CP violation at colliders

The prospects of experimental detection ofCP violation ate ⁺ e ⁻ and colliders are reviewed. After a general discussion on the quantities which can measureCP violation and on the implications of theCPT theorem, various possibilities of measuringCP violation arising outside the standard model are taken up.CP violation in leptonic processes, especially polarization effects ine ⁺ e ⁻→l ⁺ l ⁻ are discussed next.CP violation in andW ⁺ W ⁻ production and decay is also described.     

Using the e ± μ? + E Tmiss signature in the search for supersymmetry and lepton-flavor violation in neutralino decays

The LHC (CMS) discovery potential in the search for supersymmetry and lepton-flavor violation in neutralino decays using the e ^± μ^∓ + E _T ^miss signature is studied. A detailed study is done for the CMS test points LM1-LM9. It is shown that, for the point LM1, it is possible to detect lepton-flavor violation in neutralino decays with lepton-flavor-violating branching Br( → μ^± e ^∓ ) ≥ 0.04 Br( → e ⁺ e ⁻ , μ⁺ μ⁻ ) for an integral luminosity of 10 fb⁻¹. The discovery potential in the mSUGRA-SUSY scenario with tan β = 10, sgn(μ) = + in the (m ₀, m _1/2) plane using the e ^± μ^∓ + E _T ^miss signature is determined. The text was submitted by the authors in English.     

Measuring the chargino parameters

After the supersymmetric particles have been discovered, the priority will be to determine independently the fundamental parameters to reveal the structure of the underlying supersymmetric theory. In my talk I discuss how the chargino sector can be reconstructed completely by measuring the cross-sections with polarized beams at e ⁺ e ⁻ collider experiments: e ⁺ e ⁻ → [i, j=1, 2]. The closure of the two-chargino system can be investigated by analysing sum rules for the production cross-sections.     

Dynamics of low-energy nuclear forces for electromagnetic and weak reactions with the deuteron in the Nambu-Jona-Lasinio model of light nuclei

A dynamics of low-energy nuclear forces is investigated for low-energy electromagnetic and weak nuclear reactions with the deuteron in the Nambu-Jona-Lasinio model of light nuclei by example of the neutron-proton radiative capture (M1-capture) n + p → D + γ, the photomagnetic disintegration of the deuteron γ + D → n + p and weak reactions of astrophysical interest. These are the solar proton burning p + p → D + e⁺ + ν _e, the pep-process p + e⁻ + p → D + ν _e and the neutrino and antineutrino disintegration of the deuteron caused by charged ν _e + D → e⁻ + p + p, + D → e⁺ + n + n and neutral ν _e() + D → ν _e() + n + p weak currents.     

Width effects of theZ resonance and CP-violating asymmetry ine + e − annihilation

CP-violating rate asymmetry can be generated in a process only if its amplitude possesses an absorptive part. It is pointed out that such an absorptive part can be provided ine ⁺ e ⁻ annihilation by the presence of aZ(Z′) resonance of non-zero width. The CP asymmetry in the process , wherel _i are charged leptons, is discussed in several models. In a specific two-Z model, large and observable CP asymmetry ine ⁺ e ⁻ →τ ⁺ e ⁻ (τ ⁻ e ⁺) is shown to be possible at LEP/SLC energies.     

QCD corr ec tions to d ecay-l ep ton polar and azimu thal angular dis tribu tions in e+ e− → t $$\ov erlin e t $$ in th e sof t-gluon approxima tionin th e sof t-gluon approxima tion

QCD corrections to order α _s in the soft-gluon approximation to angular distributions of decay charged leptons in the process e ⁺ e ⁻ → t , followed by semileptonic decay of t , are obtained in the esu− e ⁻ centre-of-mass frame. As compared to distributions in the top rest frame, these have the advantage that they would allow direct comparison with experiment without the need to reconstruct the top rest frame. The results also do not depend on the choice of a spin quantization axis for t or t. Analytic expression for the triple distribution in the polar angle of t and polar and azimuthal angles of the lepton is obtained. Analytic expression is also derived for the distribution in the charged-lepton polar angle. Numerical values are discussed for √s=400, 800 and 1500 GeV.     

Behaviour and spectroscopy of (anti) hydrogen atoms in strong magnetic fields

Since it has been demonstrated that antiprotons can be captured in sizeable amounts in ion traps, the intriguing question has been raised whether or not these antiprotons can be used for producingantihydrogen atoms. One route proposed is the merging of trapped antiprotons with a cold trapped plasma of positrons. In this case the formation of antihydrogen proceeds most likely through three-body recombination (p⁻e⁺e⁺→ e⁺) into high Rydberg states of , followed by a rapid cascade of transitions to low-lying states. To assess the influence of the trapping magnetic field (on the order of a few tesla) upon the formation process of we review the present knowledge of the behaviour and properties of hydrogen (and antihydrogen) atoms in strong magnetic fields — a subject which has been very topical in recent years because of its relation to the problem of “quantum” chaos.     

On pair production of scalar top quarks in <Emphasis Type="Italic">e</Emphasis><Superscript>+</Superscript><Emphasis Type="Italic">e</Emphasis><Superscript>−</Superscript> collisions at ILC and a possibility of their mass reconstruction

We study pair production of scalar top quarks (stop, ) in e ⁺ e ⁻ collisions with the subsequent decay of the top squarks into b quarks and charginos . We simulate this process by using PYTHIA6.4 for the beam energy 2E _b = = 350, 400, 500, 800, 1000 GeV. A set of criteria for physical variables is proposed, which provides good separation of stop signal events from top quark pair production being the main background. These criteria allow us to reconstruct the mass of the top squark with an integrated luminosity of 1000 fb⁻¹ provided that the neutralino mass is known. The article is published in the original.     

Isospin and the tau hadronic decay modes

Isospin constraints onτ decay modes are revisited with a special interest for the low branching ratio channels. It is shown that dominance of the vector current in the channel is suggested by the present data and that some discrepancies exist betweenτ partial width ande ⁺ e ⁻ cross-section measurements in the 6π channel.     

Quark-Antiquark states and their radiative transitions in terms of the spectral integral equation: Bottomonia

In the framework of the spectral integral equation, we consider the states and their radiative transitions. We reconstruct the interaction on the basis of data for the levels of the bottomonium states with J ^PC = 0⁻⁺, 1⁻⁻, 0⁺⁺, 1⁺⁺, 2⁺⁺ as well as the data for the radiative transitions γ (3S) → _γχbJ(2P) and γ(2S) → _γχbJ(1P) with J = 0, 1, 2. We calculate bottomonium levels with the radial quantum numbers n ≤ 6, their wave functions, and corresponding radiative transitions. The ratios Br[_χbJ(2P) → _γγ(2S)]/Br[_χbJ(2P) → _γγ(1S)] for J = 0, 1, 2 are found to be in agreement with data. We determine the component of the photon wave function using the data for the e ⁺ e ⁻ annihilation, e ⁺ e ⁻ → γ(9460), γ(10 023), γ(10 036), γ(10 580), γ(10 865), γ(11 019), and predict partial widths of the two-photon decays ηb0 → γγ, χb0 → γγ, χb2 → γγ for the radial excitation states below the threshold (n ≤ 3). The text was submitted by the authors in English.     

Signatures of anomalous couplings in boson pair production throughγγ collisions

We discuss possible New Physics (NP) effects on the processesγγ →W ⁺ W ⁻,ZZ, Zγ, γγ, HH which are observable inγγ collisions. Such collisions may be achieved through laser backscattering at a high energye ⁺ e ⁻ linear collider. To the extent that no new particles will be directly produced in the future colliders, it has already been emphasized that the new physics possibly hidden in the bosonic interactions, may be represented by the sevendim=6 operatorsO _W,O _BΦ,O _WΦ,O _UB,O _UW and (the last two ones being CP-violating). In this paper, we show that the above processes are sensitive to NP scales at the several TeV range, and we subsequently discuss the possibility to disentangle the effects of the various operators. Partially supported by the EC contract CHRX-CT94-0579     

Di-jet production in γ γ collisions at LEP2

The production of two high-p _T jets in the interactions of quasi-real photons in e ⁺ e ⁻ collisions at from 189 GeV to 209 GeV is studied with data corresponding to an integrated e ⁺ e ⁻ luminosity of 550 pb⁻¹. The jets reconstructed by the k _⊥ -cluster algorithm are defined within the pseudo-rapidity range −1<η<1 and with jet transverse momentum, p _T , above 3 GeV/c. The differential di-jet cross-section is measured as a function of the mean transverse momentum of the jets and is compared to perturbative QCD calculations. Deceased     

Signals of left-right supersymmetry ine + e − collisions

We study chargino and neutralino pair production at the Next Linear e⁺ e⁻ Collider in a supersymmetric left-right model. We investigateon- and off-resonance signals via the processes: and . These reactions could lead to observable signals as they compare with the background signal from W^± -pair production.     

Mass operator of an axion in a crossed field

The dominant one-loop electron contribution to the mass operator of an axion in a crossed field in the asymptotic limits of the parameters q ²/m _e ² and is calculated. The corresponding electromagnetic mass of the axion is compared with the quantum-chromodynamic mass due to mixing with π. Expressions are derived for the probability of pair creation a→e ⁺ e ⁻, and the fundamental conclusion is reached that refractive effects are present in the propagation of an axion in an external electromagnetic field. Zh. éksp. Teor. Fiz. 113, 1558–1565 (May 1998)     

Synchrotron and annihilation channels for axion production in an external electromagnetic field

We consider axion formation processes in the synchrotron (e ⁻→e ⁻ a) and annihilation (e ⁻ e ⁺→a) channels in a constant crossed field F _μν F^μν=Fμν*F ^μν =0, which approximates constant fields of other configurations in the ultrarelativistic asymptotic limit. The probability and intensity of axion emission are obtained, and we analyze the energy and field asymptotics. A comparison with the characteristic neutrino channel yields the constraints on the axion mass and the energy scale for Peccei-Quinn symmetry breaking. Possible astrophysical applications are discussed. Zh. éksp. Teor. Fiz. 112, 25–31 (July 1997)     

Λ<Subscript>b</Subscript>→Λℓ<Superscript>+</Superscript>ℓ<Superscript>-</Superscript> decay in universal extra dimensions

We study the exclusive Λ_b→Λℓ⁺ℓ^- decay in the Appelquist, Chang, Dobrescu model with a single universal extra dimension. We investigate the sensitivity of the branching ratio, lepton polarization and forward–backward asymmetry to the compactification parameter 1/R. We obtain the result that the branching ratio for the Λ_b→Λℓ⁺ℓ^- (ℓ=μ,τ) decay changes about 25% compared to the SM value when 1/R=250 GeV, and the zero position of the forward–backward asymmetry is shifted to the left compared to the SM result. Therefore, measurement of the branching ratio of Λ_b→Λℓ⁺ℓ^- decay and determination of the zero position of are very useful in looking for new physics in the framework of the UED models. PACS 12.60.-i; 13.30.-a; 14.20.Mr     

Squarks and gluinos at a TeV e + e − collider: testing the identity of Yukawa and gauge couplings in SUSY-QCD

Supersymmetry predicts the identity of Yukawa and gauge couplings in the QCD sector: . We examine whether the  Yukawa coupling can be determined, by methods complementary to LHC, by analyzing squark–gluino final states at a TeV e ⁺ e ⁻ collider.     

Bounds on neutrino mixing with exotic singlet neutrinos

We examine the effects of mixing induced non-diagonal light-heavy neutrino weak neutral currents on the amplitude for the process (with a=e, μ or τ). By imposing constraint that the amplitude should not exceed the perturbative unitarity limit at high energy , we obtain bounds on light-heavy neutrino mixing parameter sin² where is the mixing angle. In the case of one heavy neutrino (mass mξ) or mass degenerate heavy neutrinos, for Λ=1 TeV, no bound is obtained for mξ<0.50 TeV. However, sin² ≤3.8 × 10⁻⁶ for mξ=5 TeV and sin ≤6.0 × 10⁻⁸ for mξ=10 TeV. For Λ=∞, no constraint is obtained for mξ<0.99 TeV and sin² ≤3.8 × 10⁻² (for mξ=5 TeV) and sin² ≤9.6 × 10⁻³ (for mξ=10 TeV).