${}^{86}\mathrm{Nb}$ was produced using the ${}^{58}\mathrm{Ni}{(}^{32}\mathrm{S},3pn)$ reaction at 130 MeV. $\gamma$-ray linear polarizations were measured with a four-crystal “clover” Compton polarimeter. Results from this and an angular distribution measurement have led to spin-parity assignments for the $6^{-},$ $7^{+}$, and $8^{+}$ low-lying states.

The ${}^{180}{\mathrm{Ta}}^m(\gamma ,{\gamma }^{\prime }{)}^{180}\mathrm{Ta}$ reaction that was investigated by LINAC produced 4 MeV endpoint energy bremsstrahlung. The decay signatures of ${}^{180}\mathrm{Ta}$ were detected, with an effective cross section of $32\pm 11\mu \mathrm{b};$ $300\pm 110\mu \mathrm{b}\mathrm{}\mathrm{MeV}$ was found for the reaction cross section integrated up to 4 MeV. The results obtained provide independent confirmation of previously disputed results in the literature.

We have remeasured the decay of ${}^{31}\mathrm{Ar}$ with a setup sensitive to multiparticle decay branches and obtained a new limit of $1.1\times {10}^{-3}$ (99% C.L.) on the β-delayed three-proton branch between the isobaric analog state in ${}^{31}\mathrm{Cl}$ and the ground state of ${}^{28}\mathrm{Si}$. This a factor of 17 below the previously reported first observation of β-delayed three-proton emission $\mathrm{in}{\hspace{0.5em}}^{31}\mathrm{Ar}$. The limit on a possible $\beta 3p$ branch to the first excited state in ${}^{28}\mathrm{Si}$ is $2.9\times {10}^{-4}$.

The electromagnetic form factor of the pion is calculated in a pseudoscalar field theoretical model with constituent quarks. We extract the form factor using the “$+$” and “$-$” components of the electromagnetic current on the light front. For comparison, we also compute the form factor in the covariant framework. It is shown that the pair terms do not contribute to the “$+$” component of the electromagnetic current; however, they affect the “$-$” component of the electromagnetic current.

A method is presented for determining the density of points in a multidimensional space based on a search for the nearest points to preselected test values. The primary interest in such a procedure lies in comparing sets of event files (such as those which typically arise in modern nuclear and particle physics experiments) with theoretically generated sets or with each other.

This paper reports analysis of the scaled factorial moments in two-dimensional rapidity-azimuth phase space using data of ${}^{16}\mathrm{O}-\mathrm{A}\mathrm{g}\mathrm{B}\mathrm{r}$ interactions at 60 GeV/nucleon to study the nature of the hidden phase transition in multiparticle production. The analysis indicates the occurrence of a phase transition of nonthermal nature.

Hadronic structure functions are modeled as a distribution of solutions to the classical string model of Nambu and Gotō. In the model, the endpoints of the strings, identified as quarks, carry a finite amount of energy and momentum. The endpoint trajectories are assumed to be polygons and it is shown that the structure function in the scaling limit is directly related to the distribution of lengths of the straight line segments making up the polygons. The relationship is inverted to give an analytic expression for the distribution of straight line segments in terms of the structure function. The results are applied to the measured proton and pion structure functions.

Physics beyond the standard model of electroweak interactions that violates lepton number will, in general, induce operators involving the quark and lepton fields that violate lepton number. I point out that some matrix elements of particular operators are known. In the limit of exact SU(3) flavor symmetry the operator $ū{\gamma }_{\mu }\left(1\mathrm{}-{\gamma }_5\right)dū{\gamma }_{\mu }\left(1\mathrm{}-{\gamma }_5\right)d$ is part of the $27$ representation responsible for $\Delta I=\frac{3}{2}$ strangeness changing decays in the standard model. At leading order in the chiral expansion there is only one coupling constant that describes the weak interactions of the pseudo-Goldstone bosons induced by the $27$ representation. The observed branching fraction for $K^{+}\to {\pi }^{+}{\pi }^0$ determines this coupling constant. Contributions of the form $m_s\ln m_s$ are used to estimate SU(3) breaking corrections to the relation between $K^{+}\to {\pi }^{+}{\pi }^0$ and the ${\pi }^{-}\to {\pi }^{+}{e}^{-}{e}^{-}$ interaction.

A treatment of heavy ion charge exchange reactions based on the Glauber approximation is presented. It is applied to the analysis of the reactions ${}^{12}\mathrm{C}{(}^{13}\mathrm{C}{,}^{13}\mathrm{N}{)}^{12}\mathrm{B},$ ${}^{12}\mathrm{C}{(}^{13}\mathrm{C}{,}^{13}\mathrm{B}{)}^{12}\mathrm{N}$, and ${}^{12}\mathrm{C}{(}^{12}\mathrm{C}{,}^{12}\mathrm{N}{)}^{12}\mathrm{B}$ at intermediate energies. Overall agreement is found on the basis of a model whose ingredients are the experimental nucleon-nucleon scattering amplitudes, the phenomenological nuclear densities, and the transition densities derived from microscopic nuclear structure models.

This paper describes the derivation of a new representation of an $\mathrm{SU}{\mathrm{}\left(2\right)\mathrm{}}_L\times \mathrm{SU}{\mathrm{}\left(2\right)\mathrm{}}_R$ locally invariant model of the strong interactions called quantum hadrodynamics 3 (QHD-III). QHD-III is a gauge-invariant theory based on the linear $\sigma$ model, the gauge bosons being the $\mathbf{\rho }$ and the ${\mathit{a}}_1$. The new representation considerably simplifies the Lagrangian. To derive the new representation, the gauge invariance of the model is exploited. The role of the gauge boson masses in gauge-invariant models of the strong interactions based on the $\sigma$ model is also discussed, and it is shown that these masses are necessary if the pion is to survive as a physical field.

We investigate the post-acceleration of the ${}^{10}\mathrm{Be}$ fragment in the Coulomb breakup reaction of the halo nucleus ${}^{11}\mathrm{Be}$, assuming that the excitation of the projectile is to states in the low-energy continuum. The method used retains all finite-range effects associated with the interactions between the breakup fragments and can use realistic wave functions for the halo nuclei. We apply the method to compute the average momenta of the ${}^{10}\mathrm{Be}$ fragment at four different scattering angles following breakup of ${}^{11}\mathrm{Be}$ on a Au target at 42 MeV/nucleon beam energy. Our results, which are in qualitative agreement with recent precision experimental data, are consistent with the picture of no post-acceleration effect. The implication is that the breakup takes place on a time-scale long compared to the collision time.

Optical limit Glauber theory calculations of reaction cross sections, used to deduce nuclear sizes from high energy data, are studied in the case of a deformed projectile (or target). We show that a previously applied formula, used to adjust the root-mean-squared radius deduced assuming spherical projectiles, is consistent with results which treat the projectile deformation explicitly within the reaction calculation. The correct interpretation of this formula in studies of reaction cross sections is clarified.

The parameters of the short range part of the Paris $N\overline{N}$ potential are readjusted by fitting to a new set of data which includes the recent measurements on the charge exchange $p\overline{p}\to n\mathrm{n̄}$  reaction. Significant improvements in the fit are obtained.

We argue that an analysis which does not include exchange terms cannot usefully discriminate between $\mathrm{NN}$ interactions by means of fitting $N\alpha$ data.

We present results of a search for neutral strange quark matter (strangelets) in $11.6A\mathrm{GeV}/c\mathrm{A}\mathrm{u}+\mathrm{P}\mathrm{b}$ reactions from the 1995 run of experiment E864 at the Brookhaven Alternating Gradient Synchrotron. We have sampled approximately 1.3 billion 10% most central $\mathrm{A}\mathrm{u}+\mathrm{P}\mathrm{b}$ interactions and have observed no statistically significant signal for neutral strangelet states with baryon number in the range $6<A<\mathrm{}100.\mathrm{}$ We set upper limits on the production of these exotic states at the level of $8\times {10}^{-8}$ per central collision for mass $>20\mathrm{}\mathrm{GeV}{/c}^2.$ These limits are the first limits reported on the production of heavy neutral strangelets. They complement searches for positively and negatively charged strangelets also conducted by our collaboration. We discuss the implications of these results on strangelet production mechanisms and the stability of strange quark matter.

Excited states in the proton-unbound nucleus ${}^{109}\mathrm{I}$ were populated using the ${}^{54}\mathrm{Fe}{(}^{58}\mathrm{Ni},p2n)$ reaction at a beam energy of 220 MeV. Gamma rays in ${}^{109}\mathrm{I}$ were identified using the recoil-decay tagging technique. The analysis of proton-correlated $\gamma \gamma$ coincidence data produced the yrast decay sequence in ${}^{109}\mathrm{I}$, which can be tentatively assigned as built on the $h_{11/2}$ proton state based on systematic trends in the neighboring isotopes. This sequence is completely different from that reported previously. A comparison of the $h_{11/2}$ band $\mathrm{in}{\hspace{0.5em}}^{109}\mathrm{I}$ with those in heavier iodines shows that ${}^{109}\mathrm{I}$ continues the trend of decreasing quadrupole deformation with decreasing neutron number.

Recently many authors have performed shell-model calculations of nuclear matrix elements determining the rates of the ordinary muon capture in light nuclei. These calculations have employed well-tested effective interactions in large scale shell-model studies. For one of the nuclei of interest, namely, ${}^{28}\mathrm{Si},$ there exists recent experimental data which can be used to deduce the value of the ratio $C_P{/C}_A$ by using the calculated matrix elements. Surprisingly enough, all the shell-model results suggest a very small value $\left(\simeq 0\right)$ for $C_P{/C}_A,$ quite far from the PCAC prediction and recent data on muon capture in hydrogen. We show that this rather disturbing anomaly is solved by employing effective transition operators. This finding is also very important for realistic muon-capture calculations where one explores the strength of the scalar coupling in the weak charged current of leptons and hadrons.

We propose to study the impact parameter dependence of the $\overline{\Lambda }/\overline{p}$ ratio in $\mathrm{Pb}\left(160A\hspace{0.5em}\mathrm{GeV}\right)+\mathrm{Pb}$ reactions. The $\overline{\Lambda }/\overline{p}$ ratio is a sensible tool to distinguish between hadronic cascade models and hydrodynamical models, which assume chemical equilibrium and incorporate a possible phase transition to a quark-gluon plasma.

The structure of low-lying states of ${}^{56}\mathrm{Ni}$ is studied by the Monte Carlo shell model based on the quantum Monte Carlo diagonalization method. The coexistence of spherical yrast, prolate deformed, and other non-yrast states is described by the full $\mathrm{pf}$-shell calculations, by employing the FPD6 realistic residual interaction. To understand the properties of eigenstates thus obtained, we utilize a mean field analysis, such as a potential energy surface by constrained Hartree-Fock method.

From a sum rule approach, it is shown that the excitation energy as well as the $M1\mathrm{}$ transition strength of the low-lying scissors mode in heavy even-even nuclei are well reproduced by using the moments of inertia and g factors of the ground state band. Also, a simple correspondence to the high-lying scissors mode is deduced.