A unified formalism for γγ→meson and ψ-γX with possible tests for hybrid and gluonic hadrons

The couplings of conventional and hybrid mesons to (real and virtual) and their production amplitudes in M are described in a unified manner. Existing results for heavy quarks are recovered, extensions to light quarks and to virtual couplings are made and phenomenological applications discussed. In particular we discuss relativistic corrections to 0⁺, 1⁺, 2⁺ for both real and virtual photons and offer a resolution to a long standing puzzle in perturbative QCD concerning the helicity structure of 2⁺⁺. We suggest that the production off ₂ (1720) involves gluons in an essential way or that this meson hasJ2.     

Investigation of nematic order by coherent neutron scattering

The mathematical relationship between the orientational order parameters and the coherent neutron scattering cross section for a nematic liquid crystal is given. For deuterated para-azoxyanisole the single-molecule part of the cross section is evaluated within the meanfield approximation and combined with experimental results to give information about molecular orientational order in terms of P ₂, P ₄ and P ₆. Both P ₂ and P ₄ are found necessary for describing the molecular order. Discrepancies between experimental and theoretical results are interpreted as possibly reflecting the inadequacy of the meanfield theory of Maier and Saupe.     

Extended operator expansion method for neutrinoless double beta decay

Reliable calculations of nuclear matrix elements are a prerequisite for the determination of the effective neutrino mass and other particle physics parameters from neutrinoless double beta decay. Here, the operator expansion method is improved by including Coulomb, tensor and central interactions simultaneously. Furthermore, the formalism of the OEM is extended to those matrix elements necessary to extract the right-handed parameters and from 0 decay. OEM includes the dependence of the nuclear matrix elements on the intermediate states implicitly and can therefore be understood as a step beyond the closure approximation. Numerical studies are carried out for the isotope⁷⁶Ge combining the OEM expressions with ground-state wave functions calculated within a proton-neutron quasiparticle Random Phase Approximation (pn-QRPA) model. The influence and relative importance of central, tensor and Coulomb interactions is investigated. Within the OEM, contributions from the Coulomb force are found to be negligible in 0 decay, while the tensor force leads to a moderate change of the results, of the order of (10–30)%, giving a better agreement between sets of calculations which employ different NN-interactions. Generally, results of the OEM+QRPA calculation are similar to previous calculations of 0 decay matrix elements, indicating that 0 decay is not sensitive to model approximations and might therefore be more accurately calculated than the strongly suppressed 2 decay matrix elements.     

Rescattering mechanisms for\bar p p→φX and the OZI rule re-examined

The OZI suppressed reactions¯pp and¯pp are reanalyzed, evaluating the unitarity contributions from two meson intermediate states with full spin, partially correcting earlier results. An estimate for¯pp without spin is also given. Together with earlier VDM results for¯pp the conservative estimates reported here easily explain the observed rates for all the meson channels considered.It is a pleasure to thank the following colleagues for numerous discussions: C. Amsler, D. Buzatu, O. Gortchakov, F. Lev, J.-M. Richard and M.G. Sapozhnikov.     

Diffractive production of ρ-mesons and of ρπ-systems by neutrinos and antineutrinos on protons

Evidence is presented for diffractive production of -mesons and of -systems invp and chargedcurrent interactions. In the (anti-)neutrino energy range 10 GeVE _v <60 gev=" the=" cross=" sections=" for=" diffractive="> and diffractive production are found to be (0.64±0.14 (stat.)±0.08 (syst.))% and (0.28±0.08 (stat.)±0.04 (syst.))% of the charged-current cross section. The diffractive signal is consistent with being entirely due to diffractivea ₁ production. However, the data cannot distinguish between diffractivea ₁ and diffractive nonresonant production. The experimental distributions ofW, Q ²,x _Bj andy _Bj for diffractive and events are consistent with model predictions.     

Aspects of χ and ψ production in polarized proton-proton collisions

Several topics of relevance to low transverse momentum and _1,2(c ) production in polarized proton-proton collisions are discussed. The leadingO( _S ³ ) contributions to the lowp _{T 1} production cross-sections viagg, qg, andq initial states are calculated as well as the corresponding spin-spin asymmetries. We find that ₁ production increases relative to direct and ₂ production, providing up to 25% of the observablee ^* e ^– pairs arising from decays inpp collisions at s=500 GeV. The spin-dependence of ₁ production, however, is much smaller than for either direct or ₂ production and so will likely be far less useful than either process in probing the polarized gluon structure function of the proton. A subset of theO( _S ³ ) radiative corrections to ₂ production involving initial state quarks are also performed and compared to leading ordergg₂ predictions.     

The structure of28Si above 10 MeV excitation energy I: gamma-decay modes and radiative widths of levels

The systematics of-decay modes and radiative widths of highly excited states in²⁸Si has been extended by taking-ray spectra on 60 resonances of the²⁷Al(p,) reaction in the range 1097 keVE _p 4492 keV (12643 keVE _x 15915 keV) and on the²⁴Mg(,) resonances atE =3355, 3431, 4003 keV (E _x =12860, 12925, 13 415 keV). The-decay modes of levels in the sub-resonance region (E _x =10–12.5 MeV) were studied with both the²⁷ A1(p, ) reaction and the²⁷ A1(d, n) reaction at E_d=4,5,6 MeV. Information on radiative widths of levels was obtained by measuring the resonance strengthsS =(2I+1) _p / for 52 resonances of the²⁷Al(p, ) reaction with an emphasis on prospective T=1 states.     

Photon-photon luminosities in relativistic heavy ion collisions at LHC energies

Effective – luminosities are calculated for various realistic hadron collider scenarios. The main characteristics of photon-photon processes at relativistic heavy-ion colliders are established and compared to the corresponding –-luminosities ate ⁺-e ^– — and future photon linear colliders (PLC). Higher order corrections as well as inelastic processes are discussed. It is concluded that feasible high luminosity Ca–Ca collisions at the Large Hadron Collider (LHC) are an interesting option for – physics up to about 100 GeV – CM energy.     

Search for an enhanced production of low energy pions in C(p, π+)X,Cu(p, π+)X,and Cu(p, π∘)X reactions for 300 MeV≦Tp≦400 MeV

The observation of an enhancement in the production of low energy pions in the Cu(p, ⁺)X reaction is confirmed. The width of the bump is about 5 MeV around 350 MeV. A similar enhancement appears at 330 MeV for C(p, ⁺)X but the width has not been measured. An attempt to observe this behaviour in Cu(p, )X is described. From the data one cannot conclude about the existence of a structure around 350 MeV proton energy. The lack of resolution in the spectrometer may have washed out the small effect expected from ⁺ measurements.     

Multi-strange systems in relativistic mean fields

Characteristics of multi- hypernuclei are investigated within the relativistic mean-field theory. Both linear and nonlinear models and a variety of couplings fitted to ordinary hypernuclei have been investigated. All the parametrizations used in the present work predict qualitatively similar dependence of the studied quantities (rms radii, binding energies, densities) on a number of hyperons.Deceased on May 5, 1991     

A mini transmissionγ-ray Compton polarimeter and measurements of the sign of magnetic moments of radioactive nuclei

A mini transmission-ray Compton polarimeter was developed for the measurement of the sign of magnetic moments of radioactive nuclei with low-temperature nuclear orientation. The signs of the magnetic moments of the following isotopes were determined:¹⁹³Os [=+0.7297(16) _N];^191m Ir [=+6.20(9) _N];¹⁹²Ir [=+1.924(10) _N];¹⁹⁴Ir [=+0.39(1) _N];^195m Pt [=–0.605(15) _N].Dedicated to Prof. Dr. P. Kienle on the occasion of his 60th birthday     

Photon-deuteron diffractive scattering

One expects a similarity of the energy dependence of the difference _tot(*p)– _tot(*n) for virtual (deep inelastic scatteringQ ²m ²) and real (Q ²=0) photons. Previous analysis of D structure functions with allowence for nuclear shadowing (NS) in the deuteron has led to conclusion that _tot(*p)– _tot(*n)<0>x<0.015. the=" early=" evidence=" from=" the=" real=" photoproduction=" data="> _tot(p)– _tot(n)<0. we=" critically=" reexamine=" determinations=" of=" the="> _tot(p)– _tot(n), using more accurate calculations of NS correction to _tot(D), and discuss a possibility of _tot(n) _tot(p) at moderately high energies.     

Observation of isomeric states in197Bi

The high spin states of¹¹⁹Te, populated in¹¹⁰Pd(¹³C,4n) and¹¹⁰Pd(¹²C,3n) reactions, have been studied through -ray spectroscopy. The level scheme has been established upto a spin of 55/2. Three-quasiparticle states, based on g² _7/2h_11/2 and g_7/2d_5/2h_11/2 configurations, have been identified. The 35/2 and 39/2 states are suggested to be the fully aligned states constituted by five valence h_11/2 ³, g_7/2, d_5/2 quasiparticles.     

Influence of resonances on Bose-Einstein correlations of identical pions

The influence of resonances on narrow pair correlations of identical pions is considered in detail. It is shown that kinematic or dynamic restrictions on resonance momenta lead to a substantial anisotropy of the correlation function; variables allowing one to reveal this anisotropy are proposed. An upper estimate of 0.23 for the fraction of directly produced pions is obtained based on experimental data on the resonance yields in high-energy hadron interactions. It is shown that experimental data on like-pion correlations agree with a dominant contribution of the pions from the decays of light resonances. In particular, the observed value of the parameter characterizing the suppression of the interference effect, the decrease of the slope of the correlation function with increase in the relative momentumQ of the like pions in their c.m.s. and the dependence of the time parameter on the pion velocity are explained. It is shown that the slope of the correlation function for the like-pion pairs containing the decay pions atQ>0.1 GeV/c is mainly determined by the size of the resonance production region, which allows one to determine the size of the production region of direct particles (pions and resonances) despite the very low fraction of the pairs of directly produced pions. The fraction of directly produced pions, 0.17±0.09 (stat.)±0.08 (syst.), and the radius of the direct production region, 0.55±0.08 (stat.)±0.10 (syst.) fm, have been determined based on the analysis of the most accurate correlation function measured inpp- and -interaction on ISR at 63 GeV.     

Navier and stokes meet the wavelet

We work in the space = of divergence-free measurable vector fields onR ³ complete in the norm , where     

Fast-hadron formation mechanism in leptoproduction in nuclei

The mechanism of fast-hadron leptoproduction in nuclei in deep inelastic region is considered. Different possible mechansims of fast-hadron formation in the virtual-photon fragmentation region and the process of transition of the quark (quark-gluon system) through nuclear matter is analysed. The range of consistency of the SLAC and EMC CERN data on meson leptoproduction in different nuclei is obtained to be 0.2 GeV²m _c ² 0.5 GeV². It is shown that the kinematic region 0.05x _B 0.3 and (3–5)Q ²/m _c ² 100 is the most favourable for an investigation of the growth law (evolution) of the transverse dimensions of quark (quark-gluon system) produced by the virtual photon.     

From the deuteron to deusons,an analysis of deuteronlike meson-meson bound states

A systematic study of possible deuteronlike twomeson bound states,deusons, is presented. Previous arguments that many such bound states may exist are elaborated with detailed arguments and numerical calculations including, in particular, the tensor potential. This tensor potential which is crucial for the deuteron binding is shown to be very important also in the mesonic case. Especially, in the pseudoscalar³ P ₀ pseudoscalar-vector and vector-vector channels the important observation is made that the centrifugal barrier from theP-wave can be overcome by the 1/r ² and 1/r ³ terms of the tensor potential. In the heavy meson sector one-pion exchange alone is strong enough to form at least deuteronlike and composites bound by approximately 50 MeV. Composites of and states bound by pion exchange alone are expected near the thresholds, while in the light meson sector one generally needs some additional short range attraction to form bound states. The quantum numbers of these states areI=0, andJ ^PC=0^–+, 1⁺⁺ for the states andI=0,J ^PC=0⁺⁺, O^–+, 1^+– and 2⁺⁺ for the composites. In the states: ^b (10545), _b1(10562) are predicted and in , one finds the states: ^b (10590), _bQ (10582),h _b(10608), _b2(10602). Near the threshold the states: ^c (3870), _c0(3870) are predicted, and near the threshold one finds the states: _b0(4015), ^c (4015),h _c(4015), _c2(4015). Within the light meson sector pion exchange gives strong attraction for and systems with quantum numbers where the best non- candidates exist, although pion exchange alone is not strong enough to support such bound states. Thus, although one cannot conclude with certainty it to be the case, this fact does favour the picture that the (1440) and thef ₁ (1420) are mainly composites and thef ₀(1710) mainly a bound state, while thef ₀(1515) andf ₂(1520) could be predominantly composites. If the predicted and states are found, these would support this interpretation of the light states. In channels with exotic flavour orCP quantum numbers pion exchange is generally repulsive or quite weak. Therefore one does not expect that such deuteronlike bound states exist, althoughB*B* may be an exception.     

Upper limit for thermal direct photon production in heavy-ion collisions at 60 and 200A·GeV

The production of direct photons has been investigated in reactions ofp and¹⁶O projectiles at 60 and 200A·GeV with C and Au nuclei. Photon and ⁰ spectra have been measured in the pseudorapidity range 1.52.1 for the transverse momentum region 0.4 GeV/cp _T 2.8 GeV/c employing the lead-glass spectrometer SAPHIR. An upper limit of 15% at the 90% confidence level for the direct photon signal relative to the neutral pion production is obtained from the comparison of measured photon spectra with Monte Carlo simulations of the hadronic background based on the reconstructed yield of ⁰ and mesons. Consequences for a possible phase transition to a quark-gluon plasma are discussed.     

Decay of the new isotope127Pr

A new isotope,¹²⁷Pr, has been identified and its decay has been studied using on-line isotope separation of⁹⁴Mo (³⁶Ar,p2n) reaction products. The half-life of the isotope was determined to be 7.7(6) s, and a /X-ray spectrum has been obtained. A partial level scheme is proposed for¹²⁷Ce on the basis of-singles,-gated and-coincidence data.The authors would like to thank the TIARA cyclotron crew for their cooperation in generating an intense³⁶Ar beam as well as in operating the cyclotron. This work was partly supported by the JAERI-University Collaborative Research Project.