First observations of the Cabibbo-suppressed decays B(0) → D(+)K(-)π(+)π(-) and B(-) → D(0)K(-)π(+)π(-) are reported using 35 pb(-1) of data collected with the LHCb detector. Their branching ...fractions are measured with respect to the corresponding Cabibbo-favored decays, from which we obtain B(B(0) → D(+)K(-)π(+)π(-))/B(B(0) → D(+)π(-)π(+)π(-))=(5.9±1.1±0.5)×10(-2) and B(B(-) → D(0)K(-)π(+)π(-))/B(B(-) → D(0)π(-)π(+)π(-))=(9.4±1.3±0.9)×10(-2), where the uncertainties are statistical and systematic, respectively. The B(-) → D(0)K(-)π(+)π(-) decay is particularly interesting, as it can be used in a similar way to B(-) → D(0)K(-) to measure the Cabibbo-Kobayashi-Maskawa phase γ.
The decay B(s)(0) → J/ψK+ K- is investigated using 0.16 fb(-1) of data collected with the LHCb detector using 7 TeV pp collisions. Although the J/ψϕ channel is well known, final states at higher K+ ...K- masses have not previously been studied. In the K+ K- mass spectrum we observe a significant signal in the f(2)'(1525) region as well as a nonresonant component. After subtracting the nonresonant component, we find B(B(s)(0) → J/ψf(2)'(1525))/B(B(s)(0) → J/ψϕ) = (26.4 ± 2.7 ± 2.4)%.
We present a measurement of the time-dependent CP-violating asymmetry in B(s)(0) → J/ψϕ decays, using data collected with the LHCb detector at the LHC. The decay time distribution of B(s)(0) → J/ψϕ ...is characterized by the decay widths Γ(H) and Γ(L) of the heavy and light mass eigenstates, respectively, of the B(s)(0) - B(s)(0) system and by a CP-violating phase ϕ(s). In a sample of about 8500 B(s)(0) → J/ψϕ events isolated from 0.37 fb(-1) of pp collisions at sqrts = 7 TeV, we measure ϕ(s) = 0.15 ± 0.18(stat) ± 0.06(syst) rad. We also find an average B(s)(0) decay width Γ(s) ≡ (Γ(L) + Γ(H))/2 = 0.657 ± 0.009(stat) ± 0.008(syst) ps(-1) and a decay width difference ΔΓ(s) ≡ Γ(L) - Γ(H) = 0.123 ± 0.029(stat) ± 0.011(syst) ps(-1). Our measurement is insensitive to the transformation (ϕ(s),ΔΓ(s)) ↦ (π - ϕ(s), -ΔΓ(s)).
The Large Hadron Collider beauty experiment (LHCb) is a single-arm forward spectrometer dedicated to the study of B-meson decays in p - p collisions at the Large Hadron Collider (LHC). The LHCb ...detector has excellent tracking and particle identification capabilities. The LHCb Silicon Tracker (ST) is composed of two silicon micro-strip detectors with long readout strips. The performance of these two detectors with the first high energy p - p collisions are presented here. A detailed study of the detectors intrinsic resolution and efficiency has been performed along with precise time alignment using collision data. The latest Silicon Tracker performance results and comparison to expectations are presented.
The relative abundance of the three decay modes B(0)→D(-)K(+), B(0)→D(-)π(+), and B(s)(0)→D(s)(-)π(+) produced in 7 TeV pp collisions at the LHC is determined from data corresponding to an integrated ...luminosity of 35 pb(-1). The branching fraction of B(0)→D(-)K(+) is found to be B(B(0)→D(-)K(+)) = (2.01 ± 0.18(stat) ± 0.14(syst)) × 10(-4). The ratio of fragmentation fractions f(s)/f(d) is determined through the relative abundance of B(s)(0)→D(s)(-)π(+) to B(0)→D(-)K(+) and B(0)→D(-)π(+), leading to f(s)/f(d) = 0.253 ± 0.017 ± 0.017 ± 0.020, where the uncertainties are statistical, systematic, and theoretical, respectively.
The LHCb detector will be upgraded to make more efficient use of the available luminosity at the LHC in Run III and extend its potential for discovery. The Ring Imaging Cherenkov detectors are key ...components of the LHCb detector for particle identification. In this paper we describe the setup and the results of tests in a charged particle beam, carried out to assess prototypes of the upgraded opto-electronic chain from the Multi-Anode PMT photosensor to the readout and data acquisition system.
Phys. Rev. D92, 011102 (2015) Angular correlations in $B^+\to X(3872) K^+$ decays, with $X(3872)\to \rho^0
J/\psi$, $\rho^0\to\pi^+\pi^-$ and $J/\psi \to\mu^+\mu^-$, are used to measure
orbital ...angular momentum contributions and to determine the $J^{PC}$ value of
the $X(3872)$ meson. The data correspond to an integrated luminosity of 3.0
fb$^{-1}$ of proton-proton collisions collected with the LHCb detector. This
determination, for the first time performed without assuming a value for the
orbital angular momentum, confirms the quantum numbers to be $J^{PC}=1^{++}$.
The $X(3872)$ is found to decay predominantly through S wave and an upper limit
of $4\%$ at $95\%$ C.L. is set on the fraction of D wave.
The ALEPH detector at LEP has been used to measure the momentum spectrum and charge ratio of vertical cosmic ray muons underground. The sea-level cosmic ray muon spectrum for momenta up to 2.5 TeV/c ...has been obtained by correcting for the overburden of 320 meter water equivalent (mwe). The results are compared with Monte Carlo models for air shower development in the atmosphere. From the analysis of the spectrum the total flux and the spectral index of the cosmic ray primaries is inferred. The charge ratio suggests a dominantly light composition of cosmic ray primaries with energies up to 10^15 eV.
The software alignment of planar tracking detectors using samples of charged particle trajectories may lead to global detector distortions that affect vertex and momentum resolution. We present an ...alignment procedure that constrains such distortions by making use of samples of decay vertices reconstructed from two or more trajectories and putting constraints on their invariant mass. We illustrate the method by using a sample of invariant-mass constrained vertices from D^0 --> K^- pi^+ decays to remove a curvature bias in the LHCb spectrometer.
The European Physical Journal C, Volume 73, Issue 11, 2013 An angular analysis of the decay $J/\psi \rightarrow \mu^{+} \mu^{-}$ is
performed to measure the polarization of prompt $J/\psi$ mesons ...produced in
$pp$ collisions at $\sqrt{s}=7\; \mathrm{TeV}$. The dataset corresponds to an
integrated luminosity of 0.37 fb$^{-1}$ collected with the LHCb detector. The
measurement is presented as a function of transverse momentum, $p_\mathrm{T}$,
and rapidity, $y$, of the $J/\psi$ meson, in the kinematic region $2 <
p_\mathrm{T} < 15\; \mathrm{GeV}/c$ and $2.0<y<4.5$.
