1. Nuclear and Radiation Physics, BAU, First Semester, 2007-2008 (Saed Dababneh). 1 Nuclear Force (Origin of Binding) Recall Recall Atomic Binding Energies for hydrogen like atoms: Dimensionless fine structure constant. with Bohr radii: Coupling constant  Strength. Charge. Mediators (Bosons). =1

2. Nuclear and Radiation Physics, BAU, First Semester, 2007-2008 (Saed Dababneh). 2 Nuclear Force The deuteron: proton-neutron bound state. Hydrogen:E 1 = … eVr 1 = …x10 -10 m Positronium:E 1 = … eV Deuteron:E 1 = … MeVr 1 = …x10 -15 m HW 17 !!!!!!!!! QCD Color charge! QFT

3. Nuclear and Radiation Physics, BAU, First Semester, 2007-2008 (Saed Dababneh). 3 Nuclear Force

4. Nuclear and Radiation Physics, BAU, First Semester, 2007-2008 (Saed Dababneh). 4 Nuclear Force repulsive core Attractive but repulsive core. At what separation? Saturation? Get an estimate for nuclear density and thus inter- nucleon distance. Have you done that?

5. Nuclear and Radiation Physics, BAU, First Semester, 2007-2008 (Saed Dababneh). 5 Is the nucleon bounded equally to every other nucleon? C ≡ this presumed binding energy. B tot = C(A-1)  A  ½ B ave = ½ C(A-1) Linear ??!!! Directly proportional ??!!! Clearly wrong … !  wrong assumption finite range  finite range of strong force, and force saturation. Nuclear Force

6. Nuclear and Radiation Physics, BAU, First Semester, 2007-2008 (Saed Dababneh). 6 Nuclear Force Rate of decay or interaction R   (E). Coupling constant . Vertices in the diagrams. For decays R  1/T. (T  Lifetime). The density of states  is a measure of the number of quantum mechanical states per unit energy range that are available for the final products. The more states that are available, the higher the transition rate. The coupling constant  can be interpreted as an intrinsic rate.

7. Nuclear and Radiation Physics, BAU, First Semester, 2007-2008 (Saed Dababneh). 7 Electrostatic and gravitational potential  long range (V  1/r). Near constancy of nuclear binding energy per nucleon B/A means that each nucleon feels only the effect of a few neighbors. This is called saturation. It implies also that the strong internucleon potential is short range. Range is of order of the 1.8 fm internucleon separation. Since volume  A, nuclei do not collapse, there is a very short range repulsive component. Exchange. Some particles are immune. Like what? Is nuclear physics just quark chemistry? Charge independence. Spin dependence. (Deuteron). Non-central (tensor) component  conservation of orbital angular momentum….? Nuclear Force