On the binding of atoms with antiatoms

The stability of X⁺Y⁺X^?Y^? Coulomb molecules consisting of X⁺Y^? atoms and X^?Y⁺ antiatoms to dissociation is studied. On the basis of multiparameter variational calculations, it is found that such molecules are stable to dissociation into X⁺X^? atoms and Y⁺Y^? antiatoms if the mass ratio of particles X and Y lies in the range 0.4710<m _X /m _Y <2.1231. The e⁺e⁺e^?e^?, π⁺μ⁺π^?μ^?, t⁺d⁺t^?d^?, p⁺K⁺p^?K^?, and d⁺p⁺d^?p^? molecules satisfy this condition.     

Separation of electrons and pions in the SND detector calorimeter

A method is developed for discriminating between e⁺e^? → e⁺e^? and e⁺e^? → π⁺π^? events in the center-of-mass (cms) energy range of 0.5 to 1.0 GeV by energy deposition in the electromagnetic calorimeter of the SND detector using a machine learning algorithm. Identification efficiencies for e⁺e^? → e⁺e^? and e⁺e^? → π⁺π^? events are 99.6 and 99.8%, respectively.     

Analytic calculation of feynman amplitudes

A new method is proposed for calculating amplitudes of processes involving spin-1/2 fermions. The method is based on the use of the isotropic-vierbein vectors in Minkowski space and the basis spinors associated with them. The amplitudes for the electron-positron interaction processes e^?e⁺ → ff and e^?e⁺ → W^?W⁺ and the amplitude for one of the possible diagrams for the process e⁺e^? → e⁺e^?e⁺e^?e⁺e^? are calculated in order to test and illustrate the potential of the method.     

Analysis of the production of Higgs boson pairs at the one-loop level in the minimal supersymmetric standard model

Within theminimal supersymmetric standardmodel, the amplitudes and total cross sections for the processes e ⁺ e ^? → hh, e ⁺ e ^? → hH, e ⁺ e ^? → HH, and e ⁺ e ^? → AA are calculated in the first order of perturbation theory with allowance for a complete set of one-loop diagrams in the m _e → 0 approximation. Analytic expressions are obtained for the quantities under consideration; numerical results are presented in a graphical form. It is shown that the cross section for the process e ⁺ e ^? → hh is larger than those for the other processes (and is on the same order of magnitude as the cross section for the corresponding processes in the Standard Model). In the case of the collision energy equal to √s = 500 GeV, an integrated luminosity in the region ∫ ? ≥ 500 fb^?1, and a longitudinal polarization of the e ⁺ e ? beams used, 520, 320, and 300 production events are possible in the processes e ⁺ e ^? → hh (at M _h = 115 GeV), e ⁺ e ^? → HH, and e ⁺ e ^? → AA (at M _H,A = 120 GeV), respectively. Even at M _H,A ≈ 500 GeV and √s = 1.5 TeV, not less than 200 events for each of the processes can be accumulated. The cross section for the process e ⁺ e ^? → hH is small (about 10^?2 fb), which complicates the detection of the sought signal significantly.     

Zur Theorie von Systemen aus drei Teilchen mit Coulomb-Wechselwirkung

The wave functions of muon molecules as well as of the corresponding electron molecules and of the systeme ⁺ e ^? e ⁺ have been approximated by simple analytical functions, the best choice of parameter values being obtained by straightforward variational procedure. The results are discussed in some detail and binding energies tabulated.     

Pseudoscalar Higgs boson in experiments at <Emphasis Type="Italic">e</Emphasis><Superscript>+</Superscript><Emphasis Type="Italic">e</Emphasis><Superscript>−</Superscript> colliders

The potential of experiments at e ⁺ e ^? colliders to search for a signal of a new pseudoscalar Higgs boson and to study its CP properties is analyzed. A new Higgs boson coupling to the b quark and τ lepton, which is parameterized in a model-independent way as m _b /v(a + iγ₅ b), is chosen to be an indicator of its CP nature. We study the e ⁺ e ^? → τ⁺τ^?vv, e ⁺ e ^? → b \(\bar b\)vv, and e ⁺ e ^? → e ⁺ e ^? b \(\bar b\) processes highly sensitive to anomalous Higgs boson couplings due to the dominant contributions from the vector boson fusion processes W*W* → H and Z*Z* → H in the central region. It is shown that the study of polarization of particles in the final state could help to separate the contributions from the scalar and pseudoscalar Higgs bosons. For instance, the consideration of the cascade decays of τ leptons in the e ⁺ e ^? → τ⁺τ^?vv process allows one to determine reliably the CP state of the Higgs boson as well as the value and the sign of the b parameter. As a result of our analysis, we develop a search strategy for a signal of a new pseudoscalar Higgs boson in future experiments at linear e ⁺ e ^? colliders, which will allow one to understand the CP nature of the Higgs boson and set the bounds on its couplings to fermions.     

Measurement of cross sections for processes involving <Emphasis Type="Italic">e</Emphasis><Superscript>+</Superscript><Emphasis Type="Italic">e</Emphasis><Superscript>−</Superscript> annihilation to hadrons at the VEPP-2M collider

Results obtained by measuring, in experiments at the VEPP-2M e ⁺ e ^? collider with the CMD-2 and SND detectors at the Novosibirsk Institute of Nuclear Physics, cross sections for e ⁺ e ^? → hadrons annihilation processes at energies in the range 360 ≤ √s ≤ 1380 MeV are surveyed. The measured cross sections and the vector-meson parameters deduced from an analysis of these cross sections are presented. The cross section for the process e ⁺ e ^? → π ⁺ π ^? is compared with the spectral function for the decay τ ^? → π ^? π ⁰ ν _τ.     

On accurate computations of slowly convergent atomic properties in few-electron ions and electron-electron correlations

We discuss an approach to accurate numerical computations of slowly convergent propertiesin two-electron atoms/ions which include the negatively charged Ps^? (e^?e⁺e^?)and H^? ions, Heatom and positively charged, helium-like ions from Li⁺ to Ni²⁶⁺. All these ions areconsidered in their ground 1¹S-state(s). The slowly convergent properties selected inthis study include the electron-nulceus (r^2k_eN) and electron-electron (r^2k_ee) expectation values for k = 2, 3, 4 and 5.     

Effects of four-fermion contact interactions in the Bhabha process at linear electron-positron colliders

For the case of longitudinally polarized primary beams, effects are investigated that are induced by four-fermion contact interactions in the process e⁺e^? → e⁺e^? occurring at linear electron-positron colliders of energy in the range \(\sqrt s = 0.5 - 1 TeV\). Model-independent constraints on the parameters of four-fermion contact interactions are obtained. It is shown that the sensitivity of the Bhabha process to the parameter Λ_LR is considerably higher than the sensitivity of the leptonic process e⁺e^? → μ⁺μ^?; at the same time, the sensitivities of these processes to the parameters Λ_RR and Λ_LL are commensurate.     

CP violation at colliders

The prospects of experimental detection ofCP violation ate ⁺ e ^? and\(pp/p\bar p\) 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\(t\overline t \) andW ⁺ W ^? production and decay is also described.     

Two-photon production of vector resonance in <Emphasis Type="Italic">e</Emphasis><Superscript>+</Superscript><Emphasis Type="Italic">e</Emphasis><Superscript>−</Superscript> collisions

A parameterization of the amplitude of the two-photon production of 1⁺⁺ and 1^?+ vector resonances V in the e ⁺ e ^? → e ⁺ e ^? V reaction has been obtained. The differential (in momentum transfer) scattering cross section dσ/dQ ² has been found for this reaction in the equivalent-photon approximation. The result obtained is model-independent.     

Proc ess es e+ e− → cccc and e+ e− → J/ψ + gg at $$\sqrt s = 10.59 G eV$$

Experimental data obtained by the BELLE Collaboration for inclusive J/ψ production in the processes e⁺e^? → J/ψ + gg and e⁺e^? → J/ψ + cc are discussed. These data are compared with the predictions of perturbative QCD that were obtained by two methods, that which employs information about the J/ψ wave function and that which relies on the hypothesis of quark-hadron duality exclusively. Both computational methods yield results that disagree with the experimental data considerably. The dependence of the cross section for the process e⁺e^? → J/ψ + gg on the effective gluon mass is studied. The cross section for the production of doubly charmed baryons Ξ _cc ^* is estimated.     

Determination of quark-antiquark component of the photon wave function for <Emphasis Type="Italic">u,d, s</Emphasis> quarks

Based on the data for the transitions π⁰, η, η′ → γγ*(Q²) and reactions of the e⁺e^? annihilations e⁺e^? → ρ⁰, ω, ? and e⁺e^? → hadrons at 1<E _e+e? <3.7 GeV, we determine the light-quark components of the photon wave function \(\gamma * (Q^2 ) \to q\bar q(q = u,d,s)\) for the region 0 ? Q² ? 1 (GeV/c)².     

Energy scan of cross sections for <Emphasis Type="Italic">e</Emphasis><Superscript>+</Superscript><Emphasis Type="Italic">e</Emphasis><Superscript>–</Superscript> annihilation into quarkonia and light hadrons in the Belle experiment

The cross sections of the reactions e⁺e^– → ?(nS)π⁺π^? (n = 1, 2,3) and e⁺e^– → h _b (nP)π⁺π^? (n = 1, 2) are measured as a function of the cms collision energy from their thresholds up to 11.02 GeV using the data of the Belle experiment operating at the KEKB e⁺e^– collider. The peaks of the ?(10 860) and ?(11020) resonances are observed in the cross sections with an insignificant contribution of the continuum. The decay ?(11020) → h _b (nP)π⁺π^? is found to fully proceed through intermediate isovector states Z _b (10610) and Z _b (10650).     

37 Years with the light scalar mesons. The learned lessons

Attention is paid to the production mechanisms of light scalars that reveal their nature. We reveal the chiral shielding of the σ(600) meson. We show that the kaon loop mechanism of the ? radiative decays, ratified by experiment, is four-quark transition and points to the four-quark nature of light scalars. We show also that the light scalars are produced in the two photon collisions via four-quark transitions in contrast to the classic P wave tensor qq? mesons that are produced via two-quark transitions γγ → qq?. We study the mechanism of production of the light scalar mesons in the D _s ⁺ → π⁺π^? e ⁺ν decays: D _s ⁺ → ss?e ⁺ν → [σ(600) + f ₀(980)]e ⁺ν → π⁺π^? e ⁺ν, and compare it with the mechanism of production of the light pseudoscalar mesons in the D _s ⁺ → (η/η′)e ⁺ν decays: D _s ⁺ → ss?e ⁺ν → (η/η′)e ⁺ν. As a result we find support to four-quark nature of light scalars. In the end, we outline the future research program.     

Anomalous magnetic moment of the muon in the left-right model

The effect of Higgs bosons on the anomalous magnetic moment of the muon is considered within the model that is based on the SU(2)_L×SU(2)_R×U(1)_B–L gauge group and which involves a bidoublet and two triplets of Higgs fields (left-right model). For the Yukawa coupling constants and the masses of Higgs bosons, the regions are found where the model leads to agreement with experimental results obtained at the Brookhaven National Laboratory (BNL) for the anomalous magnetic moment of the muon. In order to explore corollaries from the constraints obtained for the parameters of the Higgs sector, the processes e⁺e^? → μ⁺μ^?, τ⁺τ^? and μ⁺μ^? → μ⁺μ^?, τ⁺τ^? are considered both within the left-right model and within the model involving two Higgs doublets (two-Higgs-doublet model). It is shown that, if the mass of the lightest neutral Higgs boson does indeed lie in the range 3.1–10 GeV, as is inferred from the condition requiring the consistency of the two-Higgs-doublet model with the data of the BNL experiment, this Higgs boson may be observed as a resonance peak at currently operating e⁺e^? colliders (VEPP-4M, CESR, KEKB, PEP-II, and SLC). In order to implement this program, however, it is necessary to reduce considerably the scatter of energy in the e⁺ and e^? beams used, since the decay width of the lightest neutral Higgs boson is extremely small at such mass values. It is demonstrated that, in the case of the left-right model, for which the mass of the lightest neutral Higgs boson is not less than 115 GeV, the resonance peak associated with it may be detected at a muon collider.     

Possible check of neutral weak vector-bosons that couple to μ+μ− only

In connection with recent assumptions, that weak vector-bosons might couple only toμ ⁺ μ ^? currents (and not toe ⁺ e ^?-ones) the question arises, how to check these bosons, since no collidingμ ⁺ μ ^? beams are available. We have shown in this paper that this check could be performed by means of the resonance appearing in a pair production process fromμ-beams and that this process would work atμ-energies beyond 20 Bev.     

Effect of FCNC mediated <Emphasis Type="Italic">Z</Emphasis> boson on lepton flavor violating decays

We study the three body lepton flavor violating (LFV) decays μ ^?→e ^? e ⁺ e ^?, \(\tau^{-} \to l_{i}^{-} l_{j}^{+} l_{j}^{-}\) and the semileptonic decay τ→μφ in the flavor changing neutral current (FCNC) mediated Z boson model. We also calculate the branching ratios for LFV leptonic B decays, B _d,s →μe, B _d,s →τe, B _d,s →τμ and the conversion of muon to electron in Ti nucleus. The new physics parameter space is constrained by using the experimental limits on μ ^?→e ^? e ⁺ e ^? and τ ^?→μ ^? μ ⁺ μ ^?. We find that the branching ratios for τ→eee and τ→μφ processes could be as large as \({\sim}{\mathcal{O}}(10^{-8})\) and \(\mathrm{Br}(B_{d,s} \to \tau \mu,~ \tau e) \sim {\mathcal{O}}(10^{-10})\). For other LFV B decays the branching ratios are found to be too small to be observed in the near future.     

Proj ect for m easuri ng th e n eutro n el ectromag n etic form factor i n th e r eactio n e+ e− → n$$ \bar n $$ at th e VEPP-2000 collid er

A project aimed at measuring the neutron electromagnetic form factor in the reaction e ⁺ e ^? → n \(\bar n\) with the SND detector at the VEPP-2000 e ⁺ e ^? collider is presented. The results obtained for the time resolution of the NaI(Tl) counter using flash-ADC are reported along with estimates of the efficiency of separation of neutron-antineutron events.     

Investigation on self activated and copper activated zinc sulphide

The diamagnetic susceptibility of zinc sulphide decreases on heat treatment and becomes less temperature dependent. The susceptibilities or the differences in susceptibilities of the pure and activated samples do not obey Curie Law. The susceptibility follows a relation of the typeX _T =X ₀ +X ₁ e ^?E/KT in which bothX ₀ andX ₁ have the same sign.X ₀ is interpreted as true diamagnetic susceptibility of the sample and gradually increases in value with activation,X ₁ depends on the particle size and is found to decrease with the increase in particle size. This is interpreted as being due to surface electrons.“E” as measured in this way is found to be of the order of 0·01 ev. in all cases. Thus“E” seems to be the average surface trap depth of zinc sulphide. It has also been found that in zinc sulphide with low copper concentration the luminescent centres are diamagnetic; copper ions are present presumably in substitutional positions. For zinc sulphide containing high concentration of copper, the presence of paramagnetic centres are detected. It is suggested that in this case copper is present not only at the regular lattice positions acting as luminescent centre but also settles at special lattice sites like dislocation jogs.