Transverse spin asymmetries for W-production in proton–proton collisions

We study parity-even and parity-odd polarization observables for the process pp→l^±X$pp\to l^{\pm }X$, where the lepton comes from the decay of a W-boson. By using the collinear twist-3 factorization approach, we consider the case when one proton is transversely polarized, while the other is either unpolarized or longitudinally polarized. These observables give access to two particular quark–gluon–quark correlation functions, which have a direct relation to transverse momentum dependent parton distributions. We present numerical estimates for RHIC kinematics. Measuring, for instance, the parity-even transverse single spin correlation would provide a crucial test of our current understanding of single spin asymmetries in the framework of QCD.     

The proton spin puzzle and Λ polarization in deep-inelastic scattering

We point out that measurements of longitudinal Λ polarization in the target fragmentation region of deep-inelasticνN andμN oreN scattering may test dynamical mechanisms invoked to explain the proton spin puzzle. A previously-proposed model for polarizedqs pairs in the proton wave function reproduces successfully the negative Λ polarization found in the WA59 $\bar v$ experiment, and makes predictions that could be tested in futureμN andeN experiments.     

Calculation of gluon contribution to the proton spin by using the non-perturbative quantization à la Heisenberg

The contribution of crossed gluon fields in flux tubes connecting quarks to the proton spin is calculated. The calculations are performed following non-perturbative Heisenberg’s quantization technique. In our approach a proton is considered as consisting of three quarks connected by three flux tubes. The flux tubes contain colour longitudinal electric and transversal electric and magnetic fields. The transversal fields causes the appearance of the angular momentum density. The dimensionless relation between the angular momentum and the mass of the gluon fields is obtained. The contribution to proton spin from rotating quarks and flux tubes connecting quarks is estimated. Simple numerical relation between the proton mass, the speed of light and the proton radius, which is of the same order as the Planck constant, is discussed.     

Cross section for the Drell–Yan process in proton–proton collisions at the Large Hadron Collider (LHC)

The cross sections for the Drell–Yan process at the c.m. collision energy of \(\sqrt s \) = 13 TeV were calculated, and the results of these calculations are presented. The systematic errors associated with the uncertainties in the quark and gluon distributions and with the choice of scale for factorization and for the running QCD coupling constant are considered.     

The contribution of bremsstrahlung γ to the highp T γ production cross-section in π− p collisions at 280 GeV/c

The production of charged hadrons accompanying the highp _T photons in the reactions ^– pX at 280 GeV/c has been studied using data from the WA70 experiment at the CERN SPS. The energy distribution of these hadrons cannot be explained by direct photon processes and their hadrons background alone. The rate of bremsstrahlung processes has been estimated on the assumption that the hadronic excess results from such processes alone.     

Forward-backward multiplicity distributions in the Peřina-McGill scheme and analysis ine + e − collisions

A forward-backward multiplicity correlation is considered by the use of the Pe?ina-McGill formula. We obtain analytic formulae for conditional cumulants of the backward multiplicity and a conditional backward multiplicity distribution at a given forward multiplicity. The multiplicity distribution and the conditional mean multiplicity observed at \(\sqrt s = 29\) in HRS ine ⁺ e ^? collisions are analysed. We predict the conditional moments and the conditional backward multiplicity distribution. Those should be compared with the future analyses in HRS.     

Electron spin resonance and cation distribution studies of the Co0.6Zn0.4MnxFe2−xO4 ferrite system

The ESR spectra of the ferrite system Co_0.6Zn_0.4Mn_xFe_2−xO₄ (x=0, 0.1, 0.2, 0.3, 0.4 and 0.5) were obtained at room temperature. The experimental values of the magnetic moment (μ_exp) were estimated from the ESR spectra and the cation distribution was consequently established from the values of μ_exp. The systematic decrease in ESR line width observed in our present study was attributed to the decrease of Fe²⁺ concentration with increasing Mn content. The resonance field decreases and reaches a minimum at high values of Mn content whereas the magnetic moment reaches a maximum at these values. The IR spectra were recorded in the range 200–1200 cm⁻¹. The bands at 569 (ν₁) and 389 cm⁻¹ were assigned to the tetrahedral and octahedral complexes, respectively. The band at 441 cm⁻¹ is due to the Mn–O bond vibration. The theoretical lattice parameter was calculated and was found to be larger than the experimental one a_exp due to the presence of Mn⁴⁺ ions.     

Anomalous pulse-angle and phase dependence of Hahn’s electron spin echo and multiple-quantum echoes of the spin correlated radical pair P700+A 1 − in photosystem I

In a spin-correlated radical pair system, anomalous pulse-angle and phase dependence of electron spin echo and multiple-quantum echoes were theoretically calculated by Tanget al. (J. Chem. Phys.106, 7471 (1997)). The maximum intensity of the out of phase signal at 45 degree of spin rotation angle was experimentally verified in two-pulse echoes of the light-induced P700⁺A ₁ ^? radical pair in Photosystem I. The values,D = 1.64 G andJ = 0.00 G, fit well with the experimental ESEEM spectra. Single and double quantum echoes were observed at the value oft = τ andT = 2τ with the laser flash-t-P1_70,ζ1-τ-P2_{140, ζ2}-T pulse sequence, which led to determination of the relaxation time T₂₃ between the singlet and triplet ¦T₀〉 states. The relaxation times of the zero and single quantum transitions were determinedT ₂₃ ≈ 100 ns andT ₂ = 1000 ns, respectively. The field sweep ESE signal shape can be fitted with the hyperfine inhomogeneities of 7 G for P700⁺ and of 10 G for A ₁ ^? .     

Deuteron spin–lattice relaxation in the presence of an activation energy distribution: Application to methanols in zeolite NaX

A new method is introduced for analyzing deuteron spin–lattice relaxation in molecular systems with a broad distribution of activation energies and correlation times. In such samples the magnetization recovery is strongly non-exponential but can be fitted quite accurately by three exponentials. The considered system may consist of molecular groups with different mobility. For each group a Gaussian distribution of the activation energy is introduced. By assuming for every subsystem three parameters: the mean activation energy E₀, the distribution width σ and the pre-exponential factor τ₀ for the Arrhenius equation defining the correlation time, the relaxation rate is calculated for every part of the distribution. Experiment-based limiting values allow the grouping of the rates into three classes. For each class the relaxation rate and weight is calculated and compared with experiment. The parameters E₀, σ and τ₀ are determined iteratively by repeating the whole cycle many times. The temperature dependence of the deuteron relaxation was observed in three samples containing CD₃OH (200% and 100% loading) and CD₃OD (200%) in NaX zeolite and analyzed by the described method between 20 K and 170 K. The obtained parameters, equal for all the three samples, characterize the methyl and hydroxyl mobilities of the methanol molecules at two different locations.     

Transverse-momentum distribution of J/Ψ's in Pb-Pb collisions and gluon rescattering

We study anomalous J/Ψ suppression and p _t broadening in the model of prompt gluons. The anomalous suppression can be successfully described in this model. The transverse-momentum dependence of J/Ψ suppression in relativistic heavy-ion collisions is calculated from initial-state gluon rescattering with both nucleons and prompt gluons produced in nucleon-nucleon collisions in the early phase of the reaction. It seems impossible to describe simultaneously anomalous suppression and p _t broadening in Pb-Pb collisions within the model of prompt gluons with reasonable values of the parameters. Received: 27 September 2001 / Accepted: 12 November 2002 / Published online: 17 January 2003 RID="a" ID="a"e-mail: zhuangpf@mail.singhua.edu.cn Communicated by A. Molinari     

Production of polarized baryons in polarized and unpolarizede + e − collisions

Polarized and unpolarizede ⁺ e ^? annihilation is considered in lowest order at energies 30–150 GeV taking γ andZ ⁰ exchange in the standardSU(2)×U(1) model into account. The fragmentation of polarized quarks into polarized baryons is described by two kinds of fragmentation functions; the first is based onSU(6) weights and empirical expressions for favoured and disfavoured fragmentation; the second is based upon a Monte Carlo model of the chain decay including helicities of quarks and hadrons. From the cross sections for \(e^ + e^ - \to q\bar q\) and the fragmentation functions we obtain predictions for the baryon polarization as function of the collision energy and of kinematical variables.