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Measurement of the N-->Delta(+)(1232) transition at high-momentum transfer by pi(0) electroproduction |
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| Authors: | Ungaro M Stoler P Aznauryan I Burkert V D Joo K Smith L C Adams G Amarian M Ambrozewicz P Anghinolfi M Asryan G Audit G Avakian H Bagdasaryan H Ball J P Baltzell N A Barrow S Batourine V Battaglieri M Bedliski I Bektasoglu M Bellis M Benmouna N Berman B L Biselli A S Bonner B E Bouchigny S Boiarinov S Bradford R Branford D Briscoe W J Brooks W K Bültmann S Butuceanu C Calarco J R Careccia S L Carman D S Cazes A Chen S Cole P L Coltharp P Cords D Corvisiero P Crabb D Cummings J P Sanctis E De Devita R Degtyarenko P V Denizli H Dennis L Deur A Dharmawardane K V Djalali C Dodge G E Donnelly J |
| Institution: | Rensselaer Polytechnic Institute, Troy, New York 12180-3590, USA. |
| 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 (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). |
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