4,172 research outputs found
Fragmentation or Recombination at High p_T?
All hadronization processes, including fragmentation, are shown to proceed
through recombination. The shower partons in a jet turn out to play an
important role in describing the p_T spectra of hadrons produced in heavy-ion
collisions. Due to the recombination of the shower partons with the soft
thermal partons, the structure of jets produced in AA collisions is not the
same as that of jets produced in pp collisions.Comment: Talk given at Quark Matter 200
Dihadron Correlation in Jets Produced in Heavy-Ion Collisions
The difference between the structures of jets produced in heavy-ion and
hadronic collisions can best be exhibited in the correlations between particles
within those jets. We study the dihadron correlations in jets in the framework
of parton recombination. Two types of triggers, and proton, are
considered. It is shown that the recombination of thermal and shower partons
makes the most important contribution to the spectra of the associated
particles at intermediate . In collisions the only significant
contribution arises from shower-shower recombination, which is negligible in
heavy-ion collisions. Moments of the associated-particle distributions are
calculated to provide simple summary of the jet structures for easy comparison
with experiments.Comment: 24 pages in Latex + 5 figure
Ridge Formation Induced by Jets in Collisions at 7 TeV
An interpretation of the ridge phenomenon found in pp collisions at 7 TeV is
given in terms of enhancement of soft partons due to energy loss of semihard
jets. A description of ridge formation in nuclear collisions can directly be
extended to pp collisions, since hydrodynamics is not used, and azimuthal
anisotropy is generated by semihard scattering. Both the p_T and multiplicity
dependencies are well reproduced. Some suggestions are made about other
observables.Comment: Expanded version to be published in Phys. Rev.
The Role of Gluon Depletion in J/psi Suppression
The depletion of gluons as the parton flux traverses a nucleus in a heavy-ion
collision can influence the production rate of heavy-quark states. Thus the
suppression of can be due to gluon depletion in the initial state in
addition to nuclear and hadronic absorption in the final state. A formalism is
developed to describe the depletion effect. It is shown that, without
constraints from other experimental facts beside the suppression data
in and collisions, it is not possible to determine the relative
importance of depletion vs absorption. Possible relevance to the enhanced
suppression seen in the data is mentioned but not studied.Comment: 12 pages + 2 figures (in ps file), LaTex, Submitted to Phys. Rev.
Optimal transportation, topology and uniqueness
The Monge-Kantorovich transportation problem involves optimizing with respect
to a given a cost function. Uniqueness is a fundamental open question about
which little is known when the cost function is smooth and the landscapes
containing the goods to be transported possess (non-trivial) topology. This
question turns out to be closely linked to a delicate problem (# 111) of
Birkhoff [14]: give a necessary and sufficient condition on the support of a
joint probability to guarantee extremality among all measures which share its
marginals. Fifty years of progress on Birkhoff's question culminate in Hestir
and Williams' necessary condition which is nearly sufficient for extremality;
we relax their subtle measurability hypotheses separating necessity from
sufficiency slightly, yet demonstrate by example that to be sufficient
certainly requires some measurability. Their condition amounts to the vanishing
of the measure \gamma outside a countable alternating sequence of graphs and
antigraphs in which no two graphs (or two antigraphs) have domains that
overlap, and where the domain of each graph / antigraph in the sequence
contains the range of the succeeding antigraph (respectively, graph). Such
sequences are called numbered limb systems. We then explain how this
characterization can be used to resolve the uniqueness of Kantorovich solutions
for optimal transportation on a manifold with the topology of the sphere.Comment: 36 pages, 6 figure
Parton and Hadron Correlations in Jets
Correlation between shower partons is first studied in high jets. Then
in the framework of parton recombination the correlation between pions in
heavy-ion collisions is investigated. Since thermal partons play very different
roles in central and peripheral collisions, it is found that the correlation
functions of the produced hadrons behave very differently at different
centralities, especially at intermediate . The correlation function that
can best exhibit the distinctive features is suggested. There is not a great
deal of overlap between what we can calculate and what has been measured.
Nevertheless, some aspects of our results compare favorably with experimental
data.Comment: 28 pages in Latex + 13 figures. This is a revised version with
extended discussions added without quantitative changes in the result
Evolution of shower parton distributions in a jet from quark recombination model
The evolution of shower parton distributions in a jet is investigated in the
framework of quark recombination model. The distributions are parameterized and
the dependence of the parameters is given by polynomials of for
a wide range of .Comment: 5 pages in RevTeX, 3 figures in ep
Charm Correlation as a Diagnostic Probe of Quark Matter
The use of correlation between two open-charm mesons is suggested to give
information about the nature of the medium created in heavy-ion collisions.
Insensitivity to the charm production rate is achieved by measuring normalized
cumulant. The acollinearity of the D momenta in the transverse plane is a
measure of the medium effect. Its dependence on nuclear size or E_T provides a
signature for the formation of quark matter.Comment: 12 pages, no figure
Critical Behavior of Hadronic Fluctuations and the Effect of Final-State Randomization
The critical behaviors of quark-hadron phase transition are explored by use
of the Ising model adapted for hadron production. Various measures involving
the fluctuations of the produced hadrons in bins of various sizes are examined
with the aim of quantifying the clustering properties that are universal
features of all critical phenomena. Some of the measures involve wavelet
analysis. Two of the measures are found to exhibit the canonical power-law
behavior near the critical temperature. The effect of final-state randomization
is studied by requiring the produced particles to take random walks in the
transverse plane. It is demonstrated that for the measures considered the
dependence on the randomization process is weak. Since temperature is not a
directly measurable variable, the average hadronic density of a portion of each
event is used as the control variable that is measurable. The event-to-event
fluctuations are taken into account in the study of the dependence of the
chosen measures on that control variable. Phenomenologically verifiable
critical behaviors are found and are proposed for use as a signature of
quark-hadron phase transition in relativistic heavy-ion collisions.Comment: 17 pages (Latex) + 24 figures (ps file), submitted to Phys. Rev.
Factorial Moments of Continuous Order
The normalized factorial moments are continued to noninteger values of
the order , satisfying the condition that the statistical fluctuations
remain filtered out. That is, for Poisson distribution for all .
The continuation procedure is designed with phenomenology and data analysis in
mind. Examples are given to show how can be obtained for positive and
negative values of . With being continuous, multifractal analysis is
made possible for multiplicity distributions that arise from self-similar
dynamics. A step-by-step procedure of the method is summarized in the
conclusion.Comment: 15 pages + 9 figures (figures available upon request), Late
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