956 research outputs found

    Measurement of phi_s at LHCb

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    A time dependent angular analysis of the decay mode Bsβ†’J/ΟˆΟ•B_s \rightarrow J/\psi \phi allows for the measurement of the mixing induced CP-violating phase Ο•s\phi_s. Within the Standard Model Ο•s\phi_s is theoretically precisely predicted to be very small, however many Standard Model extensions predict sizeable contributions to this phase. The current experimental knowledge of Ο•s\phi_s has very larger uncertainties. However already with the data expected to be delivered within the next year, the LHCb experiment at the Large Hadron Collider at CERN, has the potential to improve significantly existing measurements. In a data set of up to 37.5 pbβˆ’1^{-1} taken in 2010, first physics signals in the LHCb detector are reconstructed and their properties are compared to Monte Carlo predictions. Based on recently published measurements of bbΛ‰b\bar{b} cross-sections from the LHCb collaboration, the sensitivity on the CPCP violating phase Ο•s\phi_s in the decay Bsβ†’J/ΟˆΟ•B_s \rightarrow J/\psi \phi is evaluated. Additionally an alternative method to potentially extract complementary information on Ο•s\phi_s from the measurement of the asymmetry in semileptonic final states is presented.Comment: Proceedings of CKM2010, the 6th International Workshop on the CKM Unitarity Triangle, University of Warwick, UK, 6-10 September 201

    Summary of the Heavy Flavor Working Group

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    During the last year many important results have been achieved in heavy flavour physics: New measurements of charm and beauty production have been performed at HERA and the Tevatron. A wealth of new spectroscopy data with several new, unexpected states in the charmonium and the D_s systems has been collected and b to d gamma transitions have been established. The oscillation frequency in the B_s Bbar_s is now measured, and mixing in the D0 D0bar system has been observed. Theoretical progress in the areas of open heavy flavour production, quarkonium production and decays, and multiquark spectroscopy has been presented at this workshop.Comment: 17 pages, 3 figures, to appear in the Proceedings of the XV International Workshop on Deep-Inelastic Scattering and Related Subjectes, DIS 2007, April 16--20, 2007, Munich, German

    Les droits disciplinaires des fonctions publiques : Β« unification Β», Β« harmonisation Β» ou Β« distanciation Β». A propos de la loi du 26 avril 2016 relative Γ  la dΓ©ontologie et aux droits et obligations des fonctionnaires

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    The production of ttβ€Ύ , W+bbβ€Ύ and W+ccβ€Ύ is studied in the forward region of proton–proton collisions collected at a centre-of-mass energy of 8 TeV by the LHCb experiment, corresponding to an integrated luminosity of 1.98Β±0.02Β fbβˆ’1 . The W bosons are reconstructed in the decays Wβ†’β„“Ξ½ , where β„“ denotes muon or electron, while the b and c quarks are reconstructed as jets. All measured cross-sections are in agreement with next-to-leading-order Standard Model predictions.The production of ttβ€Ύt\overline{t}, W+bbβ€ΎW+b\overline{b} and W+ccβ€ΎW+c\overline{c} is studied in the forward region of proton-proton collisions collected at a centre-of-mass energy of 8 TeV by the LHCb experiment, corresponding to an integrated luminosity of 1.98 Β±\pm 0.02 \mbox{fb}^{-1}. The WW bosons are reconstructed in the decays Wβ†’β„“Ξ½W\rightarrow\ell\nu, where β„“\ell denotes muon or electron, while the bb and cc quarks are reconstructed as jets. All measured cross-sections are in agreement with next-to-leading-order Standard Model predictions

    Physics case for an LHCb Upgrade II - Opportunities in flavour physics, and beyond, in the HL-LHC era

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    The LHCb Upgrade II will fully exploit the flavour-physics opportunities of the HL-LHC, and study additional physics topics that take advantage of the forward acceptance of the LHCb spectrometer. The LHCb Upgrade I will begin operation in 2020. Consolidation will occur, and modest enhancements of the Upgrade I detector will be installed, in Long Shutdown 3 of the LHC (2025) and these are discussed here. The main Upgrade II detector will be installed in long shutdown 4 of the LHC (2030) and will build on the strengths of the current LHCb experiment and the Upgrade I. It will operate at a luminosity up to 2Γ—1034 cmβˆ’2sβˆ’1, ten times that of the Upgrade I detector. New detector components will improve the intrinsic performance of the experiment in certain key areas. An Expression Of Interest proposing Upgrade II was submitted in February 2017. The physics case for the Upgrade II is presented here in more depth. CP-violating phases will be measured with precisions unattainable at any other envisaged facility. The experiment will probe b β†’ sl+lβˆ’and b β†’ dl+lβˆ’ transitions in both muon and electron decays in modes not accessible at Upgrade I. Minimal flavour violation will be tested with a precision measurement of the ratio of B(B0 β†’ ΞΌ+ΞΌβˆ’)/B(Bs β†’ ΞΌ+ΞΌβˆ’). Probing charm CP violation at the 10βˆ’5 level may result in its long sought discovery. Major advances in hadron spectroscopy will be possible, which will be powerful probes of low energy QCD. Upgrade II potentially will have the highest sensitivity of all the LHC experiments on the Higgs to charm-quark couplings. Generically, the new physics mass scale probed, for fixed couplings, will almost double compared with the pre-HL-LHC era; this extended reach for flavour physics is similar to that which would be achieved by the HE-LHC proposal for the energy frontier

    LHCb upgrade software and computing : technical design report

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    This document reports the Research and Development activities that are carried out in the software and computing domains in view of the upgrade of the LHCb experiment. The implementation of a full software trigger implies major changes in the core software framework, in the event data model, and in the reconstruction algorithms. The increase of the data volumes for both real and simulated datasets requires a corresponding scaling of the distributed computing infrastructure. An implementation plan in both domains is presented, together with a risk assessment analysis

    Multidifferential study of identified charged hadron distributions in ZZ-tagged jets in proton-proton collisions at s=\sqrt{s}=13 TeV

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    Jet fragmentation functions are measured for the first time in proton-proton collisions for charged pions, kaons, and protons within jets recoiling against a ZZ boson. The charged-hadron distributions are studied longitudinally and transversely to the jet direction for jets with transverse momentum 20 <pT<100< p_{\textrm{T}} < 100 GeV and in the pseudorapidity range 2.5<Ξ·<42.5 < \eta < 4. The data sample was collected with the LHCb experiment at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 1.64 fbβˆ’1^{-1}. Triple differential distributions as a function of the hadron longitudinal momentum fraction, hadron transverse momentum, and jet transverse momentum are also measured for the first time. This helps constrain transverse-momentum-dependent fragmentation functions. Differences in the shapes and magnitudes of the measured distributions for the different hadron species provide insights into the hadronization process for jets predominantly initiated by light quarks.Comment: All figures and tables, along with machine-readable versions and any supplementary material and additional information, are available at https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2022-013.html (LHCb public pages

    Study of the Bβˆ’β†’Ξ›c+Ξ›Λ‰cβˆ’Kβˆ’B^{-} \to \Lambda_{c}^{+} \bar{\Lambda}_{c}^{-} K^{-} decay