FIZIKA B 8 (1999) 2, 345-352

NEW RESULTS ON PERTURBATIVE COLOUR TRANSPARENCY IN QUASI-EXCLUSIVE ELECTROPRODUCTION

PANKAJ JAIN^a, BIJOY KUNDU^a, JOHN RALSTON^b and JIM SAMUELSSON^a

^aPhysics Department, I.I.T. Kanpur, 208016, India
^bDepartment of Physics & Astronomy, University of Kansas, Lawrence, KS 66045, U.S.A.

Received 20 January 1999; Accepted 24 June 1999

We review the perturbative QCD formalism of hadronic electromagnetic form factors and the colour transparency ratio for quasi-exclusive electroproduction of the proton and pion from nuclear targets. We have completed the first full calculations including all leading-order quark subprocesses and integrations over distribution amplitudes, including Sudakov effects. For the case of the proton, the calculated result shows scaling beyond Q² = 10 GeV². The calculation incorporating filtering due to the nuclear medium is cleaner than the corresponding calculation in free space because of attenuation of large distance amplitudes. We find that the colour transparency ratio is rather insensitive to theoretical uncertainties inherent in the perturbative formalism, such as the choice of the hadron distribution amplitude.

PACS numbers: 13.40.Fn, 12.38.Bx, 14.20.Dh
UDC 539.126

Keywords: proton and pion quasi-exclusive electroproduction, nuclear targets , perturbative QCD formalism, hadronic electromagnetic form factors, colour transparency ratio

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