66 research outputs found
The global covariance matrix of tracks fitted with a Kalman filter and an application in detector alignment
We present an expression for the covariance matrix for the set of state
vectors describing a track fitted with a Kalman filter. We demonstrate that
this expression facilitates the use of a Kalman filter track model in a minimum
algorithm for the alignment of tracking detectors. We also show that
it allows to incorporate vertex constraints in such a procedure without
refitting the tracks.Comment: 17 pages, 4 figure
Observation of X(3872) production in pp collisions at âs=7TeV
Using 34.7 pbâ1 of data collected with the LHCb
detector, the inclusive production of the X(3872) meson in
pp collisions at âs = 7 TeV is observed for the first time.
Candidates are selected in the X(3872)âJ/ÏÏ+Ïâ decay
mode, and used to measure Ï(ppâX(3872)+anything)B(X(3872)âJ/ÏÏ+Ïâ) = 5.4 ±1.3 (stat)±0.8 (syst) nb, where Ï(pp âX(3872) + anything) is the inclusive production cross section of X(3872) mesons with rapidity in the range 2.5â4.5 and transverse momentum in the range 5â20 GeV/c. In addition the masses of both the X(3872) and Ï(2S) mesons, reconstructed in the J/ÏÏ+Ïâ final state, are measured to be mX(3872) = 3871.95± 0.48 (stat)±0.12 (syst) MeV/c2 and
mÏ(2S) = 3686.12±0.06 (stat) ±0.10 (syst) MeV/c2
A search for the decay
We search for the rare flavor-changing neutral-current decay in a data sample of 82 fb collected with the {\sl BABAR}
detector at the PEP-II B-factory. Signal events are selected by examining the
properties of the system recoiling against either a reconstructed hadronic or
semileptonic charged-B decay. Using these two independent samples we obtain a
combined limit of
at the 90% confidence level. In addition, by selecting for pions rather than
kaons, we obtain a limit of using only the hadronic B reconstruction method.Comment: 7 pages, 8 postscript figures, submitted to Phys. Rev. Let
High-reflectivity broadband distributed Bragg reflector lattice matched to ZnTe
We report on the realization of a high quality distributed Bragg reflector
with both high and low refractive index layers lattice matched to ZnTe. Our
structure is grown by molecular beam epitaxy and is based on binary compounds
only. The high refractive index layer is made of ZnTe, while the low index
material is made of a short period triple superlattice containing MgSe, MgTe,
and ZnTe. The high refractive index step of Delta_n=0.5 in the structure
results in a broad stopband and the reflectivity coefficient exceeding 99% for
only 15 Bragg pairs.Comment: 4 pages, 3 figure
EuFeAs under high pressure: an antiferromagnetic bulk superconductor
We report the ac magnetic susceptibility and resistivity
measurements of EuFeAs under high pressure . By observing nearly
100% superconducting shielding and zero resistivity at = 28 kbar, we
establish that -induced superconductivity occurs at ~30 K in
EuFeAs. shows an anomalous nearly linear temperature dependence
from room temperature down to at the same . indicates that
an antiferromagnetic order of Eu moments with ~20 K persists
in the superconducting phase. The temperature dependence of the upper critical
field is also determined.Comment: To appear in J. Phys. Soc. Jpn., Vol. 78 No.
Improved measurement of CP asymmetries in B-0 ->(c(c)over-bar)K0((*)) decays
We present results on time-dependent CP asymmetries in neutral B decays to several CP eigenstates. The measurements use a data sample of about 227x10(6) Upsilon(4S)-> B (B) over bar decays collected by the BABAR detector at the PEP-II asymmetric-energy B Factory at SLAC. The amplitude of the CPasymmetry, sin2 beta in the standard model, is derived from decay-time distributions from events in which one neutral B meson is fully reconstructed in a final state containing a charmonium meson and the other B meson is determined to be either a B-0 or (0) from its decay products. We measure sin2 beta=0.722 +/- 0.040(stat)+/- 0.023(syst) in agreement with the standard model expectation
Measurement of the electron energy spectrum and its moments in inclusive B -> Xe nu decays
We report a measurement of the inclusive electron energy spectrum for semileptonic decays of B mesons in a data sample of 52 million Y(4S)-->B(B) over bar decays collected with the BABAR detector at the PEP-II asymmetric-energy B-meson factory at SLAC. We determine the branching fraction, first, second, and third moments of the spectrum for lower cutoffs on the electron energy between 0.6 and 1.5 GeV. We measure the partial branching fraction to be B(B-->Xenu,E-e>0.6 GeV)=[10.36+/-0.06(stat.)+/-0.23(sys.)]%
Search for the flavor-changing neutral current decay D0 --> mu+ mu- with the HERA-B detector
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