通过π⁰ 电产生在高动量转移下测量N→Δ⁺(1232)跃迁
Measurement of the N-->Delta(+)(1232) transition at high-momentum transfer by pi(0) electroproduction.
作者信息
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, Doughty D, Dugger M, Dytman S, Dzyubak O P, Egiyan H, Egiyan K S, Elouadrhiri L, Eugenio P, Fatemi R, Fedotov G, Feldman G, Feuerbach R J, Funsten H, Garçon M, Gavalian G, Gilfoyle G P, Giovanetti K L, Girod F X, Goetz J, Gordon C I O, Gothe R W, Griffioen K A, Guidal M, Guillo M, Guler N, Guo L, Gyurjyan V, Hadjidakis C, Hakobyan R S, Hardie J, Heddle D, Hersman F W, Hleiqawi I, Holtrop M, Hicks K, Hyde-Wright C E, Ilieva Y, Ireland D G, Ishkhanov B S, Ito M M, Jenkins D, Jo H S, Juengst H G, Kellie J D, Khandaker M, Kim W, Klein A, Klein F J, Klimenko A V, Kossov M, Kramer L H, Kubarovsky V, Kuhn J, Kuhn S E, Lachniet J, Laget J M, Langheinrich J, Lawrence D, Lee T, Li Ji, Livingston K, Marchand C, Markov N, McAleer S, McKinnon B, McNabb J W C, Mecking B A, Mehrabyan S, Melone J J, Mestayer M D, Meyer C A, Mikhailov K, Minehart R, Mirazita M, Miskimen R, Mokeev V, Morand L, Morrow S A, Mueller J, Mutchler G S, Napolitano J, Nasseripour R, Niccolai S, Niculescu G, Niculescu I, Niczyporuk B B, Niroula M, Niyazov R A, Nozar M, O'rielly G V, Osipenko M, Ostrovidov A I, Park K, Pasyuk E, Philips S A, Pivnyuk N, Pocanic D, Pogorelko O, Polli E, Pozdniakov S, Preedom B M, Price J W, Prok Y, Protopopescu D, Qin L M, Raue B A, Riccardi G, Ricco G, Ripani M, Ritchie B G, Ronchetti F, Rosner G, Rossi P, Rubin P D, Sabatié F, Salgado C, Santoro J P, Sapunenko V, Schumacher R A, Serov V S, Sharabian Y G, Skabelin A V, Smith E S, Sober D I, Stavinsky A, Stepanyan S S, Stepanyan S, Stokes B E, Strakovsky I I, Strauch S, Taiuti M, Tedeschi D J, Thoma U, Tkabladze A, Todor L, Tkachenko S, Tur C, Vineyard M F, Vlassov A V, Weinstein L B, Weygand D P, Williams M, Wolin E, Wood M H, Yegneswaran A, Zana L, Zhang B, Zhang J, Zhao B
机构信息
Rensselaer Polytechnic Institute, Troy, New York 12180-3590, USA.
出版信息
Phys Rev Lett. 2006 Sep 15;97(11):112003. doi: 10.1103/PhysRevLett.97.112003.
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).
我们报告了对专属电产生反应γ()p→π(0)p的一项新测量，以通过N→Δ跃迁中磁（M(1+)）、电（E(1+)）和标量（S(1+)）多极子的Q(2)依赖性来探索从软非微扰物理到硬过程的演化。9000个微分截面数据点涵盖了从阈值到1.4 GeV/c(2)的W、4π质心立体角以及从3到6 GeV(2)/c(2)的Q(2)，这是迄今所达到的最高值。结果发现，磁形状因子G(M)()随Q(2)的下降比质子磁形状因子更陡峭，E(1+)/M(1+)的比值小且为负，表明强烈的螺旋度不守恒，S(1+)/M(1+)的比值为负，但其大小随Q(2)增加。
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