54 research outputs found
Effects of quantum statistics on relic density of Dark Radiation
The freeze-out of massless particles is investigated. The effects due to
quantum statistics, Fermi-Dirac or Bose-Einstein, of all particles relevant for
the process are analyzed. Solutions of appropriate Boltzmann equation are
compared with those obtained using some popular approximate methods. As an
application of general results the relic density of dark radiation in
Weinberg's Higgs portal model is discussed.Comment: 19 pages, 4 figure
Light staus and enhanced Higgs diphoton rate with non-universal gaugino masses and SO(10) Yukawa unification
It is shown that substantially enhanced Higgs to diphoton rate induced by
light staus with large left-right mixing in MSSM requires at the GUT scale
non-universal gaugino masses with bino and/or wino lighter than gluino. The
possibility of such enhancement is investigated in MSSM models with arbitrary
gaugino masses at the GUT scale with additional restriction of top-bottom-tau
Yukawa unification, as predicted by minimal SO(10) GUTs. Many patterns of
gaugino masses leading to enhanced Higgs to diphoton rate and the Yukawa
unification are identified. Some of these patterns can be accommodated in a
well-motivated scenarios such as mirage mediation or SUSY breaking F-terms
being a non-singlet of SO(10). Phenomenological implications of a scenario with
non-universal gaugino masses generated by a mixture of the singlet F-term and
the F-term in a 24-dimensional representation of SU(5) SO(10) are
studied in detail. Possible non-universalities of other soft terms generated by
such F-terms are discussed. The enhancement of Higgs to diphoton rate up to 30%
can be obtained in agreement with all phenomenological constraints, including
vacuum metastability bounds. The lightest sbottom and pseudoscalar Higgs are
within easy reach of the 14 TeV LHC. The LSP can be either bino-like or
wino-like. The thermal relic abundance in the former case may be in agreement
with the cosmological data thanks to efficient stau coannihilation.Comment: 28 pages, 8 figures, comments and references added, matches published
versio
Spin-dependent constraints on blind spots for thermal singlino-higgsino dark matter with(out) light singlets
The LUX experiment has recently set very strong constraints on
spin-independent interactions of WIMP with nuclei. These null results can be
accommodated in NMSSM provided that the effective spin-independent coupling of
the LSP to nucleons is suppressed. We investigate thermal relic abundance of
singlino-higgsino LSP in these so-called spin-independent blind spots and
derive current constraints and prospects for direct detection of spin-dependent
interactions of the LSP with nuclei providing strong constraints on parameter
space. We show that if the Higgs boson is the only light scalar the new LUX
constraints set a lower bound on the LSP mass of about 300 GeV except for a
small range around the half of boson masses where resonant annihilation
via exchange dominates. XENON1T will probe entire range of LSP masses
except for a tiny -resonant region that may be tested by the LZ
experiment. These conclusions apply to general singlet-doublet dark matter
annihilating dominantly to . Presence of light singlet
(pseudo)scalars generically relaxes the constraints because new LSP (resonant
and non-resonant) annihilation channels become important. Even away from
resonant regions, the lower limit on the LSP mass from LUX is relaxed to about
250 GeV while XENON1T may not be sensitive to the LSP masses above about 400
GeV.Comment: 31 pages, 8 figure
New Regions in the NMSSM with a 125 GeV Higgs
It is pointed out that mixing effects in the CP-even scalar sector of the
NMSSM can give 6-8 GeV correction to the SM-like Higgs mass in moderate or
large regions with a small value of the singlet-higgs-higgs
superfields coupling . This effect comes mainly
from the mixing of the SM-like Higgs with lighter singlet. In the same
parameter range, the mixing of the heavy doublet Higgs with the singlet may
strongly modify the couplings of the singlet-like and the 125 GeV scalars.
Firstly, the LEP bounds on a light singlet can be evaded for a large range of
its masses. Secondly, the decay rates of both scalars can show a variety of
interesting patterns, depending on the lightest scalar mass. In particular, a
striking signature of this mechanism can be a light scalar with strongly
suppressed (enhanced) branching ratios to (, ,
) as compared to the SM Higgs with the same mass. The
decay channel is particularly promising for the search of such a
scalar at the LHC. The 125 GeV scalar can, thus, be accommodated with
substantially smaller than in the MSSM radiative corrections from the stop
loops (and consequently, with lighter stops) also for moderate or large
, with the mixing effects replacing the standard NMSSM mechanism of
increasing the tree level Higgs mass in the low and large
regime, and with clear experimental signatures of such a mechanism.Comment: 19 pages, 5 figures, references added, version to be publishe
Upper bounds on sparticle masses from muon g-2 and the Higgs mass and the complementarity of future colliders
Supersymmetric (SUSY) explanation of the discrepancy between the measurement
of and its SM prediction puts strong upper bounds on the chargino
and smuon masses. At the same time, lower experimental limits on the chargino
and smuon masses, combined with the Higgs mass measurement, lead to an upper
bound on the stop masses. The current LHC limits on the chargino and smuon
masses (for not too compressed spectrum) set the upper bound on the stop masses
of about 10 TeV. The discovery potential of the future lepton and hadron
colliders should lead to the discovery of SUSY if it is responsible for the
explanation of the anomaly. This conclusion follows from the fact
that the upper bound on the stop masses decreases with the increase of the
lower experimental limit on the chargino and smuon masses.Comment: 14 pages, 4 figures; v2: fig.2, comments and references added,
matches published versio
Towards supersymmetric cosmology in M theory
We present a new solution in the heterotic M-theory in which the metric
depends on (cosmic) time. The solution preserves N=1 supersymmetry in 4
dimensions in the leading order of the expansion. It is the
first example of the time-dependent supersymmetric solution in M-theory on
. It describes expanding 4-dimensional space-time with shrinking
orientifold interval and static Calabi-Yau internal space.Comment: latex, 12 page
Soft Supersymmetry Breaking in KKLT Flux Compactification
We examine the structure of soft supersymmetry breaking terms in KKLT models
of flux compactification with low energy supersymmetry. Moduli are stabilized
by fluxes and nonperturbative dynamics while a de Sitter vacuum is obtained by
adding supersymmetry breaking anti-branes. We discuss the characteristic
pattern of mass scales in such a set-up as well as some features of 4D N=1
supergravity breakdown by anti-branes. Anomaly mediation is found to always
give an important contribution and one can easily arrange for
flavor-independent soft terms. In its most attractive realization, the modulus
mediation is comparable to the anomaly mediation, yielding a quite distinctive
sparticle spectrum. In addition, the axion component of the modulus/dilaton
superfield dynamically cancels the relative CP phase between the contributions
of anomaly and modulus mediation, thereby avoiding dangerous SUSY CP violation.Comment: minor corrections, references added, version accepted in NP
Deconstructing 5D supersymmetric U(1) gauge theories on orbifolds
We investigate deconstruction of five dimensional supersymmetric abelian
gauge theories compactified on , with various sets of bulk and matter
multiplets. The problem of anomalies, chirality and stability in the
deconstructed theories is discussed. We find that for most of the 5d brane/bulk
matter assignments there exists the deconstructed version. There are, however,
some exceptions.Comment: Discussion of mixed anomalies and some clarifying commments added.
Version to appear in Phys.Lett.
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