2,247 research outputs found
The CP properties of the lightest Higgs boson with sbottom effects
In the framework of the recently proposed gluino-axion model, using the
effective potential method and taking into account the top-stop as well as the
bottom-sbottom effects, we discuss the CP--properties of the lightest Higgs
boson, in particular its CP--odd composition, which can offer new opportunities
at collider searches. It is found that although the CP-odd composition of the
lightest Higgs increases slightly with the inclusion of the sbottom effects, it
never exceeds %0.17 for all values of the renormalization scale Q ranging from
top mass to TeV scaleComment: 24 pp, 12 eps fig
A Clinically Relevant Method of Analyzing Continuous Change in Robotic Upper Extremity Chronic Stroke Rehabilitation
Background. Robots designed for rehabilitation of the upper extremity after stroke facilitate high rates of repetition during practice of movements and record precise kinematic data, providing a method to investigate motor recovery profiles over time. Objective. To determine how motor recovery profiles during robotic interventions provide insight into improving clinical gains. Methods. A convenience sample (n = 22), from a larger randomized control trial, was taken of chronic stroke participants completing 12 sessions of arm therapy. One group received 60 minutes of robotic therapy (Robot only) and the other group received 45 minutes on the robot plus 15 minutes of translation-to-task practice (Robot + TTT). Movement time was assessed using the robot without powered assistance. Analyses (ANOVA, random coefficient modeling [RCM] with 2-term exponential function) were completed to investigate changes across the intervention, between sessions, and within a session. Results. Significant improvement (P < .05) in movement time across the intervention (pre vs post) was similar between the groups but there were group differences for changes between and within sessions (P < .05). The 2-term exponential function revealed a fast and slow component of learning that described performance across consecutive blocks. The RCM identified individuals who were above or below the marginal model. Conclusions. The expanded analyses indicated that changes across time can occur in different ways but achieve similar goals and may be influenced by individual factors such as initial movement time. These findings will guide decisions regarding treatment planning based on rates of motor relearning during upper extremity stroke robotic interventions
How Finely Tuned is Supersymmetric Dark Matter?
We introduce a quantification of the question in the title: the logarithmic
sensitivity of the relic neutralino density Omega-hsquared to variations in
input parameters such as the supersymmetric mass scales m_0, m_1/2 and A_0, tan
beta and the top and bottom quark masses. In generic domains of the CMSSM
parameter space with a relic density in the preferred range 0.1 <
Omega-hsquared < 0.3, the sensitivities to all these parameters are moderate,
so an interesting amount of supersymetric dark matter is a natural and robust
prediction. Within these domains, the accuracy in measuring the CMSSM and other
input parameters at the LHC may enable the relic density to be predicted quite
precisely. However, in the coannihilation regions, this might require more
information on the supersymetric spectrum than the LHC is able to provide.
There are also exceptional domains, such as those where direct-channel pole
annihilation dominates, and in the `focus-point' region, where the logarithmic
sensitivity to the input parameters is greatly increased, and it would be more
difficult to predict Omega-hsquared accurately.Comment: 14 pages, 2 eps figure
Bounds on the Higgs-Boson Mass in the Presence of Non-Standard Interactions
The triviality and vacuum stability bounds on the Higgs-boson mass are
revisited in the presence of new interactions parameterized in a
model-independent way by an effective lagrangian. When the scale of new physics
is below 50 TeV the triviality bound is unchanged but the stability lower bound
is increased by 40-60 GeV. Should the Higgs-boson mass be close to its current
lower experimental limit, this leads to the possibility of new physics at the
scale of a few TeV, even for modest values of the effective lagrangian
parameters.Comment: 5 pages, 2 figures, RevTex, submitted to PR
Sneutrino Mass Measurements at e+e- Linear Colliders
It is generally accepted that experiments at an e+e- linear colliders will be
able to extract the masses of the selectron as well as the associated
sneutrinos with a precision of ~ 1% by determining the kinematic end points of
the energy spectrum of daughter electrons produced in their two body decays to
a lighter neutralino or chargino. Recently, it has been suggested that by
studying the energy dependence of the cross section near the production
threshold, this precision can be improved by an order of magnitude, assuming an
integrated luminosity of 100 fb^-1. It is further suggested that these
threshold scans also allow the masses of even the heavier second and third
generation sleptons and sneutrinos to be determined to better than 0.5%. We
re-examine the prospects for determining sneutrino masses. We find that the
cross sections for the second and third generation sneutrinos are too small for
a threshold scan to be useful. An additional complication arises because the
cross section for sneutrino pair to decay into any visible final state(s)
necessarily depends on an unknown branching fraction, so that the overall
normalization in unknown. This reduces the precision with which the sneutrino
mass can be extracted. We propose a different strategy to optimize the
extraction of m(\tilde{\nu}_\mu) and m(\tilde{\nu}_\tau) via the energy
dependence of the cross section. We find that even with an integrated
luminosity of 500 fb^-1, these can be determined with a precision no better
than several percent at the 90% CL. We also examine the measurement of
m(\tilde{\nu}_e) and show that it can be extracted with a precision of about
0.5% (0.2%) with an integrated luminosity of 120 fb^-1 (500 fb^-1).Comment: RevTex, 46 pages, 15 eps figure
Direct Higgs production and jet veto at the Tevatron and the LHC in NNLO QCD
We consider Higgs boson production through gluon--gluon fusion in hadron
collisions, when a veto is applied on the transverse momenta of the
accompanying hard jets. We compute the QCD radiative corrections to this
process at NLO and NNLO. The NLO calculation is complete. The NNLO calculation
uses the recently evaluated NNLO soft and virtual QCD contributions to the
inclusive cross section. We find that the jet veto reduces the impact of the
NLO and NNLO contributions, the reduction being more sizeable at the LHC than
at the Tevatron.Comment: 22 pages, 12 postscript figure
Reaction mechanism and characteristics of T_{20} in d + ^3He backward elastic scattering at intermediate energies
For backward elastic scattering of deuterons by ^3He, cross sections \sigma
and tensor analyzing power T_{20} are measured at E_d=140-270 MeV. The data are
analyzed by the PWIA and by the general formula which includes virtual
excitations of other channels, with the assumption of the proton transfer from
^3He to the deuteron. Using ^3He wave functions calculated by the Faddeev
equation, the PWIA describes global features of the experimental data, while
the virtual excitation effects are important for quantitative fits to the
T_{20} data. Theoretical predictions on T_{20}, K_y^y (polarization transfer
coefficient) and C_{yy} (spin correlation coefficient) are provided up to GeV
energies.Comment: REVTEX+epsfig, 17 pages including 6 eps figs, to be published in
Phys. Rev.
An Alternative Method to Obtain the Quark Polarization of the Nucleon
An alternate method is described to extract the quark contribution to the
spin of the nucleon directly from the first moment of the deuteron structure
function, . It is obtained without recourse to the use of input on the
nucleon wave function from hyperon decays involving the flavor symmetry
parameters, F and D. The result for the quark polarization of the nucleon,
is in good agreement with the values of the singlet axial
current matrix element, , obtained from recent next-to-leading order
analyses of current proton, neutron and deuteron data.Comment: 7 pages, 1 figur
Formula for proton-nucleus reaction cross section at intermediate energies and its application
We construct a formula for proton-nucleus total reaction cross section as a
function of the mass and neutron excess of the target nucleus and the proton
incident energy. We deduce the dependence of the cross section on the mass
number and the proton incident energy from a simple argument involving the
proton optical depth within the framework of a black sphere approximation of
nuclei, while we describe the neutron excess dependence by introducing the
density derivative of the symmetry energy, L, on the basis of a radius formula
constructed from macroscopic nuclear models. We find that the cross section
formula can reproduce the energy dependence of the cross section measured for
stable nuclei without introducing any adjustable energy dependent parameter. We
finally discuss whether or not the reaction cross section is affected by an
extremely low density tail of the neutron distribution for halo nuclei.Comment: 7 pages, 4 figures, added reference
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