Deduction of the quantum numbers of low-lying states of the (e+e+e−e−) system from symmetry consideration

The features of the low-lying spectrum and the complete set of quantum numbers of each of the low-lying states of a (e⁺e⁺e⁻e⁻) system have been deduced based on symmetry.     

Measurement of the exclusive D(p,e+e−)3He and D(p, γ)3He reactions at 98 and 176 MeV

A high resolution magnetic pair spectrometer for medium energy photons has been used for studies of the exclusive (p, e⁺e⁻) and (p, γ) reactions on deuterium at 98 and 176 MeV. The (p, e⁺e⁻) cross sections, obtained at 40° and 80°, are compared with the corresponding data for the (p, γ) reaction measured with the same apparatus. At small virtual photon masses the (p, e⁺e⁻) cross sections show significant enhancement over what is expected from model calculations, a behaviour which has earlier been observed also for the ¹¹B(p, e⁺e⁻)¹²C reaction.     

First measurement of the exclusive (p,e+e−) reaction

We present the first data on the exclusive (p,e⁺e⁻) reaction in a nucleus. Cross sections for populating the ground state and first excited state in the residual nucleus are presented for the reaction ¹¹B(p, e⁺e⁻)¹²C at 98 MeV. The e⁺e⁻ momentum vectors were measured with a high-resolution magnetic pair spectrometer. The distributions of the virtual photon invariant mass and of the direction of the electron in the virtual photon rest system are compared with a simple single-nucleon model. The (p,e⁺e⁻) cross sections are compared with corresponding data for the (p, γ) reaction obtained with the same apparatus. The (p,e⁺e⁻) cross sections show substantial enhancement over what is expected from the simple model.     

CP-violation effect in neutralino pair production in e+ −e− annihilation and the electric dipole moment of the electron

It is shown that in the supersymmetric extensions of the standard electroweak theory, the threshold behaviour of the cross section of production of two different neutralinos in e⁺ −e⁻ annihilation may be sensitive to the violation of CP invariance by the neutral gaugino-higgsino mass term. The corresponding CP violation effect may be substantial quite far from the threshold. A relation (although rather indirect) between the form of the behaviour of this section in the threshold region and the value of the electric dipole moment of the electron may exist.     

Broadening of ρ(→ e+e−) meson produced coherently in the photonuclear reaction

The e ⁺ e ^? invariant mass distribution spectra are calculated to estimate the hadron parameters of the ρ meson produced coherently in the photonuclear reaction. The elementary reaction occurring in the nucleus is considered to proceed as γN → ρ ⁰ N; ρ ⁰ → e ⁺ e ^?. We describe the elementary ρ meson photoproduction by the experimentally determined reaction amplitude $f_{\gamma {\rm N} \to \rho ^0 {\rm N}}$ . The ρ meson propagator is presented by the eikonal form, and the ρ meson nucleus optical potential V _Oρ appearing in it is estimated using the “t?” approximation. The ρ meson nucleon scattering amplitude f _ρN extracted from the measurements is used to generate this potential. The calculated e ⁺ e ^? invariant mass distribution spectra are compared with those measured at Jefferson Laboratory. The calculated results for the transparency ratio are also presented.     

Rovibrational and energetic analysis of the hydroxyethynyl anion (CCOH−)

For the first time, high-level structural and rovibrational data are provided for the hyroxyethynyl anion, CCOH^?. CCOH^? is a promising molecule for interstellar detection even though no new anions have been observed in the interstellar medium for the past half-decade. The large dipole moment of the corresponding neutral radical may be key for its creation as has been hypothesised and supported for other anions known to exist in various astronomical environments. Highly accurate quartic force fields are employed where previous benchmarks have produced spectroscopic constants and anharmonic vibrational frequencies within 20 MHz and 1 cm^?1, respectively, of experiment. This same approach is applied here for CCOH^? and its deuterated isotopologue with the goal of assisting laboratory experiments and/or astronomical observers in the potential detection of this anion.     

Measurement of the strong coupling α S from the three-jet rate in e+e−-annihilation using JADE data

We present a measurement of the strong coupling α _S using the three-jet rate measured with the Durham algorithm in $\mathrm{e^{+}e^{-}}$ -annihilation using data of the JADE experiment at centre-of-mass energies between 14 and 44 GeV. Recent theoretical improvements provide predictions of the three-jet rate in $\mathrm{e^{+}e^{-}}$ -annihilation at next-to-next-to-leading order. In this paper a measurement of the three-jet rate is used to determine the strong coupling α _S from a comparison to next-to-next-to-leading order predictions matched with next-to-leading logarithmic approximations and yields a value for the strong coupling consistent with the world average.     

Measurement of the yields of positively charged particles at an angle of 35° in proton interactions with nuclear targets at an energy of 50 GeV

Momentum spectra of cumulative particles in the region of high transverse momenta (P _T ) in pA → h ⁺ + X reactions were obtained for the first time. The experiment in which this was done was performed at the SPIN setup (Institute for High Energy Physics, Protvino) in a beam of 50-GeV protons interacting with C, Al, Cu, and W nuclei. Positively charged particles were detected at a laboratory angle of 35° and in the transverse-momentum range between 0.6 and 3.7 GeV/c. A strong dependence of the particle-production cross section on the atomic number was observed. A comparison with the results of calculations based on the HIJING and UrQMD models was performed in the subcumulative region.     

Phase-shift analysis of π+ p-scattering in the energy region from 194 to 600 MeV

An energy-independent phase-shift analysis ofπ ⁺ p-scattering has been carried out at 16 energies in the region 194–600 MeV. The new data on elastic polarization, obtained in LNPI up to 1983, were included.     

Measurement of the average γ-ray multiplicity and the mean γ-energy in the photon cascades following the reaction154Sm(12C,4n)162Er

By unfolding theγ-γ coincidence spectra from the reaction¹⁵⁴Sm(¹²C, 4n)¹⁶²Er at a beam energy of 64 MeV the mean energy of the continuousγ-ray spectrum feeding the ground state rotational band was determined as about 1.2 MeV. The averageγ-ray multiplicity \(\bar v\) including the rotational band transitions was measured for each of the levelsJ through which the cascade passed. The values for \(\bar v\) were found to increase regularly from \(\bar v = 8\) forJ=4 to \(\bar v = 14\) forJ=18.     

Pion pair production in γ-γ collisions at low energy and the born cross section

It is shown that (i) there is a severe constraint on σ(γγ→π⁺π⁻/σ_Born imposed by phenomenological theory and (ii) the low-mass π⁺π⁻ enhancement observed in the reaction γγ→π⁺π⁻ comes from interference between the Born term and the correction term.     

Measurement of γp→K + Λ and γp→K + Σ 0 at photon energies up to 1.47 GeV

The reactions pK ⁺ and pK ^{+ 0} have been measured with the multiparticle detector system SAPHIR at ELSA in Bonn. Besides the differential cross sections the polarization and, for the first time, the ⁰ polarization have been determined in a photon induced reaction. All data are presented as functions of the photon energy (from threshold up to 1.47 GeV) and of the kaon production angle (0°–180°). The polarization of both and ⁰ is substantial at all energies and varies strongly with the production angle.This work is supported by the Bundesminister für Forschung und Technologie (BMFT), FK 06 BN 621 I     

Measurement of the strong coupling αS from the four-jet rate in e+e- annihilation using JADE data

Data from e⁺e^- annihilation into hadrons collected by the JADE experiment at centre-of-mass energies between 14 GeV and 44 GeV are used to study the four-jet event production rate as a function of the Durham jet algorithm’s resolution parameter y_cut. The four-jet rate is compared to QCD next-to-leading order calculations including resummation of large logarithms in the next-to-leading logarithmic approximation. The strong coupling measured from the four-jet rate is in agreement with the world average.     

Production ofμ − e + pairs in neutrino interactions in the SKAT bubble chamber experiment

The production of μe-pairs is studied in interactions of neutrinos with nuclei of heavy freon in the SKAT bubble chamber experiment. A rate of μ^? e ⁺ to charged current interactions above the charm threshold of \(R^{\mu ^ - e^ + } = (4.6 \pm 1.2) \cdot 10^{ - 3} \) is found. The properties of the observed μ^? e ⁺ events can be well described by assuming them to originate from the semileptonic decay of quasielastic produced charmed baryonsΛ _c and inclusive charmedD-meson production. The rates for these reactions are found to be (6.7±3.5)×10^?2 and (2.5±0.9)×10^?2, respectively. A total charmed particle production rate of (9.2±3.6)×10^?2 is calculated.     

Measurement of the total spectrum of electrons and positrons in the energy range of 300–1500 GeV in the PAMELA experiment with the aid of a sampling calorimeter and a neutron detector

A method based on the use of a sampling calorimeter was developed for measuring the total energy spectrum of electrons and positrons from high-energy cosmic rays in the PAMELA satellite-borne experiment. This made it possible to extend the range of energies accessible to measurements by the magnetic system of the PAMELA spectrometer. Themethod involves a procedure for selecting electrons on the basis of features of a secondary-particle shower in the calorimeter. The results obtained by measuring the total spectrum of cosmic-ray electrons and positrons in the energy range of 300–1500 GeV by the method in question are presented on the basis of data accumulated over a period spanning 2006 and 2013.

     

Measurement of thee + e −→π + π − π 0 ande + e −→ωπ + π − reactions in the energy interval 1350–2400 MeV

The cross sections fore ⁺ e ^?→π ⁺ π ^? π ⁰ ande ⁺ e ^?→ωπ ⁺ π ^? have been measured in the 1.35 ≦ \(\sqrt s \) ≦2.4 GeV range from 1900 nb^?1 collected by DM2 at DCI. The second process proceeds via a resonant state at ≈- 1660 MeV/c², ≈- 280 MeV/c² wide. The first one is larger than a VDM extrapolation from the ω-? peaks and, although does not show any clear structure, is compatible with the presence of the above resonance.     

Measurement of the LT-asymmetry in πelectroproduction at the energy of the Δ(1232)-resonance

The reaction p(e, e'p)π⁰ has been studied at Q² = 0.2 (GeV/c)² in the region of W = 1232MeV. From measurements left and right of , cross-section asymmetries ρ_LT have been obtained in forward kinematics ρ_LT( = 20^°) = (- 11.68±2.36_stat±2.36_sys) and backward kinematics ρ_LT( = 160^°) = (12.18±0.27_stat±0.82_sys) π⁰. Multipole ratios {S₁₊ ^* M₁₊}/| M₁₊|² and {S₀₊ ^* M₁₊}/| M₁₊|² were determined in the framework of the MAID2003 model. The results are in agreement with older data. The unusally strong negative {S₀₊ ^* M₁₊}/| M₁₊|² required to bring also the result of Kalleicher et al. in accordance with the rest of the data is almost excluded.