4,190 research outputs found
Hadron production in heavy ion collisions: Fragmentation and recombination from a dense parton phase
We discuss hadron production in heavy ion collisions at RHIC. We argue that
hadrons at transverse momenta P_T < 5 GeV are formed by recombination of
partons from the dense parton phase created in central collisions at RHIC. We
provide a theoretical description of the recombination process for P_T > 2 GeV.
Below P_T = 2 GeV our results smoothly match a purely statistical description.
At high transverse momentum hadron production is well described in the language
of perturbative QCD by the fragmentation of partons. We give numerical results
for a variety of hadron spectra, ratios and nuclear suppression factors. We
also discuss the anisotropic flow v_2 and give results based on a flow in the
parton phase. Our results are consistent with the existence of a parton phase
at RHIC hadronizing at a temperature of 175 MeV and a radial flow velocity of
0.55c.Comment: 25 pages LaTeX, 18 figures; v2: some references updated; v3: some
typos fixe
High Energy Nuclear Collisions: Theory Overview
We review some basic concepts of Relativistic Heavy Ion Physics and discuss
our understanding of some key results from the experimental program at the
Relativistic Heavy Ion Collider (RHIC). We focus in particular on the early
time dynamics of nuclear collisions, some result from lattice QCD, hard probes
and photons.Comment: 11 pages, 3 figures; delivered at ISNP 2009, published in Praman
Recombination Models
We review the current status of recombination and coalescence models that
have been successfully applied to describe hadronization in heavy ion
collisions at RHIC energies. Basic concepts as well as actual implementations
of the idea are discussed. We try to evaluate where we stand in our
understanding at the moment and what remains to be done in the future.Comment: Plenary Talk at Quark Matter 2004, submitted to J. Phys. G, 8 pages,
3 figure
Corticospinal beta-band synchronization entails rhythmic gain modulation
Rhythmic synchronization of neurons in the beta or gamma band occurs almost ubiquitously, and this synchronization has been linked to numerous nervous system functions. Many respective studies make the implicit assumption that neuronal synchronization affects neuronal interactions. Indeed, when neurons synchronize, their output spikes reach postsynaptic neurons together, trigger coincidence detection mechanisms, and therefore have an enhanced impact. There is ample experimental evidence demonstrating this consequence of neuronal synchronization, but beyond this, beta/gamma-band synchronization within a group of neurons might also modulate the impact of synaptic input to that synchronized group. This would constitute a separate mechanism through which synchronization affects neuronal interactions, but direct in vivo evidence for this putative mechanism is lacking. Here, we demonstrate that synchronized beta-band activity of a neuronal group modulates the efficacy of synaptic input to that group in-phase with the beta rhythm. This response modulation was not an addition of rhythmic activity onto the average response but a rhythmic modulation of multiplicative input gain. Our results demonstrate that beta-rhythmic activity of a neuronal target group multiplexes input gain along the rhythm cycle. The actual gain of an input then depends on the precision and the phase of its rhythmic synchronization to this target, providing one mechanistic explanation for why synchronization modulates interactions
Performance of cardiac output measurement derived from arterial pressure waveform analysis in patients undergoing triple-H-therapy of cerebral vasospasms after subarachnoidal hemorrhage
Pair production by boost-invariant fields in comoving coordinates
We derive the pair-production probability in a constant electric field in
Rindler coordinates in a quasi-classical approximation. Our result is different
from the pair-production probability in an inertial frame (Schwinger formula).
In particular, it exhibits non-trivial dependence on rapidity and deviation
from Gaussian behavior at small transverse momenta. Our results can be
important for analysis of particle production in heavy-ion collisions.Comment: 12 pages, 2 figures. Discussion added and typos fixe
Hadronization in heavy ion collisions: recombination or fragmentation?
We show that hadron production in relativistic heavy ion collisions at
transverse momenta larger than 2 GeV/c can be explained by the competition of
two different hadronization mechanisms. Above 5 GeV/c hadron production can be
described by fragmentation of partons that are created perturbatively. Below 5
GeV/c recombination of partons from the dense and hot fireball dominates. This
can explain some of the surprising features of RHIC data like the constant
baryon-to-meson ratio of about one and the small nuclear suppression for
baryons between 2 to 4 GeV/c.Comment: Contribution to the 7th Conference on Strange Quark Matter (SQM
2003), submitted to J.Phys.G; 6 pages LaTeX, 4 eps figures, uses iopart.cl
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Infrared, UV/VIS and Raman Spectroscopy of Comet Wild-2 Samples Returned by the Stardust Mission
Results from the preliminary examination of Stardust samples obtained using various spectroscopic methods will be presented
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