821 research outputs found
Subthreshold rho^0 photoproduction on 3He
A large reduction of the rho^0 mass in the nuclear medium is reported,
inferred from dipion photoproduction spectra in the 1 GeV region, for the
reaction 3He(gamma,pi+ pi-)X with a 10% duty factor tagged-photon beam and the
TAGX multi-particle spectrometer. The energy range covered (800 < E(gamma) <
1120 MeV) lies mostly below the free rho^0 production threshold, a region which
is believed sensitive to modifications of light vector-meson properties at
nuclear-matter densities. The rho^0 masses extracted from the MC fitting of the
data, m*(rho^0) = 642 +/- 40, 669 +/- 32, and 682 +/- 56 MeV/c^2 for E(gamma)
in the 800-880, 880-960, and 960-1040 MeV regions respectively, are
independently corroborated by a measured, assumption-free, kinematical
observable. This mass shift, far exceeding current mean-field driven
theoretical predictions, may be suggestive of rho^0 decay within the range of
the nucleonic field.Comment: 40 pages, 13 figures, submitted to Phys. Rev.
- nucleus bound states in Walecka model
Possible formation of nucleus bound state is studied in the framework
of Walecka model. The bound states are found in different nuclei ranging from
to . These bound states may have a direct bearing on the
recent experiments on the photoproduction of meson in the nuclear
medium.Comment: RevTeX fil
Political cycles in Greece's municipal employment
We consider the politically motivated fluctuations in Greece’s municipal employment, constructing a data-set from primary data and focusing on the composition of municipal employment in terms of employment relationship forms. Our analysis produces strong evidence of pre-electoral manipulation through increases in the number of contract employees. Considering a number of control variables and robustness checks does not affect the key results. Such variables include whether mayors run for reelection, incumbents’ political alignment with central government, partisan shifts, general elections, mayors’ turnover rate, and timing patterns. Our evidence provides insights into Greece’s political economy in the run-up to the current economic crisis
Measurement of Inverse Pion Photoproduction at Energies Spanning the N(1440) Resonance
Differential cross sections for the process pi^- p -> gamma n have been
measured at Brookhaven National Laboratory's Alternating Gradient Synchrotron
with the Crystal Ball multiphoton spectrometer. Measurements were made at 18
pion momenta from 238 to 748 MeV/c, corresponding to E_gamma for the inverse
reaction from 285 to 769 MeV. The data have been used to evaluate the gamma n
multipoles in the vicinity of the N(1440) resonance. We compare our data and
multipoles to previous determinations. A new three-parameter SAID fit yields 36
+/- 7 (GeV)^-1/2 X 10^-3 for the A^n_1/2 amplitude of the P_11.Comment: 14 pages, 8 figures, submitted to PR
Polarization transfer in the d(epol,e' ppol)n reaction up to Q^2=1.61 (GeV/c)^2
The recoil proton polarization was measured in the d(epol,e' ppol)n reaction
in Hall A of the Thomas Jefferson National Accelerator Facility (JLab). The
electron kinematics were centered on the quasielastic peak (x_{Bj}~1) and
included three values of the squared four-momentum transfer, Q^2=0.43, 1.00 and
1.61 (GeV/c)^2. For Q^2=0.43 and 1.61 (GeV/c)^2, the missing momentum, p_m, was
centered at zero while for Q^2=1.00 (GeV/c)^2 two values of p_m were chosen: 0
and 174 MeV/c. At low p_m, the Q^2 dependence of the longitudinal polarization,
P_z', is not well described by a state-of-the-art calculation. Further, at
higher p_m, a 3.5 sigma discrepancy was observed in the transverse
polarization, P_x'. Understanding the origin of these discrepancies is
important in order to confidently extract the neutron electric form factor from
the analogous d(epol,e' npol)p experiment.Comment: 6 pages, 4 figures; updated text, figures and table
Prevalence and Predictors of Vitamin D Insufficiency in Children: A Great Britain Population Based Study
Objectives
To evaluate the prevalence and predictors of vitamin D insufficiency (VDI) in children In Great Britain.
Design
A nationally representative cross-sectional study survey of children (1102) aged 4–18 years (999 white, 570 male) living in private households (January 1997–1998). Interventions provided information about dietary habits, physical activity, socio-demographics, and blood sample. Outcome measures were vitamin D insufficiency (<50 nmol/L).
Results
Vitamin D levels (mean = 62.1 nmol/L, 95%CI 60.4–63.7) were insufficient in 35%, and decreased with age in both sexes (p<0.001). Young People living between 53–59 degrees latitude had lower levels (compared with 50–53 degrees, p = 0.045). Dietary intake and gender had no effect on vitamin D status. A logistic regression model showed increased risk of VDI in the following: adolescents (14–18 years old), odds ratio (OR) = 3.6 (95%CI 1.8–7.2) compared with younger children (4–8 years); non white children (OR = 37 [95%CI 15–90]); blood levels taken December-May (OR = 6.5 [95%CI 4.3–10.1]); on income support (OR = 2.2 [95%CI 1.3–3.9]); not taking vitamin D supplementation (OR = 3.7 [95%CI 1.4–9.8]); being overweight (OR 1.6 [95%CI 1.0–2.5]); <1/2 hour outdoor exercise/day/week (OR = 1.5 [95%CI 1.0–2.3]); watched >2.5 hours of TV/day/week (OR = 1.6[95%CI 1.0–2.4]).
Conclusion
We confirm a previously under-recognised risk of VDI in adolescents. The marked higher risk for VDI in non-white children suggests they should be targeted in any preventative strategies. The association of higher risk of VDI among children who exercised less outdoors, watched more TV and were overweight highlights potentially modifiable risk factors. Clearer guidelines and an increased awareness especially in adolescents are needed, as there are no recommendations for vitamin D supplementation in older children
Positive pion absorption on 3He using modern trinucleon wave functions
We study pion absorption on 3He employing trinucleon wave functions
calculated from modern realistic NN interactions (Paris, CD Bonn). Even though
the use of the new wave functions leads to a significant improvement over older
calculations with regard to both cross section and polarization data, there are
hints that polarization data with quasifree kinematics cannot be described by
just two-nucleon absorption mechanisms.Comment: 14 pages, 6 figure
- …