M. H. Wood

The $\nu \mathrm{BDX}\text{−}\mathrm{DRIFT}$ Collaboration seeks to detect low-energy nuclear recoils from $\mathrm{CE}\nu \mathrm{NS}$ or BSM interactions at FNAL. Backgrounds due to rock neutrons are an important concern. We present a genie and geant4 based model to estimate backgrounds from rock neutrons produced in neutrino-nucleus interactions within the rock walls surrounding the underground halls. This model was bench-marked against the 2009 COUPP experiment performed in the MINOS hall in the NuMI neutrino beam, and agreement is found between experimental results and the modeled result to within 30%. Working from this validated model, a similar two-stage simulation was performed to estimate recoil backgrounds in the $\nu \mathrm{BDX}\text{−}\mathrm{DRIFT}$ detector across several beamlines. In the first stage utilizing geant4, neutrons were tallied exiting the walls of a rectangular underground hall utilizing four different neutrino beam configurations. These results are presented for use by other underground experiments requiring estimations of their rock neutron backgrounds. For $\nu \mathrm{BDX}\text{−}\mathrm{DRIFT}$, the second stage propagated neutrons from the walls and recorded energy deposited within a scintillator veto surrounding the detector and nuclear recoils within the detector’s fiducial volume. The directional signal from the $\nu \mathrm{BDX}\text{−}\mathrm{DRIFT}$ detector allows additional background subtraction. A sample calculation of a $10{\mathrm{m}}^3·\mathrm{yr}$ exposure to the NuMI low-energy beam configuration shows a $\mathrm{CE}\nu \mathrm{NS}$ signal-to-noise ratio of $\sim 2.5$.

We have measured the moment $A_{LU}^{\sin \varphi }$ corresponding to the polarized electron beam-spin asymmetry in semi-inclusive deep inelastic scattering. $A_{LU}^{\sin \varphi }$ is a twist-3 quantity providing information about quark-gluon correlations. Data were taken with the CLAS Spectrometer at Jefferson Lab using a 5.498 GeV longitudinally polarized electron beam and an unpolarized liquid hydrogen target. All three pion channels (${\pi }^{+}$, ${\pi }^0$ and ${\pi }^{-}$) were measured simultaneously over a large range of kinematics within the virtuality range $Q^2\approx 1.0–4.5{\mathrm{GeV}}^2$. The observable was measured with better than 1% statistical precision over a large range of $z$, $P_T$, $x_B$, and $Q^2$, which permits comparison with several reaction models. The discussed measurements provide an upgrade in statistics over previous measurements, and serve as the first evidence for the negative sign of the ${\pi }^{-}$ $\sin \varphi$ moment.

We report the first extraction of the pion-nucleon multipoles near the production threshold for the $n{\pi }^{+}$ channel at relatively high momentum transfer ($Q^2$ up to 4.2 ${\mathrm{GeV}}^2$). The dominance of the $s$-wave transverse multipole ($E_{0+}$), expected in this region, allowed us to access the generalized form factor $G_1$ within the light-cone sum-rule (LCSR) framework as well as the axial form factor $G_A$. The data analyzed in this work were collected by the nearly $4\pi$ CEBAF Large Acceptance Spectrometer (CLAS) using a 5.754-GeV electron beam on a proton target. The differential cross section and the $\pi$-$N$ multipole $E_{0+}/G_D$ were measured using two different methods, the LCSR and a direct multipole fit. The results from the two methods are found to be consistent and almost $Q^2$ independent.

We have measured the differential cross section for the $\gamma$ ${}^3\mathrm{He}$ $\to \pi {}^{+}t$ reaction. This reaction was studied using the Continuous Electron Beam Accelerator Facility (CEBAF) Large Acceptance Spectrometer (CLAS) at Jefferson Lab. Real photons produced with the Hall-B bremsstrahlung tagging system in the energy range from 0.50 to 1.55 GeV were incident on a cryogenic liquid ${}^3\mathrm{He}$ target. The differential cross sections for the $\gamma$ ${}^3\mathrm{He}$ $\to \pi {}^{+}t$ reaction were measured as a function of photon-beam energy and pion-scattering angle. Theoretical predictions to date cannot explain the large cross sections except at backward angles, showing that additional components must be added to the model.

Angular distributions of $\sigma \left(\theta \right),$ $A_y,$ ${\mathrm{iT}}_{11},$ $T_{20},$ $T_{21},$ and $T_{22}$ have been measured for $d-p$ scattering at $E_{\mathrm{c}.\mathrm{m}.\mathrm{}}=667\mathrm{}\mathrm{keV}.$ This set of high-precision data is compared to variational calculations with the nucleon-nucleon potential alone and also to calculations including a three-nucleon $\mathrm{}\left(3N\right)\mathrm{}$ potential. Agreement with cross section and tensor analyzing power data is excellent when a $3N$ potential is used. However, a comparison between the vector analyzing powers reveals differences of approximately 40% in the maxima of the angular distributions which is larger than reported at higher energies for both $p-d$ and $n-d$ scattering. The inclusion of phenomenological spin-orbit forces in a $3N$ potential improves the comparison with vector analyzing powers substantially. Single-energy phase-shift analyses were performed on this data set and a similar data set at $E_{\mathrm{c}.\mathrm{m}.\mathrm{}}=431.3\mathrm{}\mathrm{keV}.$ The role of the different phase-shift parameters in fitting these data is discussed.