4,596 research outputs found
Beyond the Standard Model for Montaneros
These notes cover (i) electroweak symmetry breaking in the Standard Model
(SM) and the Higgs boson, (ii) alternatives to the SM Higgs boson including an
introduction to composite Higgs models and Higgsless models that invoke extra
dimensions, (iii) the theory and phenomenology of supersymmetry, and (iv)
various further beyond topics, including Grand Unification, proton decay and
neutrino masses, supergravity, superstrings and extra dimensions.Comment: Based on lectures by John Ellis at the 5th CERN-Latin-American School
of High-Energy Physics, Recinto Quirama, Colombia, 15 - 28 Mar 2009, 84
pages, 35 figure
MCFM for the Tevatron and the LHC
A summary is given of the current status of the next-to-leading order (NLO)
parton-level integrator MCFM. Some details are given about the Higgs + 2-jet
process and the production and decay of , both of which have
recently been added to the code. Using MCFM, comparisons between the Tevatron
running at ~TeV and the LHC running at ~TeV are made
for standard model process including the production of Higgs bosons. The case
for running the Tevatron until 16fb are accumulated by both detectors is
sketched.Comment: Talk presented by R.K Ellis at Loops and Legs in Quantum Field Theory
2010, Woerlitz, Germany, April 25-30, 2010, (6 pages and 4 figures
Exotic Baryons in Two-Dimensional QCD
Two-dimensional QCD has often been used as a laboratory for studying the full
four-dimensional theory, providing, for example, an explicit realization of
baryons as solitons. We review aspects of conventional baryons in
two-dimensional QCD, including the classical and quantum contributions to their
masses. We then discuss the spectrum of exotic baryons in two-dimensional QCD,
commenting on the solitonic radius inferred from the excitation spectrum as
well as the two-dimensional version of the Goldberger-Treiman relation relating
meson couplings to current matrix elements. Two-dimensional QCD provides strong
overall support to the chiral-soliton picture for the structure of normal and
exotic baryons in four dimensions.Comment: 15 pages latex, no figure
QCD corrections to the hadronic production of a heavy quark pair and a W-boson including decay correlations
We perform an analytic calculation of the one-loop amplitude for the W-boson
mediated process 0 \to d u-bar Q Q-bar l-bar l, retaining the mass for the
quark Q. The momentum of each of the massive quarks is expressed as the sum of
two massless momenta and the corresponding heavy quark spinor is expressed as a
sum of two massless spinors. Using a special choice for the heavy quark spinors
we obtain analytic expressions for the one-loop amplitudes which are amenable
to fast numerical evaluation. The full next-to-leading order (NLO) calculation
of hadron+hadron \to W(\to e nu) b b-bar with massive b-quarks is included in
the program MCFM. A comparison is performed with previous published work.Comment: 45 pages, 17 figure
Hadronic production of a Higgs boson and two jets at next-to-leading order
We perform an update of the next-to-leading order calculation of the rate for
Higgs boson production in association with two jets. Our new calculation
incorporates the full analytic result for the one-loop virtual amplitude. This
new theoretical information allows us to construct a code including the decay
of the Higgs boson without incurring a prohibitive penalty in computer running
time. Results are presented for the Tevatron, where implications for the Higgs
search are sketched, and also for a range of scenarios at the LHC.Comment: 16 pages, 4 figure
Quantum Decoherence in a D-Foam Background
Within the general framework of Liouville string theory, we construct a model
for quantum D-brane fluctuations in the space-time background through which
light closed-string states propagate. The model is based on monopole and vortex
defects on the world sheet, which have been discussed previously in a treatment
of 1+1-dimensional black-hole fluctuations in the space-time background, and
makes use of a T-duality transformation to relate formulations with Neumann and
Dirichlet boundary conditions. In accordance with previous general arguments,
we derive an open quantum-mechanical description of this D-brane foam which
embodies momentum and energy conservation and small mean energy fluctuations.
Quantum decoherence effects appear at a rate consistent with previous
estimates.Comment: 16 pages, Latex, two eps figures include
Prospects for Discovering Supersymmetry at the LHC
Supersymmetry is one of the best-motivated candidates for physics beyond the
Standard Model that might be discovered at the LHC. There are many reasons to
expect that it may appear at the TeV scale, in particular because it provides a
natural cold dark matter candidate. The apparent discrepancy between the
experimental measurement of g_mu - 2 and the Standard model value calculated
using low-energy e+ e- data favours relatively light sparticles accessible to
the LHC. A global likelihood analysis including this, other electroweak
precision observables and B-decay observables suggests that the LHC might be
able to discover supersymmetry with 1/fb or less of integrated luminosity. The
LHC should be able to discover supersymmetry via the classic missing-energy
signature, or in alternative phenomenological scenarios. The prospects for
discovering supersymmetry at the LHC look very good.Comment: 8 pages, 11 figure
Heinrich von Kleist
Ellis's book confronts directly the most central issue of Kleist criticism: the essential nature and meaning of his work. Rather than provide a general survey of Kleist's writings, Ellis performs an analysis of six of his most mature works: "Der Findling", "Die Marquise von O. . .", "Das Erdbeben in Chili", "Der Zweitkampf", "Michael Kohlhaas", and "Prinz Friedrich von Homburg". Ellis draws some general conclusions about the uniquely Kleistian character of these six works which are at sharp variance with previous Kleist criticism
Discovering baryon-number violating neutralino decays at the LHC.
Recently there has been much interest in the use of single-jet mass and jet substructure to identify boosted particles decaying hadronically at the LHC. We develop these ideas to address the challenging case of a neutralino decaying to three quarks in models with baryonic violation of R parity. These decays have previously been found to be swamped by QCD backgrounds. We demonstrate for the first time that such a decay might be observed directly at the LHC with high significance, by exploiting characteristics of the scales at which its composite jet breaks up into subjets
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