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 CP asymmetry in B-s(0) -> (DsK +/-)-K-/+ decays. J. High Energy Phys., 03(3), 059–28pp.
Abstract: We report the measurements of the CP-violating parameters in B-s(0) -> (DsK +/-)-K--/+ decays observed in pp collisions, using a data set corresponding to an integrated luminosity of 3.0 fb(-1) recorded with the LHCb detector. We measure C-f = 0.73 +/- 0.14 +/- 0.05, A(f)(Delta Gamma) = 0.39 +/- 0.28 +/- 0.15, A(<(f)over) (Delta Gamma)(bar>) = 0.31 +/- 0.28 +/- 0.15, S-f = -0.52 +/- 0.20 +/- 0.07, S-(f) over bar = -0.49 +/- 0.20 +/- 0.07, where the uncertainties are statistical and systematic, respectively. These parameters are used together with the world-average value of the B-s(0) mixing phase, -2 beta(s), to obtain a measurement of the CKM angle gamma from B-s(0) -> (DsK +/-)-K--/+ decays, yielding gamma – (128 (+17)(-22))degrees modulo 180 degrees, where the uncertainty contains both statistical and systematic contributions. This corresponds to 3.8 sigma evidence for CP violation in the interference between decay and decay after mixing.
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ATLAS Collaboration(Aaboud, M. et al), Alvarez Piqueras, D., Barranco Navarro, L., Cabrera Urban, S., Castillo Gimenez, V., Cerda Alberich, L., et al. (2017). Measurement of charged-particle distributions sensitive to the underlying event in root s=13 TeV proton-proton collisions with the ATLAS detector at the LHC. J. High Energy Phys., 03(3), 157–42pp.
Abstract: We present charged-particle distributions sensitive to the underlying event, measured by the ATLAS detector in proton-proton collisions at a centre-of-mass energy of 13 TeV, in low-luminosity Large Hadron Collider fills corresponding to an integrated luminosity of 1.6 nb-1. The distributions were constructed using charged particles with absolute pseudorapidity less than 2.5 and with transverse momentum greater than 500 MeV, in events with at least one such charged particle with transverse momentum above 1 GeV. These distributions characterise the angular distribution of energy and particle flows with respect to the charged particle with highest transverse momentum, as a function of both that momentum and of charged-particle multiplicity. The results have been corrected for detector effects and are compared to the predictions of various Monte Carlo event generators, experimentally establishing the level of underlying-event activity at LHC Run 2 energies and providing inputs for the development of event generator modelling. The current models in use for UE modelling typically describe this data to 5% accuracy, compared with data uncertainties of less than 1%.
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LHCb Collaboration(Aaij, R. et al), Martinez-Vidal, F., Oyanguren, A., Ruiz Valls, P., & Sanchez Mayordomo, C. (2016). Measurement of the properties of the Xi(b)(*0) baryon. J. High Energy Phys., 05(5), 161–19pp.
Abstract: We perform a search for near-threshold I (b) (0) resonances decaying to I (b) (-) pi (+) in a sample of proton-proton collision data corresponding to an integrated luminosity of 3 fb(-1) collected by the LHCb experiment. We observe one resonant state, with the following properties: m(Xi b*0) – m (Xi b-) – m (pi+) = 15.727 +/- 0.068 (stat) +/- 0.023 (syst) MeV/c2, Gamma(Xi b*0) = 0.90 +/- 0.16 (stat) +/- 0.08 (syst) MeV. This confirms the previous observation by the CMS collaboration. The state is consistent with the J (P) = 3/2(+)aEuro integral I (b) (au 0) resonance expected in the quark model. This is the most precise determination of the mass and the first measurement of the natural width of this state. We have also measured the ratio sigma(pp -> Xi b*0 X)B(Xi b*0 -> Xi b-pi+)/sigma(pp -> Xi b- X) = 0.28 +/- 0.03 (stat.) +/- 0.01 (syst).
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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). Near-threshold DD spectroscopy and observation of a new charmonium state. J. High Energy Phys., 07(7), 035–23pp.
Abstract: Using proton-proton collision data, corresponding to an integrated luminosity of 9 fb, collected with the LHCb detector between 2011 and 2018, a new narrow charmonium state, the X(3842) resonance, is observed in the decay modes X(3842) ! D0 D 0 and X(3842) ! D+D. The mass and the natural width of this state are measured to be where the fi rst uncertainty is statistical and the second is systematic. The observed mass and narrow natural width suggest the interpretation of the new state as the unobserved spin-3 3 1 3 D 3 charmonium state. In addition, prompt hadroproduction of the (3770) and 2 (3930) states is observed for the fi rst time, and the parameters of these states are measured to be m (3770) = 3778 : 1 0 : 7 0 : 6MeV where the first uncertainty is statistical and the second is systematic.
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LHCb Collaboration(Aaij, R. et al), Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., & Ruiz Vidal, J. (2022). Study of B-c(+) decays to charmonia and three light hadrons. J. High Energy Phys., 01(1), 065–28pp.
Abstract: Using proton-proton collision data, corresponding to an integrated luminosity of 9 fb(-1) collected with the LHCb detector, seven decay modes of the B-C(+) meson into a J/psi or psi(2S) meson and three charged hadrons, kaons or pions, are studied. The decays B-C (+)-> (psi(2S) -> J/psi pi(+)pi(-))pi(+), B+C -> (psi(2S)pi(+)pi(-)pi(+), B+C -> J/psi K+pi(-)pi(+) and B+C -> J/K+K-K+ are observed for the first time, and evidence for the B-C (+)-> (psi(2S)K+K-pi(+), decay is found, where J/psi and psi(2S) mesons are reconstructed in their dimuon decay modes. The ratios of branching fractions between the different B-C(+) decays are reported as well as the fractions of the decays proceeding via intermediate resonances. The results largely support the factorisation approach used for a theoretical description of the studied decays.
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