1,164 research outputs found
Overview of the CKM Matrix
The current status of the determination of the elements of the
Cabibbo-Kobayashi-Maskawa quark-mixing matrix is reviewed. Tensions in the
global fits are highlighted. Particular attention is paid to progress in, and
prospects for, measurements of CP violation effects.Comment: Proceedings of the Lepton Photon 2011 Conference, to appear in
"Pramana - journal of physics", 17 pages, 13 figure
Quantum-fluid dynamics of microcavity polaritons
Semiconductor microcavities offer a unique system to investigate the physics
of weakly interacting bosons. Their elementary excitations, polaritons--a
mixture of excitons and photons--behave, in the low density limit, as bosons
that can undergo a phase transition to a regime characterised by long range
coherence. Condensates of polaritons have been advocated as candidates for
superfluidity; and the formation of vortices as well as elementary excitations
with a linear dispersion are actively sought after. In this work, we have
created and set in motion a macroscopically degenerate state of polaritons and
let it collide with a variety of defects present in the sample. Our experiments
show striking manifestations of a coherent light-matter packet that displays
features of a superfluid, although one of a highly unusual character as it
involves an out-of-equilibrium dissipative system where it travels at
ultra-fast velocity of the order of 1% the speed of light. Our main results are
the observation of i) a linear polariton dispersion accompanied with
diffusion-less motion, ii) flow without resistance when crossing an obstacle,
iii) suppression of Rayleigh scattering and iv) splitting into two fluids when
the size of the obstacle is comparable with the size of the wavepacket. This
work opens the way to the investigation of new phenomenology of
out-of-equilibrium condensates.Comment: 22 pages, 5 figure
and coupling constants in QCD sum rules
The coupling constants and
are calculated in the framework of
three-point QCD sum rules. The correlation functions responsible for these
coupling constants are evaluated considering contributions of both and
mesons as off-shell states, but in the absence of radiative
corrections. The results, and are
obtained for the considered strong coupling constants.Comment: 13 Pages and 11 Figure
Two-loop Corrections to the B to pi Form Factor from QCD Sum Rules on the Light-Cone and |V(ub)|
We calculate the leading-twist O(alphas^2 beta0) corrections to the B to pi
transition form factor f+(0) in light-cone sum rules. We find that, as
expected, there is a cancellation between the O(alphas^2 beta0) corrections to
fB f+(0) and the large corresponding corrections to fB, calculated in QCD sum
rules. This suggests the insensitivity of the form factors calculated in the
light-cone sum rules approach to this source of radiative corrections. We
further obtain an improved determination of the CKM matrix element |V(ub)|,
using latest results from BaBar and Belle for f+(0)|V(ub)|.Comment: 18 pages, 3 figure
The UTfit Collaboration Average of D meson mixing data: Spring 2012
We derive constraints on the parameters , and
that describe meson mixing using all available data, allowing
for CP violation. We also provide posterior distributions and predictions for
observable parameters appearing in physics.Comment: 5 pages, 3 figure
Interpreting Reactor Antineutrino Anomalies with STEREO data
Anomalies in past neutrino measurements have led to the discovery that these
particles have non-zero mass and oscillate between their three flavors when
they propagate. In the 2010's, similar anomalies observed in the antineutrino
spectra emitted by nuclear reactors have triggered the hypothesis of the
existence of a supplementary neutrino state that would be sterile i.e. not
interacting via the weak interaction. The STEREO experiment was designed to
study this scientific case that would potentially extend the Standard Model of
Particle Physics. Here we present a complete study based on our full set of
data with significantly improved sensitivity. Installed at the ILL (Institut
Laue Langevin) research reactor, STEREO has accurately measured the
antineutrino energy spectrum associated to the fission of 235U. This
measurement confirms the anomalies whereas, thanks to the segmentation of the
STEREO detector and its very short mean distance to the core (10~m), the same
data reject the hypothesis of a light sterile neutrino. Such a direct
measurement of the antineutrino energy spectrum suggests instead that biases in
the nuclear experimental data used for the predictions are at the origin of the
anomalies. Our result supports the neutrino content of the Standard Model and
establishes a new reference for the 235U antineutrino energy spectrum. We
anticipate that this result will allow to progress towards finer tests of the
fundamental properties of neutrinos but also to benchmark models and nuclear
data of interest for reactor physics and for observations of astrophysical or
geo-neutrinos.Comment: 21 pages, 13 figure
Improved FIFRELIN de-excitation model for neutrino applications
The precise modeling of the de-excitation of Gd isotopes is of great interest
for experimental studies of neutrinos using Gd-loaded organic liquid
scintillators. The FIFRELIN code was recently used within the purposes of the
STEREO experiment for the modeling of the Gd de-excitation after neutron
capture in order to achieve a good control of the detection efficiency. In this
work, we report on the recent additions in the FIFRELIN de-excitation model
with the purpose of enhancing further the de-excitation description.
Experimental transition intensities from EGAF database are now included in the
FIFRELIN cascades, in order to improve the description of the higher energy
part of the spectrum. Furthermore, the angular correlations between {\gamma}
rays are now implemented in FIFRELIN, to account for the relative anisotropies
between them. In addition, conversion electrons are now treated more precisely
in the whole spectrum range, while the subsequent emission of X rays is also
accounted for. The impact of the aforementioned improvements in FIFRELIN is
tested by simulating neutron captures in various positions inside the STEREO
detector. A repository of up-to-date FIFRELIN simulations of the Gd isotopes is
made available for the community, with the possibility of expanding for other
isotopes which can be suitable for different applications.Comment: Corrected typos on author names on arXiv metadat
CD4 cell count and the risk of AIDS or death in HIV-Infected adults on combination antiretroviral therapy with a suppressed viral load: a longitudinal cohort study from COHERE.
BACKGROUND: Most adults infected with HIV achieve viral suppression within a year of starting combination antiretroviral therapy (cART). It is important to understand the risk of AIDS events or death for patients with a suppressed viral load.
METHODS AND FINDINGS: Using data from the Collaboration of Observational HIV Epidemiological Research Europe (2010 merger), we assessed the risk of a new AIDS-defining event or death in successfully treated patients. We accumulated episodes of viral suppression for each patient while on cART, each episode beginning with the second of two consecutive plasma viral load measurements 500 copies/µl, the first of two consecutive measurements between 50-500 copies/µl, cART interruption or administrative censoring. We used stratified multivariate Cox models to estimate the association between time updated CD4 cell count and a new AIDS event or death or death alone. 75,336 patients contributed 104,265 suppression episodes and were suppressed while on cART for a median 2.7 years. The mortality rate was 4.8 per 1,000 years of viral suppression. A higher CD4 cell count was always associated with a reduced risk of a new AIDS event or death; with a hazard ratio per 100 cells/µl (95% CI) of: 0.35 (0.30-0.40) for counts <200 cells/µl, 0.81 (0.71-0.92) for counts 200 to <350 cells/µl, 0.74 (0.66-0.83) for counts 350 to <500 cells/µl, and 0.96 (0.92-0.99) for counts ≥500 cells/µl. A higher CD4 cell count became even more beneficial over time for patients with CD4 cell counts <200 cells/µl.
CONCLUSIONS: Despite the low mortality rate, the risk of a new AIDS event or death follows a CD4 cell count gradient in patients with viral suppression. A higher CD4 cell count was associated with the greatest benefit for patients with a CD4 cell count <200 cells/µl but still some slight benefit for those with a CD4 cell count ≥500 cells/µl
Analysis of gender equality competence present in cultural positions
Articulating the gender dimension in organizations is not easy because their members have to be trained to adopt positions that facilitate the implementation of solutions that help to combat inequalities. The aim of this article was to identify the gender equality competence present in the three types of cultural positions Castells proposed in members of a City Council in Sevilla-Spain, who wanted to implement gender mainstreaming. The participants were 27 people (16 women and 11 men). The method used was discourse analysis. The obtained results show that, while all competences were present in the project position, in the resistance position, there was none. In the legitimizers, we observed inconsistency in the discourse presented. This arouses considerations on the importance of knowing the gender equality competences in order to implement gender mainstreaming in organization
Evidence for the η_b(1S) Meson in Radiative Υ(2S) Decay
We have performed a search for the η_b(1S) meson in the radiative decay of the Υ(2S) resonance using a sample of 91.6 × 10^6 Υ(2S) events recorded with the BABAR detector at the PEP-II B factory at the SLAC National Accelerator Laboratory. We observe a peak in the photon energy spectrum at E_γ = 609.3^(+4.6)_(-4.5)(stat)±1.9(syst) MeV, corresponding to an η_b(1S) mass of 9394.2^(+4.8)_(-4.9)(stat) ± 2.0(syst) MeV/c^2. The branching fraction for the decay Υ(2S) → γη_b(1S) is determined to be [3.9 ± 1.1(stat)^(+1.1)_(-0.9)(syst)] × 10^(-4). We find the ratio of branching fractions B[Υ(2S) → γη_b(1S)]/B[Υ(3S) → γη_b(1S)]= 0.82 ± 0.24(stat)^(+0.20)_(-0.19)(syst)
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