785 research outputs found
A 2 TeV , Supersymmetry, and the Higgs Mass
A recent ATLAS search for diboson resonances and a CMS search for
resonances which both show excesses with significance around 3 sigma have
generated interest in gauge extensions of the Standard Model with a
mass around 2 TeV. We investigate the possibility that an gauge
extension of the MSSM compatible with an explanation of the diboson anomaly
might give rise to a significant enhancement of the Higgs mass above the MSSM
tree level bound due to non-decoupling
D-terms. This model contains a vector-like charge -1/3 singlet quark
for each generation which mixes significantly with the doublet
quarks, affecting the phenomenology. We find that it is possible to
achieve , and this requires that the
mass is close to 3 TeV.Comment: 18 pages + appendices, 6 figure
Hidden-Sector Higgs Bosons at High-Energy Electron-Positron Colliders
The possibility of a scalar messenger that can couple the Standard Model (SM)
to a hidden sector has been discussed in a variety of contexts in the
literature in recent years. We consider the case that a new scalar singlet
charged under an exotic spontaneously broken Abelian gauge symmetry mixes
weakly with the SM Higgs resulting in two scalar mass states, one of which has
heavily suppressed couplings to the SM particles. Previous phenomenological
studies have focussed on potential signatures for such a model at the Large
Hadron Collider (LHC). However, there are interesting regions of the parameter
space in which the heavier Higgs state would be out of reach for LHC searches
if its mass is greater than 1 TeV. We therefore investigate the discovery
potential for such a particle at a 3 TeV electron-positron collider, which is
motivated by the recent developments of the Compact Linear Collider (CLIC). We
find that such an experiment could substantially extend our discovery reach for
a heavy, weakly coupled Higgs boson, and we discuss three possible search
channels.Comment: 14 pages, 8 Figures. Published as an LCD Not
Anomaly Detection for Resonant New Physics with Machine Learning
Despite extensive theoretical motivation for physics beyond the Standard
Model (BSM) of particle physics, searches at the Large Hadron Collider (LHC)
have found no significant evidence for BSM physics. Therefore, it is essential
to broaden the sensitivity of the search program to include unexpected
scenarios. We present a new model-agnostic anomaly detection technique that
naturally benefits from modern machine learning algorithms. The only
requirement on the signal for this new procedure is that it is localized in at
least one known direction in phase space. Any other directions of phase space
that are uncorrelated with the localized one can be used to search for
unexpected features. This new method is applied to the dijet resonance search
to show that it can turn a modest 2 sigma excess into a 7 sigma excess for a
model with an intermediate BSM particle that is not currently targeted by a
dedicated search.Comment: Replaced with short PRL version. 7 pages, 2 figures. Revised long
version will be submitted separatel
Dedicated Strategies for Triboson Signals from Cascade Decays of Vector Resonances
New colorless electroweak (EW) charged spin-1 particles with mass of a few
TeV arise in numerous extensions of the Standard Model (SM). Decays of such a
vector into a pair of SM particles, either fermions or EW bosons, are well
studied. Many of these models have an additional scalar, which can lead to (and
even dominate in certain parameter regions) a novel decay channel for the heavy
vector particles instead - into a SM EW boson and the scalar, which
subsequently decays into a SM EW boson pair. In this work, we focus on the
scalar being relatively heavy, roughly factor of two lighter than the vector
particles, rendering its decay products well separated. Such a cascade decay
results in a final state with three isolated bosons. We argue that for this
"triboson" signal the existing diboson searches are not quite optimal due to
combinatorial ambiguity for three identical bosons, and in addition, due to a
relatively small signal cross-section determined by the heaviness of the
decaying vector particle. In order to isolate the signal, we demonstrate that
tagging all three bosons, followed by use of the full triboson invariant mass
distribution as well as that of appropriate subsets of dibosons, is well
motivated. We develop these general strategies in detail within the context of
a specific class of models that are based on extensions of the standard warped
extra-dimensional scenario. We also point out that a similar analysis would
apply to models with an enlarged EW gauge sector in four dimensions, even if
they involve a different Lorentz structure for the relevant couplings
Detecting a Boosted Diboson Resonance
New light scalar particles in the mass range of hundreds of GeV, decaying
into a pair of bosons can appear in several extensions of the SM. The
focus of collider studies for such a scalar is often on its direct production,
where the scalar is typically only mildly boosted. The observed are
therefore well-separated, allowing analyses for the scalar resonance in a
standard fashion as a low-mass diboson resonance. In this work we instead focus
on the scenario where the direct production of the scalar is suppressed, and it
is rather produced via the decay of a significantly heavier (a few TeV mass)
new particle, in conjunction with SM particles. Such a process results in the
scalar being highly boosted, rendering the 's from its decay merged. The
final state in such a decay is a "fat" jet, which can be either four-pronged
(for fully hadronic decays), or may be like a jet, but with leptons
buried inside (if one of the decays leptonically). In addition, this fat
jet has a jet mass that can be quite different from that of the /Higgs/top
quark-induced jet, and may be missed by existing searches. In this work, we
develop dedicated algorithms for tagging such multi-layered "boosted dibosons"
at the LHC. As a concrete application, we discuss an extension of the standard
warped extra-dimensional framework where such a light scalar can arise. We
demonstrate that the use of these algorithms gives sensitivity in mass ranges
that are otherwise poorly constrained.Comment: 33 pages, 13 figure
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