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). Helium identification with LHCb. J. Instrum., 19(2), P02010–23pp.
Abstract: The identification of helium nuclei at LHCb is achieved using a method based on measurements of ionisation losses in the silicon sensors and timing measurements in the Outer Tracker drift tubes. The background from photon conversions is reduced using the RICH detectors and an isolation requirement. The method is developed using pp collision data at root s = 13 TeV recorded by the LHCb experiment in the years 2016 to 2018, corresponding to an integrated luminosity of 5.5 fb(-1). A total of around 10(5) helium and antihelium candidates are identified with negligible background contamination. The helium identification efficiency is estimated to be approximately 50% with a corresponding background rejection rate of up to O(10(12)). These results demonstrate the feasibility of a rich programme of measurements of QCD and astrophysics interest involving light nuclei.
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LHCb Collaboration(Aaij, R. et al), Martinez-Vidal, F., Oyanguren, A., Ruiz Valls, P., & Sanchez Mayordomo, C. (2014). Measurement of polarization amplitudes and CP asymmetries in B-0 -> phi K*(892)(0). J. High Energy Phys., 05(5), 069–24pp.
Abstract: An angular analysis of the decay B (0) -> phi K (*)(892)(0) is reported based on a pp collision data sample, corresponding to an integrated luminosity of 1.0 fb(-1), collected at a centre-of-mass energy of root S = 7 TeV with the LHCb detector. The P-wave amplitudes and phases are measured with a greater precision than by previous experiments, and confirm about equal amounts of longitudinal and transverse polarization. The S-wave K+ pi(-) and K+ K- contributions are taken into account and found to be significant. A comparison of the B (0) -> phi K (*)(892)(0) and results shows no evidence for direct CP violation in the rate asymmetry, in the triple-product asymmetries or in the polarization amplitudes and phases.
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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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LHCb Collaboration(Aaij, R. et al), Martinez-Vidal, F., Oyanguren, A., Ruiz Valls, P., & Sanchez Mayordomo, C. (2015). Measurement of the time-dependent CP asymmetries in B-s(0) -> J/psi K-S(0). J. High Energy Phys., 06(6), 131–22pp.
Abstract: The first measurement of decay-time-dependent CP asymmetries in the decay B-S(0) -> J/psi K-S(0) and an updated measurement of the ratio of branching fractions B(B-S(0) -> J/psi K-S(0))/B(B-0 -> J/psi K-S(0)) are presented. The results are obtained using data corresponding to an integrated luminosity of 3.0 fb(-1) of proton-proton collisions recorded with the LHCb detector at centre-of-mass energies of 7 and 8 TeV. The results on the CP asymmetries are A(Delta Gamma)(B-S(0) -> J/psi K-S(0)) = 0.49 +/- (0.77)(0.65)(stat) +/- 0.06(syst), C-dir(B-S(0) -> J/psi K-S(0)) = -0.28 +/- 0.41(stat) +/- 0.08(syst), S-mix(B-S(0) -> J/psi K-S(0)) = -0.08 +/- 0.40(stat) +/- 0.08(syst). The ratio B(B-S(0) -> J/psi K-S(0))/B(B-0 -> J/psi K-S(0)) is measured to be 0.0431 +/- 0.0017(stat) +/- 0.0012(syst) +/- 0.0025(f(s)/f(d)), where the last uncertainty is due to the knowledge of the B-S(0) and B-0 production fractions.
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LHCb Collaboration(Aaij, R. et al), Martinez-Vidal, F., Oyanguren, A., Ruiz Valls, P., & Sanchez Mayordomo, C. (2014). Search for CP violation in D (+/-) -> (KSK +/-)-K-0 and D-s(+/-) -> K-S(0)pi(+/-) decays. J. High Energy Phys., 10(10), 025–19pp.
Abstract: A search for CP violation in Cabibbo-suppressed D (+/-) -> aEuro parts per thousand K (S) (0) K (+/-) and D (s) (+/-) -> aEuro parts per thousand K (S) (0) pi (+/-) decays is performed using pp collision data, corresponding to an integrated luminosity of 3 fb, recorded by the LHCb experiment. The individual CP-violating asymmetries are measured to be <Equation ID=“Equa”> <MediaObject> </MediaObject> </Equation> assuming that CP violation in the Cabibbo-favoured decays is negligible. A combination of the measured asymmetries for the four decay modes D ((s)) (+/-) -> aEuro parts per thousand K (S) (0) K (+/-) and D ((s)) (+/-) -> aEuro parts per thousand K (S) (0) pi (+/-) gives the sum <Equation ID=“Equb”> <MediaObject> </MediaObject> </Equation> In all cases, the first uncertainties are statistical and the second systematic. The results represent the most precise measurements of these asymmetries to date and show no evidence for CP violation.
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