3,883 research outputs found
Electroweak Contributions to Squark Pair Production at the LHC
In this paper we compute electroweak contributions to the production of
squark pairs at hadron colliders. These include the exchange of electroweak
gauge bosons in the s-channel as well as electroweak gaugino exchange in the t-
and/or u-channel. In many cases these can interfere with the dominant QCD
contributions. As a result, we find sizable contributions to the production of
two SU(2) doublet squarks. At the LHC, they amount to 10 to 20% for typical
mSUGRA (or CMSSM) scenarios, but in more general scenarios they can vary
between -40 and +55%, depending on size and sign of the SU(2) gaugino mass. The
electroweak contribution to the total squark pair production rate at the LHC is
about 3.5 times smaller.Comment: 28 pages, 9 figure
Multiple Interactions in Two-Photon Collisions
We compute cross sections for events where two pairs of partons scatter off
each other in the same reaction, giving rise to at least 3
high--{\mbox{}} jets. Unlike in {\mbox{}}\ collisions we find
the signal to lie well above the background from higher order QCD processes. If
the usual ``eikonaliztion" assumption is correct, the signal should be readily
observable at LEP2, and might already be detectable in data taken at TRISTAN.Comment: 8 pages, plain LaTeX, 2 figures (not included). A compressed PS file
of the entire paper, including figures, can be obtained via anonymous ftp
from ftp://phenom.physics.wisc.edu/pub/preprints/1995/madph-95-921.ps.
Loop induced Higgs and Z boson couplings to Neutralinos and implications for collider and Dark Matter searches
We calculate the one-loop induced couplings of two gaugino-like neutralinos
to the and Higgs bosons in the Minimal Supersymmetric Standard Model. These
couplings, which vanish at the tree level, can be generated through loops
involving fermions and sfermions. We show that, while the neutralino
contribution to the invisible boson decay width remains small, the loop
induced couplings to the lightest Higgs boson might be sufficiently large to
yield a rate of invisible decays of this Higgs boson that should be detectable
at future colliders. We also study the implications of these couplings
for direct searches of Dark Matter and show that they can modify appreciably
the neutralino-nucleon elastic cross section for some parameter range.Comment: LaTeX with 6 (e)ps and 2 axodraw figures, 25 pages in total;
axodraw.sty is included v.2: Added one figure and some discussions; version
to appear in PR
First observations of beam losses due to bound-free pair production in a heavy-ion collider
We report the first observations of beam losses due to bound-free pair
production at the interaction point of a heavy-ion collider. This process is
expected to be a major luminosity limit for the Large Hadron Collider (LHC)
when it operates with 208Pb82+ ions because the localized energy deposition by
the lost ions may quench superconducting magnet coils. Measurements were
performed at the Relativistic Heavy Ion Collider (RHIC) during operation with
100 GeV/nucleon 63Cu29+ ions. At RHIC, the rate, energy and magnetic field are
low enough so that magnet quenching is not an issue. The hadronic showers
produced when the single-electron ions struck the RHIC beampipe were observed
using an array of photodiodes. The measurement confirms the order of magnitude
of the theoretical cross section previously calculated by others.Comment: 4 pages, 5 figures. Added journal ref. Corrected typos. Fixed fig 1.
Minor improvements to fig. 1,3,4. Rephrased a small number of sentences
(p1,3,4). Added numerical values of the aperture and the displacement for Au
(p 2). Changed reference 5, added name in acknowledgments (p 4
SUSY QCD Corrections to Higgs Pair Production from Bottom Quark Fusion
We present a complete next-to-leading order (NLO) calculation for the total
cross section for inclusive Higgs pair production via bottom-quark fusion at
the CERN Large Hadron Collider (LHC) in the minimal supersymmetric standard
model (MSSM) and the minimal supergravity model (mSUGRA). We emphasize the
contributions of squark and gluino loops (SQCD) and the decoupling properties
of our results for heavy squark and gluino masses. The enhanced couplings of
the b quark to the Higgs bosons in supersymmetric models with large tanb yield
large NLO SQCD corrections in some regions of parameter space.Comment: 24 pages, 10 figure
Supersymmetric Higgs pair discovery prospects at hadron colliders
We study the potential of hadron colliders in the search for the pair
production of neutral Higgs bosons in the framework of the Minimal
Supersymmetric Standard Model. Using analytical expressions for the relevant
amplitudes, we perform a detailed signal and background analysis, working out
efficient kinematical cuts for the extraction of the signal. The important role
of squark loop contributions to the signal is emphasised. If the signal is
sufficiently enhanced by these contributions, it could even be observable at
the next run of the upgraded Tevatron collider in the near future. At the LHC
the pair production of light and heavy Higgs bosons might be detectable
simultaneously.Comment: 5 pages, hep99, 6 figures; Presented at the International Europhysics
Conference on High Energy Physics, Tampere, Finland, 15-21 July 199
Effects of Lepton Flavour Violation on Chargino Production at the Linear Collider
We study the effects of lepton flavour violation (LFV) on the production
processes e+e- --> \chi+_i \chi-_j at a linear collider with longitudinal e+
and e- beam polarizations. In the case of LFV the sneutrino mass eigenstates
have no definite flavour, therefore, in the t-channel more than one sneutrino
mass eigenstate can contribute to the chargino production cross sections. Our
framework is the Minimal Supersymmetric Standard Model (MSSM) including LFV
terms. We show that in spite of the restrictions on the LFV parameters due to
the current limits on rare lepton decays, the cross section \sigma(e+e- -->
\chi+_1 \chi-_1) can change by a factor of 2 or more when varying the LFV
mixing angles. We point out that even if the present bound on BR(tau- --> e-
gamma) improves by a factor of thousand the influence of LFV on the chargino
production cross section can be significant. These results could have an
important impact on the strategies for determining the underlying model
parameters at the linear collider.Comment: 11pp; final version for JHE
Virtual Photon Strucutre Functions and the Parton Content of the Electron
We point out that in processes involving the parton content of the photon the
usual effective photon approximation should be modified. The reason is that the
parton content of virtual photons is logarithmically suppressed compared to
real photons. We describe this suppression using several simple, physically
motivated ans\"atze. Although the parton content of the electron in general no
longer factorizes into an electron flux function and a photon structure
function, it can still be expressed as a single integral. Numerical examples
are given for the \eplem\ collider TRISTAN as well as the collider HERA.Comment: 16 pages and 3 figures (available from DREES@WSICPHEN as topdraw or
PS files); LaTeX with equation.sty; MAD/PH/819, BU 94-0
Assessment of performance indicators in Hospitals University of Medical Sciences based on the standards of the Ministry of Health
Background and amis: One of the main issues in hospitals, to determine the efficiency and effectiveness of hospital beds are how to exploit it . For this indicator, the introduction of performance indicators are computed and compared with standards of health care services can be paid for hospital assessment activities and capabilities. This study compares the performance standards of medical care Chahar Mahal Va Bakhtiari province's health ministry. Methods: This study is descriptive and analytical and trend study in which data were collected from 498 pcs form 2006 till 2012 has been studied. Results: The tables and charts in this review suggest that the bed occupancy index in comparison with the standard country between 2008 and 2009 unfavorable and 2006. 2007 years, 2010 and 2011 in moderate country. Average index hospitalization days in the period, compared with a national standard was satisfactory (less than 3.5 preferred), three performance indicators examined in this study Turnover is the optimal value of this index in the standard state (less than 2 day), which is desirable in the years 2006 and 2007 years, average 2008 and 2009 years were 2010 and 2011 unfavorable. Conclusions Conclusion The performance indicators of hospitals toward optimal health standards have been average
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