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The Q weak experiment, which took data at Jefferson Lab in the period 2010 - 2012, will precisely determine the weak charge of the proton by measuring the parity-violating asymmetry in elastic e-p scattering at 1.1 GeV using a longitudinally polarized electron beam and a liquid hydrogen target at a low momentum transfer of Q 2 = 0.025 (GeV/c)2 . The weak charge of the proton is predicted by the Standard Model and any significant deviation would indicate physics beyond the Standard Model. The technical challenges and experimental apparatus for measuring the weak charge of the proton will be discussed, as well as the method of extracting the weak charge of the proton. The results from a small subset of the data, that has been published, will also be presented. Furthermore an update will be given of the current status of the data analysis.

A precision measurement of spin transfer in $\mathrm{pp}$ elastic scattering at 197.8 MeV has been completed recently at the Indiana University Cyclotron Facility. The new data span a kinematic regime chosen specifically to maximize sensitivity to the neutral $\ensuremath{\pi}\mathrm{NN}$ coupling constant. Our results provide strong support for modern potential models of the $\mathrm{NN}$ interaction in which a relatively weak pion coupling ( ${g}_{0}^{2}\ensuremath{\approx}13.6$, ${f}_{0}^{2}\ensuremath{\approx}0.075$) is employed, but disagree significantly with predictions of older models in which ${g}_{0}^{2}\ensuremath{\approx}14.4$. Calculations in a one-boson-exchange framework indicate that most of these latter differences can be removed by reducing ${g}_{0}^{2}$ from 14.4 to 13.6 in these models.

We report measurements of {sigma}({theta}), A({theta}), and polarization transfer for the {sup 28}Si({rvec p},{rvec p}{sup {prime}}){sup 28}Si reaction to the 6{sup {minus}},T=1 state at 14.36MeV initiated with 198MeV polarized protons. Normalization of the transition strength in the distorted-wave impulse approximation (DWIA) to inelastic electron scattering overpredicts the spin-longitudinal cross section by more than a factor of 2, while the spin-transverse cross section is nearly correct and the spin-orbit cross section is underpredicted. A reduced in-medium {rho}-meson mass reproduces some of these features, while strong relativistic mean field or Pauli blocking effects are too small. {copyright} {ital 1997} {ital The American Physical Society}

We report measurements of in-plane polarization transfer for nine natural-parity isoscalar transitions in the $^{28}\mathrm{Si}$(p\ensuremath{\rightarrow},p${\ensuremath{\rightarrow}}^{\ensuremath{'}}$${)}^{28}$Si reaction using a 198.5 MeV polarized proton beam. These measurements test in a new way the validity of an empirical effective NN interaction derived from cross section and analyzing power measurements for similar transitions. The test is successful, demonstrating the need to modify the free NN interaction in the nuclear medium. \textcopyright{} 1996 The American Physical Society.

We have made simultaneous measurements of singles ($\stackrel{\ensuremath{\rightarrow}}{p}, {\stackrel{\ensuremath{\rightarrow}}{p}}^{\ensuremath{'}}$) spin-transfer observables and coincident ($\stackrel{\ensuremath{\rightarrow}}{p}, {p}^{\ensuremath{'}}\ensuremath{\gamma}$) yields and asymmetries for the 15.11 MeV, ${1}^{+}$, $T=1$ state in $^{12}\mathrm{C}$, at an incident proton bombarding energy of 200 MeV. Data were taken at four proton scattering angles ranging from ${\ensuremath{\theta}}_{p}^{\mathrm{c}.\mathrm{m}.}=5.5\ifmmode^\circ\else\textdegree\fi{} \mathrm{to} 16.5\ifmmode^\circ\else\textdegree\fi{}$. Both vertical (normal to the reaction plane) and horizontal (in-plane) incident beam polarizations were used, which allowed us to extract 16 different observables for this transition. In particular, using the ($\stackrel{\ensuremath{\rightarrow}}{p}, {p}^{\ensuremath{'}}\ensuremath{\gamma}$) reaction, we measured the sideways and longitudinal analyzing powers, ${D}_{0S}$ and ${D}_{0L}$, which vanish identically in the ($\stackrel{\ensuremath{\rightarrow}}{p}, {p}^{\ensuremath{'}}$) reaction. Detailed comparisons of all observables to calculations done in both relativistic and nonrelativistic formalisms are presented. Surprisingly, a relativistic description in which knock-on exchange processes are not explicitly included provides the best overall agreement with the data.

The importance of high quality spin-observable data in intermediate energy nuclear physics requires that techniques be developed for obtaining accurate and reliable measurements of incident beam polarizations in a nondestructive manner. For this purpose, we have constructed, installed, and calibrated two transmission-type polarimeters at IUCF, in which p+d elastic scattering is used to determine the two transverse polarization components of a high energy proton beam. In this report, we discuss some of our experimental design considerations, and provide technical details on the actual implementation schemes chosen. Representative spectra are shown, and typical performance capabilities are described. We have also completed a calibration of the effective analyzing power of the polarimeter (Apol) as a function of the incident (beam) proton energy, and find Apol ≈ 0.51 over the entire proton energy range studied in this work ( ∼ 150–200 MeV) when θdlab = 42.6°.

The analyzing power ${\mathit{A}}_{\mathit{y}}$ for proton elastic scattering on $^{12}\mathrm{C}$ has been precisely and absolutely determined at three scattering angles (${\mathrm{\ensuremath{\theta}}}_{\mathrm{lab}}$=16.3\ifmmode^\circ\else\textdegree\fi{}, 17.3\ifmmode^\circ\else\textdegree\fi{}, and 18.3\ifmmode^\circ\else\textdegree\fi{}) at an incident proton energy of 188.9 MeV. The technique employed requires statistically high quality polarization transfer measurements, combined with the constraints imposed on polarization observables for reactions with the spin structure 1/2+0\ensuremath{\rightarrow}1/2+0. These results represent some of the most accurately known spin observables at intermediate energies and serve as calibration points for secondary standards.

Measurements using 200 MeV protons, of the spin-flip probability parameter {ital S}{sub {ital N}{ital N}{prime}} have been made on {sup 208}Pb covering an excitation energy range of 2 to 24 MeV for momentum transfers from 0.45 to 0.84 fm{sup {minus}1}. These data have been compared to calculations that use random-phase-approximation wave functions in an impulse approximation model. Distortions are shown to have a large effect in the calculation of {ital S}{sub {ital N}{ital N}{prime}}. The calculations describe the data well and suggest that natural parity transitions contribute significantly to the spin-flip response. A broad structure is observed near 7 MeV; calculations suggest that this structure is composed of a superposition of a number of spins and parities.

We report angular distribution measurements of the cross section, analyzing power, induced polarization, and all polarization transfer coefficients for the natural parity transitions in $^{10}\mathrm{B}$($\stackrel{\ensuremath{\rightarrow}}{p},{\stackrel{\ensuremath{\rightarrow}}{p}}^{'}){}^{10}$B at 197 MeV. All of the transitions closely follow the pattern for spin-1/2 scattering from spin-0, namely $A=P,{D}_{{\mathit{SS}}^{'}}={D}_{{\mathit{LL}}^{'}}$, and ${D}_{{\mathit{SL}}^{'}}=\ensuremath{-}{D}_{{\mathit{LS}}^{'}}$. Small deviations from ${D}_{{\mathit{NN}}^{'}}=1$ reflect spin-flip contributions to these transitions. Distorted wave impulse approximation calculations were generally successful, supporting the use of an empirical effective nucleon-nucleon interaction, the inclusion of channel-coupling in the ground state and the ${3}^{+}\ensuremath{\leftrightarrow}{4}^{+}$ transition, and the procedure of increasing the $L=2$ strength of shell-model particle-hole matrix elements to match the collective contribution to these transitions.

Using data obtained through simultaneous measurements of $(\stackrel{\ensuremath{\rightarrow}}{p},{p}^{\ensuremath{'}})$ spin-transfer observables and $(\stackrel{\ensuremath{\rightarrow}}{p}{,p}^{\ensuremath{'}}\ensuremath{\gamma})$ coincident spin observables, we have made a model-independent determination of the complete scattering amplitude for the 15.11 MeV, ${1}^{+},$ $T=1$ state in ${}^{12}\mathrm{C}$ at an incident proton energy of 200 MeV, for four proton scattering angles ranging from ${\ensuremath{\theta}}_{\mathrm{c}.\mathrm{m}.}=5.5\ifmmode^\circ\else\textdegree\fi{}\char21{}16.5\ifmmode^\circ\else\textdegree\fi{}.$ At each angle, 16 different observables were determined, whereas only 11 independent quantities are required to specify the transition amplitude for this state. It had been shown previously that the set of observables measured span the allowed space; hence the system is overdetermined, which allowed us to extract, in a model-independent fashion, each of the individual spin-operator amplitudes that characterize the reaction. Additional insight into the physical mechanisms that drive this transition is obtained by mapping out the momentum-transfer dependence of these amplitudes. We also compare the magnitudes and phases determined for each of the spin-operator amplitudes to the predictions of calculations performed in both relativistic and nonrelativistic frameworks, and discuss the physics content of these comparisons.

Using a 198.3 MeV polarized proton beam, measurements have been made of the dσ/dΩ, A and DNN′ for the 28Si(p↘,p↘′)28Si reaction to locate the 6− strength for comparison with large basis shell model calculations. Based on both dσ/dΩ and A data, six states above 15 MeV were determined to carry 6− strength. The measurements of & were used as a meter of isospin mixing. The shell model calculations do not match the experimental results.

Recent analyses of NN and πN scattering data have resulted in values for the πNN coupling constant which are significantly smaller than those obtained prior to 1987. These controversial results prompted us to investigate the usefulness of high‐quality spin measurements towards resolving this issue. We found that the normal component spin transfer observable DNN′ for p+p elastic scattering is very sensitive to g20, particularly at small angles. We have therefore determined precise values of DNN′ for this reaction for θlab=5.0°, 7.2°, 8.4°, 9.7°, 11.8°, 14.6°, 18.8°, 24°, 30°, and 38° at an incident beam energy of 200 MeV. The forward‐going proton was detected in the IUCF K600 spectrometer and the coincident recoil proton was detected in a Si/CsI detector telescope. Our preliminary DNN′ values are reproduced reasonably well by Arndt’s C200 solution, the Nijmegen PWA93, and the Nijmegen I potential, but differ severely from both Arndt’s SM94 global solution and the predictions of the Bonn potential.