734 research outputs found
Production and FCNC decay of supersymmetric Higgs bosons into heavy quarks in the LHC
We analyze the production and subsequent decay of the neutral MSSM Higgs
bosons (h = h^0, H^0, A^0) mediated by flavor changing neutral currents (FCNC)
in the LHC collider. We have computed the h-production cross-section times the
FCNC branching ratio, \sigma(pp -> h -> qq') = \sigma(pp -> h) B(h -> qq'), in
the LHC focusing on the strongly-interacting FCNC sector. Here qq' is an
electrically neutral pair of quarks of different flavors, the dominant modes
being those containing a heavy quark: tc or bs. We determine the maximum
production rates for each of these modes and identify the relevant regions of
the MSSM parameter space, after taking into account the severe restrictions
imposed by low energy FCNC processes. The analysis of \sigma(pp -> h -> qq')
singles out regions of the MSSM parameter space different from those obtained
by maximizing only the branching ratio, due to non-trivial correlations between
the parameters that maximize/minimize each isolated factor. The production
rates for the bs channel can be huge for a FCNC process (0.1-1 pb), but its
detection can be problematic. The production rates for the tc channel are more
modest (10^{-3}-10^{-2} pb), but its detection should be easier due to the
clear-cut top quark signature. A few thousand tc events could be collected in
the highest luminosity phase of the LHC, with no counterpart in the SM.Comment: 25 pages, 9 figures, 2 tables, LaTeX 2e. Typos corrected. Version to
appear in JHE
Sfermion Precision Measurements at a Linear Collider
At future e+- e- linear colliders, the event rates and clean signals of
scalar fermion production - in particular for the scalar leptons - allow very
precise measurements of their masses and couplings and the determination of
their quantum numbers. Various methods are proposed for extracting these
parameters from the data at the sfermion thresholds and in the continuum. At
the same time, NLO radiative corrections and non-zero width effects have been
calculated in order to match the experimental accuracy. The substantial mixing
expected for the third generation sfermions opens up additional opportunities.
Techniques are presented for determining potential CP-violating phases and for
extracting tan(beta) from the stau sector, in particular at high values. The
consequences of possible large mass differences in the stop and sbottom system
are explored in dedicated analyses.Comment: Expanded version of contributions to the proceedings of ICHEP'02
(Amsterdam) and LCWS 2002 (Jeju Island
Stride: a flexible software platform for high-performance ultrasound computed tomography
BACKGROUND AND OBJECTIVE: Advanced ultrasound computed tomography techniques like full-waveform inversion are mathematically complex and orders of magnitude more computationally expensive than conventional ultrasound imaging methods. This computational and algorithmic complexity, and a lack of open-source libraries in this field, represent a barrier preventing the generalised adoption of these techniques, slowing the pace of research, and hindering reproducibility. Consequently, we have developed Stride, an open-source Python library for the solution of large-scale ultrasound tomography problems. METHODS: On one hand, Stride provides high-level interfaces and tools for expressing the types of optimisation problems encountered in medical ultrasound tomography. On the other, these high-level abstractions seamlessly integrate with high-performance wave-equation solvers and with scalable parallelisation routines. The wave-equation solvers are generated automatically using Devito, a domain-specific language, and the parallelisation routines are provided through the custom actor-based library Mosaic. RESULTS: We demonstrate the modelling accuracy achieved by our wave-equation solvers through a comparison (1) with analytical solutions for a homogeneous medium, and (2) with state-of-the-art modelling software applied to a high-contrast, complex skull section. Additionally, we show through a series of examples how Stride can handle realistic numerical and experimental tomographic problems, in 2D and 3D, and how it can scale robustly from a local multi-processing environment to a multi-node high-performance cluster. CONCLUSIONS: Stride enables researchers to rapidly and intuitively develop new imaging algorithms and to explore novel physics without sacrificing performance and scalability. This will lead to faster scientific progress in this field and will significantly ease clinical translation
Supersymmetric Electroweak Corrections to Sbottom Decay into Lighter Stop and Charged Higgs Boson
The Yukawa corrections of order ,
and to the width of sbottom decay into lighter
stop plus charged Higgs boson are calculated in the Minimal Supersymmetric
Standard Model. These corrections depend on the masses of charged Higgs boson
and lighter stop, and the parameters and . For favorable
parameter values, the corrections decrease or increase the decay widths
significantly. Especially for high values of (=30) the corrections
exceed at least 10% for both and decay. But for low
values of (=4,10) the corrections are small and the magnitudes are
less than 10%. The numerical calculations also show that using the running
bottom quark mass which includes the QCD effects and resums all high order
-enhanced effects can improve much the convergence of the
perturbation expansion.Comment: LateX, 27 pages, 13 ps figures. 12 figures updated, a figure and some
references adde
Complete resummation of chirally-enhanced loop-effects in the MSSM with non-minimal sources of flavor-violation
In this article we present the complete resummation of the leading
chirally-enhanced corrections stemming from gluino-squark, chargino-sfermion
and neutralino-sfermion loops in the MSSM with non-minimal sources of
flavor-violation. We compute the finite renormalization of fermion masses and
the CKM matrix induced by chirality-flipping self-energies. In the decoupling
limit Msusy>>v, which is an excellent approximation to the full theory, we give
analytic results for the effective gaugino(higgsino)-fermion-sfermion and the
Higgs-fermion-fermion vertices. Using these vertices as effective Feynman
rules, all leading chirally-enhanced corrections can consistently be included
into perturbative calculations of Feynman amplitudes. We also give a
generalized parametrization for the bare CKM matrix which extends the classic
Wolfenstein parametrization to the case of complex parameters lambda and A.Comment: 31 pages, 3 figures; typos correcte
Single top production at the LHC as a probe of R parity violation
We investigate the potential of the LHC to probe the R parity violating
couplings involving the third generation by considering single top production.
This study is based on particle level event generation for both signal and
background, interfaced to a simplified simulation of the ATLAS detector.Comment: 11 pages, 5 figures, 5 tables (LaTeX, style revtex), few references
adde
QCD Corrections to the Top Decay Mode t \ra \tilde{t} \chi^0
In supersymmetric theories, the top quark can decay into its scalar partner
plus a neutralino, with an appreciable rate. We calculate the QCD
corrections to this decay mode in the minimal supersymmetric extension of the
Standard Model. These corrections can be either positive or negative and
increase logarithmically with the gluino mass. For gluino masses below 1 TeV,
they are at most of the order of ten percent and therefore, well under control.Comment: 15 pages including 4 figs (using psfig.sty). A few typos have been
corrected and some references added. The results for Figs. 3 and 4 are now
presented in the dimensional reduction scheme. Version to appear in Phys.
Rev.
Effects of Long-Versus Short-Term Exposure to the Mediterranean Diet on Skin Microvascular Function and Quality of Life of Healthy Adults in Greece and the UK
The beneficial effects of the Mediterranean diet (MD) adherence in reducing cardiovascular disease (CVD) risk and improving CVD-related physiological indices have been well-documented. However, the exact MD adherence duration needed for these effects to occur is under-researched. The aim of the present, two-arm, two-site study clinical trial was to assess the effects of long- vs. short-term MD adherence on the skin microvascular circulation, and quality of life. Two groups were recruited, one being long-term MD adherers (>5 years; from Greece; control group), and one of the non-adherers (from the UK), with the latter participating in a four-week MD intervention (intervention group). Our main outcome was skin microvascular function assessed by cutaneous vascular conductance (CVC). Secondary outcomes included quality of life, dietary intake, blood pressure and lipidemic profile. At the end of the intervention, both groups had high MD adherence. For the intervention group, significantly improved post-intervention CVC values were noted concerning the initial peak phase (2.0 ± 0.6 vs. 2.8 ± 0.8; p 0.05). CVC values of the control group, were however higher at the plateau phase in comparison to the intervention group (intervention end; 3.8 ± 0.8 vs. 3.1 ± 1.2; p 0.05). As per QoL, the physical domain was improved post-intervention (13.7 ± 1.2 vs. 15.9 ± 1.2; p 0.05). No differences were observed in the lipidemic profile between groups, or between the baseline and final intervention phases. The findings indicate that although short-term MD adherence is effective in improving certain microvascular physiological properties and QoL domains, there is room for additional improvement, observed in long-term adherers. Our findings are important in the design of future, MD-based, lifestyle interventions, with the advisable durations differing between target groups
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