Electroproduction of the Delta(1232) Resonance at High Momentum Transfer

Journal Article · Mon Jan 04 04:00:00 EST 1999 · Physical Review Letters

OSTI ID:837875

Frolov, Valera; Adams, Gary; Ahmidouch, Abdellah; Armstrong, Christopher; Assamagan, Ketevi; Avery, Steven; Baker, O; Bosted, Peter; Burkert, Volker; Carlini, Roger; Davidson, R M; Dunne, James; Eden, T; Ent, Rolf; Gaskell, David; Gueye, Paul; Hinton, Wendy; Keppel, Cynthia; Kim, Wooyoung; Klusman, Mike ; Koltenuk, Douglas; Mack, David; Madey, Richard; Meekins, David; Minehart, Ralph; Mitchell, Joseph; Mkrtchyan, Hamlet; A Mukhopadhyay, N C; Napolitano, James; Niculescu, Gabriel; Niculescu, Maria-Ioana; Nozar, Mina; Price, John; Stoler, Paul; Tadevosyan, Vardan; Tang, Liguang; Witkowski, Michael; Wood, Stephen

Jefferson Lab experiment E94-014 measured the excitation of the Delta (1232) resonance via the reaction p(e,e{prime}p){pi}{sup 0} at Q{sup 2} near 2.8 and 4 Gev{sup 2}. This is the highest Q{sup 2} for which exclusive resonance electroproduction has ever been observed. Decay distributions of the Delta (1232) resonance into the ppi{sup 0} final state were measured over a wide range of barycentric decay angles and energies. The goal of this experiment is to assess the transition in Q{sup 2} from the constituent quark model (CQM) to the regime where hard processes become important. At Q{sup 2} {approx} few GeV{sup 2}/c{sup 2} the ratio E{sub 1+}/M{sub 1+} depends dramatically on the theoretical description, varying from a few 10{sup -2} in the CQM limit, to about 1 in the pQCD limit. Preliminary analysis of the data shows that the ratio E{sub 1+}/M{sub 1+} remains small at Q{sup 2} up to 4 Gev{sup 2}/c{sup 2}. After first pass analysis we obtain E{sub 1+}/M{sub 1+} = -4.1 {+-} 1.2 at Q{sup 2} = 2.8 Gev{sup 2}/c{sup 2} and E{sub 1+}/M{sub 1+} = -7.9 {+-} 0.8 at Q{sup 2} = 4 Gev{sup 2}/c{sup 2} (statistical errors only).

• Research Organization: Thomas Jefferson National Accelerator Facility, Newport News, VA (US)
• Sponsoring Organization: USDOE Office of Energy Research (ER) (US)
• DOE Contract Number: AC05-84ER40150
• OSTI ID: 837875
• Report Number(s): JLAB-PHY-98-08; DOE/ER/40150-3217; hep-ex/9808024
• Journal Information: Physical Review Letters, Journal Name: Physical Review Letters Vol. 82
• Country of Publication: United States
• Language: English

Related Subjects

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
DECAY
ELECTROPRODUCTION
EXCITATION
MOMENTUM TRANSFER
QUARK MODEL
RESONANCE