Contributions from higher twist effects to the quark fragmentation functions in neutrino data

Quark fragmentation functions are studied with ≈3500 charged current events induced in the bubble chamber Gargamelle by neutrinos of the SPS wide band beam, with 〈E_ν〉 ≈ 25 GeV. The Q² and W² regions covered by this experiment are Q² ≈ 0–40 GeV² and W² ≈ 1–100 GeV², the mean values being 〈Q²〉 = 6.5 GeV², 〈W²〉 = 22GeV². A correlation between the variables $\text{z =}\text{E}{}_{\mathrm{\pi }}\text{E}{}_{\mathrm{<mtext>H</mtext>}}$ and $\text{y =}\text{E}{}_{\mathrm{<mtext>H</mtext>}}\text{E}{}_{\mathrm{v}}$ is found in the data in the region Q² = 1–10 GeV², which can be explained in terms of higher twist effects. These effects reproduce the Q² evolution of the non-singlet moments of the fragmentation function without any need for logarithmic terms.     

Partons and quark operators for higher twist

We compute the four-quark, twist-four contribution to the structure functions of leptoproduction in the parton model as a first step of a proposed approach towards a factorization algorithm for higher twist. Phenomenological implications for power corrections are also presented.     

The phase structure of SU(n)/Zn × SU(n)/Zn spin systems in two dimensions

The ground state of the two-dimensional chiral adjoint spin systems is studied using the most general nearest-neighbor ansatz for the eigenfunctions of the transfer matrix. The parameters entering this ansatz are determined variationally and the resulting phase structure is in close agreement with the results of Monte Carlo simulations.     

Green functions and twist correlators for N branes at angles

We compute the Green functions and correlator functions for N   twist fields for branes at angles on T²$T^2$ and we show that there are N−2$N-2$ different configurations labeled by an integer M   which is roughly associated with the number of reflex angles of the configuration. In order to perform this computation we use an SL(2,R)$\mathit{SL}(2,\mathbb{R})$ invariant formulation and geometric constraints instead of Pochammer contours. In particular the M=1$M=1$ or M=N−1$M=N-1$ amplitude can be expressed without using transcendental functions. We determine the amplitudes normalization from N→N−1$N\to N-1$ reduction without using the factorization into the untwisted sector. Both the amplitudes normalization and the OPE of two twist fields are unique (up to one constant) when the ?↔1−?$?\leftrightarrow 1-?$ symmetry is imposed. For consistency we find also an infinite number of relations among Lauricella hypergeometric functions.     

Charge accumulation in ultrathin Cs / n - GaN and Cs / n - InGaN interfaces

We report on the observation of new phenomena that arise under Cs adsorption on n-GaN(0001) and n-InGaN(0001) surfaces. First, an extremely highly quantum efficient photoemission has been found by excitation with visible light in the transparency region of GaN and InGaN. The photoemission is revealed to appear due to the formation of an electron accumulation layer in the vicinity of the surfaces. Second, a large variety of band bending and potential wells are provided by the Cs coverages. The accumulated charge density at the n-InGaN surface is much stronger than that at the n-GaN surface. Third, a new effect is revealed, namely, the appearance of an oscillation structure in the spectral dependences of the threshold photoemission. A model concept is proposed for photocurrent oscillations that takes into account the formation of an accumulation layer and the multiple-beam interference in parallel-sided GaN or InGaN samples.     

Guiding center motion of two interacting n=0 Landau electrons in two dimensions

The properties of a two-electron system in two dimensions subjected to a strong magnetic field are considered. Assuming that the electrons are in the lowest Landau level, all observables are expressed in terms of guiding center variables. In these variables, the hamiltonian can be exactly diagonalized.     

1/N calculation of structure functions

We calculate the quark and pion structure functions in CP^n?1 models with quarks using 1/N expansions. We find that the quark structure function, in the lowest order in 1/N, is just the free parton result with a modified coupling constant. The pion structure function resembles the phenomelogically successful fit but contains correction terms which modulate the function.     

Fine structure splittings in some highly ionized n = 3 doublets

Relativistic Z-expansion coefficient are calculated for ²P and ²D splittings in ions of the NaI, A1I, C1I, KI and CoI isoelectronic sequences. Good agreement with empirical results is found, and interpolation formulae valid at high Z are presented.     

Electronic structure and magnetism in (CoPt)n(n⩽5) clusters

The geometrical and magnetic properties of bimetallic clusters (CoPt)_n(1?n?5) have been studied by using the generalized gradient correction spin density formalisms. In general, the ground state structures of (CoPt)_n clusters are the three-dimension structures. We found that both the binding energy and magnetism per (CoPt) unit are increasing consistently with the size of the Co–Pt cluster (n). However, as the n increases, the magnetism shows a trace of convergence while the binding energy shows a linearly increasing pattern. Generally, Co average magnetic moment is enhanced when alloyed with Pt atoms than that in pure Co clusters.     

On representations of the groups Sp(n, 1) and Sp(n)

New classes of unitary irreducible representations of Sp(n, 1) which can be useful for applications in physics are obtained. The infinitesimal operators of these representations of Sp(n, 1) and of irreducible representations of Sp(n+1) with highest weights (m, m, m₃,…,m_n+1) and (m₁, m₂, 0,…,0) are expressed in terms of the simple Clebsch–Gordancoefficients for Sp(n). For Sp(3) and Sp(2, 1) they are found in an explicit form.     

Canonical realizations of the lie algebras gl(n, R) and sl(n, R) I. Formulae and classification

The generators of the Lie algebra of the general linear group GL(n, R) and of the special linear group SL(n, R) are, recurrently, expressed through polynomials in the quantum canonical variables p_t and q_t. These realizations are skew-Hermitian, the Casimir operations are realized by constant multiples of identity element and, in dependence on the number of the canonical pairs used, they depend on d(d?1 for sl (n,R)), d = 2, …, n, free real parameters.     

n(G)-nonextendibility of linear positive maps

Linear positive maps of C¹-algebras into the algebra of all bounded operators acting on a Hilbert space are considered. A special class of n(G)-nonextendible maps, which contains the class of nonextendible positive maps introduced by S.L. Woronowicz [9], is defined and studied. A map is n(G)-positive if it is n-positive or covariant with respect to the action of some group G of automorphisms of a C¹-algebra. n(G)-nonextendible maps are those which are nonextendible in this class in the sense of [9].Any n(G)-positive map can be obtained from an n(G)-nonextendible one by restriction.     

Wigner functions for two arbitrary operators and spectrum perturbation

We have concentrated on the Wigner function for the photon number and a quadrature operator, which we find to differ from zero outside the spectrum of the photon number operator. We have provided an illustration with a coherent state.     

Coleman-Weinberg symmetry breaking in the chiral SU(n) × SU(n) linear σ model

The onset of symmetry breaking in the chiral SU(n) × SU(n) linear σ model is investigated. It is shown that the model possesses no stable fixed points in d = 4 ? ? dimensions and that the chiral symmetry of the theory can be broken via the CW mechanism when d = 4. The implications of these results are discussed.     

Constructions and properties of k out of n scalable secret image sharing

Recently, Wang et al. introduced a novel (2, n) scalable secret image sharing (SSIS) scheme, which can gradually reconstruct a secret image in a scalable manner in which the amount of secret information is proportional to the number of participants. However, Wang et al.’s scheme is only a simple 2-out-of-n case. In this paper, we consider (k, n)-SSIS schemes where a qualified set of participants consists of any k participants. We provide two approaches for a general construction for any k, 2 ? k ? n. For the special case k = 2, Approach 1 has the lesser shadow size than Wang et al.’s (2, n)-SSIS scheme, and Approach 2 is reduced to Wang et al.’s (2, n)-SSIS scheme. Although the authors claim that Wang et al.’s (2, n)-SSIS scheme can be easily extended to a general (k, n)-SISS scheme, actually the extension is not that easy as they claimed. For the completeness of describing the constructions and properties of a general (k, n)-SSIS scheme, both approaches are introduced in this paper.     

First-principles investigation of the surface structures of Cu(n, n−1, 0) (n=2, 3 and 4) stepped surfaces

Multilayer relaxation at high-index Cu(n, n−1, 0) (n=2, 3 and 4) stepped surfaces was determined by the first-principles pseudopotential plane wave (PPPW) method. For those surfaces that have n and n−1 atom-rows in terrace and subterrace, respectively, the topmost 2n−2 interlayer spacings contract, while the 2n−1st interlayer spacing expands. There is no similar rule found for the relaxations parallel to the surfaces. Compared with the bulk terminated structure, a thin compact layer, which consisted of the topmost 2n−1 atom layers and separated slightly from the underneath atom layers, makes the surface more flat after relaxation. The bond-lengths between the step edge (first layer) atom and its nearest-neighbors do not depend on the surface termination, but only on the local coordination.     

Particle production at large pT in Xe+Xe collisions with jet quenching using the higher twist approach

The production of π⁰,η,and φ in the most central(0%-5%) Xe+Xe collisions at (s_NN)^1/2=5.44 TeV is investigated in the framework of the perturbative QCD(pQCD) improved parton model at an accuracy of next-toleading order(NLO).The jet quenching effect is effectively incorporated by medium-modified fragmentation functions via the higher-twist approach.Predictions of the nuclear modification factors of π⁰,η,and φ as functions of the transverse momentum p