Ph.D Thesis
Title :- A calculation of (d^2 σ)/(d" ?" dT_π ) (Double differential scattering cross sections) for inclusive ?-^4 He Double Charge Exchange at ?T_π?^in≤270 MeV.
Adviser :- Prof. Glen A Rebka, Dept. of Physics & Astronomy, University of Wyoming, Laramie WY -82071 USA.
Abstract :-
Pi-nuclear scattering calculations that use multiple scattering usually require the knowledge not only of the pi-nucleon interaction in free space but also its modification inside a nuclear medium. A relativistic 2 body model consisting of the pion, the ith nucleon, and the residual nucleus called the core, is developed. In this model the nucleon-core separation in coordinate space is approximated by the separation between the Center of Mass of the of the π- ith nucleon subsystem called the Composite and the Core. An Instant form of Dynamics is employed to introduce interactions between the pion & the nucleon and between the πN Composite and the Core. The Composite-Core Hamiltonian is assumed to admit no bound states. The relativistic 3-body total Hamiltonian is then diagonalized by nested separable eigenfunctions. This diagonalization allows the construction of an expression for the matrix elements of the medium modified πN scattering operator τi in the lab frame in terms of the CM πN free space t-matrix elements. Terms that are quadratic in the N t-matrix elements in this expression are neglected.
The Sequential Single Charge eXchange (SSCX) mechanism contribution to the inclusive π- 4He Double Charge eXchange (DCX) is calculated using only the double scattering term of the Watson multiple scattering series. The τ – matrix elements obtained from this 3-body model are used for the first scattering . It contains explicit dependence upon the matrix elements of the Composite- Core scattering operator t πN-C. This explicit dependence is ignored in the second scattering. The pole of the intermediate pion green function is fixed from the 3-Body model considerations and the requirement that the pion be on its mass shell at the pole.
The calculated inclusive cross sections (d^2 σ)/(dΩdΤ_π ) are compared with the Kinney et.al. experimental results and essential agreement with the spectrum for the incident pion kinetic energy T_π^in=120 MeV is found. At higher values of T_π^in<270 MeV only qualitative agreement with experiment is claimed. Zeroing t πN-C changes the cross section magnitudes by < 5 %. The presence of the P33 partial wave, the choice of the appropriate width in the momentum space of the Gaussian Wave function for the ground state of 4He, and the inclusion of both single and double spin flip amplitudes are found to be important.
Work Experience :-
My entire work experience has been in the Birla Institute of Technology & Science (BITS) now known as BITS-Pilani. I joined BITS Pilani in Rajasthan in Nov-1995, and worked there until May-2004. The Goa Campus (later renamed as K.K. Birla Goa Campus) started in the academic session 2004-05 and I transferred from Pilani to Goa to be in the newly started campus. The table below summarizes my progress in BITS from the starting date to the present.
| Month/Year | Position | Campus | Location |
1. | Nov-1995 to Jan -2000 | Lecturer | Pilani | Pilani, Rajasthan - 333031 |
2. | Feb-2000 to May-2004 | Assist. Prof | Pilani | Pilani, Rajasthan - 333031 |
3. | June-2004 to Jan-2005 | Assist Prof | Goa | Zuarinagar, Goa - 403726 |
4. | Jan-2005 to July-2010 | Assoc. Prof | Goa | Zuarinagar, Goa - 403726 |
5. | July-2010 to present | Professor | Goa | Zuarinagar, Goa - 403726 |