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Garcia Rivas, I., Fernandez Prieto, A., Vazquez Regueiro, P., Garcia Fernandez, D., Kögler, T., Römer, K., et al. (2025). Performance of a CeBr3 scintillator coupled to a photomultiplier tube with an active voltage divider under high bremsstrahlung fluences. J. Instrum., 20(11), P11016–25pp.
Abstract: Proton therapy lacks a standard method to verify the proton range during the treatments in the clinical routine. In this context, the monitoring of prompt gamma-rays in a coaxial geometry using a compact detector based on a CeBr3 scintillator coupled to a commercial photomultiplier tube (PMT) could lead to the identification of proton range deviations. Such detection system could be easily integrated in every treatment room. Although measuring in this geometry profits from an advantageous solid angle, the detector is also exposed to an extreme gamma-ray rate, of up to 10 Mcps. In this work, we present the first experimental performance evaluation for the proposed detector by irradiating it at very high bremsstrahlung rates at the gamma ELBE facility. Using a customized active voltage divider to supply voltage to the PMT, the detection system was able to sustain a photon rate higher than 12 Mcps without dead time while keeping gain drifts below 15% in the best configuration, and to achieve a sub-nanosecond time resolution.
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Molina, R., & Oset, E. (2025). Determination of off-shell ambiguities in correlation functions: Strategies to minimize them. Phys. Rev. D, 112(9), 096006–7pp.
Abstract: We face here the problem of uncertainties in correlation functions due to the freedom in the off-shell dependence of the wave functions or, equivalently, off-shell ambiguities in the scattering matrices. We make the study for the case of meson baryon interaction, choosing the K Lambda, K Sigma, and rjN coupled channels, which are related to the N*(1535) resonance, and the K+ K<overline>0 channel related to the a0(980) resonance. We find that, by using realistic interactions based on chiral dynamics, the uncertainties are small, of the order of 2-3%, but could be much bigger if other methods are used. However, our study shows the way to optimally overcome these uncertainties in the analysis of correlation functions, and we provide a series of recommendations for any general analysis.
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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. (2025). Three-pion Bose-Einstein correlations measured in proton-proton collisions. J. High Energy Phys., 08(8), 174–27pp.
Abstract: A study on the Bose-Einstein correlations for triplets of same-sign pions is presented. The analysis is performed using proton-proton collisions at a centre-of-mass energy of root s = 7TeV, recorded by the LHCb experiment, corresponding to an integrated luminosity of 1.0 fb(-1). For the first time, the results are interpreted in the core-halo model. The parameters of the model are determined in regions of charged-particle multiplicity. This measurement provides insight into the nature of hadronisation in terms of coherence, being consistent with the presence of coherent emission of pions.
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LHCb Collaboration(Aaij, R. et al), Fernandez Casani, A., Jaimes Elles, S. J., Jashal, B. K., Libralon, S., Martinez-Vidal, F., et al. (2025). Measurement of the branching fraction ratio RK at large dilepton invariant mass. J. High Energy Phys., 07(7), 198–36pp.
Abstract: A test of lepton universality between muons and electrons is performed using B+ -> K+ l(+)l(-) decays (where l = e, mu), in the dilepton invariant-mass-squared region above 14.3 GeV2/c(4). The data used for the measurement consists of beauty meson decays produced in proton-proton collisions, corresponding to an integrated luminosity of 9 fb(-1), collected by the LHCb experiment between 2011 and 2018. The ratio of branching fractions for B+ -> K+ mu(+)mu(-) and B+ -> K+ e(+)e(-) decays is measured to be R-K = 1.08(-0.09)(+0.11) (stat) (+0.04)(-0.04) (syst), which is consistent with the Standard Model prediction of unity. This constitutes the most precise test of lepton flavour universality using B+ -> K+ l(+)l(-) decays with dilepton invariant-mass-squared above the psi(2S) mass, whilst being the first of its kind at a hadron collider.
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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. (2025). Measurement of the Ωc0 and Ξc0 baryon lifetimes using hadronic b-baryon decays. J. High Energy Phys., 09(9), 157–25pp.
Abstract: The lifetimes of the Omega(0)(c) and Xi(0)(c) baryons are measured using a pp collision dataset collected by the LHCb experiment, corresponding to an integrated luminosity of 9 fb(-1). The charm baryons are produced in the fully reconstructed decay chains Omega(-)(b) -> Omega(0)(c)(-> pK(-)K(-)pi(+))pi(-) and Xi(-)(b) -> Xi(0)(c)(-> pK(-)K(-)pi(+))pi(-). The measurement uses topologically and kinematically similar B- -> D-0(-> K-K+pi(-)pi(+))pi(-) decays for normalisation. The measured lifetimes are tau(Omega c0) = 276.3 +/- 19.4 (stat) +/- 1.8 (syst) +/- 0.7(tau(D0))fs, tau(Xi c0) = 149.2 +/- 2.5 (stat) +/- 0.9 (syst) +/- 0.4(tau(D0))fs, where the first uncertainty is statistical, the second systematic and the third due to the uncertainty of the D-0 lifetime. These results are consistent with previous measurements performed by the LHCb experiment.
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