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 ($0-5$ most) central collisions of gold nuclei at $\sqrt{s_\textrm{NN}}=$ 200 GeV and lead nuclei at $\sqrt{s_{\textrm{NN}}}=$ 2.76 TeV. Full next-to-leading order radiative corrections at ${\cal{O}}(\alpha_s^3)$, 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 $\epsilon=\lambda \times dE/dx$ per collision, where $\lambda$ is their mean free path. We take $\epsilon=\kappa E$ for a treatment which is suggestive of the Bethe Heitler (BH) mechanism of incoherent scatterings, $\epsilon = \sqrt{\alpha E}$ for LPM mechanism, and $\epsilon=$ constant for a mechanism which suggests that the rate of energy loss ($dE/dx$) of the partons is proportional to total path length ($L$) of the parton in the plasma, as the formation time of the radiated gluon becomes much larger than $L$. We find that while the BH mechanism describes the nuclear modification factor $R_{\textrm{AA}}$ for $p_T \leq$ 5 GeV/$c$ (especially at RHIC energy), the LPM and more so the constant $dE/dx$ mechanism provides a good description at larger $p_T$. This confirms the earlier expectation that the energy loss mechanism for partons changes from BH to LPM for $p_T \ge \lambda$, where $\lambda \approx$ 1 fm and $\approx$ 1 GeV$^2$ is the average transverse kick-squared received by the parton per collision. The energy loss per collision at the $\sqrt{s_\textrm{NN}}$ =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