454 research outputs found
Higgs portal dark matter and neutrino mass and mixing with a doubly charged scalar
We consider an extension of the Standard Model involving two new scalar
particles around the TeV scale: a singlet neutral scalar , to be
eventually identified as the Dark Matter candidate, plus a doubly charged
singlet scalar, , that can be the source for the
non-vanishing neutrino masses and mixings. Assuming an unbroken symmetry
in the scalar sector, under which only the additional neutral scalar is
odd, we write the most general (renormalizable) scalar potential. The model may
be regarded as a possible extension of the conventional Higgs portal Dark
Matter scenario which also accounts for neutrino mass and mixing. This
framework cannot completely explain the observed positron excess. However a
softening of the discrepancy observed in conventional Higgs portal framework
can be obtained, especially when the scale of new physics responsible for
generating neutrino masses and lepton number violating processes is around 2
TeV.Comment: 16 pages, 4 figure
CP violation with a dynamical Higgs
We determine the complete set of independent gauge and gauge-Higgs CP-odd
effective operators for the generic case of a dynamical Higgs, up to four
derivatives in the chiral expansion. The relation with the linear basis of
dimension six CP-odd operators is clarified. Phenomenological applications
include bounds inferred from electric dipole moment limits, and from present
and future collider data on triple gauge coupling measurements and Higgs
signals.Comment: 41 pages, 3 figures; V2: citations added, typos corrected, version
published on JHE
Quantum channels in random spin chains
We study the entanglement between pairs of qubits in a random
antiferromagnetic spin-1/2 chain at zero temperature. We show that some very
distant pairs of qubits are highly entangled, being almost pure Bell states.
Furthermore, the probability to obtain such spin pairs is proportional to the
chain disorder strenght and inversely proportional to the square of their
separation.Comment: v1: 4 pages, 2 eps figures; v2: discussion about the effect of
temperature added, v3: 1 eps figure added, enlarged discussions, 6 pages,
published versio
Higgs ultraviolet softening
We analyze the leading effective operators which induce a quartic momentum
dependence in the Higgs propagator, for a linear and for a non-linear
realization of electroweak symmetry breaking. Their specific study is relevant
for the understanding of the ultraviolet sensitivity to new physics. Two
methods of analysis are applied, trading the Lagrangian coupling by: i) a
"ghost" scalar, after the Lee-Wick procedure; ii) other effective operators via
the equations of motion. The two paths are shown to lead to the same effective
Lagrangian at first order in the operator coefficients. It follows a
modification of the Higgs potential and of the fermionic couplings in the
linear realization, while in the non-linear one anomalous quartic gauge
couplings, Higgs-gauge couplings and gauge-fermion interactions are induced in
addition. Finally, all LHC Higgs and other data presently available are used to
constrain the operator coefficients; the future impact of data via off-shell Higgs exchange and of vector boson fusion data is
considered as well. For completeness, a summary of pure-gauge and gauge-Higgs
signals exclusive to non-linear dynamics at leading-order is included.Comment: 31 pages, 3 figures, 7 table
Decoupling Properties of MSSM particles in Higgs and Top Decays
We study the supersymmetric (SUSY) QCD radiative corrections, at the one-loop
level, to , and t quark decays, in the context of the Minimal
Supersymmetric Standard Model (MSSM) and in the decoupling limit. The
decoupling behaviour of the various MSSM sectors is analyzed in some special
cases, where some or all of the SUSY mass parameters become large as compared
to the electroweak scale. We show that in the decoupling limit of both large
SUSY mass parameters and large CP-odd Higgs mass, the decay width approaches its Standard Model value at one loop, with the onset
of decoupling being delayed for large values. However, this
decoupling does not occur if just the SUSY mass parameters are taken large. A
similar interesting non-decoupling behaviour, also enhanced by , is
found in the SUSY-QCD corrections to the decay width
at one loop. In contrast, the SUSY-QCD corrections in the
decay width do decouple and this decoupling is fast.Comment: 19 pages, 10 figures. Invited talk presented by M.J.Herrero at the
5th International Symposium on Radiative Corrections (RADCOR 2000) Carmel CA,
USA, 11-15 September, 200
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