74,198 research outputs found
Properties of the top quark
Recent measurements of top-quark properties at the LHC and the Tevatron are
presented. Most recent measurements of the top quark mass have been carried out
by CMS using fb of TeV data including the study of the
dependence on event kinematics. ATLAS uses the full Run I data at TeV for a "3D" measurement that significantly reduces systematic
uncertainties. D0 employs the full Run II data using the matrix element method
to measure the top quark mass with significantly reduced systematic
uncertainties. Many different measurements of the top quark exist to date and
the most precise ones per decay channel per experiment have been combined into
the first world combination with a relative precision of 0.44%. Latest updates
of measurements of production asymmetries include the measurement of the \ttbar
production asymmetry by D0 employing the full Run II data set, by CMS and ATLAS
(including the polarization of the top quark) employing both the full data set
at TeV. CMS uses the full TeV data to measure the
top quark polarization in single top production, the ratio of the
branching fractions
and to search for flavor changing neutral currents. The results from all these
measurements agree well with their respective Standard Model expectation.Comment: Large Hadron Collider Physics (LHCP) conference held at Columbia
University in New York City from June 2-7, 201
125 GeV Higgs as a pseudo-Goldstone boson in supersymmetry with vector-like matters
We propose a possibility of the 125 GeV Higgs being a pseudo-Goldstone boson
in supersymmetry with extra vector-like fermions. Higgs mass is obtained from
loops of top quark and vector-like fermions from the global symmetry breaking
scale f at around TeV. The mu, Bmu/mu \sim f are generated from the dynamics of
global symmetry breaking and the Higgs quartic coupling vanishes at f as tan
beta \simeq 1. The relation of msoft \sim with f \sim mu \sim m_soft
\sim TeV is obtained and large mu does not cause a fine tuning for the
electroweak symmetry breaking. The Higgs to di-photon rate can be enhanced from
the loop of uncolored vector-like matters. The stability problem of Higgs
potential with vector-like fermions can be nicely cured by the UV completion
with the Goldstone picture.Comment: 28 pages, 8 figure
Transistorized Marx bank pulse circuit provides voltage multiplication with nanosecond rise-time
Base-triggered avalanche transistor circuit used in a Marx bank pulser configuration provides voltage multiplication with nanosecond rise-time. The avalanche-mode transistors replace conventional spark gaps in the Marx bank. The delay time from an input signal to the output signal to the output is typically 6 nanoseconds
Universal Ratios of Characteristic Lengths in Semidilute Polymer Solutions
We use experimental and simulation data from the literature to infer five
characteristic lengths, denoted , , , , and
of a semidilute polymer solution. The first two of these are defined in
terms of scattering from the solution, the third is defined in terms of osmotic
pressure, the fourth by the spatial monomer concentration profile, and the last
by co-operative diffusion. In a given solution the ratios of any of these five
lengths are expected to be universal constants. Knowing these constants thus
allows one to use one measured property of a solution as a means of inferring
others. We calculate these ratios and estimate their uncertainties for
solutions in theta as well as good-solvent conditions. The analysis is
strengthened by use of scattering properties of isolated polymers inferred from
computer simulations.Comment: 15 pages(pdf), to be submitted to Macromolecules or J. Chem. Phy
Brain Control of Movement Execution Onset Using Local Field Potentials in Posterior Parietal Cortex
The precise control of movement execution onset is essential for safe and autonomous cortical motor prosthetics. A recent study from the parietal reach region (PRR) suggested that the local field potentials (LFPs) in this area might be useful for decoding execution time information because of the striking difference in the LFP spectrum between the plan and execution states (Scherberger et al., 2005). More specifically, the LFP power in the 0–10 Hz band sharply rises while the power in the 20–40 Hz band falls as the state transitions from plan to execution. However, a change of visual stimulus immediately preceded reach onset, raising the possibility that the observed spectral change reflected the visual event instead of the reach onset. Here, we tested this possibility and found that the LFP spectrum change was still time locked to the movement onset in the absence of a visual event in self-paced reaches. Furthermore, we successfully trained the macaque subjects to use the LFP spectrum change as a "go" signal in a closed-loop brain-control task in which the animals only modulated the LFP and did not execute a reach. The execution onset was signaled by the change in the LFP spectrum while the target position of the cursor was controlled by the spike firing rates recorded from the same site. The results corroborate that the LFP spectrum change in PRR is a robust indicator for the movement onset and can be used for control of execution onset in a cortical prosthesis
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