1,937 research outputs found
Further studies of GEM performance in dense noble gases
We further study the performance of single, double and triple Gas Electron
Multiplier (GEM) detectors in pure noble gases at high pressures, in the range
of 1-10 atm. We confirm that light noble gases, in particular He and its
mixtures with Kr, have the highest gain, reaching 10^6, and an unusual gain
dependence on pressure. Effects of the number of GEMs, GEM hole diameter and
pitch are investigated in detail. In He, avalanche-induced secondary
scintillations are observed at high gains, using the metal photocathode. These
results are relevant in the field of avalanche mechanism in noble gases and
X-ray, neutron and cryogenic particle detectors.Comment: 4 pages, 4 figures. Presented at the 6th Int. Conf. on Position
Sensitive Detectors, Leicester, Sept 9-13, 200
Weak ferromagnetism of quasi-one-dimensional S=1/2 antiferromagnet BaCuGeO
Weak ferromagnetism of quasi-one-dimensional S = 1/2 antiferromagnet
BaCuGeO is studied by the magnetization measurement. The
spontaneous magnetization appears along the b axis. The local symmetry between
the in-chain nearest neighbor spins allows the presence of
Dzyaloshinskii-Moriya interaction, and the only possible spatial configuration
of the weak ferromagnetic moment per spin determines the sign of the
inter-chain interaction. A weak -axis magnetic field can change the
direction of the magnetization to the -axis direction, which shows that the
spin chain forms a weakly coupled weak-ferromagnetic chain system.Comment: 10 pages, 4 figure
Measurement of the branching fraction of at KEDR
We present the study of the decay . The results
are based on of 5.2 million events collected by the KEDR detector at
VEPP-4M collider. The branching fraction is measured to be
where the first uncertainty is statistical, the second one
is systematic. This is the most precise single measurement of this quantity at
the moment
Differential branching fraction and angular analysis of the decay B0→K∗0μ+μ−
The angular distribution and differential branching fraction of the decay B 0→ K ∗0 μ + μ − are studied using a data sample, collected by the LHCb experiment in pp collisions at s√=7 TeV, corresponding to an integrated luminosity of 1.0 fb−1. Several angular observables are measured in bins of the dimuon invariant mass squared, q 2. A first measurement of the zero-crossing point of the forward-backward asymmetry of the dimuon system is also presented. The zero-crossing point is measured to be q20=4.9±0.9GeV2/c4 , where the uncertainty is the sum of statistical and systematic uncertainties. The results are consistent with the Standard Model predictions
Measurement of the relative rate of prompt χc0, χc1 and χc2 production at √s=7TeV
Prompt production of charmonium χc0, χc1 and χc2 mesons is studied using proton-proton collisions at the LHC at a centre-of-mass energy of √s=7TeV. The χc mesons are identified through their decay to J/ψγ, with J/ψ→μ+mu− using photons that converted in the detector. A data sample, corresponding to an integrated luminosity of 1.0fb−1 collected by the LHCb detector, is used to measure the relative prompt production rate of χc1 and χc2 in the rapidity range 2.0<y<4.5 as a function of the J/ψ transverse momentum from 3 to 20 GeV/c. First evidence for χc0 meson production at a hadron collider is also presented
Measurement of the mass and lifetime of the baryon
A proton-proton collision data sample, corresponding to an integrated
luminosity of 3 fb collected by LHCb at and 8 TeV, is used
to reconstruct , decays. Using the , decay mode for calibration, the lifetime ratio and absolute
lifetime of the baryon are measured to be \begin{align*}
\frac{\tau_{\Omega_b^-}}{\tau_{\Xi_b^-}} &= 1.11\pm0.16\pm0.03, \\
\tau_{\Omega_b^-} &= 1.78\pm0.26\pm0.05\pm0.06~{\rm ps}, \end{align*} where the
uncertainties are statistical, systematic and from the calibration mode (for
only). A measurement is also made of the mass difference,
, and the corresponding mass, which
yields \begin{align*} m_{\Omega_b^-}-m_{\Xi_b^-} &= 247.4\pm3.2\pm0.5~{\rm
MeV}/c^2, \\ m_{\Omega_b^-} &= 6045.1\pm3.2\pm 0.5\pm0.6~{\rm MeV}/c^2.
\end{align*} These results are consistent with previous measurements.Comment: 11 pages, 5 figures, All figures and tables, along with any
supplementary material and additional information, are available at
https://lhcbproject.web.cern.ch/lhcbproject/Publications/LHCbProjectPublic/LHCb-PAPER-2016-008.htm
Measurements of the branching fractions of B+→ppK+ decays
The branching fractions of the decay B+ → pp̄K+ for different intermediate states are measured using data, corresponding to an integrated luminosity of 1.0 fb-1, collected by the LHCb experiment. The total branching fraction, its charmless component Mpp̄ < 2.85 GeV/c2 and the branching fractions via the resonant cc̄ states η c(1S) and ψ(2S) relative to the decay via a J/ψ intermediate state are [Equation not available: see fulltext.] Upper limits on the B + branching fractions into the η c(2S) meson and into the charmonium-like states X(3872) and X(3915) are also obtained
Measurement of the lifetime
Using a data set corresponding to an integrated luminosity of ,
collected by the LHCb experiment in collisions at centre-of-mass energies
of 7 and 8 TeV, the effective lifetime in the
decay mode, , is measured to be ps. Assuming
conservation, corresponds to the lifetime of the light
mass eigenstate. This is the first measurement of the effective
lifetime in this decay mode.Comment: All figures and tables, along with any supplementary material and
additional information, are available at
https://lhcbproject.web.cern.ch/lhcbproject/Publications/LHCbProjectPublic/LHCb-PAPER-2016-017.htm
Search for the decay Bs0→D*∓π±
A search for the decay Bs0→D*∓π± is presented using a data sample corresponding to an integrated luminosity of 1.0 fb-1 of pp collisions collected by LHCb. This decay is expected to be mediated by a W-exchange diagram, with little contribution from rescattering processes, and therefore a measurement of the branching fraction will help us to understand the mechanism behind related decays such as Bs0→π+π- and Bs0→DD- . Systematic uncertainties are minimized by using B0→D*∓π± as a normalization channel. We find no evidence for a signal, and set an upper limit on the branching fraction of B(Bs0→D*∓π±)<6.1(7.8)×10-6 at 90% (95%) confidence level
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