Resonances and CP violation in B-s(0) and (B)over-bar(s)(0) -> j psi K+K- decays in the mass region above the I center dot(1020)

The decays of B (s) (0) and mesons into the J/psi K (+) K (-) final state are studied in the K (+) K (-) mass region above the I center dot(1020) meson in order to determine the resonant substructure and measure the CP-violating phase, I center dot (s) , the decay width, I" (s) , and the width difference between light and heavy mass eigenstates, Delta I" (s) . A decay-time dependent amplitude analysis is employed. The data sample corresponds to an integrated luminosity of 3 fb(-1) produced in 7 and 8 TeV pp collisions at the LHC, collected by the LHCb experiment. The measurement determines I center dot (s) = 119 +/- 107 +/- 34 mrad. A combination with previous LHCb measurements using similar decays into the J/psi pi (+) pi (-) and J/psi I center dot(1020) final states gives I center dot (s) = 1 +/- 37 mrad, consistent with the Standard Model prediction.

Precision Measurement of CP Violation in B-S(0) -> J/Psi K+K- Decays

Liupan An, Aurelio Bay, Marc-Olivier Bettler, Frédéric Blanc, Peter Clarke, Victor Coco, Greig Alan Cowan, Adam Davis, Michel De Cian, Hans Dijkstra, Mirco Dorigo, Frédéric Guillaume Dupertuis, Paolo Durante, Christoph Frei, Sebastiana Gianì, Elena Graverini, Guido Haefeli, Xiaoxue Han, Pierre Jaton, Chitsanu Khurewathanakul, Ilya Komarov, Yiming Li, Alessandro Mapelli, Pietro Marino, Maurizio Martinelli, Bastien Luca Muster, Tatsuya Nakada, Matthew Needham, Niko Neufeld, Luca Pescatore, Cédric Potterat, Jessica Prisciandaro, Barinjaka Rakotomiaramanana, Gerhard Raven, Federico Leo Redi, Julien Rouvinet, Olivier Schneider, Liang Sun, Frédéric Teubert, Mark Tobin, Minh Tâm Tran, Jian Wang, Zhirui Xu, Yi Zhang, Lei Zhang

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.

Amer Physical Soc2015

LHCb Detector Momentum Calibration with the First Year Data and a Performance Study of CP Violation Measurement with the B°s -> J/[Psi][Phi] Decays

Géraldine Conti

A new area in particle physics has begun with the start of the Large Hadron Collider (LHC) at CERN at the end of 2009, which collides protons at energies never reached before. To detect the products of the collisions, four main experiments are located around the LHC, among which the LHCb experiment. LHCb has been designed as a single-arm forward spectrometer and is dedicated to measurements of CP violation and rare decays of B hadrons. These searches could also potentially lead to the discovery of phenomena that cannot be described by the model used to date, called the Standard Model. The physics beyond the Standard Model is referred to as New Physics. A measurement of the phase of the Bs0–Bs0 oscillation amplitude with respect to that of the b → c+W- tree decay amplitude, called , is one of the key goals of the LHCb experiment with first data. In the Standard Model, this phase equals –2βs, with βs the smallest angle of the unitary triangle of the CKM matrix relevant to Bs0. The phase is hence predicted to be small, rad. However, possible contributions of New Physics to the Bs0–Bs0 box diagram, such as new particles entering into it, could modify the value from its Standard Model expectation. Due to its very small theoretical uncertainty in the Standard Model, is therefore a very sensitive probe to detect the presence of New Physics. The phase will be measured from a time-dependent angular analysis to Bs0 → J/ψφ events with tagging the initial flavor of the Bs0 mesons. Due to the pseudo-scalar to vector-vector particle nature of the decay, an angular analysis is required to disentangle statistically the CP-even and CP-odd components present in the final state. Already with 2 fb-1 of data taken at the nominal luminosity ℒ = 2·1032 cm2s-1, corresponding to ∼ 117,000 Bs0 → J/ψφ signal events, the LHCb experiment is expected to achieve a statistical uncertainty σ() ≃ 0.03 rad, similar to the value predicted by the Standard Model. On the way to this measurement, we present prospects for the time-dependent angular analysis to Bs0 → J/ψφ events without tagging the initial flavor of the Bs0 mesons. This analysis is less sensitive to , but it has the advantages of being independent of the tagging calibration and less stringent about the proper time resolution, as it does not have to resolve the fast Bs0–Bs0 oscillations. Consequently, it can be applied on first data. Sensitivity results for , but also for the other parameters entering in the analysis are given. In particular, the amplitudes of the CP-even and CP-odd components and the Bs0 meson lifetime can already be measured with a better precision than the latest CDF results (June 2010) with only 0.2 fb-1 of data at nominal luminosity with the untagged analysis. To perform this analysis, the trajectories through the spectrometer of the particles coming from the Bs0 → J/ψ(µ+µ-)φ(Κ +Κ-) decay, the muons and kaons, need to be reconstructed very precisely. Indeed, from the curvature of their trajectory in the magnetic field, the momentum of the particles is obtained, which is then used in the calculation of the angles forming the basis for the angular analysis to Bs0 → J/ψφ events. For particles flying in the innermost part of LHCb, the Inner Tracker is the detector that provides information about the tracks. It consists of twelve detector boxes fixed on three tracking stations located downstream of the magnet in a cross-shaped configuration around the beam pipe. They are each filled with four layers of silicon microstrip sensors. We have assembled the twelve Inner Tracker detector boxes in a clean environment at CERN. By summer 2008, they were all assembled and installed in the LHCb cavern. To reconstruct track trajectories very accurately, two ingredients are essential: a good alignment description of the detectors used for tracking and an accurate description of the magnetic field. Before closing the Inner Tracker detector boxes, we organized with the survey team at CERN measurements of the silicon sensor positions. Once installed in the LHCb cavern, the Inner Tracker detector boxes were aligned as close to their nominal position as possible on the tracking stations previously adjusted. From the final measurements, we provided to the LHCb software a first realistic geometry description of the Inner Tracker, which was validated using particles coming from LHC injection tests of September 2008 and June 2009. The magnetic field map used initially in the LHCb software had been generated with a model based on finite element calculation. To obtain a better magnetic field map description, we developed a method for parameterizing magnetic field measurements that were recorded in December 2005 in the LHCb cavern using Hall probes. This new map replaced the former field map in the LHCb software. However, the magnetic field measurements showed some different features compared to the simulated magnetic field values, which needed to be validated with real data. As an example, an asymmetry of the magnetic field between the lower and upper parts of the magnet is observed in the measurements, while simulated values do not have this by design of the dipole magnet. Using reconstructed masses of Κs → π+π-, Λ → p+π- and Λ → p-π+ decays coming from 2009 and early 2010 real data, we validated the magnetic field map based on the measurements against the one based on simulated values according to several criteria, one of which being the confirmation of the up-down asymmetry in the field. From the same studies, we calculated a factor to correct globally for the momentum scale. As this factor should be universal, it can be calculated for one resonance and validated using the results for other resonances.

EPFL2010

Measurement of CP violation and the B-s(0) meson decay width difference with B-s(0) -> J/psi K+K- and B-s(0) -> J/psi pi(+) pi(-)decays

Vladislav Balagura, Aurelio Bay, Marc-Olivier Bettler, Frédéric Blanc, Joël Bressieux, Peter Clarke, Victor Coco, Greig Alan Cowan, Michel De Cian, Hans Dijkstra, Frédéric Guillaume Dupertuis, Vincent Fave, Christoph Frei, Guido Haefeli, Plamen Hristov Hopchev, Pierre Jaton, Anne Keune, Ilya Komarov, Yiming Li, Johan Luisier, Maurizio Martinelli, Raluca Anca Muresan, Bastien Luca Muster, Tatsuya Nakada, Matthew Needham, Niko Neufeld, Cédric Potterat, Jessica Prisciandaro, Albert Puig Navarro, Barinjaka Rakotomiaramanana, Gerhard Raven, Julien Rouvinet, Christophe Salzmann, Olivier Schneider, Frédéric Teubert, Mark Tobin, Minh Tâm Tran, Jian Wang, Jean Wicht, Songmei Wu, Yi Zhang, Lei Zhang

The time-dependent CP asymmetry in B-s(0) -> J/psi K+ K- decays is measured using pp collision data at root s = 7 TeV, corresponding to an integrated luminosity of 1: 0 fb(-1), collected with the LHCb detector. The decay-time distribution is characterized by the decay widths Gamma(L) and Gamma(H) of the light and heavy mass eigenstates of the B-s(0) - (B) over barB(s)(0) system and by a CP-violating phase s. In a sample of 27 617 B-s(0) -> J/psi K+ K- decays, where the dominant contribution comes from B-s(0) -> J/psi K+ K- decays, these parameters are measured to be phi(s) = 0. 07 +/- 0.09(stat) +/- 0. 01(syst) rad, Gamma(s) equivalent to (Gamma(L) + Gamma(L))/2 = 0.663 +/- 0.005(stat) +/- 0.006(syst) ps(-1), and 0.006(syst) ps(-1), and Delta Gamma(s) equivalent to Gamma(L) - Gamma(L) = 0.100 +/- 0.016(stat) +/- 0.003(syst) ps(-1), corresponding to the single most precise determination of phi(s), Delta Gamma(s), and Gamma(s.). The result of performing a combined analysis with B-s(0) -> J/psi pi(+) pi(-) decays gives phi(s) = 0.01 +/- 0.07(stat) +/- 0.01(syst)rad, Gamma(s) = 0.661 +/- 0.004(stat) +/- 0.006(syst) ps(-1), and Delta Gamma(s) = 0.106 +/- 0.011(stat) +/- 0.007(syst) ps(-1). All measurements are in agreement with the Standard Model predictions.

Amer Physical Soc2013

LHCb Detector Momentum Calibration with the First Year Data and a Performance Study of CP Violation Measurement with the B°s -> J/[Psi][Phi] Decays

Géraldine Conti

EPFL2010