38 research outputs found
Strange Quark Contributions to Parity-Violating Asymmetries in the Backward Angle G0 Electron Scattering Experiment
We have measured parity-violating asymmetries in elastic electron-proton and
quasi-elastic electron-deuteron scattering at Q^2 = 0.22 and 0.63 GeV^2. They
are sensitive to strange quark contributions to currents in the nucleon, and to
the nucleon axial current. The results indicate strange quark contributions of
< 10% of the charge and magnetic nucleon form factors at these four-momentum
transfers. We also present the first measurement of anapole moment effects in
the axial current at these four-momentum transfers.Comment: 5 pages, 2 figures, changed references, typo, and conten
Transverse Beam Spin Asymmetries at Backward Angles in Elastic Electron-Proton and Quasi-elastic Electron-Deuteron Scattering
We have measured the beam-normal single-spin asymmetries in elastic
scattering of transversely polarized electrons from the proton, and performed
the first measurement in quasi-elastic scattering on the deuteron, at backward
angles (lab scattering angle of 108 degrees) for Q2 = 0.22 GeV^2/c^2 and 0.63
GeV^2/c^2 at beam energies of 362 MeV and 687 MeV, respectively. The asymmetry
arises due to the imaginary part of the interference of the two-photon exchange
amplitude with that of single photon exchange. Results for the proton are
consistent with a model calculation which includes inelastic intermediate
hadronic (piN) states. An estimate of the beam-normal single-spin asymmetry for
the scattering from the neutron is made using a quasi-static deuterium
approximation, and is also in agreement with theory
First Midwives in the Town of Bjelovar, Croatia 1756-1856
Prve izučene (aprobirane) primalje dolaze u novoosnovani Bjelovar, jako vojno središte Vojne krajine početkom druge polovice XVIII. stoljeća zajedno s vojnim liječnicima, kirurzima i ljekarnicima, a većina njih je germanskoga podrijetla. U do sada neistraženom arhivskom materijalu za razdoblje 1756.-1856. pronađeni su podaci o 23 izučene primalje, od kojih je 14 bilo pukovnijskih i 9 gradskih primalja. Visok perinatalni pomor djece i majki i kriminalni pobačaji karakteristike su toga razdoblja. Uz model domicilnoga primaljstva: skrb za trudnice, rodilje, babinjače, novorođenčad i dojenčad, primalje u teškim porodima obavljaju krštenje iz nužde ugroženoj novorođenčadi ili su pak krsne kume zdravoj dojenčadi. Premda je u samom gradu Bjelovaru ustrojeno stručno primaljstvo, u okolici grada i dalje se porodi obavljaju bez stručne pomoći. Za razliku od većine tadašnjih gradova kontinentalne Hrvatske, pa i Dalmacije, u Bjelovaru postoji kontinuirano izučeno primaljstvo i zaštita materinstva od polovice XVIII. stoljeća.The first trained (certified) midwives came to the newly founded town of Bjelovar, a strong military centre of Vojna Krajina (Croatian province bordering Ottoman Empire), at the beginning of the 1750s, along with army physicians, surgeons, and pharmacists. Most were of German origin. The archival material investigated for the period 1756-1856 speaks of 23 certified midwives, of whom 14 were regimental and nine municipal. This period was characterised by high neonatal and maternal mortality rates and criminal abortions. Within the scope of the domiciliary midwifery model that included care for pregnant women, parturient women, neonates, and infants, midwives used to act as godmothers to newborns at risk, in periculo, or to healthy newborns. Although Bjelovar had professional midwifery service, the practice of unassisted childbirths continued in the town surroundings. Unlike other inland and coastal (Dalmatian) towns of the time, Bjelovar has had a continuous tradition of training midwives and maternal health care since the 1750s
Višenukleonska emisija nakon pionske apsorpcije u N, Ar i Xe
Positive pion absorption was studied in an almost 4π geometry allowing simultaneous measurements of various charge and neutral multiplicities. Total absorption cross sections and its decomposition into the most important channels is determined. The results are presented for N, Ar and Xe nuclei at incident pion energies of 118,162 and 239 MeV. The role of multinucleon emission in the absorption process is emphasized.Proučava se pionska apsorpcija s blizu 4π detekcijom koja dozvoljava istovremeno mjerenje raznih nabojskih i neutralnih višestrukosti. Određuju se ukupni udarni presjeci i njihovo razlaganje u najvažnije kanale. Predstavljaju se rezultati za jezgre N, Ar i Xe na energijama 118,162 i 239 MeV. Ističe se uloga višenukleonske emisije u procesu apsorpcije
Pionska apsorpcija u 4He
This paper presents a large solid angle measurement of the positive pion absorption cross-section on 4He and its decomposition into partial channels. A large fraction of the absorption cross-section at incident pion kinetic energies of Tπ+ =70, 118, 162, 239, and 330 MeV is due to multinucleon channels.Daju se ishodi mjerenja pod velikim prostornim kutom udarnog presjeka za apsorpciju pozitivnih piona u He4 i razdjela na pojedine kanale. Velik dio apsorpcijskog udarnog presjeka za energije upadnih piona od Tπ+ =70, 118, 162, 239 i 330 MeV je posljedica višenukleonskih kanala
The G0 Experiment: Apparatus for Parity-Violating Electron Scattering Measurements at Forward and Backward Angles
In the G0 experiment, performed at Jefferson Lab, the parity-violating
elastic scattering of electrons from protons and quasi-elastic scattering from
deuterons is measured in order to determine the neutral weak currents of the
nucleon. Asymmetries as small as 1 part per million in the scattering of a
polarized electron beam are determined using a dedicated apparatus. It consists
of specialized beam-monitoring and control systems, a cryogenic hydrogen (or
deuterium) target, and a superconducting, toroidal magnetic spectrometer
equipped with plastic scintillation and aerogel Cerenkov detectors, as well as
fast readout electronics for the measurement of individual events. The overall
design and performance of this experimental system is discussed.Comment: Submitted to Nuclear Instruments and Method
Measurement of the Parity-Violating Asymmetry in Inclusive Electroproduction of π- near the Δ0 Resonance
The parity-violating (PV) asymmetry of inclusive π-production in electron scattering from a liquid deuterium target was measured at backward angles. The measurement was conducted as a part of the G0 experiment, at a beam energy of 360 MeV. The physics process dominating pion production for these kinematics is quasifree photoproduction off the neutron via the Δ0 resonance. In the context of heavy-baryon chiral perturbation theory, this asymmetry is related to a low-energy constant dΔ- that characterizes the parity-violating γNΔ coupling. Zhu et al. calculated dΔ- in a model benchmarked by the large asymmetries seen in hyperon weak radiative decays, and predicted potentially large asymmetries for this process, ranging from Aγ-=-5.2 to +5.2 ppm. The measurement performed in this work leads to Aγ-=-0.36±1.06±0.37±0.03 ppm (where sources of statistical, systematic and theoretical uncertainties are included), which would disfavor enchancements considered by Zhu et al. proportional to Vud/Vus. The measurement is part of a program of inelastic scattering measurements that were conducted by the G0 experiment, seeking to determine the N-Δ axial transition form factors using PV electron scattering
Parity-Violating Inelastic Electron-Proton Scattering at Low Above the Resonance Region
We report the measurement of the parity-violating asymmetry for the inelastic
scattering of electrons from the proton, at GeV and GeV, above the resonance region. The result ~ppm agrees with theoretical
calculations, and helps to validate the modeling of the interference
structure functions and used in those
calculations, which are also used for determination of the two-boson exchange
box diagram () contribution to parity-violating elastic
scattering measurements. A positive parity-violating asymmetry for inclusive
production was observed, as well as positive beam-normal single-spin
asymmetry for scattered electrons and a negative beam-normal single-spin
asymmetry for inclusive production.Comment: 18 pages, 9 figures, version accepted in Physical Review