Unique R-parity violating sneutrino exchange signatures at e + e − linear colliders with polarized beams

We examine the possibility of uniquely identifying the indirect effects of s-channel R-parity violation sneutrino exchange against other kinds of new physics that can be parametrized by the four-fermion contact interactions, by means of double polarization asymmetry at the International Liner Collider with both e ⁺ e ^? beams being polarized.     

Hard bremsstrahlung amplitudes fore + e − collisions with polarized beams at LEP/SLC energies

Cross sections are presented for the processese ⁺ e ^?→e ⁺ e ^?γ ande ⁺ e ^?→f \(\bar f\) γ (wheref is any light fermion) in the form of helicity amplitudes in which all complex phase information is kept. Owing to a spcial choice of the bremsstrahlung polarization and the use of spinor techniques the resultant expressions are extremely compact and lend themselves to fast numerical evaluation. An algorithm is given to obtain from the helicity amplitudes the cross section for arbitrary polarization of the incominge ⁺ e ^? beams. Special attention is given to the case of bremsstrahlung at very small angles to the beams, where a complicated dependence on the electron mass has to be taken into account.     

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.     

e + e −-Annihilation with polarized beams in the standard model and extended electroweak gauge models

We derive the general expressions for the differential cross section and final state polarization ine ⁺ e ^?→γ,Z ₁ ⁰ ,Z ₂ ⁰ , ...→ff (f: leptons and quarks) with several neutral bosons and with polarized beams. From this also the jet axis distributions ine ⁺ e ^? → 2 jets are obtained. The general formulas are applied to the standard model and extended gauge models of electroweak interactions with one neutral boson lighter than the standard modelZ ⁰. The models differ from each other in the coefficients of angular distributions at energies around the firstZ ⁰ resonance and beyond. Observable effects are expected in certain models already at energies up to 60 GeV if the firstZ ⁰ is not too heavy.     

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.     

Possibility of distinguishing the effect of neutral weak currents in e+e− → μ−μ+ experiments with longitudinally polarized clashing beams

The process e⁺e^{– – +} for the case of longitudinal polarization of the initial and final particles is studied on the basis of several models: the Weinberg-Salam model, the Lee-Prentki-Zumino model, the vector model, the X model, and under the assumption of a V-A structure of the neutral weak currents. Polarization effects tn the differential and total cross sections for this process are analyzed in detail, and various possibilities for distinguishing the contribution of neutral weak currents are found. Calculations show that neutral weak currents lead to appreciable polarization effects at attainable energies and that these effects are very sensitive to the model. It is important to note that an experimental study of these effects can yield valuable information on not only the structure of the neutral weak currents but also the sign of the weak-interaction constant.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 31–36, April, 1978.The authors thank A. A. Sokolov for a useful discussion and for interest in this work.     

Forward circularly polarized photon emission in longitudinally polarized e+e− collisions

We discuss the emission of circularly polarized forward photons in high energy e⁺e⁻ collisions with longitudinally polarized beams. We find substantial asymmetry under inversion of longitudinal electron polarization, thus supporting the proposal that measurement of circular polarization of forward emitted photons may allow for monitoring of longitudinal beam polarization.     

Joint creation of Z-boson and photons by colliding e+e− beams

Density matrix elements for a Z-boson created in the reaction e⁺+e^–Z+, are computed. Two reference frames are used in computations: the center-of-mass frame of the reaction e⁺+e^–Z+ with polarization states of the Z-boson specified by the polarization 4-vector with definite helicities, and the rest frame of the Z-boson. In both cases P-odd phenomena should stipulate particular combinations of the density matrix elements. The energy behavior of the total cross-section of the process e⁺+e^–Z+ is studied.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 3–6, September, 1982.     

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.     

Higgs-boson production together with neutrino pair at e+e− colliders

The cross section for production of supersymmetric neutral Higgs boson in association with a neutrino-antineutrino muon pair in e⁺e^? annihilation are calculated, i.e. $e^ + e^ - \to \nu _\mu \bar \nu _\mu H_i^0 $ via different propagators.     

Discovering and studying bileptons with e−e− collisions

We analyze the prospects for discovering and unraveling the nature of doubly charged bileptons at a linear collider of the next generation running in its e⁻e⁻ mode. We stress the importance of initial state radiation, beam spread and polarization, and compute the discovery bounds. The gauge nature of vector bileptons can be determined by studying hard photon emission.     

Possibility of distinguishing the contribution of neutral weak currents in e+e− → μ−μ+ experiments with transverse-polarized clashing beams

The process e⁺+e^{– –}+ ⁺ is studied on the basis of several models: the Weinberg- Salam model, the Lee-Prentki-Zumino model, the vector model, the X model, and under the assumption of a V-A structure of the neutral weak currents. Arbitrary polarizations of all the particles are taken into account simultaneously. Polarization effects are analyzed in detail for the case of transverse-polarized clashing beams, and various possibilities for distinguishing the contribution of neutral weak currents are identified. This possibility is very important not only for obtaining information about the structure of these currents but also for experimentally determining the sign of the weak-interaction constant. Calculations show that the neutral weak currents lead to significant polarization effects at attainable energies. These effects are very sensitive to the model.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 22–27, April, 1978.The authors thank A. A. Sokolov for interest and a useful discussion.     

The process\bar p p→e − e + with polarized initial particles and proton form factors in time-like region

The process pe ^– e ⁺ is considered in the general case of polarized initial particles. A relation between the difference of the phases of the electromagnetic form factorsG _M andG _E in the time-like region and measurable asymmetries is derived. It is shown that the moduli of the form factors can be determined from measurements of the total unpolarized cross section and of the integral asymmetry for longitudinally polarized (or, transversely polarized) andp. The behaviour of the proton form factors at highq ² in the time-like region is also discussed. From the Phragmén-Lindelöf's theorem it follows that the asymptotical behaviour of the form factors in the space-like and time-like regions must be the same. An analysis of experimental data in both regions based on perturbative QCD is presented.     

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.     

Study of conversion decays φ→ηe+e− and η→γe+e− in the experiment with SND detector at VEPP-2M collider

The conversion decays φ→ηe⁺e⁻ and η→γe⁺e⁻ were studied by the SND detector using φ-meson production in e⁺e⁻-annihilation at VEPP-2M collider. The branching ratios of these decays were measured: Br(φ→ηe⁺e⁻)=(1.19±0.19±0.07)×10⁻⁴ and Br(η→γe⁺e⁻)=(5.15±0.62±0.39)×10⁻³. The e⁺e⁻-pair mass spectra and transition form factors were also studied.     

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.     

Nuclear Physics with 10 PW laser beams at Extreme Light Infrastructure – Nuclear Physics (ELI-NP)

The field of the uncharted territory of high-intensity laser interaction with matter is confronted with new exotic phenomena and, consequently, opens new research perspectives. The intense laser beams interacting with a gas or solid target generate beams of electrons, protons and ions. These beams can induce nuclear reactions. Electrons also generate ions high-energy photons via bremsstrahlung processes which can also induce nuclear reactions. In this context a new research domain began to form in the last decade or so, namely nuclear physics with high power lasers. The observation of high brilliance proton beams of tens of MeV energy from solid targets has stimulated an intense research activity. The laser-driven particle beams have to compete with conventional nuclear accelerator-generated beams. The ultimate goal is aiming at applications of the laser produced beams in research, technology and medicine. The mechanism responsible for ion acceleration are currently subject of intensive research in many laboratories in the world. The existing results, experimental and theoretical, and their perspectives are reviewed in this article in the context of IZEST and the scientific program of ELI-NP.     

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.