONNET fast-neutron source of the European Commission Joint Research Centre (JRC-Geel, Belgium). Highly precise corrections for multiple scattering were calculated using a sophisticated iterative method based on Monte Carlo simulations with MCNP6.3 code, accounting for the effects of the experimental setup. With the SAMMY code, an R-Matrix analysis of the experimental data was performed. The extracted resonance widths, spins, and parities, as well as the limitations of the method, are carefully discussed.
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LHCb Collaboration(Aaij, R. et al), Fernandez Casani, A., Jaimes Elles, S. J., Jashal, B. K., Libralon, S., Lucio Martinez, M., et al. (2026). Search for KS(L)0 → π+ π- μ+ μ- decays at LHCb. Phys. Rev. D, 113(7), 072001–13pp.
Abstract: A search for K-S(L)(0) -> pi(+) pi(-) mu(+) mu(-) decays is performed using proton-proton collision data collected by the LHCb experiment at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 5.4 fb(-1). No K-S(L)(0) -> pi(+) pi(-) mu(+) mu(-) signals are found and upper limits are set for the first time on the branching fractions B(K-S(0) -> pi(+) pi(-) mu(+) mu(-)) < 1.4 x 10(-9) and B(K-L(0) -> pi(+) pi(-) mu(+) mu(-)) < 6.6 x 10(-7), at the 90% confidence level.
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Pellumaj, J. et al, Valiente-Dobon, J. J., & Perez-Vidal, R. M. (2026). Development of deformed intruder structures along the N=50 magic number: Insights from 83Se. Phys. Lett. B, 876, 140432–7pp.
Abstract: The 83Se nucleus was studied in the context of shape coexistence employing a 82Se(d,p)83Se reaction performed in inverse kinematics with the GALILEO-II + SPIDER setup to reach the desired selectivity on the reaction channel of interest via y-particle coincidences. The lifetimes of the 1/2+ 540-keV and 3/2+3 1100-keV low-lying intruder states of 83Se were measured for the first time by employing the Recoil Distance Doppler Shift and the Doppler Shift Attenuation Method. The deduced transition probabilities, together with the mixing ratios obtained from a separate neutron-capture experiment performed at ILL with the FIPPS array, are compared and discussed in the framework of shell-model calculations performed with the PFSDG-U Hamiltonian. Large transition probabilities of hundreds of e2fm4 were found for the E2 decays of the states built on top of the intruders, pointing to the development of quadrupole collectivity and large deformation in the proximity of N = 50 shell closure.
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