|
Botella, F. J., Garcia Martin, L. M., Marangotto, D., Martinez-Vidal, F., Merli, A., Neri, N., et al. (2017). On the search for the electric dipole moment of strange and charm baryons at LHC. Eur. Phys. J. C, 77(3), 181–15pp.
Abstract: Permanent electric dipole moments (EDMs) of fundamental particles provide powerful probes for physics beyond the Standard Model. We propose to search for the EDM of strange and charm baryons at LHC, extending the ongoing experimental program on the neutron, muon, atoms, molecules and light nuclei. The EDM of strange. baryons, selected from weak decays of charm baryons produced in pp collisions at LHC, can be determined by studying the spin precession in the magnetic field of the detector tracking system. A test of CPT symmetry can be performed by measuring the magnetic dipole moment of. and. baryons. For short-lived Lambda(+)(c) and Xi(+)(c) baryons, to be produced in a fixedtarget experiment using the 7 TeV LHC beam and channeled in a bent crystal, the spin precession is induced by the intense electromagnetic field between crystal atomic planes. The experimental layout based on the LHCb detector and the expected sensitivities in the coming years are discussed.
|
|
|
LHCb Collaboration(Aaij, R. et al), Martinez-Vidal, F., Oyanguren, A., Ruiz Valls, P., & Sanchez Mayordomo, C. (2016). Observations of Lambda(0)(b) -> Lambda K+pi(-) and Lambda(0)(b) -> Lambda K+K- decays and searches for other Lambda(0)(b) and Xi(0)(b) decays to Lambda h(+)h '(-) final states. J. High Energy Phys., 05(5), 081–22pp.
Abstract: A search is performed for the charmless three-body decays of the Lambda(0)(b) and Xi(0)(b) baryons to the final states Lambda h(+)h'(-), where h(') = pi or K. The analysis is based on a data sample, corresponding to an integrated luminosity of 3 fb-1 of pp collisions, collected by the LHCb experiment. The Lambda(0)(b) -> Lambda K+pi(-) and Lambda(0)(b) -> Lambda K+K- decays are observed for the first time and their branching fractions and CP asymmetry parameters are measured. Evidence is seen for the Lambda(0)(b) -> Lambda pi(+)pi(-) decay and limits are set on the branching fractions of Xi(0)(b) baryon decays to the Lambda h(+)h(-) final states.
|
|
|
LHCb Collaboration(Aaij, R. et al), Oyanguren, A., & Ruiz Valls, P. (2013). Observations of B-S(0) ->psi(2S)eta and B-(s)(0) ->psi(2S)pi(+)pi(-) decays. Nucl. Phys. B, 871(3), 403–419.
Abstract: First observations of the B-S(0) ->psi(2S)eta, B-(s)(0) ->psi(2S)pi(+)pi(-) decays are made using a dataset corresponding to an integrated luminosity of 1.0 fb(-1) collected by the LHCb experiment in proton proton collisions at a centre-of-mass energy of root s = 7 TeV. The ratios of the branching fractions of each of the *(2S) modes with respect to the corresponding J/psi decays are B(B-s(0) ->psi(2S)eta)/B(B-s(0) -> J(2S)eta) = 0.83 +/- 0.14 (stat) +/- 0.12 (B), B(B0 ->psi(2S)pi(+)pi(-))/B(B0 -> J/psi pi(+)pi(-)) = 0.56 +/- 0.07 (stat) +/- 0.05 (syst) +/- 0.01 (B), B(B0 ->psi(2S)pi(+)pi(-))/B(B-s(0) -> J/psi pi(+)pi(-)) = 0.34 +/- 0.04 (stat) +/- 0.03 (syst) +/- 0.01 (B). where the third uncertainty corresponds to the uncertainties of the dilepton branching fractions of the J/* and psi(28) meson decays.
|
|
|
LHCb Collaboration(Aaij, R. et al), Martinez-Vidal, F., Oyanguren, A., Ruiz Valls, P., & Sanchez Mayordomo, C. (2014). Observation of Z production in proton-lead collisions at LHCb. J. High Energy Phys., 09(9), 030–18pp.
Abstract: The first observation of Z boson production in proton-lead collisions at a centre-of-mass energy per proton-nucleon pair of root(s) N N = 5TeV is presented. The data sample corresponds to an integrated luminosity of 1.6 nb(-1) collected with the LHCb detector. The Z candidates are reconstructed from pairs of oppositely charged muons with pseudorapidities between 2.0 and 4.5 and transverse momenta above 20 GeV/c. The invariant dimuon mass is restricted to the range 60-120 GeV/c. The Z production cross-section is measured to be sigma(Z ->mu+mu-) (fwd) = 13.5(-4.0)(+5.4)(stat.) +/- 1.2(syst.) nb in the direction of the proton beam and sigma(Z ->mu+mu-) (bwd) = 10.7(-5.1)(+8.4)(stat.) +/- 1.0(syst.) nb in the direction of the lead beam, where the first uncertainty is statistical and the second systematic.
|
|
|
LHCb Collaboration(Aaij, R. et al), Garcia Martin, L. M., Henry, L., Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., et al. (2019). Observation of Two Resonances in the Lambda(0)(b)pi(+/-) Systems and Precise Measurement of Sigma(+/-)(b) and Sigma(*+/-)(b) Properties. Phys. Rev. Lett., 122(1), 012001–9pp.
Abstract: The first observation of two structures consistent with resonances in the final states Lambda(0)(b)pi(-) and Lambda(0)(b)pi(+) thorn is reported using samples of pp collision data collected by the LHCb experiment at root s = 7 and 8 TeV, corresponding to an integrated luminosity of 3 fb(-1). The ground states Sigma(+/-)(b) and Sigma(*+/-)(b) are also confirmed and their masses and widths are precisely measured.
|
|
|
LHCb Collaboration(Aaij, R. et al), Martinez-Vidal, F., Oyanguren, A., Ruiz Valls, P., & Sanchez Mayordomo, C. (2015). Observation of Two New Xi(-)(b) Baryon Resonances. Phys. Rev. Lett., 114(6), 062004–9pp.
Abstract: Two structures are observed close to the kinematic threshold in the Xi(0)(b)pi(-) mass spectrum in a sample of proton-proton collision data, corresponding to an integrated luminosity of 3.0 fb(-1), recorded by the LEICb experiment. In the quark model, two baryonic resonances with quark content bds are expected in this mass region: the spin-parity J(P) = (1/2)(+) and J(P) = (3/2)(+) states, denoted Xi'(-)(b) and Xi*(-)(b). Interpreting the structures as these resonances, we measure the mass differences and the width of the heavier state to be m(Xi'(-)(b)) – m(Xi(0)(b)) – m(pi(-))=3.653 +/- 0.018 +/- 0.006 MeV/c(2), m(Xi*(-)(b)) – m(Xi(0)(b)) – m(pi(-)) = 23.96 +/- 0.12 +/- 0.06 MeV/e(2), Gamma(Xi*(-)(b)) = 1.65 +/- 0.31 +/- 0.10 MeV, where the first and second uncertainties are statistical and systematic, respectively. The width of the lighter state is consistent with zero, and we place an upper limit of Gamma(Xi'(-)(b)) < 0.08 MeV at 95% confidence level. Relative production rates of these states are also reported.
|
|
|
LHCb Collaboration(Aaij, R. et al), Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., & Ruiz Vidal, J. (2022). Observation of two new excited Ξ0b states decaying to Λ0bK−π+. Phys. Rev. Lett., 128(16), 162001–12pp.
Abstract: Two narrow resonant states are observed in the Λ0bK−π+ mass spectrum using a data sample of proton-proton collisions at a center-of-mass energy of 13 TeV, collected by the LHCb experiment and corresponding to an integrated luminosity of 6 fb−1. The minimal quark content of the Λ0bK−π+ system indicates that these are excited Ξ0b baryons. The masses of the Ξb(6327)0 and Ξb(6333)0 states are m(Ξb(6327)0)=6327.28+0.23−0.21±0.12±0.24 MeV and m(Ξb(6333)0)=6332.69+0.17−0.18±0.03±0.22 MeV, respectively, with a mass splitting of Δm=5.41+0.26−0.27±0.12 MeV, where the uncertainties are statistical, systematic and due to the Λ0b mass measurement. The measured natural widths of these states are consistent with zero, with upper limits of Γ(Ξb(6327)0)<2.20 (2.56) MeV and Γ(Ξb(6333)0)<1.60 (1.92) MeV at a 90% (95%) credibility level. The significance of the two-peak hypothesis is larger than nine (five) Gaussian standard deviations compared to the no-peak (one-peak) hypothesis. The masses, widths and resonant structure of the new states are in good agreement with the expectations for a doublet of 1D Ξ0b resonances.
|
|
|
BABAR Collaboration(Lees, J. P. et al), Bernabeu, J., Martinez-Vidal, F., Oyanguren, A., & Villanueva-Perez, P. (2012). Observation of Time-Reversal Violation in the B-0 Meson System. Phys. Rev. Lett., 109(21), 211801–8pp.
Abstract: Although CP violation in the B meson system has been well established by the B factories, there has been no direct observation of time-reversal violation. The decays of entangled neutral B mesons into definite flavor states (B-0 or (B) over bar (0)), and J/psi K-L(0) or c (c) over barK(S)(0) final states (referred to as B+ or B-), allow comparisons between the probabilities of four pairs of T-conjugated transitions, for example, (B) over bar (0) -> B- and B- -> (B) over bar (0), as a function of the time difference between the two B decays. Using 468 X 10(6) B (B) over bar pairs produced in Y(4S) decays collected by the BABAR detector at SLAC, we measure T-violating parameters in the time evolution of neutral B mesons, yielding Delta S-T(+) = -137 +/- 0.14(stat) +/- 0.06(syst) and Delta S-T(-) = 1.17 +/- 0.18(stat) +/- 0.11(syst). These nonzero results represent the first direct observation of T violation through the exchange of initial and final states in transitions that can only be connected by a T-symmetry transformation.
|
|
|
BABAR Collaboration(del Amo Sanchez, P. et al), Lopez-March, N., Martinez-Vidal, F., Milanes, D. A., & Oyanguren, A. (2010). Observation of the Y(1(3)D(J)) bottomonium state through decays to pi(+)pi Y-(1S). Phys. Rev. D, 82(11), 111102–7pp.
Abstract: Based on 122 X 10(6)Y(3S) events collected with the BABAR detector, we have observed the Y(1(3)D(J)) bottomonium state through the Y(3S) -> gamma gamma Y(1(3)D(J)) -> gamma gamma pi(+)pi Y-(1S) decay chain. The significance for the J = 2 member of the Y(1(3)D(J)) triplet is 5.8 standard deviations including systematic uncertainties. The mass of the J = 2 state is determined to be 10 164.5 +/- 0.8(stat) +/- 0.5(syst) MeV/c(2). We use the pi(+)pi(-) invariant mass distribution to confirm the consistency of the observed state with the orbital angular momentum assignment of the Y(1(3)D(J)).
|
|
|
LHCb Collaboration(Aaij, R. et al), Garcia Martin, L. M., Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., Ruiz Valls, P., et al. (2017). Observation of the Xi(-)(b) -> J/psi Lambda K- decay. Phys. Lett. B, 772, 265–273.
Abstract: The observation of the decay Xi(-)(b)-> J/psi Lambda K- is reported, using a data sample corresponding to an integrated luminosity of 3 fb(-1), collected by the LHCb detector in pp collisions at centre-of-mass energies of 7 and 8 TeV. The production rate of Xi(-)(b) baryons detected in the decay Xi(-)(b) -> J/psi Lambda K- is measured relative to that of Lambda(0)(b) baryons using the decay Lambda(0)(b) -> J/psi Lambda. Integrated over the b-baryon transverse momentum p(T) < 25 GeV/c and rapidity 2.0 < y < 4.5, the measured ratio is f Xi(-)(b/) f Lambda(0)(b) B(Xi(-)(b)-> J/psi Lambda K-) / B(Lambda(0)(b)-> J/psi Lambda) = (4.19 +/- 0.29 (stat) +/- 0.15 (syst)) x 10(-2), where f(Xi)(b)(-) band f(Lambda)(b)(0)are the fragmentation fractions of b ->Xi(-)(b)and b ->Lambda(0)(b)transitions, and ss represents the branching fraction of the corresponding b- baryon decay. The mass difference between Xi(-)(b) and Lambda(0)(b) baryons is measured to be M(Xi(-)(b))-M(Lambda(0)(b)) = 177.08 +/- 0.47 (stat) +/- 0.16 (syst) MeV/c(2).
|
|