A b s t r a c tWe performed coupled-channel calculations for the n o n p e r t u r b a t i v e description of electron-positron pair production in relativistic heavy ion collisions. For the system U92++U92+ at Elab=10 GeV/nucleon and impact parameter b=386 fm we obtained probabilities for pair production with i n n e r -s h e l l capture that exceed the results of first order p e rt u r b a t i o n theory b y two orders of magnitude.
I. I n t r o d u c t i o nToday there is i n t e r e s t in electron-positron production b y relativistic heavy ions. In relativistic heavy ion collidere the pair production plays the role of a b a c k g r o u n d effect that might lead to an impairment of the ion beams since the cross sections for pair production with capture are v e r y large. From the theoretical side the pair creation process can serve as a t e s t i n g g r o u n d for n o n p e rt u r b a t i v e methods in QED, because the coupling constant Za is n e a r l y one and a failure of first order theories can be expected. In this contribution we s t u d y n o n p e r t u r b a t i v e effects on the electron-positron creation in relativistic heavy ion collisions. We c a r r y out coupled channel calculations for a collision of U 92+ on U 92+ at an e n e r g y of Elab=10 GeV/nucleon and compare the results with those of first order p e r t u r b a t i o n theory.C o u p l e d c h a n n e l f o r --m a l i s mIn order to describe n o n p e r t u r b a t i v e l y electronpositron pair production we solve the time-dependent Dirac equation for the electron wave f u n ction b y the coupled channel formalism [1,2]. Expanr sion of the electron wave function in terms of t a rg e t -c e n t e r e d hydrogenic Coulomb-Dirac functions results in the coupled channel equations: " -Z<¢. i aji-= J IV(r,t)l¢l.> exp(i(E:-Ek)t)aki.(1) k J * Work supported b y BMFT (06 GI 709) and GSI (Darmstadt)For the positive and negative continuum a discretization by means of time-dependent relativistic wave-packets has been employed. The perturbation operator V describes the interaction between the electron and the projectile. We neglect the recoil of the target, the deflection of the projectile and the electron-electron interaction. Then the operator V is the Lorentz contracted electromagnetic potential of the projectile moving with contant velocity in the target system.After solving the coupled-channel equations (1) b y s t a r t i n g from each initially occupied state of the negative continuum, the time-evolution of the vacuum state is described with a finite Slaterdeterminant [ 3 ]. From this time-dependent Slaterdeterminant the probabilities for the production of free electron-positron pairs and for pair production with atomic i n n e r -s h e l l capture of the electron are extracted b y projection on the corresp o n d i n g final states.I I I . R e s u l t sThe formalism was applied to the system of U 92+ colliding with U 92+ at Elab=10 GeV/nucleon at an impact parameter b=386 fm. The atomic basis set consists of 5 b o u n d states ( l s ...
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