Measurement of the N-->Delta(+)(1232) transition at high-momentum transfer by pi(0) electroproduction.
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 (M(1+)), electric (E(1+)), and scalar (S(1+)) multipoles in the N-->Delta transition. 9000 differential cross section data points cover W from threshold to 1.4 GeV/c(2), 4pi center-of-mass solid angle, and Q(2) from 3 to 6 GeV(2)/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 E(1+)/M(1+) is small and negative, indicating strong helicity nonconservation, and the ratio S(1+)/M(1+) is negative, while its magnitude increases with Q(2).
Ungaro
M
M
Rensselaer Polytechnic Institute, Troy, New York 12180-3590, USA.
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Ambrozewicz
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Audit
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Bagdasaryan
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Barrow
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Batourine
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Battaglieri
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Berman
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Bradford
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Briscoe
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Butuceanu
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Careccia
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Chen
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Coltharp
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Corvisiero
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Cummings
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Sanctis
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Degtyarenko
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Dennis
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Dharmawardane
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Eugenio
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Fatemi
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Hadjidakis
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Ireland
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Jenkins
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Jo
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Juengst
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Kellie
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Niczyporuk
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Niroula
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Osipenko
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Park
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Pasyuk
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Philips
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Pocanic
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Pogorelko
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Polli
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Pozdniakov
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Preedom
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Protopopescu
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Raue
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Ricco
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Ripani
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Ritchie
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Ronchetti
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Rosner
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Rossi
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Rubin
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Salgado
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Santoro
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Sapunenko
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Schumacher
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Serov
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Sharabian
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Skabelin
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Smith
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Stavinsky
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Stepanyan
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Stokes
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Strakovsky
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Thoma
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Todor
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Tkachenko
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Tur
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Vineyard
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Vlassov
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Weinstein
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Wolin
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Yegneswaran
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Zhang
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Zhao
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