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LHCb Collaboration(Aaij, R. et al), Jaimes Elles, S. J., Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., Rebollo De Miguel, M., et al. (2024). Search for CP violation in the phase space of D0 → KS0 K± π∓ decays with the energy test. J. High Energy Phys., 03(3), 107–20pp.
Abstract: A search for CP violation in D-0 -> (KSK+)-K-0 pi(-) and D-0 -> (KSK-)-K-0 pi(+) decays is reported. The search is performed using an unbinned model-independent method known as the energy test that probes local CP violation in the phase space of the decays. The data analysed correspond to an integrated luminosity of 5.4 fb(-1) collected in proton-proton collisions by the LHCb experiment at a centre-of-mass energy of root s = 13TeV, amounting to approximately 950 thousand and 620 thousand signal candidates for the D-0 -> (KSK-)-K-0 pi(+) and D-0 -> (KSK+)-K-0 pi(-) modes, respectively. The method is validated using D-0 -> K-pi(+)pi(-)pi(+) and D-0 -> K-S(0)pi(+)pi(-) decays, where CP-violating effects are expected to be negligible, and using background-enhanced regions of the signal decays. The results are consistent with CP symmetry in both the D-0 -> (KSK-)-K-0 pi(+) and the D-0 -> (KSK+)-K-0 pi(-) decays, with p-values for the hypothesis of no CP violation of 70% and 66%, respectively.
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LHCb Collaboration(Aaij, R. et al), Jaimes Elles, S. J., Jashal, B. K., Martinez Vidal, F., Oyanguren, A., Rebollo De Miguel, M., et al. (2023). First observation of the B+ → Ds+ Ds- K+ decay. Phys. Rev. D, 108(3), 034012–14pp.
Abstract: B+ -> D-s(+) D-s(-) K+ decay is observed for the first time using proton-proton collision data collected by the LHCb detector at center-of-mass energies of 7, 8, and 13 TeV, corresponding to an integrated luminosity of 9 fb-1. Its branching fraction relative to that of the B+ -> D-s(+) D-s(-) K+ decay is measured to be B(B+ -> D-s(+) D-s(-) K+)/(KB+ -> D-s(+) D-s(-) K+) = 0.525 +/- 0.0333 +/- 0.027 +/- 0.034; where the first uncertainty is statistical, the second s D-s Kthornthorn systematic, and the third is due to the uncertainties on the branching fractions of the D-s(+/-) -> (KK +/-)-K--/+pi(+/-) and D-+/- -> K--/+pi(+/-)pi(+/-) decays. This measurement fills an experimental gap in the knowledge of the family of Cabibbo-favored (b) over bar -> (b) over barc (c) over bar transitions and opens the path for unique studies of spectroscopy in future.
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LHCb Collaboration(Aaij, R. et al), Jaimes Elles, S. J., Jashal, B. K., Martinez Vidal, F., Oyanguren, A., Rebollo De Miguel, M., et al. (2023). Search for KS(L)0 → μ+ μ- μ+ μ- decays at LHCb. Phys. Rev. D, 108(3), L031102–12pp.
Abstract: A search for K-S(L)(0) -> mu(+) mu(-) mu(+) mu(-) decays is performed using proton-proton collision data collected by the LHCb experiment at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 5.1 fb(-1). No evidence for signal is found. The 90% confidence level upper limits are the first set for both decays and are B(K-S(0)) -> mu(+) mu(-) mu(+) mu(-)) < 5.1 x 10(-12) and B(K-L(0))-> mu(+) mu(-) mu(+) mu(-)) < 2.3 x 10(-9).
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LHCb Collaboration(Aaij, R. et al), Martinez-Vidal, F., Oyanguren, A., & Ruiz Valls, P. (2014). Measurement of Upsilon production in collisions at root s=2.76 TeV. Eur. Phys. J. C, 74(4), 2835–11pp.
Abstract: The production of , and mesons decaying into the dimuon final state is studied with the LHCb detector using a data sample corresponding to an integrated luminosity of collected in proton-proton collisions at a centre-of-mass energy of TeV. The differential production cross-sections times dimuon branching fractions are measured as functions of the transverse momentum and rapidity, over the ranges GeV/ and . The total cross-sections in this kinematic region, assuming unpolarised production, are measured to be sigma (pp -> Upsilon(1S)X) x B(Upsilon(1S) -> mu(+)mu(-)) = 1.111 +/- 0.043 +/- 0.044 nb, sigma (pp -> Upsilon(2S)X) x B(Upsilon(2S) -> mu(+)mu(-)) = 0.264 +/- 0.023 +/- 0.011 nb, sigma (pp -> Upsilon(3S)X) x B(Upsilon(3S) -> mu(+)mu(-))s = 0.159 +/- 0.020 +/- 0.007 nb, where the first uncertainty is statistical and the second systematic.
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LHCb Collaboration(Aaij, R. et al), Martinez-Vidal, F., Oyanguren, A., Ruiz Valls, P., & Sanchez Mayordomo, C. (2015). Measurement of the Semileptonic CP Asymmetry in B-0-(B)over-bar(0) Mixing. Phys. Rev. Lett., 114(4), 041601–9pp.
Abstract: The semileptonic CP asymmetry in B-0-(B) over bar (0) mixing, a(s1)(d), is measured in proton-proton collision data, corresponding to an integrated luminosity of 3.0 fb(-1), recorded by the LHCb experiment. Semileptonic B-0 decays are reconstructed in the inclusive final states D-mu(+) and D*(-)mu(+), where the D- meson decays into the K+pi(-)pi(-) final state and the D*(-) meson into the (D) over bar (0)(-> K+pi(-))pi(-) final state. The asymmetry between the numbers of D-(*()-)mu(+) and D-(*()+)mu(-) decays is measured as a function of the decay time of the B-0 mesons. The CP asymmetry is measured to be a(s1)(d) = (-0.02 +/- 0.19 +/- 0.30)%, where the first uncertainty is statistical and the second systematic. This is the most precise measurement of a(s1)(d) to date and is consistent with the prediction from the standard model.
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LHCb Collaboration(Aaij, R. et al), Martinez-Vidal, F., Oyanguren, A., Ruiz Valls, P., & Sanchez Mayordomo, C. (2015). Precision Measurement of CP Violation in B-S(0) -> J/Psi K+K- Decays. Phys. Rev. Lett., 114(4), 041801–9pp.
Abstract: The time-dependent CP asymmetry in B-S(0) -> J/Psi K+K- decays is measured using pp collision data, corresponding to an integrated luminosity of 3.0 fb(-1), collected with the LHCb detector at center-of-mass energies of 7 and 8 TeV. In a sample of 96 000 B-S(0) -> J/Psi K+K- decays, the CP-violating phase phi(s) is measured, as well as the decay widths GL and GH of the light and heavy mass eigenstates of the B-s(0)-(B) over bar (0)(s) system. The values obtained are phi(s) = -0.058 +/- 0.049 +/- 0.006 rad, Gamma(s) equivalent to (Gamma(L) + Gamma(H))/2 = 0.6603 +/- 0.0027 +/- 0.0015 ps(-1), and Delta Gamma(s) equivalent to Gamma(L)-Gamma(H) = 0.0805 +/- 0.0091 +/- 0.0032 ps(-1), where the first uncertainty is statistical and the second, systematic. These are the most precise single measurements of those quantities to date. A combined analysis with B-s(0) -> J/Psi pi(+)pi(-) decays gives phi(s) = -0.010 +/- 0.039 rad. All measurements are in agreement with the standard model predictions. For the first time, the phase phi(s) is measured independently for each polarization state of the K+K- system and shows no evidence for polarization dependence.
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LHCb Collaboration(Aaij, R. et al), Martinez-Vidal, F., Oyanguren, A., Ruiz Valls, P., & Sanchez Mayordomo, C. (2015). Measurement of indirect CP asymmetries in D-0 -> K-K+ and D-0 -> pi(-)pi(+) decays using semileptonic B decays. J. High Energy Phys., 04(4), 043–19pp.
Abstract: Time-dependent CP asymmetries in the decay rates of the singly Cabibbo-suppressed decays D-0 -> K-K+ and D-0 -> pi (-) pi(+) are measured in pp collision data corresponding to an integrated luminosity of 3.0 fb(-1) collected by the LHCb experiment. The D-0 mesons are produced in semileptonic b-hadron decays, where the charge of the accompanying muon is used to determine the initial state as D-0 or (D) over bar (0). The asymmetries in effective lifetimes between D-0 and (D) over bar (0) decays, which are sensitive to indirect CP violation, are determined to be A(Gamma) (K-K+) = (-0.134 +/- 0.077(-0.034)(+0.026))%, A(Gamma) (pi(-)pi(+)) = -0.092 +/- 0.145(-0.033)(+0.025))%, where the first uncertainties are statistical and the second systematic. This result is in agreement with previous measurements and with the hypothesis of no indirect CP violation in D (0) decays.
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LHCb Collaboration(Aaij, R. et al), Martinez-Vidal, F., Oyanguren, A., Ruiz Valls, P., & Sanchez Mayordomo, C. (2015). Precise measurements of the properties of the B-1(5721)(0,+) and B-2*(5747)(0,+) states and observation of B-+,B-0 pi(-,+) mass structures. J. High Energy Phys., 04(4), 024–27pp.
Abstract: Invariant mass distributions of B (+) pi (-) and B (0) pi (+) combinations are investigated in order to study excited B mesons. The analysis is based on a data sample corresponding to 3.0 fb(-1) of pp collision data, recorded by the LHCb detector at centre-of-mass energies of 7 and 8 TeV. Precise measurements of the masses and widths of the B (1)(5721)(0,+) and B (2)(5747)(0,+) states are reported. Clear enhancements, particularly prominent at high pion transverse momentum, are seen over background in the mass range 5850-6000 MeV in both B (+) pi (-) and B (0) pi (+) combinations. The structures are consistent with the presence of four excited B mesons, labelled B (J) (5840)(0,+) and B (J) (5960)(0,+), whose masses and widths are obtained under different hypotheses for their quantum numbers.
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LHCb Collaboration(Aaij, R. et al), Martinez-Vidal, F., Oyanguren, A., Ruiz Valls, P., & Sanchez Mayordomo, C. (2015). Search for long-lived particles decaying to jet pairs. Eur. Phys. J. C, 75(4), 152–12pp.
Abstract: A search is presented for long-lived particles with a mass between 25 and 50 GeV/c(2) and a lifetime between 1 and 200 ps in a sample of proton-proton collisions at a centre-of-mass energy of root s = 7 TeV, corresponding to an integrated luminosity of 0.62 fb(-1), collected by the LHCb detector. The particles are assumed to be pair-produced by the decay of a standard model-like Higgs boson. The experimental signature of the long-lived particle is a displaced vertex with two associated jets. No excess above the background is observed and limits are set on the production cross-section as a function of the long-lived particle mass and lifetime.
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LHCb Collaboration(Aaij, R. et al), Martinez-Vidal, F., Oyanguren, A., Ruiz Valls, P., & Sanchez Mayordomo, C. (2015). Angular analysis of the B-0 -> K*(0) e(+) e(-) decay in the low-q(2) region. J. High Energy Phys., 04(4), 064–23pp.
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 3.0 fb(-1), collected by the LHCb experiment in pp collisions at centre-of-mass energies of 7 and 8 TeV during 2011 and 2012. For the first time several observables are measured in the dielectron mass squared (q(2)) interval between 0.002 and 1.120 GeV2/c(4). The angular observables F-L and A(T)(Re) which are related to the K-*0 polarisation and to the lepton forward-backward asymmetry, are measured to be F-L = 0.16 +/- 0.06 +/- 0.03 and A(T)(Re) = 0.10 +/- 0.18 +/- 0.05, where the first uncertainty is statistical and the second systematic. The angular observables A(T)((2)) and A(T)(Im) which are sensitive to the photon polarisation in this q(2) range, are found to be A(T)((2)) = – 0.23 +/- 0.23 +/- 0.05 and A(T)(Im) = 0.14 +/- 0.22 +/- 0.05. The results are consistent with Standard Model predictions.
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