Fast deuteron production from antiproton annihilation at rest on carbon and uranium targets

Deuteron yields from 20–350 MeV kinetic energy in antiproton annihilation at rest in¹²C and²³⁸U targets are compared with a coalescence model calculation. Agreement of the data with the model up to approximately 80 MeV is good. However, from 80 to 350 MeV the model increasingly underestimates the yield, by as much as on order of magnitude. These results, along with previously reported failures to explain proton spectra with first order rescattering of pions, suggest that other mechanisms are manifest in relatively rare, high energy light nucleus emission, e.g.B > 0 annihilations or possible six quark interactions.Work supported in part by the U.S. Air Force Office of Scientific Research and the National Science Foundation     

Protonium annihilation into two mesons

The available branching ratios for protonium annihilation into two mesons are analyzed in terms of a hadronic picture. We start from protonium wave functions calculated using a realistic OBE potential, a phenomenological part to account for the annihilation, and a particularly simple transition operatorV(N¯N meson _a + meson _b ). Flavour effects, sensitivity to tensor mixing and to isospin mixing are investigated.Work supported in part by German BMFT grant 06 OR 762, and by European Community project SC1-0233-C     

Prompt fission induced by antiproton annihilation at rest on heavy nuclei

Antiproton induced fission probabilities of U²³⁸, Bi²⁰⁹, Pb²⁰⁸ and Au¹⁷⁷ are reported together with the mass distribution of the fission fragments in the U²³⁸ and Bi²⁰⁹ cases. The charged particles multiplicities observed in co-incidence with fission have, also, been measured for U and Bi and are presented.Dedicated to Peter Armbruster on the occasion of his 60th birthday in recognition of his important contribution to modern Nuclear Physics     

Updating the effective range expansion of low-energyN \bar N-scattering

Low energyN¯N scattering is reanalyzed using the new data on annihilation cross-sections from CERN [1], the¯np-absorption measurement from BNL [2] and the annihilation width of the 2p state in antiprotonic hydrogen [3]. Imposing the condition that the imaginary part of the effective range is negative we find low energy scattering parameters which interpolate between the existing ITEP [4] and CERN/Heidelberg [5] values.Supported by the BMFT-grant 06 HD 756     

Vertex form factors of the rho-meson nucleon interaction at low momentum transfer

We calculated the one pion loop contributions to the form factors of the rho-nucleon interaction within a field theoretical model using effective Lagrangians. The results show that the tensor interaction is likely to be described well within such an approach. We obtain a magnetic coupling in the range of 3.5–7.1 atQ ²=0, depending on the choice of pion-nucleon form factor and a dipole form for theQ ² dependence tensor form factor with a scale of roughly 900 MeV for space-like momentum transfer. The results agree with the findings of the recent analysis of thep-N interaction and support a small scale parameter (0.5 GeV) for the pion-nucleon form factor.This work is supported by BMFT (06BO7027) and COSY-KFA Jülich (41140512)     

Dynamics of multipionp¯ p annihilation

We construct a dynamical model to study the pion correlations in the 5 annihilation ofp¯ p at rest. For the resonant channels, the simplest Lorentz-invariant couplings have been used. It is found that, in addition to the Bose-Einstein correlations caused by the finite size of the source, the dynamical correlations from the channels with intermediate resonances are important for explaining the experimental two-pion correlation function. The reliability of two standard methods for pion interferometry is tested in our model.On leave from Institute of Nuclear Research, Academia Sinica, P.O. Box 800204, Shanghai 201800, China     

The signal of Z ±(4430) in nucleon–antinucleon scattering

We study the production of Z ^±(4430) at a nucleon–antinucleon scattering experiment. Considering the PANDA experiment to be an ideal platform to explore the production of the charmonium and charmonim-like states, we suggest the forthcoming PANDA experiment to pay attention to the production of Z ^±(4430).     

N -N Annihilation intoKK from atomicS-states

We investigate the initial state interaction for the antiprotonic hydrogen (protonium) annihilation intoKK. We calculate thepp-n¯n mixing in the annihilation region and underline that the initial state interaction drastically changes the results of the isospin analysis of theN¯NK¯K amplitude.On leave of absence from ITEP, Moscow     

Correlations of two protons in relativisticdp-collisions

Two-proton correlations in thedpppn collisions of relativistic deuterons with protons are considered. These correlations give more information than inclusive proton spectra described in the framework of different deuteron structure function models because of uncertainty in the calculation of secondary interaction contribution (rescattering processes and final state interactions). We present the predictable calculations which show different behaviour of the correlation function for different deuteron structure function models in the kinematic region where contributions of secondary interactions are negligible.     

On the applicability of perturbative QCD to exclusive processes at currently available momentum transfer

We re-examine the problems connected with the end-point dominance in the calculation of exclusive processes in perturbative QCD. In a re-analysis we construct nucleon quark distribution amplitudes from the respective moments obtained from a QCD sum rule approach. These functions lead to acceptable values for the e.m. Dirac form factorsF ₁ ^p,n of the nucleon if effective gluon masses of ca. 300–600 MeV are included into the hard-scattering amplitude. In addition we also find a reasonable Q₂ — dependence of the proton form factor. The results point at the importance of the end-point k-dependence of distribution amplitude and hard-scattering amplitude in the calculation of exclusive processes.Work is supported by Deutsche Forschungsgemeinschaft (Ga 153-13-1) and partially by NATO (0581/87)     

Measurements of the antiproton-proton elastic cross section in the beam momentum range between 180 and 600 MeV/c

Thep¯ p cross sections at low energies are analysed in the framework of the optical model. It is shown that the annihilation range is closely related to the size of the proton as measured in electromagnetic and hadronic interactions. At larger distances thep¯ p interaction has the similar character as the NN one.     

QCD sum rules analysis of the rare B_{c}\rightarrow X\nu\bar{\nu} decays

Taking into account the gluon correction contributions to the correlation function, the form factors relevant to the rare decays are calculated in the framework of the three-point QCD sum rules, where X stands for axial vector particle, AV(D _s1), and vector particles, V(D ^*,D _s ^*). The total decay width as well as the branching ratio of these decays are evaluated using the q ² dependent expressions of the form factors. A comparison of our results with the predictions of the relativistic constituent quark model is presented.     

Effect of top quark spin on the unparticle couplings in $\gamma\gamma \to t\bar{t}$

We investigate the potential of γ γ collisions to probe scalar unparticle couplings via top–antitop quark pair production. We find 95% confidence level limits on the unparticle couplings with an integrated luminosity of 500 fb⁻¹ and an energy of  TeV. We investigate the effect of the top quark spin polarization on the unparticle couplings. It is shown that spin polarization of the top quark leads to a significant improvement in the sensitivity limits.     

Electromagnetic form factors of the nucleon in the few GeV region

The form factors of the nucleon are investigated in a framework in which nucleons are viewed as built up by quarks and diquarks, the latter being treated as quasie-lementary constituents. This model is a generalization of the hard scattering scheme for exclusive reactions applicable at moderately large momentum transfer. In contrast to the hard scattering scheme the diquark model provides non-zero helicity flip transitions of the nucleon. Therefore, we obtain predictions for both the magnetic and the electric form factor. The results are in good agreement with data.Sponsored in part by the Bundesministerium für Forschung und Technologie, FRG under contract number 06 Wü 765     

The influence of state dependent short range correlations on the depletion of the nuclear Fermi sea

The inlfuence of state dependent short range correlations on the occupation numbers of the single particle shell model orbits of the doubly closed shell nuclei¹⁶O and⁴⁰Ca is examined. The study shows that the effect of the state dependence of the short range correlations is rather small. The total depletion of the nuclear Fermi sea changes slightly compared with the one calculated by considering state independent short range correlations.     

Determination of antiproton-neutron amplitude from elastic¯p-deuteron scattering at 600 MeV/c

The elementary ¯p-neutron amplitude has been obtained from Glauber's model analysis of ¯p-d elastic scattering data at 600 MeV/c, taking into account theD-state component of the deuteron. The results are compared with the ¯p-nucleus analysis and the ¯NN potential model predictions.     

Comparison of Geant4 hadron generation with data from the interactions with beryllium nuclei of +8.9 GeV/c protons and pions and −8.0 GeV/c pions

Hadron generation in the Geant4 simulation tool kit is compared with inclusive spectra of secondary protons and pions from the interactions with beryllium nuclei of +8.9 GeV/c protons and pions, and of −8.0 GeV/c pions. The data were taken in 2002 at the CERN Proton Synchrotron with the HARP spectrometer. We report on significant disagreements between data and Monte Carlo simulation especially in the polar-angle distributions of secondary protons and pions. On leave of absence at Ecole Polytechnique Fédérale, Lausanne, Switzerland.     

Octet-baryon form factors in the diquark model

We present an alternative parameterization of the quark-diquark model of baryons which particularly takes care of the most recent proton electric form-factor data from the E136 experiment at SLAC. In addition to electromagnetic form factors of the nucleon, for which good agreement with data is achieved, we discuss the weak axial vector form factor of the nucleon as well as electromagnetic form factors of and hyperons. Technical advance in calculating the pertinent analytic expressions within perturbative quantum chromodynamics is gained by formulating the wave function of the quark-diquark system in a covariant way. Finally, we also comment on the influence of Sudakov corrections within the scope of the diquark model.Sponsored in part by the Bundesministerium für Forschung und Technologie, Germany, under contract number 06 Wu 737     

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.