LHCb Collaboration(Aaij, R. et al), Garcia Martin, L. M., Henry, L., Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., et al. (2017). Resonances and CP violation in B-s(0) and (B)over-bar(s)(0) -> j psi K+K- decays in the mass region above the I center dot(1020). J. High Energy Phys., 08(8), 037–28pp.
Abstract: The decays of B (s) (0) and mesons into the J/psi K (+) K (-) final state are studied in the K (+) K (-) mass region above the I center dot(1020) meson in order to determine the resonant substructure and measure the CP-violating phase, I center dot (s) , the decay width, I“ (s) , and the width difference between light and heavy mass eigenstates, Delta I” (s) . A decay-time dependent amplitude analysis is employed. The data sample corresponds to an integrated luminosity of 3 fb(-1) produced in 7 and 8 TeV pp collisions at the LHC, collected by the LHCb experiment. The measurement determines I center dot (s) = 119 +/- 107 +/- 34 mrad. A combination with previous LHCb measurements using similar decays into the J/psi pi (+) pi (-) and J/psi I center dot(1020) final states gives I center dot (s) = 1 +/- 37 mrad, consistent with the Standard Model prediction.
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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.
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LHCb Collaboration(Aaij, R. et al), Garcia Martin, L. M., Henry, L., Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., et al. (2018). Search for CP violation using triple product asymmetries in Lambda(0)(b) -> pK(-) pi(+) pi(-), Lambda(0)(b) -> pK(-) K+ K- and Xi(0)(b) -> pK(-) K- pi(+) decays. J. High Energy Phys., 08(8), 039–27pp.
Abstract: A search for CP and P violation using triple- product asymmetries is performed with Lambda(0)(b) -> pK(-) pi(+) pi(-), Lambda(0)(b) -> pK(-) K+ K- and Xi(0)(b) -> pK(-) K- pi(+) decays. The data sample corresponds to integrated luminosities of 1.0 fb(-1) and 2.0 fb(-1), recorded with the LHCb detector at centre- of- mass energies of 7TeV and 8TeV, respectively. The CP- and P-violating asymmetries are measured both integrating over all phase space and in speci fi c phase- space regions. No signi fi cant deviation from CP or P symmetry is found. The fi rst observation of Lambda(0)(b) -> pK(-) chi(c0) (1P)(->pi(+) pi(-), K+ K-) decay is also reported.
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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. (2019). Measurement of CP observables in the process B-0 -> DK*0 with two- and four-body D decays. J. High Energy Phys., 08(8), 041–30pp.
Abstract: Measurements of CP observables in B-0 -> DK0 decays are presented, where D represents a superposition of D-0 and D0 states. The D meson is reconstructed in the two-body final states K+pi(-), pi K-+(-), K+K- and pi(+)pi(-), and, for the first time, in the fourbody final states K+pi(-)pi(+)pi(-), pi K-+(-)pi(+)pi(-) and pi(+)pi(-)pi(+)pi(-). The analysis uses a sample of neutral B mesons produced in proton-proton collisions, corresponding to an integrated luminosity of 1.0, 2.0 and 1.8 fb(-1) collected with the LHCb detector at centre-of-mass energies of ,8 and 13 TeV, respectively. First observations of the decays B-0 -> D(pi K-+(-))K-0 and B-0 -> D(pi(+)pi(-)pi(+)pi(-))K-0 are obtained. The measured observables are interpreted in terms of the CP -violating weak phase gamma.
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T2K Collaboration(Abe, K. et al), Antonova, M., Cervera-Villanueva, A., Fernandez, P., Izmaylov, A., & Novella, P. (2019). Search for neutral-current induced single photon production at the ND280 near detector in T2K. J. Phys. G, 46(8), 08LT01–16pp.
Abstract: Neutrino neutral-current (NC) induced single photon production is a sub-leading order process for accelerator-based neutrino beam experiments including T2K. It is, however, an important process to understand because it is a background for electron (anti)neutrino appearance oscillation experiments. Here, we performed the first search of this process below 1 GeV using the fine-grained detector at the T2K ND280 off-axis near detector. By reconstructing single photon kinematics from electron-positron pairs, we achieved 95% pure gamma ray sample from 5.738 x 10(20) protons-on-targets neutrino mode data. We do not find positive evidence of NC induced single photon production in this sample. We set the model-dependent upper limit on the cross-section for this process, at 0.114 x 10(-38) cm(2) (90% C.L.) per nucleon, using the J-PARC off-axis neutrino beam with an average energy of < E-v > similar to 0.6 GeV. This is the first limit on this process below 1 GeV which is important for current and future oscillation experiments looking for electron neutrino appearance oscillation signals.
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Agarwalla, S. K., Prakash, S., & Sankar, S. U. (2013). Resolving the octant of theta(23) with T2K and NOvA. J. High Energy Phys., 07(7), 131–24pp.
Abstract: Preliminary results of MINOS experiment indicate that theta(23) is not maximal. Global fits to world neutrino data suggest two nearly degenerate solutions for theta(23): one in the lower octant (LO: theta(23) < 45 degrees) and the other in the higher octant (HO: theta(23) > 45 degrees). v(mu) -> v(e) oscillations in superbeam experiments are sensitive to the octant and are capable of resolving this degeneracy. We study the prospects of this resolution by the current T2K and upcoming NOvA experiments. Because of the hierarchy-delta(CP) degeneracy and the octant delta(CP) degeneracy, the impact of hierarchy on octant resolution has to be taken into account. As in the case of hierarchy determination, there exist favorable (unfavorable) values of delta(CP) for which octant resolution is easy (challenging). However, for octant resolution the unfavorable delta(CP) values of the neutrino data are favorable for the anti-neutrino data and vice-verse. This is in contrast to the case of hierarchy determination. In this paper, we compute the combined sensitivity of T2K and NOvA to resolve the octant ambiguity. If sin(2)theta(23) – 0.41, then NOvA can rule out all the values of theta(23) in HO at 2 sigma C.L., irrespective of the hierarchy and delta(CP). Addition of T2K data improves the octant sensitivity. If T2K were to have equal neutrino and anti-neutrino runs of 2.5 years each, a 2 sigma resolution of the octant becomes possible provided sin(2) theta(23) <= 0.43 or >= 0.58 for any value of delta(CP).
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Blennow, M., Coloma, P., Donini, A., & Fernandez-Martinez, E. (2013). Gain fractions of future neutrino oscillation facilities over T2K and NOvA. J. High Energy Phys., 07(7), 159–23pp.
Abstract: We evaluate the probability of future neutrino oscillation facilities to discover leptonic CP violation and/or measure the neutrino mass hierarchy. We study how this probability is affected by positive or negative hints for these observables to be found at T2K and NO nu A. We consider the following facilities: LBNE; T2HK; and the 10 GeV Neutrino Factory (NF10), and show how their discovery probabilities change with the running time of T2K and NO nu A conditioned to their results. We find that, if after 15 years T2K and NO nu A have not observed a 90% CL hint of CP violation, then LBNE and T2HK have less than a 10% chance of achieving a 5 sigma discovery, whereas NF10 still has a similar to 40% chance to do so. Conversely, if T2K and NO nu A have an early 90% CL hint in 5 years from now, T2HK has a rather large chance to achieve a 5 sigma CP violation discovery (75% or 55%, depending on whether the mass hierarchy is known or not). This is to be compared with the 90% (30%) probability that NF10 (LBNE) would have to observe the same signal at 5 sigma. A hierarchy measurement at 5 sigma is achievable at both LBNE and NF10 with more than 90% probability, irrespectively of the outcome of T2K and NO nu A. We also find that if LBNE or a similar very long baseline super-beam is the only next generation facility to be built, then it is very useful to continue running T2K and NO nu A (or at least T2K) beyond their original schedule in order to increase the CP violation discovery chances, given their complementarity.
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LHCb Collaboration(Aaij, R. et al), Martinez-Vidal, F., Oyanguren, A., Ruiz Valls, P., & Sanchez Mayordomo, C. (2014). Measurement of CP asymmetry in D-0 -> K- K+ and D-0 -> pi(-) pi(+) decays. J. High Energy Phys., 07(7), 041–25pp.
Abstract: Time-integrated CP asymmetries in D-0 decays to the final states K- K+ and pi(-) pi(+) are measured using proton-proton collisions corresponding to 3 fb(-1) of integrated luminosity collected at centre-of-mass energies of 7 TeV and 8 TeV. The D-0 mesons are produced in semileptonic b-hadron decays, where the charge of the accompanying muon is used to determine the initial flavour of the charm meson. The difference in CP asymmetries between the two final states is measured to be Delta A(CP) = A(CP)(K- K+) – A(CP)(pi(-) pi(+)) = (+0.14 +/- 0.16 (stat) +/- 0.08 (syst))% . A measurement of A(CP)(K- K+) is obtained assuming negligible CP violation in charm mixing and in Cabibbo-favoured D decays. It is found to be A(CP)(K- K+) = (-0.06 +/- 0.15 (stat) +/- 0.10 (syst))% , where the correlation coefficient between Delta A(CP) and A(CP)(K- K+) is rho = 0.28. By combining these results, the CP asymmetry in the D-0 -> pi(-) pi(+) channel is A(CP)(pi(-) pi(+)) = (-0.20 +/- 0.19 (stat) +/- 0.10 (syst))%.
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LHCb Collaboration(Aaij, R. et al), Martinez-Vidal, F., Oyanguren, A., Ruiz Valls, P., & Sanchez Mayordomo, C. (2014). Observation of the Lambda(0)(b) -> J / psi p pi(-) decay. J. High Energy Phys., 07(7), 103–19pp.
Abstract: The first observation of the Cabibbo-suppressed decay Lambda(0)(b) -> J / psi p pi(-) is reported using a data sample of proton-proton collisions at 7 and 8TeV, corresponding to an integrated luminosity of 3 fb(-1). A prominent signal is observed and the branching fraction relative to the decay mode Lambda(0)(b) -> J / psi pK(-) is determined to be B(Lambda(0)(b) -> J / psi p pi(-))/ B(Lambda(0)(b) -> J / psi pK(-)) = 0.0824 +/- 0.0025 (stat) +/- 0.0042 (syst). A search for direct CP violation is performed. The difference in the CP asymmetries between these two decays is found to be ACP(Lambda(0)(b) -> J / psi p pi(-))/ A(CP)(Lambda(0)(b) -> J / psi pK(-)) = (+5.7 +/- 2.4 (stat) +/- 1.2 (syst))%, which is compatible with CP symmetry at the 2.2 sigma level.
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LHCb Collaboration(Aaij, R. et al), Martinez-Vidal, F., Oyanguren, A., Ruiz Valls, P., & Sanchez Mayordomo, C. (2015). Measurement of CP asymmetries and polarisation fractions in B-s(0) -> K*(0)(K)over-bar*(0) decays. J. High Energy Phys., 07(7), 166–28pp.
Abstract: An angular analysis of the decay B-s(0) -> K*(0)(K) over bar*(0) is performed using pp collisions corresponding to an integrated luminosity of 1.0 fb(-1) collected by the LHCb experiment at a centre-of-mass energy root s = 7TeV. A combined angular and mass analysis separates six helicity amplitudes and allows the measurement of the longitudinal polarisation fraction f(L) = 0.201 +/- 0.057 (stat.) +/- 0.040 (syst.) for the B-s(0) -> K*(892)(0)(K) over bar*(892)(0) decay. A large scalar contribution from the K*(0) (1430) and K*(0) (800) resonances is found, allowing the determination of additional CP asymmetries. Triple product and direct CP asymmetries are determined to be compatible with the Standard Model expectations. The branching fraction B(B-s(0) -> K*(892)(0)(K) over bar*(892)(0)) is measured to be (10.8 +/- 2.1 (stat.) +/- 1.4 (syst.) +/- 0.6 (f(d)/f(s))) x 10(-6).
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