Compton Scattering from the Proton Below Pion Threshold
Compton Scattering from the Proton Below Pion Threshold

Author: Bruce Everett MacGibbon

Publisher:

Published: 1995

Total Pages: 296

ISBN-13:

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The Compton scattering cross section on the proton was measured at laboratory angles of 90$spcirc$ and 135$spcirc$, using 70-100 MeV tagged photons, and simultaneously using 100-150 MeV untagged photons, in order to determine the electric and magnetic polarizabilities. The 135$spcirc$ cross section is sensitive to the difference of the electric and magnetic polarizabilities, $bar alpha - barbeta$, while the 90$spcirc$ cross section is sensitive to the electric polarizability $bar alpha$. Using the model independent sum rule constraint for $bar alpha$ + $bar beta$ and a model dependent dispersion relation calculation, the values for the polarizabilities extracted from the cross sections are:$$bar alpha = (12.5 pm 0.6 pm 0.8 pm 0.6) times 10sp{-4} fmsp3cr bar beta = (1.8 mp 0.6 mp 0.8 mp 0.6) times 10sp{-4} fmsp3$$where the errors shown are statistical, systematic, and model, respectively.

Measurement of the Generalized Polarizabilities of the Proton in Virtual Compton Scattering at Q2
Measurement of the Generalized Polarizabilities of the Proton in Virtual Compton Scattering at Q2

Author:

Publisher:

Published: 2003

Total Pages:

ISBN-13:

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Virtual Compton Scattering is studied at the Thomas Jefferson National Accelerator Facility in the energy domain below pion threshold and in the Delta(1232) resonance region. The data analysis is based on the Dispersion Relation (DR) approach. The electric and magnetic Generalized Polarizabilities (GPs) of the proton and the structure functions Pll-Ptt/epsilon and Plt are determined at four-momentum transfer squared Q2=0.92 and 1.76 GeV2. The DR analysis is consistent with the low-energy expansion analysis. The world data set indicates that neither the electric nor magnetic GP follows a simple dipole form.

Virtual Compton Scattering
Virtual Compton Scattering

Author: L. Van Hoorebeke

Publisher:

Published: 2003

Total Pages:

ISBN-13:

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Virtual Compton Scattering o013 the proton has been studied at Q 2 -values of 1:0 and 1:9 (GeV=c) 2 in Hall A at the Thomas Je013erson National Accelerator Facility (JLab). Data were taken below and above the pion production threshold as well as in the resonance region. Results obtained below pion threshold at Q 2 = 1:0 (GeV=c) 2 are presented in this paper.

Measurement of the Generalized Polarizabilities of the Proton in Virtual Scattering at Q2
Measurement of the Generalized Polarizabilities of the Proton in Virtual Scattering at Q2

Author:

Publisher:

Published: 2003

Total Pages:

ISBN-13:

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Virtual Compton Scattering is studied at the Thomas Jefferson National Accelerator Facility at low Center-of-Mass energies, below pion threshold. Following the Low Energy Theorem for the ep --> ep gamma process, we obtain values for the two structure functions Pll-Ptt/epsilon and Plt at four-momentum transfer squared Q2=0.92 and 1.76 GeV2.

Deuteron Compton Scattering Below Pion Threshold
Deuteron Compton Scattering Below Pion Threshold

Author: Luke S. Myers

Publisher:

Published: 2011

Total Pages:

ISBN-13:

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A series of experiments were performed at the Tagged Photon Facility at MAX-lab in Lund, Sweden to study photon scattering from the deuteron and extract the neutron polarizabilities. The deuteron Compton scattering cross section was measured at laboratory angles of $60^o$, $120^o$, and $150^o$ for photon energies from 70 - 112 MeV. The photons were scattered from the Lund liquid deuterium target and detected in three large (20'' x 20'') NaI photon spectrometers. These detectors have sufficient energy resolution ($sim$2$%$ at 100 MeV) to separate the elastically and inelastically scattered photons. The extracted scattering cross section for this experiment was found to have angular distributions that matched prior experiments but needed a scaling factor to bring the absolute cross section into agreement. This scaling factor was determined to have a value of 1.47 $pm$ 0.10. Suggestions are made for future studies that could yield further knowledge of the scaling factor and potentially allow for this data to be re-normalized.

Gdh 2000 - The Gerasimov-drell-hearn Sum Rule & The Nucleon Spin Structure In The Resonance Region
Gdh 2000 - The Gerasimov-drell-hearn Sum Rule & The Nucleon Spin Structure In The Resonance Region

Author: Dieter Drechsel

Publisher: World Scientific

Published: 2001-02-05

Total Pages: 430

ISBN-13: 9814491381

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The history of spin in general, and of the nucleon spin structure in particular, has been full of surprises. For the past 25 years deep inelastic lepton scattering has been studied to determine the carriers of the nucleon spin. However, it was realized only recently that a full understanding of the nucleon spin will also require detailed information on the helicity structure in the resonance region, i.e. in the realm of nonperturbative QCD.This volume gives a status report on the spin structure in the nucleon resonance region, focusing on: new experimental results from SLAC and HERMES; a first glance at the JLab experiments to map out the spin structure functions at low and intermediate four-momentum transfers; the pioneering experiment at MAMI (Mainz) to determine the Gerasimov-Drell-Hearn sum rule for real photons; and recent theoretical concepts and investigations to describe the spin structure in the frameworks of higher twist expansion, phenomenological models and chiral perturbation theory.

Nstar 2001 - Proceedings Of The Workshop On The Physics Of Excited Nucleons
Nstar 2001 - Proceedings Of The Workshop On The Physics Of Excited Nucleons

Author: Dieter Drechsel

Publisher: World Scientific

Published: 2001-08-28

Total Pages: 528

ISBN-13: 9814490040

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The study of N∗s can provide us with critical insights into the nature of QCD in the confinement domain. The keys to progress in this domain are the identification of its important degrees of freedom and the effective forces between them. The nucleon is the simplest system in which the nonabelian character of QCD is manifest. There are Nc quarks in a baryon because there are Nc colors, and as a consequence Gell-Mann and Zweig were forced to introduce the quarks in order to describe the octet and decuplet baryons.This volume gives a status report on the recent experimental and theoretical results in the field of nucleon resonance physics. A wealth of new high precision data was presented from facilities around the world, such as BES, BNL, ELSA, GRAAL, JLab, MAMI, MIT/Bates, SPring8, and Yerevan. Particular emphasis was laid on polarization degrees of freedom and large acceptance detectors as precision tools for studying small but important transition amplitudes, and the helicity (spin) structure of the nucleon. There were new results describing the nucleon resonance structure on the basis of quantum chromodynamics, either directly in terms of quarks and gluons by means of lattice gauge theory, or in terms of hadrons in the framework of chiral field theories. A status report on duality showed the surprising connections between the physics of the low energy nucleon resonance region and the realm of quark structure functions in deep inelastic scattering. Finally, this volume contains a summary report of the BRAG workshop, devoted to the analysis of baryon resonances.