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Soleti, S. R., Dietz, P., Esteve, R., Garcia-Barrena, J., Herrero,, Lopez, F., et al. (2026). CRYSP: a total-body PET based on cryogenic cesium iodide crystals. Phys. Med. Biol., 71(2), 025001–18pp.
Abstract: Objective. Total body positron emission tomography (TBPET) scanners have the potential to substantially reduce both acquisition time and administered radiation dose, owing to their high sensitivity. However, their widespread clinical adoption is hindered by the high cost of currently available systems. This work explores the use of pure cesium iodide (CsI) monolithic crystals operated at cryogenic temperatures as a cost-effective alternative to rare-earth scintillators for TBPET. Approach. We investigate the performance of pure CsI crystals operated at cryogenic temperatures (similar to 100 K), where they achieve a light yield of approximately 105 photons/MeV. The implications for energy resolution, spatial resolution (including depth-of-interaction (d.o.i.) capability), and timing performance are assessed, with a view toward their integration into a TBPET system. Main results. Cryogenic CsI crystals demonstrated energy resolution below 7% and coincidence time resolution (CTR) at the nanosecond level, despite their relatively slow scintillation decay time. A Monte Carlo simulation of monolithic CsI crystals shows that a millimeter-scale spatial resolution in all three dimensions can be obtained. These characteristics indicate that high-performance PET imaging is achievable with this technology. Significance. A TBPET scanner based on cryogenic CsI monolithic crystals could combine excellent imaging performance with significantly reduced detector costs, enabling broader accessibility and accelerating the adoption of TBPET in both clinical and research settings.
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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). Study of charm mixing and CP violation with D0→ K±π∓π±π∓ decays. J. High Energy Phys., 12(12), 153–39pp.
Abstract: A study of charm mixing and CP violation in D0 -> K +/-pi -/+pi +/-pi -/+ decays is performed using data collected by the LHCb experiment in proton-proton collisions from 2015 to 2018, corresponding to an integrated luminosity of 6 fb-1. The ratio of promptly produced D0 -> K+pi-pi+pi- to D0 -> K-pi+pi-pi+ decay rates is measured as a function of D0 decay time, both inclusive over phase space and in bins of phase space. Taking external inputs for the D0-D<overline>0\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ {D}<^>0-{\overline{D}}<^>0 $$\end{document} mixing parameters x and y allows constraints to be obtained on the hadronic parameters of the charm decay. When combined with previous measurements from charm-threshold experiments and at LHCb, improved knowledge is obtained for these parameters, which is valuable for studies of the angle gamma of the Unitarity Triangle. An alternative analysis is also performed, in which external inputs are taken for the hadronic parameters, and the mixing parameters are determined, including triangle x and triangle y, which are nonzero in the presence of CP violation. It is found that x=0.85-0.24+0.15%\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ x=\left(0.{85}{-0.24}<^>{+0.15}\right)\% $$\end{document}, y=0.21-0.27+0.29%\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ y=\left(0.{21}{-0.27}<^>{+0.29}\right)\% $$\end{document}, triangle x = (-0.02 +/- 0.04) % and Delta y=0.02-0.03+0.04%\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \Delta y=\left(0.0{2}_{-0.03}<^>{+0.04}\right)\% $$\end{document}. These results are consistent with previous measurements and the hypothesis of CP conservation.
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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 B0→ ρ(770)0γ branching fraction. J. High Energy Phys., 12(12), 151–21pp.
Abstract: The ratio between the branching fractions of the B0 -> rho(770)0 gamma and B0 -> K*(892)0 gamma decays is measured with proton-proton collision data collected by the LHCb experiment at centre-of-mass energies of 7, 8, and 13 TeV, corresponding to an integrated luminosity of 9 fb-1. The measured value isBB0 ->rho 7700 gamma BB0 -> K & lowast;8920 gamma=0.0189 +/- 0.0007 +/- 0.0005, where the first uncertainty is statistical and the second systematic. The branching fraction for B0 -> rho(770)0 gamma decays is hence obtained asBB0 ->rho 7700 gamma=7.9 +/- 0.3 +/- 0.2 +/- 0.2x10-7, where the last uncertainty is due to the branching fraction of the normalisation mode. This result assumes that both the rho(770)0 and K*(892)0 decays saturate the dihadron mass spectra considered in the analysis. It is consistent with the current world-average value and by far the most precise measurement to date.
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ATLAS Collaboration(Aad, G. et al), Aikot, A., Amos, K. R., Bouchhar, N., Cabrera Urban, S., Cantero, J., et al. (2025). Search for electroweak production of vector-like leptons in τ-lepton and b-jet final states in pp collisions at √s=13 TeV with the ATLAS detector. Eur. Phys. J. C, 85(11), 1335–42pp.
Abstract: A search for pair-production of vector-like leptons is presented, considering their decays into a third-generation Standard Model (SM) quark and a vector leptoquark (U-1) as predicted by an ultraviolet-complete extension of the SM, referred to as the '4321' model. Given the assumed decay of U-1 into third-generation SMfermions, the final state can contain multiple tau-leptons and b-quarks. This search is based on a dataset of pp collisions at root s = 13 TeV recorded with the ATLAS detector during Run 2 of the Large Hadron Collider, corresponding to an integrated luminosity of up to 140 fb(-1). No significant excess above the SM background prediction is observed, and 95% confidence level limits on the cross-section times branching ratio are derived as a function of the vector-like lepton mass. A lower observed (expected) limit of 910 GeV (970 GeV) is set on the vectorlike lepton mass. Additionally, the results are interpreted for a supersymmetric model with an R-parity violating coupling to the third-generation quarks and leptons. Lower observed (expected) limits are obtained on the higgsino mass at 880 GeV (940 GeV) and on the wino mass at 1170 GeV (1170 GeV).
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Costantini, M. N., Mantani, L., Moore, J. M., Schütze Sanchez, V., & Ubiali, M. (2026). A new tool for fast-flying PDF fits. Eur. Phys. J. C, 86(1), 22–19pp.
Abstract: We present Colibri, an open-source Python code that provides a general and flexible tool for PDF fits. The code is built so that users can implement their own PDF model, and use the built-in functionalities of Colibri for a fast computation of observables. It grants easy access to experimental data, several error propagation methodologies, including the Hessian method, the Monte Carlo replica method, and an efficient numerical Bayesian sampling algorithm. To demonstrate the capabilities of Colibri, we consider its simplest application: a polynomial PDF parametrisation. We perform closure tests using a full set of DIS data and compare the results of Hessian and Monte Carlo fits with those from a Bayesian fit. We further discuss how the functionalities illustrated in this example can be extended to more complex PDF parametrisations. In particular, the Bayesian framework in Colibri provides a principled approach to model selection and model averaging, making it a valuable tool for benchmarking and combining different PDF parametrisations on solid statistical grounds.
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