791 research outputs found
A FORTRAN code for in SM and MSSM
Through the present paper, the code gamgamZZ is presented, which may be used
to calculate all possible observables related to the process , in either the Standard Model (SM), or the minimal sypersymmetric standard
model (MSSM) with real parameters.Comment: 13 pages, 7 figures Revised according to the EPJC Referee suggestion
Bounds on the mass of the b' quark, revisited
Recent results from the DELPHI collaboration led us to review the present
bounds on the b' quark mass. We use all available experimental data for m_b' >
96 GeV to constrain the b' quark mass as a function of the
Cabibbo-Kobayashi-Maskawa elements in a sequential four generations model. We
find that there is still room for a b' with a mass larger than 96 GeV.Comment: 9 pages and 7 figures. REVTEX
Possibilistic KNN regression using tolerance intervals
International audienceBy employing regression methods minimizing predictive risk, we are usually looking for precise values which tends to their true response value. However, in some situations, it may be more reasonable to predict intervals rather than precise values. In this paper, we focus to find such intervals for the K-nearest neighbors (KNN) method with precise values for inputs and output. In KNN, the prediction intervals are usually built by considering the local probability distribution of the neighborhood. In situations where we do not dispose of enough data in the neighborhood to obtain statistically significant distributions, we would rather wish to build intervals which takes into account such distribution uncertainties. For this latter we suggest to use tolerance intervals to build the maximal specific possibility distribution that bounds each population quantiles of the true distribution (with a fixed confidence level) that might have generated our sample set. Next we propose a new interval regression method based on KNN which take advantage of our possibility distribution in order to choose, for each instance, the value of K which will be a good trade-off between precision and uncertainty due to the limited sample size. Finally we apply our method on an aircraft trajectory prediction problem
Gluino Pair Production at Linear e^+e^- Colliders
We study the potential of high-energy linear colliders for the
production of gluino pairs within the Minimal Supersymmetric Standard Model
(MSSM). In this model, the process is mediated by
quark/squark loops, dominantly of the third generation, where the mixing of
left- and right-handed states can become large. Taking into account realistic
beam polarization effects, photon and -boson exchange, and current mass
exclusion limits, we scan the MSSM parameter space for various
center-of-mass energies to determine the regions, where gluino production
should be visible.Comment: 22 pages, 9 figure
The MSSM prediction for W+/- H-/+ production by gluon fusion
We discuss the associated W+/- H-/+ production in p p collision for the Large
Hadron Collider. A complete one-loop calculation of the loop-induced subprocess
g g -> W+/- H-/+ is presented in the framework of the Minimal Supersymmetric
Standard Model (MSSM), and the possible enhancement of the hadronic cross
section is investigated under the constraint from the squark direct-search
results and the low-energy precision data. Because of the large destructive
interplay in the quark-loop contributions between triangle-type and box-type
diagrams, the squark-loop contributions turn out to be comparable with the
quark-loop ones. In particular, the hadronic cross section via gluon fusion can
be extensively enhanced by squark-pair threshold effects in the box-type
diagrams, so that it can be as large as the hadronic cross section via the b
b-bar -> W+/- H-/+ subprocess which appears at tree level.Comment: 35 pages, 7 figures, version to appear in Physical Review
Two ways to solve ASEP
The purpose of this article is to describe the two approaches to compute
exact formulas (which are amenable to asymptotic analysis) for the probability
distribution of the current of particles past a given site in the asymmetric
simple exclusion process (ASEP) with step initial data. The first approach is
via a variant of the coordinate Bethe ansatz and was developed in work of Tracy
and Widom in 2008-2009, while the second approach is via a rigorous version of
the replica trick and was developed in work of Borodin, Sasamoto and the author
in 2012.Comment: 10 pages, Chapter in "Topics in percolative and disordered systems
Superposition effect and clan structure in forward-backward multiplicity correlations
The main purpose of this paper is to discuss the link between
forward-backward multiplicity correlations properties and the shape of the
corresponding final charged particle multiplicity distribution in various
classes of events in different collisions. It is shown that the same mechanism
which explains the shoulder effect and the H_n vs. n oscillations in charged
particle multiplicity distributions, i.e., the weighted superposition of
different classes of events with negative binomial properties, reproduces
within experimental errors also the forward-backward multiplicity correlation
strength in e+e- annihilation at LEP energy and allows interesting predictions
for pp collisions in the TeV energy region, to be tested at LHC, for instance
with the ALICE detector. We limit ourselves at present to study substructures
properties in hadron-hadron collisions and e+e- annihilation; they are examined
as ancillary examples in the conviction that their understanding might be
relevant also in other more complex cases.Comment: 16 page
One-loop contributions of charginos and neutralinos to W-pair production in E+ E- collisions
We study the one-loop effects of charginos and neutralinos on the helicity
amplitudes for \eeww in the minimal supersymmetric standard model. The
calculation is tested by using two methods. First, the sum rule for the form
factors between \eeww and the process where the external bosons are
replaced by the corresponding Goldstone bosons is employed to test
the analytic expression and the accuracy of the numerical program. Second, the
decoupling property in the large mass limit is used to test the overall
normalization of the amplitudes. These two tests are most effectively carried
out when the amplitudes are expanded in terms of the modified minimal
subtraction () couplings of the standard model. The resulting
perturbation expansion is valid at collider energies below and around the
threshold of the light supersymmetric particles. We find that the corrections
to the cross section of the longitudinally polarized -pair production can be
as large as -1.4% at the threshold of the light chargino-pair production for
large scattering angles. We also study the effects of the CP-violating phase in
the chargino and neutralino sectors on the helicity amplitudes. We find that
the resulting CP-violating asymmetries can be at most 0.1%.Comment: 30 pages, 25 figures, Final verision, To appear in Physical Review D,
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Genomic differentiation during speciation-with-gene-flow: Comparing geographic and host-related variation in divergent life history adaptation in rhagoletis pomonella
A major goal of evolutionary biology is to understand how variation within populations gets partitioned into differences between reproductively isolated species. Here, we examine the degree to which diapause life history timing, a critical adaptation promoting population divergence, explains geographic and host-related genetic variation in ancestral hawthorn and recently derived apple-infesting races of Rhagoletis pomonella. Our strategy involved combining experiments on two different aspects of diapause (initial diapause intensity and adult eclosion time) with a geographic survey of genomic variation across four sites where apple and hawthorn flies co-occur from north to south in the Midwestern USA. The results demonstrated that the majority of the genome showing significant geographic and host-related variation can be accounted for by initial diapause intensity and eclosion time. Local genomic differences between sympatric apple and hawthorn flies were subsumed within broader geographic clines; allele frequency differences within the races across the Midwest were two to three-fold greater than those between the races in sympatry. As a result, sympatric apple and hawthorn populations displayed more limited genomic clustering compared to geographic populations within the races. The findings suggest that with reduced gene flow and increased selection on diapause equivalent to that seen between geographic sites, the host races may be recognized as different genotypic entities in sympatry, and perhaps species, a hypothesis requiring future genomic analysis of related sibling species to R. pomonella to test. Our findings concerning the way selection and geography interplay could be of broad significance for many cases of earlier stages of divergence-with-gene flow, including (1) where only modest increases in geographic isolation and the strength of selection may greatly impact genetic coupling and (2) the dynamics of how spatial and temporal standing variation is extracted by selection to generate differences between new and discrete units of biodiversity
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