1,134 research outputs found
Measurement of the B0-anti-B0-Oscillation Frequency with Inclusive Dilepton Events
The - oscillation frequency has been measured with a sample of
23 million \B\bar B pairs collected with the BABAR detector at the PEP-II
asymmetric B Factory at SLAC. In this sample, we select events in which both B
mesons decay semileptonically and use the charge of the leptons to identify the
flavor of each B meson. A simultaneous fit to the decay time difference
distributions for opposite- and same-sign dilepton events gives ps.Comment: 7 pages, 1 figure, submitted to Physical Review Letter
Improved Limits on decays to invisible final states
We establish improved upper limits on branching fractions for B0 decays to
final States 10 where the decay products are purely invisible (i.e., no
observable final state particles) and for final states where the only visible
product is a photon. Within the Standard Model, these decays have branching
fractions that are below the current experimental sensitivity, but various
models of physics beyond the Standard Model predict significant contributions
for these channels. Using 471 million BB pairs collected at the Y(4S) resonance
by the BABAR experiment at the PEP-II e+e- storage ring at the SLAC National
Accelerator Laboratory, we establish upper limits at the 90% confidence level
of 2.4x10^-5 for the branching fraction of B0-->Invisible and 1.7x10^-5 for the
branching fraction of B0-->Invisible+gammaComment: 8 pages, 3 postscript figures, submitted to Phys. Rev. D (Rapid
Communications
Neutron spin resonance as a probe of superconducting gap anisotropy in partially detwinned electron underdoped NaFeCoAs
We use inelastic neutron scattering (INS) to study the spin excitations in
partially detwinned NaFeCoAs which has coexisting static
antiferromagnetic (AF) order and superconductivity ( K, K). In
previous INS work on a twinned sample, spin excitations form a dispersive sharp
resonance near meV and a broad dispersionless mode at
meV at the AF ordering wave vector and its
twinned domain . For partially detwinned
NaFeCoAs with the static AF order mostly occurring at , we still find a double resonance at both wave vectors with
similar intensity. Since characterizes the explicit breaking
of the spin rotational symmetry associated with the AF order, these results
indicate that the double resonance cannot be due to the static and fluctuating
AF orders, but originate from the superconducting gap anisotropy.Comment: 5 pages, 5 figures; PRB, 2015 (the correct final version is now used
Exclusive Measurements of b -> s gamma Transition Rate and Photon Energy Spectrum
We use 429 fb of collision data collected at the
resonance with the BABAR detector to measure the radiative
transition rate of with a sum of 38 exclusive final
states. The inclusive branching fraction with a minimum photon energy of 1.9
GeV is found to be where the first uncertainty is statistical and the
second is systematic. We also measure the first and second moments of the
photon energy spectrum and extract the best fit values for the heavy-quark
parameters, and , in the kinetic and shape function
models.Comment: 18 pages, 14 pdf figures, submitted to Phys. Rev.
Active Matter Alters the Growth Dynamics of Coffee Rings
How particles are deposited at the edge of evaporating droplets, i.e. the
{\em coffee ring} effect, plays a crucial role in phenomena as diverse as
thin-film deposition, self-assembly, and biofilm formation. Recently,
microorganisms have been shown to passively exploit and alter these deposition
dynamics to increase their survival chances under harshening conditions. Here,
we show that, as the droplet evaporation rate slows down, bacterial mobility
starts playing a major role in determining the growth dynamics of the edge of
drying droplets. Such motility-induced dynamics can influence several
biophysical phenomena, from the formation of biofilms to the spreading of
pathogens in humid environments and on surfaces subject to periodic drying.
Analogous dynamics in other active matter systems can be exploited for
technological applications in printing, coating, and self-assembly, where the
standard coffee-ring effect is often a nuisance.Comment: 7 pages, 5 figure
Progress on development of the new FDIRC PID detector
International audienceWe present a progress status of a new concept of PID detector called FDIRC, intended to be used at the SuperB experiment, which requires π/K separation up to a few GeV/c. The new photon camera is made of the solid fused-silica optics with a volume 25× smaller and speed increased by a factor of 10 compared to the BaBar DIRC, and therefore will be much less sensitive to electromagnetic and neutron background
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