39 research outputs found
A meta-analysis of perceptions of defeat and entrapment in depression, anxiety problems, posttraumatic stress disorder, and suicidality
This document is the Accepted Manuscript version of the following article: Andy P. Siddaway, Peter J. Taylor, Alex M. Wood, and Joerg Schulz, ‘A meta-analysis of perceptions of defeat and entrapment in depression, anxiety problems, posttraumatic stress disorder, and suicidality’, Journal of Affective Disorders, Vol. 184: 149-159, September 2015. The final, published version is available online at: DOI: https://doi.org/10.1016/j.jad.2015.05.046Background: There is a burgeoning literature examining perceptions of being defeated or trapped in different psychiatric disorders. The disorders most frequently examined to date are depression, anxiety problems, posttraumatic stress disorder (PTSD), and suicidality. Aims: To quantify the size and consistency of perceptions of defeat and entrapment in depression, anxiety problems, PTSD and suicidality, test for differences across psychiatric disorders, and examine potential moderators and publication bias. Method:Random-effects meta-analyses based on Pearson's correlation coefficient r. Results: Forty studies were included in the meta-analysis (n=10,072). Perceptions of defeat and entrapment were strong (around r=0.60) and similar in size across all four psychiatric disorders. Perceptions of defeat were particularly strong in depression (r=0.73). There was no between-study heterogeneity; therefore moderator analyses were conducted in an exploratory fashion. There was no evidence of publication bias. Limitations: Analyses were cross-sectional, which precludes establishing temporal precedence or causality. Some of the meta-analyses were based on relatively small numbers of effect sizes, which may limit their generalisability. Conclusions: Perceptions of defeat and entrapment are clinically important in depression, anxiety problems, PTSD, and suicidality. Similar-sized, strong relationships across four different psychiatric disorders could suggest that perceptions of defeat and entrapment are transdiagnostic constructs. The results suggest that clinicians and researchers need to become more aware of perceptions of defeat and entrapmentPeer reviewedFinal Accepted Versio
The Spin Structure Function of the Proton and a Test of the Bjorken Sum Rule
New results for the double spin asymmetry and the proton
longitudinal spin structure function are presented. They were
obtained by the COMPASS collaboration using polarised 200 GeV muons scattered
off a longitudinally polarised NH target. The data were collected in 2011
and complement those recorded in 2007 at 160\,GeV, in particular at lower
values of . They improve the statistical precision of by
about a factor of two in the region . A next-to-leading order
QCD fit to the world data is performed. It leads to a new determination
of the quark spin contribution to the nucleon spin, ranging
from 0.26 to 0.36, and to a re-evaluation of the first moment of .
The uncertainty of is mostly due to the large uncertainty in
the present determinations of the gluon helicity distribution. A new evaluation
of the Bjorken sum rule based on the COMPASS results for the non-singlet
structure function yields as ratio of the axial and
vector coupling constants , which validates the sum rule to an accuracy of about
9\%.Comment: 19 pages, 8 figures and table
Measurement of the charged-pion polarisability
The COMPASS collaboration at CERN has investigated pion Compton scattering,
, at centre-of-mass energy below 3.5 pion
masses. The process is embedded in the reaction
, which is initiated by
190\,GeV pions impinging on a nickel target. The exchange of quasi-real photons
is selected by isolating the sharp Coulomb peak observed at smallest momentum
transfers, \,(GeV/). From a sample of 63\,000 events the
pion electric polarisability is determined to be $\alpha_\pi\ =\ (\,2.0\ \pm\
0.6_{\mbox{\scriptsize stat}}\ \pm\ 0.7_{\mbox{\scriptsize syst}}\,) \times
10^{-4}\,\mbox{fm}^3\alpha_\pi=-\beta_\pi$, which
relates the electric and magnetic dipole polarisabilities. It is the most
precise measurement of this fundamental low-energy parameter of strong
interaction, that has been addressed since long by various methods with
conflicting outcomes. While this result is in tension with previous dedicated
measurements, it is found in agreement with the expectation from chiral
perturbation theory. An additional measurement replacing pions by muons, for
which the cross-section behavior is unambigiously known, was performed for an
independent estimate of the systematic uncertainty.Comment: Published version: 9 pages, 3 figures, 1 tabl
Collins and Sivers asymmetries in muonproduction of pions and kaons off transversely polarised proton
Measurements of the Collins and Sivers asymmetries for charged pions and
charged and neutral kaons produced in semi-inclusive deep-inelastic scattering
of high energy muons off transversely polarised protons are presented. The
results were obtained using all the available COMPASS proton data, which were
taken in the years 2007 and 2010. The Collins asymmetries exhibit in the
valence region a non-zero signal for pions and there are hints of non-zero
signal also for kaons. The Sivers asymmetries are found to be positive for
positive pions and kaons and compatible with zero otherwise.Comment: 15 pages, 13 figures and 1 tabl
Spin alignment and violation of the OZI rule in exclusive and production in pp collisions
Exclusive production of the isoscalar vector mesons and is
measured with a 190 GeV proton beam impinging on a liquid hydrogen target.
Cross section ratios are determined in three intervals of the Feynman variable
of the fast proton. A significant violation of the OZI rule is found,
confirming earlier findings. Its kinematic dependence on and on the
invariant mass of the system formed by fast proton
and vector meson is discussed in terms of diffractive
production of resonances in competition with central
production. The measurement of the spin density matrix element of
the vector mesons in different selected reference frames provides another
handle to distinguish the contributions of these two major reaction types.
Again, dependences of the alignment on and on are
found. Most of the observations can be traced back to the existence of several
excited baryon states contributing to production which are absent in
the case of the meson. Removing the low-mass resonant
region, the OZI rule is found to be violated by a factor of eight,
independently of .Comment: 23 pages, 13 figures and 5 table
Search for exclusive photoproduction of Z(3900) at COMPASS
A search for the exclusive production of the hadron by
virtual photons has been performed in the channel . The data cover the range from 7 GeV to 19 GeV in the
centre-of-mass energy of the photon-nucleon system. The full set of the COMPASS
data set collected with a muon beam between 2002 and 2011 has been used. An
upper limit for the ratio of has been established at the confidence
level of 90%.Comment: 8 pages, 3 figures, 1 tabl
Transverse-momentum-dependent Multiplicities of Charged Hadrons in Muon-Deuteron Deep Inelastic Scattering
A semi-inclusive measurement of charged hadron multiplicities in deep
inelastic muon scattering off an isoscalar target was performed using data
collected by the COMPASS Collaboration at CERN. The following kinematic domain
is covered by the data: photon virtuality (GeV/), invariant
mass of the hadronic system GeV/, Bjorken scaling variable in the
range , fraction of the virtual photon energy carried by the
hadron in the range , square of the hadron transverse momentum
with respect to the virtual photon direction in the range 0.02 (GeV/ (GeV/). The multiplicities are presented as a
function of in three-dimensional bins of , , and
compared to previous semi-inclusive measurements. We explore the
small- region, i.e. (GeV/), where
hadron transverse momenta are expected to arise from non-perturbative effects,
and also the domain of larger , where contributions from
higher-order perturbative QCD are expected to dominate. The multiplicities are
fitted using a single-exponential function at small to study
the dependence of the average transverse momentum on , and . The power-law behaviour of the
multiplicities at large is investigated using various
functional forms. The fits describe the data reasonably well over the full
measured range.Comment: 28 pages, 20 figure
The COMPASS Setup for Physics with Hadron Beams
The main characteristics of the COMPASS experimental setup for physics with
hadron beams are described. This setup was designed to perform exclusive
measurements of processes with several charged and/or neutral particles in the
final state. Making use of a large part of the apparatus that was previously
built for spin structure studies with a muon beam, it also features a new
target system as well as new or upgraded detectors. The hadron setup is able to
operate at the high incident hadron flux available at CERN. It is characterised
by large angular and momentum coverages, large and nearly flat acceptances, and
good two and three-particle mass resolutions. In 2008 and 2009 it was
successfully used with positive and negative hadron beams and with liquid
hydrogen and solid nuclear targets. This article describes the new and upgraded
detectors and auxiliary equipment, outlines the reconstruction procedures used,
and summarises the general performance of the setup.Comment: 91 pages, 101 figures and 7 table
Longitudinal double-spin asymmetry A1pand spin-dependent structure function g1pof the proton at small values of x and Q2
We present a precise measurement of the proton longitudinal double-spin asymmetry Ap1 and the proton spin-dependent structure function gp 1 at photon virtualities 0.006 (GeV/c)2 < Q 2 < 1 (GeV/c)2 in the Bjorken x range of 4
7 10 125 < x < 4
7 10 122. The results are based on data collected by the COMPASS Collaboration at CERN using muon beam energies of 160 GeV and 200 GeV. The statistical precision is more than tenfold better than that of the previous measurement in this region. In the whole range of x, the measured values of Ap1 and gp1 are found to be positive. It is for the first time that spin effects are found at such low values of