22,279 research outputs found
Colorphilic Spin-2 Resonances in the LHC Dijet Channel
Experiments at the LHC may yet discover a dijet resonance indicative of
Beyond the Standard Model (BSM) physics. In this case, the question becomes:
what BSM theories are consistent with the unexpected resonance? One possibility
would be a spin-2 object called the colorphilic graviton--a spin-2
color-singlet particle which couples exclusively to the quark and gluon
stress-energy tensors. We assess the possibility of this state's discovery in
the dijet channel as an s-channel resonance, and report the regions of
parameter space where colorphilic gravitons have not yet been excluded by
LHC-13 data but still may be discovered in the dijet channel at LHC-14 for
integrated luminosities of 0.3, 1, and 3 ab. We then delineate which of
those regions remain accessible to future collider searches, once one accounts
for applicability of the narrow-width approximation, detector mass resolution,
and self-consistency according to tree-level partial-wave unitarity. We
discover that--despite the strong constraints unitarity imposes on collider
searches--the colorphilic graviton remains potentially discoverable in the LHC
dijet channel. A means of investigation would be to apply the color
discriminant variable (CDV), a dimensionless combination of quantities
(cross-section, decay width, and invariant mass) that can be quickly measured
after the discovery of a dijet resonance. Previous publications have
demonstrated the CDV's utility when applied to theories containing Z',
colorons, excited quarks, and diquarks. We extend this analysis to the
colorphilic graviton by applying the CDV to the appropriate region of parameter
space. We conclude that resolvable, discoverable dijet resonances consistent
with colorphilic gravitons span a narrower range of masses than those
consistent with leptophobic Z' models, and can be distinguished from those
originating from coloron, excited quark, and diquark models.Comment: 23 pages, 4 figures, updated notation and figure
History of "Anomalous" Atmospheric Neutrino Events: A First Person Account
The modern picture of the neutrino as a multiple mass highly mixed neutral
particle has emerged over 40 years of study. Best known of the issues leading
to this picture was the apparent loss of neutrinos coming from the sun. This
article describes another piece of evidence that supports the picture; the
substantial reduction of high energy muon type neutrinos observed in nature.
For much of the 40 year period, before the modern picture emerged this
observation was known as the "atmospheric neutrino anomaly", since as will be
seen, these neutrinos originate in the Earth's atmosphere.
This paper describes the discovery of the atmospheric neutrino anomaly. We
explore the scientific context and motivations in the late 1970's from which
this work emerged. The gradual awareness that the observations of atmospheric
neutrinos were not as expected took place in the 1983-1986 period.Comment: 46 pages, 24 figures. To be published in Physics in Perspective
Version 2 has a table of contents, a table of figures and the DOI added The
final publication is available at Springer via
http://dx.doi.org/10.1007/s00016-016-0185-
The Standard Model: How far can it go and how can we tell?
The Standard Model of particle physics encapsulates our current best
understanding of physics at the smallest distances and highest energies. It
incorporates Quantum Electrodynamics (the quantised version of Maxwell's
electromagnetism) and the weak and strong interactions, and has survived
unmodified for decades, save for the inclusion of non-zero neutrino masses
after the observation of neutrino oscillations in the late 1990s. It describes
a vast array of data over a wide range of energy scales. I review a selection
of these successes, including the remarkably successful prediction of a new
scalar boson, a qualitatively new kind of object observed in 2012 at the Large
Hadron Collider. New calculational techniques and experimental advances
challenge the Standard Model across an ever-wider range of phenomena, now
extending significantly above the electroweak symmetry breaking scale. I will
outline some of the consequences of these new challenges, and briefly discuss
what is still to be found.Comment: Write up of a talk given at "Unifying physics and technology in light
of Maxwell's equations", a Royal Society meeting organised by A. Zayats, J.
Ellis, R. Pike on the 150th anniversary of Maxwell's equation
Search for Standard Higgs Boson at Supercolliders
We review the standard Higgs boson physics and the search for higgs boson at
LEP and LHC supercollidersComment: latex, 70 pages, 15 ps.figure
Long-Lived Sleptons at the LHC and a 100 TeV Proton Collider
We study the prospects for long-lived charged particle (LLCP) searches at
current and future LHC runs and at a 100 TeV pp collider, using Drell-Yan
slepton pair production as an example. Because momentum measurements become
more challenging for very energetic particles, we carefully treat the expected
momentum resolution. At the same time, a novel feature of 100 TeV collisions is
the significant energy loss of energetic muons in detectors. We use this to
help discriminate between muons and LLCPs. We find that the 14 TeV LHC with an
integrated luminosity of 3 ab can probe LLCP slepton masses up to 1.2
TeV, and a 100 TeV pp collider with 3 ab can probe LLCP slepton masses
up to 4 TeV, using time-of-flight measurements. These searches will have
striking implications for dark matter, with the LHC definitively testing the
possibility of slepton-neutralino co-annihilating WIMP dark matter, and with
the LHC and future hadron colliders having a strong potential for discovering
LLCPs in models with superWIMP dark matter.Comment: 24 pages, 9 figures, revised to match published versio
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