4,498 research outputs found
SUSY Parameter Measurements with Fittino
This article presents the results of a realistic global fit of the Lagrangian
parameters of the Minimal Supersymmetric Standard Model with no assumptions on
the SUSY breaking mechanism using the fit program Fittino. The fit is performed
using the precision of future mass measurements of superpartners at the LHC and
mass and polarized topological cross-section measurements at the ILC. Higher
order radiative corrections are accounted for wherever possible to date.
Results are obtained for a modified SPS1a MSSM benchmark scenario (general MSSM
without assumptions on the breaking mechanism) and for a specific mSUGRA
scenario. Exploiting a simulated annealing algorithm, a stable result is
obtained without any {\it a priori} assumptions on the fit parameters. Most of
the Lagrangian parameters can be extracted at the percent level or better if
theoretical uncertainties are neglected. Neither LHC nor ILC measurements alone
will be sufficient to obtain a stable result.Comment: 3 pages, presented at the 2005 International Linear Collider Physics
And Detector Workshop, Snowmass, CO, 14.-27. August 200
Fittino, a program for determining MSSM parameters from collider observables using an iterative method
Provided that Supersymmetry (SUSY) is realized, the Large Hadron Collider
(LHC) and the future International Linear Collider (ILC) may provide a wealth
of precise data from SUSY processes. An important task will be to extract the
Lagrangian parameters. On this basis the goal is to uncover the underlying
symmetry breaking mechanism from the measured observables. In order to
determine the SUSY parameters, the program Fittino has been developed. It uses
an iterative fitting technique and a Simulated Annealing algorithm to determine
the SUSY parameters directly from the observables without any a priori
knowledge of the parameters, using all available loop-corrections to masses and
couplings. Simulated Annealing is implemented as a stable and efficient method
for finding the optimal parameter values. The theoretical predictions can be
provided from any program with SUSY Les Houches Accord interface. As fit
result, a set of parameters including the full error matrix and two-dimensional
uncertainty contours are obtained. Pull distributions can automatically be
created and allow an independent cross-check of the fit results and possible
systematic shifts in the parameter determination. A determination of the
importance of the individual observables for the measurement of each parameter
can be performed after the fit. A flexible user interface is implemented,
allowing a wide range of different types of observables and a wide range of
parameters to be used.Comment: 32 pages, 6 figures, accepted by Comp. Phys. Com
Magnetic Fields Recorded by Chondrules Formed in Nebular Shocks
Recent laboratory efforts (Fu et al., 2014) have constrained the remanent
magnetizations of chondrules and the magnetic field strengths at which the
chondrules were exposed to as they cooled below their Curie points. An
outstanding question is whether the inferred paleofields represent the
background magnetic field of the solar nebula or were unique to the
chondrule-forming environment. We investigate the amplification of the magnetic
field above background values for two proposed chondrule formation mechanisms,
large-scale nebular shocks and planetary bow shocks. Behind large-scale shocks,
the magnetic field parallel to the shock front is amplified by factors , regardless of the magnetic diffusivity. Therefore, chondrules melted in
these shocks probably recorded an amplified magnetic field. Behind planetary
bow shocks, the field amplification is sensitive to the magnetic diffusivity.
We compute the gas properties behind a bow shock around a 3000 km-radius
planetary embryo, with and without atmospheres, using hydrodynamics models. We
calculate the ionization state of the hot, shocked gas, including thermionic
emission from dust, and thermal ionization of gas-phase potassium atoms, and
the magnetic diffusivity due to Ohmic dissipation and ambipolar diffusion. We
find that the diffusivity is sufficiently large that magnetic fields have
already relaxed to background values in the shock downstream where chondrules
acquire magnetizations, and that these locations are sufficiently far from the
planetary embryos that chondrules should not have recorded a significant
putative dynamo field generated on these bodies. We conclude that, if melted in
planetary bow shocks, chondrules probably recorded the background nebular
field.Comment: 17 pages, 11 figures, accepted for publication in Ap
Saturn's ionosphere: Inferred electron densities
During the two Voyager encounters with Saturn, radio bursts were detected which appear to have originated from atmospheric lightning storms. Although these bursts generally extended over frequencies from as low as 100 kHz to the upper detection limit of the instrument, 40 MHz, they often exhibited a sharp but variable low frequency cutoff below which bursts were not detected. We interpret the variable low-frequency extent of these bursts to be due to the reflection of the radio waves as they propagate through an ionosphere which varies with local time. We obtain estimates of electron densities at a variety of latitude and local time locations. These compare well with the dawn and dusk densitis measured by the Pioneer 11 Voyager Radio Science investigations, and with model predictions for dayside densities. However, we infer a two-order-of-magnitude diurnal variation of electron density, which had not been anticipated by theoretical models of Saturn's ionosphere, and an equally dramatic extinction of ionospheric electron density by Saturn's rings
The source of Saturn electrostatic discharges: Atmospheric storms
Important properties of the recently discovered Saturn electrostatic discharges are entirely consistent with an extended lightning storm system in Saturn's atmosphere. The presently favored B-ring location is ruled out
TAUOLA as tau Monte Carlo for future applications
The status of the Monte Carlo programs for the simulation of tau-lepton
production and decay in high-energy accelerator experiments is reviewed. In
particular, the status of the following packages is discussed: (i) TAUOLA for
tau-lepton decay, (ii) PHOTOS for radiative corrections in decays, (iii)
MC-TESTER packages for various types of semi-automatic tests, and (iv)
universal interface of TAUOLA for the decay of tau leptons produced by `any'
generator. Emphasis is put on recent developments for high-precision tests and
extensions of PHOTOS. Some considerations for the software organization
necessary in future applications for Belle and BaBar will be given; examples of
TAUOLA universal interface use will only be listed at the end of the review.Comment: 7 pages, 2 figure, Presented at International workshop on Tau Lepton
Physics, TAU04 Nara, Japan September 14-17,200
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
Evidence for a distant ( 8700 R sub J) Jovian magnetotail: Voyager 2 observations
A correlative survey of magnetometer (MAG) and Planetary Radio Astronomy (PRA) 1.2 kHz continuum radiation measurements from Voyager 2 provide evidence for at least eight distant Jovian magnetotail sightings occurring about once a month over the first 2/3 of 1981 at distances of approximately 5,000 to 9,000 R sub J. The occurrences of these events are in good agreement with prior Plasma Wave Science and Plasma Science identifications. Observations of these distant magnetotail, or tail filament, encounters appear most prevalent in both MAC and PRA data sets when the spacecraft was closest to the Jupiter-Sun axis at approximately 6,500 R sub J from the planet; the PRA events are also most intense during those times. A specific tail encounter occurring in mid-February 1981 is analyzed and shown to possess a remarkably symmetric magnetic field signature and to have a bipolar field structure in the central region. The bipolarity is characteristic of most of the eight events
- …