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.     

Subthreshold antiproton andK − production in heavy ion collisions

Subthreshold ¯p andK ^– and energetic ^– production was studied in Ne + NaF, Cu, Sn and Bi, and in Ni + Ni collisions with incident energies between 1.6 and 2 GeV/u. The measured cross sections indicate a dominant contribution of baryonic resonances. This is also consistent with a generalized scaling behaviour of the cross sections with the energy available in the collision and the energy necessary to produce particles as observed with Ne induced reactions. Deviations from scaling especially pronounced in the Ni-Ni system will be discussed in terms of absorption effects. The flat slope of the excitation function for ¯p production can be related to a reduced production threshold caused by a reduction of the antiproton mass in the dense and heated medium by about 100—150 MeV/c². A similar in-medium mass reduction is also indicated forK ^– mesons. An increased ¯p reabsorption probability for the heavier systems is concluded from the comparison of the ¯p yields in Ne + NaF, Ne + Sn and Ni + Ni collisions.Dedicated to Professor Klaus Dietrich on the occasion of his 60th birthday.     

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     

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     

Results from the UA 2 experiment at the CERN p¯p Collider

This paper presents results on the production and decay properties of the Intermediate Vector Bosons (IVB)W and Z⁰ and on the search of the top quark in the upgraded UA 2 detector at the CERNp¯p Collider. The analysed data have been taken in the 1988 and 1989 Collider running periods at the centre of mass energy of 630 GeV, and correspond to an integrated luminosity of 7·4 pb^–1.     

A possible way to promote antihydrogen formation via metastable antiprotonic helium atoms

A new way to promote antihydrogen formation via the recently discovered long-lived metastable states of antiprotonic helium atoms is discussed. Recombination processes such ase ^– ¯pHe⁺⁺ +e ⁺ e ^– e ⁺ ¯p + He⁰ are possible in this respect.Dedicated to Prof. Dr. P. Kienle on the occasion of his 60th birthday     

The\bar pp \to e^ + e^ - reaction at rest and the hierarchy of the annihilation ranges

A new procedure is devised to evaluate the proton form-factor at the ¯pp threshold from experimental data on ¯ppe ⁺ e ^– annihilation at rest. Comparison of the ¯ppe ⁺ e ^– and¯pp ^+– processes reveals that annihilation ranges for various channels are ranked in line with quark dynamics.This work has been funded in part by the German Federal Minister for Research and Technology (BMFT) under the contract number 06HD756     

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     

Measurement of the electric form factor of the neutron at Q2 = 0.3-0.8 (GeV/ c) 2 ⋆

The electric form factor of the neutron, G_E,n, has been measured at the Mainz Microtron by recoil polarimetry in the quasielastic D(¯e, e¯n)p reaction. Three data points have been extracted at squared four-momentum transfers Q ² = 0.3, 0.6 and 0.8 (GeV/c)². Corrections for nuclear binding effects have been applied.This revised version was published online in March 2005. In the previous version, the email address of one author was inadvertently assigned to multiple authors.     

A possible assignment for the ground scalar meson nonet

Based on the main assumption that a₀(980) and D ^* _sJ(2317) belong to the 1³P₀ q¯ multiplet, in the framework of Regge phenomenology and meson-meson mixing, it is suggested that a₀(980), K ^* ₀(1052), f₀(1099) and f₀(530) constitute the ground scalar meson nonet, and that the f₀(1099) is composed mostly of s¯, while the f₀(530) is mainly a u¯ + d¯ system. It is supposed that these states would likely correspond to the observed scalar states a₀(980), κ(900), f₀(980) and f₀(600)/σ, respectively. The agreement between the present findings and those given by other different approaches is satisfactory.     

Photoproduction of π 0 ω off protons for E γ ≤3 GeV

Differential and total cross-sections for photoproduction of γp→pπ ⁰ ω and γp→Δ ⁺ ω were determined from measurements of the CB-ELSA experiment, performed at the electron accelerator ELSA in Bonn. The measurements covered the photon energy range from the production threshold up to 3GeV.     

Regularization of singular terms in the N¯ potential model

We suggest a method of singular terms regularization in a potential model of the N¯ interaction. This method is free from uncertainties related to the usual cut-off procedure and is based on the fact that, in the presence of sufficiently strong short-range annihilation, N and ¯ never approach close enough to each other. In such a case the low-energy scattering is shown to be fully determined by the OBEP tail, while any details of the short-range core of the N¯ interaction are excluded from the observables. The obtained results for S- and P-wave scattering lengths are in agreement with the well-established theoretical models.     

On the physical interpretation and the mathematical structure of the combinatorial hierarchy

The combinatorial hierarchy model for basic particle processes is based on elementary entities; any representation they may have is discrete and two-valued. We call themSchnurs to suggest their most fundamental aspect as concatenating strings. Consider a definite small number of them. Consider an elementary creation act as a result of which two different Schnurs generate a new Schnur which is again different. We speak of this process as a discrimination. By this process and by this process alone can the complexity of the universe be explored. By concatenations of this process we create more complex entities which are themselves Schnurs at a new level of complexity. Everything plays a dual role in which something comes in from the outside to interact, and also serves as a synopsis or concatenation of such a process. We thus incorporate the observation metaphysic at the start, rejecting Bohr's reduction to the haptic language of common sense and classical physics. Since discriminations occur sequentially, our model is consistent with a fixed past-uncertain future philosophy of physics. We demonstrate that this model generates four hierarchical levels of rapidly increasing complexity. Concrete interpretation of the four levels of the hierarchy (with cardinals 3,7,127,2¹²⁷-110³⁸) associates the three levels which map up and down with the three absolute conservation laws (charge, baryon number, lepton number) and the spin dichotomy. The first level represents +, –, and ± unit charge. The second has the quantum numbers of a baryon-antibaryon pair and associated charged meson (e.g.,n¯n,p¯n,p¯p,n¯p, ⁺ , ⁰, ^– ). The third level associates this pair, now including four spin states as well as four charge states, with a neutral lepton-antilepton pair (e¯e orv¯v), each pair in four spin states (total, 64 states)—three charged spinless, three charged spin-1, and a neutral spin-1 mesons (15 states), and a neutral vector boson associated with the leptons; this gives 3+15+3×15=63 possible boson states, so a total correct count of 63+64=127 states. Something likeSU ₂×SU ₃ and other indications of quark quantum numbers can occur as substructures at the fourth (unstable) level. Breaking into the (Bose) hierarchy by structures with the quantum numbers of a fermion, if this is an electron, allows us to understand Parker-Rhodes' calculation ofm _p /m _e =1836.1515 in terms of our interpretation of the hierarchy. A slight extension gives us the usual static approximation to the binding energy of the hydrogen atom, ² m _e c ² . We also show that the cosmological implications of the theory are in accord with current experience. We conclude that we have made a promising beginning in the physical interpretation of a theory which could eventually encompass all branches of physics.Work supported by the Department of Energy under contract number EY-76-C-03-051.     

Transient field measurements on32S(21 +) ions in Gd at the 1s electron Bohr velocity

With the knowng-factor of the Coulomb excited first 2⁺-state in³²S the transient magnetic field was determined for sulphur ions traversing Gd at a mean velocity of 16 ₀ ( ₀=c/137). The degree of polarization deduced for the dominating H-like ions, ¯p_1s =0.10(3), agrees very well with that obtained at lower velocities. In addition, an upper limit of a transient electric field gradient was deduced from the particle--angular correlation which is expected on theoretical grounds.The authors thank the operating staff and in particular Dr. R. Repnow of the accelerator facility at the Max-Planck-Institut für Kernphysik in Heidelberg for providing excellent beam conditions. They are indebted to Profs. D. Habs and U. Schmidt-Rohr for their continuous interest and generous support during the experiment. They are grateful to Dr. P. Maier-Komor and Mrs. A. Meens for preparing the Gd-targets and He-implantation. Support by the BMFT and the Deutsche Forschungsgemeinschaft is acknowledged.     

A metric topology for causally continuous completions

A metric topologyH(¯M) is introduced on the causal completion¯M of a causally continuous space-timeM. This metric topology is at least as coarse as the extended Alexandrov topologyA(¯M) on¯M. In bothH(¯M) andA(¯M), the original space-timeM is an open and dense subset. From the definition ofH(¯M), it follows that the causality on¯M is continuous at boundary points. IfM admits a compact Cauchy surface, thenH(¯M) andA(¯M) are the same.     

Nucleon electromagnetic form factors and polarization observables in space-like and time-like regions

We perform a global analysis of the experimental data of the electromagnetic nucleon form factors, in space-like and time-like regions. We give the expressions of the observables in annihilation processes, such as p + ¯↦ℓ⁺ + ℓ^-, ℓ = e or μ, in terms of form factors. We discuss some of the phenomenological models proposed in the literature for the space-like region, and consider their analytical continuation to the time-like region. After determining the parameters through a fit on the available data, we give predictions for the observables which will be experimentally accessible with large statistics, polarized annihilation reactions     

Comparative Regge analysis of Λ,ΣΛ(1520) and Θ<Superscript>+</Superscript> production in γp,πp and pp reactions

Using the Quark-Gluon Strings Model --combined with Regge phenomenology-- we perform a comparative analysis of Λ, Σ⁰, Λ(1520) and Θ⁺ production in binary reactions induced by photon, pion and proton beams on the nucleon. We find that the existing experimental data on the γp↦K⁺Λ differential and total cross-sections can be described very well by the model for photon energies 1-16 GeV and - t < 2 GeV² assuming a dominant contribution of the K^* Regge trajectory. Moreover, using the same parameters we also reproduce the total γp↦K⁺Σ⁰ and γp↦K⁺Λ(1520) cross-sections suggesting a “universality” of the Regge model. In order to check the consistency of the approach we evaluate the differential and total cross-sections for the reaction π^-p↦K⁰Λ which is also found to be dominated by the K^* Regge trajectory. Using the apparent “universality” of the Regge model we extend our scheme to the analysis of the binary reactions γp↦¯⁰Θ⁺, π^-p↦K^-Θ⁺ and pp↦Σ⁺Θ⁺ as well as the exclusive and inclusive Θ⁺ production in the reactions pp↦p¯⁰Θ⁺ and pp↦Θ⁺X. Our detailed studies demonstrate that Θ⁺ production does not follow the “universality” principle, thus suggesting an essentially different internal structure of the exotic baryon relative to conventional hyperons or hyperon resonances.     

Physical meaning of the phase of high energy elastic scattering amplitude

The influence of the phaset-dependence on the profiles of high energy elastic hadron scattering in the impact-parameter plane are discussed. The analysis of interference experimental data concerning pp, ¯pp and p⁴He scattering is summarized. It is shown that in all these cases the high-energy elastic scattering can be interpreted as a peripheral process.Dedicated to Academician Václav Votruba on the occasion of his eightieth birthday.