John Watson

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FROM THE NUCLEAR SHELL MODEL TO SHORT-RANGE CORRELATIONS: THE ADVENTURE OF A LIFETIME

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The nuclear shell model, for which the Nobel Prize was awarded in 1963, has been highly successful in describing the properties of nuclear ground states and low-lying excited states. It has been clear for some time, however, that only 65 or 70% of the nucleons in nuclei are undergoing the type of independent-particle motion that is the hallmark of the shell-model [1]. Also, scaling studies of inclusive high-energy electron scattering indicate that at any given moment roughly 20% of the nucleons in a nucleus are involved in short-range correlated (SRC) pairs [2]. My recent research has focused on experiments where such SRC pairs can be observed directly in high-energy, high-momentum-transfer reactions with protons at Brookhaven National Laboratory[3,4], and with electrons at Thomas Jefferson Laboratory[5,6]. These measurements have yielded the startling result that n-p SRC pairs outnumber p-p SRC pairs by a factor of nearly 20. This could have significant implications for modeling neutron stars. [1] L. Lapikas, Nucl. Phys. A553, 297c (1993). [2] K.S. Egyian at al., Phys. Rev. C68 014313 (2003); Phys. Rev. Lett 96 082501 (2006). [3] A. Tang et al., Phys. Rev. Lett. 90 042301 (2003). [4] E. Piasetzky et al., Phys. Rev. Lett. 97 162504 (2006). [5] R. Schneor et al., Phys. Rev. Lett. 99 072501 (2007). [6] R. Subedi et al., Science 320, 1476 (2008).