Theory of parity violation in compound nuclear states; one particle aspects

In this work we formulate the reaction theory of parity violation in compound nuclear states using Feshbach's projection operator formalism. We derive in this framework a complete set of terms that contribute to the longitudinal asymmetry measured in experiments with polarized epithermal neutrons. We also discuss the parity violating spreading width resulting from this formalism. We then use the above formalism to derive expressions which hold in the case when the doorway state approximation is introduced. In applying the theory we limit ourselves in this work to the case when the parity violating potential and the strong interaction are one-body. In this approximation, using as the doorway the giant spin-dipole resonance and employing well known optical potentials and a time-reversal even, parity odd one-body interaction we calculate or estimate the terms we derived. In our calculations we explicitly orthogonalize the continuum and bound wave functions. We find the effects of orthogonalization to be very important. Our conclusion is that the present one-body theory cannot explain the average longitudinal asymmetry found in the recent polarized neutron experiments. We also confirm the discrepancy, first pointed out by Auerbach and Bowman, that emerges, between the calculated average asymmetry and the parity violating spreading width, when distant doorways are used in the theory.Comment: 37 pages, REVTEX, 5 figures not included (Postscript, available from the authors

Fine Structure Discussion of Parity-Nonconserving Neutron Scattering at Epithermal Energies

The large magnitude and the sign correlation effect in the parity non-conserving resonant scattering of epithermal neutrons from $^{232}$Th is discussed in terms of a non-collective $2p-1h$ local doorway model. General conclusions are drawn as to the probability of finding large parity violation effects in other regions of the periodic table.Comment: 6 pages, Tex. CTP# 2296, to appear in Z. Phys.

Microscopic theories of neutrino-^{12}C reactions

In view of the recent experiments on neutrino oscillations performed by the LSND and KARMEN collaborations as well as of future experiments, we present new theoretical results of the flux averaged $^{12}C(\nu_e,e^-)^{12}N$ and $^{12}C(\nu_{\mu},{\mu}^-)^{12}N$ cross sections. The approaches used are charge-exchange RPA, charge-exchange RPA among quasi-particles (QRPA) and the Shell Model. With a large-scale shell model calculation the exclusive cross sections are in nice agreement with the experimental values for both reactions. The inclusive cross section for $\nu_{\mu}$ coming from the decay-in-flight of $\pi^+$ is $15.2 \times 10^{-40} cm^2$ to be compared to the experimental value of $12.4 \pm 0.3 \pm 1.8 \times 10^{-40} cm^2$, while the one due to $\nu_{e}$ coming from the decay-at-rest of $\mu^+$ is $16.4 \times 10^{-42} cm^2$ which agrees within experimental error bars with the measured values. The shell model prediction for the decay-in-flight neutrino cross section is reduced compared to the RPA one. This is mainly due to the different kind of correlations taken into account in the calculation of the spin modes and partially due to the shell-model configuration basis which is not large enough, as we show using arguments based on sum-rules.Comment: 17 pages, latex, 5 figure

Pion double charge exchange on 4He

The doubly differential cross sections for the $^4$He$(\pi^+,\pi^-) 4p$ reaction were calculated using both a two-nucleon sequential single charge exchange model and an intranuclear cascade code. Final state interactions between the two final protons which were the initial neutrons were included in both methods. At incident pion energies of 240 and 270 MeV the low-energy peak observed experimentally in the energy spectrum of the final pions can be understood only if the contribution of pion production is included. The calculated cross sections are compared with data.Comment: 25 pages, 9 figure

Vibrational States of the Hydrogen Isotopes on Pd(111)

The ground and excited vibrational states for the three hydrogen isotopes on the Pd(111) surface have been calculated. Notable features of these states are the high degree of anharmonicity, which is most prominently seen in the weak isotopic dependence of the parallel vibrational transition, and the narrow bandwidths of these states, which imply that atomic hydrogen is localized on a particular surface site on time scales of 100 picoseconds or more. Experiments to resolve ambiguities concerning the present system are suggested.Comment: Surface Science Letters, 302, L305 (1994

Induced Parity Nonconserving Interaction and Enhancement of Two-Nucleon Parity Nonconserving Forces

Two-nucleon parity nonconserving (PNC) interaction induced by the single-particle PNC weak potential and the two-nucleon residual strong interaction is considered. An approximate analytical formula for this Induced PNC Interaction (IPNCI) between proton and neutron is derived ($Q({\bf r} {\bf \sigma}_{p} \times {\bf \sigma}_{n}) \delta({\bf r}_{p}-{\bf r}_{n})$), and the interaction constant is estimated. As a result of coherent contributions from the nucleons to the PNC potential, IPNCI is an order of magnitude stronger ($\sim A^{1/3}$) than the residual weak two-nucleon interaction and has a different coordinate and isotopic structure (e.g., the strongest part of IPNCI does not contribute to the PNC mean field). IPNCI plays an important role in the formation of PNC effects, e.g., in neutron-nucleus reactions. In that case, it is a technical way to take into account the contribution of the distant (small) components of a compound state which dominates the result. The absence of such enhancement ($\sim A^{1/3}$) in the case of T- and P-odd interaction completes the picture.Comment: Phys. Rev. C, to appear; 17 pages, revtex 3, no figure

Cognitive testing of an instrument to evaluate acceptability and use of pre-exposure prophylaxis products among women

Given the range of pre-exposure prophylaxis (PrEP) products currently being tested to prevent HIV in women, a standardized Acceptability and Use of PrEP Products Among Women Tool may facilitate comparisons of product acceptability and use across different geographies, trials, and users. We conducted three rounds of cognitive interviewing over 2 months in 2016, with 28 South African women who had experience participating in a range of PrEP product trials. The final instrument contained 41 items, including five new items that improved construct validity and 22 items modified for clarity. Changes were made due to unclear wording, difficulty answering, participant embarrassment, low response variability, and administrative formatting. Cognitive interviewing provided a means to address issues that would have inhibited this tool's ability to accurately collect data otherwise. This rapid, low-cost study provided valuable insight into participants' understanding of questions and demonstrated the utility of cognitive interviewing in international clinical trials

HIV and women in the USA: what we know and where to go from here

New diagnoses of HIV infection have decreased among women in the USA overall, but marked racial and geographical disparities persist. The federal government has announced an initiative that aims to decrease the number of new infections in the nation by 90% within the next 10 years. With this in mind, we highlight important recent developments concerning HIV epidemiology, comorbidities, treatment, and prevention among women in the USA. We conclude that, to end the US HIV epidemic, substantially greater inclusion of US women in clinical research will be required, as will better prevention and treatment efforts, with universal access to health care and other supportive services that enable women to exercise agency in their own HIV prevention and care. Ending the epidemic will also require eliminating the race, class, and gender inequities, as well as the discrimination and structural violence, that have promoted and maintained the distribution of HIV in the USA, and that will, if unchecked, continue to fuel the epidemic in the future

Shell-model calculations of neutrino scattering from 12C

Neutrino reaction cross-sections, $(\nu_\mu,\mu^-)$, $(\nu_e,e^-)$, $\mu$-capture and photoabsorption rates on $^{12}$C are computed within a large-basis shell-model framework, which included excitations up to $4\hbar\omega$. When ground-state correlations are included with an open $p$-shell the predictions of the calculations are in reasonable agreement with most of the experimental results for these reactions. Woods-Saxon radial wave functions are used, with their asymptotic forms matched to the experimental separation energies for bound states, and matched to a binding energy of 0.01 MeV for unbound states. For comparison purposes, some results are given for harmonic oscillator radial functions. Closest agreement between theory and experiment is achieved with unrestricted shell-model configurations and Woods-Saxon radial functions. We obtain for the neutrino-absorption inclusive cross sections: $\bar{\sigma} = 13.8 \times 10^{-40}$ cm$^2$ for the $(\nu_{\mu},\mu^{-})$ decay-in-flight flux in agreement with the LSND datum of $(12.4 \pm 1.8) \times 10^{-40}$ cm$^2$; and $\bar{\sigma} = 12.5 \times 10^{-42}$ cm$^2$ for the $(\nu_{e},e^{-})$ decay-at-rest flux, less than the experimental result of $(14.4 \pm 1.2) \times 10^{-42}$ cm$^2$.Comment: 19 pages. ReVTeX. No figure

Effects of T- and P-odd weak nucleon interaction in nuclei: renormalizations due to residual strong interaction, matrix elements between compound states and their correlations with P-violating matrix elements

Manifestations of P-,T-odd weak interaction between nucleons in nucleus are considered. Renormalization of this interaction due to residual strong interaction is studied. Mean squared matrix elements of P-,T-odd weak interaction between compound states are calculated. Correlators between P-,T-odd and P-odd, T-even weak interaction matrix elements between compound states are considered and estimates for these quantities are obtained.Comment: Submitted to Phys. Rev. C; 21 pages, REVTEX 3, no figure