5,006 research outputs found
The breaking of the symmetry: The 750 GeV resonance at the LHC and perturbative unitarity
If the di-photon excess at 750 GeV hinted by the 2015 data at the LHC is
explained in terms of a scalar resonance participating in the breaking of the
electro-weak symmetry, this resonance must be accompanied by other scalar
states for perturbative unitarity in vector boson scattering to be preserved.
The simplest set-up consistent with perturbative unitarity and with the data of
the di-photon excess is the Georgi-Machacek model.Comment: 9 pages, 5 figures. v2: Minor changes, bibliography updated. v3:
Minor change
Natural minimal dark matter
We show how the Higgs boson mass is protected from the potentially large
corrections due to the introduction of minimal dark matter if the new physics
sector is made supersymmetric. The fermionic dark matter candidate (a 5-plet of
) is accompanied by a scalar state. The weak gauge sector is made
supersymmetric and the Higgs boson is embedded in a supersymmetric multiplet.
The remaining standard model states are non-supersymmetric. Non vanishing
corrections to the Higgs boson mass only appear at three-loop level and the
model is natural for dark matter masses up to 15 TeV--a value larger than the
one required by the cosmological relic density. The construction presented
stands as an example of a general approach to naturalness that solves the
little hierarchy problem which arises when new physics is added beyond the
standard model at an energy scale around 10 TeV.Comment: 6 pages, 4 figures. v2: Discussion on the mass splitting extended and
improved. References adde
Finite-time blowup and existence of global positive solutions of a semi-linear SPDE
We consider stochastic equations of the prototype on a smooth domain , with Dirichlet boundary condition, where
, are positive constants and , is a
one-dimensional standard Wiener process. We estimate the probability of finite
time blowup of positive solutions, as well as the probability of existence of
non-trivial positive global solutions
Antiproton constraints on the GeV gamma-ray excess: a comprehensive analysis
A GeV gamma-ray excess has possibly been individuated in Fermi-LAT data from
the Galactic Center and interpreted in terms of Dark Matter (DM) annihilations,
either in hadronic (essentially ) or leptonic channels. In order to
test this tantalizing interpretation, we address two issues: (i) we improve the
computation of secondary emission from DM (Inverse Compton and Bremsstrahlung)
with respect to previous works, confirming it to be very relevant for
determining the DM spectrum in the leptonic channels, so that any conclusion on
the DM nature of the signal critically depends on this contribution; (ii) we
consider the constraints from antiprotons on the DM hadronic channel, finding
that the uncertainties on the propagation model, and in particular on the halo
height, play a major role. Moreover, we discuss the role of solar modulation,
taking into account possible charge dependent effects whose importance is
estimated exploiting detailed numerical tools. The limits that we obtain
severely constrain the DM interpretation of the excess in the hadronic channel,
for standard assumptions on the Galactic propagation parameters and solar
modulation. However, they considerably relax if more conservative choices are
adopted.Comment: 22 pages, 6 figures, 2 table
Mixing-induced Spontaneous Supersymmetry Breaking
It is conjectured that flavor mixing furnishes a universal mechanism for the
spontaneous breaking of supersymmetry. The conjecture is proved explicitly for
the mixing of two Wess--Zumino supermultiplets and arguments
for its general validity are given. The mechanism relies on the fact that,
despite mixing treats fermions and bosons symmetrically, both the fermionic and
the bosonic zero point energies are shifted by a positive amount and this kind
of shift does not respect supersymmetry.Comment: 5 pages, 1 figure, Eq(12) of V1 corrected to Eq(22), explicit
off-shell formulation included, one reference adde
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