de Salas, P. F., Forero, D. V., Gariazzo, S., Martinez-Mirave, P., Mena, O., Ternes, C. A., et al. (2021). 2020 global reassessment of the neutrino oscillation picture. J. High Energy Phys., 02(2), 071–36pp.
Abstract: We present an updated global fit of neutrino oscillation data in the simplest three-neutrino framework. In the present study we include up-to-date analyses from a number of experiments. Concerning the atmospheric and solar sectors, besides the data considered previously, we give updated analyses of IceCube DeepCore and Sudbury Neutrino Observatory data, respectively. We have also included the latest electron antineutrino data collected by the Daya Bay and RENO reactor experiments, and the long-baseline T2K and NO nu A measurements, as reported in the Neutrino 2020 conference. All in all, these new analyses result in more accurate measurements of theta (13), theta (12), Delta m212 and Delta m312. The best fit value for the atmospheric angle theta (23) lies in the second octant, but first octant solutions remain allowed at similar to 2.4 sigma. Regarding CP violation measurements, the preferred value of delta we obtain is 1.08 pi (1.58 pi) for normal (inverted) neutrino mass ordering. The global analysis still prefers normal neutrino mass ordering with 2.5 sigma statistical significance. This preference is milder than the one found in previous global analyses. These new results should be regarded as robust due to the agreement found between our Bayesian and frequentist approaches. Taking into account only oscillation data, there is a weak/moderate preference for the normal neutrino mass ordering of 2.00 sigma. While adding neutrinoless double beta decay from the latest Gerda, CUORE and KamLAND-Zen results barely modifies this picture, cosmological measurements raise the preference to 2.68 sigma within a conservative approach. A more aggressive data set combination of cosmological observations leads to a similar preference for normal with respect to inverted mass ordering, namely 2.70 sigma. This very same cosmological data set provides 2 sigma upper limits on the total neutrino mass corresponding to Sigma m(nu)< 0.12 (0.15) eV in the normal (inverted) neutrino mass ordering scenario. The bounds on the neutrino mixing parameters and masses presented in this up-to-date global fit analysis include all currently available neutrino physics inputs.
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Double Chooz collaboration(Abrahao, T. et al), & Novella, P. (2021). Reactor rate modulation oscillation analysis with two detectors in Double Chooz. J. High Energy Phys., 01(1), 190–18pp.
Abstract: A theta (13) oscillation analysis based on the observed antineutrino rates at the Double Chooz far and near detectors for different reactor power conditions is presented. This approach provides a so far unique simultaneous determination of theta (13) and the total background rates without relying on any assumptions on the specific background contributions. The analysis comprises 865 days of data collected in both detectors with at least one reactor in operation. The oscillation results are enhanced by the use of 24.06 days (12.74 days) of reactor-off data in the far (near) detector. The analysis considers the nu <mml:mo stretchy=“true”><overbar></mml:mover>e interactions up to a visible energy of 8.5 MeV, using the events at higher energies to build a cosmogenic background model considering fast-neutrons interactions and Li-9 decays. The background-model-independent determination of the mixing angle yields sin(2)(2 theta (13)) = 0.094 0.017, being the best-fit total background rates fully consistent with the cosmogenic background model. A second oscillation analysis is also performed constraining the total background rates to the cosmogenic background estimates. While the central value is not significantly modified due to the consistency between the reactor-off data and the background estimates, the addition of the background model reduces the uncertainty on theta (13) to 0.015. Along with the oscillation results, the normalization of the anti-neutrino rate is measured with a precision of 0.86%, reducing the 1.43% uncertainty associated to the expectation.
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LHCb Collaboration(Aaij, R. et al), Henry, L., Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., et al. (2021). Study of B-s(0) -> J/psi pi(+)pi-K+K- decays. J. High Energy Phys., 02(2), 024–34pp.
Abstract: The decays B-s(0) -> J/psi pi(+)pi-K+K- are studied using a data set corresponding to an integrated luminosity of 9 fb(-1), collected with the LHCb detector in proton-proton collisions at centre-of-mass energies of 7, 8 and 13TeV. The decays B-s(0) -> J/psi K*(K) over bar *0 and B-s(0) -> chi(c1)(3872)K+K-, where the K+K- pair does not originate from a phi meson, are observed for the first time. Precise measurements of the ratios of branching fractions between intermediate chi(c1)(3872)phi, J/psi K*0 (K) over bar *0, psi(2S)phi and chi(c1)(3872)K+K- states are reported. A structure, denoted as X(4740), is observed in the J/psi phi mass spectrum and, assuming a Breit-Wigner parameterisation, its mass and width are determined to be m(X(4740)) = 4741 +/- 6 +/- 6 MeV/c(2), Gamma(X(4740)) = 53 +/- 15 +/- 11MeV, where the first uncertainty is statistical and the second is systematic. In addition, the most precise single measurement of the mass of the B-s(0) meson is performed and gives a value of m(Bs)(0) = 5366.98 +/- 0.07 +/- 0.13MeV/c(2).
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NEXT Collaboration(Kekic, M. et al), Benlloch-Rodriguez, J. M., Carcel, S., Carrion, J. V., Diaz, J., Felkai, R., et al. (2021). Demonstration of background rejection using deep convolutional neural networks in the NEXT experiment. J. High Energy Phys., 01(1), 189–22pp.
Abstract: Convolutional neural networks (CNNs) are widely used state-of-the-art computer vision tools that are becoming increasingly popular in high-energy physics. In this paper, we attempt to understand the potential of CNNs for event classification in the NEXT experiment, which will search for neutrinoless double-beta decay in Xe-136. To do so, we demonstrate the usage of CNNs for the identification of electron-positron pair production events, which exhibit a topology similar to that of a neutrinoless double-beta decay event. These events were produced in the NEXT-White high-pressure xenon TPC using 2.6 MeV gamma rays from a Th-228 calibration source. We train a network on Monte Carlo-simulated events and show that, by applying on-the-fly data augmentation, the network can be made robust against differences between simulation and data. The use of CNNs offers significant improvement in signal efficiency and background rejection when compared to previous non-CNN-based analyses.
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ATLAS Collaboration(Aad, G. et al), Aparisi Pozo, J. A., Bailey, A. J., Cabrera Urban, S., Castillo, F. L., Castillo Gimenez, V., et al. (2021). Measurement of hadronic event shapes in high-p(T) multijet final states at root s=13 TeV with the ATLAS detector. J. High Energy Phys., 01(1), 188–44pp.
Abstract: A measurement of event-shape variables in proton-proton collisions at large momentum transfer is presented using data collected at root s = 13 TeV with the ATLAS detector at the Large Hadron Collider. Six event-shape variables calculated using hadronic jets are studied in inclusive multijet events using data corresponding to an integrated luminosity of 139 fb(-1). Measurements are performed in bins of jet multiplicity and in different ranges of the scalar sum of the transverse momenta of the two leading jets, reaching scales beyond 2 TeV. These measurements are compared with predictions from Monte Carlo event generators containing leading-order or next-to-leading order matrix elements matched to parton showers simulated to leading-logarithm accuracy. At low jet multiplicities, shape discrepancies between the measurements and the Monte Carlo predictions are observed. At high jet multiplicities, the shapes are better described but discrepancies in the normalisation are observed.
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