2,167 research outputs found
Bibliometrics of systematic reviews : analysis of citation rates and journal impact factors
Background:
Systematic reviews are important for informing clinical practice and health policy. The aim of this study was to examine the bibliometrics of systematic reviews and to determine the amount of variance in citations predicted by the journal impact factor (JIF) alone and combined with several other characteristics.
Methods:
We conducted a bibliometric analysis of 1,261 systematic reviews published in 2008 and the citations to them in the Scopus database from 2008 to June 2012. Potential predictors of the citation impact of the reviews were examined using descriptive, univariate and multiple regression analysis.
Results:
The mean number of citations per review over four years was 26.5 (SD +/-29.9) or 6.6 citations per review per year. The mean JIF of the journals in which the reviews were published was 4.3 (SD +/-4.2). We found that 17% of the reviews accounted for 50% of the total citations and 1.6% of the reviews were not cited. The number of authors was correlated with the number of citations (r = 0.215, P =5.16) received citations in the bottom quartile (eight or fewer), whereas 9% of reviews published in the lowest JIF quartile (<=2.06) received citations in the top quartile (34 or more). Six percent of reviews in journals with no JIF were also in the first quartile of citations.
Conclusions:
The JIF predicted over half of the variation in citations to the systematic reviews. However, the distribution of citations was markedly skewed. Some reviews in journals with low JIFs were well-cited and others in higher JIF journals received relatively few citations; hence the JIF did not accurately represent the number of citations to individual systematic reviews
Measurement of the diffractive structure function in deep inelastic scattering at HERA
This paper presents an analysis of the inclusive properties of diffractive
deep inelastic scattering events produced in interactions at HERA. The
events are characterised by a rapidity gap between the outgoing proton system
and the remaining hadronic system. Inclusive distributions are presented and
compared with Monte Carlo models for diffractive processes. The data are
consistent with models where the pomeron structure function has a hard and a
soft contribution. The diffractive structure function is measured as a function
of \xpom, the momentum fraction lost by the proton, of , the momentum
fraction of the struck quark with respect to \xpom, and of . The \xpom
dependence is consistent with the form \xpoma where
in all bins of and
. In the measured range, the diffractive structure function
approximately scales with at fixed . In an Ingelman-Schlein type
model, where commonly used pomeron flux factor normalisations are assumed, it
is found that the quarks within the pomeron do not saturate the momentum sum
rule.Comment: 36 pages, latex, 11 figures appended as uuencoded fil
Measurement of inclusive D*+- and associated dijet cross sections in photoproduction at HERA
Inclusive photoproduction of D*+- mesons has been measured for photon-proton
centre-of-mass energies in the range 130 < W < 280 GeV and a photon virtuality
Q^2 < 1 GeV^2. The data sample used corresponds to an integrated luminosity of
37 pb^-1. Total and differential cross sections as functions of the D*
transverse momentum and pseudorapidity are presented in restricted kinematical
regions and the data are compared with next-to-leading order (NLO) perturbative
QCD calculations using the "massive charm" and "massless charm" schemes. The
measured cross sections are generally above the NLO calculations, in particular
in the forward (proton) direction. The large data sample also allows the study
of dijet production associated with charm. A significant resolved as well as a
direct photon component contribute to the cross section. Leading order QCD
Monte Carlo calculations indicate that the resolved contribution arises from a
significant charm component in the photon. A massive charm NLO parton level
calculation yields lower cross sections compared to the measured results in a
kinematic region where the resolved photon contribution is significant.Comment: 32 pages including 6 figure
Search for charged Higgs decays of the top quark using hadronic tau decays
We present the result of a search for charged Higgs decays of the top quark,
produced in collisions at 1.8 TeV. When the charged
Higgs is heavy and decays to a tau lepton, which subsequently decays
hadronically, the resulting events have a unique signature: large missing
transverse energy and the low-charged-multiplicity tau. Data collected in the
period 1992-1993 at the Collider Detector at Fermilab, corresponding to
18.70.7~pb, exclude new regions of combined top quark and charged
Higgs mass, in extensions to the standard model with two Higgs doublets.Comment: uuencoded, gzipped tar file of LaTeX and 6 Postscript figures; 11 pp;
submitted to Phys. Rev.
Inclusive jet cross section in collisions at TeV
The inclusive jet differential cross section has been measured for jet
transverse energies, , from 15 to 440 GeV, in the pseudorapidity region
0.10.7. The results are based on 19.5 pb of data
collected by the CDF collaboration at the Fermilab Tevatron collider. The data
are compared with QCD predictions for various sets of parton distribution
functions. The cross section for jets with GeV is significantly
higher than current predictions based on O() perturbative QCD
calculations. Various possible explanations for the high- excess are
discussed.Comment: 8 pages with 2 eps uu-encoded figures Submitted to Physical Review
Letter
Measurement of Jet Shapes in Photoproduction at HERA
The shape of jets produced in quasi-real photon-proton collisions at
centre-of-mass energies in the range GeV has been measured using the
hadronic energy flow. The measurement was done with the ZEUS detector at HERA.
Jets are identified using a cone algorithm in the plane with a
cone radius of one unit. Measured jet shapes both in inclusive jet and dijet
production with transverse energies GeV are presented. The jet
shape broadens as the jet pseudorapidity () increases and narrows
as increases. In dijet photoproduction, the jet shapes have been
measured separately for samples dominated by resolved and by direct processes.
Leading-logarithm parton-shower Monte Carlo calculations of resolved and direct
processes describe well the measured jet shapes except for the inclusive
production of jets with high and low . The observed
broadening of the jet shape as increases is consistent with the
predicted increase in the fraction of final state gluon jets.Comment: 29 pages including 9 figure
Measurement of Dijet Angular Distributions at CDF
We have used 106 pb^-1 of data collected in proton-antiproton collisions at
sqrt(s)=1.8 TeV by the Collider Detector at Fermilab to measure jet angular
distributions in events with two jets in the final state. The angular
distributions agree with next to leading order (NLO) predictions of Quantum
Chromodynamics (QCD) in all dijet invariant mass regions. The data exclude at
95% confidence level (CL) a model of quark substructure in which only up and
down quarks are composite and the contact interaction scale is Lambda_ud(+) <
1.6 TeV or Lambda_ud(-) < 1.4 TeV. For a model in which all quarks are
composite the excluded regions are Lambda(+) < 1.8 TeV and Lambda(-) < 1. 6
TeV.Comment: 16 pages, 2 figures, 2 tables, LaTex, using epsf.sty. Submitted to
Physical Review Letters on September 17, 1996. Postscript file of full paper
available at http://www-cdf.fnal.gov/physics/pub96/cdf3773_dijet_angle_prl.p
Inclusive Search for Anomalous Production of High-pT Like-Sign Lepton Pairs in Proton-Antiproton Collisions at sqrt{s}=1.8 TeV
We report on a search for anomalous production of events with at least two
charged, isolated, like-sign leptons with pT > 11 GeV/c using a 107 pb^-1
sample of 1.8 TeV ppbar collisions collected by the CDF detector. We define a
signal region containing low background from Standard Model processes. To avoid
bias, we fix the final cuts before examining the event yield in the signal
region using control regions to test the Monte Carlo predictions. We observe no
events in the signal region, consistent with an expectation of
0.63^(+0.84)_(-0.07) events. We present 95% confidence level limits on new
physics processes in both a signature-based context as well as within a
representative minimal supergravity (tanbeta = 3) model.Comment: 15 pages, 4 figures. Minor textual changes, cosmetic improvements to
figures and updated and expanded reference
Search for New Particles Decaying to Dijets at CDF
We have used 106 pb^-1 of data collected with the Collider Detector at
Fermilab to search for new particles decaying to dijets. We exclude at the 95%
confidence level models containing the following new particles: axigluons and
flavor universal colorons with mass between 200 and 980 GeV/c, excited quarks
with mass between 80 and 570 GeV/c^2 and between 580 and 760 GeV/c^2, color
octet technirhos with mass between 260 and 480 GeV/c^2, W' bosons with mass
between 300 and 420 GeV/c^2, and E_6 diquarks with mass between 290 and 420
GeV/c^2.Comment: 18 pages, 4 figures, 1 table. Submitted to Physical Review D Rapid
Communications. Postscript file of paper is also available at
http://www-cdf.fnal.gov/physics/pub97/cdf3276_dijet_search_prd_rc.p
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