We have measured the spin structure functions
g
2
p
and
g
2
d
and the virtual photon asymmetries
A
2
p
and
A
2
d
over the kinematic range 0.02≤
x≤0.8 and 1.0≤
Q
2≤30 (GeV/c)
2 by scattering 38.8 GeV ...longitudinally polarized electrons from transversely polarized NH
3 and
6LiD targets. The absolute value of
A
2 is significantly smaller than the
R
positivity limit over the measured range, while
g
2 is consistent with the twist-2 Wandzura-Wilczek calculation. We obtain results for the twist-3 reduced matrix elements
d
2
p
,
d
2
d
and
d
2
n
. The Burkhardt-Cottingham sum rule integral
∫
g
2(x)dx
is reported for the range 0.02≤
x≤0.8.
Gram-negative bacteria can antagonize neighboring microbes using a type VI secretion system (T6SS) to deliver toxins that target different essential cellular features. Despite the conserved nature of ...these targets, T6SS potency can vary across recipient species. To understand the functional basis of intrinsic T6SS susceptibility, we screened for essential Escherichia coli (Eco) genes that affect its survival when antagonized by a cell wall-degrading T6SS toxin from Pseudomonas aeruginosa, Tae1. We revealed genes associated with both the cell wall and a separate layer of the cell envelope, lipopolysaccharide, that modulate Tae1 toxicity in vivo. Disruption of genes in early lipopolysaccharide biosynthesis provided Eco with novel resistance to Tae1, despite significant cell wall degradation. These data suggest that Tae1 toxicity is determined not only by direct substrate damage, but also by indirect cell envelope homeostasis activities. We also found that Tae1-resistant Eco exhibited reduced cell wall synthesis and overall slowed growth, suggesting that reactive cell envelope maintenance pathways could promote, not prevent, self-lysis. Together, our study reveals the complex functional underpinnings of susceptibility to Tae1 and T6SS which regulate the impact of toxin-substrate interactions in vivo.
We have analyzed the properties of a noncollinear magnetic phase obtained in the mean-field analysis of the model of two coupled Heisenberg subsystems. The domain of its existence and stability is ...narrow and depends on the ratio between the averaged over nearest neighbours microscopic exchange parameters.
The 2H(e,ep)n cross section was measured in Hall A of the Thomas Jefferson National Accelerator Facility near the top of the quasielastic peak (xBj = 0.964) at a four-momentum transfer squared, Q2 = ...0.665 (GeV/c)2 (= 0.368GeV, W = 2.057GeV), and for recoil momenta up to 550MeV/c. The measured cross section deviates by 1-2 from a state-of-the-art calculation at low recoil momenta. At high recoil momenta the cross section is well described by the same calculation; however, in this region, final-state interactions and interaction currents are predicted to be large, and alternative choices of nucleon-nucleon potential and nucleon current operator may result in significant spread in the calculations.
The 2H(e,e(')p)n cross section was measured in Hall A of the Thomas Jefferson National Accelerator Facility near the top of the quasielastic peak (x(Bj)=0.964) at a four-momentum transfer squared, ...Q(2)=0.665 (GeV/c) (2) (omega=0.368 GeV, W=2.057 GeV), and for recoil momenta up to 550 MeV/c. The measured cross section deviates by 1-2sigma from a state-of-the-art calculation at low recoil momenta. At high recoil momenta the cross section is well described by the same calculation; however, in this region, final-state interactions and interaction currents are predicted to be large, and alternative choices of nucleon-nucleon potential and nucleon current operator may result in significant spread in the calculations.
Light vector mesons in the nuclear medium Wood, M. H.; Mosel, U.; Muehlich, P. ...
Physical review. C, Nuclear physics,
07/2008, Letnik:
78, Številka:
1
Journal Article
Recenzirano
Odprti dostop
The light vector mesons ({rho},{omega}, and {phi}) were produced in deuterium, carbon, titanium, and iron targets in a search for possible in-medium modifications to the properties of the {rho} meson ...at normal nuclear densities and zero temperature. The vector mesons were detected with the CEBAF Large Acceptance Spectrometer (CLAS) via their decays to e{sup +}e{sup -}. The rare leptonic decay was chosen to reduce final-state interactions. A combinatorial background was subtracted from the invariant mass spectra using a well-established event-mixing technique. The {rho}-meson mass spectrum was extracted after the {omega} and {phi} signals were removed in a nearly model-independent way. Comparisons were made between the {rho} mass spectra from the heavy targets (A>2) with the mass spectrum extracted from the deuterium target. With respect to the {rho}-meson mass, we obtain a small shift compatible with zero. Also, we measure widths consistent with standard nuclear many-body effects such as collisional broadening and Fermi motion.
We present measurements of the ratio of the proton elastic electromagnetic form factors, {mu}{sub p}G{sub Ep}/G{sub Mp}. The Jefferson Lab Hall A Focal Plane Polarimeter was used to determine the ...longitudinal and transverse components of the recoil proton polarization in ep elastic scattering; the ratio of these polarization components is proportional to the ratio of the two form factors. These data reproduce the observation of Jones Phys. Rev. Lett. 84, 1398 (2000), that the form factor ratio decreases significantly from unity above Q{sup 2}=1 GeV{sup 2}.
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