78 research outputs found
Measurement of the Neutron Radius of 208Pb Through Parity-Violation in Electron Scattering
We report the first measurement of the parity-violating asymmetry A_PV in the
elastic scattering of polarized electrons from 208Pb. A_PV is sensitive to the
radius of the neutron distribution (Rn). The result A_PV = 0.656 \pm 0.060
(stat) \pm 0.014 (syst) ppm corresponds to a difference between the radii of
the neutron and proton distributions Rn - Rp = 0.33 +0.16 -0.18 fm and provides
the first electroweak observation of the neutron skin which is expected in a
heavy, neutron-rich nucleus.Comment: 6 pages, 1 figur
Exclusive Neutral Pion Electroproduction in the Deeply Virtual Regime
We present measurements of the ep->ep pi^0 cross section extracted at two
values of four-momentum transfer Q^2=1.9 GeV^2 and Q^2=2.3 GeV^2 at Jefferson
Lab Hall A. The kinematic range allows to study the evolution of the extracted
hadronic tensor as a function of Q^2 and W. Results will be confronted with
Regge inspired calculations and GPD predictions. An intepretation of our data
within the framework of semi-inclusive deep inelastic scattering has also been
attempted
Identification of Tsetse (Glossina spp.) using matrix-assisted laser desorption/ionisation time of flight mass spectrometry
Glossina (G.) spp. (Diptera: Glossinidae), known as tsetse flies, are vectors
of African trypanosomes that cause sleeping sickness in humans and nagana in
domestic livestock. Knowledge on tsetse distribution and accurate species
identification help identify potential vector intervention sites.
Morphological species identification of tsetse is challenging and sometimes
not accurate. The matrix-assisted laser desorption/ionisation time of flight
mass spectrometry (MALDI TOF MS) technique, already standardised for microbial
identification, could become a standard method for tsetse fly diagnostics.
Therefore, a unique spectra reference database was created for five lab-reared
species of riverine-, savannah- and forest- type tsetse flies and incorporated
with the commercial Biotyper 3.0 database. The standard formic
acid/acetonitrile extraction of male and female whole insects and their body
parts (head, thorax, abdomen, wings and legs) was used to obtain the flies'
proteins. The computed composite correlation index and cluster analysis
revealed the suitability of any tsetse body part for a rapid taxonomical
identification. Phyloproteomic analysis revealed that the peak patterns of G.
brevipalpis differed greatly from the other tsetse. This outcome was
comparable to previous theories that they might be considered as a sister
group to other tsetse spp. Freshly extracted samples were found to be matched
at the species level. However, sex differentiation proved to be less reliable.
Similarly processed samples of the common house fly Musca domestica (Diptera:
Muscidae; strain: Lei) did not yield any match with the tsetse reference
database. The inclusion of additional strains of morphologically defined wild
caught flies of known origin and the availability of large-scale mass
spectrometry data could facilitate rapid tsetse species identification in the
futur
High Precision Measurement of the Proton Elastic Form Factor Ratio at low
We report a new, high-precision measurement of the proton elastic form factor
ratio \mu_p G_E/G_M for the four-momentum transfer squared Q^2 = 0.3-0.7
(GeV/c)^2. The measurement was performed at Jefferson Lab (JLab) in Hall A
using recoil polarimetry. With a total uncertainty of approximately 1%, the new
data clearly show that the deviation of the ratio \mu_p G_E/G_M from unity
observed in previous polarization measurements at high Q^2 continues down to
the lowest Q^2 value of this measurement. The updated global fit that includes
the new results yields an electric (magnetic) form factor roughly 2% smaller
(1% larger) than the previous global fit in this Q^2 range. We obtain new
extractions of the proton electric and magnetic radii, which are
^(1/2)=0.875+/-0.010 fm and ^(1/2)=0.867+/-0.020 fm. The charge
radius is consistent with other recent extractions based on the electron-proton
interaction, including the atomic hydrogen Lamb shift measurements, which
suggests a missing correction in the comparison of measurements of the proton
charge radius using electron probes and the recent extraction from the muonic
hydrogen Lamb shift.Comment: 12 pages, 3 figure
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