Commissioning of the 4 $$\pi \,\gamma $$ -summing array HECTOR at CASPAR: measurements of $$^{27}\text {Al}$$ $$(p,\gamma )$$ $$^{28}\text {Si}$$ resonances 4850 feet underground

The European Physical Journal A - Neutron star matter spans a wide range of densities, from that of nuclei at the surface to exceeding several times normal nuclear matter density in the core. While...     

γ5-Invarianz und starke Wechselwirkungen

In a previous letter⁶ a generalizedγ ₅-invariance for strong interactions has been proposed and some consequences of this invariance have been outlined. The present paper contains the detailed proof and discussion of these consequences. For the baryon-pion interactions one obtains two possible forms for the coupling:

1. a)
   The coupling is determined by the total I-spin vector current and contains no directΛ∑π-coupling. This interaction turns out to be strictly parity conserving even in the presence of electromagnetic and I-spin invariantK-meson couplings.     

Local current commutators

The predictive power of current algebra relations is discussed using models for the spectral functions of current commutator matrix elements. The functions constructed fulfill the requirements of covariance, locality and spectrum conditions. Thus, the current algebra constraints can easily be imposed. In these models the formfactors are described by superpositions of poles. For simplicity only spin zero states are taken into account.     

Nonlocal anomaly of the axial-vector current for bound states

We argue that the amplitude does not vanish in the limit of zero quark masses. This represents a new kind of violation of the classical equation of motion for the axial current and should be interpreted as the axial anomaly for bound states. The anomaly emerges in spite of the fact that the one loop integrals are ultraviolet finite as guaranteed by the finite size of bound-state wave functions. As a result, the amplitude behaves like approximately 1/p(2) in the limit of a large momentum p of the current. The observed effect requires the modification of the classical equation of motion of the axial-vector current by nonlocal operators.     

The surprising nonleptonic decays

Recent experiments onD-meson decays necessitate a revision of the standard theoretical model for weak decays. In this paper we argue that the presence of gluons in hadrons as required by local color gauge-invariance of Quantum Chromodynamics vitiates, in particular, two assumptions previously made:

1. color suppression factors in amplitudes for weak decays like \(D^0 \to \bar K^0 \pi ^0 \) ,
2. helicity suppression of two-quark interactions in weak decays.

A formula for estimating inclusive rates of mesons decaying via two-quark interactions is derived. Estimates for decay rates and branching ratios of several interesting decays of charmed hadrons are given. In particular, we obtain lifetime estimates forD ⁰,D ⁺, andF ⁺, and we predict the branching ratio for Cabibbo-suppressed decays ofD ⁺ to be of order 0.3 rather than of order tan²Θ _c as expected within the conventional model for weak decays.B-meson decays, which would provide an additional test of our scheme, are briefly discussed. Furthermore we point out that our approach sheds new light on the old problem of strongly enhanced |ΔI|=1/2 amplitudes in nonleptonic decays of strange particles.     

Epsilon-ritz method for solving optimal control problems: Useful parallel solution method

Using Balakrishnan's epsilon problem formulation (Ref. 1) and the Rayleigh-Ritz method with an orthogonal polynomial function basis, optimal control problems are transformed from the standard two-point boundary-value problem to a nonlinear programming problem. The resulting matrix-vector equations describing the optimal solution have standard parallel solution methods for implementation on parallel processor arrays. The method is modified to handle inequality constraints, and some results are presented under which specialized nonlinear functions, such as sines and cosines, can be handled directly. Some computational results performed on an Intel Sugarcube are presented to illustrate that considerable computational savings can be realized by using the proposed solution method.     

A form factor model for exclusive B- and D-decays

An explicit model is presented which gives the momentum transfer-dependent ratios of form factors of hadronic currents. For the unknown Isgur-Wise function and its generalization for transitions to light particles a simple phenomenological Ansatz is added. The model allows a calculation of all form factors in terms of mass parameters only. It is tested by comparison with experimental data, QCD sum rules and lattice calculations.