arXiv subjects

H. P. Morsch

Publications and source records attributed to H. P. Morsch.

23 records · Page 2Linked to original sources

arXiv2007

Comparison of Isoscalar Vector Meson Production Cross Sections in Proton-Proton Collisions

The reaction $ pp\to pp\bf ω$ was investigated with the TOF spectrometer, which is an external experiment at the accelerator COSY (Forschungszentrum Jülich, Germany). Total as well as differential cross sections were determined at an excess energy of $93 MeV$ ($p_{beam}=2950 MeV/c$). Using the total cross section of $(9.0\pm 0.7 \pm1.1) μb$ for the reaction $ pp\to ppω$ determined here and existing data for the reaction $pp\to pp\bf ϕ$, the ratio $\mathcal{R}_{ϕ/ω}=σ_ϕ/σ_ω$ turns out to be significantly larger than expected by the Okubo-Zweig-Iizuka (OZI) rule. The uncertainty of this ratio is considerably smaller than in previous determinations. The differential distributions show that the $ω$ production is still dominated by S-wave production at this excess energy, however higher partial waves clearly contribute. A comparison of the measured angular distributions for $ω$ production to published distributions for $ϕ$ production at $83 MeV$ shows that the data are consistent with an identical production mechanism for both vector mesons.

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arXiv2006

Single-Pion Production in pp Collisions at =.95 GeV/c (I)

The single-pion production reactions $pp\to dπ^+$, $pp\to npπ^+$ and $pp\to ppπ^0$ were measured at a beam momentum of 0.95 GeV/c ($T_p \approx$ 400 MeV) using the short version of the COSY-TOF spectrometer. The implementation of a central calorimeter provided particle identification, energy determination and neutron detection in addition to time-of-flight and angle measurements. Thus all pion production channels were recorded with 1-4 overconstraints. The total and differential cross sections obtained are compared to previous data and theoretical calculations. Main emphasis is put on the discussion of the $ppπ^0$ channel, where we obtain angular distributions different from previous experimental results, however, partly in good agreement with recent phenomenological and theoretical predictions. In particular we observe very large anisotropies for the $π^0$ angular distributions in the kinematical region of small relative proton momenta revealing there a dominance of proton spinflip transitions associated with $π^0$ $s$- and $d$-partial waves and emphasizing the important role of $π^0$ d-waves.

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arXiv2005

Structure for the breathing mode of the nucleon from high energy p-p scattering

Spectra of p-p and pi-p scattering at beam momenta between 6 and 30 GeV/c have been reanalysed. These show strong excitation of N* resonances, the strongest one corresponding to the "scalar" P11 excitation (breathing mode) at m_o= 1400+-10 MeV with Gamma= 200+-25 MeV. The result of a strong scalar excitation is supported by a large longitudinal amplitude S_1/2 extracted from e-p scattering. From exclusive data on p+p=>p p pi+ pi- a large 2pi-N decay branch for the P_11 resonance of B_2pi= 75+-20 % has been extracted. The differential cross sections were described in a double folding approach, assuming multi-gluon exchange as the dominant part of the effective interaction between the constituents of projectile and target. First, the parameters of the interaction were fitted to elastic scattering; then with this interaction the inelastic cross sections were described in the distorted wave Born approximation. A good description of the data requires a surface peaked transition density, quite different from that of a pure radial mode. In contrast, the electron scattering amplitude S_1/2 is quite well described by a breathing mode transition density with radial node. This large difference between charge and matter transition density suggests, that in p-p scattering the coupling to the multi-gluon field is much more important than the coupling to the valence quarks. A multi-gluon (or sea-quark) transition density is derived, which shows also breathing, indicating a rather complex multi-quark structure of N and N* including multi-glue (or q^2n qbar ^-2n) creation out of the g.s. vacuum.

hep-ex↗

arXiv2004

Evidence for a narrow resonance at 1530 MeV/c2 in the K0 p - system of the reaction pp --> Sigma+ K0 p from the COSY-TOF experiment

The hadronic reaction pp --> Sigma+ K0 p was measured exclusively at a beam momentum of 2.95 GeV/c using the TOF detector at the COSY storage ring. A narrow peak was observed in the invariant mass spectrum of the K0 p subsystem at 1530 +- 5 MeV/c2 with a significance of 4 - 6 standard deviations, depending on background assumptions. The upper limit of 18 +- 4 MeV/c2 (FWHM) for its width is given by the experimental resolution. The corresponding total cross section is estimated to be about 0.4 +- 0.1(stat) +- 0.1(syst) microbarn. Since a resonance in this subsystem must have strangeness S = + 1 we claim it to be the Theta+ state for which very recently evidence was found in various experiments.

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arXiv2003

Hadron Physics at COSY

The workshop 'Hadron Physics at COSY' held from July 7th to July 10th 2003 in Bad Honnef brought together experimentalists and theoreticians from various fields of hadron physics to identify the key physics questions, which can be addressed with (un-) polarized proton and deuteron induced reactions at COSY. Topics discussed include charge symmetry breaking, elastic and inelastic nucleon-nucleon and nucleon-deuteron interactions, hadrons in the medium, mesonic bound states, meson and baryon resonances, and the hyperon-nucleon system. In addition prospects of the planned GSI facility were discussed. These Miniproceedings contain besides short summaries of the presentations the most relevant references for the field.

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