Short-Range Correlations (SRCs): Short-range correlations - brief fluctuations of high relative-momentum nucleon pairs - have important consequences for nuclear physics, high-energy physics, atomic physics and astrophysics. These pairs form some of the most dense states of cold matter achievable on earth, making them an ideal system to study the interplay between partonic (quark-gluon) and nucleonic degrees of freedom in nuclear systems.
Recent developments in high-energy high-luminosity electron and proton accelerators have allowed us to resolve SRCs with unprecedented accuracy, revolutionizing our understanding of the role SRCs play in nuclei.
Our SRC studies focus primarily on exclusive breakup reactions where high-energy probes are used to break up SRC pairs, and specialized detectors measure all of the particles emitted in the process. These experiments have allowed us to quantify properties of SRC pairs (isospin decomposition, nuclear mass and asymmetry dependence, c.m. momentum distribution) and to probe the elusive short-range part of the nuclear interaction.
Our current program focuses on data-mining analyses of existing 6 GeV CLAS data from a wide range of nuclei (d, He-3, He-4, C-12, Al-27, Fe-56, and Pb-208), future 12 GeV measurements of asymmetric nuclei (e.g. 3H - 3He, 40Ca-48Ca) at JLab and hadron beam based measurements at GSI and JINR.
Medium-Energy Nuclear Physics (Back)
In-Medium Structure Functions and the EMC Effect: Since nucleons have non-zero size, their internal structure may well be modified when their quark distributions begin to overlap those of their neighbors. While clear experimental evidence for modification of the partonic structure functions of nucleons bound in nuclei, known as the EMC effect, was first seen over 30 years ago, the microscopic origin of this phenomenon is still unclear.
Some time ago, we showed a phenomenological correlation between the average nucleon modification in various nuclei and the amount of SRC pairing in those nuclei. This was an initial indication that bound nucleon modification is related to high-virtuality nucleons in nuclei. More recently, we presented a theoretical model that quantitatively links SRCs and the EMC effect via the effect of QCD Point-Like Configuration (PLC) supression in nuclei and the exited nature of SRC nucleons.
Two new experiments approved to run at Jefferson Lab will test this theoretical picture by measuring the virtuality dependence of the structure functions of protons and neutrons bound in the deuteron. The measurement will use, d(e,e' N_recoil) Tagged-DIS reaction, using high-resolution spectrometers to detect the DIS scattered electron and new large acceptance detectors (LAD and BAND) to measure recoiling protons and neutrons. We are building these detectors as part of an international collaboration between the US (MIT, ODU, Jefferson-Lab), Israel (TAU), and Chile (TUSM).
Our Medium-Energy nuclear physics program spans the globe, with various activities taking place at accelerator laboratories in the USA (Jefferson-Lab @ Newport News, VA), Russia (JINR @ Dubna) and Germany (GSI @ Darmstadt).