Cumulation and acceleration of ions by TW femtosecond laser pulse

A new method of ion cumulation and acceleration at three-dimensional compression of plasma in the ”light trap” created in the focal region of the high-power femtosecond laser is theoretically studied. The ”light trap” is formed by delay in time of the central part of the laser pulse being focused. The cumulation degree and maximum energy of acceleration ions depending on values of the high-power femtosecond laser pulse have been investigated by numerical methods. Physical mechanisms of ion density and energy increase in the paraxial plasma zone have been discussed. The proposed method of ion cumulation and acceleration allows one to create compact bright sources of fast neutrons, nuclei for x-ray and gamma lasers, and also provides the unique possibilities of nuclear reaction initiation and isotope production.Теоретично досліджен новий метод прискорення та кумуляції при трьохвимірному стисненні плазми в “світової пастці”, що утворюється в фокальної області потужного фемптосекундного лазера. “Світлова пастка” формується шляхом затримки центральної частини лазерного імпульсу. Чисельними методами вивчені степінь кумуляції та максимальна енергія іонів в залежності от параметрів потужного лазерного імпульсу. Запропонований метод кумуляції та прискорення іонів дозволяє розробити компактні джерела швидких нейтронів середовища для рентгенівського то гамма-лазерів, а також дає унікальні можливості ініціювання ядерних реакцій і отримання ізотопів.Теоретически исследован новый метод ускорения и кумуляции ионов при трехмерном обжатии плазмы в “световой ловушке”, создаваемой в фокальной области мощного фемтосекундного лазера. “Световая ловушка ” формируется путем задержки во времени центральной части фокусируемого импульса. Численными методами изучены степень кумуляции и максимальная энергия ускоренных ионов в зависимости от параметров мощного лазерного импульса. Обсуждены физические механизмы увеличения плотности и энергии ионов в приосевой области плазмы. Предложенный метод кумуляции и ускорения ионов позволяет создать компактные яркие источники быстрых нейтронов, среды для рентгеновского и гамма-лазеров, а также создает уникальные возможности инициирования ядерных реакций и получения изотопов

Pion form factor and QCD sum rules: case of axial current

We present an analysis of QCD sum rules for pion form factor in next-to-leading order of perturbation theory for the case of axial-vector pion currents. The theoretical predictions for Q^2-dependence of pion form factor are in good agreement with available experimental data. It is shown, that NLO corrections are large in this case and should be taken into account in rigorous theoretical analysis.Comment: LaTeX file, 10 pages, 5 figures, v2: added check of Ward identity constrains at Q^2=0, the continuum thresholds are determined to satisfy F_{\pi}(0)=1 condition with NLO accuracy, what led to \approx 10% reduction of our numerical estimates, references adde

Two-loop sunset diagrams with three massive lines

In this paper, we consider the two-loop sunset diagram with two different masses, m and M, at spacelike virtuality q^2 = -m^2. We find explicit representations for the master integrals and an analytic result through O(epsilon) in d=4-2epsilon space-time dimensions for the case of equal masses, m = M.Comment: 11 page

Nonforward anomalous dimensions of Wilson operators in N=4 super-Yang-Mills theory

We present the next-to-leading order results for universal non-forward anomalous dimensions of Wilson twist-2 operators in N=4 supersymmetric Yang-Mills theory. The whole calculation was performed using supersymmetric Ward identities derived in this paper together with already known QCD results and does not involve any additional calculation of diagrams. We also considered one particular limit of our result, which could potentially be interesting in the context of AdS/CFT correspondence.Comment: 15 pages, references added, typos corrected, version accepted in JHE

Doubly heavy baryons in sum rules of NRQCD

The masses of baryons containing two heavy quarks and their couplings to the corresponding quark currents are evaluated in the framework of NRQCD sum rules. The coulomb-like corrections in the system of doubly heavy diquark are taken into account, and the contribution of nonperturbative terms coming from the quark, gluon and mixed condensates as well as the product of quark and gluon condensates, is analyzed. The higher condensates destroy the factorization of baryon and diquark correlators and provide the convergency of sum rule method. As a result the accuracy of estimates is improved.Comment: 17 pages, LATEX file and 6 eps-figure

Three-loop universal anomalous dimension of the Wilson operators in N=4 SUSY Yang-Mills model

We present results for the three-loop universal anomalous dimension of Wilson twist-2 operators in the N=4 Supersymmetric Yang-Mills model. These results are obtained by extracting the most complicated contributions from the three loop non-singlet anomalous dimensions in QCD which were calculated recently. Their singularities at j=1 agree with the predictions obtained from the BFKL equation for N=4 SYM in the next-to-leading order. The asymptotics of universal anomalous dimension at large j is in an agreement with the expectations based on an interpolation between weak and strong coupling regimes in the framework of the AdS/CFT correspondence.Comment: LaTeX file, 13 pages, no figures. Some corrections, additional remarks and references. In the last version the analysis of anomalous dimension at j -> 2 was improve

Pion form factor and QCD sum rules: case of pseudoscalar current

We present an analysis of QCD sum rules for pion form factor in next-to-leading order of perturbation theory for the case of pseudoscalar pion currents. The essential instanton contribution is reanalysed with account for present more accurate values of parameters entering Single Instanton Approximation (SIA). The theoretical curve obtained for Q^2 dependence of pion form factor is in a good agreement with existing experimental data. To calculate NLO corrections for double spectral densities we developed an effective computational technic. The details of the method together with the results for pion form factor in a more theoretically clean case of axial interpolating currents will be presented elsewhere.Comment: LaTeX file, 12 pages, 5 figures, uses axodraw.st

Semileptonic B_c-meson decays in sum rules of QCD and NRQCD

The semileptonic B_c-meson decays into the heavy quarkonia J/\psi (\eta_c) and a pair of leptons are investigated in the framework of three-point sum rules of QCD and NRQCD. Calculations of analytical expressions for the spectral densities of QCD and NRQCD correlators with account for the Coulomb-like \alpha_s/v terms are presented. The generalized relations due to the spin symmetry of NRQCD for the form factors of B_c\to J/\psi (\eta_c)l\nu_l transitions with l denoting one of the leptons e, \mu or \tau, are derived at the recoil momentum close to zero. This allows one to express all NRQCD form factors through a single universal quantity, an analogue of Isgur-Wise function at the maximal invariant mass of lepton pair. The gluon condensate corrections to three-point functions are calculated both in full QCD in the Borel transform scheme and in NRQCD in the moment scheme. This enlarges the parameteric stability region of sum rule method, that makes the results of the approach to be more reliable. Numerical estimates of widths for the transitions of B_c\to J/\psi (\eta_c)l\nu_l are presented.Comment: 37 pages, Latex file, 10 figures, 15 epsf-insertions, revised version to appear in Nucl.Phys.

Experimental research and work development on the helium ions linac

The paper provides a brief summary of the experimental research carried out at the present time at the materials science complex developed at the NSC KIPT. The main directions for the development of the work carried out have been determined. The complex is based on a linear accelerator of helium ions. The features and advantages of the accelerating structure of the accelerator, which is based on the principle of APF, are described. A technique was developed and irradiation of candidate materials for the divertor and the first wall of the TNR was carried out. The damageability of the irradiated samples could create from 3 to 80 dpa.Наведений короткий виклад експериментальних досліджень, проведених на матеріалознавському радіаційному комплексі, розробленому в ННЦ ХФТІ. Комплекс базується на лінійному прискорювачі іонів гелію. Описані особливості та переваги прискорюючої структури, в основу якої покладений принцип зміннофазового фокусування (ЗФФ). Визначені основні напрямки розвитку досліджень. Розроблено методики та проведені опромінення різного типу конструкційних матеріалів та кандидатних матеріалів для дивертора і першої стінки ТЯР. Пошкоджуваність опромінених зразків в експериментах створювалася в межах 3…80 сна.Приведено краткое изложение экспериментальных исследований, проводимых на материаловедческом радиационном комплексе, разработанном в ННЦ ХФТИ. Комплекс базируется на линейном ускорителе ионов гелия. Описаны особенности и преимущества ускоряющей структуры, в основу которой положен принцип переменно-фазовой фокусировки (ПФФ). Определены основные направления развития исследований. Разработаны методики и проведены облучения разного типа конструкционных и кандидатных материалов для дивертора и первой стенки ТЯР. Повреждаемость облученных образцов в экспериментах создавалась в пределах 3…80 сна

Heavy mass expansion, light-by-light scattering and the anomalous magnetic moment of the muon

Contributions from light-by-light scattering to (g_\mu-2)/2, the anomalous magnetic moment of the muon, are mediated by the exchange of charged fermions or scalar bosons. Assuming large masses M for the virtual particles and employing the technique of large mass expansion, analytical results are obtained for virtual fermions and scalars in the form of a series in (m_\mu /M)^2. This series is well convergent even for the case M=m_\mu. For virtual fermions, the expansion confirms published analytical formulae. For virtual scalars, the result can be used to evaluate the contribution from charged pions. In this case our result confirms already available numerical evaluations, however, it is significantly more precise.Comment: revtex4, eps figure