Dieter Rein

Neutrino-Excitation of Baryon Resonances and Single Pion Production

Abstract This is an attempt to describe all existing data on neutrino production of single pions in the resonance region up to W = 2 GeV in terms of the relativistic quark model of Feynman, Kislinger and Ravndal (FKR). We considered single pion production to be mediated by all interfering resonances below 2 GeV. A simple noninterfering, nonresonant background of isospin 1 2 was added. It improved agreement with experiment, particularly in the ratio of isospin amplitudes in charged current reactions, at the expense of one additional constant. All total cross sections, cross section ratios and W-distributions are well reproduced at low and high energies, with charged and neutral currents (supposing the Salam-Weinberg theory with sin2 θ w ≈ 1 4 to be correct), and for neutrinos and antineutrinos, giving predictions where data are lacking. New predictions have been made for complex angular distributions in N π channels exhibiting strong interference between neighbouring resonances. These are sensitive (for 1.1 GeV ≲ W ≲ 1.5 GeV) to the sign of the Roper resonance P11(1450) which is controversial in photoproduction experiments.

Observation of neutrino and antineutrino induced coherent neutral pion production off Al27

Abstract The angular distribution of isolated π0,s, produced by νμ′s and ν μ′s in the Aachen-Padova spark chamber, shows a peak in the forward direction which is not explicable by resonance production. A similar effect is seen in the acoplanarity distribution of the decay photons, which shows an excess of nearly coplanar events. A control sample containing a recoil proton shows no such peaks and is well reproduced by a resonance model. The observed effects are consistent with neutral current (NC) induced coherent single π0 production off the entire Al27 nucleus. The coherent cross sections are σν=(29±10)×10−40 cm2/nucleus and σ ν =(25±7)×10 −40 cm 2 / nucleus . They determine the isovector axial NC coupling constant s=0.93±0.12. No η0 mesons were observed, which limits the corresponding isoscalar coupling constant to δ

CP violating partial rate asymmetries in the decays B±→ηπ±, η′π±, ηcπ±: a K-matrix analysis

Abstract We analyse the CP -violating asymmetries in the partial decay widths of B ± → π ± η and B ± → π ± η ′. The asymmetry is assumed to arise as a result of strong-interaction mixing of the channels π ± η ( η ′) with the channel π ± η c . The strength of the mixing is obtained using data on the decays η c → η ( η ′) ππ . Inelastic unitarity is implemented with the help of the K -matrix formalism. We predict large asymmetries, up to about 20%, with branching ratios of 10 −6 –10 −5 . Therefore, these decays provide the best place for testing in charged modes the hypothesis that CP noninvariance arises from a nonzero phase in the quark-mixing matrix.

Coherent production of photons by neutrinos

Abstract The reaction ν +N→ ν +N+ γ , involving the coherent emission of a photon in a neutrino-nucleus collision, can produce “single shower” events that simulate the reaction ν +e→ ν +e. The ratio of coherent photons to electrons (for an 27 Al target) is estimated to be 40% at E ν =20GeV and 10% at E ν =20 GeV. We examine the extent to which the “excess” of showers seen in the Aachen-Padova experiment could be understood by this mechanism.

Possibility of a locally, strongly increasing total cross section and related large real amplitude for\(\bar p\)(p)−p scattering up to 1000 TeV

AbstractUsing a new form for the diffractive amplitude, we show the possibility of a local increase above asymptotic behavior in the

Analysis of high-energy p(p)-p diffractive, elastic scattering and multiparticle production in terms of fluctuations in the eikonal

\bar p

New understanding of the diffractive scattering of hadrons at high energies; The blackening and increasing effective interaction area of the proton

(p)−p total cross section well up in the TeV range with values of about 180 mb reached at 100 TeV and 316 mb at 1000 TeV. Use of this locally, relatively strongly rising cross section in the dispersion relation leads to evaluation of the real to imaginary part ratio ϱ, for the forward scattering amplitude up into the TeV range. This quantity increases; we obtain ϱ=18% at 40 TeV. On the basis of a physical picture involving the growth of average multiplicities, it appears possible that asymptotic, bounded growth for the cross section may be reached only at collision energies in the vicinity of 1000 TeV. In this domain, certain global measures of partonic behavior come close to the behavior of the produced physical hadrons.

Elastic scattering and single diffractive dissociation inp(\(\bar p\))-p collisions up to 1000 TeV from a theory with fluctuations in the eikonal

Starting from a Dirac equation with a scalar linear confinement potential for quarks we calculate static properties ofS-wave baryons, such as magnetic moments, axial vector coupling constants and the proton charge radius. In addition we pursue the renormalization of weak decay constants originating from the influence of quark masses on the baryonic wave functions. The static baryon properties compare well with data andSU(3) symmetry breaking effects are found to be small in agreement with recent results on semileptonic hyperon decays.