Results from a π−p slow proton trigger experiment at 12 GeV/c

A study of the reaction π^?p → X^?p based on 1.27 × 10⁶ events, corresponding to a mean sensitivity of 200 events/μb, is presented. Properties of the exclusive channels π^?p → π^?π⁰p, π⁺π^?π^?p, π⁺π^?π^?π⁰p, π⁺π⁺π^?π^?π^?p and π⁺π⁺π^?π^?π^?π⁰p are discussed.     

Lepton charge and model of weak interactions with μ-e transitions

The gauge model of weak interactions is proposed and μ^±?e^? transitions predicted by the model are discussed. Estimates are given for μ^±→e^? transitions on hadrons like K⁺→π^?μ⁺e⁺ with Γ (K⁺→π^?μ⁺e⁺) ? 10^?11Γ(K⁺ and μ^? capture on nuclei with W(μ^?→e⁺) ? 10^?12W(μ^? → ν). Single μ^± production in e^? beams with a cross section δ ～ 10^?42?10^?41 cm² is predicted.     

A study of hadronic decays of the ϒ′

We present a detailed study of the decays ?′ → π⁺π^?? and ?′ → π⁰π⁰?, where the ? decays subsequently to e⁺e^? or μ⁺μ^?. The results are obtained from a sample of 146 000 ?′ decays observed with the CUSB detector at the Cornell Electron Storage Ring. We derive branching fractions of (18.9 ± 2.6)% for ?′ → π′π^?? and (10.3 ± 2.3)% for ?′ → π⁰π⁰?, and determined partial widths for these decays. Invariant mass and angular distributions of both the π⁺π^? and π⁰π⁰ systems are presented. We also set a limit on the branching fraction for ?′ → η? of less than 0.2% at the 90% confidence level.     

The muon spectra from decays ofW- andZ-bosons produced ine + e −-collisions

The muon spectra from the decays ofW-andZ-bosons, produced ine ⁺ e ^?→W ⁺ W ^?,e ⁺ e ^?→Zγ,e ⁺ e ^?→ZZ ande ⁺ e ^?→ZH reactions have been obtained (H is the Higgs boson). It has been shown (in terms of Glashow-Weinberg-Salam theory) that the main source of muons are thee ⁺ e ^?→Zγ ande ⁺ e ^?→W ⁺ W ^? processes (over theW-boson production threshold). The contribution of thee ⁺ e ^?→ZZ ande ⁺ e ^?→ZH reactions to the inclusive muon spectra is small. It has been also shown, that it is possible to distinguish contributions of thee ⁺ e ^?→Zγ ande ⁺ e ^?→W ⁺ W ^? reactions if the decay muons move at a small angle to the initial electron momentum.     

Test of the Zweig rule in π−p interactions at 19 GeV/c

We have observed φ production in π^?p interactions at 19 GeV/c with (44±10) events in the final state φπ⁺π^?π^?p and (45±9) events in φK⁺K^?π^?p. The production ratios φπ⁺π^?π^?p/ωπ⁺π^?π^?p ≈ 0.005 and φK⁺K^?π^?p/?°K⁺K^?π^?p ≈ 0.45 agree with Zweig-rule expectations.     

A study of K−p interactions in deuterium in the c.m. energy range from 1.60 to 1.74 GeV

We present results of a K^?d bubble-chamber experiment at four K^? momenta between 680 and 840 MeV/c. The validity of the spectator model for the analysisof KN interactions in deuterium is discussed. Cross sections are determined for the reactions K^?p → Σ^?π⁺, K^?p → Σ⁺π^? and K^?p → Λπ⁺π^? and are compared to those obtain ed on free protons.     

Study of meson systems with isospin I = 3/2 at the VES setup

Preliminary results obtained by studying K ^? π ^?, K ^? π ^? π ⁰, and K ^? π ^? η systems in the VES experiment are presented. No statistically significant signals from possible resonances were observed in two- and three-particle mass spectra of doubly charged (sub)systems.     

Hyperspherical Three-Body Calculation for Exotic Atoms

Ground state energies of atomic three-body systems like negatively charged hydrogen, normal helium, positively charged-lithium, beryllium, carbon, oxygen, neon and negatively charged exotic- muonium and positronium atoms have been calculated adopting hyperspherical harmonics expansion method. Calculation of matrix elements of two body interactions needed in the hyperspherical harmonics expansion method for a three body system is greatly simplified by expanding the bra- and ket-vector states in the hyperspherical harmonics (HH) basis states appropriate for the partition corresponding to the interacting pair. This involves the Raynal–Revai coefficients (RRC), which are the transformation coefficients between the HH bases corresponding to the two partitions. Use of RRC become particularly essential for the numerical solution of three-body Schr?dinger equation where the two-body potentials are other than Coulomb or harmonic. However in the present work the technique is used for two electron atoms ¹H^?(p ⁺ e ^? e ^?), D^?(d ⁺ e ^? e ^?), Mu^?(μ ⁺ e ^? e ^?),⁴He(⁴ He ²⁺ e ^? e ^?),⁶Li(⁶ Li ³⁺ e ^? e ^?),¹⁰Be(¹⁰ Be ⁴⁺ e ^? e ^?),¹²C(¹² C ⁶⁺ e ^? e ^?),¹⁶O(¹⁶ O ⁸⁺ e ^? e ^?) etc. and the exotic positronium negative ion Ps ^?(e ⁺ e ^? e ^?) where the interactions are purely Coulomb. The relative convergence in ground state binding energy with increasing K _max for ²⁰Ne has been demonstrated as a representative case. The calculated energies at K _max ?=?28 using RRC’s have been compared with those obtained by a straight forward manner in some representative cases to demonstrate the appropriateness of the use of RRC. The extrapolated energies have also been compared with those found in the literature. The calculated binding energies agree within the computational error.     

Total and visible cross sections for multilepton events in e+e− collisions

We calculate cross section for e⁺e^? scattering into four-lepton final states such as e⁺e^?e⁺e^?, e⁺e^?μ⁺μ^?, μ⁺μ^?μ⁺μ^?, μ⁺μ^?τ⁺τ^?. We also give exclusive cross sectionsfor all cases where one or more lepton tracks are at large angles to the beams. The calculations are performed using a Monte Carlo event generator which takes into account the complete set of relevant lowest order Feynman diagrams.     

Leptonic polarization asymmetries ate + e − colliders inE 6 theories

We examine the left-right and azimuthal polarization asymmetries of lepton pairs produced ine ⁺ e ^? ande ^? e ^? interactions as probes of new physics resulting fromE ₆ theories. The asymmetries are calculated and compared for the processese ⁺ e ^?→µ ⁺ µ ^?,e ⁺ e ^?→e ⁺ e ^?,e ^? e ^?→e ^? e ^?, ande ⁺ e ^?→L ⁺ L ^? whereL is either anE ₆ exotic, mirror, or fourth generation heavy lepton. Our results show that lepton polarization asymmetries can be used to easily distinguish differentE ₆ models and can be used to distinguish among possible new heavy leptonsL.     

Screening effect of the coulomb interaction on the energy levels of atomic and molecular systems

The energies of atomic and molecular systems with a screened Coulomb interaction are expressed in terms of properties of the system with a conventional Coulomb interaction to the third order in the screening constant. The energy levels of an H atom, an H^? ion, and nonadiabatic systems, namely, the positronium ion e ⁺ e ^? e ^? and the positronium molecule e ⁺ e ⁺ e ^? e ^?, are calculated for screened Coulomb interactions of charged particles. It is demonstrated that, as the screening constant of the Coulomb interaction increases, the stability of the hydrogen atom, the H^? ion, and the positronium molecule e ⁺ e ⁺ e ^? e ^? decreases, whereas the stability of the positronium ion e ⁺ e ^? e ^? increases after a slight decrease.     

Two-photon annihilation into pion pair

The first experimental study of the interaction γγ → π⁺π^t- has been carried out in the region of ?(660) through the reaction e⁺e^? → e⁺e^?π⁺π^?. Based on two observed events, the γγ width of ?(660) is obtained to be Γ_?γγ = 9.6_?8.0^+12.3 keV. Applied on this, theory of P.C.D.C. anomaly predicts R_∞ = 5.8_?3.5^+3.2 for the asymptotic value of σ(e⁺e^? → hadrons)/σ(e⁺e^? → μ⁺μ^?).     

Multipion production below 1.1 GeV by e+e− annihilation

The production of multipion events by e⁺e^? annihilation has been measured at centre of mass energies 915,990 and 1076 MeV. Both channels e⁺e^?→π⁺π^?π^o and e⁺e^?→π⁺π^?π⁺π^? have been analysed. An energy threshold effect analysed. An energy threshold effect around 919 MeV (m_ω + m_π^o) has been evidenced for the π⁺π^?π^oπ^o channel and the cross section is consistent with the quasi two-body process e⁺e^?→ωπ^o. The cross section for π⁺π^?π⁺π^? is lower by an order of magnitude and increases with the energy.     

Multipion and strange particle photoproduction off neutrons up to 5.3 GeV

In a study of photoproduction at photon energies up to 5.3 GeV in a deuterium bubble chamber the reactions γn→pπ⁺π^?π^? and γn→pπ⁺π^?π^?π⁰ were analyzed. In these reactions production of the resonances Δ⁺⁺, Δ⁰, ?⁰, ω and A₂^? was observed. Photoproduction of strange particles was investigated and cross sections for the reactions γn→ΛK⁺π^?, Σ^?K⁰π⁺, pK^?K⁰, ΛK⁰π⁺π^? and ΛK⁺π^?π⁰ are presented. Production of Σ^?(1385) and K¹⁰(890) was observed.     

The stability boundary of four-particle mesomolecules

Multiparametric variational calculations of the ground-state energy of symmetric four-particle mesomolecules of the type X ⁺ Y ⁺ X ^? Y ^? as a function of masses M and m of particles X and Y are carried out. A basis consisting of 3200 Gaussian functions depending on all six interparticle distances is used. Calculations are carried out with the optimization of 1200 nonlinear parameters of the first 200 basis functions. As opposed to mesomolecules of the type X ⁺ X ⁺ Y ^? Y ^?, which are stable for all values of masses M and m in X ⁺ Y ⁺ X ^? Y ^? systems, are stable with respect to dissociation if the ratio of the masses of particles X and Y in them satisfies the condition 0.472≤M/m≤2.12. Hence it follows that four symmetric mesomolecules of the type considered (π⁺μ ⁺π^?μ^?, t ⁺ d ⁺ t ^? d ^?, p ⁺ K ⁺ p ^? K ^?, and d ⁺ p ⁺ d ^? p ^?) and 84 various asymmetric mesomolecules of the type X ⁺ Y ⁺ Z ^? T ^? are knowingly stable with respect to dissociation. For mesomolecules of the type X ⁺ Y ⁺ X ^? Y ^?, which are stable with respect to dissociation, mathematical expectations of their physical quantities depending on interparticle distances that specify averaged geometrical structures of these systems are calculated and their dependence on the masses of particles M and m is studied.     

The π N → e +e−N reaction close to the vector-meson production threshold

The π^? p→e ⁺ e ^? n and π⁺ n→e ⁺ e ^? p reaction cross sections are calculated below and in the vicinity of the vector-meson (?⁰,ω) production threshold. These processes are largely responsible for the emission of e ⁺e^? pairs in pion-nucleus reactions and contribute to the dilepton spectra observed in relativistic heavy ion collisions. They are dominated by the decay of low-lying baryon resonances into vector-meson-nucleon channels. The vector mesons materialize subsequently into e ⁺ e^? pairs. Using πN→?⁰ N and πN→ωN, amplitudes calculated in the center of mass energy interval 1.4 < √s<1.8 GeV, we compute the π^? p→e ⁺ e ^? n and π⁺ n→e ⁺ e ^? p reaction cross sections in these kinematics. Below the vector-meson production threshold, the π⁰?ω interference in the e ⁺ e^? channel appears largely destructive for the π^? p→e ⁺ e ^? n cross section and constructive for the π⁺ n→e ⁺ e ^? p cross section. The pion beam and the HADES detector at GSI offer a unique possibility to measure these effects. Such data would provide strong constraints on the coupling of vector-meson-nucleon channels to low-lying baryon resonances.     

Optimal Hamiltonian of internal motion of an atomic-molecular system in a magnetic field

The effect of a uniform magnetic field on the state of an atomic-molecular system considered as a united system of N particles (without separation of the motion of acoelightac and particles) is analyzed. It is shown that the Hamiltonian of the internal motion of the system in the magnetic field contains (N-1)(N-2)/2 arbitrary parameters corresponding to the coefficients of the gauge transformation of the vector potential. A method of calculation of the optimal values of these coefficients based on the requirement for the minimum diamagnetic correction to the energy is proposed. New formulas for the diamagnetic susceptibility of atomic-molecular systems are obtained that take into account the simultaneous perturbing effect of the magnetic field on the motion of all particles. The theory is applied for calculation of the diamagnetic susceptibilities of the H, He, Li, and Be atoms; the muonic analogues of helium atoms ^∞He²⁺µ^? e ^?,⁴He²⁺µ^? e ^?, and ³He²⁺µ^? e ^?; and the positron-containing systems t ⁺ e ⁺ e ^? e ^?, d ⁺ e ⁺ e ^? e ^?, p ⁺ e ⁺ e ^? e ^?, µ⁺ e ⁺ e ^? e ^?, and e ⁺ e ⁺ e ^? e ^?, with regard for the motion of all particles.     

Analysis of e + e −→π+π−π+π− and e + e −→π+π−π0π0 processes in the energy range of \sqrt 2 = 0.98 - 1.38 GeV in experiments with a spherical neutral detector

The cross sections of the e ⁺ e ^?→π⁺π^?π ⁺π^?, e ⁺ e ^?→π⁺π^?π⁰π ⁰, and e ⁺ e ^?→ωπ→ π⁺π^?π ⁰π⁰ processes, as well as the e ⁺ e ^?→π⁺π^?π⁰π⁰ process with subtracted contribution of the ωπ intermediate state, are measured in experiments with a spherical neutral detector on the VEPP-2M collider in the energy range 0.98–1.38 GeV. About 41 000 events of the e ⁺ e ^?→π⁺π^?π⁺π ^? process and more than 54 000 events of the e ⁺ e ^?→π⁺π ^?π⁰π⁰ process have been selected in experiment. The statistical error in determining the cross section is 2–20%, while the systematic error is 7 and 8%.     

Limits on the couplings of ϱ′ (1300 Me) and rhov;″ (1700 MeV) to the photon and to the (ππ) system

The analysis of the reaction e⁺e^?→π⁺π^? measured at the e⁺e^? colliding beam machine ADONE shows that, if ?′ and ?″ exist, the cross sections compare as follows (taking the ? as the reference point): $\text{σ(}\text{e}{}^{\mathrm{+}}\text{e}{}^{\mathrm{?}}\text{→ ? → π}{}^{\mathrm{+}}\text{π}{}^{\mathrm{?}}\text{)}$: σ(e⁺e^? → ?′ → π⁺π^?): σ(e⁺e^? → ?″ → π⁺π^?) = 1: (7 ± 4) × 10^?3: (1 ± 5) × 10^?4. The square of the product of their couplings to the photon (γ_?) and the γγ system (g_?ππ) are derived.