abstract

Introducing a fifth quark f with electric charge \(Q = 2/3\), and assuming  that the particle classification follows the \(C\)–\(C^{\prime }\) model mentioned by Achiman, Kollar and Walsh, we have derived the magnetic moments of all baryons under U(5)-symmetry. The normal and charmed particles have the same magnetic moments expressed in terms of at most three arbitrary constants, as those obtained in U(4)-symmetry. We predict the moments of new baryons, which turn out to be inevitable if \(Y\)-spectroscopy indicates the existence of a new quark. We have also evaluated magnetic moments of baryons for an alternative model with f-quark charge \(Q = - 1/3\) to accommodate the possible bias of the experimental results.

abstract

Two methods of determination of the reaction impact parameter, the one proposed by Webber and other by Henyey and Pumplin, are compared and discussed. It is shown that the lower limits of the impact parameter bL obtained by means of these methods are comparable and are always very low (\(\lesssim 0.5\) fm). On the example of the Henyey–Pumplin method it is argued that the experimentally obtained values \(b_{\rm L}\) may be very unreliable estimates of the reaction impact parameter and that any comparison of different reactions or reaction channels may be meaningless.

abstract

Constituent quarks with electromagnetic and strong-interaction form-factors behaving as \(1/\sqrt {Q^2}\) for \(Q^2 \to \infty \) are considered. One-gluon-exchange potential is used to calculate the hfs and fs of quarkonium q\(\overline {\rm q}\) built of such extended quarks. No confining potential is included in the calculations but its possible form, compatible with the picture of extended quarks, is suggested. The constituent quark gets then a strong-interaction radius \(r_0\) of large magnitude \(\gtrsim 1\) GeV\(^{-1}\) being in contrast with its small electromagnetic radius \(\lesssim 0.1\) GeV\(^{-1}\). So it behaves as a composite object with electric charge concentrated in the middle and colour broadly extended around (with a range comparable to actual hadron radii). Thus, if the structure of a constituent quark is dominated by the parton configuration consisting of one current quark and one current gluon, the gluon must be effectively lighter than the quark. The above picture emerges if the confining potential does not play any essential role in the lowest states in charmonium. It is true in fact for the suggested confining potential which switches on only for \(r \geq 2r_0\).

abstract

Some identities for on-shell \(S\)-matrices in consecutive scattering on two potentials are derived. As a straightforward consequence, the first order formula for the perturbed on-shell \(S\)-matrix is obtained. Finally, a new derivation of equations of variable phase method is proposed.

abstract

The binding energy of nuclear matter with an excess of neutrons, with spin-up neutrons and spin-up protons (characterized by the corresponding parameters \(\alpha _{\tau }=(N-Z)/A\), \(\alpha _{\rm n}=(N\hspace {-1mm}\uparrow - N\hspace {-1mm}\downarrow )/A\), and \(\alpha _{\rm p}=(Z\hspace {-1mm}\uparrow -Z\hspace {-1mm}\downarrow )/A)\) contains three symmetry energies: the isospin symmetry energy \(\varepsilon _{\tau }\), the spin symmetry energy \(\varepsilon _{\sigma }\) and the spin-isospin symmetry energy These energies are calculated using velocity-dependent effective potential of \(s\)-wave interaction, which was developed by Dzhibuti and Mamasakhlisov. The spin, isospin and spin-isospin dependent parts of the single-particle potential in nuclear matter are also calculated using the same effective nucleon–nucleon potentials. The spin-spin part of the optical model potential is estimated. The results are compared with those of Dąbrowski and Haensel, Krewald et al. and Khanna and Barhai.

abstract

Excited states of \(^{92}\)Mo were studied by in-beam \(\gamma \)-ray spectroscopy. The reaction (\(\alpha \), 2n) on \(^{90}\)Zr target was used to populate the excited states which were investigated by \(\gamma \)-single spectra, beam-\(\gamma \), \(\gamma \)–\(\gamma \) and beam-\(\gamma \)–\(\gamma \) coincidences. The excitation function and lifetimes were also measured. Several new \(\gamma \) lines belonging to the \(^{92}\)Mo and a few new levels were found. The results were compared with the level positions predicted by the nuclear shell-model.

abstract

The effective interaction energies were deduced from the experimental data for single neighbouring nuclei with \(N = 28\) and \(N = 50\). Odd–even effect, which was found, manifests itself by the dependence of the effective two-particle interaction energy on the number of particles which are filling the same orbit. The results were compared with the predictions obtained for \(\delta \)-function interaction with a varied value of spin exchange term. Comparison with the experiment is given.

abstract

We show that if the electromagnetic form-factor decreases fast enough, then the spectral function has at least one zero.

abstract

It is shown that the Cabibbo angle is associated not only with the pion and kaon masses but also with the D meson mass. The universality of the Cabibbo angle is further established.