265 research outputs found
Variation of endophytic cork oakâassociated fungal communities in relation to plant health and water stress
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/86852/1/j.1439-0329.2010.00652.x.pd
Measurements of the \gamma * p --> \Delta(1232) reaction at low Q2
We report new p measurements in the
resonance at the low momentum transfer region utilizing the
magnetic spectrometers of the A1 Collaboration at MAMI. The mesonic cloud
dynamics are predicted to be dominant and appreciably changing in this region
while the momentum transfer is sufficiently low to be able to test chiral
effective calculations. The results disagree with predictions of constituent
quark models and are in reasonable agreement with dynamical calculations with
pion cloud effects, chiral effective field theory and lattice calculations. The
reported measurements suggest that improvement is required to the theoretical
calculations and provide valuable input that will allow their refinements
The f_LT Response Function of D(e,e'p)n at Q^2=0.33(GeV/c)^2
The interference response function f_LT (R_LT) of the D(e,e'p)n reaction has
been determined at squared four-momentum transfer Q^2 = 0.33 (GeV/c)^2 and for
missing momenta up to p_miss= 0.29 (GeV/c). The results have been compared to
calculations that reproduce f_LT quite well but overestimate the cross sections
by 10 - 20% for missing momenta between 0.1 (GeV/c) and 0.2 (GeV/c) .Comment: 12 Pages, 10 figure
Measurements of the Generalized Electric and Magnetic Polarizabilities of the Proton at Low Q2 Using the VCS Reaction
The mean square polarizability radii of the proton have been measured for the
first time in a virtual Compton scattering experiment performed at the
MIT-Bates out-of-plane scattering facility. Response functions and
polarizabilities obtained from a dispersion analysis of the data at Q2=0.06
GeV2/c2 are in agreement with O(p3) heavy baryon chiral perturbation theory.
The data support the dominance of mesonic effects in the polarizabilities, and
the increase of beta with increasing Q2 is evidence for the cancellation of
long-range diamagnetism by short-range paramagnetism from the pion cloud
Final State Interaction Effects in pol 3He(pol e,e'p)
Asymmetries in quasi-elastic pol 3He(pol e,e'p) have been measured at a
momentum transfer of 0.67 (GeV/c)^2 and are compared to a calculation which
takes into account relativistic kinematics in the final state and a
relativistic one-body current operator. With an exact solution of the Faddeev
equation for the 3He-ground state and an approximate treatment of final state
interactions in the continuum good agreement is found with the experimental
data.Comment: 11 pages, 6 figures, submitted to Phys. Lett. B, revised version,
sensitivity study to relativity and NN-potential adde
Measurement of the proton electric to magnetic form factor ratio from \vec ^1H(\vec e, e'p)
We report the first precision measurement of the proton electric to magnetic
form factor ratio from spin-dependent elastic scattering of longitudinally
polarized electrons from a polarized hydrogen internal gas target. The
measurement was performed at the MIT-Bates South Hall Ring over a range of
four-momentum transfer squared from 0.15 to 0.65 (GeV/c).
Significantly improved results on the proton electric and magnetic form factors
are obtained in combination with previous cross-section data on elastic
electron-proton scattering in the same region.Comment: 4 pages, 2 figures, submitted to PR
Deeply Virtual Compton Scattering off the neutron
The present experiment exploits the interference between the Deeply Virtual
Compton Scattering (DVCS) and the Bethe-Heitler processes to extract the
imaginary part of DVCS amplitudes on the neutron and on the deuteron from the
helicity-dependent D cross section measured at =1.9
GeV and =0.36. We extract a linear combination of generalized parton
distributions (GPDs) particularly sensitive to , the least constrained
GPD. A model dependent constraint on the contribution of the up and down quarks
to the nucleon spin is deduced.Comment: Published in Phys. Rev. Let
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