Nuclear effects in the Drell-Yan process at very high energies

We study Drell-Yan (DY) dilepton production in proton(deuterium)-nucleus and in nucleus-nucleus collisions within the light-cone color dipole formalism. This approach is especially suitable for predicting nuclear effects in the DY cross section for heavy ion collisions, as it provides the impact parameter dependence of nuclear shadowing and transverse momentum broadening, quantities that are not available from the standard parton model. For p(D)+A collisions we calculate nuclear shadowing and investigate nuclear modification of the DY transverse momentum distribution at RHIC and LHC for kinematics corresponding to coherence length much longer than the nuclear size. Calculations are performed separately for transversely and longitudinally polarized DY photons, and predictions are presented for the dilepton angular distribution. Furthermore, we calculate nuclear broadening of the mean transverse momentum squared of DY dileptons as function of the nuclear mass number and energy. We also predict nuclear effects for the cross section of the DY process in heavy ion collisions. We found a substantial nuclear shadowing for valence quarks, stronger than for the sea.Comment: 46 pages, 18 figures, title changed and some discussion added, accepted for publication in PR

Nonperturbative Effects in Gluon Radiation and Photoproduction of Quark Pairs

We introduce a nonperturbative interaction for light-cone fluctuations containing quarks and gluons. The $\bar qq$ interaction squeezes the transverse size of these fluctuations in the photon and one does not need to simulate this effect via effective quark masses. The strength of this interaction is fixed by data. Data on diffractive dissociation of hadrons and photons show that the nonperturbative interaction of gluons is much stronger. We fix the parameters for the nonperturbative quark-gluon interaction by data for diffractive dissociation to large masses (triple-Pomeron regime). This allows us to predict nuclear shadowing for gluons which turns out to be not as strong as perturbative QCD predicts. We expect a delayed onset of gluon shadowing at $x \leq 10^{-2}$ shadowing of quarks. Gluon shadowing turns out to be nearly scale invariant up to virtualities $Q^2\sim 4 GeV^2$ due to presence of a semihard scale characterizing the strong nonperturbative interaction of gluons. We use the same concept to improve our description of gluon bremsstrahlung which is related to the distribution function for a quark-gluon fluctuation and the interaction cross section of a $\bar qqG$ fluctuation with a nucleon. We expect the nonperturbative interaction to suppress dramatically the gluon radiation at small transverse momenta compared to perturbative calculations.Comment: 58 pages of Latex including 11 figures. Shadowing for soft gluons and Fig. 6 are added as well as a few reference

Calculations of binding energies and masses of heavy quarkonia using renormalon cancellation

We use various methods of Borel integration to calculate the binding ground energies and masses of b-bbar and t-tbar quarkonia. The methods take into account the leading infrared renormalon structure of the hard+soft part of the binding energies E(s), and of the corresponding quark pole masses m_q, where the contributions of these singularities in M(s) = 2 m_q + E(s) cancel. Beforehand, we carry out the separation of the binding energy into its hard+soft and ultrasoft parts. The resummation formalisms are applied to expansions of m_q and E(s) in terms of quantities which do not involve renormalon ambiguity, such as MSbar quark mass, and alpha_s. The renormalization scales are different in calculations of m_q, E(s) and E(us). The MSbar mass of b quark is extracted, and the binding energies of t-tbar and the peak (resonance) energies for (t+tbar) production are obtained.Comment: 23 pages, 8 double figures, revtex4; the version to appear in Phys.Rev.D; extended discussion between Eqs.(25) and (26); the paragraph between Eqs.(32) and (33) is new and explains the numerical dependence of the residue parameter on the factorization scale; several new references were added; acknowledgments were modified; the numerical results are unchange

S-band electron linac with beam energy of 30…100 MeV

The S-band electron linac has been designed at NSC KIPT to cover an energy range from 30 to 100 MeV. The linac consists of the injector based on evanescent oscillations and the two four-meter long piecewise homogeneous accelerating sections. Each section is supplied with RF power from the KIU-12AM klystron. Variation of mean energy of the beam over a wide range is produced by placing bunches out of the wave crest in the second accelerating section. The report presents layout of the linac as well as simulation results of self-consistent particle dynamics in the linac and its present status.Лінійний прискорювач електронів 10 см - діапазону було розроблено в ННЦ ХФТІ з метою перекрити діапазон енергій 30…100 MeВ. Прискорювач складається з інжектора, основаного на коливаннях, що не розповсюджуються, і двох шматково-однорідних чотириметрових прискорювальних секцій. Кожна секція забезпечується НВЧ-потужністю від клістрона KІУ-12AM. Зміна середньої енергії пучка в широких межах забезпечується прискоренням згустків не на гребені хвилі в другій прискорювальній секції. Представлено структурну схему прискорювача, результати моделювання динаміки частинок в прискорювачі і його поточний стан.Линейный ускоритель электронов 10 см - диапазона был разработан в ННЦ ХФТИ с целью перекрытия диапазона энергий 30…100 MэВ. Ускоритель состоит из инжектора, основанного на не распространяющихся колебаниях и двух кусочно-однородных четырехметровых ускоряющих секций. Каждая секция питается СВЧ-мощностью от клистрона KИУ-12AM. Изменение средней энергии пучка в широких пределах обеспечивается ускорением сгустков не на гребне волны во второй ускоряющей секции. Представлены структурная схема ускорителя, результаты моделирования динамики частиц в ускорителе и его текущее состояние

QCD corrections for heavy quark effects at LEP/SLC and NLC

Fleischer J, Avdeev LV, Tarasov OV. QCD corrections for heavy quark effects at LEP/SLC and NLC. 1994

ПСИХОЛОГИЧЕСКИЕ ОСОБЕННОСТИ АДАПТАЦИИ К ОБУЧЕНИЮ В ВУЗЕ У СТУДЕНТОВ МЛАДШИХ КУРСОВ

This article discusses the psychological characteristics of adaptation to learning in high School for undergraduate students. With the help ofdiagnostic methods of social and psychological adaptation of K. Rogers and R. diamond, test of anxiety research (spielberger questionnaire), "Methods of determining stress resistance and social adaptation" Holmes and rage conducted a comparative study of the characteristics of psychological adaptation of students of 1-2 courses. It is possible to allocate rather extensive number of interpretations of the term "adaptation", both narrow, and in wide senses which reduce value ofprocess of adaptation to the phenomena, both biochemical level, and social. Close attention in relation to such problems, in our opinion, should be paid to educational activities, in which a special frequency acquire problems of adaptation, as one of the varieties of social adaptation to educational activities in undergraduate students. As a rule, the first years in higher education are especially important in terms of adaptation of students to study at the University. Further professional development of young specialists in the future depends on the success or failure of adaptation to training at the University from Junior courses.В данной статье рассматриваются психологические особенности адаптации к обучению в ВУЗе у студентов младших курсов. При помощи методик диагностики социально-психологической адаптации К. Роджерса и Р. Даймонда, теста исследования тревожности (опросник Спилбергера), «Методика определения стрессоустойчивости и социальной адаптации»Холмса и Раге проведено сравнительное исследование характеристик психологической адаптации студентов 1-2 курсов. Можно выделить достаточно обширное количество трактовок термина «адаптация», как узком, так и в широком смыслах, которые сводят значение процесса адаптации к явлениям, как биохимического уровня, так и социального. Пристальное внимание в отношении подобных проблем, на наш взгляд, нужно уделить в отношении образовательной деятельности, в рамках которой особую частоту приобретают проблемы адаптации, как одной из разновидностей социальной адаптации, к учебной деятельности у студентов младших курсов. Как правило, именно первые годы в высшем учебном заведении особенно важны с точки зрения адаптации студентов к обучению в вузе. От успешности или неуспешности адаптации к обучению в вузе с младших курсов зависит дальнейшее профессиональное становление молодых специалистов в будущем