Antiprotonic strong interaction

The spin-averaged hadronic shifts and widths of the Is and the 2p state have been measured both for antiprotonic hydrogen and deuterium. Furthermore, information on individual hyperfine states was obtained for pH. Here, the strong-interaction parameters of the 23Po hyperfine state could be determined using a crystal spectrometer. The hadronic effects in the lx5o and 13,S i hyperfine ground states were derived with the help of a few assumptions. 

HGURE 8.31 The phase diagram of strongly interacting matter. The antiproton-induced cold compression (c.c.) takes place at low temperatures and high densities, a regime that cannot be accessed in heavy-ion collisions. The curves with arrows denote dynamic trajectories of matter in heavy-ion collisions as expected at the future GSI facility and the relativistic heavy-ion collider (RHIC) at Brookhaven National Laboratory. 

Using exotic atoms, one can separately study the distributions of protons and neutrons in the nucleus by comparing muon and pion absorption. Muons are absorbed by the protons only, whereas the strong interaction is independent of the electric charge, so hadrons (pions, kaons, and antiprotons) interact equally with protons and neutrons. 

Strong interaction between the captured hadron and the nucleus shifts and broadens the energy levels this makes it possible to study strong interaction effects using X-ray spectroscopy. The shift and broadening of the atomic s and p levels in the antiproton-proton system are... 

There is a kind of atom where the nuclear effects are very large - exotic atoms, containing hadrons, i.e. particles that can interact strongly pions, antiprotons, kaons etc. In such atoms any advanced high-accurate QED theory is not necessary and a goal to study such atoms is to measure these nuclear parameters. An important feature of any spectroscopic measurement is its high accuracy in respect to non-spectroscopic methods. That is very important for exotic atoms, because some, like e.g. pionium (7r+7r -system or bound 7rp-system), are available in very small quantities (a few hundreds) [35],... 

Physical information can be obtained, e.g., by measuring the shift and broadening of the energy levels of the hadron in the atom due to nuclear interactions as compared to a purely electromagnetic case. The shifts and widths can be measured for one or two levels only in each kind of hadronic atom as the strong nuclear absorption - which causes the level broadening -terminates the atomic cascade at a certain principal quantum number This lowest n sensitively depends on the mass of the particle and on the atomic number of the nucleus min = 1 for pionic oxygen and 8 for antiprotonic nickel. 

In fig. 5.6 we plot the comparison of direct ionization for protons and antiprotons on hydrogen. It is a remarkable fact that protons and antiprotons have cross sections showing marked deviations from the Born result but are, by this measure, very close in value to each other. Why From our previous discussions on Dipole Dominance and the Glauber method one might conclude that here we have an example of the former, not unlike the 1S-2P transition. Or, a brilliant confirmation of the predictive power of the latter. And at the same time a demonstration of the poverty of the ideas of binding and polarization that should surely predict a cross section more symmetric about the Born result. Perhaps those ideas are only good for weak perturbative situations and our physical intuition lets us down when the interaction is strong. 

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