71 research outputs found
Top Quark Properties in Little Higgs Models
We study the shifts in the gauge couplings of the top quark induced in the
Littlest Higgs model with and without T parity. We find that the ILC will be
able to observe the shifts throughout the natural range of model parameters.Comment: 3 pages, 4 figures. Contributed to 2005 International Linear Collider
Physics and Detector Workshop and 2nd ILC Accelerator Workshop, Snowmass,
Colorado, 14-27 Aug 200
Recommended from our members
Measurements of Rates, Asymmetries, and Angular Distributions in B -> K l+ l- and B -> K* l+ l- Decays
This dissertation describes studies of the rare decays B{sub d} {yields} K{ell}{sup +}{ell}{sup -} and B{sub d} {yields} K*{ell}{sup +}{ell}{sup -}, where {ell}{sup +}{ell}{sup -} is either an e{sup +}e{sup -} or a {mu}{sup +}{mu}{sup -} pair. These decays are highly suppressed in the Standard Model, and could be strongly affected by physics beyond the Standard Model. The authors measure the total branching fractions {Beta}(B{sub d} {yields} K{ell}{sup +}{ell}{sup -}) = (0.34 {+-} 0.07 {+-} 0.03) x 10{sup -6}, {Beta}(B{sub d} {yields} K*{ell}{sup +}{ell}{sup -}) = (0.78{sub -0.17}{sup +0.19} {+-} 0.12) x 10{sup -6}. In addition, they measure the partial branching fractions, relative abundance of muons to electrons, direct CP asymmetry, dilepton forward-backward asymmetry, and longitudinal polarization of the K* in these modes. They also search for the lepton flavor-violating decays B{sub d} {yields} Ke{sup {+-}}{mu}{sup {-+}} and B{sub d} {yields} K*e{sup {+-}}{mu}{sup {-+}}. The measurements were performed at the SLAC PEP II storage ring running at the {Upsilon}(4S) resonance
Recommended from our members
Polarization Possibilities of Small Spin-Orbit Interaction in Strained-Superlattice Photocathodes
Strained-superlattice photocathodes based on InGaP/GaAs were investigated. The photocathode performance is found highly dependent on the superlattice parameters. The electron confinement energy in superlattice appears important
Report of the 2005 Snowmass Top/QCD Working Group
This report discusses several topics in both top quark physics and QCD at an
International Linear Collider (ILC). Issues such as measurements at the
threshold, including both theoretical and machine requirements, and
the determination of electroweak top quark couplings, are reviewed. New results
concerning the potential of a 500 GeV collider for measuring
couplings and the top quark Yukawa coupling are presented. The status of higher
order QCD corrections to jet production cross sections, heavy quark form
factors, and longitudinal gauge boson scattering, needed for percent-level
studies at the ILC, are reviewed. A new study of the measurement of the
hadronic structure of the photon at a collider is presented. The
effects on top quark properties from several models of new physics, including
composite models, Little Higgs theories, and CPT violation, are studied.Comment: 39 pages, many figs; typos fixed and refs added. Contributed to the
2005 International Linear Collider Physics and Detector Workshop and 2nd ILC
Accelerator Workshop, Snowmass, Colorado, 14-27 Aug 200
On the influence of the cosmological constant on gravitational lensing in small systems
The cosmological constant Lambda affects gravitational lensing phenomena. The
contribution of Lambda to the observable angular positions of multiple images
and to their amplification and time delay is here computed through a study in
the weak deflection limit of the equations of motion in the Schwarzschild-de
Sitter metric. Due to Lambda the unresolved images are slightly demagnified,
the radius of the Einstein ring decreases and the time delay increases. The
effect is however negligible for near lenses. In the case of null cosmological
constant, we provide some updated results on lensing by a Schwarzschild black
hole.Comment: 8 pages, 1 figure; v2: extended discussion on the lens equation,
references added, results unchanged, in press on PR
Recommended from our members
Gamma Lines without a Continuum: Thermal Models for the Fermi-LAT 130 GeV Gamma Line
Recommended from our members
Simplified Models for LHC New Physics Searches
This document proposes a collection of simplified models relevant to the design of new-physics searches at the LHC and the characterization of their results. Both ATLAS and CMS have already presented some results in terms of simplified models, and we encourage them to continue and expand this effort, which supplements both signature-based results and benchmark model interpretations. A simplified model is defined by an effective Lagrangian describing the interactions of a small number of new particles. Simplified models can equally well be described by a small number of masses and cross-sections. These parameters are directly related to collider physics observables, making simplified models a particularly effective framework for evaluating searches and a useful starting point for characterizing positive signals of new physics. This document serves as an official summary of the results from the 'Topologies for Early LHC Searches' workshop, held at SLAC in September of 2010, the purpose of which was to develop a set of representative models that can be used to cover all relevant phase space in experimental searches. Particular emphasis is placed on searches relevant for the first {approx} 50-500 pb{sup -1} of data and those motivated by supersymmetric models. This note largely summarizes material posted at http://lhcnewphysics.org/, which includes simplified model definitions, Monte Carlo material, and supporting contacts within the theory community. We also comment on future developments that may be useful as more data is gathered and analyzed by the experiments
Recommended from our members
Supersymmetry Parameter Analysis: SPA Convention and Project
Recommended from our members
Section on Supernova Remnants and Cosmic Rays of the White Paper on the Status and Future of Ground-Based Gamma-Ray Astronomy
This is a report on the findings of the SNR/cosmic-ray working group for the white paper on the status and future of ground-based gamma-ray astronomy. The white paper is an APS commissioned document, and the overall version has also been released and can be found on astro-ph. This detailed section of the white paper discusses the status of past and current attempts to observe shell-type supernova remnants and diffuse emission from cosmic rays at GeV-TeV energies. We concentrate on the potential of future ground-based gamma-ray experiments to study the acceleration of relativistic charged particles which is one of the main unsolved, yet fundamental, problems in modern astrophysics. The acceleration of particles relies on interactions between energetic particles and magnetic turbulence. In the case of SNRs we can perform spatially resolved studies in systems with known geometry, and the plasma physics deduced from these observations will help us to understand other systems where rapid particle acceleration is believed to occur and where observations as detailed as those of SNRs are not possible
Recommended from our members
DUSEL Theory White Paper
The scientific case for a Deep Underground Science and Engineering Laboratory [DUSEL] located at the Homestake mine in Lead, South Dakota is exceptional. The site of this future laboratory already claims a discovery for the detection of solar neutrinos, leading to a Nobel Prize for Ray Davis. Moreover this work provided the first step to our present understanding of solar neutrino oscillations and a chink in the armor of the Standard Model of particle physics. We now know, from several experiments located in deep underground experimental laboratories around the world, that neutrinos have mass and even more importantly this mass appears to fit into the framework of theories which unify all the known forces of nature, i.e. the strong, weak, electromagnetic and gravitational. Similarly, DUSEL can forge forward in the discovery of new realms of nature, housing six fundamental experiments that will test the frontiers of our knowledge: (1) Searching for nucleon decay (the decay of protons and neutrons predicted by grand unified theories of nature); (2) Searching for neutrino oscillations and CP violation by detecting neutrinos produced at a neutrino source (possibly located at Brookhaven National Laboratory and/or Fermi National Laboratory); (3) Searching for astrophysical neutrinos originating from the sun, from cosmic rays hitting the upper atmosphere or from other astrophysical sources, such a supernovae; (4) Searching for dark matter particles (the type of matter which does not interact electromagnetically, yet provides 24% of the mass of the Universe); (5) Looking for the rare process known as neutrino-less double beta decay which is predicted by most theories of neutrino mass and allows two neutrons in a nucleus to spontaneously change into two protons and two electrons; and (6) Searching for the rare process of neutron- anti-neutron oscillations, which would establish violation of baryon number symmetry. A large megaton water Cherenkov detector for neutrinos and nucleon decay, located in DUSEL and roughly 20 times the size of current detectors, can perform the first three of these experiments. The last 3 can utilize the unique environment afforded by DUSEL to perform the most sensitive tests to date. Any one of these experiments can greatly increase our knowledge of nature. The Deep Underground Science and Engineering Laboratory (DUSEL), with a Large Megaton Size Detector, is desperately needed to address a set of fundamental issues in particle and astrophysics
- …