The LHCb experiment is dedicated to precision measurements of CP violation and rare decays of B hadrons at the Large Hadron Collider (LHC) at CERN (Geneva). The initial configuration and expected performance of the detector and associated systems, as established by test beam measurements and simulation studies, is described.
T2K (Tokai to Kamioka) is a long baseline neutrino experiment with the primary goal of measuring the neutrino mixing angle θ 13 . It uses a muon neutrino beam, produced at the J-PARC accelerator facility in Tokai, sent through a near detector complex on its way to the far detector, Super-Kamiokande. Appearance of electron neutrinos at the far detector due to oscillation is used to measure the value of θ 13 .
The T2K experiment is a long baseline neutrino oscillation experiment. Its main goal is to measure the last unknown lepton sector mixing angle θ13θ13 by observing νeνe appearance in a νμνμ beam. It also aims to make a precision measurement of the known oscillation parameters, View the MathML sourceΔm232 and sin22θ23sin22θ23, via νμνμ disappearance studies. Other goals of the experiment include various neutrino cross-section measurements and sterile neutrino searches. The experiment uses an intense proton beam generated by the J-PARC accelerator in Tokai, Japan, and is composed of a neutrino beamline, a near detector complex (ND280), and a far detector (Super-Kamiokande) located 295 km away from J-PARC. This paper provides a comprehensive review of the instrumentation aspect of the T2K experiment and a summary of the vital information for each subsystem
A narrow pentaquark state, P c ð4312Þ þ , decaying to J=ψp, is discovered with a statistical significance of 7.3σ in a data sample of Λ 0 b → J=ψpK − decays, which is an order of magnitude larger than that previously analyzed by the LHCb Collaboration. The P c ð4450Þ þ pentaquark structure formerly reported by LHCb is confirmed and observed to consist of two narrow overlapping peaks, P c ð4440Þ þ and P c ð4457Þ þ , where the statistical significance of this two-peak interpretation is 5.4σ. The proximity of the Σ þ cD 0 and Σ þ cD Ã0 thresholds to the observed narrow peaks suggests that they play an important role in the dynamics of these states.
A measurement of the ratio of branching fractions of the decays B þ → K þ μ þ μ − and B þ → K þ e þ e − is presented. The proton-proton collision data used correspond to an integrated luminosity of 5.0 fb −1 recorded with the LHCb experiment at center-of-mass energies of 7, 8, and 13 TeV. For the dilepton mass-squared range 1.1 < q 2 < 6.0 GeV 2 =c 4 the ratio of branching fractions is measured to be R K ¼ 0.846 þ0.060 −0.054 þ0.016 −0.014 , where the first uncertainty is statistical and the second systematic. This is the most precise measurement of R K to date and is compatible with the standard model at the level of 2.5 standard deviations.
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