5,104 research outputs found
Pion Interferometry From A Relativistic Fluid With A First Order Phase Transition In CERN-SPS 158 GeV/A Pb+Pb Collisions
We investigate pion source sizes through the Yano-Koonin-Podgoretski\u{\i}
(YKP) parametrization for the Hanbury-Brown Twiss (HBT) effect in the CERN-SPS
158 GeV/A central collisions. We calculate two-particle correlation functions
numerically based on a (3+1)-dimensional relativistic hydrodynamics with a
first order phase transition and analyze the pair momentum dependence of the
HBT radii extracted from the YKP parametrization in detail. We find that even
in the case of a first order phase transition, expansion and the surface
dominant freeze-out make the source in the hydrodynamical model opaque
significantly. Consequently, the interpretation of the temporal radius
parameter as the time duration becomes unavailable for the hydrodynamical
model.Comment: 5 pages, LaTeX with six eps figures, Contribution to 'International
Workshop XXVIII on Gross Properties of Nuclei And Nuclear Excitations'.
Hirchegg, Austria, Jan 16-22, 200
Helical mode conversion using conical reflector
In a recent paper, Mansuripur et al. [Phys. Rev. A 84, 033813 (2011)]
indicated and numerically verified the generation of the helical wavefront of
optical beams using a conical-shape reflector. Because the optical reflection
is largely free from chromatic aberrations, the conical reflector has an
advantage of being able to manipulate the helical wavefront with broadband
light such as white light or short light pulses. In this study, we introduce
geometrical understanding of the function of the conical reflector using the
spatially-dependent geometric phase, or more specifically, the spin redirection
phase. We also present a theoretical analysis based on three-dimensional matrix
calculus and elucidate relationships of the spin, orbital, and total angular
momenta between input and output beams. These analyses are very useful when
designing other optical devices that utilize spatially-dependent spin
redirection phases. Moreover, we experimentally demonstrate the generation of
helical beams from an ordinary Gaussian beam using a metallic conical-shape
reflector.Comment: 7 pages, 7 figure
Effect of Maceration on \u3ci\u3ein Sacco\u3c/i\u3e Degradability and Energy Content of Low-Moisture Round Bale Alfalfa Silage
The aim of this study was to determine the effect of maceration on in sacco degradability and energy content of low-moisture alfalfa (Medicago sativa L.) silage. The results of two treatments were compared: 1) maceration, in which the alfalfa was processed through a large- scale forage mat maker prior to wilting to approximately 50% DM content (FM treatment), and 2) conventional conditioning, in which the alfalfa was tedded and wilted to the same DM content as that in the FM treatment (CC treatment). Silage bales were chopped in 20-mm pieces for each experiment. In sacco degradabilities of DM, CP and NDF of silage stems were estimated with two fistulated cows incubated for 3, 6, 12, 24, 48 and 72 h. DE and ME contents of FM- and CC-treated silage were measured using a respiration chamber with two dry cows. In sacco DM degradability was similar for both FM- and CC- treated silage, but CP degradability of FM-treated silage was higher than that of CC-treated silage. There were no differences between FM- and CC-treated silage in DE, ME and TDN contents. These results suggested that maceration increased the degradable fraction of CP in the alfalfa stem. However, in chopped silage, maceration has no effects on digestibility and metabolizability of energy
Hadronization in heavy ion collisions: Recombination and fragmentation of partons
We argue that the emission of hadrons with transverse momentum up to about 5
GeV/c in central relativistic heavy ion collisions is dominated by
recombination, rather than fragmentation of partons. This mechanism provides a
natural explanation for the observed constant baryon-to-meson ratio of about
one and the apparent lack of a nuclear suppression of the baryon yield in this
momentum range. Fragmentation becomes dominant at higher transverse momentum,
but the transition point is delayed by the energy loss of fast partons in dense
matter.Comment: 4 pages, 2 figures; v2: reference [8] added; v3: Eq.(2) corrected,
two references added, version to appear in PR
Live imaging of whole mouse embryos during gastrulation : migration analyses of epiblast and mesodermal cells
During gastrulation in the mouse embryo, dynamic cell movements including epiblast invagination and mesodermal layer expansion lead to the establishment of the three-layered body plan. The precise details of these movements, however, are sometimes elusive, because of the limitations in live imaging. To overcome this problem, we developed techniques to enable observation of living mouse embryos with digital scanned light sheet microscope (DSLM). The achieved deep and high time-resolution images of GFP-expressing nuclei and following 3D tracking analysis revealed the following findings: (i) Interkinetic nuclear migration (INM) occurs in the epiblast at embryonic day (E)6 and 6.5. (ii) INM-like migration occurs in the E5.5 embryo, when the epiblast is a monolayer and not yet pseudostratified. (iii) Primary driving force for INM at E6.5 is not pressure from neighboring nuclei. (iv) Mesodermal cells migrate not as a sheet but as individual cells without coordination
Charge diffusion constant in hot and dense hadronic matter - A Hadro-molecular-dynamic calculation
We evaluate charge diffusion constant of dense and hot hadronic matter based
on the molecular dynamical method by using a hadronic collision generator which
describes nuclear collisions at energies 10 < E < 100 GeV/A and satisfies
detailed balance at low temperatures (T < 200 MeV). For the hot and dense
hadronic matter of the temperature range, 100 < T < 200 MeV and baryon number
density, 0.16 < nB < 0.32 fm^-3, charge diffusion constant D gradually
increases from 0.5 fm c to 2 fm c with temperature and is almost independent of
baryon number density. Based on the obtained diffusion constant we make simple
discussions on the diffusion of charge fluctuation in ultrarelativistic nuclear
collisions.Comment: 13 pages, 4 figure
Angular hadron correlations probing the early medium evolution
Hard processes are a well calibrated probe to study heavy-ion collisions.
However, the information to be gained from the nuclear suppression factor R_AA
is limited, hene one has to study more differential observables to do medium
tomography. The angular correlations of hadrons associated with a hard trigger
appear suitable as they show a rich pattern when going from low p_T to high
p_T. Of prime interest is the fate of away side partons with an in-medium
pathlength O(several fm). At high p_T the correlations become dominated by the
punchtrough of the away side parton with subsequent fragmentation. We discuss
what information about the medium density can be gained from the data.Comment: Talk given at the 19th International Conference on Ultrarelativistic
Nucleus-Nucleus Collisions: Quark Matter 2006 (QM 2006), Shanghai, China,
14-20 Nov 200
Evolution of mechanism of parton energy loss with transverse momentum at RHIC and LHC in relativistic collision of heavy nuclei
We analyze the suppression of particle production at large transverse momenta
in ( most) central collisions of gold nuclei at
200 GeV and lead nuclei at 2.76 TeV. Full
next-to-leading order radiative corrections at , and
nuclear effects like shadowing and parton energy loss are included. The parton
energy loss is implemented in a simple multiple scattering model, where the
partons lose an energy per collision, where
is their mean free path. We take for a treatment
which is suggestive of the Bethe Heitler (BH) mechanism of incoherent
scatterings, for LPM mechanism, and
constant for a mechanism which suggests that the rate of energy loss ()
of the partons is proportional to total path length () of the parton in the
plasma, as the formation time of the radiated gluon becomes much larger than
.
We find that while the BH mechanism describes the nuclear modification factor
for 5 GeV/ (especially at RHIC energy), the LPM
and more so the constant mechanism provides a good description at
larger . This confirms the earlier expectation that the energy loss
mechanism for partons changes from BH to LPM for ,
where 1 fm and 1 GeV is the average
transverse kick-squared received by the parton per collision. The energy loss
per collision at the =2.76 TeV is found to be about
twice of that at 0.2 TeV.Comment: Discussion expanded, additional references added, 14 pages, 6
figures, To appear in Journal of Physics
- âŠ