2,936 research outputs found
Parton Propagation and Fragmentation in QCD Matter
We review recent progress in the study of parton propagation, interaction and
fragmentation in both cold and hot strongly interacting matter. Experimental
highlights on high-energy hadron production in deep inelastic lepton-nucleus
scattering, proton-nucleus and heavy-ion collisions, as well as Drell-Yan
processes in hadron-nucleus collisions are presented. The existing theoretical
frameworks for describing the in-medium interaction of energetic partons and
the space-time evolution of their fragmentation into hadrons are discussed and
confronted to experimental data. We conclude with a list of theoretical and
experimental open issues, and a brief description of future relevant
experiments and facilities.Comment: Invited review paper for "Rivista del Nuovo Cimento". 112 pages, 67
figures, 13 table
First results from ALICE
The Large Hadron Collider provides p-p and Pb-Pb collisions at the highest centre-of-mass energies to date, which allow to study high-pT particle, jet and heavy-quark properties in a new energy regime. We present first results from both p-p and Pb-Pb collisions that provide a first characterization of the properties of the matter formed in these collisions
Azimuthal Asymmetries: Access to Novel Structure Functions
One of the most interesting consequence of non-zero intrinsic transverse
momentum of partons in the nucleon is the nontrivial azimuthal dependence of
the cross section of hard scattering processes. Many of the observable
asymmetries contain unknown functions which provide essential information on
the quark and gluon structure. Several of them have been studied in the last
few years; we discuss their qualitative and quantitative features in
semi-inclusive DIS.Comment: 6 pages, LaTeX, 7 eps figures, Talk presented at the 15th
International Spin Physics Symposium, Spin 2002, Brookhaven National
Laboratory, September 9-14, 200
Higher Twist Effects in Deep Inelastic Scattering on Nuclei
Particle production in deep inelastic scattering on nuclei is reduced due to
absorption of the produced particles in the nucleus. The photon ejects a quark
from a bound nucleon which propagates through the nucleus forming a prehadron
before turning into a hadron. We calculate the higher twist effect in
hadronization which dominates the region of fragmentation.Comment: Based on a talk given by H.J. Pirner at the Fifth International
Conference on Perspectives in Hadronic Physics, Trieste, May 200
Probe Initial Parton Density and Formation Time via Jet Quenching
Medium modification of jet fragmentation function due to multiple scattering
and induced gluon radiation leads directly to jet quenching or suppression of
leading particle distribution from jet fragmentation. One can extract an
effective total parton energy loss which can be related to the total transverse
momentum broadening. For an expanding medium, both are shown to be sensitive to
the initial parton density and formation time. Therefore, one can extract the
initial parton density and formation time from simultaneous measurements of
parton energy loss and transverse momentum broadening. Implication of the
recent experimental data on effects of detailed balance in parton energy loss
is also discussed.Comment: 4 pages, 2 figures, talk at Quark Matter 2002, 16th International
Conference on Ultrarelativistic Nucleus-nucleus Collisions, Nantes, July
18-24, 200
Hadron Formation in DIS in a nuclear environment
The influence of the nuclear medium on the production of charged hadrons in
semi-inclusive deep inelastic scattering has been studied by the HERMES
experiment at DESY using 27.5 GeV positrons.
A substantial reduction of the multiplicity of charged hadrons and identified
charged pions from nuclei relative to that from deuterium has been measured as
function of the relevant kinematic variables. The preliminary results on
krypton show a larger reduction of the multiplicity ratio with
respect to the one previously measured on nitrogen and suggest a possible
modification of the quark fragmentation process in the nuclear environment.Comment: 5 pages, 5 figures, Proceeding of DIS 2001, IX International Workshop
on Deep Inelastic Scattering Bologna, 27 April-1 May 200
Influence of seed coat color on germination rate and seedling development of Trifolium repens. Is physiological dormancy possible?
Trifolium repens L. (var. Regal Ladino) is among the most used species of Italian legumes as fodder
for pastures, for direct consumption, or as mowing for stocks and then pastures. The seed
integument of Trifolium repens L. has different colors ranging from light yellow to dark brown. In
this work, the physiology of germination of light-colored, light intermediate, dark and dark
intermediate seeds was studied to highlight any difference in the percentage of seed germination
and seedling development. The results showed a lower germination rate and a noticeable reduction
of the root length in dark seeds compared to light seeds. In this context, tests to exclude a
physiological dormancy of dark seeds were performed. Light microscope and scanning electron
microscope observation were conducted to detect substantial differences in the structure and
thickness of the integument and in the quality of reserves. Biochemical investigations have
evidenced that total polyphenols content is similar in all the seeds categories, while higher amount
of total flavonoids was detected in dark seeds. Total Polyphenols and flavonoids content decreased
during germination in all seed groups
Proces hadronizacije u duboko-neelastičnom raspršenju u eksperimentu HERMES
The influence of the nuclear medium on lepto-production of hadrons was studied in the HERMES experiment at DESY in semi-inclusive deep-inelastic scattering of 27.6 GeV and 12 GeV positrons off deuterium, and off light and heavy targets. The differential multiplicity for nuclei relative to that of deuterium has been measured for the first time for various identified hadrons (π +, π −, π 0 , K+, K−, p and ¯p) as a function of the virtual photon energy ν, the fraction z of this energy transferred to the hadron, and the hadron transverse momentum squared p 2 t .Proučavamo utjecaj nuklearne tvari na leptonsku tvorbu hadrona u mjerenju HERMES u DESYu poluinkluzivnim duboko-neelastičnim raspršenjem pozitrona energije 27.6 GeV i 12 GeV u deuteriju, te lakim i teškim metama. Načinili smo prva mjerenja omjera diferencijalne višestrukosti za jezgre u odnosu prema deuteriju za više utvrđenih hadrona (π +, π −, π 0 , K+, K−, p and ¯p) u ovisnosti o virtualnoj energiji fotona ν, dijela te energije z predane hadronu i kvadrata poprečnog impulsa pt2
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