We report a new measurement of the exclusive electroproduction reaction gamma(*)p ->pi(0)p to explore the evolution from soft nonperturbative physics to hard processes via the Q(2) dependence of the magnetic (M1+), electric (E1+), and scalar (S1+) multipoles in the N ->Delta transition. 9000 differential cross section data points cover W from threshold to 1.4 GeV/c(2), 4 pi center-of-mass solid angle, and Q(2) from 3 to 6 GeV2/c(2), the highest yet achieved. It is found that the magnetic form factor G(M)(*) decreases with Q(2) more steeply than the proton magnetic form factor, the ratio E1+/M1+ is small and negative, indicating strong helicity nonconservation, and the ratio S1+/M1+ is negative, while its magnitude increases with Q(2).
MEASUREMENT OF THE N ---> DELTA+(1232) TRANSITION AT HIGH MOMENTUM TRANSFER BY PI0 ELECTROPRODUCTION
CORVISIERO, PIETRO;RICCO, GIOVANNI;TAIUTI, MAURO GINO;
2006-01-01
Abstract
We report a new measurement of the exclusive electroproduction reaction gamma(*)p ->pi(0)p to explore the evolution from soft nonperturbative physics to hard processes via the Q(2) dependence of the magnetic (M1+), electric (E1+), and scalar (S1+) multipoles in the N ->Delta transition. 9000 differential cross section data points cover W from threshold to 1.4 GeV/c(2), 4 pi center-of-mass solid angle, and Q(2) from 3 to 6 GeV2/c(2), the highest yet achieved. It is found that the magnetic form factor G(M)(*) decreases with Q(2) more steeply than the proton magnetic form factor, the ratio E1+/M1+ is small and negative, indicating strong helicity nonconservation, and the ratio S1+/M1+ is negative, while its magnitude increases with Q(2).
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