1,664 research outputs found
A model-independent confirmation of the state
The decay is analyzed using of
collision data collected with the LHCb detector. A model-independent
description of the mass spectrum is obtained, using as input the
mass spectrum and angular distribution derived directly from data,
without requiring a theoretical description of resonance shapes or their
interference. The hypothesis that the mass spectrum can be
described in terms of reflections alone is rejected with more than
8 significance. This provides confirmation, in a model-independent way,
of the need for an additional resonant component in the mass region of the
exotic state.Comment: All figures and tables, along with any supplementary material and
additional information, are available at
https://lhcbproject.web.cern.ch/lhcbproject/Publications/LHCbProjectPublic/LHCb-PAPER-2015-038.htm
Q^2 Dependence of the azimuthal Asymmetry in Unpolarized Drell-Yan
We study the azimuthal asymmetry of the unpolarized Drell-Yan in the
framework of the T-odd functions. We find, on the basis of quite general
arguments, that for |{\bf q}_{\perp}| << Q such an asymmetry decreases as
Q^{-2}, where {\bf q}_{\perp} and Q are respectively the transverse momentum
and the center-of-mass energy of the muon pair. The experimental results
support this conclusion.Comment: 15 pages, 4 figures. Presented at "HiX2004", Marseille, July 26-28,
200
Inclusive Λ_c^+ production in e^+e^- annihilations at √s=10.54 GeV and in Υ(4S) decays
We present measurements of the total production rates and momentum distributions of the charmed baryon Λ_c^+ in e^+e^-→hadrons at a center-of-mass energy of 10.54 GeV and in Υ(4S) decays. In hadronic events at 10.54 GeV, charmed hadrons are almost exclusively leading particles in e^+e^-→cc[overbar] events, allowing direct studies of c-quark fragmentation. We measure a momentum distribution for Λ_c^+ baryons that differs significantly from those measured previously for charmed mesons. Comparing with a number of models, we find none that can describe the distribution completely. We measure an average scaled momentum of =0.574±0.009 and a total rate of N_(Λc)^(qq[overbar]) =0.057±0.002(exp)±0.015(BF) Λ_c^+ per hadronic event, where the experimental error is much smaller than that due to the branching fraction into the reconstructed decay mode, pK^-π^+. In Υ(4S) decays we measure a total rate of N_(Λc)^Υ=0.091±0.006(exp)±0.024(BF) per Υ(4S) decay, and find a much softer momentum distribution than expected from B decays into a Λ_c^+ plus an antinucleon and one to three pions
Branching fraction measurements of the color-suppressed decays B̅^0 to D^((*)0_π^(0), D^((*)0)η, D^((*)0)ω, and D^((*)0)η′ and measurement of the polarization in the decay B̅ 0→D^(*0)ω
We report updated branching fraction measurements of the color-suppressed decays B̅ ^(0) → D^(0)π^(0), D^(*0)π^(0), D^(0)η, D^(*0)η, D^(0)ω, D^(*0)ω, D^(0)η′, and D^(*0)η′. We measure the branching fractions (×10^(-4)): B(B̅^0 → D^(0)π^(0)) = 2.69±0.09±0.13, B(B̅^(0) → D^(*0)π^(0)) = 3.05±0.14±0.28, B(B̅^(0) → D^(0)η) = 2.53±0.09±0.11, B(B̅^(0) → D^(*0)η) = 2.69±0.14±0.23, B(B̅^(0) → D^(0)ω) = 2.57±0.11±0.14, B(B̅^(0) → D^(*0)ω) = 4.55±0.24±0.39, B(B̅^(0)→D^(0)η′) = 1.48±0.13±0.07, and B(B̅^(0) → D^(*0)n′) = 1.49±0.22±0.15. We also present the first measurement of the longitudinal polarization fraction of the decay channel D*0ω, fL=(66.5±4.7±1.5)%. In the above, the first uncertainty is statistical and the second is systematic. The results are based on a sample of (454±5)×10^6 BB̅ pairs collected at the Υ(4S) resonance, with the BABAR detector at the PEP-II storage rings at SLAC. The measurements are the most precise determinations of these quantities from a single experiment. They are compared to theoretical predictions obtained by factorization, Soft Collinear Effective Theory (SCET) and perturbative QCD (pQCD). We find that the presence of final state interactions is favored and the measurements are in better agreement with SCET than with pQCD
f(R) Gravity with Torsion: The Metric-Affine Approach
The role of torsion in f(R) gravity is considered in the framework of
metric-affine formalism. We discuss the field equations in empty space and in
presence of perfect fluid matter taking into account the analogy with the
Palatini formalism. As a result, the extra curvature and torsion degrees of
freedom can be dealt as an effective scalar field of fully geometric origin.
From a cosmological point of view, such a geometric description could account
for the whole Dark Side of the Universe.Comment: 12 page
The Cauchy problem for f(R)-gravity: an overview
We review the Cauchy problem for f(R) theories of gravity, in metric and
metric-affine for- mulations, pointing out analogies and differences with
respect to General Relativity. The role of conformal transformations, effective
scalar fields and sources in the field equations is discussed in view of the
well-posedness of the problem. Finally, criteria of viability of the
f(R)-models are considered according to the various matter fields acting as
sources.Comment: 14 page
Elementary quotient completion
We extend the notion of exact completion on a weakly lex category to
elementary doctrines. We show how any such doctrine admits an elementary
quotient completion, which freely adds effective quotients and extensional
equality. We note that the elementary quotient completion can be obtained as
the composite of two free constructions: one adds effective quotients, and the
other forces extensionality of maps. We also prove that each construction
preserves comprehensions
Muon and Cosmogenic Neutron Detection in Borexino
Borexino, a liquid scintillator detector at LNGS, is designed for the
detection of neutrinos and antineutrinos from the Sun, supernovae, nuclear
reactors, and the Earth. The feeble nature of these signals requires a strong
suppression of backgrounds below a few MeV. Very low intrinsic radiogenic
contamination of all detector components needs to be accompanied by the
efficient identification of muons and of muon-induced backgrounds. Muons
produce unstable nuclei by spallation processes along their trajectory through
the detector whose decays can mimic the expected signals; for isotopes with
half-lives longer than a few seconds, the dead time induced by a muon-related
veto becomes unacceptably long, unless its application can be restricted to a
sub-volume along the muon track. Consequently, not only the identification of
muons with very high efficiency but also a precise reconstruction of their
tracks is of primary importance for the physics program of the experiment. The
Borexino inner detector is surrounded by an outer water-Cherenkov detector that
plays a fundamental role in accomplishing this task. The detector design
principles and their implementation are described. The strategies adopted to
identify muons are reviewed and their efficiency is evaluated. The overall muon
veto efficiency is found to be 99.992% or better. Ad-hoc track reconstruction
algorithms developed are presented. Their performance is tested against muon
events of known direction such as those from the CNGS neutrino beam, test
tracks available from a dedicated External Muon Tracker and cosmic muons whose
angular distribution reflects the local overburden profile. The achieved
angular resolution is 3-5 deg and the lateral resolution is 35-50 cm, depending
on the impact parameter of the crossing muon. The methods implemented to
efficiently tag cosmogenic neutrons are also presented.Comment: 42 pages. 32 figures on 37 files. Uses JINST.cls. 1 auxiliary file
(defines.tex) with TEX macros. submitted to Journal of Instrumentatio
Direct measurement of non-linear properties of bipartite quantum states
Non-linear properties of quantum states, such as entropy or entanglement,
quantify important physical resources and are frequently used in quantum
information science. They are usually calculated from a full description of a
quantum state, even though they depend only on a small number parameters that
specify the state. Here we extract a non-local and a non-linear quantity,
namely the Renyi entropy, from local measurements on two pairs of polarization
entangled photons. We also introduce a "phase marking" technique which allows
to select uncorrupted outcomes even with non-deterministic sources of entangled
photons. We use our experimental data to demonstrate the violation of entropic
inequalities. They are examples of a non-linear entanglement witnesses and
their power exceeds all linear tests for quantum entanglement based on all
possible Bell-CHSH inequalities.Comment: To appear on PRL with minor change
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