537 research outputs found
Measurement of the Decay Amplitudes of B0 --> J/psi K* and B0s --> J/psi phi Decays
A full angular analysis has been performed for the pseudo-scalar to
vector-vector decays, B0 --> J/psi K* and B_s --> J/psi phi, to determine the
amplitudes for decays with parity-even longitudinal and transverse polarization
and parity-odd transverse polarization. The measurements are based on 190 B0
candidates and 40 B_s candidates collected from a data set corresponding to 89
inverse pb of pbarp collisions at root(s) = 1.8 TeV at the Fermilab Tevatron.
In both decays the decay amplitude for longitudinal polarization dominates and
the parity-odd amplitude is found to be small.Comment: 7 pages, 3 figures, 1 tabl
Appraisal of MC2010 shear resistance approaches coupled with a residual flexural strength prediction model
In the present work the predictive performance of the two approaches proposed by
Model Code 2010 for the evaluation of the shear capacity of fiber reinforced concrete (FRC)
elements flexurally reinforced with conventional steel bars is assessed considering a database
(DBs) constituted by 80 FRC beams do not including conventional transverse reinforcements.
The accuracy of these shear models is evaluated by statistical analysis of the prediction ratio
between the experimental and estimated shear capacity of the beams of the DBs, and applying
the Demerit Points Classification approach for further information about the reliability of the
two approaches in design context. Due to the absence of the post-cracking experimental
characterization of the FRC used in several beams considered in the DBs, an approach was
developed for estimating the residual flexural strength parameters from the most relevant known
variables of steel fiber reinforcement mechanisms for concrete, namely the fiber volume and
aspect ratio, and the concrete compressive and tensile strength. The residual flexural strength
prediction model is assessed and its influence on the performance of the shear resistance models
is evaluatedSFRH/BDE/96381/2013 co-funded by CiviTest -
Pesquisa de Novos Materiais para a Engenharia Civil, Lda. and by FCT - Portuguese Foundation for
Science and Technology. The authors also acknowledge the support provided by the FCT project PTDC/ECM-EST/2635/201
Measurement of the Ratios of Branching Fractions B(Bs->Ds- pi+)/B(B0->D-pi+) and B(B+->D0bar pi+)/B(B0->D-pi+)
We report an observation of the decay Bs -> Ds- pi+ in p pbar collisions at
sqrt(s) = 1.96 TeV using 115 pb^(-1) of data collected by the CDF II detector
at the Fermilab Tevatron. We observe 83 +/- 11 Bs -> Ds- pi+ candidates,
representing a large increase in statistics over previous measurements and the
first observation of this decay at a p pbar collider. We present the first
measurement of the relative branching fraction B(Bs -> Ds- pi+) / B(B0 -> D-
pi+) = 1.32 +/- 0.18 (stat.) +/- 0.38 (syst.). We also measure B(B+ -> D0bar
pi+) / B(B0 -> D- pi+) = 1.97 +/- 0.10(stat.) +/- 0.21(syst.), which is
consistent with previous measurements
Search for New Physics in Lepton + Photon + X Events with L=305 pb-1 of ppbar Collisions at roots=1.96 TeV
We present results of a search for anomalous production of events containing
a charged lepton (either electron or muon) and a photon, both with high
transverse momentum, accompanied by additional signatures, X, including missing
transverse energy (MET) and additional leptons and photons. We use the same
kinematic selection criteria as in a previous CDF search, but with a
substantially larger data set, 305 pb-1, a ppbar collision energy of 1.96 TeV,
and the upgraded CDF II detector. We find 42 Lepton+Photon+MET events versus a
standard model expectation of 37.3 +- 5.4 events. The level of excess observed
in Run I, 16 events with an expectation of 7.6 +- 0.7 events (corresponding to
a 2.7 sigma effect), is not supported by the new data. In the signature of
Multi-Lepton+Photon+X we observe 31 events versus an expectation of 23.0 +- 2.7
events. In this sample we find no events with an extra photon or MET and so
find no events like the one ee+gg+MET event observed in Run I.Comment: 7 pages, 3 figures, 1 table. Accepted to PR
Measurement of the Lambda_b Lifetime in Lambda_b --> J/psi Lambda0 in p-pbar Collisions at sqrt(s)=1.96 TeV
We report a measurement of the Lambda_b lifetime in the exclusive decay
Lambda_b --> J/psi Lambda0 in p-pbar collisions at sqrt(s) = 1.96 TeV using an
integrated luminosity of 1.0 fb^{-1} of data collected by the CDF II detector
at the Fermilab Tevatron. Using fully reconstructed decays, we measure
tau(Lambda_b) = 1.593 ^{+0.083}_{-0.078} (stat.) +- 0.033 (syst.) ps. This is
the single most precise measurement of tau(Lambda_b) and is 3.2 sigma higher
than the current world average.Comment: 7 Pages, 2 Figures, 1 Table. Submitted to Phys. Rev. Let
Top Quark Mass Measurement from Dilepton Events at CDF II with the Matrix-Element Method
We describe a measurement of the top quark mass using events with two charged
leptons collected by the CDF II detector from collisions with TeV at the Fermilab Tevatron. The likelihood in top mass is
calculated for each event by convoluting the leading order matrix element
describing
with detector resolution functions. The presence of background events in the
data sample is modeled using similar calculations involving the matrix elements
for major background processes. In a data sample with integrated luminosity of
340 pb, we observe 33 candidate events and measure This
measurement represents the first application of this method to events with two
charged leptons and is the most precise single measurement of the top quark
mass in this channel.Comment: 21 pages, 14 figure
Precision measurement of the top quark mass from dilepton events at CDF II
We report a measurement of the top quark mass, M_t, in the dilepton decay
channel of
using an integrated luminosity of 1.0 fb^{-1} of p\bar{p} collisions collected
with the CDF II detector. We apply a method that convolutes a leading-order
matrix element with detector resolution functions to form event-by-event
likelihoods; we have enhanced the leading-order description to describe the
effects of initial-state radiation. The joint likelihood is the product of the
likelihoods from 78 candidate events in this sample, which yields a measurement
of M_{t} = 164.5 \pm 3.9(\textrm{stat.}) \pm 3.9(\textrm{syst.})
\mathrm{GeV}/c^2, the most precise measurement of M_t in the dilepton channel.Comment: 7 pages, 2 figures, version includes changes made prior to
publication by journa
Measurement of the Ratios of Branching Fractions B(Bs -> Ds pi pi pi) / B(Bd -> Dd pi pi pi) and B(Bs -> Ds pi) / B(Bd -> Dd pi)
Using 355 pb^-1 of data collected by the CDF II detector in \ppbar collisions
at sqrt{s} = 1.96 TeV at the Fermilab Tevatron, we study the fully
reconstructed hadronic decays B -> D pi and B -> D pi pi pi. We present the
first measurement of the ratio of branching fractions B(Bs -> Ds pi pi pi) /
B(Bd -> Dd pi pi pi) = 1.05 pm 0.10 (stat) pm 0.22 (syst). We also update our
measurement of B(Bs -> Ds pi) / B(Bd -> Dd pi) to 1.13 pm 0.08 (stat) pm 0.23
(syst) improving the statistical uncertainty by more than a factor of two. We
find B(Bs -> Ds pi) = [3.8 pm 0.3 (stat) pm 1.3 (syst)] \times 10^{-3} and B(Bs
-> Ds pi pi pi) = [8.4 pm 0.8 (stat) pm 3.2 (syst)] \times 10^{-3}.Comment: 7 pages, 2 figure
Cross Section Measurements of High- Dilepton Final-State Processes Using a Global Fitting Method
We present a new method for studying high- dilepton events
(, , ) and simultaneously
extracting the production cross sections of , , and p\bar{p} \to \ztt at a center-of-mass energy of TeV. We perform a likelihood fit to the dilepton data in a parameter
space defined by the missing transverse energy and the number of jets in the
event. Our results, which use of data recorded with the CDF
II detector at the Fermilab Tevatron Collider, are pb, pb, and
\sigma(\ztt) =291^{+50}_{-46} pb.Comment: 20 pages, 2 figures, to be submitted to PRD-R
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