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Stepanyan, S

Publications and source records attributed to Stepanyan, S.

4 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2012

Progress on Neutron-Target Multipoles above 1 GeV

We report a new extraction of nucleon resonance couplings using π{sup -} photo-production cross sections on the neutron. The world database for the process γn → π{sup -}p above 1 GeV has quadrupled with the addition of new differential cross sections from the CEBAF Large Acceptance Spectrometer (CLAS) at Jefferson Lab in Hall B. Differential cross sections from CLAS have been improved with a new final-state interaction determination using a diagrammatic technique taking into account the SAID phenomenological NN and πN final-state interaction amplitudes. Resonance couplings have been extracted and compared to previous determinations. With the addition of these new cross sections, significant changes are seen in the high-energy behavior of the SAID cross sections and amplitudes.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2012

Amplitude analysis of gamma n --> pi- p data above 1 GeV

We report a new extraction of nucleon resonance couplings using pi- photoproduction cross sections on the neutron. The world database for the process gamma n --> pi- p above 1 GeV has quadrupled with the addition of new differential cross sections from the CEBAF Large Acceptance Spectrometer (CLAS) at Jefferson Lab in Hall B. Differential cross sections from CLAS have been improved with a new final-state interaction determination using a diagramatic technique taking into account the NN and piN final-state interaction amplitudes. Resonance couplings have been extracted and compared to previous determinations. With the addition of these new cross sections, significant changes are seen in the high-energy behavior of the SAID cross sections and amplitudes.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Timelike Compton Scattering

Generalized Parton Distributions (GPDs) have become a key concept in our studies of hadron structure in QCD. The measurement of suitable experimental observables and the extraction of GPDs from these data is one of the high priority 12 GeV programs at Jefferson Lab. Deeply Virtual Compton Scattering (DVCS) is generally thought of as the most promising channel for probing GPDs in the valence quark region. However, the inverse process, Timelike Compton Scattering (TCS) can provide an important complementary measurement, in particular of the real part of the Compton amplitude and power corrections at intermediate values of Q{sup 2}. The first studies of TCS using real tagged and quasi-real untagged photons were performed in Hall B at Jefferson Lab.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗