1,286 research outputs found
Fitted HBT radii versus space-time variances in flow-dominated models
The inability of otherwise successful dynamical models to reproduce the ``HBT
radii'' extracted from two-particle correlations measured at the Relativistic
Heavy Ion Collider (RHIC) is known as the ``RHIC HBT Puzzle.'' Most comparisons
between models and experiment exploit the fact that for Gaussian sources the
HBT radii agree with certain combinations of the space-time widths of the
source which can be directly computed from the emission function, without
having to evaluate, at significant expense, the two-particle correlation
function. We here study the validity of this approach for realistic emission
function models some of which exhibit significant deviations from simple
Gaussian behaviour. By Fourier transforming the emission function we compute
the 2-particle correlation function and fit it with a Gaussian to partially
mimic the procedure used for measured correlation functions. We describe a
novel algorithm to perform this Gaussian fit analytically. We find that for
realistic hydrodynamic models the HBT radii extracted from this procedure agree
better with the data than the values previously extracted from the space-time
widths of the emission function. Although serious discrepancies between the
calculated and measured HBT radii remain, we show that a more
``apples-to-apples'' comparison of models with data can play an important role
in any eventually successful theoretical description of RHIC HBT data.Comment: 12 pages, 16 color figure
Tilted Pion Sources from Azimuthally Sensitive HBT Interferometry
Intensity interferometry in noncentral heavy ion collisions provides access
to novel information on the geometry of the effective pion-emitting source. We
demonstrate analytically that, even for vanishing pair momentum, the cross
terms and of the HBT correlation function in general show
a strong first harmonic in their azimuthal dependence. The strength of this
oscillation characterizes the tilt of the major axis of the spatial emission
ellipsoid away from the direction of the beam. Event generator studies indicate
that this tilt can be large (>20 degrees) at AGS energies which makes it by far
the most significant azimuthally sensitive HBT signal at these energies.
Moreover, transport models suggest that for pions this spatial tilt is directed
opposite to the tilt of the directed flow ellipsoid in momentum space. A
measurement of the azimuthal dependence of the HBT cross terms and
thus probes directly the physical origin of directed pion flow.Comment: submitted to Phys. Rev. Lett; revised version has some wording
changes/clarification, finer binning in q leads to tiny changes in Fig. 2,
one new referenc
Symmetry constraints for the emission angle dependence of Hanbury Brown--Twiss radii
We discuss symmetry constraints on the azimuthal oscillations of two-particle
correlation (Hanbury Brown--Twiss interferometry) radii for non-central
collisions between equal spherical nuclei. We also propose a new method for
correcting in a model-independent way the emission angle dependent correlation
function for finite event plane resolution and angular binning effects.Comment: 8 pages revtex4, 2 tables, no figures. Short Section VI added and
correction algorithm in Section VII made more explicit. Submitted to Physical
Review
Photon HBT interferometry for non-central heavy-ion collisions
Currently, the only known way to obtain experimental information about the
space-time structure of a heavy-ion collision is through 2-particle momentum
correlations. Azimuthally sensitive HBT interferometry (Hanbury Brown-Twiss
intensity interferometry) can complement elliptic flow measurements by
constraining the spatial deformation of the source and its time evolution.
Performing these measurements on photons allows us to access the fireball
evolution at earlier times than with hadrons. Using ideal hydrodynamics to
model the space-time evolution of the collision fireball, we explore
theoretically various aspects of 2-photon intensity interferometry with
transverse momenta up to 2 GeV, in particular the azimuthal angle dependence of
the HBT radii in non-central collisions. We highlight the dual nature of
thermal photon emission, in both central and non-central collisions, resulting
from the superposition of QGP and hadron resonance gas photon production. This
signature is present in both the thermal photon source function and the HBT
radii extracted from Gaussian fits of the 2-photon correlation function.Comment: 18 pages, 12 figure
Beam Energy Evolution of HBT Systematics at the AGS
We present preliminary results of the first pion interferometry (HBT)
excitation function at intermediate AGS energies. The beam energy evolution of
the correlations' dependence on mT, centrality, and emission angle with respect
to the reaction plane are discussed. Comparisons with predictions of the RQMD
cascade model are made.Comment: to appear in proceedings of Quark Matter '9
Describing transverse dynamics and space-time evolution at RHIC in a hydrodynamic model with statistical hadronization
A hydrodynamic model coupled to the statistical hadronization code
Therminator is used to study a set of observables in the soft sector at RHIC. A
satisfactory description of the pT-spectra and elliptic flow is obtained,
similarly to other hydrodynamic models. With the Gaussian initial conditions
the transverse femtoscopic radii are also reproduced, providing a possible
solution of the RHIC HBT puzzle.Comment: to appear in the conference proceedings for Quark Matter 2009, March
30 - April 4, Knoxville, Tennesse
The use of ultrasonic measurements assessed with two probes in live lambs for predicting the carcass composition
The accuracy of the use of two probes (UST-586-5 MHz and UST-556 tu-7.5 MHz) for
predicting the carcass composition were used in 36 lambs of Churra Bragançana breed
ranging in body weight from 26 to 47kg. Comparison between the ultrasonic
measurements assessed in live lambs with the same measurements taken on carcass were
established. The best relationship obtained were between the ultrasonic measurements
assessed with 7.5 MHz probe on last rib and the same fat thickness measurements taken
on carcass. Between 41 and 86tm of the variation in the weight of carcass components
were accounted for by variation in body weight and the ultrasonic measurements
Hydrodynamic emission of strange and non-strange particles at RHIC and LHC
The hydrodynamic model is used to describe the single-particle spectra and
elliptic flow of hadrons at RHIC and to predict the emission angle dependence
of HBT correlations at RHIC and LHC energies.Comment: 6 pages LaTeX, 3 postscript figures. Proceedings for the conference
"Strange Quark Matter 2003", Atlantic Beach, NC, March 12-17, 2003, to appear
in J. Phys.
Emission angle dependent pion interferometry at RHIC and beyond
We use hydrodynamics to generate freeze-out configurations for non-central
heavy-ion collisions at present and future collider energies. Such collisions
are known to produce strong elliptic flow. The accompanying space-time
structure of the source at freeze-out is analyzed using pion interferometry.
Between RHIC and LHC energies the source deformation in the transverse plane
changes sign. This leaves characteristic signatures in the emission angle
dependence of the HBT radii.Comment: Minor changes (some references and discussion added), accepted by
Physics Letters
Intracellular localization of Crimean-Congo Hemorrhagic Fever (CCHF) virus glycoproteins
BACKGROUND: Crimean-Congo Hemorrhagic Fever virus (CCHFV), a member of the genus Nairovirus, family Bunyaviridae, is a tick-borne pathogen causing severe disease in humans. To better understand the CCHFV life cycle and explore potential intervention strategies, we studied the biosynthesis and intracellular targeting of the glycoproteins, which are encoded by the M genome segment. RESULTS: Following determination of the complete genome sequence of the CCHFV reference strain IbAr10200, we generated expression plasmids for the individual expression of the glycoproteins G(N )and G(C), using CMV- and chicken β-actin-driven promoters. The cellular localization of recombinantly expressed CCHFV glycoproteins was compared to authentic glycoproteins expressed during virus infection using indirect immunofluorescence assays, subcellular fractionation/western blot assays and confocal microscopy. To further elucidate potential intracellular targeting/retention signals of the two glycoproteins, GFP-fusion proteins containing different parts of the CCHFV glycoprotein were analyzed for their intracellular targeting. The N-terminal glycoprotein G(N )localized to the Golgi complex, a process mediated by retention/targeting signal(s) in the cytoplasmic domain and ectodomain of this protein. In contrast, the C-terminal glycoprotein G(C )remained in the endoplasmic reticulum but could be rescued into the Golgi complex by co-expression of G(N). CONCLUSION: The data are consistent with the intracellular targeting of most bunyavirus glycoproteins and support the general model for assembly and budding of bunyavirus particles in the Golgi compartment
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