2,748 research outputs found
Blind Spots for neutralino Dark Matter in the MSSM with an intermediate m_A
We study the spin-independent neutralino Dark Matter scattering off heavy
nuclei in the MSSM. We identify analytically the blind spots in direct
detection for intermediate values of . In the region where and
have opposite signs, there is not only a reduction of the lightest
CP-even Higgs coupling to neutralinos, but also a destructive interference
between the neutralino scattering through the exchange of the lightest CP-even
Higgs and that through the exchange of the heaviest CP-even Higgs. At critical
values of , the tree-level contribution from the light Higgs exchange
cancels the contribution from the heavy Higgs, so the scattering cross section
vanishes. We denote these configurations as blind spots, since they provide a
generalization of the ones previously discussed in the literature, which occur
at very large values of . We show that the generalized blind spots may
occur in regions of parameter space that are consistent with the obtention of
the proper neutralino relic density, and can be tested by non-standard Higgs
boson searches and EWino searches at the LHC and future linear colliders.Comment: 25pages, 7 figures, v2:references and one paragraph added, v3:
discussion about collider searches added, accepted by PR
Enhancing the Higgs associated production with a top quark pair
It is pointed out that in a wide class of models reminiscent of type-II
Two-Higgs-Doublet Models (2HDM) the signal of the Higgs produced in association
with a top-antitop quark pair () and decaying into gauge bosons can be
significantly larger than the Standard Model (SM) prediction without violating
any experimental constraints. The crucial feature of these models is enhanced
(suppressed) Higgs coupling to top (bottom) quarks and existence of light
colored particles that give negative contribution to the effective Higgs
coupling to gluons resulting in the gluon fusion rates in the gauge boson decay
channels close to SM predictions. We demonstrate this mechanism in NMSSM with
light stops and show that signal in the decay channel can be two
times larger than the SM prediction, as suggested by the excesses observed by
ATLAS and CMS, provided that the Higgs-singlet superpotential coupling
and the MSSM-like Higgs boson masses are in the range of
160 to 300 GeV.Comment: 19 pages, 4 figures; v2:comments and references added, matches
published versio
CP-odd component of the lightest neutral Higgs boson in the MSSM
The Higgs sector of the Minimal Supersymmetric Extension of the Standard
Model may be described with a two Higgs doublet model with properties that
depend on the soft supersymmetry breaking parameters. For instance, flavor
independent CP-violating phases associated with the gaugino masses, the squark
trilinear mass parameters and the Higgsino mass parameter may lead to
sizable CP-violation in the Higgs sector. For these CP-violating effects to
affect the properties of the recently observed SM-like Higgs resonance, the
non-standard charged and neutral Higgs bosons masses must be of the order of
the weak scale, and both as well as the trilinear stop mass parameter
must be of the order or larger than the stop mass parameters. Constraints
on this possibility come from direct searches for non-standard Higgs bosons,
precision measurements on the lightest neutral Higgs properties, including its
mass, and electric dipole moments. In this article, we discuss these
constraints within the MSSM, trying to evaluate the possible size of the CP-odd
component of the lightest neutral Higgs boson, and the possible experimental
tests of this CP-violating effect at the LHC.Comment: 35 pages, 13 figure
Modification of Higgs Couplings in Minimal Composite Models
We present a comprehensive study of the modifications of Higgs couplings in
the SO(5)/SO(4) minimal composite model. We focus on three couplings of central
importance to Higgs phenomenology at the LHC: the couplings to top and bottom
quarks and the coupling to two gluons. We consider three possible embeddings of
the fermionic partners in 5, 10 and 14 of SO(5) and find tth and bbh couplings
to be always suppressed in 5 and 10, while in 14 they can be either enhanced or
suppressed. Assuming partial compositeness, we analyze the interplay between
the tth coupling and the top sector contribution to the Coleman-Weinberg
potential for the Higgs boson, and the correlation between tth and ggh
couplings. In particular, if the electroweak symmetry breaking is triggered
radiatively by the top sector, we demonstrate that the ratio of the tth
coupling in composite Higgs models over the Standard Model expectation is
preferred to be less than the corresponding ratio of the ggh coupling.Comment: 42 pages, 14 figures; Added reference
Precise Estimates of the Higgs Mass in Heavy SUSY
In supersymmetric models, very heavy stop squarks introduce large logarithms
into the computation of the Higgs boson mass. Although it has long been known
that in simple cases these logs can be resummed using effective field theory
techniques, it is technically easier to use fixed-order formulas, and many
public codes implement the latter. We calculate three- and four-loop
next-to-next-to-leading-log corrections to the Higgs mass and compare the fixed
order formulas numerically to the resummation results in order to estimate the
range of supersymmetry scales where the fixed-order results are reliable. We
find that the four-loop result may be accurate up to a few tens of TeV. We
confirm an accidental cancellation between different three-loop terms, first
observed in S. P. Martin, Phys. Rev. D 75, 055005 (2007), and show that it
persists to higher scales and becomes more effective with the inclusion of
higher radiative corrections. Existing partial three-loop calculations that
include only one of the two cancelling terms may overestimate the Higgs mass.
We give analytic expressions for the three- and four-loop corrections in terms
of Standard Model parameters and provide a complete dictionary for translating
parameters between the SM and the MSSM and the \MSbar and \DRbar
renormalization schemes.Comment: 34 pages, 6 figures. Added acknowledgments in v2. Corrected typos
from published version in PRD in v
Prospects for Higgs Searches at the Tevatron and LHC in the MSSM with Explicit CP-violation
We analyze the Tevatron and Large Hadron Collider (LHC) reach for the Higgs
sector of the Minimal Supersymmetric Standard Model (MSSM) in the presence of
explicit CP-violation. Using the most recent studies from the Tevatron and LHC
collaborations, we examine the CPX benchmark scenario for a range of
CP-violating phases in the soft trilinear and gluino mass terms and compute the
exclusion/discovery potentials for each collider on the
plane. Projected results from Standard Model (SM)-like, non-standard, and
charged Higgs searches are combined to maximize the statistical significance.
We exhibit complementarity between the SM-like Higgs searches at the LHC with
low luminosity and the Tevatron, and estimate the combined reach of the two
colliders in the early phase of LHC running.Comment: 38 pages, 9 figures; References added, minor additions to Appendix
Very Light Charginos and Higgs Decays
We explore modifications to the loop-induced Higgs couplings h\gamma\gamma\
and h\gamma Z from light charginos in the Minimal Supersymmetric Standard
Model. When the lightest chargino mass is above the naive LEP bound of order
100 GeV the effects are modest, with deviations in the decay branching ratios
typically less than 15% from the Standard Model predictions. However, if the
charginos are lighter than 100 GeV, more dramatic alterations to these
couplings are possible as a consequence of the rise of the one loop form
factor. For example, the diphoton signal strength can be enhanced by as much as
70% compared to the Standard Model value. We scrutinize in detail the existing
LEP, Tevatron, and LHC searches and present a scenario in which a very light
chargino with a mass as light as half the Higgs mass is hidden at LEP and is
allowed by all direct collider constraints and electroweak precision tests. The
scenario has a sneutrino LSP with a macroscopic decay length of order 10-100
cm. We outline potential search strategies to test this scenario at the LHC.Comment: 14 pages, 7 figure
Bounding the Charm Yukawa
The study of the properties of the observed Higgs boson is one of the main
research activities in High Energy Physics. Although the couplings of the Higgs
to the weak gauge bosons and third generation quark and leptons have been
studied in detail, little is known about the Higgs couplings to first and
second generation fermions. In this article, we study the charm quark Higgs
coupling in the so-called framework. We emphasize the existence of
specific correlations between the Higgs couplings that can render the measured
LHC Higgs production rates close to the SM values in the presence of large
deviations of the charm coupling from its SM value, . Based on
this knowledge, we update the indirect bounds on through a fit to
the precision Higgs measurements at the LHC. We also examine the limits on
arising from the radiative decay , the charm
quark-associated Higgs production, charm quark decays of the Higgs field and
charge asymmetry in production. Estimates for the future LHC
sensitivity on at the high luminosity run are provided.Comment: Version published in Phys. Rev.
Prospects for MSSM Higgs Searches at the Tevatron
We analyze the Tevatron reach for neutral Higgs bosons in the Minimal
Supersymmetric Standard Model (MSSM), using current exclusion limits on the
Standard Model Higgs. We study four common benchmark scenarios for the soft
supersymmetry-breaking parameters of the MSSM, including cases where the Higgs
decays differ significantly from the Standard Model, and provide projections
for the improvements in luminosity and efficiency required for the Tevatron to
probe sizeable regions of the plane.Comment: 23 pages, 21 figures; References added, benchmark scenarios and
figures updated, webpage link adde
Baryogenesis from an Earlier Phase Transition
We explore the possibility that the observed baryon asymmetry of the universe
is the result of an earlier phase transition in which an extended gauge sector
breaks down into the of the Standard
Model. Our proto-typical example is the Topflavor model, in which there is a
separate for the third generation from the felt by the
first two generations. We show that the breakdown of results in lepton number being asymmetrically distributed
through-out the three families, and provided the SM electroweak phase
transition is {\em not} strongly first order, results in a non-zero baryon
number, which for parameter choices that can be explored at the LHC, may
explain the observed baryon asymmetry.Comment: 25 pages, 6 figures, submitted to PR
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