55 research outputs found
Electroweak precision measurements in supersymmetric models with a U(1)R lepton number
As experimental constraints on the parameter space of the MSSM and close
variations thereof become stronger, the motivation to explore supersymmetric
models that challenge some of the standard assumptions of the MSSM also become
stronger. For example, models where the gauginos are Dirac instead of Majorana
have recently received more attention. Beside allowing for a supersoft SUSY
breaking mechanism where the gauginos only provide finite threshold corrections
to scalar masses, the cross section for the production of a squark pairs is
reduced. In addition, Dirac gauginos can be used to build models that possess a
U(1)R symmetry. This symmetry can then be identified with a lepton number,
leading to models that are quite different from conventional scenarios. The
sneutrinos in these models can acquire a vev and give mass to the leptons and
the down-type squark. The phenomenology is novel, combining signatures that are
typical of R-parity violating scenarios with signatures arising from
leptoquarks. Correspondingly the constraints from electroweak precision data
are also different. In these models, one of the leptons mixes with gauginos and
superpotential Yukawa couplings can contribute to EWPM at tree level. In
addition, lepton universality is broken. In this paper we adapt the operators
analysis of Han and Skiba [1] to include the relevant violation of lepton
universality, and do a global fit of the model to electroweak precision data,
including all relevant tree-level and loop-level effects. We obtain bounds on
the vev of the sneutrino and on the superpotential couplings of the model.Comment: 18 pages, 6 figures, references adde
LHC constraints on Mini-Split anomaly and gauge mediation and prospects for LHC 14 and a future 100 TeV pp collider
Stringent experimental constraints have raised the lower limit on the masses
of squarks to TeV levels, while compatibility with the mass of the Higgs boson
provides an upper limit. This two-sided bound has lead to the emergence of
Mini-Split theories where gauginos are not far removed from the electroweak
scale while scalars are somewhat heavier. This small hierarchy modifies the
spectrum of standard anomaly and gauge mediation, leading to Mini-Split
deflected anomaly and gauge mediation models. In this paper, we study LHC
constraints on these models and their prospects at LHC 14 and a 100 TeV
collider. Current constraints on their parameter space come from ATLAS and CMS
supersymmetry searches, the known mass of the Higgs boson, and the absence of a
color-breaking vacuum. Prospects at LHC 14 and a 100 TeV collider are obtained
from these same theoretical constraints in conjunction with background
estimates. As would be expected from renormalization group effects, a slightly
lighter third generation of squarks is assumed. Higgsinos have masses similar
to those of the scalars and are at the origin of the deflection.Comment: 25 pages, 10 figures, references added, LHC 14 results added, matched
to journal versio
The spontaneous breaking Twin Higgs
The Twin Higgs model seeks to address the little hierarchy problem by making
the Higgs a pseudo-Goldstone of a global symmetry that is spontaneously
broken to . Gauge and Yukawa couplings, which explicitly break ,
enjoy a discrete symmetry that accidentally maintains at
the quadratic level and therefore keeps the Higgs light. Contrary to most
beyond the Standard Model theories, the quadratically divergent corrections to
the Higgs mass are cancelled by a mirror sector, which is uncharged under the
Standard Model groups. However, the Twin Higgs with an exact
symmetry leads to equal vevs in the Standard Model and mirror sectors, which is
phenomenologically unviable. An explicit breaking potential must
then be introduced and tuned against the breaking terms to produce a
hierarchy of vevs between the two sectors. This leads to a moderate but
non-negligible tuning. We propose a model to alleviate this tuning, without the
need for an explicit breaking sector. The model consists of two
fundamental Higgses, one whose vacuum preserves and one
whose vacuum breaks it. As the interactions between the two Higgses are turned
on, the breaking is transmitted from the broken to the unbroken
sector and a small hierarchy of vevs is naturally produced. The presence of an
effective tadpole and feedback between the two Higgses lead to a sizable
improvement of the tuning. The resulting Higgs boson is naturally very Standard
Model like.Comment: 17 pages, 6 figures, references update
Searching for periodic signals in kinematic distributions using continuous wavelet transforms
Many models of physics beyond the Standard Model include towers of particles
whose masses follow an approximately periodic pattern with little spacing
between them. These resonances might be too weak to detect individually, but
could be discovered as a group by looking for periodic signals in kinematic
distributions. The continuous wavelet transform, which indicates how much a
given frequency is present in a signal at a given time, is an ideal tool for
this. In this paper, we present a series of methods through which continuous
wavelet transforms can be used to discover periodic signals in kinematic
distributions. Some of these methods are based on a simple test statistic,
while others make use of machine learning techniques. Some of the methods are
meant to be used with a particular model in mind, while others are
model-independent. We find that continuous wavelet transforms can give bounds
comparable to current searches and, in some cases, be sensitive to signals that
would go undetected by standard experimental strategies.Comment: 22 pages, 7 figures, matches version published in EPJ
On the observability of the Higgs decay to a photon and a dark photon
Many collider searches have attempted to detect the Higgs boson decaying to a
photon and an invisible massless dark photon. For the branching ratio to this
channel to be realistically observable at the LHC, there must exist new
mediators that interact with both the standard model and the dark photon. In
this paper, we study experimental and theoretical constraints on an extensive
set of mediator models. We show that these constraints limit the Higgs
branching ratio to a photon and a dark photon to be far smaller than the
current sensitivity of collider searches.Comment: 17 pages, 5 figure
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