160,721 research outputs found
Fragmentation or Recombination at High p_T?
All hadronization processes, including fragmentation, are shown to proceed
through recombination. The shower partons in a jet turn out to play an
important role in describing the p_T spectra of hadrons produced in heavy-ion
collisions. Due to the recombination of the shower partons with the soft
thermal partons, the structure of jets produced in AA collisions is not the
same as that of jets produced in pp collisions.Comment: Talk given at Quark Matter 200
Tracking 3-D body motion for docking and robot control
An advanced method of tracking three-dimensional motion of bodies has been developed. This system has the potential to dynamically characterize machine and other structural motion, even in the presence of structural flexibility, thus facilitating closed loop structural motion control. The system's operation is based on the concept that the intersection of three planes defines a point. Three rotating planes of laser light, fixed and moving photovoltaic diode targets, and a pipe-lined architecture of analog and digital electronics are used to locate multiple targets whose number is only limited by available computer memory. Data collection rates are a function of the laser scan rotation speed and are currently selectable up to 480 Hz. The tested performance on a preliminary prototype designed for 0.1 in accuracy (for tracking human motion) at a 480 Hz data rate includes a worst case resolution of 0.8 mm (0.03 inches), a repeatability of plus or minus 0.635 mm (plus or minus 0.025 inches), and an absolute accuracy of plus or minus 2.0 mm (plus or minus 0.08 inches) within an eight cubic meter volume with all results applicable at the 95 percent level of confidence along each coordinate region. The full six degrees of freedom of a body can be computed by attaching three or more target detectors to the body of interest
Perturbative calculation of the scaled factorial moments in second-order quark-hadron phase transition within the Ginzburg-Landau description
The scaled factorial moments are studied for a second-order
quark-hadron phase transition within the Ginzburg-Landau description. The role
played by the ground state of the system under low temperature is emphasized.
After a local shift of the order parameter the fluctuations are around the
ground state, and a perturbative calculation for can be carried out.
Power scaling between 's is shown, and a universal scaling exponent
is given for the case with weak correlations and weak
self-interactions.Comment: 12 pages in RevTeX, 12 eps figure
The power of VNA-driven quasi-optics to sense group molecular action in condensed phase systems
© © 20xx IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.The authors would like to thank the Engineering and Physical Sciences Research Council (EPSRC, UK) for generous support (EP/1014845)
Accurate determination of terahertz optical constants by vector network analyzer of Fabry-Perot response
This paper was published in Optics Letters and is made available as an electronic reprint with the permission of OSA. The paper can be found at the following URL on the OSA website: http://dx.doi.org/10.1364/OL.38.005438. Systematic or multiple reproduction or distribution to multiple locations via electronic or other means is prohibited and is subject to penalties under law.We present a method based on a Fabry-Perot model to efficiently and accurately estimate optical constants of wafer samples in transmission-only measurements performed by a vector network analyzer (VNA). The method is demonstrated on two separate wafer samples: one of silicon and the other of polymethylmethacrylate. Results show that the method can not only acquire optical constants accurately and simply over a broad frequency domain but also overcome the limitations of calculation for dispersive and lossy materials to which existing methods are susceptible, such as those based on VNA-driven quasi-optical transmissometers and terahertz time-domain spectrometry
Current experimental constraints on NMSSM with large lambda
The next-to-minimal supersymmetric model (NMSSM) with a large lambda (the
mixing parameter between the singlet and doublet Higgs fields) is well
motivated since it can significantly push up the upper bound on the SM-like
Higgs boson mass to solve the little hierarchy problem. In this work we examine
the current experimental constraints on the NMSSM with a large lambda, which
include the direct search for Higgs boson and sparticles at colliders, the
indirect constraints from precision electroweak measurements, the cosmic dark
matter relic density, the muon anomalous magnetic moment, as well as the
stability of the Higgs potential. We find that, with the increase of lambda,
parameters like tan-beta, M_A, mu and M_2 are becoming more stringently
constrained. It turns out that the maximal reach of lambda is limited by the
muon anomalous magnetic moment, and for smuon masses of 200 GeV (500 GeV) the
parameter space with lambda > 1.5 (0.6) is excluded.Comment: Version in PRD (figs and discussions added
Recent La Plata basin drought conditions observed by satellite gravimetry
The Gravity Recovery and Climate Experiment (GRACE) provides quantitative
measures of terrestrial water storage (TWS) change. GRACE data show a
significant decrease in TWS in the lower (southern) La Plata river basin of
South America over the period 2002-2009, consistent with recognized drought
conditions in the region. GRACE data reveal a detailed picture of temporal and
spatial evolution of this severe drought event, which suggests that the drought
began in lower La Plata in around austral spring 2008 and then spread to the
entire La Plata basin and peaked in austral fall 2009. During the peak, GRACE
data show an average TWS deficit of ~12 cm (equivalent water layer thickness)
below the 7 year mean, in a broad region in lower La Plata. GRACE measurements
are consistent with accumulated precipitation data from satellite remote
sensing and with vegetation index changes derived from Terra satellite
observations. The Global Land Data Assimilation System model captures the
drought event but underestimates its intensity. Limited available
groundwater-level data in southern La Plata show significant groundwater
depletion, which is likely associated with the drought in this region.
GRAC-observed TWS change and precipitation anomalies in the studied region
appear to closely correlate with the ENSO climate index, with dry and wet
seasons corresponding to La Ni\~na and El Ni\~no events, respectively
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