88 research outputs found
Correlated Emission of Hadrons from Recombination of Correlated Partons
We discuss different sources of hadron correlations in relativistic heavy ion
collisions. We show that correlations among partons in a quasi-thermal medium
can lead to the correlated emission of hadrons by quark recombination and argue
that this mechanism offers a plausible explanation for the dihadron
correlations in the few GeV/c momentum range observed in Au+Au collisions at
RHIC.Comment: 4 pages, 2 figures; v2: typo on p.4 correcte
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
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
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
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
Neutron diffraction and magnetic properties of CoCrTiAl Heusler alloys
We report the structural, magnetic, and magnetocaloric properties of
CoCrTiAl ( 0--0.5) Heusler alloys for spintronic and
magnetic refrigerator applications. Room temperature X-ray diffraction and
neutron diffraction patterns along with Rietveld refinements confirm that the
samples are of single phase and possess a cubic structure. Interestingly,
magnetic susceptibly measurements indicate a second order phase transition from
paramagnetic to ferromagnetic where the Curie temperature (T) of
CoCrAl increases from 330~K to 445~K with Ti substitution. Neutron powder
diffraction data of the 0 sample across the magnetic phase transition
taken in a large temperature range confirm the structural stability and exclude
the possibility of antiferromagnetic ordering. The saturation magnetization of
the 0 sample is found to be 8000~emu/mol (1.45~/{\it f.u.})
at 5~K, which is in good agreement with the value (1.350.05~/{\it f.u.}) obtained from the Rietveld analysis of the neutron powder
diffraction pattern measured at temperature of 4~K. By analysing the
temperature dependence of the neutron data of the 0 sample, we find that
the change in the intensity of the most intense Bragg peak (220) is consistent
with the magnetization behavior with temperature. Furthermore, an enhancement
of change in the magnetic entropy and relative cooling power values has been
observed for the 0.25 sample. Interestingly, the critical behavior
analysis across the second order magnetic phase transition and extracted
exponents ( 0.496, 1.348, and
3.71 for the 0.25 sample) suggest the presence of long-range ordering,
which deviates towards 3D Heisenberg type interactions above T,
consistent with the interaction range value .Comment: submitte
- …