Contribution of the π<Superscript>0</Superscript>γ and ηγ intermediate states to vacuum polarization and the muon anomalous magnetic moment

Using new experimental data, we calculated, with a high precision, a contribution to the muon anomalous magnetic moment from the vacuum-polarization intermediate states π⁰γ and ηγ taking into account a correction for the trapezoidal rule: aμ(π⁰γ+aμ(ηγ)=(53.1± 1.5)×10^?11. We also determined a small contribution from the e⁺e^?π⁰, e⁺e^?η, and μ⁺μ^?π⁰ intermediate states, which was found to be equal to 0.5×10^?11.     

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.     

Using a chiral anomaly to determine the number of colors

The N_c dependence of PPPγ vertices, where P is a pseudoscalar meson and N_c is the number of colors, is analyzed with allowance for the N_c dependence of the quark charges. It is shown that the reactions Kγ → Kπ and π^±γ → π^±η and the decay η → π⁺π^?γ are the best processes for determining N_c. The cross section σ(π^?γ → π^?η) as measured by using the VES facility at IHEP agrees with the value of N_c=3.     

Application of the hidden local symmetry effective chiral Lagrangian to evaluation of the <Emphasis Type="Italic">ω</Emphasis>(782), <Emphasis Type="Italic">ϕ</Emphasis>(1020) → 5<Emphasis Type="Italic">π</Emphasis> decay widths

The amplitudes obtained from the effective chiral Lagrangian with anomalous terms based on hidden local symmetry are applied to the evaluation of the partial widths of the decays ω → 2π⁺2π^?π⁰ and ω → π⁺π^?3π⁰. Combining the Okubo-Zweig-Iizuka rule, applied to the five-pion final state, with the Adler condition of vanishing of the amplitude at the vanishing of four-momentum of any final pion in the chiral limit, the ? → 2π⁺2π^?π⁰ and ? → π⁺π^?3π⁰ decay amplitudes are also calculated. The partial widths of the above decays are evaluated, and the resonance excitation curves in e⁺e^? annihilation are obtained, assuming reasonable particular relations among the free parameters characterizing the anomalous terms of the Lagrangian. The evaluated branching ratios \(Br_{\phi \to \pi + \pi - 3\pi ^0 } \approx 2 \times 10^{ - 7} \) and \(Br_{\phi \to 2\pi + 2\pi - \pi ^0 } \approx 5 \times 10^{ - 7} \) are such that with the luminosity L = 500 pb^?1, attained at the DAΦNE ? factory, one may already possess about 1340 events of the decays ? → 5π.     

Signature splitting in two quasiparticle rotational bands of <Superscript>180,182</Superscript>Ta

The signature splittings in K^π = 1 ⁺: 7 /2[404] _π?9 /2[624] _ν, K^π = 0^?: 9 /2[514] _π?9 /2[624] _ν bands of ¹⁸⁰Ta and K^π = 0^?: 7 /2[404] _π?7 /2[503] _ν, K^π = 1^?: 5 /2[402] _π?3 /2[512] _ν, K^π = 1⁺: 7 /2[404] _π?9 /2[624] _ν bands of ¹⁸²Ta are analysed within the framework of two-quasiparticle rotor model. The phase as well as magnitude of the experimentally observed signature splitting in K^π = 1⁺ band of ¹⁸⁰Ta, which could not be explained in earlier calculations, is successfully reproduced. The conflict regarding placement of a 12 ⁺ level in K^π = 1 ⁺: 7 /2 ⁺[404] _π?9 /2 ⁺[624] _ν ground-state rotational band of ¹⁸⁰Ta is resolved and tentative nature of K^π = 0^?: 7 /2[404] _π?7 /2[503] _ν, K^π = 1⁺: 7 /2[404] _π?9 /2[624] _ν bands observed in ¹⁸²Ta is confirmed. As a future prediction for experimentalists, these two-quasiparticle structures observed in ¹⁸⁰Ta and ¹⁸²Ta are extended to higher spins.     

Polarisations-Korrelations-Messungen am Na24

An arrangement for the measurement of angular correlations betweenβ-particles and circular polarizedγ-radiation is described and a result on Na²⁴ is given. A correlation coefficientA=(+ 0,12± 0,03) was obtained, which indicates a ratio of Gamow-Teller to Fermi matrix elementM _G /M _F > 10.     

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.     

Tests of discrete symmetries with the neutral kaon system at the KLOE and KLOE-2 experiments

The KLOE-2 experiment continues and extends the program of its predecessor KLOE in the field of discrete symmetry tests with the K meson system, among other studies which comprise light meson spectroscopy, dark matter searches and γγ physics. Together, KLOE and KLOE-2 have recorded the largest sample (almost 8 fb^??1) of e⁺e^? collisions at the energy equal to ? meson mass, amounting to 2.4 × 10¹⁰ of produced ? mesons. We report on the latest results and ongoing analyses of KLOE and KLOE-2 concerning discrete symmetry tests and measurements of symmetry-violating observables. A measurement of the CPT violation sensitive asymmetry in semileptonic decays of K˙S with 1.7 fb^??1 of KLOE data will be presented, which improves the sensitivity w.r.t. previous measurements about twice. Moreover, status of direct tests of T and CPT in transitions of neutral kaons performed with the ? →K˙SK˙L → πeν, 3π⁰(2π) processes will be reported, followed by the search of the CP-violating decay K˙S → 3π⁰ using the data recently acquired by KLOE-2.     

Production of exotic Λ hypernuclei via mesonic beams

We study the production of neutron-rich hypernuclei _Λ ¹² Be, _Λ ¹⁶ C, and _Λ ¹⁰ Li by the (π^?, K⁺) and (K^?, π⁺) reactions in flight and treat two different mechanisms of production. The first mechanism is a two-step process with meson charge exchange (e.g., π^?p → π⁰n, π⁰p → K⁺Λ). The other mechanism is one-step production (π^?p → K⁺Σ^?) proceeding via a small Σ^? component, arising in Λ hypernuclei due to ΛN–ΣN coupling, as a doorway state. Typically, the two-step mechanism is more productive. The forward differential cross section of the ¹⁰B(π^?,K⁺) reaction is about 70 nb/sr at an incident momentum of 1.05 GeV/c. On the other hand, the one-step process can serve as a direct measurement of the Σ admixture if the two-step contribution is suppressed by a suitable choice of the reaction kinematics.     

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).     

Nonadiabatic theory of diamagnetic susceptibility of molecules

A nonadiabatic theory of diamagnetic susceptibility of molecules is presented in which the electrons and nuclei are considered to be a united system of charged particles whose motion is simultaneously per-turbed by a magnetic field. It is found that on separating out the translational motion of the molecule as a whole, there is certain freedom in choosing the phase of the wave function. Its optimum choice corresponds to the gauge of the vector potential with which two contributions opposite in sign to the magnetic susceptibility—the first order diamagnetism and the second order paramagnetism—have minimum magnitudes. Expressions for non-adiabatic calculations of the diamagnetic susceptibility of atoms and molecules are derived. The diamagnetic contributions to the energy of the hydrogen, helium, and lithium atoms, the hydrogen molecule, the π^?μ^?π⁺μ⁺ and p ^? K ^? p ⁺ K ⁺ mesomolecules, and the positronium molecule e ^? e ^? e ⁺ e ⁺ are calculated. The nonadiabatic contribution of the nuclear motion to the diamagnetic susceptibility amounts to 0.01–0.1% for ordinary atoms and molecules, is increased by several hundred times on passing to mesomolecules, and reaches 50% for the positronium molecule.     

Proximity effect of a superconductor on an antiferromagnetic metal

There should be two contributions to the pair breaking energy in an antiferromagnetic metal. The first, already discussed byde Gennes andSarma, is due to disorder on the magnetic sites. The second is a temperature dependent contribution from electron magnon scattering. This term is calculated for the temperature rangeT _N(J/μ)²?T?T _N and found to be of orderT ²/T _N. (T _N = Néel temperature,μ = Fermi energy,J = exchange coupling between conduction electrons and magnetic ions.)     

Search for superheavy hydrogen isotopes <Superscript>4,5</Superscript>H in reactions of pion absorption by <Superscript>10,11</Superscript>B nuclei

The results of searching for production of superheavy hydrogen isotopes ^4,5H in reactions of absorption of stopped π^? mesons by ^10,11B nuclei are reported. A peak near 3 MeV was observed in the missing mass spectra measured in the reactions ^10,11B(π^?, t⁴He)X, ¹⁰B(π^?, d⁴He)X, and ¹⁰B(π^?, t³He)X. A structure caused by two ⁵H states with the resonance energies E _R = 5.2 and 10.4 MeV was observed in the missing mass spectra measured in the reactions ¹¹B(π^?, d⁴He)X, ¹¹B(π^?, t³He)X, and ¹⁰B(π^?, d³He)X.     

Method for taking into account hard-photon emission in four-fermion processes

A method for taking into account hard-photon emission in four-fermion processes proceeding in the s channel is described. The application of this method is exemplified by numerically estimating one-loop electroweak corrections to observables (cross sections and asymmetries) of the reaction e^?e⁺ → μ^?μ⁺(γ) involving longitudinally polarized electrons and proceeding at energies below the Z-resonance energy.     

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.     

Energy and momentum losses of a magnetized plasma via familon emission

Familon emission from a dense magnetized plasma in the processes e^? → e^?φ and e^? → μ^?φ is investigated. The contribution of these processes to the energy losses of a supernova remnant is calculated. It is shown that, at a late stage of the cooling of a supernova remnant, the energy loss of a plasma via familon emission may become commensurate with the loss via neutrino emission. It is found that, because of asymmetry of familon emission in the process e^? → gm^?φ, there arises a force acting on the plasma.     

Intertwining Symmetry Algebras of Quantum Superintegrable Systems on Constant Curvature Spaces

A class of quantum superintegrable Hamiltonians defined on a hypersurface in a n+1 dimensional ambient space with signature (p,q) is considered and a set of intertwining operators connecting them are determined. It is shown that the intertwining operators can be chosen such that they generate the su(p,q) and so(2p,2q) Lie algebras and lead to the Hamiltonians through Casimir operators. The physical states corresponding to the discrete spectrum of bound states as well as the degeneration are characterized in terms of some particular unitary representations.     

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.     

Effect of <Emphasis Type="Italic">Z′</Emphasis>-mediated flavor-changing neutral current on <Emphasis Type="Italic">B</Emphasis> → <Emphasis Type="Italic">ππ</Emphasis> decays

We study the effect of Z′-mediated flavor-changing neutral current on the B → ππ decays. The branching ratios of these decays can be enhanced remarkably in the nonuniversal Z′ model. Our estimated branching ratios B(B ⁰ → π ⁰ π ⁰) are enhanced significantly from their standard model (SM) value. For g′/g = 1, the branching ratios B(B ⁰ → π ⁰ π ⁰) are very close to the recently observed experimental values and for higher values of g′/g branching ratios are more. Our calculated branching ratios B(B ⁰ → π ⁺ π ^?) and B(B ⁺ → π ⁺ π ⁰) are also enhanced from the SM value as well as the recently observed experimental values. These enhancements of branching ratios from their SM value give the possibility of new physics.     

Phenomenology of light- and strange-quark simultaneous production at high energies

This letter presents an extension of EPL116(2017)62001 to light- and strange-quark nonequilibrium chemical phase-space occupancy factors (γ_q,s). The resulting damped trigonometric functionalities relating γ_q,s to the nucleon-nucleon center-of-mass energies (\(\sqrt {{s_{NN}}} \)) looks very similar except different coefficients. The phenomenology of the resulting γ_q,s(\(\sqrt {{s_{NN}}} \)) describes a rapid decrease at \(\sqrt {{s_{NN}}} \) ? 7GeV followed by a faster increase up to ~20 GeV. Then, both γ_q,s become nonsensitive to \(\sqrt {{s_{NN}}} \). Although these differ from γ _s (\(\sqrt {{s_{NN}}} \))obtained at γ _q (\(\sqrt {{s_{NN}}} \))=1, various particle ratios including K⁺/π⁺, K^?/π^?, Λ/π^?, Λ?/π^?, Ξ⁺/π⁺, and Ω/π^?, can well be reproduced, as well. We conclude that γ_q,s(\(\sqrt {{s_{NN}}} \)) should be instead determined from fits of various particle yields and ratios but not merely from fits to the particle ratio K⁺/π⁺.