87 research outputs found
Effects of Curvature-Higgs Coupling on Electroweak Fine-Tuning
It is shown that, nonminimal coupling between the Standard Model (SM) Higgs
field and spacetime curvature, present already at the renormalizable level, can
be fine-tuned to stabilize the electroweak scale against power-law ultraviolet
divergences. The nonminimal coupling acts as an extrinsic stabilizer with no
effect on the loop structure of the SM, if gravity is classical. This novel
fine-tuning scheme, which could also be interpreted within Sakharov's induced
gravity approach, works neatly in extensions of the SM involving additional
Higgs fields or singlet scalars.Comment: 11 pp. Added reference
Dark Matter from Conformal Sectors
We show that a conformal-invariant dark sector, interacting conformally with
the Standard Model (SM) fields through the Higgs portal, provides a viable
framework where cold dark matter (CDM) and invisible Higgs decays can be
addressed concurrently. Conformal symmetry naturally subsumes the Z_2 symmetry
needed for stability of the CDM. It also guarantees that the weaker the
couplings of the dark sector fields to the SM Higgs field, the smaller the
masses they acquire through elektroweak breaking. The model comfortably
satisfies the bounds from Large Hadron Collider (LHC) and Planck Space
Telescope (Planck 2013).Comment: 9 pages, 3 figure
Weak-Scale Hidden Sector and Energy Transport in Fireball Models of Gamma-Ray Bursts
The annihilation of pairs of very weakly interacting particles in the
neibourghood of gamma-ray sources is introduced here as a plausible mechanism
to overcome the baryon load problem. This way we can explain how these very
high energy gamma-ray bursts can be powered at the onset of very energetic
events like supernovae (collapsars) explosions or coalescences of binary
neutron stars. Our approach uses the weak-scale hidden sector models in which
the Higgs sector of the standard model is extended to include a gauge singlet
that only interacts with the Higgs particle. These particles would be produced
either during the implosion of the red supergiant star core or at the aftermath
of a neutron star binary merger. The whole energetics and timescales of the
relativistic blast wave, the fireball, are reproduced.Comment: 4 pp, 1 ps fig, text revised and improve
Neutralino Dark Matter in the Left-Right Supersymmetric Model
We study the neutralino sector of the left-right supersymmetric model. In
addition to the possibilities available in the minimal supersymmetric model,
the neutralino states can be superpartners of the U(1)_{B-L} gauge boson, the
neutral SU(2)_R neutral gauge boson, or of the Higgs triplets. We analyze
neutralino masses and determine the parameter regions for which the lightest
neutralino can be one of the new pure states. We then calculate the relic
density of the dark matter for each of these states and impose the constraints
coming from the rho parameter, the anomalous magnetic moment of the muon, b ->
s gamma, as well as general supersymmetric mass bounds. The lightest neutralino
can be the bino, or the right-wino, or the neutral triplet higgsino, all of
which have different couplings to the standard model particles from the usual
neutralinos. A light bino satisfies all the experimental constraints and would
be the preferred dark matter candidate for light supersymmetric scalar masses,
while the right-wino would be favored by intermediate supersymmetric mass
scales. The neutral triplet Higgs fermion satisfies the experimental bounds
only in a small region of the parameter space, for intermediate to heavy
supersymmetric scalar masses.Comment: 31 pages, 8 figures, one table and references added, to be published
in Phys. Rev.
Squark Pair Production in the MSSM with Explicit CP Violation
We analyze effects of the CP-odd soft phases in the MSSM on the
pair-productions of colored superpartners in pp collisions at the LHC energies.
We find that, among all pair-production processes, those of the scalar quarks
in the first and second generations are particularly sensitive to the CP-odd
phases, more precisely, to the phases of the gluinos and neutralinos. We
compute pair-production cross sections, classify various production modes
according to their dependencies on the gluino and neutralino phases, perform a
detailed numerical analysis to determine individual as well as total cross
sections, and give a detailed discussion of EDM bounds. We find that
pair-productions of first and second generation squarks serve as a viable probe
of the CP violation sources in the gaugino sector of the theory even if
experiments cannot determine chirality, flavor and electric charge of the
squarks produced.Comment: 36 pp, 14 ps figures, 1 table, Corrected the cross sections; mild
changes in numerical results; conclusion unchange
Renormalization Group Invariants in the MSSM and Its Extensions
We derive one-loop renormalization group (RG) invariant observables and
analyze their phenomenological implications in the MSSM and its \mu problem
solving extensions, U(1)' model and NMSSM. We show that there exist several RG
invariants in the gauge, Yukawa and soft-breaking sectors of each model. In
general, RG invariants are highly useful for projecting experimental data to
messenger scale, for revealing correlations among the model parameters, and for
probing the mechanism that breaks supersymmetry. The Yukawa couplings and
trilinear soft terms in U(1)' model and NMSSM do not form RG invariants though
there exist approximate invariants in low tan(beta). In the NMSSM, there are no
invariants that contain the Higgs mass-squareds. We provide a comparative
analysis of RG invariants in all three models and analyze their model-building
and phenomenological implications by a number of case studies.Comment: 32 pages, 5 tables; extended previous analysis to include U(1)'
models and NMSSM where a comparative discussion is give
- …