We report the first observation of the parity-violating gamma-ray asymmetry A_{γ}^{np} in neutron-proton capture using polarized cold neutrons incident on a liquid parahydrogen target at the ...Spallation Neutron Source at Oak Ridge National Laboratory. A_{γ}^{np} isolates the ΔI=1, ^{3}S_{1}→^{3}P_{1} component of the weak nucleon-nucleon interaction, which is dominated by pion exchange and can be directly related to a single coupling constant in either the DDH meson exchange model or pionless effective field theory. We measured A_{γ}^{np}=-3.0±1.4(stat)±0.2(syst)×10^{-8}, which implies a DDH weak πNN coupling of h_{π}^{1}=2.6±1.2(stat)±0.2(syst)×10^{-7} and a pionless EFT constant of C^{^{3}S_{1}→^{3}P_{1}}/C_{0}=-7.4±3.5(stat)±0.5(syst)×10^{-11} MeV^{-1}. We describe the experiment, data analysis, systematic uncertainties, and implications of the result.
Status of the NPDGamma experiment Fry, J.; Alarcon, R.; Allen, R. ...
Hyperfine interactions,
11/2017, Volume:
238, Issue:
1
Journal Article
Peer reviewed
Open access
The NPDGamma experiment measures the parity-violating (PV) gamma asymmetry from polarized cold neutrons captured on protons at the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory ...(ORNL). The (PV) neutron spin asymmetry
A
γ
of photons from polarized cold neutron capture on protons is proportional to the Δ
I
=1 long range weak meson coupling
h
π
1
between nucleons in the hadronic weak interaction (HWI). Liquid para-hydrogen production data taking concluded in April 2014 and once the background aluminum asymmetry measurements are complete, the PV asymmetry
A
γ
can be extracted. Preliminary results of the analysis of
A
γ
are presented.
The CLAS12 drift chamber system Mestayer, M.D.; Adhikari, K.; Bennett, R.P. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
04/2020, Volume:
959, Issue:
C
Journal Article
Peer reviewed
Open access
The CEBAF Large Acceptance Spectrometer at 12 GeV (CLAS12) is located in Hall B, one of the experimental halls at Jefferson Lab. The forward part of CLAS12 is built around a superconducting toroidal ...magnet. The six coils of the toroid divide the detector azimuthally into six sectors. Each sector contains three multi-layer drift chambers for reconstructing the trajectories of charged particles originating from a fixed target.
Each of the 18 planar chambers has two “superlayers” of six layers each, with the wires in the two adjacent superlayers oriented at ±6° stereo angles. Each layer has 112 hexagonal cells spanning a range from about 5° to 40° in polar angle. The six-layer structure provides redundancy in track segment finding and good tracking efficiency even in the presence of some individual wire inefficiency. The design, construction, operation, and calibration methods are described, and estimates of the efficiency and resolution are presented from in-beam measurements.
In this work, the performance of inkjet-printed 6,13-bis(triisopropylsilylethynyl)pentacene (TIPS-pentacene)-based organic thin-film transistors (OTFTs) was studied under various printing conditions ...using photolithography-defined test structures. OTFTs were printed from TIPS-pentacene solutions with several concentrations, and the impact of printing temperature as well as the amount of material printed was studied. A hybrid approach that includes wells defined by a photolithography process and printed TIPS solution is demonstrated. The results show that the mobility of the printed OTFTs increases with increasing solution concentration, with a maximum mobility for concentration of 50 mg/mL and substrate temperature of 50°C. X-ray diffraction analysis showed the presence of the thin-film phase for all of the TIPS concentrations, with strong and sharp preferential orientation along the (001) direction without any disruption in molecular packing with increasing TIPS thickness. Optimized OTFTs fabricated with this technique show mobilities of 5 × 10
−2
cm
2
/V-s, threshold voltages (
V
T
) in the range of −5 V, and subthreshold slopes of approximately 0.5 V/dec. On–off current ratios up to 10
6
were also achieved.
► We monitored levels of organochlorine compounds in breast milk of Bangladeshi women from a non-endemic area. ► Compared to Europe and US, the concentrations of organochlorine pesticides in ...Bangladeshi mothers were 100 times higher. ► Low ratio between the pesticides (DDE and DDT) indicated ongoing or recent exposure. ► Low concentrations of polychlorinated compounds in breast milk from Bangladesh compared to Europe. ► Probable sources of organochlorine exposure include agricultural work or DDT-sprayed fish for vector control.
In low-income countries, the use of some organochlorine pesticides is still common in order to increase food production. Monitoring the chemical exposure is an important step in risk-reducing strategies. This is the first study to report concentrations of organochlorines in breast milk of women from Bangladesh where farming is the main income source.
Organochlorines such as p,p′-DDT, o,p′-DDT, p,p′-DDE, p,p′-DDD (i.e., ∑DDT), HCB, α-, β- and γ-HCH, trans-chlordane, cis-chlordane, oxy-chlordane, trans-nonachlor, cis-nonachlor, mirex and polychlorinated biphenyls (CB 28, 52, 99, 101, 105, 114, 118, 123, 128, 138, 141, 149, 153, 156, 157, 163, 167, 170, 180, 183, 187, 189, 194) were analyzed in breast milk collected in 2002 from 72 first-time mothers (median age 20years) living in the rural area Matlab, Bangladesh.
While the concentrations of PCBs and many of the pesticides were low, the concentrations of p,p′-DDT and its metabolite p,p′-DDE were high (median 349 and 1645ngg−1lipid, respectively) in comparison to other countries. The median value of ∑DDT was 2123ngg−1lipid. The estimated daily exposure to p,p′-DDT, p,p′-DDE and ∑DDTs was 10, 30 and 42μgkg−1 body weight, respectively, in 3months old infants. The p,p′-DDE/p,p′-DDT ratio ranged from 1 to 23, where 58% of the mothers had a ratio below 5 indicating recent or ongoing DDT exposure.
This study reports infant exposure and maternal body burden of organochlorines through breast milk. Although the findings give no reason to limit breast-feeding, it is essential to identify the main exposure sources and find means to decrease the exposure.
Pneumonia is an important cause of neonatal infection and accounts for significant morbidity and mortality in the neonatal period. The best way to reduce the high prevalence of pneumonia at this age ...group is through identification and elimination of its risk factors. This case-control study was conducted in the department of Pediatrics, Dhaka Medical College & Hospital during Nov 2007 to Nov 2008 with an aim to identify the risk factors of pneumonia. Data were collected from 100 neonates, 50 cases and 50 controls who met the predefined inclusion criteria. Results shows mean birth weight (p<0.05), inadequate antenatal care (p<0.001), normal vaginal delivery (p<0.05), home delivery (p<0.001), delivery by untrained personnel (p<0.001), neonatal resuscitation (p<0.001), intrapartum fever (p<0.01), obstetric problem of mother (p<0.001), foul smelling liquor (p<0.01), prolonged rupture of membrane (p<0.001), prolonged labour (p<0.05) were significantly associated with pneumonia. Multivariate analysis showed inadequate antenatal care (OR 168.9), home delivery (OR 13.8), intrapartum fever (OR 225.9), obstetric problem of mother (OR 33.4), requirement of resuscitation (OR 12.5), prolonged labour (OR 15.2) as significant risk factors of neonatal pneumonia.
In the past two decades, deeply virtual Compton scattering of electrons has been successfully used to advance our knowledge of the partonic structure of the free proton and investigate correla- tions ...between the transverse position and the longitudinal momentum of quarks inside the nucleon. Meanwhile, the structure of bound nucleons in nuclei has been studied in inclusive deep-inelastic lepton scattering experiments off nuclear targets, showing a significant difference in longitudinal momentum distribution of quarks inside the bound nucleon, known as the EMC effect. In this work, we report the first beam spin asymmetry (BSA) measurement of exclusive deeply virtual Compton scattering (DVCS) off a proton bound in 4He. The data used here were accumulated using a 6 GeV longitudinally polarized electron beam incident on a pressurized 4He gaseous target placed within the CLAS spectrometer in Hall-B at the Thomas Jefferson National Accelerator Facility. The azimuthal angle ($φ$) dependence of the BSA was studied in a wide range of virtual photon and scattered proton kinematics. The $Q^2$, $x_B$, and t dependencies of the BSA on the bound proton are compared with those on the free proton. In the whole kinematical region of our measurements, the BSA on the bound proton is smaller by 20% to 40%, indicating possible medium modification of its partonic structure.
In the past two decades, deeply virtual Compton scattering of electrons has been successfully used to advance our knowledge of the partonic structure of the free proton and investigate correlations ...between the transverse position and the longitudinal momentum of quarks inside the nucleon. Meanwhile, the structure of bound nucleons in nuclei has been studied in inclusive deep-inelastic lepton scattering experiments off nuclear targets, showing a significant difference in longitudinal momentum distribution of quarks inside the bound nucleon, known as the EMC effect. In this Letter, we report the first beam spin asymmetry (BSA) measurement of exclusive deeply virtual Compton scattering off a proton bound in He-4. The data used here were accumulated using a 6 GeV longitudinally polarized electron beam incident on a pressurized He-4 gaseous target placed within the CLAS spectrometer in Hall-B at the Thomas Jefferson National Accelerator Facility. The azimuthal angle (phi) dependence of the BSA was studied in a wide range of virtual photon and scattered proton kinematics. The Q(2), x(B), and t dependencies of the BSA on the bound proton are compared with those on the free proton. In the whole kinematical region of our measurements, the BSA on the bound proton is smaller by 20% to 40%, indicating possible medium modification of its partonic structure.
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