1,066 research outputs found
Virtual signatures of dark sectors in Higgs couplings
Where collider searches for resonant invisible particles loose steam, dark
sectors might leave their trace as virtual effects in precision observables.
Here we explore this option in the framework of Higgs portal models, where a
sector of dark fermions interacts with the standard model through a strong
renormalizable coupling to the Higgs boson. We show that precise measurements
of Higgs-gauge and triple Higgs interactions can probe dark fermions up to the
TeV scale through virtual corrections. Observation prospects at the LHC and
future lepton colliders are discussed for the so-called singlet-doublet model
of Majorana fermions, a generalization of the bino-higgsino scenario in
supersymmetry. We advocate a two-fold search strategy for dark sectors through
direct and indirect observables.Comment: 20 pages, 7 figures, 1 tabl
The Spectrum of Goldstini and Modulini
When supersymmetry is broken in multiple sectors via independent dynamics,
the theory furnishes a corresponding multiplicity of "goldstini" degrees of
freedom which may play a substantial role in collider phenomenology and
cosmology. In this paper, we explore the tree-level mass spectrum of goldstini
arising from a general admixture of F-term, D-term, and almost no-scale
supersymmetry breaking, employing non-linear superfields and a novel gauge
fixing for supergravity discussed in a companion paper. In theories of F-term
and D-term breaking, goldstini acquire a mass which is precisely twice the
gravitino mass, while the inclusion of no-scale breaking renders one of these
modes, the modulino, massless. We argue that the vanishing modulino mass can be
explained in terms of an accidental and spontaneously broken "global"
supersymmetry.Comment: 10 pages, 2 figures; v2: typo corrected, references updated; v3:
version to appear in JHE
Asymmetric Origin for Gravitino Relic Density in the Hybrid Gravity-Gauge Mediated Supersymmetry Breaking
We propose the hybrid gravity-gauge mediated supersymmetry breaking where the
gravitino mass is about several GeV. The strong constraints on supersymmetry
viable parameter space from the CMS and ATLAS experiments at the LHC can be
relaxed due to the heavy colored supersymmetric particles, and it is consistent
with null results in the dark matter (DM) direct search experiments such as
XENON100. In particular, the possible maximal flavor and CP violations from the
relatively small gravity mediation may naturally account for the recent LHCb
anomaly. In addition, because the gravitino mass is around the asymmetric DM
mass, we propose the asymmetric origin of the gravitino relic density and solve
the cosmological coincident problem on the DM and baryon densities \Omega_{\rm
DM}:\Omega_{B}\approx 5:1. The gravitino relic density arises from asymmetric
metastable particle (AMP) late decay. However, we show that there is no AMP
candidate in the minimal supersymmetric Standard Model (SM) due to the robust
gaugino/Higgsino mediated wash-out effects. Interestingly, AMP can be realized
in the well motivated supersymmetric SMs with vector-like particles or
continuous U(1)_R symmetry. Especially, the lightest CP-even Higgs boson mass
can be lifted in the supersymmetric SMs with vector-like particles.Comment: RevTex4, 21 pages, 1 figure, minor corrections, JHEP versio
The Two Faces of Anomaly Mediation
Anomaly mediation is a ubiquitous source of supersymmetry (SUSY) breaking
which appears in almost every theory of supergravity. In this paper, we show
that anomaly mediation really consists of two physically distinct phenomena,
which we dub "gravitino mediation" and "Kahler mediation". Gravitino mediation
arises from minimally uplifting SUSY anti-de Sitter (AdS) space to Minkowski
space, generating soft masses proportional to the gravitino mass. Kahler
mediation arises when visible sector fields have linear couplings to SUSY
breaking in the Kahler potential, generating soft masses proportional to beta
function coefficients. In the literature, these two phenomena are lumped
together under the name "anomaly mediation", but here we demonstrate that they
can be physically disentangled by measuring associated couplings to the
goldstino. In particular, we use the example of gaugino soft masses to show
that gravitino mediation generates soft masses without corresponding goldstino
couplings. This result naively violates the goldstino equivalence theorem but
is in fact necessary for supercurrent conservation in AdS space. Since
gravitino mediation persists even when the visible sector is sequestered from
SUSY breaking, we can use the absence of goldstino couplings as an unambiguous
definition of sequestering.Comment: 21 pages, 1 table; v2, references added, extended discussion in
introduction and appendix; v3, JHEP versio
Measurement of the cross-section and charge asymmetry of bosons produced in proton-proton collisions at TeV with the ATLAS detector
This paper presents measurements of the and cross-sections and the associated charge asymmetry as a
function of the absolute pseudorapidity of the decay muon. The data were
collected in proton--proton collisions at a centre-of-mass energy of 8 TeV with
the ATLAS experiment at the LHC and correspond to a total integrated luminosity
of 20.2~\mbox{fb^{-1}}. The precision of the cross-section measurements
varies between 0.8% to 1.5% as a function of the pseudorapidity, excluding the
1.9% uncertainty on the integrated luminosity. The charge asymmetry is measured
with an uncertainty between 0.002 and 0.003. The results are compared with
predictions based on next-to-next-to-leading-order calculations with various
parton distribution functions and have the sensitivity to discriminate between
them.Comment: 38 pages in total, author list starting page 22, 5 figures, 4 tables,
submitted to EPJC. All figures including auxiliary figures are available at
https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/STDM-2017-13
Electroweak Precision Constraints on Vector-like Fermions
We calculate the oblique electroweak corrections and confront with the
experiments in an extension of the Standard Model. The new fields added are a
vector-like weak doublet and a singlet fermion. After electroweak symmetry
breaking there is a mixing between the components of the new fields, but no
mixing allowed with the standard fermions. Four electroweak parameters,
, , W, Y are presented in the formalism of Barbieri et al.,
these are the generalization of the Peskin-Takeuchi S, T, U's. The vector-like
extension is slightly constrained, requires the new neutral fermion
masses not to be very far from each other, allowing higher mass difference for
higher masses and smaller mixing. gives practically no
constraints on the masses. This extension can give a positive contribution to
, allowing a heavy Higgs boson in electroweak precision tests of the
Standard Model.Comment: 11 pages, 3 figures, references added,sign correction, conclusion
about heavy Higgs has change
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