76 research outputs found
Neutralino Dark Matter in Gauge Mediation After Run I of LHC and LUX
Neutralino can be the dark matter candidate in the gauge-mediated
supersymmetry breaking models if the conformal sequestered mechanism is assumed
in the hidden sector. In this paper, we study this mechanism by using the
current experimental results after the run I of LHC and LUX. By adding new
Yukawa couplings between the messenger fields and Higgs fields, we find that
this mechanism can predict a neutralino dark matter with correct relic density
and a Higgs boson with mass around 125 GeV. All our survived points have some
common features. Firstly, the Higgs sector falls into the decoupling limit. So
the properties of the light Higgs boson are similar to the predictions of the
Standard Model one. Secondly, the correct EWSB hints a relatively small
-term, which makes the lightest neutralino lighter than the lightest stau.
So a bino-higgsino dark matter with correct relic density can be achieved. And
the relatively small -term results in a small fine-tuning. Finally, this
bino-higgsino dark matter can pass all current bounds, including both
spin-independent and spin-dependent direct searches. The spin-independent cross
section of our points can be examined by further experiments.Comment: Minor changes, version to appear in Phys. Lett.
Towards the Natural Gauge Mediation
The sweet spot supersymmetry (SUSY) solves the mu problem in the Minimal
Supersymmetric Standard Model (MSSM) with gauge mediated SUSY breaking (GMSB)
via the generalized Giudice-Masiero (GM) mechanism where only the mu-term and
soft Higgs masses are generated at the unification scale of the Grand Unified
Theory (GUT) due to the approximate PQ symmetry. Because all the other SUSY
breaking soft terms are generated via the GMSB below the GUT scale, there
exists SUSY electroweak (EW) fine-tuning problem to explain the 125 GeV Higgs
boson mass due to small trilinear soft term. Thus, to explain the Higgs boson
mass, we propose the GMSB with both the generalized GM mechanism and
Higgs-messenger interactions. The renormalization group equations are runnings
from the GUT scale down to EW scale. So the EW symmetry breaking can be
realized easier. We can keep the gauge coupling unification and solution to the
flavor problem in the GMSB, as well as solve the \mu/B_{\mu}-problem. Moreover,
there are only five free parameters in our model. So we can determine the
characteristic low energy spectra and explore its distinct phenomenology. The
low-scale fine-tuning measure can be as low as 20 with the light stop mass
below 1 TeV and gluino mass below 2 TeV. The gravitino dark matter can come
from a thermal production with the correct relic density and be consistent with
the thermal leptogenesis. Because gluino and stop can be relatively light in
our model, how to search for such GMSB at the upcoming run II of the LHC
experiment could be very interesting.Comment: 22 pages, 7 figures, Late
Revisit to Non-decoupling MSSM
Dipole operator requires the helicity
flip in the involving quark states thus the breaking of chiral . On the other hand, the -quark mass generation is also a
consequence of chiral symmetry breaking. Therefore,
in many models, there might be strong correlation between the
and quark Yukawa coupling. We use non-decoupling MSSM model to illustrate
this feature. The light Higgs boson may evade the direct search experiments at
LEPII or Tevatron while the 125 GeV Higgs-like boson is identified as the heavy
Higgs boson in the spectrum. A light charged Higgs is close to the heavy Higgs
boson which is of 125 GeV and its contribution to requires
large supersymmetric correction with large PQ and symmetry breaking. The
large supersymmetric contribution at the same time significantly modifies the
quark Yukawa co upling. With combined flavor constraints
and and direct constraints on Higgs properties, we
find best fit scenarios with light stop of (500 GeV), negative
around -750 GeV and large -term of 2-3 TeV. In addition, reduction in
partial width may also result in large enhancement of
decay branching fraction. Large parameter region in the survival space under
all bounds may be further constrained by if no excess of
is confirmed at LHC. We only identify a small parameter region with
significant decay that is consistent with all bounds and reduced
decay branching fraction.Comment: 18pages, 6 figure
Gamma-rays from Nearby Clusters: Constraints on Selected Decaying Dark Matter Models
Recently, the Fermi-LAT collaboration reported upper limits on the GeV
gamma-ray flux from nearby clusters of galaxies. Motivated by these limits, we
study corresponding constraints on gamma-ray emissions from two specific
decaying dark matter models, one via grand unification scale suppressed
operators and the other via R-parity violating operators. Both can account for
the PAMELA and Fermi-LAT excesses of e^\pm. For GUT decaying dark matter, the
gamma-rays from the M49 and Fornax clusters, with energy in the range of 1 to
10 GeV, lead to the most stringent constraints to date. As a result, this dark
matter is disfavored with conventional model of e^\pm background. In addition,
it is likely that some tension exists between the Fermi-LAT e^\pm excess and
the gamma ray constraints for any decaying dark matter model, provided
conventional model of e^\pm background is adopted. Nevertheless, the GUT
decaying dark matter can still solely account for the PAMELA positron fraction
excess without violating the gamma-ray constraints. For the gravitino dark
matter model with R-parity violation, cluster observations do not give tight
constraints. This is because a different e^\pm background has been adopted
which leads to relatively light dark matter mass around 200 GeV.Comment: 17 pages, 4 figures, version to appear in Phys. Lett.
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