LHCb Collaboration(Aaij, R. et al), Henry, L., Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., et al. (2021). Measurement of the CKM angle gamma in B-+/- -> DK +/- and B-+/- -> D pi(+/-) decays with D -> K(S)(0)h(+)h(-). J. High Energy Phys., 02(2), 169–36pp.
Abstract: A measurement of CP-violating observables is performed using the decays B-+/- -> DK +/- and B-+/- -> D pi(+/-), where the D meson is reconstructed in one of the self-conjugate three-body final states K-S(0)pi(+)pi(-) and (KSK+K-)-K-0 (commonly denoted K(S)(0)h(+)h(-)). The decays are analysed in bins of the D-decay phase space, leading to a measurement that is independent of the modelling of the D-decay amplitude. The observables are inter- preted in terms of the CKM angle gamma. Using a data sample corresponding to an integrated luminosity of 9 fb(-1) collected in proton-proton collisions at centre-of mass energies of 7, 8, and 13 TeV with the LHCb experiment, gamma is measured to be (68.7(-5.1)(+5.2))degrees. The hadronic parameters r(B)(DK), r(B)(D pi), delta(DK)(B), and delta(D pi)(B), which are the ratios and strong-phase differences of the suppressed and favoured B-+/- decays, are also reported.
|
LHCb Collaboration(Aaij, R. et al), Garcia Martin, L. M., Henry, L., Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., et al. (2017). Measurement of CP violation in B-0 -> J/psi K-S(0) and B-0 -> psi(2S) K-S(0) decays. J. High Energy Phys., 11(11), 170–18pp.
Abstract: A measurement is presented of decay-time-dependent CP violation in the decays B-0 -> J/psi K-S(0) and B-0 -> psi(2S) K-S(0), where the J/psi is reconstructed from two electrons and the psi(2S) from two muons. The analysis uses a sample of pp collision data recorded with the LHCb experiment at centre-of-mass energies of 7 and 8 TeV, corresponding to an integrated luminosity of 3 fb(-1). The CP-violation observables are measured to be C(B-0 -> J/psi K-S(0)) = 0.12 +/- 0.07 +/- 0.02, S(B-0 -> J/psi K-S(0)) = 0.83 +/- 0.08 +/- 0.01, C(B-0 -> psi(2S) K-S(0)) = -0.05 +/- 0.10 +/- 0.01, S(B-0 -> psi(2S) K-S(0)) = 0.84 +/- 0.10 +/- 0.01, where C describes CP violation in the direct decay, and S describes CP violation in the interference between the amplitudes for the direct decay and for the decay after B-0-(B) over bar (0) oscillation. The first uncertainties are statistical and the second are systematic. The two sets of results are compatible with the previous LHCb measurement using B-0 -> J/psi K-S(0) decays, where the J/psi meson was reconstructed from two muons. The averages of all three sets of LHCb results are C(B-0 -> [c (c) over bar] K-S(0)) = -0.017 +/- 0.029, S(B-0 -> [c (c) over bar] K-S(0)) = 0.760 +/- 0.034, under the assumption that higher-order contributions to the decay amplitudes are negligible. The uncertainties include statistical and systematic contributions.
|
Masud, M., Mehta, P., Ternes, C. A., & Tortola, M. (2021). Non-standard neutrino oscillations: perspective from unitarity triangles. J. High Energy Phys., 05(5), 171–19pp.
Abstract: We formulate an alternative approach based on unitarity triangles to describe neutrino oscillations in presence of non-standard interactions (NSI). Using perturbation theory, we derive the expression for the oscillation probability in case of NSI and cast it in terms of the three independent parameters of the leptonic unitarity triangle (LUT). The form invariance of the probability expression (even in presence of new physics scenario as long as the mixing matrix is unitary) facilitates a neat geometric view of neutrino oscillations in terms of LUT. We examine the regime of validity of perturbative expansions in the NSI case and make comparisons with approximate expressions existing in literature. We uncover some interesting dependencies on NSI terms while studying the evolution of LUT parameters and the Jarlskog invariant. Interestingly, the geometric approach based on LUT allows us to express the oscillation probabilities for a given pair of neutrino flavours in terms of only three (and not four) degrees of freedom which are related to the geometric properties (sides and angles) of the triangle. Moreover, the LUT parameters are invariant under rephasing transformations and independent of the parameterization adopted.
|
LHCb Collaboration(Aaij, R. et al), Garcia Martin, L. M., Henry, L., Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., et al. (2018). Measurement of the CKM angle gamma using B-+/- -> DK +/- with D -> K-S(0)pi(+)pi(-), (KSK+K-)-K-0 decays. J. High Energy Phys., 08(8), 176–36pp.
Abstract: A binned Dalitz plot analysis of B-+/- -> DK +/- decays, with D -> K-S(0)pi(+)pi(-) and D -> (KSK+K-)-K-0, is used to perform a measurement of the CP-violating observables x(+/-) and y(+/-), which are sensitive to the Cabibbo-Kobayashi-Maskawa angle gamma. The analysis is performed without assuming any D decay model, through the use of information on the strong-phase variation over the Dalitz plot from the CLEO collaboration. Using a sample of proton-proton collision data collected with the LHCb experiment in 2015 and 2016, and corresponding to an integrated luminosity of 2.0 fb(-1), the values of the CP violation parameters are found to be x = (9.0 +/- 1.7 +/- 0.7 +/- 0.4) x 10(-2), y = (2.1 +/- 2.2 +/- 0.5 +/- 1.1) x 10(-2), x(+) = (-7.7 +/- 1.9 +/- 0.7 +/- 0.4) x 10(-2), and y(+) = (-1.0 +/- 1.9 +/- 0.4 +/- 0.9) x10(-2). The first uncertainty is statistical, the second is systematic, and the third is due to the uncertainty on the strong-phase measurements. These values are used to obtain gamma = (87(+)(12)(+11))degrees, r(B) = 0.086(-)(0.1)(43)(+0.013), and delta(B) = (101 +/- 11), where r(B) is the ratio between the suppressed and favoured B-decay amplitudes and delta(B) is the corresponding strong-interaction phase difference. This measurement is combined with the result obtained using 2011 and 2012 data collected with the LHCb experiment, to give gamma = (80(-9)(+10))degrees, r(B) = 0.080 +/- 0.011, and delta(B) = (110 +/- 10)degrees.
|
LHCb Collaboration(Aaij, R. et al), Martinez-Vidal, F., Oyanguren, A., Ruiz Valls, P., & Sanchez Mayordomo, C. (2014). Measurement of CP asymmetries in the decays B-0 -> K-*0 mu(+) mu(-) and B+ -> K+ mu(+) mu(-). J. High Energy Phys., 09(9), 177–18pp.
Abstract: The direct CP asymmetries of the decays B-0 -> K-*0 mu(+) mu(-) and B+ -> K+ mu(+) mu(-) are measured using pp collision data corresponding to an integrated luminosity of 3.0 fb(-1) collected with the LHCb detector. The respective control modes B-0 -> J/psi K+ and B+ -> J/psi K+ are used to account for detection and production asymmetries. The measurements are made in several intervals of mu(+)mu(-) invariant mass squared, with the phi(1020) and charmonium resonance regions excluded. Under the hypothesis of zero CP asymmetry in the control modes, the average values of the asymmetries are A(CP)(B-0 -> K-*0 mu(+) mu(-) and B+ -> K+ mu(+) mu(-)) = -0.035 +/- 0.024 +/- 0.003, A(CP)(B+ -> K+ mu(+) mu(-) = 0.012 +/- 0.017 +/- 0.001, where the first uncertainties are statistical and the second are due to systematic effects. Both measurements are consistent with the Standard Model prediction of small CP asymmetry in these decays.
|
