Chen, Z. Q. et al, & Montaner-Piza, A. (2019). Proton Shell Evolution below Sn-132: First Measurement of Low-Lying beta-Emitting Isomers in Ag-123,Ag-325. Phys. Rev. Lett., 122(21), 212502–6pp.
Abstract: The beta-delayed gamma-ray spectroscopy of neutron-rich Ag-123,Ag-325 isotopes is investigated at the Radioactive Isotope Beam Factory of RIKEN, and the long-predicted 1/2(-) beta-emitting isomers in Ag-123,Ag-325 are identified for the first time. With the new experimental results, the systematic trend of energy spacing between the lowest 9/2(+) and 1/2(-) levels is extended in Ag isotopes up to N = 78, providing a clear signal for the reduction of the Z = 40 subshell gap in Ag towards N = 82. Shell-model calculations with the state-of-the-art V-MU plus M3Y spin-orbit interaction give a satisfactory description of the low-lying states in Ag-123,Ag-325. The tensor force is found to play a crucial role in the evolution of the size of the Z = 40 subshell gap. The observed inversion of the single-particle levels around Ag-123 can be well interpreted in terms of the monopole shift of the pi 1g(9/2) orbitals mainly caused by the increasing occupation of nu 1h(11/2) orbitals.
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ATLAS Collaboration(Aaboud, M. et al), Alvarez Piqueras, D., Bailey, A. J., Barranco Navarro, L., Cabrera Urban, S., Castillo, F. L., et al. (2018). Probing the Quantum Interference between Singly and Doubly Resonant Top-Quark Production in pp Collisions at root s=13 TeV with the ATLAS Detector. Phys. Rev. Lett., 121(15), 152002–20pp.
Abstract: This Letter presents a normalized differential cross-section measurement in a fiducial phase-space region where interference effects between top-quark pair production and associated production of a single top quark with a W boson and a b-quark are significant. Events with exactly two leptons (ee, μmu, or e mu) and two b-tagged jets that satisfy a multiparticle invariant mass requirement are selected from 36.1 fb(-1) of protonproton collision data taken at root s = 13 TeV with the ATLAS detector at the LHC in 2015 and 2016. The results are compared with predictions from simulations using various strategies for the interference. The standard prescriptions for interference modeling are significantly different from each other but are within 2 sigma of the data. State-of-the-art predictions that naturally incorporate interference effects provide the best description of the data in the measured region of phase space most sensitive to these effects. These results provide an important constraint on interference models and will guide future model development and tuning.
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Wu, J. J., Molina, R., Oset, E., & Zou, B. S. (2010). Prediction of Narrow N* and Lambda* Resonances with Hidden Charm above 4 GeV. Phys. Rev. Lett., 105(23), 232001–4pp.
Abstract: The interaction between various charmed mesons and charmed baryons is studied within the framework of the coupled-channel unitary approach with the local hidden gauge formalism. Several meson-baryon dynamically generated narrow N* and Lambda* resonances with hidden charm are predicted with mass above 4 GeV and width smaller than 100 MeV. The predicted new resonances definitely cannot be accommodated by quark models with three constituent quarks and can be looked for in the forthcoming PANDA/FAIR experiments.
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BABAR Collaboration(Lees, J. P. et al), Martinez-Vidal, F., & Oyanguren, A. (2020). Precision Measurement of the Ratio B(gamma(3S) -> tau(+)tau(-))/B(gamma(3S) -> mu(+)mu(-)). Phys. Rev. Lett., 125(24), 241801–7pp.
Abstract: We report on a precision measurement of the ratio R-tau mu(gamma(3s)) = B(gamma(3S) -> tau(+)tau(-))/B(tau(gamma(3S) ->mu(+)mu(-)) using data collected with the BABAR detector at the SLAC PEP-II e(+)e(-) collider. The measurement is based on a 28 fb(-1) data sample collected at a center-of-mass energy of 10.355 GeV corresponding to a sample of 122 million gamma(35) mesons. The ratio is measured to be R-tau mu(gamma(3s)) = 0.966 +/- 0.008(stat) +/- 0.014(syst) and is in agreement with the standard model prediction of 0.9948 within 2 standard deviations. The uncertainty in R-tau mu(gamma(3s)) is almost an order of magnitude smaller than the only previous measurement.
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LHCb Collaboration(Aaij, R. et al), Martinez-Vidal, F., Oyanguren, A., Ruiz Valls, P., & Sanchez Mayordomo, C. (2014). Precision Measurement of the Mass and Lifetime of the Xi(0)(b) Baryon. Phys. Rev. Lett., 113(3), 032001–10pp.
Abstract: Using a proton-proton collision data sample corresponding to an integrated luminosity of 3 fb(-1) collected by LHCb at center-of-mass energies of 7 and 8 TeV, about 3800 Xi(0)(b) -> Xi(+)(c)pi(-), Xi(+)(c) -> pK(-)pi(+) signal decays are reconstructed. From this sample, the first measurement of the Xi(0)(b) baryon lifetime is made, relative to that of the Lambda(0)(b) baryon. The mass differences M(Xi(0)(b)) – M(Lambda(0)(b)) and M(Xi(+)(c)) – M(Lambda(+)(c)) are also measured with precision more than 4 times better than the current world averages. The resulting values are tau(Xi b0)/tau(Lambda b0) = 1.006 +/- 0.018 +/- 0.010, M(Xi(0)(b)) – M(Lambda(0)(b)) = 172.44 +/- 0.39 +/- 0.17 MeV/c(2), M(Xi(+)(c)) – M(Lambda(+)(c)) = 181.51 +/- 0.14 +/- 0.10 MeV/c(2), where the first uncertainty is statistical and the second is systematic. The relative rate of Xi(0)(b) to Lambda(0)(b) baryon production is measured to be f(Xi b0) B(Xi(0)(b) -> Xi(+)(c)pi(-)) B(Xi(+)(c) -> pK(-)pi(+))/f(Lambda b0) B(Lambda(0)(b) -> Lambda(+)(c)pi(-)) B(Lambda(+)(c) -> pK(-)pi(+)) = (1.88 +/- 0.04 +/- 0.03) x 10(-2), where the first factor is the ratio of fragmentation fractions, b -> Xi(0)(b) relative to b -> Lambda(0)(b). Relative production rates as functions of transverse momentum and pseudorapidity are also presented.
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LHCb Collaboration(Aaij, R. et al), Martinez-Vidal, F., Oyanguren, A., Ruiz Valls, P., & Sanchez Mayordomo, C. (2014). Precision Measurement of the Mass and Lifetime of the Xi(-)(b) Baryon. Phys. Rev. Lett., 113(24), 242002–9pp.
Abstract: We report on measurements of the mass and lifetime of the Xi(-)(b) baryon using about 1800 Xi(-)(b) decays reconstructed in a proton-proton collision data set corresponding to an integrated luminosity of 3.0 fb(-1) collected by the LHCb experiment. The decays are reconstructed in the Xi(-)(b) -> Xi(0)(c)pi(-), Xi(0)(c) -> pK(-)K(-)pi(+) channel and the mass and lifetime are measured using the Lambda(0)(b) -> Lambda(+)(c)pi(-) mode as a reference. We measure M(Xi(-)(b)) – M(Lambda(0)(b)) = 178.36 +/- 0.46 +/- 0.16 MeV/c(2), (tau Xi(-)(b)/tau Lambda(0)(b)) = 1.089 +/- 0.026 +/- 0.011, where the uncertainties are statistical and systematic, respectively. These results lead to a factor of 2 better precision on the Xi(-)(b) mass and lifetime compared to previous best measurements, and are consistent with theoretical expectations.
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BABAR Collaboration(Lees, J. P. et al), Martinez-Vidal, F., & Oyanguren, A. (2012). Precision Measurement of the B -> Xs gamma Photon Energy Spectrum, Branching Fraction, and Direct CP Asymmetry ACP(B -> Xs+d gamma). Phys. Rev. Lett., 109(19), 191801–8pp.
Abstract: The photon spectrum in the inclusive electromagnetic radiative decays of the B meson, B --> X-s gamma plus B --> X-d gamma, is studied using a data sample of (382.8 +/- 4.2) x 10(6)Y(4S) --> B (B) over bar decays collected by the BABAR experiment at SLAC. The spectrum is used to extract the branching fraction B(B --> X-s gamma) = (3.21 +/- 0.33) x 10(-4) for E-gamma > 1.8 GeV and the direct CP asymmetry A(CP)(B --> Xs+d gamma) = 0.057 +/- 0.063. The effects of detector resolution and Doppler smearing are unfolded to measure the photon energy spectrum in the B meson rest frame.
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Borexino Collaboration(Bellini, G. et al), & Pena-Garay, C. (2011). Precision Measurement of the (7)Be Solar Neutrino Interaction Rate in Borexino. Phys. Rev. Lett., 107(14), 141302–5pp.
Abstract: The rate of neutrino-electron elastic scattering interactions from 862 keV (7)Be solar neutrinos in Borexino is determined to be 46.0 +/- 1.5(stat)(-1.6)(+1.5)(syst)counts/(day . 100 ton). This corresponds to a nu(e)-equivalent (7)Be solar neutrino flux of (3.10 +/- 0.15) x 10(9) cm(-2) s(-1) and, under the assumption of nu(e) transition to other active neutrino flavours, yields an electron neutrino survival probability of 0.51 +/- 0.07 at 862 keV. The no flavor change hypothesis is ruled out at 5.0 sigma. A global solar neutrino analysis with free fluxes determines Phi(pp) = 6.06(-0.66)(+0.02) x 10(10) cm(-2) s(-1) and Phi(CNO) < 1.3 x 10(9) cm(-2) s(-1) (95% C.L.). These results significantly improve the precision with which the Mikheyev-Smirnov-Wolfenstein large mixing angle neutrino oscillation model is experimentally tested at low energy.
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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). Precision Measurement of CP Violation in the Penguin-Mediated Decay B0s → φφ. Phys. Rev. Lett., 131(17), 171802–12pp.
Abstract: A flavor-tagged time-dependent angular analysis of the decay B0s -> phi phi is performed using pp collision integrated luminosity of 6 fb-1. The CP-violating phase and direct CP-violation parameter are measured to s = -0.042 +/- 0.075 +/- 0.009 rad and l lambda l = 1.004 +/- 0.030 +/- 0.009, respectively, assuming the same values for all polarization states of the phi phi system. In these results, the first uncertainties are statistical and the second systematic. These parameters are also determined separately for each polarization state, showing no evidence for polarization dependence. The results are combined with previous LHCb measurements using pp collisions at center-of-mass energies of 7 and 8 TeV, yielding phi sss over bar s = -0.074 +/- 0.069 rad and l lambda l = 1.009 +/- 0.030. This is the most precise study of time-dependent CP violation in a penguindominated B meson decay. The results are consistent with CP symmetry and with the standard model predictions.
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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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