27 research outputs found
Digging Deeper for New Physics in the LHC Data
In this paper we describe a novel, model-independent technique of
"rectangular aggregations" for mining the LHC data for hints of new physics. A
typical (CMS) search now has hundreds of signal regions, which can obscure
potentially interesting anomalies. Applying our technique to the two CMS
jets+MET SUSY searches, we identify a set of previously overlooked excesses. Among these, four excesses survive tests of inter- and
intra-search compatibility, and two are especially interesting: they are
largely overlapping between the jets+MET searches and are characterized by low
jet multiplicity, zero -jets, and low MET and . We find that resonant
color-triplet production decaying to a quark plus an invisible particle
provides an excellent fit to these two excesses and all other data -- including
the ATLAS jets+MET search, which actually sees a correlated excess. We discuss
the additional constraints coming from dijet resonance searches, monojet
searches and pair production. Based on these results, we believe the
wide-spread view that the LHC data contains no interesting excesses is greatly
exaggerated.Comment: 31 pages + appendices, 14 figures, source code for recasted searches
attached as auxiliary materia
Simplified Models for Dark Matter Interacting with Quarks
We investigate simplified models in which dark matter particles, taken to be
either Dirac or Majorana fermions, couple to quarks via colored mediators. We
determine bounds from colliders and direct detection experiments, and show how
the interplay of the two leads to a complementary view of this class of dark
matter models. Forecasts for future searches in light of the current
constraints are presented.Comment: 12 pages, 13 figures (39 images) Fixed erroneous calculation and
updated plot
An Update on the LHC Monojet Excess
In previous work, we identified an anomalous number of events in the LHC
jets+MET searches characterized by low jet multiplicity and low-to-moderate
transverse energy variables. Here, we update this analysis with results from a
new ATLAS search in the monojet channel which also shows a consistent excess.
As before, we find that this "monojet excess" is well-described by the resonant
production of a heavy colored state decaying to a quark and a massive invisible
particle. In the combined ATLAS and CMS data, we now find a local (global)
preference of 3.3 (2.5) for the new physics model over the
Standard Model-only hypothesis. As the signal regions containing the excess are
systematics-limited, we consider additional cuts to enhance the
signal-to-background ratio. We show that binning finer in and requiring
the jets to be more central can increase by a factor of .Comment: 5 pages, 5 figures, source for analysis code used in this paper in
attached Ancillary file
Systematically Searching for New Resonances at the Energy Frontier using Topological Models
We propose a new strategy to systematically search for new physics processes
in particle collisions at the energy frontier. An examination of all possible
topologies which give identifiable resonant features in a specific final state
leads to a tractable number of `topological models' per final state and gives
specific guidance for their discovery. Using one specific final state,
, as an example, we find that the number of possibilities is
reasonable and reveals simple, but as-yet-unexplored, topologies which contain
significant discovery potential. We propose analysis techniques and estimate
the sensitivity for collisions with TeV and
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Photocarrier lifetime and transport in silicon supersaturated with sulfur
Doping of silicon-on-insulator layers with sulfur to concentrations far above equilibrium by ion implantation and pulsed laser melting can result in large concentration gradients. Photocarriers generated in and near the impurity gradient can separate into different coplanar transport layers, leading to enhanced photocarrier lifetimes in thin silicon-on-insulator films. The depth from which holes escape the heavily doped region places a lower limit on the minority carrier mobility-lifetime product of 10⁻⁸ cm²/V for heavily sulfur dopedsilicon. We conclude that the cross-section for recombination through S impurities at this concentration is significantly reduced relative to isolated impurities.Research at Rensselaer was supported by the Army
Research Office under Contract No. W911NF0910470 and
by the NSF REU program at Rensselaer. Research at Harvard
was supported by US Army ARDEC under Contract
No. W15QKN-07-P-0092. D.R. was supported in part by a
National Defense Science and Engineering Graduate fellowship
Simplified Models for Dark Matter Model Building
The largest mass component of the universe is a longstanding mystery to the physics community. As a glaring source of new physics beyond the Standard Model, there is a large effort to uncover the quantum nature of dark matter. Many probes have been formed to search for this elusive matter; cultivating a rich environment for a phenomenologist. In addition to the primary probes -- colliders, direct detection, and indirect detection -- each with their own complexities, there is a plethora of prospects to illuminate our unanswered questions. In this work, phenomenological techniques for studying dark matter and other possible hints of new physics will be discussed. This work primarily focuses on the use of Simplified Models, which are intended to be a compromise between generality and validity of the theoretical description. They are often used to parameterize a particular search, develop a well-defined sense of complementarity between searches, or motivate new search strategies. Explicit examples of such models and how they may be used will be the highlight of each chapter