924 research outputs found
Prospects for Discovering Supersymmetry at the LHC
Supersymmetry is one of the best-motivated candidates for physics beyond the
Standard Model that might be discovered at the LHC. There are many reasons to
expect that it may appear at the TeV scale, in particular because it provides a
natural cold dark matter candidate. The apparent discrepancy between the
experimental measurement of g_mu - 2 and the Standard model value calculated
using low-energy e+ e- data favours relatively light sparticles accessible to
the LHC. A global likelihood analysis including this, other electroweak
precision observables and B-decay observables suggests that the LHC might be
able to discover supersymmetry with 1/fb or less of integrated luminosity. The
LHC should be able to discover supersymmetry via the classic missing-energy
signature, or in alternative phenomenological scenarios. The prospects for
discovering supersymmetry at the LHC look very good.Comment: 8 pages, 11 figure
Higgs boson bounds in non-minimal supersymmetric standard models
In the minimal supersymmetric standard model (MSSM), when radiative
corrections are included, the mass of the lightest Higgs boson is
bounded by for and a scale of supersymmetry
breaking . In non-minimal supersymmetric standard models (NMSSM)
upper bounds on the mass of the corresponding scalar Higgs boson arise if the
theory is required to remain perturbative up to scales . We
have computed those bounds for two illustrative NMSSM: i) A model with an
arbitrary number of gauge singlets; ii) A model with three triplets
with . We have integrated numerically the corresponding
renormalization group equations (RGE), including the top and bottom quark
Yukawa couplings, and added one-loop radiative corrections. For
the absolute bounds are for both models.Comment: 8 pages, (Talk presented at the XXVI INTERNATIONAL CONFERENCE ON HIGH
ENERGY PHYSICS, August 6-12, 1992, Dallas), latex, IEM-FT-60/92, 3 figures
(available by Fax upon request
Complete two-loop effective potential approximation to the lightest Higgs scalar boson mass in supersymmetry
I present a method for accurately calculating the pole mass of the lightest
Higgs scalar boson in supersymmetric extensions of the Standard Model, using a
mass-independent renormalization scheme. The Higgs scalar self-energies are
approximated by supplementing the exact one-loop results with the second
derivatives of the complete two-loop effective potential in Landau gauge. I
discuss the dependence of this approximation on the choice of renormalization
scale, and note the existence of particularly poor choices which fortunately
can be easily identified and avoided. For typical input parameters, the
variation in the calculated Higgs mass over a wide range of renormalization
scales is found to be of order a few hundred MeV or less, and is significantly
improved over previous approximations.Comment: 5 pages, 1 figure. References added, sample test model parameters
listed, minor wording change
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
Radiative Corrections to the Higgs Boson Mass for a Hierarchical Stop Spectrum
An effective theory approach is used to compute analytically the radiative
corrections to the mass of the light Higgs boson of the Minimal Supersymmetric
Standard Model when there is a hierarchy in the masses of the stops (M_st1 >>
M_st2 >> M_top, with moderate stop mixing). The calculation includes up to
two-loop leading and next-to-leading logarithmic corrections dependent on the
QCD and top-Yukawa couplings, and is further completed by two-loop
non-logarithmic corrections extracted from the effective potential. The results
presented disagree already at two-loop-leading-log level with widely used
findings of previous literature. Our formulas can be used as the starting point
for a full numerical resummation of logarithmic corrections to all loops, which
would be mandatory if the hierarchy between the stop masses is large.Comment: 42 pages, LaTeX, 13 figure
Dominant Two-Loop Corrections to the MSSM Finite Temperature Effective Potential
We show that two-loop corrections to the finite temperature effective
potential in the MSSM can have a dramatic effect on the strength of the
electroweak phase transition, making it more strongly first order. The change
in the order parameter can be as large as 75\% of the one-loop daisy
improved result. This effect can be decisive to widen the region in parameter
space where erasure of the created baryons by sphaleron processes after the
transition is suppressed and hence, where electroweak baryogenesis might be
successful. We find an allowed region with \tan\beta\simlt 4.5 and a Higgs
boson with standard couplings and mass below within the reach of LEP
II.Comment: 20 pages, LaTeX. 4 postscript figure
What if Supersymmetry Breaking Unifies beyond the GUT Scale?
We study models in which soft supersymmetry-breaking parameters of the MSSM
become universal at some unification scale, , above the GUT scale,
\mgut. We assume that the scalar masses and gaugino masses have common
values, and respectively, at . We use the
renormalization-group equations of the minimal supersymmetric SU(5) GUT to
evaluate their evolutions down to \mgut, studying their dependences on the
unknown parameters of the SU(5) superpotential. After displaying some generic
examples of the evolutions of the soft supersymmetry-breaking parameters, we
discuss the effects on physical sparticle masses in some specific examples. We
note, for example, that near-degeneracy between the lightest neutralino and the
lighter stau is progressively disfavoured as increases. This has the
consequence, as we show in planes for several different values
of , that the stau coannihilation region shrinks as
increases, and we delineate the regions of the plane
where it is absent altogether. Moreover, as increases, the focus-point
region recedes to larger values of for any fixed and
. We conclude that the regions of the plane that are
commonly favoured in phenomenological analyses tend to disappear at large
.Comment: 24 pages with 11 eps figures; references added, some figures
corrected, discussion extended and figure added; version to appear in EPJ
No Evidence Supporting Flare Driven High-Frequency Global Oscillations
The underlying physics that generates the excitations in the global
low-frequency, < 5.3 mHz, solar acoustic power spectrum is a well known process
that is attributed to solar convection; However, a definitive explanation as to
what causes excitations in the high-frequency regime, > 5.3 mHz, has yet to be
found. Karoff and Kjeldsen (Astrophys. J. 678, 73-76, 2008) concluded that
there is a correlation between solar flares and the global high-frequency solar
acoustic waves. We have used the Global Oscillations Network Group (GONG)
helioseismic data in an attempt to verify Karoff and Kjeldsen (2008) results as
well as compare the post-flare acoustic power spectrum to the pre-flare
acoustic power spectrum for 31 solar flares. Among the 31 flares analyzed, we
observe that a decrease in acoustic power after the solar flare is just as
likely as an increase. Furthermore, while we do observe variations in acoustic
power that are most likely associated with the usual p-modes associated with
solar convection, these variations do not show any significant temporal
association with flares. We find no evidence that consistently supports flare
driven high-frequency waves.Comment: 20 pages, 9 figures, Accepted for publication in Solar Physic
Revisiting the Higgs Mass and Dark Matter in the CMSSM
Taking into account the available accelerator and astrophysical constraints,
the mass of the lightest neutral Higgs boson h in the minimal supersymmetric
extension of the Standard Model with universal soft supersymmetry-breaking
masses (CMSSM) has been estimated to lie between 114 and ~ 130 GeV. Recent data
from ATLAS and CMS hint that m_h ~ 125 GeV, though m_h ~ 119 GeV may still be a
possibility. Here we study the consequences for the parameters of the CMSSM and
direct dark matter detection if the Higgs hint is confirmed, focusing on the
strips in the (m_1/2, m_0) planes for different tan beta and A_0 where the
relic density of the lightest neutralino chi falls within the range of the
cosmological cold dark matter density allowed by WMAP and other experiments. We
find that if m_h ~ 125 GeV focus-point strips would be disfavoured, as would
the low-tan beta stau-chi and stop -chi coannihilation strips, whereas the
stau-chi coannihilation strip at large tan beta and A_0 > 0 would be favoured,
together with its extension to a funnel where rapid annihilation via
direct-channel H/A poles dominates. On the other hand, if m_h ~ 119 GeV more
options would be open. We give parametrizations of WMAP strips with large tan
beta and fixed A_0/m_0 > 0 that include portions compatible with m_h = 125 GeV,
and present predictions for spin-independent elastic dark matter scattering
along these strips. These are generally low for models compatible with m_h =
125 GeV, whereas the XENON100 experiment already excludes some portions of
strips where m_h is smaller.Comment: 24 pages, 9 figure
Higgs-boson production associated with a bottom quark at hadron colliders with SUSY-QCD corrections
The Higgs boson production p p (p\bar p) -> b h +X via b g -> b h at the LHC,
which may be an important channel for testing the bottom quark Yukawa coupling,
is subject to large supersymmetric quantum corrections. In this work the
one-loop SUSY-QCD corrections to this process are evaluated and are found to be
quite sizable in some parameter space. We also study the behavior of the
corrections in the limit of heavy SUSY masses and find the remnant effects of
SUSY-QCD. These remnant effects, which are left over in the Higgs sector by the
heavy sparticles, are found to be so sizable (for a light CP-odd Higgs and
large \tan\beta) that they might be observable in the future LHC experiment.
The exploration of such remnant effects is important for probing SUSY,
especially in case that the sparticles are too heavy (above TeV) to be directly
discovered at the LHC.Comment: Results for the Tevatron adde
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