Constraints on the Nucleon Strange Form Factors at Q^2 ~ 0.1 GeV^2

We report the most precise measurement to date of a parity-violating asymmetry in elastic electron-proton scattering. The measurement was carried out with a beam energy of 3.03 GeV and a scattering angle =6 degrees, with the result A_PV = -1.14 +/- 0.24 (stat) +/- 0.06 (syst) parts per million. From this we extract, at Q^2 = 0.099 GeV^2, the strange form factor combination G_E^s + 0.080 G_M^s = 0.030 +/- 0.025 (stat) +/- 0.006 (syst) +/- 0.012 (FF) where the first two errors are experimental and the last error is due to the uncertainty in the neutron electromagnetic form factor. This result significantly improves current knowledge of G_E^s and G_M^s at Q^2 ~0.1 GeV^2. A consistent picture emerges when several measurements at about the same Q^2 value are combined: G_E^s is consistent with zero while G_M^s prefers positive values though G_E^s=G_M^s=0 is compatible with the data at 95% C.L.Comment: minor wording changes for clarity, updated references, dropped one figure to improve focu

Current assessment of the Red Rectangle band problem

In this paper we discuss our insights into several key problems in the identification of the Red Rectangle Bands (RRBs). We have combined three independent sets of observations in order to try to define the constraints guiding the bands. We provide a summary of the general behavior of the bands and review the evidence for a molecular origin of the bands. The extent, composition, and possible absorption effects of the bands are discussed. Comparison spectra of the strongest band obtained at three different spectral resolutions suggests that an intrinsic line width of individual rotational lines can be deduced. Spectroscopic models of several relatively simple molecules were examined in order to investigate where the current data are weak. Suggestions are made for future studies to enhance our understanding of these enigmatic bands

Plane-wave impulse approximation extraction of the neutron magnetic form factor from quasielastic 3He(e,e′) at Q2=0.3 to 0.6 (GeV/c)2

A high precision measurement of the transverse spin-dependent asymmetry AT′ in 3He(e,e′) quasielastic scattering was performed in Hall A at Jefferson Lab at values of the squared four-momentum transfer, Q2, between 0.1 and 0.6 (GeV/c)2. AT′ is sensitive to the neutron magnetic form factor, GMn. Values of GMn at Q2=0.1 and 0.2 (GeV/c)2, extracted using Faddeev calculations, were reported previously. Here, we report the extraction of GMn for the remaining Q2 values in the range from 0.3 to 0.6 (GeV/c)2 using a plane-wave impulse approximation calculation. The results are in good agreement with recent precision data from experiments using a deuterium target

Plane-wave impulse approximation extraction of the neutron magnetic form factor from quasielastic 3He(e,e′) at Q2=0.3 to 0.6 (GeV/c)2

A high precision measurement of the transverse spin-dependent asymmetry AT′ in 3He(e,e′) quasielastic scattering was performed in Hall A at Jefferson Lab at values of the squared four-momentum transfer, Q2, between 0.1 and 0.6 (GeV/c)2. AT′ is sensitive to the neutron magnetic form factor, GMn. Values of GMn at Q2=0.1 and 0.2 (GeV/c)2, extracted using Faddeev calculations, were reported previously. Here, we report the extraction of GMn for the remaining Q2 values in the range from 0.3 to 0.6 (GeV/c)2 using a plane-wave impulse approximation calculation. The results are in good agreement with recent precision data from experiments using a deuterium target

Extraction of the Neutron Magnetic Form Factor from Quasi-Elastic 3He(pol)(e(pol),e') at Q^2 = 0.1 - 0.6 (GeV/c)^2

We have measured the spin-dependent transverse asymmetry, A_T', in quasi-elastic inclusive electron scattering from polarized 3He with high precision at Q^2 = 0.1 to 0.6 (GeV/c)^2. The neutron magnetic form factor, GMn, was extracted at Q^2 = 0.1 and 0.2 (GeV/c)^2 using a non-relativistic Faddeev calculation that includes both final-state interactions (FSI) and meson-exchange currents (MEC). In addition, GMn was extracted at Q^2 = 0.3 to 0.6 (GeV/c)^2 using a Plane Wave Impulse Approximation calculation. The accuracy of the modeling of FSI and MEC effects was tested and confirmed with a precision measurement of the spin-dependent asymmetry in the breakup threshold region of the 3He(pol)(e(pol),e') reaction. The total relative uncertainty of the extracted GMn data is approximately 3%. Close agreement was found with other recent high-precision GMn data in this Q^2 range.Comment: Archival paper, 17 pages, 10 figures, 5 tables, submitted to Physical Review C. v2: shortened considerably, updated comparison to theor

Q

The Qweak experiment, which took data at Jefferson Lab in the period 2010 - 2012, will precisely determine the weak charge of the proton by measuring the parity-violating asymmetry in elastic e-p scattering at 1.1 GeV using a longitudinally polarized electron beam and a liquid hydrogen target at a low momentum transfer of Q2 = 0.025 (GeV/c)2. The weak charge of the proton is predicted by the Standard Model and any significant deviation would indicate physics beyond the Standard Model. The technical challenges and experimental apparatus for measuring the weak charge of the proton will be discussed, as well as the method of extracting the weak charge of the proton. The results from a small subset of the data, that has been published, will also be presented. Furthermore an update will be given of the current status of the data analysis

Measurement of the single-spin asymmetry A y 0 in quasi-elastic 3He↑(e,e′n) scattering at 0.4 < Q 2 < 1.0 GeV/c 2

No abstract available

Rotavirus group : a genotype circulation patterns across Kenya before and after nationwide vaccine introduction, 2010-2018

Background Kenya introduced the monovalent G1P [8] Rotarix® vaccine into the infant immunization schedule in July 2014. We examined trends in rotavirus group A (RVA) genotype distribution pre- (January 2010–June 2014) and post- (July 2014–December 2018) RVA vaccine introduction. Methods Stool samples were collected from children aged < 13 years from four surveillance sites across Kenya: Kilifi County Hospital, Tabitha Clinic Nairobi, Lwak Mission Hospital, and Siaya County Referral Hospital (children aged < 5 years only). Samples were screened for RVA using enzyme linked immunosorbent assay (ELISA) and VP7 and VP4 genes sequenced to infer genotypes. Results We genotyped 614 samples in pre-vaccine and 261 in post-vaccine introduction periods. During the pre-vaccine introduction period, the most frequent RVA genotypes were G1P [8] (45.8%), G8P [4] (15.8%), G9P [8] (13.2%), G2P [4] (7.0%) and G3P [6] (3.1%). In the post-vaccine introduction period, the most frequent genotypes were G1P [8] (52.1%), G2P [4] (20.7%) and G3P [8] (16.1%). Predominant genotypes varied by year and site in both pre and post-vaccine periods. Temporal genotype patterns showed an increase in prevalence of vaccine heterotypic genotypes, such as the commonly DS-1-like G2P [4] (7.0 to 20.7%, P < .001) and G3P [8] (1.3 to 16.1%, P < .001) genotypes in the post-vaccine introduction period. Additionally, we observed a decline in prevalence of genotypes G8P [4] (15.8 to 0.4%, P < .001) and G9P [8] (13.2 to 5.4%, P < .001) in the post-vaccine introduction period. Phylogenetic analysis of genotype G1P [8], revealed circulation of strains of lineages G1-I, G1-II and P [8]-1, P [8]-III and P [8]-IV. Considerable genetic diversity was observed between the pre and post-vaccine strains, evidenced by distinct clusters. Conclusion Genotype prevalence varied from before to after vaccine introduction. Such observations emphasize the need for long-term surveillance to monitor vaccine impact. These changes may represent natural secular variation or possible immuno-epidemiological changes arising from the introduction of the vaccine. Full genome sequencing could provide insights into post-vaccine evolutionary pressures and antigenic diversity

Dynamics of the 16^{16}O(e,e'p) cross section at high missing energies

We measured the cross section and response functions (R_L, R_T, and R_LT) for the 16O(e,e'p) reaction in quasielastic kinematics for missing energies 25 60 MeV and P_miss > 200 MeV/c, the cross section is relatively constant. Calculations which include contributions from pion exchange currents, isobar currents and short-range correlations account for the shape and the transversity but only for half of the magnitude of the measured cross section