15,841 research outputs found
Proof of Factorization of Fragmentation Function in Non-Equilibrium QCD
In this paper we prove factorization of fragmentation function in
non-equilibrium QCD by using Schwinger-Keldysh closed-time path integral
formalism. We use the background field method of QCD in a pure gauge in path
integral approach to prove factorization of fragmentation function in
non-equilibrium QCD. Our proof is valid in any arbitrary gauge fixing parameter
. This may be relevant to study hadron production from quark-gluon
plasma at high energy heavy-ion colliders at RHIC and LHC.Comment: 13 pages latex, (Final Published Version, Annals of Physics
Proton-proton physics in ALICE
The ALICE experiment has several unique features which makes it an important contributor to proton-proton physics at the LHC, in addition to its specific design goal of studying the physics of strongly interacting matter in heavy-ion collisions. The unique capabilities include its low transverse momentum (\pT) acceptance, excellent vertexing, particle identification over a broad \pT range and jet reconstruction. In this report, a brief review of ALICE capabilities is given for studying bulk properties of produced particles which characterize the underlying events, and the physics of heavy-flavour, quarkonia, photons, di-leptons and jets
Renormalization Group Equation and QCD Coupling Constant in the Presence of SU(3) Chromo-Electric Field
We solve renormalization group equation in QCD in the presence of SU(3)
constant chromo-electric field E^a with arbitrary color index a=1,2,...8 and
find that the QCD coupling constant \alpha_s depends on two independent
casimir/gauge invariants C_1=[E^aE^a] and C_2=[d_{abc}E^aE^bE^c]^2 instead of
one gauge invariant C_1=[E^aE^a]. The \beta function is derived from the
one-loop effective action. This coupling constant may be useful to study hadron
formation from color flux tubes/strings at high energy colliders and to study
quark-gluon plasma formation at RHIC and LHC.Comment: 13 pages latex, 4 eps figs, Eur. Phys. J.
Schwinger Mechanism for Gluon Pair Production in the Presence of Arbitrary Time Dependent Chromo-Electric Field
We study Schwinger mechanism for gluon pair production in the presence of
arbitrary time-dependent chromo-electric background field with
arbitrary color index =1,2,...8 in SU(3) by directly evaluating the path
integral. We obtain an exact expression for the probability of non-perturbative
gluon pair production per unit time per unit volume and per unit transverse
momentum from arbitrary . We show that the
tadpole (or single gluon) effective action does not contribute to the
non-perturbative gluon pair production rate . We find
that the exact result for non-perturbative gluon pair production is independent
of all the time derivatives where
and has the same functional dependence on two casimir invariants
and as the constant
chromo-electric field result with the replacement: . This
result may be relevant to study the production of a non-perturbative
quark-gluon plasma at RHIC and LHC.Comment: 13 pages latex, Published in European Physical Journal
Photons from Nucleus-Nucleus Collisions at Ultra-Relativistic Energies
We compare the photon emission rates from hot hadronic matter with in-medium
mass shift and Quark Gluon Plasma (QGP). It is observed that the WA98 data can
be well reproduced by hadronic initial state with initial temperature MeV if the universal scaling of temperature dependent hadronic masses are
assumed and the evolution of temperature with time is taken from transport
model or (3+1) dimensional hydrodynamics. The data can also be reproduced by
QGP initial state with similar initial temperature and non-zero initial radial
velocity.Comment: Talk given in the International Nuclear Physics Conference, at the
University of California, Berkeley, USA, during July 30 - August 3, 200
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Recent Advances in Treatment of Primary Central Nervous System Lymphoma
Opinion statement Therapeutic options are limited in primary central nervous system lymphoma (PCNSL) with no uniform consensus on optimal management and few published, randomized trials. High-dose methotrexate in combination with other chemotherapeutic agents forms the mainstay of treatment. There hasn’t been much progress beyond high-dose methotrexate in this disease, and although results from trials using high-dose chemotherapy and autologous stem-cell transplant seem promising, these need to be further validated. Moreover, the role of whole brain radiation in the upfront setting remains to be determined. However, international efforts in this direction are underway, with ongoing randomized trials in newly diagnosed PCNSL, more research on the molecular pathogenesis and biomarkers, and the use of novel agents in salvage therapy. There also is emphasis on quality of life parameters and neurocognitive status. Future treatment options should optimize high-efficacy rates while minimizing the risk of neurotoxicity
Color Octet Contribution to High p_T J/\Psi Production in pp Collisions at \sqrt s = 500 and 200 GeV at RHIC
We compute \frac{d\sigma}{dp_T} of the J/\psi production in pp collisions at
RHIC at \sqrt s = 500 and 200 GeV by using both the color octet and singlet
models in the framework of non-relativistic QCD. The J/\psi we compute here
includes the direct J/\psi from the partonic fusion processes and the J/\psi
coming from the radiative decays of \chi_J's both in the color octet and
singlet channel. The high p_T J/\psi production cross section is computed
within the PHENIX detector acceptance ranges: -0.35 < \eta < 0.35 and 1.2 <
\|\eta| < 2.4, the central electron and forward muon arms. It is found that the
color octet contribution to J/\psi production is dominant at RHIC energy in
comparison to the color singlet contributions. We compare our results with the
recent preliminary data obtained by PHENIX detector for the high p_T J/\psi
measurements. While the color singlet model fails to explain the data
completely the color octet model is in agreement with the single data point
above 2 GeV transverse momentum. A measurement of J/\psi production at RHIC in
the next run with better statistics will allow us to determine the validity of
the color octet model of J/\psi production at RHIC energies. This is very
important because it is necessary to know the exact mechanism for J/\psi
production in pp collisions at RHIC if one is to make predictions of J/\psi
suppression as a signature of quark-gluon plasma. These mechanisms also play an
important role in determining the polarized spin structure function of the
proton at RHIC.Comment: 16 pages latex, 6 figure
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