Isotope dependence of deeply bound pionic states in Sn and Pb

Abstract

We have studied the isotope dependence of deeply bound pionic states in Sn and Pb in order to examine the possibility of obtaining important information on neutron density distribution and the modification of the pion decay constant f in a nuclear medium. Formation cross sections of the pionic states are calculated in the (d, 3 He) reactions. The present results indicate that the isotope dependence of the pionic states can be deduced from the experimental data with accessible energy resolution. The effects of the neutron skin for the formation cross sections are also examined and are found to affect the (d, 3 He) spectra significantly.

Precision Spectroscopy of Pionic1sStates of Sn Nuclei and Evidence for Partial Restoration of Chiral Symmetry in the Nuclear Medium

“…1 one distinct peak at around 365 MeV was observed, which was assigned to a dominant configuration of (1s) π (3s) −1 n . The overall spectrum shapes for the three Sn targets were found to be in good agreement with the predicted ones [25]. The spectra were decomposed according to the theoretical prescription of Ref.…”

“…One of the advantages of using Sn isotopes is that we can produce the 1s π − states as the most dominant quasisubstitutional states, (1s) π − (3s) −1 n , because of the presence of the 3s orbital near the Fermi surface, as theoretically predicted [25]. Another merit is to make use of isotopes over a wide range of (N − Z)/A to test the isospin dependence [10].…”

“…Such states were predicted to be produced as discrete states by nuclear reactions [21,22,23,24,25] and to provide unique information on the s-wave interaction, whereas in most pionic atoms the repulsive s-wave interaction is nearly counterbalanced by the attractive p-wave interaction (see, for instance, Batty et al [26]). In recent papers we showed that the density-dependent parameter b * 1 (ρ) can be well represented by a constant parameter b 1 [27], and developed a method to deduce the b 1 parameter [28].…”

“…The spectra were decomposed according to the theoretical prescription of Ref. [25], from which we could precisely determine the 1s binding energies (B 1s ) and widths (Γ 1s ). The results are summarized in Table I and in Fig.…”

Formation of Deeply Bound Pionic Atoms in Sn Isotopes

“…The (d, 3 He) spectra have been obtained in near recoilless kinematics to observe the peaks of the pionic state formation with a neutron hole in the quasi-substitutional configurations [2][3][4]. The Pb and Sn isotopes were used as the target nuclei in the experiments [2][3][4] since the spectra were expected to show the peak structures owing to one dominant [π ⊗ n −1 ] configuration based on the theoretical evaluations [5,6]. The simple structure of the observed peak is important and effective to deduce the pion binding energies precisely from the observed spectra.…”