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T2K Collaboration(Abe, K. et al), Antonova, M., Cervera-Villanueva, A., Fernandez, P., Izmaylov, A., & Novella, P. (2019). Measurement of the muon neutrino charged-current cross sections on water, hydrocarbon and iron, and their ratios, with the T2K on-axis detectors. Prog. Theor. Exp. Phys., (9), 093C02–30pp.
Abstract: We report a measurement of the flux-integrated v(mu) charged-current cross sections on water, hydrocarbon, and iron in the T2K on-axis neutrino beam with a mean neutrino energy of 1.5 GeV. The measured cross sections on water, hydrocarbon, and iron are sigma(H2O)(CC) = (0.840 +/- 0.010(stat.)(0.08)(+0.10)(syst.)) x 10 (38) cm(2)/nucleon, sigma(CH)(CC) = (0.817 +/- 0.007(stat.)(0.08)(+0.11)(syst.)) x 10 (38) cm(2)/nucleon, and sigma(Fe)(CC) = (0.859 +/- 0.003(stat.)(0.10)(+0.12)(syst.)) x 10 (38) cm(2)/nucleon, respectively, for a restricted phase space of induced muons: theta(mu) < 45 degrees and p(mu) >0.4 GeV/c in the laboratory frame. The measured cross section ratios are sigma(H2O)(CC)/sigma(CH)(CC) = 1.028 +/- 0.016(stat.) +/- 0.053(syst.), sigma(Fe)(CC)/sigma(H2O)(CC) = 1.023 +/- 0.012(stat.) +/- 0.058(syst.), and sigma(Fe)(CC)/sigma(CH)(CC) = 1.049 +/- 0.010(stat.) +/- 0.043(syst.). These results, with an unprecedented precision for the measurements of neutrino cross sections on water in the studied energy region, show good agreement with the current neutrino interaction models used in the T2K oscillation analyses.
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Molina, R., Geng, L. S., & Oset, E. (2019). Comments on the dispersion relation method to vector-vector interaction. Prog. Theor. Exp. Phys., (10), 103B05–16pp.
Abstract: We study in detail the method proposed recently to study the vector-vector interaction using the N/D method and dispersion relations, which concludes that, while, for J = 0, one finds bound states, in the case of J = 2, where the interaction is also attractive and much stronger, no bound state is found. In that work, approximations are done for N and D and a subtracted dispersion relation for D is used, with subtractions made up to a polynomial of second degree in s – s(th), matching the expression to 1 – VG at threshold. We study this in detail for the rho rho interaction and to see the convergence of the method we make an extra subtraction matching 1 – VG at threshold up to (s – s(th))(3). We show that the method cannot be used to extrapolate the results down to 1270 MeV where the f(2)(1270) resonance appears, due to the artificial singularity stemming from the “on-shell” factorization of the rho exchange potential. In addition, we explore the same method but folding this interaction with the mass distribution of the rho, and we show that the singularity disappears and the method allows one to extrapolate to low energies, where both the (s – s(th))(2) and (s – s(th))(3) expansions lead to a zero of Re D(s), at about the same energy where a realistic approach produces a bound state. Even then, the method generates a large Im D(s) that we discuss is unphysical.
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ATLAS Collaboration(Aaboud, M. et al), Alvarez Piqueras, D., Aparisi Pozo, J. A., Bailey, A. J., Barranco Navarro, L., Cabrera Urban, S., et al. (2019). Measurement of the production cross section for a Higgs boson in association with a vector boson in the H -> WW* -> l nu l nu channel in pp collisions at root s=13 TeV with the ATLAS detector. Phys. Lett. B, 798, 134949–24pp.
Abstract: A measurement of the Higgs boson production cross sections via associated WH and ZH production using H -> WW* -> l nu l nu decays, where l stands for either an electron or a muon, is presented. Results for combined WH and ZH production are also presented. The analysis uses events produced in proton-proton collisions collected with the ATLAS detector at the Large Hadron Collider in 2015 and 2016. The data correspond to an integrated luminosity of 36.1 fb(-1) recorded at a centre-of-mass energy of 13 TeV. The products of the H -> WW* branching fraction times the WH and ZH cross sections are measured to be 0.67(-0.27)(+0.31)(stat.)(-0.14)(+0.18)(syst.) pb and 0.54(-0.24)(+0.31)(stat.)(-0.07)(+0.15)(syst.) pb respectively, in agreement with the Standard Model predictions.
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ATLAS Collaboration(Aaboud, M. et al), Alvarez Piqueras, D., Aparisi Pozo, J. A., Bailey, A. J., Barranco Navarro, L., Cabrera Urban, S., et al. (2019). Search for a right-handed gauge boson decaying into a high-momentum heavy neutrino and a charged lepton in pp collisions with the ATLAS detector at root s=13 TeV. Phys. Lett. B, 798, 134942–23pp.
Abstract: A search for a right-handed gauge boson W-R, decaying into a boosted right-handed heavy neutrino N-R, in the framework of Left-Right Symmetric Models is presented. It is based on data from proton-proton collisions with a centre-of-mass energy of 13 TeV collected by the ATLAS detector at the Large Hadron Collider during the years 2015, 2016 and 2017, corresponding to an integrated luminosity of 80 fb(-1). The search is performed separately for electrons and muons in the final state. A distinguishing feature of the search is the use of large-radius jets containing electrons. Selections based on the signal topology result in smaller background compared to the expected signal. No significant deviation from the Standard Model prediction is observed and lower limits are set in the W-R and N-R mass plane. Mass values of the W-R smaller than 3.8-5 TeV are excluded for N-R in the mass range 0.1-1.8 TeV.
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ATLAS Collaboration(Aad, G. et al), Alvarez Piqueras, D., Aparisi Pozo, J. A., Bailey, A. J., Barranco Navarro, L., Cabrera Urban, S., et al. (2019). Evidence for the production of three massive vector bosons with the ATLAS detector. Phys. Lett. B, 798, 134913–22pp.
Abstract: A search for the production of three massive vector bosons in proton-proton collisions is performed using data at root s = 13 TeV recorded with the ATLAS detector at the Large Hadron Collider in the years 2015-2017, corresponding to an integrated luminosity of 79.8 fb(-1). Events with two same-sign leptons l (electrons or muons) and at least two reconstructed jets are selected to search for WWW -> l nu l nu qq. Events with three leptons without any same-flavour opposite-sign lepton pairs are used to search for WWW > l nu l nu l nu, while events with three leptons and at least one same-flavour opposite-sign lepton pair and one or more reconstructed jets are used to search for WWZ -> l nu qqll. Finally, events with four leptons are analysed to search for WWZ > l nu l nu ll and WZZ > qqllll. Evidence for the joint production of three massive vector bosons is observed with a significance of 4.1 standard deviations, where the expectation is 3.1 standard deviations.
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