Author: H. C. KirkmanPublisher:
ISBN:
Category :
Languages : en
Pages : 14
Book Description
Measurements of the Polarisation of the Recoil Proton in Elastic Electron Proton Scattering at Q2
Author: H. C. KirkmanMeasurements of the Polarisation of the Recoil Proton in Elastic Electron Proton Scattering at 92
Author: H. C. KirkmanSome Measurements of the Recoil Proton Polarisation in Elastic Electron Proton Scattering
Author: Robert RailtonMeasurements of the Polarisation of the Recoil Proton in Elastic Proton Scattering at Q 2
Author: H. C. KirkmanMeasurements of the Proton Electromagnetic Form Factor Ratio From Elastic E + P -] E + P Scattering at Momentum Transfer Q2
![Measurements of the Proton Electromagnetic Form Factor Ratio From Elastic E + P -] E + P Scattering at Momentum Transfer Q2 PDF](https://books.google.com/books/content/images/frontcover/7oSkAQAACAAJ?fife=w80-h100)
Author: Publisher:
ISBN:
Category :
Languages : en
Pages :
Book Description
Among the fundamental observables of nucleon structure, electromagnetic form factors are a crucial benchmark for modern calculations describing the strong interaction dynamics of the nucleon's quark constituents. Electromagnetic probes are traditionally preferered to the hadronic beams. The electromagnetic interaction is a powerful tool for investigating the nucleon structure since it is well understood and it reveals observables that can be directly interpreted in terms of the current carried by the quarks. Elastic scattering leads to the form factors that describe the spatial charge and current distributions inside the nucleon. The reaction mechanism is assumed to be one photon exchange, the electromagnetic interaction is exactly calculable in QED, and one can safely extract the information on the hadronic vertex. The most important feature of early measurements of proton form factor ratio GEp/GMp with recoil polarization technique at Q2 up to 5.6 (GeV/c)2 is the sharp decline of the ratio with Q2 increases, indicating that GEp falls much faster than GMp. This contradicts to data obtained by Rosenbluth separation method. An intriguing question was whether GEp will continue to decrease or become constant when Q2 increases. New set of measurements of proton form factor ratio GEp/GMp at Q2 = 2.5, 5.2, 6.7 and 8.5 (GeV/c)2 have been conducted at JLab Hall C using ~85% longitudinally polarized electron elastic scattering from unpolarized hydrogen target. Recoil protons were detected in the HMS magnetic spectrometer with the standard detector package, combined with newly installed trigger scintillators and Focal Plane Polarimeter. The BigCal electromagnetic calorimeter (1744 channel) have been used for electron detection. Data obtained in this experiment show that GEp/GMp ratio continued to drop with Q2 and may cross 'zero' at Q2> 10-15 (GeV/c)2. Intensive theoretical and experimental efforts over the past decade have aimed at explaining the discrepancy between data for the proton form factor ratio GEp/GMp obtained from cross section and polarization measurements. It was assumed that the two photon exchange contribution might be responsible for difference of GEp/GMp ratio obtained by Rosenbluth separation method and recoil polarization technique. The kinematical dependence of polarization transfer observables in elastic electron-proton scattering at Q2 = 2.5 (GeV/c)2 have been used in search of effects of 2[gamma] contribution. For a wide range of values of the virtual photon polarization [Sigma] ([Sigma] = 0.15, 0.63, and 0.77), the proton form factor ratio and longitudinal polarization transfer component were measured with statistical uncertainties of ±0.01 and ±0.005, respectively. Our data provide significant constraints on models of nucleon structure.
A Measurement of the Two-photon Exchange Effect in Elastic Electron-proton Scattering with OLYMPUS
Author: Rebecca Lynn RussellPublisher:
ISBN:
Category :
Languages : en
Pages : 190
Book Description
Elastic electron-proton scattering has long been the tool of choice for the study of the proton form factors, GE(Q 2 ) and GM(Q2 ), which describe the electric and magnetic distributions of the proton as a function of momentum transfer. Recent experiments, measuring the form factors from polarization observables in polarized elastic electron-proton scattering, have found values of the ratio GE(Q2 )/GM(Q2) at high Q2 that contradict the results from unpolarized measurements. A proposed explanation for this discrepancy is the unaccounted two-photon exchange radiative correction, which could affect the unpolarized measurements. As this effect is currently not possible to calculate in a model-independent way, the OLYMPUS experiment was designed to make a direct measurement of it by measuring the elastic positron-proton to electron-proton scattering cross section ratio. The experiment was run in 2012 at DESY using the BLAST spectrometer and the DORIS positron and electron beams at 2 GeV incident on a gaseous hydrogen target. To analyze the data, a careful reconstruction of the scattering events, detailed simulation of the experimental setup, and full radiative corrections to the measured cross sections were performed. Preliminary results for the experiment show a statistically significant two-photon exchange effect, increasing over the measurement range of 0.6 GeV2
Nuclear Science Abstracts
Author: Elastic K+-proton Scattering at 910 MeV/c
Author: Warner HirschRecoil Polarization Measurements of the Proton Electromagnetic Form Factor Ratio at High Momentum Transfer
Author: Publisher:
ISBN:
Category :
Languages : en
Pages :
Book Description
Electromagnetic form factors are fundamental properties of the nucleon that describe the effect of its internal quark structure on the cross section and spin observables in elastic lepton-nucleon scattering. Double-polarization experiments have become the preferred technique to measure the proton and neutron electric form factors at high momentum transfers. The recently completed GEp-III experiment at the Thomas Jefferson National Accelerator Facility used the recoil polarization method to extend the knowledge of the proton electromagnetic form factor ratio GpE/GpM to Q2 = 8.5 GeV2. In this paper we present the preliminary results of the experiment.
Recoil Polarization Measurements of the Proton Electromagnetic Form Factor Ratio to High Momentum Transfer
Author: Publisher:
ISBN:
Category :
Languages : en
Pages : 313
Book Description
The electromagnetic form factors of the nucleon characterize the effect of its internal structure on its response to an electromagnetic probe as studied in elastic electronnucleon scattering. These form factors are functions of the squared four-momentum transfer Q2 between the electron and the proton. The two main classes of observables of this reaction are the scattering cross section and polarization asymmetries, both of which are sensitive to the form factors in different ways. When considering large f momentum transfers, double-polarization observables offer superior sensitivity to the electric form factor. This thesis reports the results of a new measurement of the ratio of the electric and magnetic form factors of the proton at high momentum transfer using the recoil polarization technique. A polarized electron beam was scattered from a liquid hydrogen target, transferring polarization to the recoiling protons. These protons were detected in a magnetic spectrometer which was used to reconstruct their kinematics, including their scattering angles and momenta, and the position of the interaction vertex. A proton polarimeter measured the polarization of the recoiling protons by measuring the azimuthal asymmetry in the angular distribution of protons scattered in CH2 analyzers. The scattered electron was detected in a large acceptance electromagnetic calorimeter in order to suppress inelastic backgrounds. The measured ratio of the transverse and longitudinal polarization components of the scattered proton is directly proportional to the ratio of form factors GpE=GpM. The measurements reported in this thesis took place at Q2 =5.2, 6.7, and 8.5 GeV2, and represent the most accurate measurements of GpE in this Q2 region to date.