Development of an optical front-end readout system for the LHCb RICH detectors.

The development of a front-end readout system for the LHCb Ring Imaging Cherenkov (RICH) detectors is in progress. The baseline choice for the RICH photon detector front-end electronics is a binary readout ASIC for an encapsulated silicon pixel detector. This paper describes a system to transmit the binary data with address ID and error codes, from a radiation harsh environment while keeping synchronisation. The total data read out for the fixed Level-0 readout period of 900ns is 32x36x440 non-zero-suppressed bits per Level-0 trigger, with a sustained Level-0 trigger rate of 1MHz. Multimode fibres driven by VCSEL devices are used to transmit data to the off-detector Level-1 electronics located in a non-radiation environment. The data are stored in 512Kbit deep QDR buffers

A precise measurement of the B0 meson oscillation frequency

The oscillation frequency, Δ md, of B0 mesons is measured using semileptonic decays with a D- or D∗- meson in the final state. The data sample corresponds to 3.0fb-1 of pp collisions, collected by the LHCb experiment at centre-of-mass energies √s = 7 and 8 TeV. A combination of the two decay modes gives Δmd = (505.0 ± 2.1 ± 1.0) ns-1, where the first uncertainty is statistical and the second is systematic. This is the most precise single measurement of this parameter. It is consistent with the current world average and has similar precision

TWO NON-KOLMOGOROVIAN GENERALIZATIONS OF REICHENBACH'S COMMON CAUSE DEFINITION

Given a probabilistic correlation between two events, this correlation might be explained in terms of a common cause. In [1] Reichenbach defines the notion of common cause and shows that the definition is consistent with the explicable correlation, i.e. if two events have a common cause then they do correlate. In this paper we generalize the notion of common cause to Hilbert lattices in two different ways according to the two different definitions of conditional probability in the quantum case, and show that Reichenbach's theorem does not hold in either case. There will be given counter-examples when a common cause 'causes' correlation, anticorrelation and independence, respectively

Measurement of the properties of the Ξ∗0b baryon

We perform a search for near-threshold Ξb0 resonances decaying to Ξb−π+ in a sample of proton-proton collision data corresponding to an integrated luminosity of 3 fb−1 collected by the LHCb experiment. We observe one resonant state, with the following properties: m(Ξ∗0b) − m(Ξ−b) − m(π+) = 15.727 ± 0.068(stat) ± 0.023(syst) MeV/c2 Γ(Ξ∗0b) = 0.90 ± 0.16(stat) ± 0.08(syst) MeV. This confirms the previous observation by the CMS collaboration. The state is consistent with the JP = 3/2+  Ξb∗ 0 resonance expected in the quark model. This is the most precise determination of the mass and the first measurement of the natural width of this state. We have also measured the ratio σ(pp→Ξ∗0bX)B(Ξ∗0b→Ξ−bπ+)/σ(pp → Ξ−bX) =0.28 ± 0.03(stat.) ± 0.01(syst.)

Measurement of forward W and Z boson production in association with jets in proton-proton collisions at √s = 8 TeV

The production of W and Z bosons in association with jets 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 ± 0.02 fb−1. The W boson is identified using its decay to a muon and a neutrino, while the Z boson is identified through its decay to a muon pair. Total cross-sections are measured and combined into charge ratios, asymmetries, and ratios of W +jet and Z+jet production cross-sections. Differential measurements are also performed as a function of both boson and jet kinematic variables. All results are in agreement with Standard Model predictions

Observation of the Λ0b → Λφ decay

The Λ0b → Λφ decay is observed using data corresponding to an integrated luminosity of 3.0 fb^-1 recorded by the LHCb experiment. The decay proceeds at leading order via a b → sss loop transition and is therefore sensitive to the possible presence of particles beyond the Standard Model. A first observation is reported with a significance of 5.9 standard deviations. The value of the branching fraction is measured to be (5.18 ± 1.04 ± 0.35^+0.67-0.62) X 10^-6, where the first uncertainty is statistical, the second is systematic, and the third is related to external inputs. Triple-product asymmetries are measured to be consistent with zero

Search for Higgs-like bosons decaying into long-lived exotic particles

A search is presented for massive long-lived particles, in the 20-60 GeV/c2 mass range with lifetimes between 5 and 100 ps. The dataset used corresponds to 0.62 fb^-1 of proton-proton collision data collected by the LHCb detector at √s = 7 TeV. The particles are assumed to be pair-produced by the decay of a Higgs-like boson with mass between 80 and 140 GeV/c2. No excess above the background expectation is observed and limits are set on the production cross-section as a function of the long-lived particle mass and lifetime and of the Higgs-like boson mass

Search for B+c decays to the ppπ+ final state

A search for the decays of the B+c meson to ppπ+ is performed for the first time using a data sample corresponding to an integrated luminosity of 3.0 fb-1 collected by the LHCb experiment in pp collisions at centre-of-mass energies of 7 and 8 TeV. No signal is found and an upper limit, at 95% confidence level, is set, fc/fu × B(B+c → ppπ+) < 3.6×10^-8 in the kinematic region m(pp) < 2.85 GeV/c^2, pT(B) < 20 GeV/c and 2.0 < y(B) < 4.5, where B is the branching fraction and fc(fu) is the fragmentation fraction of the b quark into a Bc+ (B+) meson

Measurement of CP observables in B +/- → DK +/- and B +/- → Dπ +/- with two- and four-body D decays

Measurements of CP observables in B± → DK± and B± → Dπ± decays are presented where the D meson is reconstructed in the final states K±π∓, π±K∓, K+K−, π+π−, K±π∓π+π−, π±K∓π+π− and π+π−π+π−. This analysis uses a sample of charged B mesons from pp collisions collected by the LHCb experiment in 2011 and 2012, corresponding to an integrated luminosity of 3.0 fb^−1. Various CP-violating effects are reported and together these measurements provide important input for the determination of the unitarity triangle angle γ. The analysis of the four-pion D decay mode is the first of its kind

First observation of the decay D0 → K−π+μ+μ− in the ρ0–ω region of the dimuon mass spectrum

.A study of the decay D0 → K-π+μ+μ-is performed using data collected by the LHCb detector in proton-proton collisions at a centre-of-mass energy of 8 TeV, corresponding to an integrated luminosity of 2.0 fb^-1. Decay candidates with muon pairs that have an invariant mass in the range 675-875 MeV/c2 are considered. This region is dominated by the ρ0 and ω resonances. The branching fraction in this range is measured to B(D0 → K-π+μ+μ-) = (4.17 ± 0.12(stat) ± 0.40(syst))×10^-6. This is the first observation of the decay D0 → K-π+μ+μ-. Its branching fraction is consistent with the value expected in the Standard Model