1,311 research outputs found
Challenges for MSSM Higgs searches at Hadron Colliders
In this article we analyze the impact of B-physics and Higgs physics at LEP
on standard and non-standard Higgs bosons searches at the Tevatron and the LHC,
within the framework of minimal flavor violating supersymmetric models. The
B-physics constraints we consider come from the experimental measurements of
the rare B-decays b -> s gamma and B_u -> tau nu and the experimental limit on
the B_s -> mu+ mu- branching ratio. We show that these constraints are severe
for large values of the trilinear soft breaking parameter A_t, rendering the
non-standard Higgs searches at hadron colliders less promising. On the contrary
these bounds are relaxed for small values of A_t and large values of the
Higgsino mass parameter mu, enhancing the prospects for the direct detection of
non-standard Higgs bosons at both colliders. We also consider the available
ATLAS and CMS projected sensitivities in the standard model Higgs search
channels, and we discuss the LHC's ability in probing the whole MSSM parameter
space. In addition we also consider the expected Tevatron collider
sensitivities in the standard model Higgs h -> b bbar channel to show that it
may be able to find 3 sigma evidence in the B-physics allowed regions for small
or moderate values of the stop mixing parameter.Comment: 22 pages, 5 figures. Added references and acknowledgements. Submitted
to PR
On the treatment of threshold effects in SUSY spectrum computations
We take a critical view of the treatment of threshold effects in SUSY
spectrum computations from high-scale input. We discuss the two principal
methods of (a) renormalization at a common SUSY scale versus (b) integrating
out sparticles at their own mass scales. We point out problems in the
implementations in public spectrum codes, together with suggestions for
improvements. In concrete examples, we compare results of Isajet7.72 and
Spheno2.2.3, and present the improvements done in Isajet7.73. We also comment
on theoretical uncertainties. Last but not least, we outline how a consistent
multiscale approach may be achieved.Comment: 15 pages, 1 figur
Looking for a heavy wino LSP in collider and dark matter experiments
We investigate the phenomenology of a wino LSP as obtained in AMSB and some
string models. The WMAP constraint on the DM relic density implies a wino LSP
mass of 2.0-2.3 TeV. We find a viable signature for such a heavy wino at CLIC,
operating at its highest CM energy of 5 TeV. One also expects a viable
monochromatic -ray signal from its pair-annihilation at the galactic
centre at least for cuspy DM halo profiles.Comment: A discussion on non-perturbative effects on annihilation cross
section of TeV scale wino LSP added. Version to appear in Phys. Rev. D
FCNCs in supersymmetric multi-Higgs doublet models
We conduct a general discussion of supersymmetric models with three families
in the Higgs sector. We analyse the scalar potential, and investigate the
minima conditions, deriving the mass matrices for the scalar, pseudoscalar and
charged states. Depending on the Yukawa couplings and the Higgs spectrum, the
model might allow the occurrence of potentially dangerous flavour changing
neutral currents at the tree-level. We compute model-independent contributions
for several observables, and as an example we apply this general analysis to a
specific model of quark-Higgs interactions, discussing how compatibility with
current experimental data constrains the Higgs sector.Comment: 30 pages, 9 figures. Comments and references added. Final version
published in Physical Review
Supersymmetric Musings on the Predictivity of Family Symmetries
We discuss the predictivity of family symmetries for the soft supersymmetry
breaking parameters in the framework of supergravity. We show that unknown
details of the messenger sector and the supersymmetry breaking hidden sector
enter into the soft parameters, making it difficult to obtain robust
predictions. We find that there are specific choices of messenger fields which
can improve the predictivity for the soft parameters.Comment: 20 pages, 5 figure
Resonance-continuum interference in the di-photon Higgs signal at the LHC
A low mass Standard Model Higgs boson should be visible at the Large Hadron
Collider through its production via gluon-gluon fusion and its decay to two
photons. We compute the interference of this resonant process, gg -> H -> gamma
gamma, with the continuum QCD background, gg -> gamma gamma induced by quark
loops. Helicity selection rules suppress the effect, which is dominantly due to
the imaginary part of the two-loop gg -> gamma gamma scattering amplitude. The
interference is destructive, but only of order 5% in the Standard Model, which
is still below the 10-20% present accuracy of the total cross section
prediction. We comment on the potential size of such effects in other Higgs
models.Comment: 10 pages, 2 figure
Densities and phase equilibria of hydrogen, propane and vegetable oil mixtures. Experimental data and thermodynamic modeling
Heterogeneous catalytic gas-liquid reactions are intensified when carried out in the homogenous fluid phase by means of a supercritical co-solvent. For instance, supercritical propane is used to enhance yield in the hydrogenation of vegetable oils. Besides phase equilibrium knowledge, volumetric information is also needed to elucidate kinetic mechanisms and design continuous supercritical reactors. In this work, we report new experimental PvT data of the reactive mixture H2+sunflower oil+propane using the isochoric method. In addition, the phase equilibria and PvT data are modeled with the GCA and RK-PR equations of state, respectively. The isochoric method not only provides PvT information under the reaction conditions, but also the reactive system compressibility, key variable to attain enhanced transport properties in the supercritical reactors.Fil: Hegel, Pablo Ezequiel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; ArgentinaFil: Cotabarren, Natalia Soledad. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; ArgentinaFil: Brignole, Esteban Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; ArgentinaFil: Pereda, Selva. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; Argentina. University of KwaZulu-Natal; Sudáfric
Determining the Structure of Supersymmetry-Breaking with Renormalization Group Invariants
If collider experiments demonstrate that the Minimal Supersymmetric Standard
Model (MSSM) is a good description of nature at the weak scale, the
experimental priority will be the precise determination of superpartner masses.
These masses are governed by the weak scale values of the soft supersymmetry
(SUSY)-breaking parameters, which are in turn highly dependent on the
SUSY-breaking scheme present at high scales. It is therefore of great interest
to find patterns in the soft parameters that can distinguish different high
scale SUSY-breaking structures, identify the scale at which the breaking is
communicated to the visible sector, and determine the soft breaking parameters
at that scale. In this work, we demonstrate that 1-loop Renormalization
Group~(RG) invariant quantities present in the MSSM may be used to answer each
of these questions. We apply our method first to generic flavor-blind models of
SUSY-breaking, and then examine in detail the subset of these models described
by General Gauge Mediation and the constrained MSSM with non-universal Higgs
masses. As RG invariance generally does not hold beyond leading-log order, we
investigate the magnitude and direction of the 2-loop corrections. We find that
with superpartners at the TeV scale, these 2-loop effects are either
negligible, or they are of the order of optimistic experimental uncertainties
and have definite signs, which allows them to be easily accounted for in the
overall uncertainty.Comment: v2 -- references added, version to be published in PRD; 40 page
Upper Bounds on the Lightest Higgs Boson Mass in General Supersymmetric Standard Models
In a general supersymmetric standard model there is an upper bound on
the tree level mass of the lightest Higgs boson which depends on the
electroweak scale, and the gauge and Yukawa couplings of the
theory. When radiative corrections are included, the allowed region in the
plane depends on the scale , below which the theory
remains perturbative, and the supersymmetry breaking scale , that we
fix to . In the minimal model with : $m_h<130\
GeVm_t<185\ GeV\Lambda=10^{16}\ GeVm_h<145\ GeVm_t<185\ GeV\Lambda=10^{16}\ GeVm_h<155\ GeVm_t<190\ GeV\Lambda\Lambda_sm_hm_t\Lambda=10\ TeVm_hm_t415\
GeV385\ GeV$, respectively.Comment: 13 pages, latex, IEM-FT-64/92 (5 postscript figures availables upon
request
Supergravity Radiative Effects on Soft Terms and the Term
We compute quadratically divergent supergravity one-loop effects on soft
supersymmetry-breaking parameters and the term in generic hidden sector
supergravity models. These effects can significantly modify the matching
condition for soft parameters at the Planck scale and also provide several new
sources of the term which are naturally of order the weak scale. We also
discuss some phenomenological implications of these effects, particularly the
violation of the scalar mass universality which may lead to dangerous FCNC
phenomena, and apply the results to superstring effective supergravity models.Comment: 12 pages, REVTEX. One reference is adde
- …