Electroexcitation of the Roper resonance for 1.7 < Q2 < 4.5 -GeV2 in vec-ep ---> en pi

• Published in: Physical review. C, Nuclear physics Nuclear physics, 2008-10, Vol.78
• Main Authors: Aznauryan, Inna, Amaryan, Moscov, Ambrozewicz, Pawel, Anghinolfi, Marco, Baillie, Nathan, Ball, Jacques, Baltzell, Nathan, Barrow, Steve, Battaglieri, Marco, Bektasoglu, Mehmet, Bellis, Matthew, Berman, Barry, Biselli, Angela, Briscoe, Wilbert, Brooks, William, Careccia, Sharon, Cazes, Antoine, Coltharp, Philip, Cords, Dieter, Corvisiero, Pietro, Crabb, Donald, Cummings, John, De Masi, Rita, Deur, Alexandre, Dhuga, Kalvir, Dickson, Richard, Donnelly, J, Doughty, David, Dzyubak, Oleksandr, Elfassi, Lamiaa, Elouadrhiri, Latifa, Eugenio, Paul, Fatemi, Renee, Gavalian, Gagik, Gohn, Wesley, Golovach, Evgeny, Gordon, Christopher, Guidal, Michel, Guler, Nevzat, Guo, Lei, Gyurjyan, Vardan, Hadjidakis, Cynthia, Hafnaoui, Khadija, Hakobyan, Rafael, Hanretty, Charles, Hardie, John, Hicks, Kenneth, Hyde, Charles, Jo, Hyon-Suk, Joo, Kyungseon, Juengst, Henry, Kellie, James, Kim, Kui, Kossov, Mikhail, Kramer, Laird, Kubarovsky, Valery, Kuhn, Sebastian, Kuznetsov, Viacheslav, Lachniet, Jeff, Lawrence, Dave, Lima, Ana, MacCormick, Marion, Mattione, Paul, McKinnon, Bryan, Mecking, Bernhard, Mehrabyan, Surik, Mestayer, Mac, Mibe, Tsutomu, Minehart, Ralph, Mirazita, Marco, Miskimen, Rory, Morand, Ludyvine, Mueller, James, Nasseripour, Rakhsha, Niculescu, Maria-Ioana, Niczyporuk, Bogdan, Niroula, Megh, Niyazov, Rustam, Pasyuk, Evgueni, Anefalos Pereira, S, Pierce, Jerome, Pocanic, Dinko, Preedom, Barry, Prok, Yelena, Qin, Liming, Raue, Brian, Riccardi, Gregory, Ricco, Giovanni, Ripani, Marco, Saini, Mukesh, Salamanca, Julian, Sapunenko, Vladimir, Schumacher, Reinhard, Serov, Vladimir, Sharabian, Youri, Shaw, J, Skabelin, Alexander, Sokhan, Daria, Stepanyan, Samuel, Stokes, Burnham
• Format: Article
• Language: English
• Subjects: AMPLITUDES; ASYMMETRY; CROSS SECTIONS; DISPERSION RELATIONS; ELECTROPRODUCTION; EXCITATION; HELICITY; ISOBAR MODEL; N-1440 BARYONS; PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; POLARIZED BEAMS; PROTONS
• ISSN: 0556-2813; 1089-490X
• DOI: 10.1103/PhysRevC.78.045209

DOI: http://dx.doi.org/10.1103/PhysRevC.78.045209 The helicity amplitudes of the electroexcitation of the Roper resonance are extracted for 1.7 < Q2 < 4.5 GeV2 from recent high precision JLab-CLAS cross section and longitudinally polarized beam asymmetry data for pi+ electroproduction on protons at W=1.15-1.69 GeV. The analysis is made using two approaches, dispersion relations and a unitary isobar model, which give consistent results. It is found that the transverse helicity amplitude A_{1/2} for the gamma* p -> N(1440)P11 transition, which is large and negative at Q2=0, becomes large and positive at Q2 ~ 2 GeV2, and then drops slowly with Q2. The longitudinal helicity amplitude S_{1/2}, which was previously found from CLAS ep -> eppi0,enpi+ data to be large and positive at Q2=0.4,0.65 GeV2, drops with Q2. Available model predictions for gamma* p -> N(1440)P11 allow us to conclude that these results provide strong evidence in favor of N(1440)P11 as a first radial excitation of