Ultra-wideband (UWB) signals exhibit different characteristics upon propagation through matter compared with narrow-band signals. The latter keeps a sinusoidal shape during different forms of signal ...propagation. The behavior of narrow-band signals does not apply to UWB signals in many cases. Presently, the possibilities for development of UWB signaling technology remain largely unexplored. Few applications have been developed due to strict regulations by the Federal Communications Commission (FCC). In this paper, we describe a series of experiments that have been carried out to determine the behavior of UWB signals and their properties. A transverse electromagnetic (TEM) horn antenna has been made for radiating UWB signals. A procedure for propagating UWB signals through a liquid medium of given salt concentration has been demonstrated, providing a basis for studying UWB signal propagation in biological matter. A new pulsewidth definition was adopted, which is suitable for propagated UWB signals.
The Q(weak) experiment has measured the parity-violating asymmetry in ep elastic scattering at Q(2)=0.025(GeV/c)(2), employing 145 μA of 89% longitudinally polarized electrons on a 34.4 cm long ...liquid hydrogen target at Jefferson Lab. The results of the experiment's commissioning run, constituting approximately 4% of the data collected in the experiment, are reported here. From these initial results, the measured asymmetry is A(ep)=-279±35 (stat) ± 31 (syst) ppb, which is the smallest and most precise asymmetry ever measured in ep scattering. The small Q(2) of this experiment has made possible the first determination of the weak charge of the proton Q(W)(p) by incorporating earlier parity-violating electron scattering (PVES) data at higher Q(2) to constrain hadronic corrections. The value of Q(W)(p) obtained in this way is Q(W)(p)(PVES)=0.064±0.012, which is in good agreement with the standard model prediction of Q(W)(p)(SM)=0.0710±0.0007. When this result is further combined with the Cs atomic parity violation (APV) measurement, significant constraints on the weak charges of the up and down quarks can also be extracted. That PVES+APV analysis reveals the neutron's weak charge to be Q(W)(n)(PVES+APV)=-0.975±0.010.
Ultra-wideband (UWB) electromagnetic pulses of nanosecond duration, or nanopulses, have recently been approved by the Federal Communications Commission for a number of different applications. They ...are also being explored for applications in biotechnology and medicine. The simulation of the propagation of a nanopulse through biological matter, previously performed using a two-dimensional finite-difference time-domain (FDTD) method, has been extended here into a full three-dimensional computation. To account for the UWB frequency range, the geometrical resolution of the exposed sample was 0.25 mm and the dielectric properties of biological matter were accurately described in terms of the Debye model. The results obtained from the three-dimensional computation support the previously obtained results: the electromagnetic field inside a biological tissue depends on the incident pulse rise time and width, with increased importance of the rise time as the conductivity increases; no thermal effects are possible for the low pulse repetition rates, supported by recent experiments. New results show that the dielectric sample exposed to nanopulses behaves as a dielectric resonator. For a sample in a cuvette, we obtained the dominant resonant frequency and the Q-factor of the resonator.
We have measured parity-violating asymmetries in elastic electron-proton and quasielastic electron-deuteron scattering at Q2=0.22 and 0.63 GeV2. They are sensitive to strange quark contributions to ...currents in the nucleon and the nucleon axial-vector current. The results indicate strange quark contributions of approximately < 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-vector current at these four-momentum transfers.
In this paper, we report the first measurement of the parity-violating elastic electron scattering asymmetry on 27Al. The 27Al elastic asymmetry is $A_{\text{PV}}$ = 2.16 ± 0.11(stat) ± 0.16(syst) ...ppm, and was measured at $\langle Q^2\rangle$ = 0.02357 ± 0.00010 GeV$^2$, $\angleθ_{\text{lab}}$ = 7.61° ± 0.02°, and $\langle E_{\text{lab}}$ = 1.157 GeV with the Qweak apparatus at Jefferson Lab. Predictions using a simple Born approximation as well as more sophisticated distorted-wave calculations are in good agreement with this result. From this asymmetry the 27Al neutron radius $R_n$ = 2.89 ± 0.12 fm was determined using a many-models correlation technique. The corresponding neutron skin thickness $R_n – R_p$ = –0.04 ± 0.12 fm is small, as expected for a light nucleus with a neutron excess of only 1. This result thus serves as a successful benchmark for electroweak determinations of neutron radii on heavier nuclei. A tree-level approach was used to extract the 27Al weak radius $R_w$ = 3.00 ± 0.15 fm, and the weak skin thickness $R_{\text{wk}} – R_{\text{ch}}$ = –0.04 ± 0.15 fm. The weak form factor at this $Q^2$ is $F_{\text{wk}}$ = 0.39 ± 0.04.
An experiment with a newly developed high-resolution kaon spectrometer and a scattered electron spectrometer with a novel configuration was performed in Hall C at Jefferson Lab. The ground state of a ...neutron-rich hypernucleus, (Λ)(7)He, was observed for the first time with the (e, e'K+) reaction with an energy resolution of ~0.6 MeV. This resolution is the best reported to date for hypernuclear reaction spectroscopy. The (Λ)(7)He binding energy supplies the last missing information of the A = 7, T = 1 hypernuclear isotriplet, providing a new input for the charge symmetry breaking effect of the ΛN potential.
We report measurements of the parity-conserving beam-normal single-spin elastic scattering asymmetries Bn on 12C and 27Al, obtained with an electron beam polarized transverse to its momentum ...direction. These measurements add an additional kinematic point to a series of previous measurements of Bn on 12C and provide a first measurement on 27Al. The experiment utilized the Qweak apparatus at Jefferson Lab with a beam energy of 1.158 GeV. The average lab scattering angle for both targets was 7.7°, and the average Q2 for both targets was 0.02437 GeV2 (Q = 0.1561 GeV). The asymmetries are Bn = -10.68 ± 0.90 (stat) ± 0.57 (syst) ppm 12C and Bn = -12.16 ± 0.58 (stat) ± 0.62 (syst) ppm for 27Al. The results are consistent with theoretical predictions, and are compared to existing data. When scaled by Z/A, the Q dependence of all the far-forward angle (θ < 10°) data from 1H to 27Al can be described by the same slope out to Q ≈ 0.35 GeV. Larger-angle data from other experiments in the same Q range are consistent with a slope about twice as steep.