8,093 research outputs found
The Rare Top Decays and
The large value of the top quark mass implies that the rare top decays and , and and
, are kinematically allowed decays so long as or , respectively. The partial decay widths for these decay modes
are calculated in the standard model. The partial widths depend sensitively on
the precise value of the top quark mass. The branching ratio for is as much as for , and could be
observable at LHC. The rare decay modes and are highly GIM-suppressed, and thus provide a means for testing the GIM
mechanism for three generations of quarks in the u, c, t sector.Comment: 19 pages, latex, t->bWZ corrected, previous literature on t->bWZ
cited, t->cWW unchange
Measurement of the Charge Collection Efficiency after Heavy Non-Uniform Irradiation in BaBar Silicon Detectors
We have investigated the depletion voltage changes, the leakage current
increase and the charge collection efficiency of a silicon microstrip detector
identical to those used in the inner layers of the BaBar Silicon Vertex Tracker
(SVT) after heavy non-uniform irradiation. A full SVT module with the front-end
electronics connected has been irradiated with a 0.9 GeV electron beam up to a
peak fluence of 3.5 x 10^14 e^-/cm^2, well beyond the level causing substrate
type inversion. We irradiated one of the two sensors composing the module with
a non-uniform profile with sigma=1.4 mm that simulates the conditions
encountered in the BaBar experiment by the modules intersecting the horizontal
machine plane. The position dependence of the charge collection properties and
the depletion voltage have been investigated in detail using a 1060 nm LED and
an innovative measuring technique based only on the digital output of the chip.Comment: 7 pages, 13 figures. Presented at the 2004 IEEE Nuclear Science
Symposium, October 18-21, Rome, Italy. Accepted for publication by IEEE
Transactions on Nuclear Scienc
Equal-time two-point correlation functions in Coulomb gauge Yang-Mills theory
We apply a functional perturbative approach to the calculation of the
equal-time two-point correlation functions and the potential between static
color charges to one-loop order in Coulomb gauge Yang-Mills theory. The
functional approach proceeds through a solution of the Schroedinger equation
for the vacuum wave functional to order g^2 and derives the equal-time
correlation functions from a functional integral representation via new
diagrammatic rules. We show that the results coincide with those obtained from
the usual Lagrangian functional integral approach, extract the beta function,
and determine the anomalous dimensions of the equal-time gluon and ghost
two-point functions and the static potential under the assumption of
multiplicative renormalizability to all orders.Comment: 33 pages, 7 figures with Feyman diagrams generated with pstricks;
revised version with additional references and comments on possible
applications added in the conclusions; accepted for publication in Nucl.
Phys.
In vitro evaluation of live attenuated vaccines against Salmonella enteritidis: humoral immune response
Salmonella enteritidis (SE) vaccination is one of the major tool to reduce the infection in commercial poultry. In this work, techniques, evaluating the presence of Ig-G and Ig-A in serum, tears and intestinal secretions, were studied to improve the knowledge of the humoral immune response following SE live attenuated vaccination. The Ig-G and Ig-A ELISA are important and easy tests to plan and optimize SE vaccination programs
Boost operators in Coulomb-gauge QCD: the pion form factor and Fock expansions in phi radiative decays
In this article we rederive the Boost operators in Coulomb-Gauge Yang-Mills
theory employing the path-integral formalism and write down the complete
operators for QCD. We immediately apply them to note that what are usually
called the pion square, quartic... charge radii, defined from derivatives of
the pion form factor at zero squared momentum transfer, are completely blurred
out by relativistic and interaction corrections, so that it is not clear at all
how to interpret these quantities in terms of the pion charge distribution. The
form factor therefore measures matrix elements of powers of the QCD boost and
Moeller operators, weighted by the charge density in the target's rest frame.
In addition we remark that the decomposition of the eta' wavefunction in
quarkonium, gluonium, ... components attempted by the KLOE collaboration
combining data from phi radiative decays, requires corrections due to the
velocity of the final state meson recoiling against a photon. This will be
especially important if such decompositions are to be attempted with data from
J/psi decays.Comment: 14 pages, 4 figure
Top-ology
Extended version of an article on top-quark physics, to appear in the May
1997 issue of Physics Today.Comment: 24 pages, 5 figures, LaTeX2e + BoxedEPS
A Study of Time-Dependent CP-Violating Asymmetries and Flavor Oscillations in Neutral B Decays at the Upsilon(4S)
We present a measurement of time-dependent CP-violating asymmetries in
neutral B meson decays collected with the BABAR detector at the PEP-II
asymmetric-energy B Factory at the Stanford Linear Accelerator Center. The data
sample consists of 29.7 recorded at the
resonance and 3.9 off-resonance. One of the neutral B mesons,
which are produced in pairs at the , is fully reconstructed in
the CP decay modes , , , () and , or in flavor-eigenstate
modes involving and (). The flavor of the other neutral B meson is tagged at the time of
its decay, mainly with the charge of identified leptons and kaons. The proper
time elapsed between the decays is determined by measuring the distance between
the decay vertices. A maximum-likelihood fit to this flavor eigenstate sample
finds . The value of the asymmetry amplitude is determined from
a simultaneous maximum-likelihood fit to the time-difference distribution of
the flavor-eigenstate sample and about 642 tagged decays in the
CP-eigenstate modes. We find , demonstrating that CP violation exists in the neutral B meson
system. (abridged)Comment: 58 pages, 35 figures, submitted to Physical Review
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Measurement of B(B-->X_s {\gamma}), the B-->X_s {\gamma} photon energy spectrum, and the direct CP asymmetry in B-->X_{s+d} {\gamma} decays
The photon spectrum in B --> X_s {\gamma} decay, where X_s is any strange
hadronic state, is studied using a data sample of (382.8\pm 4.2) \times 10^6
e^+ e^- --> \Upsilon(4S) --> BBbar events collected by the BABAR experiment at
the PEP-II collider. The spectrum is used to measure the branching fraction B(B
--> X_s \gamma) = (3.21 \pm 0.15 \pm 0.29 \pm 0.08)\times 10^{-4} and the
first, second, and third moments = 2.267 \pm 0.019 \pm 0.032 \pm
0.003 GeV,, )^2> = 0.0484 \pm 0.0053 \pm 0.0077 \pm
0.0005 GeV^2, and )^3> = -0.0048 \pm 0.0011 \pm 0.0011
\pm 0.0004 GeV^3, for the range E_\gamma > 1.8 GeV, where E_{\gamma} is the
photon energy in the B-meson rest frame. Results are also presented for
narrower E_{\gamma} ranges. In addition, the direct CP asymmetry A_{CP}(B -->
X_{s+d} \gamma) is measured to be 0.057 \pm 0.063. The spectrum itself is also
unfolded to the B-meson rest frame; that is the frame in which theoretical
predictions for its shape are made.Comment: 37 pages, 19 postscript figures, submitted to Phys. Rev. D. No
analysis or results have changed from previous version. Some changes to
improve clarity based on interactions with Phys. Rev. D referees, including
one new Figure (Fig. 13), and some minor wording/punctuation/spelling
mistakes fixe
Measurement of ISR-FSR interference in the processes e+ e- --> mu+ mu- gamma and e+ e- --> pi+ pi- gamma
Charge asymmetry in processes e+ e- --> mu+ mu- gamma and e+ e- --> pi+ pi-
gamma is measured using 232 fb-1 of data collected with the BABAR detector at
center-of-mass energies near 10.58 GeV. An observable is introduced and shown
to be very robust against detector asymmetries while keeping a large
sensitivity to the physical charge asymmetry that results from the interference
between initial and final state radiation. The asymmetry is determined as
afunction of the invariant mass of the final-state tracks from production
threshold to a few GeV/c2. It is compared to the expectation from QED for e+ e-
--> mu+ mu- gamma and from theoretical models for e+ e- --> pi+ pi- gamma. A
clear interference pattern is observed in e+ e- --> pi+ pi- gamma, particularly
in the vicinity of the f_2(1270) resonance. The inferred rate of lowest order
FSR production is consistent with the QED expectation for e+ e- --> mu+ mu-
gamma, and is negligibly small for e+ e- --> pi+ pi- gamma.Comment: 32 pages,29 figures, to be submitted to Phys. Rev.
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