Low-Energy Photodisintegration of the Deuteron and Big-Bang Nucleosynthesis

The photon analyzing power for the photodisintegration of the deuteron was measured for seven gamma-ray energies between 2.39 and 4.05 MeV using the linearly polarized gamma-ray beam of the High-Intensity Gamma-ray Source at the Duke Free-Electron Laser Laboratory. The data provide a stringent test of theoretical calculations for the inverse reaction, the neutron-proton radiative capture reaction at energies important for Big-Bang Nucleosynthesis. Our data are in excellent agreement with potential model and effective field theory calculations. Therefore, the uncertainty in the baryon density obtained from Big-Bang Nucleosynthesis can be reduced at least by 20%.Comment: 5 pages, 5 figure

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

Visible photoluminescence from SiOx films grown by low temperature plasma enhanced chemical vapor deposition

a-SiOx films of varying stoichiometry have been prepared by low temperature plasma enhanced chemical vapor deposition. The majority of films showed photoluminescence (PL) and films prepared in a narrow range of gas flows exhibited much stronger PL after annealing. Peak PL energies ranging from the ultraviolet to the near infrared have been observed. PL, infrared and X-ray diffraction on selected samples indicate formation of Si clusters in the films. The effects of annealing on the PL properties of the films have been found to depend on initial stoichiometry of the films. © 1995

An interactive procedure of a transverse beam matching and correction in INR Linac

An application package is developed to carry out an interactive procedure for a transverse beam matching and correction in INR Linac. The results of multiple beam profile measurements in several accelerator areas are used. The currents in steering coils are found to suppress the beam displacement. The gradients in quadrupole lenses are calculated to match the beam. This procedure is successfully used in accelerator tuning.Разработан пакет программ для проведения интерактивной процедуры поперечного согласования и коррекции пучка по результатам измерения профилей пучка на различных участках линейного ускорителя ИЯИ РАН. Определяются режимы включения корректирующих элементов для выведения пучка на ось ускорителя и градиенты полей квадрупольных линз для согласования пучка с фокусирующим каналом ускорителя. Разработанная процедура успешно используется при настройке режимов работы ускорителя.Розроблено пакет програм для проведення інтерактивної процедури поперечного узгодження і корекції пучка за результатами виміру профілів пучка на різних ділянках лінійного прискорювача ІЯД РАН. Визначаються режими включення коригувальних елементів для виведення пучка на вісь прискорювача і градієнти полів квадрупольних лінз для узгодження пучка з фокусуючим каналом прискорювача. Розроблена процедура успішно використається при настроюванні режимів роботи прискорювача

Activation transport under quantum Hall regime in HgTe-based heterostructure

We have measured the temperature (2.9 K < T < 50 K) and magnetic field (0 T < B < 9 T) dependences of longitudinal and Hall resistivities for HgCdTe/HgTe/HgCdTe system with HgTe quantum well width of 20.3 nm. The activation analysis of the experimental magnetoresistivity traces has been used as a quantitative tool to probe inter-Landau level distances. The activation energies were determined from the temperature dependence of the longitudinal resistivity in the regions of quantized Hall plateaus (for the filling factors ν of 1, 2 and 3) and the indications of the large values of the g factor ≅ 30–75 were found

Ioffe-time distributions instead of parton momentum distributions in description of deep inelastic scattering

We argue that parton distributions in coordinate space provide a more natural object for nonperturbative methods compared to the usual momentum distributions in which the physics of different longitudinal distances is being mixed. To illustrate the advantages of the coordinate space formulation, we calculate the coordinate space distributions for valence quarks in the proton using the QCD sum rule approach. A remarkable agreement is found between the calculated and the experimentally measured u-quark distribution up to light-cone distances $\Delta^- = \Delta^0 - \Delta^3$ of order $\sim 1$ fm in the proton rest frame. The calculation for valence d quarks gives much worse results; the reasons for this discrepancy are discussed.Comment: 24 pages plus 13 pages with figures, requires epsf.sty, revised version to appear in Phys.Rev.

Double distributions and evolution equations

Applications of perturbative QCD to deeply virtual Compton scattering and hard exclusive meson electroproduction processes require a generalization of usual parton distributions for the case when long-distance information is accumulated in nonforward matrix elements of quark and gluon light-cone operators. In our previous papers we used two types of nonperturbative functions parametrizing such matrix elements: double distributions F(x,y;t) and nonforward distribution functions F_\zeta(X;t). Here we discuss in more detail the double distributions (DD's) and evolution equations which they satisfy. We propose simple models for F(x,y;t=0) DD's with correct spectral and symmetry properties which also satisfy the reduction relations connecting them to the usual parton densities f(x). In this way, we obtain self-consistent models for the \zeta-dependence of nonforward distributions. We show that, for small \zeta, one can easily obtain nonforward distributions (in the X > \zeta region) from the parton densities: F_\zeta (X;t=0) \approx f(X-\zeta/2).Comment: 21 pages, Latex, 8 figures. To appear in Phys. Rev.

Gluon polarization in the nucleon from quasi-real photoproduction of high-pT hadron pairs

We present a determination of the gluon polarization Delta G/G in the nucleon, based on the helicity asymmetry of quasi-real photoproduction events, Q^2<1(GeV/c)^2, with a pair of large transverse-momentum hadrons in the final state. The data were obtained by the COMPASS experiment at CERN using a 160 GeV polarized muon beam scattered on a polarized 6-LiD target. The helicity asymmetry for the selected events is = 0.002 +- 0.019(stat.) +- 0.003(syst.). From this value, we obtain in a leading-order QCD analysis Delta G/G=0.024 +- 0.089(stat.) +- 0.057(syst.) at x_g = 0.095 and mu^2 =~ 3 (GeV}/c)^2.Comment: 10 pages, 3 figure

The Deuteron Spin-dependent Structure Function g1d and its First Moment

We present a measurement of the deuteron spin-dependent structure function g1d based on the data collected by the COMPASS experiment at CERN during the years 2002-2004. The data provide an accurate evaluation for Gamma_1^d, the first moment of g1d(x), and for the matrix element of the singlet axial current, a0. The results of QCD fits in the next to leading order (NLO) on all g1 deep inelastic scattering data are also presented. They provide two solutions with the gluon spin distribution function Delta G positive or negative, which describe the data equally well. In both cases, at Q^2 = 3 (GeV/c)^2 the first moment of Delta G is found to be of the order of 0.2 - 0.3 in absolute value.Comment: fits redone using MRST2004 instead of MRSV1998 for G(x), correlation matrix adde