384 research outputs found
Spin Sum Rules and the Strong Coupling Constant at large distance
We present recent results on the Bjorken and the generalized forward spin
polarizability sum rules from Jefferson Lab Hall A and CLAS experiments,
focusing on the low part of the measurements. We then discuss the
comparison of these results with Chiral Perturbation theory calculations. In
the second part of this paper, we show how the Bjorken sum rule with its
connection to the Gerasimov-Drell-Hearn sum, allows us to conveniently define
an effective coupling for the strong force at all distances.Comment: Contribution to proceedings for the Workshop on Spin Structure at
Long Distance (Newport News, March 2009
3He Spin-Dependent Cross Sections and Sum Rules
We present a measurement of the spin-dependent cross sections for the 3→He(→e,e′)X reaction in the quasielastic and resonance regions at a four-momentum transfer 0.1≤Q2≤0.9  GeV2. The spin-structure functions have been extracted and used to evaluate the nuclear Burkhardt-Cottingham and extended Gerasimov-Drell-Hearn sum rules for the first time. The data are also compared to an impulse approximation calculation and an exact three-body Faddeev calculation in the quasielastic region
Electron microscopic studies on the palpi of Cybister fimbriolatus fimbriolatus (Say)
The maxillary palpi of the predaceous diving beetle Cybister fimbriolatus fimbriolatus Say were observed by transmission and scanning electron microscopy. Scanning electron microscopy shows at least two types of sensilla at the tip of palp, which are referred to as “circumvallate and naked sensilla”. The former are innervated with outer segments of distal processes of sensory cells, but the latter are provided only with chitin and cuticular substances.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47659/1/441_2004_Article_BF00330709.pd
Moments of the Neutron \u3cem\u3eg\u3c/em\u3e\u3csub\u3e2\u3c/sub\u3e Structure Function at Intermediate \u3cem\u3eQ\u3c/em\u3e\u3csup\u3e2\u3c/sup\u3e
We present new experimental results for the 3He spin structure function g2 in the resonance region at Q2 values between 1.2 and 3.0(GeV/c)2. Spin dependent moments of the neutron were extracted. Our main result, the inelastic contribution to the neutron d2 matrix element, was found to be small at ⟨Q2⟩=2.4(GeV/c)2 and in agreement with the lattice QCD calculation. The Burkhardt-Cottingham sum rule for 3He and the neutron was tested with the measured data and using the Wandzura-Wilczek relation for the low x unmeasured region
Quark-Hadron Duality in Neutron (3He) Spin Structure
We present experimental results of the first high-precision test of
quark-hadron duality in the spin-structure function g_1 of the neutron and
He using a polarized 3He target in the four-momentum-transfer-squared range
from 0.7 to 4.0 (GeV/c)^2. Global duality is observed for the spin-structure
function g_1 down to at least Q^2 = 1.8 (GeV/c)^2 in both targets. We have also
formed the photon-nucleon asymmetry A_1 in the resonance region for 3He and
found no strong Q^2-dependence above 2.2 (GeV/c)^2.Comment: 13 pages, 3 figure
Experimental determination of the evolution of the Bjorken integral at low Q^2
We extract the Bjorken integral Gamma^{p-n}_1 in the range 0.17 < Q^2 < 1.10
GeV^2 from inclusive scattering of polarized electrons by polarized protons,
deuterons and 3He, for the region in which the integral is dominated by nucleon
resonances. These data bridge the domains of the hadronic and partonic
descriptions of the nucleon. In combination with earlier measurements at higher
Q^2, we extract the non-singlet twist-4 matrix element f_2.Comment: Quoted world data updated. Minor change in some results, Minor
rephrasin
Moments of the neutron structure function at intermediate
We present new experimental results of the He spin structure function
in the resonance region at values between 1.2 and 3.0 (GeV/c).
Spin dependent moments of the neutron were then extracted. Our main result, the
resonance contribution to the neutron matrix element, was found to be
small at =2.4 (GeV/c) and in agreement with the Lattice QCD
calculation. The Burkhardt-Cottingham sum rule for He and the neutron was
tested with the measured data and using the Wandzura-Wilczek relation for the
low unmeasured region. A small deviation was observed at values
between 0.5 and 1.2 (GeV/c) for the neutron
Proton Spin Structure in the Resonance Region
We have examined the spin structure of the proton in the region of the
nucleon resonances (1.085 GeV < W < 1.910 GeV) at an average four momentum
transfer of Q^2 = 1.3 GeV^2. Using the Jefferson Lab polarized electron beam, a
spectrometer, and a polarized solid target, we measured the asymmetries
A_parallel and A_perp to high precision, and extracted the asymmetries A_1 and
A_2, and the spin structure functions g_1 and g_2. We found a notably non-zero
A_perp, significant contributions from higher-twist effects, and only weak
support for polarized quark--hadron duality.Comment: 6 pages, 4 figures, REVTeX4, similar to PRL submission, plots
colorized and appenix added, v3: minor edit, matches PR
Probing the high momentum component of the deuteron at high Q^2
The d(e,e'p) cross section at a momentum transfer of 3.5 (GeV/c)^2 was
measured over a kinematical range that made it possible to study this reaction
for a set of fixed missing momenta as a function of the neutron recoil angle
theta_nq and to extract missing momentum distributions for fixed values of
theta_nq up to 0.55 GeV/c. In the region of 35 (deg) <= theta_nq <= 45 (deg)
recent calculations, which predict that final state interactions are small,
agree reasonably well with the experimental data. Therefore these experimental
reduced cross sections provide direct access to the high momentum component of
the deuteron momentum distribution in exclusive deuteron
electro-disintegration.Comment: 5 pages, 2 figure
- …