4,761 research outputs found
Observables with tau leptons at LHC and LC structure of event records and Monte Carlo Algorithms
In the present report, let us adress the issues related to simulation of
decays for particle embodied in full production and decay chains of Monte Carlo
programs set-up for experiments such as at LHC or LC. Both technical issues
related to the way how the events may be stored in event records and issues
related to physics (in particular non-factorizable correlations of the
Einstein-Rosen-Podolsky type) will be reviewed on the basis of practical
examples. We will limit our discussion to the case of tau lepton and W boson
decays, but similar problems (and solutions) may arise also in case of
simulation for other intermediate states or particles. Examples related to
construction of physics observables will be also given. In particular the
method of measuring the CP parity properties of the h-tau-tau coupling at LC
will be explained.Comment: 5 pages, 3 Postscript figures, uses espcrc2.sty, Presented at IX
Workshop on A C A T in Physics Research, December 1-5, 2003, KEK, Tsukuba,
Japa
High-Temperature Processing of Solids Through Solar Nebular Bow Shocks: 3D Radiation Hydrodynamics Simulations with Particles
A fundamental, unsolved problem in Solar System formation is explaining the
melting and crystallization of chondrules found in chondritic meteorites.
Theoretical models of chondrule melting in nebular shocks has been shown to be
consistent with many aspects of thermal histories inferred for chondrules from
laboratory experiments; but, the mechanism driving these shocks is unknown.
Planetesimals and planetary embryos on eccentric orbits can produce bow shocks
as they move supersonically through the disk gas, and are one possible source
of chondrule-melting shocks. We investigate chondrule formation in bow shocks
around planetoids through 3D radiation hydrodynamics simulations. A new
radiation transport algorithm that combines elements of flux-limited diffusion
and Monte Carlo methods is used to capture the complexity of radiative
transport around bow shocks. An equation of state that includes the rotational,
vibrational, and dissociation modes of H is also used. Solids are followed
directly in the simulations and their thermal histories are recorded. Adiabatic
expansion creates rapid cooling of the gas, and tail shocks behind the embryo
can cause secondary heating events. Radiative transport is efficient, and bow
shocks around planetoids can have luminosities few
L. While barred and radial chondrule textures could be produced in
the radiative shocks explored here, porphyritic chondrules may only be possible
in the adiabatic limit. We present a series of predicted cooling curves that
merit investigation in laboratory experiments to determine whether the solids
produced by bow shocks are represented in the meteoritic record by chondrules
or other solids.Comment: Accepted for publication in ApJ. Images have been resized to conform
to arXiv limits, but are all readable upon adjusting the zoom. Changes from
v1: Corrected typos discovered in proofs. Most changes are in the appendi
Physics at Future Linear Colliders
This article summarises the physics at future linear colliders. It will be
shown that in all studied physics scenarios a 1 TeV linear collider in addition
to the LHC will enhance our knowledge significantly and helps to reconstruct
the model of new physics nature has chosen.Comment: Invited talk at the Lepton Photon Symposium 2005, Upsala, Sweden,
July 2005, V2: minor improvement
The Precision of Higgs Boson Measurements and Their Implications
The prospects for a precise exploration of the properties of a single or many
observed Higgs bosons at future accelerators are summarized, with particular
emphasis on the abilities of a Linear Collider (LC). Some implications of these
measurements for discerning new physics beyond the Standard Model (SM) are also
discussed.Comment: Summary report of the Precision Higgs Working Group P1WG2 at Snowmass
200
Stau as the Lightest Supersymmetric Particle in R-Parity Violating SUSY Models: Discovery Potential with Early LHC Data
We investigate the discovery potential of the LHC experiments for R-parity
violating supersymmetric models with a stau as the lightest supersymmetric
particle (LSP) in the framework of minimal supergravity. We classify the final
states according to their phenomenology for different R-parity violating decays
of the LSP. We then develop event selection cuts for a specific benchmark
scenario with promising signatures for the first beyond the Standard Model
discoveries at the LHC. For the first time in this model, we perform a detailed
signal over background analysis. We use fast detector simulations to estimate
the discovery significance taking the most important Standard Model backgrounds
into account. Assuming an integrated luminosity of 1 inverse femtobarn at a
center-of-mass energy of 7 TeV, we perform scans in the parameter space around
the benchmark scenario we consider. We then study the feasibility to estimate
the mass of the stau-LSP. We briefly discuss difficulties, which arise in the
identification of hadronic tau decays due to small tau momenta and large
particle multiplicities in our scenarios.Comment: 26 pages, 18 figures, LaTeX; minor changes, final version published
in PR
Cooling of Dense Gas by H2O Line Emission and an Assessment of its Effects in Chondrule-Forming Shocks
We consider gas at densities appropriate to protoplanetary disks and
calculate its ability to cool due to line radiation emitted by H2O molecules
within the gas. Our work follows that of Neufeld & Kaufman (1993; ApJ, 418,
263), expanding on their work in several key aspects, including use of a much
expanded line database, an improved escape probability formulism, and the
inclusion of dust grains, which can absorb line photons. Although the escape
probabilities formally depend on a complicated combination of optical depth in
the lines and in the dust grains, we show that the cooling rate including dust
is well approximated by the dust-free cooling rate multiplied by a simple
function of the dust optical depth. We apply the resultant cooling rate of a
dust-gas mixture to the case of a solar nebula shock pertinent to the formation
of chondrules, millimeter-sized melt droplets found in meteorites. Our aim is
to assess whether line cooling can be neglected in chondrule-forming shocks or
if it must be included. We find that for typical parameters, H2O line cooling
shuts off a few minutes past the shock front; line photons that might otherwise
escape the shocked region and cool the gas will be absorbed by dust grains.
During the first minute or so past the shock, however, line photons will cool
the gas at rates ~ 10,000 K/hr, dropping the temperature of the gas (and most
likely the chondrules within the gas) by several hundred K. Inclusion of H2O
line cooling therefore must be included in models of chondrule formation by
nebular shocks.Comment: Accepted for publication in The Astrophysical Journa
Saturn as a radio source
Magnetospheric radio emissions, Saturn electrostatic discharges, inferred source locations, and emission theories are addressed
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