LHCb Collaboration(Aaij, R. et al), Garcia Martin, L. M., Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., Ruiz Valls, P., et al. (2017). Measurement of the b- Quark Production Cross Section in 7 and 13 TeV pp Collisions. Phys. Rev. Lett., 118(5), 052002–11pp.
Abstract: Measurements of the cross section for producing b quarks in the reaction pp -> b (b) over barX are reported in 7 and 13 TeV collisions at the LHC as a function of the pseudorapidity. in the range 2 < eta < 5 covered by the acceptance of the LHCb experiment. The measurements are done using semileptonic decays of b-flavored hadrons decaying into a ground-state charmed hadron in association with a muon. The cross sections in the covered. range are 72.0 +/- 0.3 +/- 6.8 and 154.3 +/- 1.5 +/- 14.3 +/- μb for 7 and 13 TeV. The ratio is 2.14 +/- 0.02 +/- 0.13, where the quoted uncertainties are statistical and systematic, respectively. The agreement with theoretical expectation is good at 7 TeV, but differs somewhat at 13 TeV. The measured ratio of cross sections is larger at lower eta than the 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 Lifetime of the Doubly Charmed Baryon Xi(++)(cc). Phys. Rev. Lett., 121(5), 052002–10pp.
Abstract: The first measurement of the lifetime of the doubly charmed baryon Xi(++)(cc) is presented, with the signal reconstructed in the final state Lambda K-+(c)-pi(+)pi(+). The data sample used corresponds to an integrated luminosity of 1.7 fb(-1), collected by the LHCb experiment in proton-proton collisions at a center-of-mass energy of 13 TeV. The Xi(++)(cc) lifetime is measured to be 0.256(-0.022)(+0.024) (stat) +/- 0.014(syst) ps.
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BABAR Collaboration(Lees, J. P. et al), Martinez-Vidal, F., & Oyanguren, A. (2012). Search for the Z(1)(4050)(+) and Z(2)(4250)(+) states in (B)over-bar(0) -> chi K-c1(-)pi(+) and B+ -> chi K-c1(S)0 pi(+). Phys. Rev. D, 85(5), 052003–12pp.
Abstract: We search for the Z(1)(4050)(+) and Z(2)(4250)(+) states, reported by the Belle Collaboration, decaying to chi(c1)pi(+) in the decays (B) over bar (0) -> chi K-c1(-)pi(+) and B+ -> chi K-c1(S)0 pi(+) where chi(c1) -> J/psi gamma. The data were collected with the BABAR detector at the SLAC PEP-II asymmetric-energy e(+)e(-) collider operating at center-of-mass energy 10.58 GeV, and correspond to an integrated luminosity of 429 fb(-1). In this analysis, we model the background-subtracted, efficiency-corrected chi(c1)pi(+) mass distribution using the K pi mass distribution and the corresponding normalized K pi Legendre-polynomial moments, and then test the need for the inclusion of resonant structures in the description of the chi(c1)pi(+) mass distribution. No evidence is found for the Z(1)(4050)(+) and Z(2)(4250)(+) resonances, and 90% confidence level upper limits on the branching fractions are reported for the corresponding B-meson decay modes.
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BABAR Collaboration(Lees, J. P. et al), Martinez-Vidal, F., Oyanguren, A., & Villanueva-Perez, P. (2013). Measurement of the D*(2010)(+) natural linewidth and the D*(2010)(+)-D-0 mass difference. Phys. Rev. D, 88(5), 052003–20pp.
Abstract: We measure the mass difference, Delta m(0), between the D*(2010)(+) and the D-0 and the natural linewidth, Gamma, of the transition D*(2010)(+) -> D-0 pi(+). The data were recorded with the BABAR detector at center-of-mass energies at and near the Upsilon(4S) resonance, and correspond to an integrated luminosity of approximately 477 fb(-1). The D-0 is reconstructed in the decay modes D-0 -> K-pi(+) and D-0 -> K-pi(+)pi(-)pi(+). For the decay mode D-0 -> K-pi(+) we obtain Gamma = (83.4 +/- 1.7 +/- 1.5) keV and Delta m(0) = (145425.6 +/- 0.6 +/- 1.8) keV, where the quoted errors are statistical and systematic, respectively. For the D-0 -> K-pi(+)pi(-)pi(+) mode we obtain Gamma = (83.2 +/- 1.5 +/- 2.6) keV and Delta m(0) = (145426.6 +/- 0.5 +/- 2.0) keV. The combined measurements yield Gamma = (83.3 +/- 1.2 +/- 1.4) keV and Delta m(0) = (145425.9 +/- 0.4 +/- 1.7) keV; the width is a factor of approximately 12 times more precise than the previous value, while the mass difference is a factor of approximately 6 times more precise.
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BABAR Collaboration(Lees, J. P. et al), Martinez-Vidal, F., Oyanguren, A., & Villanueva-Perez, P. (2014). Measurement of Collins asymmetries in inclusive production of charged pion pairs in e(+)e(-) annihilation at BABAR. Phys. Rev. D, 90(5), 052003–26pp.
Abstract: We present measurements of Collins asymmetries in the inclusive process e(+)e(-) -> pi pi X, where p stands for charged pions, at a center-of-mass energy of 10.6 GeV. We use a data sample of 468 fb(-1) collected by the BABAR experiment at the PEP-II B factory at SLAC, and consider pairs of charged pions produced in opposite hemispheres of hadronic events. We observe clear asymmetries in the distributions of the azimuthal angles in two distinct reference frames. We study the dependence of the asymmetry on several kinematic variables, finding that it increases with increasing pion momentum and momentum transverse to the analysis axis, and with increasing angle between the thrust and beam axis.
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BABAR Collaboration(del Amo Sanchez, P. et al), Lopez-March, N., Martinez-Vidal, F., Milanes, D. A., & Oyanguren, A. (2010). Exclusive production of Ds+Ds-,D-s*D-+(s)-, and D-s*D-+(s)*(-) via e(+)e(-) annihilation with initial-state radiation. Phys. Rev. D, 82(5), 052004–10pp.
Abstract: We perform a study of exclusive production of Ds+Ds-,D-s*(+),D-s(-), and D-s*D-+(s)*- final states in initial-state radiation events from e(+)e(-) annihilations at a center-of-mass energy near 10.58 GeV, to search for charmonium 1(--) states. The data sample corresponds to an integrated luminosity of 525 fb(-1) and was recorded by the BABAR experiment at the PEP-II storage ring. Ds+Ds-,D-s*(+),D-s(-) and ,D-s*(+),D-s*(-) mass spectra show evidence of the known psi resonances. Limits are extracted for the branching ratios of the decays X(4260) -> D-s(()*()+) D-s(()*()-)
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LHCb Collaboration(Aaij, R. et al), Garcia Martin, L. M., Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., Ruiz Valls, P., et al. (2017). Measurements of charm mixing and CP violation using D-0 -> K-+/-pi(-/+) decays. Phys. Rev. D, 95(5), 052004–14pp.
Abstract: Measurements of charm mixing and CP violation parameters from the decay-time-dependent ratio of D-0 -> K+pi(-) to D-0 -> K-pi(+) decay rates and the charge-conjugate ratio are reported. The analysis uses (B) over bar -> D*(+) μX-, and charge-conjugate decays, where D *(+) -> D-0 pi(+), and D-0 -> K-+/-pi(-/+). The pp collision data are recorded by the LHCb experiment at center-of-mass energies root s = 7 and 8 TeV, corresponding to an integrated luminosity of 3 fb(-1). The data are analyzed under three hypotheses: (i) mixing assuming CP symmetry, (ii) mixing assuming no direct CP violation in the Cabibbo-favored or doubly Cabibbo-suppressed decay amplitudes, and (iii) mixing allowing either direct CP violation and/or CP violation in the superpositions of flavor eigenstates defining the mass eigenstates. The data are also combined with those from a previous LHCb study of D-0 -> K pi decays from a disjoint set of D*(+) candidates produced directly in pp collisions. In all cases, the data are consistent with the hypothesis of CP symmetry.
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LHCb Collaboration(Aaij, R. et al), Garcia Martin, L. M., Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., Ruiz Valls, P., et al. (2017). Measurement of the B-+/- production asymmetry and the CP asymmetry in B-+/-> J/psi K-+/- decays. Phys. Rev. D, 95(5), 052005–13pp.
Abstract: The B-+/- meson production asymmetry in pp collisions is measured using B-+/- -> (D) over bar (0)pi(+) decays. The data were recorded by the LHCb experiment during Run 1 of the LHC at center- of- mass energies of ffiffiffi root s = 7 and 8 TeV. The production asymmetries, integrated over transverse momenta in the range 2 < p(T) < 30 GeV/c, and rapidities in the range 2.1 < y < 4.5 are measured to be A(prod)(B+, root s = 7 TeV) = (-0.41 +/- 0.49 +/- 0.10) x 10(- 2), A(prod)(B+, root s = 8 TeV = (- 0.53 +/- 0.31 +/- 0.10) x 10(-2), where the first uncertainties are statistical and the second are systematic. These production asymmetries are used to correct the raw asymmetries of (B+ -> J/psi K+) decays, thus allowing a measurement of the CP asymmetry, A(CP)(B+-> J/psi K+) = (0.09 +/- 0.27 +/- 0.07) x 10(-2)
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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). Model-independent measurement of charm mixing parameters in Bbar → D0(→ K0Sπ+π-)μ-νbar_μX decays. Phys. Rev. D, 108(5), 052005–17pp.
Abstract: A measurement of charm mixing and CP-violating parameters is reported, using B over bar -> D0(-> K0S pi+pi-)x mu- nu over bar μX decays reconstructed in proton-proton collisions collected by the LHCb experiment during the years 2016 to 2018, corresponding to an integrated luminosity of 5.4 fb-1. The measured mixing and CP-violating parameters are xCP = [4.29 1 1.48(stat) 1 0.26(syst)] x 10-3, yCP = [12.61 1 3.12(stat) 1 0.83(syst)] x 10-3, Ax = [-0.77 1 0.93(stat) 1 0.28(syst)] x 10-3, Ay = [3.01 1 1.92(stat) 1 0.26(syst)] x 10-3. The results are complementary to and consistent with previous measurements. A combination with the recent LHCb analysis of D*+ -> D0(-> K0S pi+ pi-)pi+ decays is 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 the mass and production rate of Xi(-)(b)( )baryons. Phys. Rev. D, 99(5), 052006–13pp.
Abstract: The first measurement of the production rate of Xi(-)(b) baryons in pp collisions relative to that of Lambda(0 )(b)baryons is reported, using data samples collected by the LHCb experiment, and corresponding to integrated luminosities of 1, 2 and 1.6 fb(-1) at root s = 7, 8 and 13 TeV, respectively. In the kinematic region 2 < eta < 6 and p(T) < 20 GeV/c, we measure f(Xi b-)/f(Lambda b0) B(Xi(-)(b)-> J/psi Xi(-))/B(Lambda(0)(b)-> J/psi Lambda)= (10.8 +/- 0.9 +/- 0.8) x 10(-2) [root s = 7,8 TeV], f(Xi b-)/f(Lambda b0) B(Xi(-)(b)-> J/psi Xi(-))/B(Lambda(0)(b)-> J/psi Lambda) =(13.1 +/- 1.1 +/- 1.0) x 10(-2) [root s = 13 TeV], where and f(Xi b-) and f(Lambda)(b0) the fragmentation fractions of b quarks into Xi(-)(b) and Lambda(0)(b) baryons, respectively; B represents branching fractions; and the uncertainties are due to statistical and experimental systematic sources. The values of f(Xi b-)/f(Lambda b0) are obtained by invoking SU(3) symmetry in the Xi(-)(b)-> J/psi Xi(-) and Lambda(0)(b)-> J/psi Lambda decays. Production asymmetries between Xi(-)(b) and (Xi) over bar (+)(b) baryons are also reported. The mass of the Xi(-)(b) baryon is also measured relative to that of the Lambda(0)(b) baryon, from which it is found that m(Xi(-)(b)) = 5796.70 +/- 0.39 +/- 0.15 +/- 0.17 MeV/c(2), where the last uncertainty is due to the precision on the known Lambda(0)(b) mass. This result represents the most precise determination of the Xi(-)(b) mass.
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