Ilya F. Ginzburg

COLLIDING ge AND gg BEAMS BASED ON THE SINGLE-PASS e ~ e COLLIDERS (VLEPP TYPE)

Abstract We discuss in detail our proposed [1,2] method of obtaining colliding γe and γγ beams with high energies and luminosities using the designed linear accelerators VLEPP and SLC with colliding e + e − beams at the energies 2 E ≳ 100 GeV. The intense γ beams are obtained by backward Compton scattering of laser light which is focused on the electron beams of these accelerators. This paper contains the scheme for conversion of an electron beam into a γ beam, a calculation of the conversion coefficient and of the total and spectral γe and γγ luminosities. To get the luminosity L γ e , L γγ ∼ L ee , one needs a laser flash with energy ∼ 15J, and a pulse duration ∼ 30 ps at a repetition rate of 10 or 180 Hz. Such parameters seem to be achievable on the basis of current technology. The luminosity distribution over the γe or γγ invariant mass is broad. A method of monochromatization is described. It demands an increase of the laser flash energy (with a possible increase of pulse duration) and leads to a decrease of luminosity. We also describe a method for calibrating the total and spectral luminosities. Problems concerning the background are shown to be easier than in e + e − collisions. Some examples of interesting physical problems for γe and γγ collisions are enumerated.

Colliding γe and γγ beams based on single-pass e+e− accelerators II. Polarization effects, monochromatization improvement

Polarization effects are considered in colliding γe and γγ beams, which are proposed to be obtained on the basis of linear e+e− colliders (by backward Compton scattering of laser light on electron beams). It is shown that using electrons and laser photons with helicities λ and Pc, such that λPc<0, essentially improves the monochromatization. The characteristic laser flash energy, A0, which is necessary to obtain a conversion coefficient k ≈ 1 with a definite degree of monochromatization, is considerably less (sometimes by one order of magnitude) in the case 2λPc = −1 in contrast to the case λPc=0. Simultaneously the luminosities Lγe and Lggγ essentially increase. Formulae are obtained which allow one to extract the polarization information about γe → X and γγ → X reactions. Perculiarities connected with the specific scheme of the γ beam preparation are discussed. Problems of the calibration of the γe and γγ collisions for the polarized beams are discussed.

Tree-level unitarity constraints in the most general two Higgs doublet model

We obtain tree-level unitarity constraints for the most general Two-Higgs-Doublet Model (2HDM) with explicit

Evolution of the Universe to the present inert phase

CP

An interaction region for gamma–gamma and gamma–electron collisions at TESLA/SBLC

-violation. We briefly discuss correspondence between possible violation of tree-level unitarity limitation and physical content of the theory.

Evolution of vacuum states and phase transitions in the two Higgs doublet model during cooling of the Universe

We assume that the current state of the Universe can be described by the inert doublet model, containing two scalar doublets, one of which is responsible for electroweak-symmetry breaking and masses of particles and the second one having no couplings to fermions and being responsible for dark matter. We consider possible evolutions of the Universe to this state during cooling down of the Universe after inflation. We found that in the past the Universe could pass through phase states having no dark matter candidate. In the evolution via such states, in addition to a possible electroweak-symmetry breaking phase transition (second order), the Universe sustained one first-order phase transition or two phase transitions of the second order.

Standard-Model-like scenarios in the 2HDM and Photon Collider potential

Abstract Linear colliders offer a unique opportunity to study γγ and γe interactions. Using the laser backscattering method one can obtain γγ, γe colliding beams with an energy and luminosity comparable to that in e + e − collisions. This work is part of the Conceptual Design of TESLA/SBLC linear colliders considering a second interaction region for γγ and γe collisions. We consider here possible physics in high-energy γγ, γe collisions, e→γ conversion, requirements to lasers, collision schemes, attainable luminosities, backgrounds, possible lasers, optics at the interaction region and other associated problems.

Semihard production of neutral pseudoscalar and tensor mesons in photon-photon collisions

We consider the evolution of the ground state in the two Higgs doublet model during cooling down of the Universe after the big bang. Different regions in the space of free parameters of this model correspond to different sequences of thermal phase transitions. We discuss different paths of thermal evolution and corresponding evolution of physical properties of the system for different modern values of the parameters.

Search for fourth generation quarks and leptons at the Fermilab Tevatron and CERN Large Hadron Collider

After operations at the LHC and e+e− Linear Colliders it may be found that a Standard-Model-like scenario is realized. In this scenario no new particle will be discovered, except a single Higgs boson having partial widths or coupling constants with fundamental particles, whose squares are close, within anticipated experimental uncertainty, to those of the SM. Experiments at a Photon Collider can resolve whether the SM or e.g. the Two-Higgs-Doublet Model is realized in Nature. For the SM-like realizations of the 2HDM (II) we study the loop couplings of the Higgs boson with γγ and Zγ, and also with gluons. The deviation of the two-photon width from its SM value is generally higher than the expected inaccuracy in the measurement of Γγγ at a Photon Collider. The deviation is sensitive to the parameters of the Higgs self interaction.

Excited leptons and quarks at γγ/γe colliders

We investigate the semihard production of neutral pseudoscalar and tensor mesons in high-energy γγ collisions (M = P = π0, η, η′ or M = T = a2, f2, f′2). We deal with the exclusive γγ → MM′ or semi-exclusive γγ → MX reactions (X is the hadron jet with not too large mass). The considered transfer momenta are small in comparison with the photon energies and they are large in comparison with the confinement scale. The amplitudes of these processes are determined by the odderon exchange, i.e. three-gluon exchange in the lowest order of perturbative QCD. The cross sections are calculated in this approximation. The possibility of measurements at LEP and at future γγ colliders is discussed.