In 1949, Yukawa was awarded Nobel Prize in Physics for the predicted the existence of meson as the carrier particle of strong nuclear force. In 1980’s with the development of high intensity proton accelerators at Los Alamos National Laboratory’s Meson Physics Facility (LAMPF), Swiss Institute of Nuclear Physics (SIN) and Canadian Particle Accelerator Center (TRIUMF) it became possible to study nuclear interactions with pion beams.
My 1st pion physics experiment performed in the summer of 1982 at the LAMPF Low Energy Pion beamline was my master thesis experiment, “Isospin effect in π+/- 14C elastic scattering at 50 MeV”. This was my 1st exposure to an international experiment at a premier nuclear physics laboratory of the world in 1980s.
Abstract: Angular distributions have been measured for π± elastic scattering at 50 MeV from 14C. Comparison with previously measured distributions for 12C shows a significant isotopic difference for π− scattering. The data were analyzed using the second order Michigan State University optical potential proposed for low energy pion nucleus elastic scattering. Agreement with the data was obtained using the same density distributions for the protons and neutrons. This work is published in Phys.Rev.C 32 (1985) 995-998.
Further studies of the observed neutron density effect were carried out on Nickel isotopes Phys.Rev.C 38 (1988) 1316-1321 and Tin isotopes. I was invited by Prof. Barry Preedom to defend the NSF funding renewal of this neutron density effect in pion scattering experiments at the Chairman’s conference Room, Department of Physics, University of South Carolina (summer of 1983). I presented the Carbon and Nickel data, where carbon measurement showed a clear neutron density effect but no such effect was observed in Nickel. In the request we were asking funding for continuing this measurement for Tin isotopes. The reviewer asked well in the heavy nucleus like Nickel you have seen no effect, so why continue this measurement in even heaver nucleus. We had not anticipated this question, it was not written any where in our proposal and was not discussed by the professors. In my head, I calculated and answered that the percentage of access neutron in Carbon and Tin isotopes are the same, while in Nickel it is much smaller, hence it will be interesting to see if this effect is truly neutron density effect. Prof. Preedom, a few days later again with coffee in his hand told me that I gave an excellent answer to the question and he had thought I would say well we want to measure it.
I continued to participate in many pion physics experiments at LAMPF and SIN. My Ph.d. dissertation experiment: (π+/-, P) Reaction at Low Excitation Energy, was performed in part at both of these laboratories in 1984.
Abstract: Results of the first experimental search for the excitation of discrete final states following exclusive (π−,p) reactions are reported. The measurements include differential cross section at theta lab=25° for (π±,p) reactions on Mg24, Al27, Ca40, and Ni58 at Tπ=120 MeV and (π−,p) on C12 at Tπ=145 MeV. The (π−,p) reactions yield peaks with dσ/dΩ≤1 μb/sr compared to 7–22 μb/sr for peaks from (π+,p) reactions. The shape of the continuum in an excitation energy range of 10–40 MeV was found to be independent of pion charge and target. The ratios of (π+,p)/(π−,p) averaged over excitation energy and the ratios of the same reaction on different nuclei are presented. The magnitude of the proton yield in the low excitation continuum is more than 20 times larger for π+ than for π−, which supports a two-nucleon absorption model including pion charge exchange. This work is published in Phys.Rev.C 35 (1987) 1567-1569
I was the Principal Investigator of a Pion absorption on Helium experiment which was approved by the Program Advisory Committee of the LAMPF. That experiment was never carried out as I moved to the Fermi National Accelerator Laboratory as a Research Associate and started working on High Energy Physics Experiments.