64 research outputs found
QCD Saturation and Deuteron-Nucleus Collisions
We make quantitative predictions for the rapidity and centrality dependencies
of hadron multiplicities in dA collisions at RHIC basing on the ideas of parton
saturation in the Color Glass Condensate.Comment: 16 pages, 5 figures; added Erratum with a discussion of centrality
selection procedure and comparison to the published experimental result
Particle Correlations in Saturated QCD Matter
We study quantitatively angular correlations in the two-particle spectrum
produced by an energetic probe scattering off a dense hadronic target with
sizeable saturation momentum. To this end, two parton inclusive cross sections
for arbitrary projectiles with small color charge density are derived in the
eikonal formalism. Our results are the following: For large momenta of the
observed particles, the perturbative limit with characteristic back-to-back
correlation is recovered. As the trigger momenta get closer to the saturation
scale Q_s, the angular distribution broadens. When the momenta are
significantly smaller than Q_s, the azimuthal distribution is broad but still
peaked back-to-back. However, in a narrow momentum range (0.5 - 1.5) Q_s, we
observe that the azimuthal correlation splits into a double peak with maxima
displaced away from 180 degree. We argue that it is the soft multiple
scattering physics that is responsible for the appearance of this shift in the
angle of maximal correlation. We also point out that when the physical size of
the projectile is particularly small, the double peak structure persists in a
significantly wider range of final state momenta.Comment: 28 pages LaTex, 7 eps-figure
Gluon saturation effects on J/Psi production in heavy ion collisions
We consider a novel mechanism for J/Psi production in nuclear collisions
arising due to the high density of gluons. We calculate the resulting J/Psi
production cross section as a function of rapidity and centrality. We evaluate
the nuclear modification factor and show that the rapidity distribution of the
produced J/Psi's is significantly more narrow in AA collisions due to the gluon
saturation effects. Our results indicate that gluon saturation in the colliding
nuclei is a significant source of J/Psi suppression that can be disentangled
from the quark-gluon plasma effects.Comment: 5 pages, 3 figures; v2: typos corrected; presentation improve
Charmed hadron production in high-energy nuclear collisions
We present a new model for the description of heavy-flavor hadronization in
high-energy nuclear (and possibly hadronic) collisions, where the process takes
place not in the vacuum, but in the presence of other color charges. We explore
its effect on the charmed hadron yields and kinematic distributions once the
latter is applied at the end of transport calculations used to simulate the
propagation of heavy quarks in the deconfined fireball produced in nuclear
collisions. The model is based on the formation of color-singlet clusters
through the recombination of charm quarks with light antiquarks or diquarks
from the same fluid cell. This local mechanism of color neutralization leads to
a strong space-momentum correlation, which provides a substantial enhancement
of charmed baryon production -- with respect to expectations based on
collisions -- and of the collective flow of all charmed hadrons. We also
discuss the similarities between our model and recently developed mechanisms
implemented in QCD event generators to simulate medium corrections to
hadronization in the presence of other nearby color charges.Comment: 6 pages, proceedings of ICHEP-2022. arXiv admin note: substantial
text overlap with arXiv:2209.0423
Heavy-flavor transport and hadronization in pp collisions
Recent experimental results on the Lambda_c/D^0 ratio in proton-proton
collisions have revealed a significant enhancement compared to expectations
based on universal fragmentation fractions/functions across different colliding
systems, from e+e- to pp. This unexpected enhancement has sparked speculation
about the potential effects of a deconfined medium impacting hadronization,
previously considered exclusive to heavy-ion collisions. In this study, we
propose a novel approach that assumes the formation of a small, deconfined, and
expanding fireball even in pp collisions, where charm quarks can undergo
rescattering and hadronization. We make use of the same in-medium hadronization
mechanism developed for heavy-ion collisions, which involves local
color-neutralization through recombination of charm quarks with nearby opposite
color charges from the background fireball. Our model incorporates the presence
of diquark excitations in the hot medium, which promotes the formation of
charmed baryons. Moreover, the recombination process, involving closely aligned
partons from the same fluid cell, effectively transfers the collective flow of
the system to the final charmed hadrons. We show that this framework can
qualitatively reproduce the observed experimental findings in heavy-flavor
particle-yield ratios, -spectra and elliptic-flow coefficients. Our
results provide new, complementary supporting evidence that the collective
phenomena observed in small systems naturally have the same origin as those
observed in heavy-ion collision
The onset of classical QCD dynamics in relativistic heavy ion collisions
The experimental results on hadron production obtained recently at RHIC offer
a new prospective on the energy dependence of the nuclear collision dynamics.
In particular, it is possible that parton saturation -- the phenomenon likely
providing initial conditions for the multi--particle production at RHIC
energies -- may have started to set in central heavy ion collisions already
around the highest SPS energy. We examine this scenario, and make predictions
based on high density QCD for the forthcoming 22 GeV run at RHIC.Comment: 4 pages, 2 figures, revte
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