116 research outputs found
Technicolor in the LHC Era
LHC searches for the standard model Higgs Boson in \gamma\gamma\ or \tau\tau\
decay modes place strong constraints on the light technipion state predicted in
technicolor models that include colored technifermions. Compared with the
standard Higgs Boson, the technipions have an enhanced production rate (largely
because the technipion decay constant is smaller than the weak scale) and also
enhanced branching ratios into di-photon and di-tau final states (largely due
to the suppression of WW decays of the technipions). Recent ATLAS and CMS
searches for Higgs bosons exclude the presence of technipions with masses from
110 GeV to nearly 2m_t in technicolor models that (a) include colored
technifermions (b) feature topcolor dynamics and (c) have technicolor groups
with three or more technicolors (N_{TC} > 3).Comment: 15 pages, pdf figures embedded. Contribution to KMI Inauguration
Conference "Quest for the Origin of Particles and the Universe" (KMIIN),
24-26 Nov. 2011, KMI, Nagoya Universit
Color Discriminant Variable to Separate Dijet Resonances at the LHC
A narrow resonance decaying to dijets could be discovered at the 14 TeV run
of the LHC. To quickly identify its color structure in a model-independent
manner, we introduced a method based on a color discriminant variable,
determined from the measurements of the resonance's production cross section,
mass and width. This talk introduces a more transparent theoretical formulation
of the color discriminant variable that highlights its relationship to the
branching ratios of the resonance into incoming and outgoing partons and to the
properties of those partons. The formulation makes it easier to predict the
value of the variable for a given class of resonance. We show that this method
applies well to color-triplet and color-sextet scalar diquarks, distinguishing
them clearly from other candidate resonances.Comment: 9 pages, 3 figures. Presentation at the DPF 2015 Meeting of the
American Physical Society Division of Particles and Fields, Ann Arbor,
Michigan, August 4-8, 201
The Color Discriminant Variable and Scalar Diquarks at the LHC
The LHC is actively searching for narrow dijet resonances corresponding to
physics beyond the Standard Model. Among the many resonances that have been
postulated (e.g., colored vectors, scalars, and fermions) one that would have a
particularly large production rate at the LHC would be a scalar diquark
produced in the s-channel via fusion of two valence quarks. In previous work,
we introduced a color discriminant variable that distinguishes among various
dijet resonances, drawing on measurements of the dijet resonance mass, total
decay width and production cross-section. Here, we show that this
model-independent method applies well to color-triplet and color-sextet scalar
diquarks, distinguishing them clearly from other candidate resonances. We also
introduce a more transparent theoretical formulation of the color discriminant
variable that highlights its relationship to the branching ratios of the
resonance into incoming and outgoing partons and to the properties of those
partons. While the original description of the color discriminant variable
remains convenient for phenomenological use upon discovery of a new resonance,
the new formulation makes it easier to predict the value of the variable for a
given class of resonance.Comment: 22 pages, 11 pdf figures. One reference added, one updated. arXiv
admin note: text overlap with arXiv:1406.200
Distinguishing Color-Octet and Color-Singlet Resonances at the Large Hadron Collider
Di-jet resonance searches are simple, yet powerful and model-independent,
probes for discovering new particles at hadron colliders. Once such a resonance
has been discovered it is important to determine the mass, spin, couplings,
chiral behavior and color properties to determine the underlying theoretical
structure. We propose a new variable which, in the absence of decays of the
resonance into new non-standard states, distinguishes between color-octet and
color-singlet resonances. To keep our study widely applicable we study
phenomenological models of color-octet and color-singlet resonances in flavor
universal as well as flavor non-universal scenarios. We present our analysis
for a wide range of mass (2.5 - 6 TeV), couplings and flavor scenarios for the
LHC with center of mass energy of 14 TeV and varying integrated luminosities of
30, 100, 300 and 1000 . We find encouraging results to
distinguish color-octet and color-singlet resonances for different flavor
scenarios at the LHC.Comment: 24 pages, 5 figures, 1 tabl
Simplified Limits on New LHC Resonances
If an excess potentially heralding new physics is noticed in collider data,
it would be useful to be able to compare the data with entire classes of models
at once. This talk discusses a method that applies when the new physics
corresponds to the production and decay of a single, relatively narrow,
s-channel resonance. A simplifed model of the resonance allows us to convert an
estimated signal cross section into model-independent bounds on the product of
the branching ratios corresponding to production and decay. This quickly
reveals whether a given class of models could possibly produce a signal of the
observed size. We will describe how to apply our analysis framework to cases of
current experimental interest, including resonances decaying to dibosons,
diphotons, dileptons, or dijets.Comment: 13 pages, 5 figures; Proceedings of 12th Conference on Quark
Confinement and the Hadron Spectru
Simplified Limits on Resonances at the LHC
In the earliest stages of evaluating new collider data, especially if a small
excess may be present, it would be useful to have a method for comparing the
data with entire classes of models, to get an immediate sense of which classes
could conceivably be relevant. In this paper, we propose a method that applies
when the new physics invoked to explain the excess corresponds to the
production and decay of a single, relatively narrow, -channel resonance. A
simplifed model of the resonance allows us to convert an estimated signal cross
section into model-independent bounds on the product of the branching ratios
corresponding to production and decay. This quickly reveals whether a given
class of models could possibly produce a signal of the required size at the
LHC. Our work sets up a general framework, outlines how it operates for
resonances with different numbers of production and decay modes, and analyzes
cases of current experimental interest, including resonances decaying to
dibosons, diphotons, dileptons, or dijets. If the LHC experiments were to
report their searches for new resonances beyond the standard model in the
simplified limits variable defined in this paper, that would make it
far easier to avoid blind alleys and home in on the most likely candidate
models to explain any observed excesses.Comment: 31 pages, png and pdf figures embedded; title change and other minor
changes in response to referee comment
Probing Color Octet Couplings at the Large Hadron Collider
Color-octet resonances arise in many well motivated theories beyond the
standard model. As colored objects they are produced copiously at the LHC and
can be discovered in early searches for new physics in dijet final states. Once
they are discovered it will be important to measure the couplings of the new
resonances to determine the underlying theoretical structure. We propose a new
channel, associated production of gauge bosons and color-octet
resonances, to help determine the chiral structure of the couplings. We present
our analysis for a range of color-octet masses (2.5 to 4.5 TeV), couplings and
decay widths for the LHC with center of mass energy of 14 TeV and 10 or 100 of integrated luminosity. We find that the LHC
can probe a large region of the parameter space up to very small couplings.Comment: 19 pages, 9 figures, 3 table
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