49 research outputs found
Strangeness Form Factors of the Proton in the Chiral Quark Model
The chiral quark model describes the strangeness components of the light
quarks as fluctuations into strange mesons and quarks. The single strange
pseudoscalar and vector meson loop fluctuations of the constituent - and
-quarks give rise to only very small strangeness form factors for the
proton. This result is in line with recent experimental results, given their
wide uncertainty range.Comment: 15 pages RevTeX, 6 figures (PS
The Cryogenic Target for the G Experiment at Jefferson Lab
A cryogenic horizontal single loop target has been designed, built, tested
and operated for the G experiment in Hall C at Jefferson Lab. The target
cell is 20 cm long, the loop volume is 6.5 l and the target operates with the
cryogenic pump fully immersed in the fluid. The target has been designed to
operate at 30 Hz rotational pump speed with either liquid hydrogen or liquid
deuterium. The high power heat exchanger is able to remove 1000 W of heat from
the liquid hydrogen, while the nominal electron beam with current of 40 A
and energy of 3 GeV deposits about 320 W of heat into the liquid. The increase
in the systematic uncertainty due to the liquid hydrogen target is negligible
on the scale of a parity violation experiment. The global normalized yield
reduction for 40 A beam is about 1.5 % and the target density fluctuations
contribute less than 238 ppm (parts per million) to the total asymmetry width,
typically about 1200 ppm, in a Q bin.Comment: 27 pages, 14 figure
Relaxation of Spin Polarized He in Mixtures of He and He Below the He Lambda Point
We report the first study of the depolarization behavior of spin polarized
3He in a mixture of 3He-4He at a temperature below the 4He Lambda point in a
deuterated TetraPhenyl Butadiene-doped deuterated PolyStyrene (dTPB-dPS) coated
acrylic cell. In our experiment the measured 3He relaxation time is due to the
convolution of the 3He longitudinal relaxation time, T1, and the diffusion time
constant of 3He in superfluid 4He since depolarization takes place on the
walls. We have obtained a 3He relaxation time ~3000 seconds at a temperature
around 1.9K. We have shown that it's possible to achieve values of wall
depolarization probability on the order of (1-2)x10^-7 for polarized 3He in the
superfluid 4He from a dTPB-dPS coated acrylic surface.Comment: The Model used to interpret the data has been change
Strange nucleon form factors in the perturbative chiral quark model
We apply the perturbative chiral quark model at one loop to calculate the
strange form factors of the nucleon. A detailed numerical analysis of the
strange magnetic moments and radii of the nucleon, and also the momentum
dependence of the form factors is presented.Comment: 18 pages, 6 figure
The Strangeness Magnetic Moment of the Proton in the Chiral Quark Model
The strangeness magnetic moment of the proton is shown to be small in the
chiral quark model. The dominant loop contribution is due to kaons. The K^*
loop contributions are proportional to the difference between the strange and
light constituent quark masses or and therefore small. The loop
fluctuations that involve radiative transitions between K^* mesons and kaons
are small, when the cut-off scale in the loops is taken to be close to the
chiral symmetry restoration scale. The net loop amplitude contribution to the
strangeness magnetic moment of the proton is about -0.05, which falls within
the uncertainty range of the experimental value.Comment: 14 pages, 3 figures; Figs. 1(a) and (b) interchanged, one harmless
typo correcte
Transverse Beam Spin Asymmetries in Forward-Angle Elastic Electron-Proton Scattering
We have measured the beam-normal single-spin asymmetry in elastic scattering of transversely polarized 3 GeV electrons from unpolarized protons at Q^2=0.15, 0.25 (GeV/c)^2. The results are inconsistent with calculations solely using the elastic nucleon intermediate state and generally agree with calculations with significant inelastic hadronic intermediate state contributions. A_n provides a direct probe of the imaginary component of the 2γ exchange amplitude, the complete description of which is important in the interpretation of data from precision electron-scattering experiments
Strange form factors in the context of SAMPLE, HAPPEX, and A4 experiments
The strange properties of the nucleon are investigated within the framework
of the SU(3) chiral quark-soliton model assuming isospin symmetry and applying
the symmetry conserving SU(3) quantization. We present the form factors
, and the electric and magnetic strange form
factors incorporating pion and kaon asymptotics. The results
show a fairly good agreement with the recent experimental data from the SAMPLE
and HAPPEX collaborations. We also present predictions for future measurements
including the A4 experiment at MAMI (Mainz).Comment: 10 pages with four figures. RevTeX4 is used. Few lines are changed.
Accepted for publication in Phys.Rev.
Parity-violating Electron Deuteron Scattering and the Proton's Neutral Weak Axial Vector Form Factor
We report on a new measurement of the parity-violating asymmetry in
quasielastic electron scattering from the deuteron at backward angles at Q2=
0.038 (GeV/c)2. This quantity provides a determination of the neutral weak
axial vector form factor of the nucleon, which can potentially receive large
electroweak corrections. The measured asymmetry A=-3.51 +/- 0.57(stat) +/-
0.58(sys)ppm is consistent with theoretical predictions. We also report on
updated results of the previous experiment at Q2=0.091 (GeV/c)2, which are also
consistent with theoretical predictions.Comment: 4 pages, 2 figures, submitted to Phys. Rev. Let
Parity-violating Electron Deuteron Scattering and the Proton's Neutral Weak Axial Vector Form Factor
We report on a new measurement of the parity-violating asymmetry in
quasielastic electron scattering from the deuteron at backward angles at Q2=
0.038 (GeV/c)2. This quantity provides a determination of the neutral weak
axial vector form factor of the nucleon, which can potentially receive large
electroweak corrections. The measured asymmetry A=-3.51 +/- 0.57(stat) +/-
0.58(sys)ppm is consistent with theoretical predictions. We also report on
updated results of the previous experiment at Q2=0.091 (GeV/c)2, which are also
consistent with theoretical predictions.Comment: 4 pages, 2 figures, submitted to Phys. Rev. Let
Transverse Beam Spin Asymmetries in Forward-Angle Elastic Electron-Proton Scattering
We have measured the beam-normal single-spin asymmetry in elastic scattering
of transversely-polarized 3 GeV electrons from unpolarized protons at Q^2 =
0.15, 0.25 (GeV/c)^2. The results are inconsistent with calculations solely
using the elastic nucleon intermediate state, and generally agree with
calculations with significant inelastic hadronic intermediate state
contributions. A_n provides a direct probe of the imaginary component of the
2-gamma exchange amplitude, the complete description of which is important in
the interpretation of data from precision electron-scattering experiments.Comment: 5 pages, 3 figures, submitted to Physical Review Letters; shortened
to meet PRL length limit, clarified some text after referee's comment