181 research outputs found
Anomalous and Diboson Resonances at the LHC
We propose novel collider searches which can significantly improve the LHC
reach to new gauge bosons with mixed anomalies with the electroweak (EW)
gauge group. Such a necessarily acquires a Chern-Simons coupling to the EW
gauge bosons and these couplings can drive both exotic decays into
if the new gauge boson is sufficiently light, as well as decays
into EW gauge bosons.While the exotic decay rate of the heavy into
is too small to be observed at the LHC, for a light , we show
the potential of a lepton jet search in association with a photon to probe the
rare decay .Comment: 17 pages, 4 figures. v2: equation corrected, main results in Section
4 unchanged, accepted for publication in JHE
Signals of a Sneutrino (N)LSP at the LHC
The sneutrino is a viable candidate for the NLSP in SUSY spectra with
gravitino LSP. In this work we study the collider implications of this
possibility. In particular, we investigate whether the LHC can distinguish it
(at least, in some cases) from alternative spectra, such as those with a
neutralino LSP. We show that there exists a complete family of experimentally
allowed and theoretically motivated spectra with sneutrino NLSP, which exhibit
very distinctive multilepton signals that are difficult to fake within the
MSSM. We study these signals in detail, including the techniques necessary to
find them. We demonstrate our analysis approach on simulations incorporating
backgrounds.Comment: 41 pages, 13 figures. V2: Tau-tau background added and background
discussion in subsection V.C modified. Short discussion about early discovery
in subsection V.D added. Minors changes and refs. adde
Unbroken at a 100 TeV collider
A future 100 TeV pp collider will explore energies much higher than the scale
of electroweak (EW) symmetry breaking. In this paper we study some of the
phenomenological consequences of this fact, concentrating on enhanced
bremsstrahlung of EW gauge bosons. We survey a handful of possible new physics
experimental searches one can pursue at a 100 TeV collider using this
phenomenon. The most dramatic effect is the non-negligible radiation of EW
gauge bosons from neutrinos, making them partly visible objects. The presence
of collinear EW radiation allows for the full reconstruction of neutrinos under
certain circumstances. We also show that the presence of EW radiation allows
one to distinguish the quantum numbers of various new physics
particles. We consider examples of two completely different new physics
paradigms, additional gauge groups and SUSY, where the bremsstrahlung radiation
of and from s, s or stops allows one to determine the couplings
and the mixing angles of the new particles (respectively). Finally, we show how
the emission of s and s from high Higgs bosons can be used to test
the couplings of new physics to the Higgs boson.Comment: 27 pages, 10 figure
The Fraternal WIMP Miracle
We identify and analyze thermal dark matter candidates in the fraternal twin
Higgs model and its generalizations. The relic abundance of fraternal twin dark
matter is set by twin weak interactions, with a scale tightly tied to the weak
scale of the Standard Model by naturalness considerations. As such, the dark
matter candidates benefit from a "fraternal WIMP miracle," reproducing the
observed dark matter abundance for dark matter masses between 50 and 150 GeV.
However, the couplings dominantly responsible for dark matter annihilation do
not lead to interactions with the visible sector. The direct detection rate is
instead set via fermionic Higgs portal interactions, which are likewise
constrained by naturalness considerations but parametrically weaker than those
leading to dark matter annihilation. The predicted direct detection cross
section is close to current LUX bounds and presents an opportunity for the next
generation of direct detection experiments.Comment: 22 pages, 6 figures. v2: Relic abundance calculations revised and
improved, citations added. Conclusions largely unchanged. v3: Minor changes,
accepted by JCA
Higgs Couplings and Electroweak Phase Transition
We argue that extensions of the Standard Model (SM) with a strongly
first-order electroweak phase transition generically predict significant
deviations of the Higgs couplings to gluons, photons, and Z bosons from their
SM values. Precise experimental measurements of the Higgs couplings at the LHC
and at the proposed next-generation facilities will allow for a robust test of
the phase transition dynamics. To illustrate this point, in this paper we focus
on the scenario in which loops of a new scalar field are responsible for the
first-order phase transition, and study a selection of benchmark models with
various SM gauge quantum numbers of the new scalar. We find that the current
LHC measurement of the Higgs coupling to gluons already excludes the
possibility of a first-order phase transition induced by a scalar in a sextet,
or larger, representation of the SU(3)_c. Future LHC experiments (including
HL-LHC) will be able to definitively probe the case when the new scalar is a
color triplet. If the new scalar is not colored, an electron-positron Higgs
factory, such as the proposed ILC or TLEP, would be required to test the nature
of the phase transition. The extremely precise measurement of the
Higgsstrahlung cross section possible at such machines will allow for a
comprehensive and definitive probe of the possibility of a first-order
electroweak phase transition in all models we considered, including the case
when the new scalar is a pure gauge singlet.Comment: 27 pages, 6 figures. v2: typos fixed, some clarifications added,
results and conclusions unchange
Lorentz Violation and Superpartner Masses
We consider Lorentz violation in supersymmetric extensions of the standard
model. We perform a spurion analysis to show that, in the simplest natural
constructions, the resulting supersymmetry-breaking masses are tiny. In the
process, we argue that one of the strongest bounds on Lorentz violation in the
photon Lagrangian, which comes from the absence of birefringence from distant
astrophysical sources, does not apply when Lorentz violation is parametrized by
a single vector.Comment: 13 pages. v3: some comments and a short appendix added to elaborate
on the relation between LV and SUSY breakin
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