4,415 research outputs found
High Pt hadron-hadron correlations
We propose the formulation of a dihadron fragmentation function in terms of
parton matrix elements. Under the collinear factorization approximation and
facilitated by the cut-vertex technique, the two hadron inclusive cross section
at leading order (LO) in e+ e- annihilation is shown to factorize into a short
distance parton cross section and the long distance dihadron fragmentation
function. We also derive the DGLAP evolution equation of this function at
leading log. The evolution equation for the non-singlet and singlet quark
fragmentation function and the gluon fragmentation function are solved
numerically with the initial condition taken from event generators.
Modifications to the dihadron fragmentation function from higher twist
corrections in DIS off nuclei are computed. Results are presented for cases of
physical interest.Comment: 7 pages, 8 figures, Latex, Proceedings of Hot Quarks 2004, July
18-24, Taos, New Mexic
A comparative study of Jet-quenching Schemes
The four major approximation schemes devised to study the modification of
jets in dense matter are outlined. The comparisons are restricted to basic
assumptions and approximations made in each case and the calculation
methodology used. Emergent underlying similarities between apparently disparate
methods brought about by the approximation schemes are exposed.
Parameterizations of the medium in each scheme are discussed in terms of the
transport coefficient . Discrepancies between the estimates obtained
from the four schemes are discussed. Recent developments in the basic theory
and phenomenology of energy loss are highlighted.Comment: 12 pages, 10 figures, latex, plenary presentation at the 19th
International Conference on Ultra-Relativistic Nucleus-Nucleus Collisions
(QM2006), Shanghai, China Nov. 14-20, 200
Evolution of Parton Fragmentation Functions at Finite Temperature
The first order correction to the parton fragmentation functions in a thermal
medium is derived in the leading logarithmic approximation in the framework of
thermal field theory. The medium-modified evolution equations of the parton
fragmentation functions are also derived. It is shown that all infrared
divergences, both linear and logarithmic, in the real processes are canceled
among themselves and by corresponding virtual corrections. The evolution of the
quark number and the energy loss (or gain) induced by the thermal medium are
investigated.Comment: 21 pages in RevTex, 10 figure
Nuclear Attenuation of high energy two-hadron system in the string model
Nuclear attenuation of the two-hadron system is considered in the string
model. The two-scale model and its improved version with two different choices
of constituent formation time and sets of parameters obtained earlier for the
single hadron attenuation, are used to describe available experimental data for
the -dependence of subleading hadron, whereas satisfactory agreement with
the experimental data has been observed. A model prediction for
-dependence of the nuclear attenuation of the two-hadron system is also
presented.Comment: 8 page
Charged Particle Production at Large Transverse Momentum in PbPb Collisions at TeV Measured with ALICE at the LHC
Transverse momentum () spectra of charged particles are measured as a
function of event centrality in PbPb collisions at TeV
with ALICE at the LHC. The spectra are compared to those measured in pp
collisions at the same collision energy in terms of the nuclear modification
factor . The high- charge particle production in central PbPb
collisions () is strongly suppressed by a factor at transverse
momenta GeV/c as compared to expectation from independent
superposition of nucleon-nucleon collisions. Above GeV/c there is a
significant rise in the nuclear modification factor, which reaches at GeV/c. The measured suppression of high-
particles is stronger than that measured at RHIC.Comment: 4 pages, 6 figures, Quark Matter 2011 Proceeding
Jet tomography
I summarize the recent advances in jet tomographic studies of cold and hot
nuclear matter based on perturbative QCD calculations of medium-induced gluon
bremsstrahlung. Quantitative applications to ultrarelativistic heavy ion
reactions at RHIC indicate the creation of a deconfined state of QCD with
initial energy density on the order of 100 times cold nuclear matter density.Comment: Plenary talk given at the seventeenth international conference on
Ultra-Relativistic Nucleus-Nucleus Collisions (Quark Matter 2004). 8 pages,
12 figures. Updated references, updated Table
Particle Production at Large Transverse Momentum with ALICE
We present transverse momentum distributions of inclusive charged particles
and identified hadrons in and Pb--Pb collisions at \rs= 2.76 TeV,
measured by ALICE at the LHC. The Pb--Pb data are presented in intervals of
collision centrality and cover transverse momenta up to 50 GeV/. Nuclear
medium effects are studied in terms of the nuclear modification factor \raa.
The results indicate a strong suppression of high- particles in Pb--Pb
collisions, consistent with a large energy loss of hard-scattered partons in
the hot, dense and long-lived medium created at the LHC. We compare the
preliminary results for inclusive charged particles to previous results from
RHIC and calculations from energy loss models. Furthermore, we compare the
nuclear modification factors of inclusive charged particles to those of
identified , , K, and .Comment: Talk given at Quark Matter 2011 conferenc
Multiparticle angular correlations: a probe for the sQGP at RHIC
A novel decomposition technique is used to extract the centrality dependence
of di-jet properties and yields from azimuthal correlation functions obtained
in Au+Au collisions at =200 GeV. The width of the
near-side jet shows very little dependence on centrality. In contrast, the
away-side jet indicates substantial broadening as well as hints for for a local
minimum at for central and mid-central events. The yield of
jet-pairs (per trigger particle) slowly increases with centrality for both the
near- and away-side jets. These observed features are compatible with several
recent theoretical predictions of possible modifications of di-jet
fragmentation by a strongly interacting medium. Several new experimental
approaches, including the study of flavor permutation and higher order
multi-particle correlations, that might help to distinguish between different
theoretical scenarios are discussed.Comment: Proceedings of the MIT workshop on correlations and fluctation
Dileptons from a Quark Gluon Plasma with Finite Baryon Density
We investigate the effects of a baryon-antibaryon asymmetry on the spectrum
of dileptons radiating from a quark gluon plasma. We demonstrate the existence
of a new set of processes in this regime. The dilepton production rate from the
corresponding diagrams is shown to be as important as that obtained from the
usual quark-antiquark annihilation.Comment: 20 pages, 5 figures, REVTEX. Typos corrected, references added.
Version accepted for publication in Physical Review
Jet Quenching in Heavy Ion Collisions
This review article was prepared for the Landolt-Boernstein volume on
Relativisitc Heavy Ion Physics.Comment: Review articel accepted for publication in the Landolt-Boernstein
Handbook of Physics, ed. R. Stock. 41 pages LaTex, 7 eps-figure
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