355 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
Radiative Corrections to Neutralino and Chargino Masses in the Minimal Supersymmetric Model
We determine the neutralino and chargino masses in the MSSM at one-loop. We
perform a Feynman diagram calculation in the on-shell renormalization scheme,
including quark/squark and lepton/slepton loops. We find generically the
corrections are of order 6%. For a 20 GeV neutralino the corrections can be
larger than 20%. The corrections change the region of
parameter space which is ruled out by LEP data. We demonstrate that, e.g., for
a given and the lower limit on the parameter can shift
by 20 GeV.Comment: 11 pages, JHU-TIPAC-930030, PURD-TH-93-13, uses epsf.sty, 6 uuencoded
postscript figures, added one sentence and a referenc
Top-Down Approach to Unified Supergravity Models
We introduce a new approach for studying unified supergravity models. In this
approach all the parameters of the grand unified theory (GUT) are fixed by
imposing the corresponding number of low energy observables. This determines
the remaining particle spectrum whose dependence on the low energy observables
can now be investigated. We also include some SUSY threshold corrections that
have previously been neglected. In particular the SUSY threshold corrections to
the fermion masses can have a significant impact on the Yukawa coupling
unification.Comment: 19 pages, uuencoded compressed ps file, DESY 94-057 (paper format
corrected
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
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
The one-loop renormalization of the MSSM Higgs sector and its application to the neutral scalar Higgs masses
The structure of the Higgs sector in the minimal supersymmetric standard
model is reviewed at the one-loop level. An on-shell renormalization scheme of
the MSSM Higgs sector is presented in detail together with the complete list of
formulae for the neutral Higgs masses at the one-loop level. The results of a
complete one- loop calculation for the mass spectrum of the neutral MSSM Higgs
bosons and the quality of simpler Born-like approximations are discussed for
sfermion and gaugino masses in the range of the electroweak scale.Comment: 32 pages, report KA-THEP-5-199
Colliders and Cosmology
Dark matter in variations of constrained minimal supersymmetric standard
models will be discussed. Particular attention will be given to the comparison
between accelerator and direct detection constraints.Comment: Submitted for the SUSY07 proceedings, 15 pages, LaTex, 26 eps figure
Effects of the supersymmetric phases on the neutral Higgs sector
By using the effective potential approximation and taking into account the
dominant top quark and scalar top quark loops, radiative corrections to MSSM
Higgs potential are computed in the presence of the supersymmetric CP-violating
phases. It is found that, the lightest Higgs scalar remains essentially CP-even
as in the CP-invariant theory whereas the other two scalars are heavy and do
not have definite CP properties. The supersymmetric CP-violating phases are
shown to modify significantly the decay rates of the scalars to fermion pairs.Comment: 24 pp, 8 figs, 2 tables, typos and errors correcte
Additional phases induced by the supersymmetric CP phases
The explicit CP violation in the MSSM radiatively induces a finite
unremovable alignment between the Higgs doublets. This additinal phase can be
as large as the original CP phases in certain portions of the MSSM parameter
space. Considering the specific case of the charginos, this additional phase is
shown to induce a conceivable amount of CP violation near the would--be CP
conserving points. Moreover, the CP violation in the absence of this phase is
smaller than the one in the presence of it, and the former can never compete
with the latter, however large is.Comment: 29 pp, 15 fig
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