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LHCb Collaboration(Aaij, R. et al), Garcia Martin, L. M., Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., Ruiz Valls, P., et al. (2016). Differential branching fraction and angular moments analysis of the decay B-0 -> K+pi(-)mu(+)mu(-) in the K-0,K-2*(1431:)(0) region. J. High Energy Phys., 12(12), 065–24pp.
Abstract: Measurements of the differential branching fraction and angular moments of the decay B-0 -> K+pi(-)mu(+)mu(-) in the K+pi(-) invariant mass range 1330 <m(K+pi(-)) < 1530 MeV/c(2) are presented. Proton-proton collision data are used, corresponding to an integrated luminosity of 3 fb(-1) collected by the LHCb experiment. Differential branching fraction measurements are reported in five bins of the invariant mass squared of the dimuon system, q(2), between 0.1 and 8.0 GeV2/c(4). For the first time, an angular analysis sensitive to the S-, P- and D-wave contributions of this rare decay is performed. The set of 40 normalised angular moments describing the decay is presented for the q(2) range 1.1-6.0 GeV2/c(4).
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LHCb Collaboration(Aaij, R. et al), Garcia Martin, L. M., Henry, L., Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., et al. (2020). Strong constraints on the b -> s gamma photon polarisation from B-0 -> K(*0)e(+)e(-) decays. J. High Energy Phys., 12(12), 081–25pp.
Abstract: An angular analysis of the B-0 -> K*(0)e(+)e(-) decay is performed using a data sample corresponding to an integrated luminosity of 9 fb(-1) of pp collisions collected with the LHCb experiment. The analysis is conducted in the very low dielectron mass squared (q(2)) interval between 0.0008 and 0.257 GeV2, where the rate is dominated by the B-0 -> K*(0)gamma transition with a virtual photon. The fraction of longitudinal polarisation of the K*(0) meson, F-L, is measured to be F-L = (4.4 +/- 2.6 +/- 1.4)%, where the first uncertainty is statistical and the second systematic. The A(T)(Re) observable, which is related to the lepton forward-backward asymmetry, is measured to be A(T)(Re) = -0.06 +/- 0.08 +/- 0.02. The A(T)((2)) and A(T)(Im) transverse asymmetries, which are sensitive to the virtual photon polarisation, are found to be A(T)((2)) = 0.11 +/- 0.10 +/- 0.02 and A(T)(Im) = 0.02 +/- 0.10 +/- 0.01. The results are consistent with Standard Model predictions and provide the world's best constraint on the b -> s gamma photon polarisation.
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Hirsch, M., Joaquim, F. R., & Vicente, A. (2012). Constrained SUSY seesaws with a 125 GeV Higgs. J. High Energy Phys., 11(11), 105–33pp.
Abstract: Motivated by the ATLAS and CMS discovery of a Higgs-like boson with a mass around 125 GeV, and by the need of explaining neutrino masses, we analyse the three canonical SUSY versions of the seesaw mechanism (type I, II and III) with CMSSM boundary conditions. In type II and III cases, SUSY particles are lighter than in the CMSSM (or the constrained type I seesaw), for the same set of input parameters at the universality scale. Thus, to explain m(h0) similar or equal to 125 GeV at low energies, one is forced into regions of parameter space with very large values of m(0), M-1/2 or A(0). We compare the squark and gluino masses allowed by the ATLAS and CMS ranges for m(h0) (extracted from the 2011-2012 data), and discuss the possibility of distinguishing seesaw models in view of future results on SUSY searches. In particular, we briefly comment on the discovery potential of LHC upgrades, for squark/gluino mass ranges required by present Higgs mass constraints. A discrimination between different seesaw models cannot rely on the Higgs mass data alone, therefore we also take into account the MEG upper limit on BR(mu -> e gamma) and show that, in some cases, this may help to restrict the SUSY parameter space, as well as to set complementary limits on the seesaw scale.
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LHCb Collaboration(Aaij, R. et al), Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., Ruiz Valls, P., & Sanchez Mayordomo, C. (2016). Measurements of the S-wave fraction in B-0 -> K+ pi(-) mu(+) mu(-) decays and the B-0 -> K*(892)(0) mu(+) mu(-) differential branching fraction. J. High Energy Phys., 11(11), 047–30pp.
Abstract: A measurement of the differential branching fraction of the decay B-0 -> K* (892)(0) mu(+)mu(-) is presented together with a determination of the S-wave fraction of the K+ pi(-) system in the decay B-0 -> K+ pi-mu(+)mu(-). The analysis is based on pp-collision data corresponding to an integrated luminosity of 3 fb(-1) collected with the LHCb experiment. The measurements are made in bins of the invariant mass squared of the dimuon system, q(2). Precise theoretical predictions for the differential branching fraction of B-0 -> K* (892)(0) mu(+) mu(-) decays are available for the q(2) region 1.1 < q(2) < 6.0 GeV2/c(4). In this q(2) region, for the K+pi(-) invariant mass range 796 < m(K pi) < 996MeV/c(2), the S-wave fraction of the K+pi(-) system in B-0 -> K+pi(-)mu(+)mu(-) decays is found to be F-S – 0.101 +/- 0.017(stat) +/- 0: 009(syst), and the differential branching fraction of B-0 -> K* (892)(0) mu(+)mu(-) decays is determined to be dB/dq(2) = (0.392(-0.019)(+ 0.020)(stat) +/- 0.010(syst) +/- 0.027(norm)) x 10(-7) c(4)/GeV2. The differential branching fraction measurements presented are the most precise to date and are found to be in agreement with Standard Model predictions.
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NA62 Collaboration(Cortina Gil, E. et al), & Husek, T. (2020). An investigation of the very rare K+ -> pi+ nu nubar decay. J. High Energy Phys., 11(11), 042–57pp.
Abstract: The NA62 experiment reports an investigation of the K+-> pi+nu nu <overbar></mml:mover> mode from a sample of K+ decays collected in 2017 at the CERN SPS. The experiment has achieved a single event sensitivity of (0.389 +/- 0.024) x 10(-10), corresponding to 2.2 events assuming the Standard Model branching ratio of (8.4 +/- 1.0) x 10(-11). Two signal candidates are observed with an expected background of 1.5 events. Combined with the result of a similar analysis conducted by NA62 on a smaller data set recorded in 2016, the collaboration now reports an upper limit of 1.78 x 10(-10) for the K+-> pi+nu nu <overbar></mml:mover> branching ratio at 90% CL. This, together with the corresponding 68% CL measurement of (0.48<mml:mo>-0.48<mml:mo>+0.72) x 10(-10), are currently the most precise results worldwide, and are able to constrain some New Physics models that predict large enhancements still allowed by previous measurements.
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LHCb Collaboration(Aaij, R. et al), Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., & Ruiz Vidal, J. (2021). Angular analysis of the rare decay B-s(0) -> phi mu(+)mu(-). J. High Energy Phys., 11(11), 043–45pp.
Abstract: An angular analysis of the rare decay B-s(0) -> phi mu(+)mu(-) is presented, using proton-proton collision data collected by the LHCb experiment at centre-of-mass energies of 7, 8 and 13TeV, corresponding to an integrated luminosity of 8.4 fb(-1). The observables describing the angular distributions of the decay B-s(0) -> phi mu(+)mu(-) are determined in regions of q(2), the square of the dimuon invariant mass. The results are consistent with Standard Model predictions.
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LHCb Collaboration(Aaij, R. et al), Martinez-Vidal, F., Oyanguren, A., Ruiz Valls, P., & Sanchez Mayordomo, C. (2014). First observations of the rare decays B (+) -> K (+)pi (+)pi (-)mu(+)mu (-) and B (+)-> phi K (+)mu(+)mu (-). J. High Energy Phys., 10(10), 064–18pp.
Abstract: First observations of the rare decays B (+) -> K (+)pi (+) pi (-) μ(+) μ(-) and B (+)-> phi K+ mu(+)mu(-) are presented using data corresponding to an integrated luminosity of 3.0 fb(-1), collected by the LHCb experiment at centre-of-mass energies of 7 and 8 TeV. The branching fractions of the decays are B(B (+) -> K (+)pi (+) pi (-) μ(+) μ(-) ) = (4.36 (-0.27) (+0.29) (stat) +/- 0.21 (syst) +/- (norm)) x 10(-7), B(B (+)-> phi K+ mu(+)mu(-)) = (0.82 (+0.19)(-0.17) (stat) (+0.10)(-0.04) (syst) +/- 0.27 (norm)) x 10(-7) where the uncertainties are statistical, systematic, and due to the uncertainty on the branching fractions of the normalisation modes. A measurement of the differential branching fraction in bins of the invariant mass squared of the dimuon system is also presented for the decay B (+) -> K (+)pi (+) pi (-) μ(+) μ(-)
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LHCb Collaboration(Aaij, R. et al), Martinez-Vidal, F., Oyanguren, A., Ruiz Valls, P., & Sanchez Mayordomo, C. (2015). First measurement of the differential branching fraction and CP asymmetry of the B-+/- -> pi(+/-)mu(+/-)mu(-) decay. J. High Energy Phys., 10(10), 034–21pp.
Abstract: The differential branching fraction with respect to the dimuon invariant mass squared, and the CP asymmetry of the B-+/- -> pi(+/-)mu(+/-)mu(-) decay are measured for the first time. The CKM matrix elements vertical bar V-td vertical bar, and vertical bar V-ts vertical bar, and the ratio vertical bar V-td/V-ts vertical bar are determined. The analysis is performed using proton-proton collision data corresponding to an integrated luminosity of 3.0 fb(-1), collected by the LHCb experiment at centre-of-mass energies of 7 and 8 TeV. The total branching fraction and CP asymmetry of B-+/- -> pi(+/-)mu(+/-)mu(-) decays are measured to be B(B-+/- -> pi(+/-)mu(+/-)mu(-)) = (1.83 +/- 0.24 +/- 0.05) x 10(-8) and A(cp)(B-+/- -> pi(+/-)mu(+/-)mu(-)) = -0.11 +/- 0.12 +/- 0.01, where the first uncertainties are statistical and the second are systematic. These are the most precise measurements of these observables to date, and they are compatible with the predictions of the Standard Model.
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NA48/2 Collaboration(Batley, J. R. et al), & Fiorini, L. (2018). Measurement of the form factors of charged kaon semileptonic decays. J. High Energy Phys., 10(10), 150–23pp.
Abstract: A measurement of the form factors of charged kaon semileptonic decays is presented, based on 4.4 x 10(6)K(+/-) (0)e(e)(+/-) (Ke3 +/-) and 2.3 x 10(6)K(+/-) (0)+/- (K3 +/-) decays collected in 2004 by the NA48/2 experiment. The results are obtained with improved precision as compared to earlier measurements. The combination of measurements in the Ke3 +/- and K3 +/- modes is also presented.
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Hirsch, M., Kernreiter, T., Romao, J. C., & del Moral, A. V. (2010). Minimal supersymmetric inverse seesaw: neutrino masses, lepton flavour violation and LHC phenomenology. J. High Energy Phys., 01(1), 103–21pp.
Abstract: We study neutrino masses in the framework of the supersymmetric inverse seesaw model. Different from the non-supersymmetric version a minimal realization with just one pair of singlets is sufficient to explain all neutrino data. We compute the neutrino mass matrix up to 1-loop order and show how neutrino data can be described in terms of the model parameters. We then calculate rates for lepton flavour violating (LFV) processes, such as μ-> e gamma and chargino decays to singlet scalar neutrinos. The latter decays are potentially observable at the LHC and show a characteristic decay pattern dictated by the same parameters which generate the observed large neutrino angles.
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