Radiative corrections for associatedZH production at futuree + e − colliders

The \(ZHf\bar f\) four-point function is calculated in the one-loop approximation of the Standard Model and full analytic results are presented. The loop contributions due to both light and new heavy fermions are inspected in detail. The dominant mechanisms of Higgs-boson production from fermions are compared. The effect of radiative corrections on the cross section of \(f\bar f \to ZH\) including bremsstrahlung is studied. The spectrum of hard bremsstrahlung is integrated analytically. The implications for Higgs-boson searches at futuree ⁺ e ^? colliders in the energy range 200 \(200GeV \le \sqrt s \le 1.5TeV\) , which includes both LEP 2 and the Next Linear Collider, are analyzed. ForM _H <2m _t weak corrections in the modified on-mass-shell scheme are generally negative and feebly vary withM _H , while forM _H >2m _t , they strongly increase withM _H and may take large positive values. Electromagnetic corrections dramatically reduce the cross section close to theZH-production threshold, while they may considerably enhance it far above this threshold.     

Predictions for anomalous τ+τ−γ production at LEP 1

We calculate distributions for τ⁺τ^?γ production at LEP 1 taking into account a potentially existing anomalous magnetic moment a _τ of the τ lepton. The existing upper limits for ¦a _τ¦ are known from the dependence of the decay Z ⁰ → τ⁺τ^?γ on a _τ ² and are of the order of (1–5)%. We show that such limits are also sensitive to linear terms in a _τ, which are of equal importance at ¦a _τ¦ ～ (1–2)% and dominate below this value. Contributions from an electric dipole moment dτ do not interfere with the electromagnetic vertex or with the anomalous magnetic moment. Appropriate formulae are derived.     

Nuclear data for the cyclotron production of ~（117）Sb and ~（90）Nb

This presented study is to make comparison of cross sections to produce ¹¹⁷Sb and ⁹⁰Nb via different reactions with particle incident energy up to 70 MeV as a part of systematic studies on particle-induced activations on enriched Sn, Y₂O₃ and ZrO₂ targets, theoretical calculation of production yield, calculation of required thickness of target and suggestion of optimum reaction to produce Antimony-117 and Niobium-90.     

New investigation for Tc depression by Ca in Y1−xCax:123 superconducting systems

Two similar sets of the series Y_1?xCa_xBa₂Cu₃O_Y (0.00 ? x ? 0.50) are prepared by two different heat treatments at the final process of calcinations. The first set is quenched in air down to room temperature (ssq); while the second is left in the furnace and slowly cooled to room temperature (sss). After that, the samples are separately sintered in two different oxygen purity (99.99% Hp and 93% Lp, respectively) to obtain four different sets called ssqHp, sssHp, ssqLp and sssLp. Then, the considered samples are tested by XRD, SEM, resistivity and microhardness (VHN) techniques. It is found that c-parameter for ssqHP and sssLP samples increases slightly with Ca doping; while orthorhombic distortion remains nearly invariant. Interestingly, unlike for ssqHp and sssLp samples, the OD decreases continuously with Ca doping in sssHp and ssqLp samples; while c-parameter increases. SEM micrographs indicate that Ca generally improve the link between superconducting grains for all set of samples. The oxygen content is gradually decreased by Ca for all set of samples and generally follow the relation, y = 6.93 ? 0.5x. The effective Cu valence slightly decreases, as compared to pure samples, but stays nearly independent of Ca content for all the series. The relative decrease in critical temperature T_c by Ca is more in ssqHp and sssLp samples, when compared with those of sssHp and ssqLp samples. Although, an approximately linear increase in VHN with various Ca is obtained, the relative increase is more in ssqHp and sssLp samples with respect to sssHp and ssqLp samples. These results indicate that substitution of Ca at Y site leads towards oxygen vacancies predominantly created in CuO₂ planes (CuO chains) of ssqHp and sssLp (sssHp and ssqLp) based samples, and far from overdoping.     

Structural and superconducting properties of Eu1−xPrxBaSrCu3O7−δ

We have investigated the structural and superconducting properties of Eu_1−xPr_xBaSrCu₃O_7−δ by X-ray diffraction analysis, AC and DC magnetization and DC resistivity measurements. The parent compound crystallizes in the orthorhombic symmetry which transforms to tetragonal symmetry at x=0.2. Superconducting transition temperature T_c decreases monotonically with increasing x which approaches zero at x=0.6. The enhancement in critical concentration x_cr observed in Eu_1−xPr_xBa₂Cu₃O_7−δ on replacing 50 at.% Ba by Sr is attributed to the resulting local structural changes.     

Subthreshold K− production in pion-nucleus reactions

The inclusive subthresholdK ^– mesons production in charged pion-induced reactions is analyzed with respect to the one-step production processes on the basis of an appropriate first collision model, which allows one to take into account the various forms of an internal nucleon momentum distribution. Free elementary production processes are described by the phase space calculations normalized to the corresponding total experimental cross sections. Simple parametrizations for the total cross sections of theK ^– production in pion-nucleon collisions are given. Primary-pion energy dependence of the inclusive cross sections for K^– production in ⁺ C– collisions is calculated. The influence of the uncertainties in the elementaryK ^– production cross sections close to the production threshold on theK ^– yield is explored.The authors acknowledge stimulating discussions with V. Koptev on the initial stage of this study.     

Factorization and transverse momentum for two-hadron production in inclusive e + e − annihilation

We study the factorization of processes involving two fragmentation functions in the case of very small transverse momenta. We consider two-hadron production in inclusive e ⁺ e ⁻ annihilation and demonstrate a new simple and illustrative method of factorization for such processes, including leading order α _s corrections. The text was submitted by the authors in English.     

Inclusive ϕ production inK − p interactions at 110 GeV/c and search for structure in φ π−

Results on inclusive ? production inK ^? p interactions at 110 GeV/c are presented. The production cross section is found to be larger than in πp andpp interactions at similar energies, suggesting OZI allowed \(s\bar s\) fusion to be the dominant mechanism in ? production. Thex distributions of ? and \(\bar K^{*0} \) are found to be similar to each other over the entirex range suggesting an overall strangeness suppression factor of 0.20±0.04 in the sea to be the dominant source of the difference in the cross section for ? and \(\bar K^{*0} \) . There is no evidence of a narrowφπ ^? state around 2.1 GeV/c² as suggested byK ⁺ experiments, but there is some excess of events in the region 1.94?1.98 GeV/c² consistent with theF-meson mass as observed ine ⁺ e ^? experiments.     

A minimum single-band model for low-energy excitations in superconducting A x Fe2−y Se2

We investigate the coherent electronic transport properties of square-shaped zigzag graphene nanoconstrictions (ZGNC) under transverse strain using recursive Green’s function method. We find that the low-bias conductance of ZGNCs is monotonically dependent on the strain in contrast to that of zigzag graphene nanoribbons (ZGNRs), which is unaffected by strain. This result suggests that ZGNCs can be used as elementary building blocks in graphene nanomechanical system devices. In addition, a simplified analytical model is employed to qualitatively explain the strain tuning of the low-bias conductance of ZGNCs.     

Fluorination of superconducting Ba2YCu3O9−δ

Using a series of samples ranging in composition from δ = 2 to δ = 3 we have successfully introduced substantial amounts of fluorine into samples of superconducting Ba₂YCu₃O_9-δ by annealing under F₂ gas flows at low temperatures. These syntheses yielded single phase materials containing up to 1.05 F per formula unit. ¹⁹F NMR experiments have confirmed that fluorine is incorporated into the lattice and susceptibility and transport measurements indicate that the samples are superconducting with critical temperatures in the range 80 to 89 K.     

Simulation of electron cyclotron current drive and electron cyclotron resonant heating for the HL-2A tokamak＊

A quasi-linear formalism is developed for relativistic particles. It is self-consistent including spatial diffusion. An attempt is made to simulate the process of electron cyclotron resonant heating （ECRH） and electron cyclotron current drive （ECCD） for the HL-2A tokamak. Temperature oscillating regimes in Tore Supra diagnosed by MHD activity seem to be reproduced in the simulation. The special feature in this paper is to see the resonance in the long time scale for relativistic plasma.     

Critical properties of superconducting Ba1−xKxFe2As2

Magnetisation and magneto-resistance measurements have been carried out on superconducting Ba_1?xK_xFe₂As₂ samples with x = 0.40 and 0.50. From high field magnetization hysteresis measurements carried out in fields up to 16 T at 4.2 K and 20 K, the critical current density has been evaluated using the Bean critical state model. The J_C determined from the high field data is >10⁴ A/cm² at 4.2 K and 5 T. The superconducting transitions were also measured resistively in increasing applied magnetic fields up to 12 T. From the variation of the T_C onset with applied field, dH_C2/dT at T_C was obtained to be ?7.708 T/K and ?5.57 T/K in the samples with x = 0.40 and 0.50.     

Multipurpose device for nonperturbative photoelectron diagnostics of high-energy H− ion beams

A method of nonperturbative photoelectron diagnostics of a high-energy negative-ion beam proposed earlier by one of the authors is briefly discussed. A multipurpose device using the proposed method of a relativistic H⁻ ion beam in straight-line segments of the transportation channel is described in detail. The beamprobing photonic targets are formed by diaphragming polarized radiation of an Nd:YAG laser. The ion energy (momentum) distributions in transverse and longitudinal phase spaces are promptly determined from the spatial distributions of photoelectrons formed at the corresponding detectors after passing through a homogeneous-field 180° magnetic analyzer.     

Vector boson pair production in e−e− collisions with polarized beams

The W-boson pair production in e⁻e⁻ collisions with polarized beams is investigated. The helicity amplitudes are derived for general couplings and the conditions for a good high-energy behaviour of the cross-section are given. The results are applied to the heavy vector boson production in the context of the left-right symmetric model. The Ward identities and the equivalence theorem are also discussed.     

Higgss-channel production ine + e − collisions below theW + W − threshold

The cross section for direct neutral Higgs production in the reaction is calculated in theE _CM energy range of 40 to 160 GeV and compared to the corresponding Electro-Weak (EW) process . Neglecting radiation effects, a signal of the order of 10^–4 to 10^–3 over the EW can be expected outside theZ ⁰ region for the Minimal Standard Model Higgs in its decay to a state. For \sqrt s - M_Z $$ " align="middle" border="0"> , thes-channel Higgs formation can surpass the Bjorken Bremsstrahlung process and thus may afford at LEP 2 a realistic search method for high mass, say 100 GeV Higgs, given enough luminosity. For a non-Standard Model Higgs, in some cases, significantly higher signals are expected. The effects of initial state radiation and-machine energy resolution are evaluated and the gain in using longitudinal polarized electron beams is discussed.Supported in part by the Israel Ministry for Science and Technology     

H ̄ + production from collisions between positronium and keV antiprotons for GBAR

In the framework of the GBAR (Gravitational Behaviour of Antihydrogen at Rest) experiment, cross sections for antihydrogen ion ( \(\bar {\mathrm {H}}^{+}\) ) production in collisions between antiprotons ( \(\bar {\mathrm {p}}\) ) and excited positronium atoms (Ps), with intermediate production of antihydrogen ( \(\bar {\mathrm {H}}\) ), have been computed using a perturbative theory, namely Continuum Distorted Wave - Final State (CDW-FS). The results suggest to use antiprotons at 1, 2 or 6 keV with, respectively, Ps(3p,3d), Ps(2p) or no Ps excitation. A simulation using these cross sections is under development to investigate the reaction chamber geometry and the parameters of the different beams (positrons, antiprotons and laser). This simulation, focusing on Ps(3d), predicts at least one \(\bar {\mathrm {H}}^{+}\) ion per pulse of 3·10⁶ \(\bar {\mathrm {p}}\) at 1 and 6 keV, and highlights both the interest of positronium excitation and the need for short pulses of particles.