31 research outputs found
Selectron Pair Production at e-e- and e+e- Colliders with Polarized Beams
We investigate selectron pair production and decay in e-e- scattering and
e+e- annihilation with polarized beams taking into account neutralino mixing as
well as ISR and beamstrahlung corrections. One of the main advantages of having
both modes at disposal is their complementarity concerning the threshold
behaviour of selectron pair production. In e-e- the cross sections at threshold
for seleectron_R selectron_R and selectron_L selectron_L rise proportional to
the momentum of the selectron and in e+ e- that for selectron_R selectron_L.
Measurements at threshold with polarized beams can be used to determine the
selectron masses precisely. Moreover we discuss how polarized electron and
positron beams can be used to establish directly the weak quantum numbers of
the selectrons. We also use selectron pair production to determine the gaugino
mass parameter M_1. This is of particular interest for scenarios with
non-universal gaugino masses at a high scale resulting in |M_1| << |M_2| at the
electroweak scale. Moreover, we consider also the case of a non-vanishing
selectron mixing and demonstrate that it leads to a significant change in the
phenomenology of selectrons.Comment: LaTex, 23 pages, 14 figures, v2, typos corrected, version to appear
in Eur.Phys.J.
CP violation through particle mixing and the H-A lineshape
We consider the possibility of looking for CP-mixing effects in two-Higgs
doublet models (and particularly in the MSSM) by studying the lineshape of the
CP-even (H) and CP-odd (A) neutral scalars. In most cases H and A come quite
degenerate in mass, and their s-channel production would lead to nearly
overlapping resonances. CP-violating effects may connect these two Higgs
bosons, giving origin to one-loop particle mixing, which, due to their mass
proximity, can be resonantly enhanced. The corresponding transition amplitude
contains then CP-even and CP-odd components; besides the signal of
intereference between both amplitudes, leading to a CP-odd asymmetry, we
propose to look for the mixing probability itself, a quantity which, although
CP-even, can originate only from a CP-odd amplitude. We show that, in general,
the effect of such a mixing probability cannot be mimicked by (or be
re-absorbed into) a simple redefinition of the H and A masses in the context of
a CP-conserving model. Specifically, the effects of the CP-mixing are such
that, either the mass-splitting of the H and A bosons cannot be accounted for
in the absence of CP-mixing, and/or the detailed energy dependence of the
produced lineshape is clearly different from the one obtained by redefining the
masses, but not allowing any mixing. This analysis suggests that the detailed
study of the lineshape of this Higgs system may provide valuable information on
the CP nature of the underlying theory.Comment: 16 pages, 13 figures; v2: added one reference; v3: radiative
corrections taken into account, agreement now with CP-SuperH, conclusions
unchanged. v3 matches the paper version accepted for publication in JHE
Refining the predictions of supersymmetric CP-violating models: A top-down approach
We explore in detail the consequences of the CP-violating phases residing in
the supersymmetric and soft SUSY breaking parameters in the approximation that
family flavour mixings are ignored. We allow for non-universal boundary
conditions and in such a consideration the model is described by twelve
independent CP-violating phases and one angle which misaligns the vacuum
expectation values (VEVs) of the Higgs scalars. We run two-loop renormalization
group equations (RGEs), for all parameters involved, including phases, and we
properly treat the minimization conditions using the one-loop effective
potential with CP-violating phases included. We show that the two-loop running
of phases may induce sizable effects for the electric dipole moments (EDMs)
that are absent in the one-loop RGE analysis. Also important corrections to the
EDMs are induced by the Higgs VEVs misalignment angle which are sizable in the
large tanb region. Scanning the available parameter space we seek regions
compatible with accelerator and cosmological data with emphasis on rapid
neutralino annihilations through a Higgs resonance. It is shown that large
CP-violating phases, as required in Baryogenesis scenarios, can be tuned to
obtain agreement with WMAP3 cold dark matter constraints, EDMs and all
available accelerator data, in extended regions of the parameter space which
may be accessible to LHC.Comment: 41 pages, 22 eps figures. A reference added and a typo corrected;
version to appear in JHE
Probing neutrino properties with charged scalar lepton decays
Supersymmetry with bilinear R-parity violation provides a predictive
framework for neutrino masses and mixings in agreement with current neutrino
oscillation data. The model leads to striking signals at future colliders
through the R-parity violating decays of the lightest supersymmetric particle.
Here we study charged scalar lepton decays and demonstrate that if the scalar
tau is the LSP (i) it will decay within the detector, despite the smallness of
the neutrino masses, (ii) the relative ratio of branching ratios Br({tilde
tau}_1 --> e sum nu_i)/ Br({tilde tau}_1 --> mu sum nu_i) is predicted from the
measured solar neutrino angle, and (iii) scalar muon and scalar electron decays
will allow to test the consistency of the model. Thus, bilinear R-parity
breaking SUSY will be testable at future colliders also in the case where the
LSP is not the neutralino.Comment: 24 pages, 8 ps figs Report-no.: IFIC/02-33 and ZU-TH 11/0
TESLA Technical Design Report Part III: Physics at an e+e- Linear Collider
The TESLA Technical Design Report Part III: Physics at an e+e- Linear
ColliderComment: 192 pages, 131 figures. Some figures have reduced quality. Full
quality figures can be obtained from http://tesla.desy.de/tdr. Editors -
R.-D. Heuer, D.J. Miller, F. Richard, P.M. Zerwa
Linear Collider Physics Resource Book for Snowmass 2001, 3: Studies of Exotic and Standard Model Physics
This Resource Book reviews the physics opportunities of a next-generation e+e- linear collider and discusses options for the experimental program. Part 3 reviews the possible experiments on that can be done at a linear collider on strongly coupled electroweak symmetry breaking, exotic particles, and extra dimensions, and on the top quark, QCD, and two-photon physics. It also discusses the improved precision electroweak measurements that this collider will make available.This Resource Book reviews the physics opportunities of a next-generation e+e- linear collider and discusses options for the experimental program. Part 3 reviews the possible experiments on that can be done at a linear collider on strongly coupled electroweak symmetry breaking, exotic particles, and extra dimensions, and on the top quark, QCD, and two-photon physics. It also discusses the improved precision electroweak measurements that this collider will make available
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Physics opportunities at mu+ mu- Higgs factories
We update theoretical studies of the physics opportunities presented by {mu}{sup +} {mu}{sup -} Higgs factories. Interesting measurements of the Standard Model Higgs decays into {bar b}b, {tau}{sup +} {tau}{sup -} and WW* may be possible if the Higgs mass is less than about 160 GeV, as preferred by the precision electroweak data, the mass range being extended by varying appropriately the beam energy resolution. A suitable value of the beam energy resolution would also enable the uncertainty in the b-quark mass to be minimized, facilitating measurements of parameters in the MSSM at such a first {mu}{sup +} {mu}{sup -} Higgs factory. These measurements would be sensitive to radiative corrections to the Higgs-fermion-antifermion decay vertices, which may violate CP. Radiative corrections in the MSSM may also induce CP violation in Higgs-mass mixing, which can be probed via various asymmetries measurable using polarized {mu}{sup +} {mu}{sup -} beams. In addition, Higgs-chargino couplings may be probed at a second {mu}{sup +} {mu}{sup -} Higgs factory
A distribution method for solving SAT in grids
Abstract. The emerging large-scale computational grid infrastructure is providing an interesting platform for massive distributed computations. In this paper the problem of exploiting such computational grids for solving challenging propositional satisfiability problem (SAT) instances is studied. When designing a distributed algorithm for a large loosely coupled computational grid, a number of grid specific problems need to be tackled including the heterogeneity of the resources, inherent communication delays, and high failure probabilities of grid jobs. In this work a novel distribution method for solving SAT problem instances, called scattering, is introduced. The key advantages of scattering are that it can be used in conjunction with any sequential SAT solver (including industrial black box solvers), the distribution heuristic is strictly separated from the heuristic used in sequential solving, and it requires no communication between processes solving subproblems but still allows coordination of such processes. An implementation of the method has been developed for NorduGrid, a large widely distributed production-level grid running in Scandinavia. The implementation has been benchmarked with test cases including random 3SAT and challenging industrial benchmarks used in previous SAT competitions.