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 $z \to 1$ 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 $R_M^{h}$ 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

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