0000000000170389
AUTHOR
H. Holvoet
showing 12 related works from this author
Real and Virtual Compton Scattering (experiments)
1999
This paper deals with Real and Virtual Compton Scattering off the proton at threshold and the way to deduce information about the nucleon polarizabilities.
The first Virtual Compton Scattering experiment at MAMI
1999
Abstract Virtual Compton scattering, i.e. the exclusive reaction γ ∗ p → γ′p′ with γ ∗ denoting a virtual photon, provides new insights on the internal structure of the proton. Below π 0 production threshold, this experiment measures the generalized polarizabilities of the proton as defined by Guichon et al [1], [2] and Drechsel et al [3]. These new electromagnetic observables, functions of Q 2 , enlarge the concept of electric (α0 and magnetic (β) polarizabilities in Real Compton Scattering ( Q 2 =0) [4]. The first VCS experiment [5] of this kind was measured at the three spectrometer facility at the Mainz Microtron MAMI for Q 2 =0.33 GeV 2 and we present in this paper the preliminary resu…
Virtual Compton Scattering and polarizabilities
1999
Abstract Virtual Compton Scattering (VCS) off the proton below pion threshold allows access to generalized polarizabilities of the proton. These observables measure the response of the nucleon to low energy electromagnetic field perturbations. This paper presents a comparison with Real Compton Scattering and also results for the first dedicated VCS experiment performed at the Mainz Microtron MAMI with high resolution spectrometers at Q2 = 0.33 GeV2.
First Measurement of the Gerasimov-Drell-Hearn Sum Rule forH1from 0.7 to 1.8 GeV at ELSA
2003
To verify the fundamental Gerasimov-Drell-Hearn (GDH) sum rule for the first time experimentally, we measured the helicity dependent total photoabsorption cross section with circularly polarized real photons and longitudinally polarized nucleons in the photon energy range 0.68-1.82 GeV with the tagged photon facility at ELSA. The experiment was carried out with a 4pi detection system, a circularly polarized tagged photon beam, and a frozen spin polarized proton target. The contribution to the GDH sum rule in this photon energy range is [49.9+/-2.4(stat)+/-2.2(syst)] mub.
Measurement of Helicity-Dependent Photoabsorption Cross Sections on the Neutron from 815 to 1825 MeV
2005
Helicity-dependent total photoabsorption cross sections on the deuteron have been measured for the first time at ELSA (Bonn) in the photon energy range from 815 to 1825 MeV. Circularly polarized tagged photons impinging on a longitudinally polarized LiD target have been used together with a highly efficient 4pi detector system. The data around 1 GeV are not compatible with predictions from existing multipole analyses. From the measured energy range an experimental contribution to the GDH integral on the neutron of [33.9 +/- 5.5(stat) +/- 4.5(syst)] microb is extracted.
Virtual Compton Scattering at MAMI γ*p→ γ1p1
1999
The virtual Compton scattering (VCS) is the electron scattering on a proton which radiates a real photon before being detected. The new observables, called Generalized Polarizabilities (GP), extracted from this VCS at threshold can be understood as the deformation of the charge and current distributions of the proton [1]. These GP are functions of the mass of the virtual photon Q2. In real Compton scattering (Q2 = 0), some polarizabilities of the nucleon are already measured [2]. With the VCS, we will generalize these observables by measuring them at different values of Q2.
Measurement of the Gerasimov-Drell-Hearn Integrand forH2from 200 to 800 MeV
2006
A measurement of the helicity dependence of the total inclusive photoabsorption cross section on the deuteron was carried out at MAMI (Mainz) in the energy range $200l{E}_{\ensuremath{\gamma}}l800\text{ }\text{ }\mathrm{MeV}$. The experiment used a $4\ensuremath{\pi}$ detection system, a circularly polarized tagged photon beam and a frozen-spin target which provided longitudinally polarized deuterons. The contribution to the Gerasimov-Drell-Hearn sum rule for the deuteron determined from the data is $407\ifmmode\pm\else\textpm\fi{}20(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}24(\mathrm{syst})\text{ }\text{ }\ensuremath{\mu}\mathrm{b}$ for $200l{E}_{\ensuremath{\gamma}}l800\text{ }\text{ }\m…
The first dedicated Virtual Compton Scattering experiment at MAMI
1999
We measured the absolute cross sections for photon electro-production off the proton, ep to ep gamma , with the high resolution spectrometers at MAMI at momentum transfer q=600 MeV/c and photon polarization epsilon =0.62. We covered the momentum range for the outgoing real photon q'=33/111 MeV/c. From the extracted virtual Compton scattering amplitude we deduce values for two structure functions related to the generalized polarizabilities of the proton.
Virtual compton scattering under π0 threshold at Q2=0.33 GeV2. Preliminary results
1999
We have measured the absolute unpolarized cross sections for photon electro-production off the proton ep → epγ with the Three-Spectrometer-Setup at MAMI at a momentum transfer q=600 MeV/c and a virtual photon polarization ɛ=0.62. The momentum q ′ of the outgoing real photon range from 33 to 111 MeV/c. We extracted two combinations of the recently introduced generalized polarizabilities [1,2].
Helicity Dependence ofγp→Nπbelow 450 MeV and Contribution to the Gerasimov-Drell-Hearn Sum Rule
2000
The helicity dependence of the single pion photoproduction on the proton has been measured in the energy range from 200 to 450 MeV for the first time. The experiment, performed at the Mainz microtron MAMI, used a 4pi-detector system, a circularly polarized, tagged photon beam, and a frozen-spin target. The data obtained provide new information for multipole analyses of pion photoproduction and determine the main contributions to the Gerasimov-Drell-Hearn sum rule and the forward spin polarizability gamma(0).
Experimental Check of the Gerasimov-Drell-Hearn Sum Rule for H1
2004
For the first time we checked the fundamental Gerasimov-Drell-Hearn (GDH) sum rule for the proton experimentally in the photon energy range from 0.2-2.9 GeV with the tagged photon facilities at MAMI (Mainz) and ELSA (Bonn). New data of the doubly polarized total cross section difference are presented in the energy range from 1.6 to 2.9 GeV. The contribution to the GDH integral from 0.2-2.9 GeV yields [254+/-5(stat)+/-12(syst)] microb with negative contributions in the Regge regime at photon energies above 2.1 GeV. This trend supports the validity of the GDH sum rule.
"Table 1" of "Virtual Compton scattering under pi0 threshold at Q**2 = 0.33-GeV**2: Preliminary results."
1999
No description provided.