Alternative vector-boson self-couplings and e+e− → W+W−

Employing global SU(2)_WI symmetry and γW³ mixing we derive a lagrangian for vector-boson self-interactions whose strength may considerably differ from the ones required by the standard model; the neutral-current structure and the mass relationship of the standard model remain intact, however. Numerical results for the cross section for e⁺e⁻ → W⁺W⁻ are presented.     

Comparative study of Z′ searches in e+e− and e−e− scattering

We consider indirect searches for additional neutral vector bosons in e⁺e⁻ and e⁻e⁻ collisions, and compare these two linear collider modes with similar analysis procedures and assumptions. Discovery limits and resolving power are discussed in a model-independent way.     

Jet masses in e+e− annihilation

We calculate heavy (M _H ² /s) and light (M _L ² /s) jet masses up toO(α _s ² ) in perturbative Quantum Chromodynamics (QCD). The sensitivity of these quantities to radiative corrections, quark masses, fragmentation effects as well as their infrared stability properties, are investigated and compared to those exhibited by other jet measures. A comparison with recent Mark II data is also presented.     

Thrust ine + e −-annihilation

The thrust distribution ine ⁺ e ^–-annihilation is analysed in perturbative QCD. Proper account is taken of multiple emission of gluons. Scaling holds for this quantity in the sense that its energy dependence comes only through the change in the QCD effective coupling. It thus provides an ideal means to determine the value of the QCD mass scale experimentally. From the data atW=91 GeV by the ALEPH collaboration at LEP, we obtain .     

Duality ine + e − annihilation

With the help of a relativistic generalization of the formula for the leptonic width of quarkonium in the semiclassical approximation it is shown that for any confinement potential nonsingular at the origin the sum of total cross sections for the production of the heavy quarkonium states \((Q\bar Q)_n\) with masses \(M_n \leqq \sqrt s\) ine ⁺ e ^?-annihilation is equal to the cross section at givens for the production of the free quark-antiquark pair \(Q\bar Q\) . We obtain also a family of dual sum rules for quarkonium which are in agreement with the available experimental data on charmonium and beautionium within experimental errors.     

e + e − multiplicity distribution from branching process

We present a multiplicity distribution which is a solution to the stochastic branching equation proposed by Giovannini. This solution is more commonly known as generalized multiplicities distribution (GMD) and has already been successfully applied to bothpp andp collisions. It assumes that shapes and energy dependence of distributions are basically determined by hard parton scattering and subsequent branching. We apply GMD to the recente ⁺ e ^– data by Tasso Collaboration.     

W+W−γ production in e+e− annihilation in the TeV region

The reaction e⁺e⁻→γW⁺W⁻ has been studied at TeV energies as a possible background to Higgs production. Our results differ significantly from previous estimates and show that the ratio signal/background can be kept reasonably large.     

Effect of weak neutral currents in the process e− + p → e− + γ + X

Polarization effects in the inclusive process e^– + p e^– + + X due to the neutral current are studied in the framework of the Weinberg-Salam model. Expressions for the asymmetry parameters and the degree of circular polarization of the photons are obtained in the quark-parton picture. It is shown that measurement of such quantities gives additional information about the quark structure of the hadronic weak neutral current.Paper presented at the scientific session of the nuclear physics branch, USSR Academy of Sciences and the Moscow State University on Electromagnetic and Weak Interactions (Moscow, January 16–20, 1979).Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 96–99, January, 1981.     

Rapidity distribution ine + e − annihilation

A method to systematically calculate the rapidity distribution of hadrons in a high-energy jet is formulated in terms of an integral equation for the multiplicity. The distribution has the following properties at high energies: (i) a translational invariance; (ii) an increasingly steep distribution with a width proportional to \(\sqrt {\ln s} \) , but without a widening “central plateau”; (iii) if the rapidity is scaled by \(\sqrt {\ln s} \) , it approaches to a universal exponential curve. In the large rapidity region, however, the translational invariance is broken because of the recoil of the quark by the emission of soft gluons. It is also discussed that a gluon jet has a wider angular distribution.     

Tests for planar events in e+e− annihilation

We present a new class of observables which distinguish events containing two or three hadron jets from those containing a larger number. These observables, which essentially measure the coplanary of events, are calculable in QCD perturbation theory. Their use should allow the mechanism of

decay to be determined.     

Higgsino production through toponium in e+e− reactions

Higgsino production in e⁺e⁻ reactions is considered in the simplest model where the higgsino is the lightest supersymmetric particle. The supersymmetric version of the Wilczek mechanism seems to be the best way to detect higgsinos and photinos in the LEP energy range.     

Double P-wave charmonium production in e + e − annihilation

On the basis of perturbative QCD and relativistic quark model we calculate relativistic and bound state corrections in the production processes of a pair of \(\mathcal{P}\) -wave charmonium states. Relativistic factors in the production amplitude are taken into account connected with the relative motion of heavy quarks and the transformation law of the bound-state wave function to the reference frame of the moving \(\mathcal{P}\) -wave mesons. Relativistic corrections to the quark bound-state wave functions in the rest frame are considered by means of the Breit-like potential. It turns out that the examined effects change essentially nonrelativistic results of the cross section for the reaction e ⁺ + e ^? → h _c + χ _c J at the center-of-mass energy √s = 10.6 GeV.     

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     

Spontaneous e+e− pair creation in heavy ion collisions

We demonstrate that vibrational perturbations of supercritical “quasimolecules” which may occur in collisions of heavy ions can, within the context of first-order perturbation,theory, result in the production of coincident narrow e⁺e⁻ peaks, in place of and with a larger yield than that predicted for spontaneous positron emission from static supercritical systems. Certain features of this phenomenon coincide with those of the e⁺e⁻ peaks observed by the EPOS collaboration although some important aspects of the observations cannot be reproduced within our approximation. A detailed attempt to reconcile this theoretical model with the EPOS experiment must go beyond perturbation theory.     

Zinos and scalar muon production at e+e− colliders

Single scalar muon production is examined in detail which results in a final state particularly favourable for detection: two strongly acollinear muons plus large missing energy. Cross sections, missing energy and angular distributions are given. A strong dependence on the zino total width, common to all single production channel, is found.     

Characterising WIMPs at a future e + e − linear collider

We investigate the prospects for detecting and measuring the parameters of WIMP dark matter in a model-independent way at the International Linear Collider. The signal under study is direct WIMP pair production with associated initial state radiation e ⁺ e ^?→χχγ. The analysis accounts for the beam energy spectrum of the ILC and the dominant machine induced backgrounds. The influence of the detector parameters are incorporated by full simulation and event reconstruction within the framework of the ILD detector concept. We show that by using polarised beams, the detection potential is significantly increased by reduction of the dominant SM background of radiative neutrino production $e^{+}e^{-} \rightarrow \nu \bar {\nu }\gamma The light-by-light contribution from the lightest neutral pseudoscalar and scalar mesons to the anomalous magnetic moment of muon is calculated in the framework of the nonlocal SU(3)×SU(3) quark model. The model is based on chirally symmetric four-quark interaction of the Nambu?CJona-Lasinio type and Kobayashi?CMaskawa?C??t?Hooft U _A (1) breaking six-quark interaction. Full kinematic dependence of vertices with off-shell mesons and photons in intermediate states in the light-by-light scattering amplitude is taken into account. The small positive contributions from the scalar mesons stabilize the total result with respect to change of model parameters and reduces to $a_{\mu}^{\mathrm{LbL},\mathrm{PS}+\mathrm{S}}=(6.25\pm0.83)\cdot10^{-10}$ .     

e+ e− production from pp reactions at BEVALAC energies

We have performed a detailed study of dilepton production from pp collisions including the subthreshold ϱ production via baryonic resonances (N(1520), N(1700)) in addition to the conventional dilepton sources as π⁰, η, ω and Δ Dalitz decays and direct decays of vector mesons (ϱ, ω). The role of baryonic resonances in ϱ production from nucleon-nucleon collisions is studied in comparison to the DLS data which are well described.