Multi-Nucleon Short-Range Correlation Model for Nuclear Spectral Functions.*

We develop a theoretical model for~ nuclear~ spectral functions at high missing momenta~ and energies based on the~ multi-nucleon short-range correlation(SRC) model aimed at probing~nuclear structure at short-distances.~The model is based on the effective Feynman diagram method which allows us to account for the~relativistic effects~ in the SRC domain. We derive the contribution of two-nucleon SRC with center of mass motion, and three-nucleon SRCs to the nuclear spectral functions.~The spectral functions are based on two~ theoretical approaches in evaluating covariant~Feynman diagrams: In the first,~ referred to as virtual nucleon approximation, ~ we~ reduce~ Feynman diagrams to the time~ordered~ non-covariant diagrams~ by evaluating nucleon spectators on the SRC at their positive energy poles,~neglecting~ the contribution from vacuum diagrams.~In the second approach, referred to as light-front~ approximation, we formulate the boost invariant nuclear spectral function on the~ light-front reference frame, on which the vacuum diagrams are suppressed.~Numerical calculations and parametrization of spectral functions and momentum distributions are presented.