The results of scientific cooperation of NSC KIPT and TJNAF (USA)

As a part of the spin-physics program at the Jefferson Laboratory (TJNAF), a Møller polarimeter has been developed to measure the polarization of electron beam of energies between 0.8 and 6.0 GeV. Since April 1998, regular measurements with the polarimeter are made. Kharkov scientists participated in 14 from 17 experiments, which were done in the Hall A. The most interesting published results are presented

Electron beam Møller polarimeter at hall A, JLab

As a part of the spin-physics program at the Thomas Jefferson National Accelerator Facility (JLab), a Møller polarimeter has been developed to measure the polarization of electron beam of energies between 0.8 and 6.0 GeV. A unique design of this polarimeter was developed. A set of three quadrupole magnets provides an angular selection of the Møller electron pairs and a dipole magnet provides energy analysis. The test procedure and commissioning of the polarimeter are presented. The results of beam polarization measurements in long-term physical experiments, the correlation for the three-beam accelerator mode and other effects are discussed

First measurement of direct f0(980)f_0(980) photoproduction on the proton

We report on the results of the first measurement of exclusive $f_0(980)$ meson photoproduction on protons for $E_\gamma=3.0 - 3.8$ GeV and $-t = 0.4-1.0$ GeV$^2$. Data were collected with the CLAS detector at the Thomas Jefferson National Accelerator Facility. The resonance was detected via its decay in the $\pi^+ \pi^-$ channel by performing a partial wave analysis of the reaction $\gamma p \to p \pi^+ \pi^-$. Clear evidence of the $f_0(980)$ meson was found in the interference between $P$ and $S$ waves at $M_{\pi^+ \pi^-}\sim 1$ GeV. The $S$-wave differential cross section integrated in the mass range of the $f_0(980)$ was found to be a factor of 50 smaller than the cross section for the $\rho$ meson. This is the first time the $f_0(980)$ meson has been measured in a photoproduction experiment

Plane-wave impulse approximation extraction of the neutron magnetic form factor from quasielastic 3He(e,e′) at Q2=0.3 to 0.6 (GeV/c)2

A high precision measurement of the transverse spin-dependent asymmetry AT′ in 3He(e,e′) quasielastic scattering was performed in Hall A at Jefferson Lab at values of the squared four-momentum transfer, Q2, between 0.1 and 0.6 (GeV/c)2. AT′ is sensitive to the neutron magnetic form factor, GMn. Values of GMn at Q2=0.1 and 0.2 (GeV/c)2, extracted using Faddeev calculations, were reported previously. Here, we report the extraction of GMn for the remaining Q2 values in the range from 0.3 to 0.6 (GeV/c)2 using a plane-wave impulse approximation calculation. The results are in good agreement with recent precision data from experiments using a deuterium target

Plane-wave impulse approximation extraction of the neutron magnetic form factor from quasielastic 3He(e,e′) at Q2=0.3 to 0.6 (GeV/c)2

A high precision measurement of the transverse spin-dependent asymmetry AT′ in 3He(e,e′) quasielastic scattering was performed in Hall A at Jefferson Lab at values of the squared four-momentum transfer, Q2, between 0.1 and 0.6 (GeV/c)2. AT′ is sensitive to the neutron magnetic form factor, GMn. Values of GMn at Q2=0.1 and 0.2 (GeV/c)2, extracted using Faddeev calculations, were reported previously. Here, we report the extraction of GMn for the remaining Q2 values in the range from 0.3 to 0.6 (GeV/c)2 using a plane-wave impulse approximation calculation. The results are in good agreement with recent precision data from experiments using a deuterium target

Extraction of the Neutron Magnetic Form Factor from Quasi-Elastic 3He(pol)(e(pol),e') at Q^2 = 0.1 - 0.6 (GeV/c)^2

We have measured the spin-dependent transverse asymmetry, A_T', in quasi-elastic inclusive electron scattering from polarized 3He with high precision at Q^2 = 0.1 to 0.6 (GeV/c)^2. The neutron magnetic form factor, GMn, was extracted at Q^2 = 0.1 and 0.2 (GeV/c)^2 using a non-relativistic Faddeev calculation that includes both final-state interactions (FSI) and meson-exchange currents (MEC). In addition, GMn was extracted at Q^2 = 0.3 to 0.6 (GeV/c)^2 using a Plane Wave Impulse Approximation calculation. The accuracy of the modeling of FSI and MEC effects was tested and confirmed with a precision measurement of the spin-dependent asymmetry in the breakup threshold region of the 3He(pol)(e(pol),e') reaction. The total relative uncertainty of the extracted GMn data is approximately 3%. Close agreement was found with other recent high-precision GMn data in this Q^2 range.Comment: Archival paper, 17 pages, 10 figures, 5 tables, submitted to Physical Review C. v2: shortened considerably, updated comparison to theor

Møller polarimetry with atomic hydrogen targets

A novel proposal of using polarized atomic hydrogen gas, stored in an ultra-cold magnetic trap, as the target for electron beam polarimetry based on Møller scattering is discussed. Such a target of practically 100% polarized electrons could provide a superb systematic accuracy of about 0.5% for beam polarization measurements. Feasibility studies for the CEBAF electron beam have been performed.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/45814/1/10050_2005_Article_394.pd

The next generation HAPPEX experiments

A new generation of parity violating electron scattering experiments began running in Summer 2004 at the Thomas Jefferson National Accelerator Facility. HAPPEX-H will measure the parity violating asymmetry in polarized electron scattering from protons at Q 2 = 0.11 (GeV/c)2. This asymmetry is sensitive to a linear combination of the strange electric and magnetic form factors of the proton. HAPPEX-He will measure the parity violating asymmetry in polarized electron scattering from a 4He target at the same value of Q 2, using the same spectrometers and similar detectors, accessing the strange electric form factor cleanly. PREX will use parity violating electron scattering to determine the neutron radius of the 206Pb nucleus. PACS: 13.60.Fz Elastic and Compton scattering – 11.30.Er Charge conjugation, parity, time reversal, and other discrete symmetries – 13.40.Gp Electromagnetic form factors – 14.20.Dh Protons and neutrons – 24.80.+y Nuclear tests of fundamental interactions and symmetries – 21.10.Gv Mass and neutron distributions – 25.30.Bf Elastic electron scatterin