- QWeak Collaboration;
- Androic, D;
- Armstrong, DS;
- Asaturyan, A;
- Bartlett, K;
- Beminiwattha, RS;
- Benesch, J;
- Benmokhtar, F;
- Birchall, J;
- Carlini, RD;
- Christy, ME;
- Cornejo, JC;
- Dusa, S Covrig;
- Dalton, MM;
- Davis, CA;
- Deconinck, W;
- Dowd, JF;
- Dunne, JA;
- Dutta, D;
- Duvall, WS;
- Elassar, M;
- Falk, WR;
- Finn, JM;
- Forest, T;
- Gal, C;
- Gaskell, D;
- Gericke, MTW;
- Gray, VM;
- Guo, F;
- Hoskins, JR;
- Jones, DC;
- Kargiantoulakis, M;
- King, PM;
- Korkmaz, E;
- Kowalski, S;
- Leacock, J;
- Leckey, JP;
- Lee, AR;
- Lee, JH;
- Lee, L;
- MacEwan, S;
- Mack, D;
- Magee, JA;
- Mahurin, R;
- Mammei, J;
- Martin, JW;
- McHugh, MJ;
- Meekins, D;
- Mesick, KE;
- Michaels, R;
- Mkrtchyan, A;
- Mkrtchyan, H;
- Narayan, A;
- Ndukum, LZ;
- Nuruzzaman;
- Nelyubin, V;
- van Oers, WTH;
- Owen, VF;
- Page, SA;
- Pan, J;
- Paschke, KD;
- Phillips, SK;
- Pitt, ML;
- Radloff, RW;
- Rajotte, JF;
- Ramsay, WD;
- Roche, J;
- Sawatzky, B;
- Seva, T;
- Shabestari, MH;
- Silwal, R;
- Simicevic, N;
- Smith, GR;
- Solvignon, P;
- Spayde, DT;
- Subedi, A;
- Subedi, R;
- Tadevosyan, V;
- Tobias, WA;
- Waidyawansa, B;
- Wang, P;
- Wells, SP;
- Wood, SA;
- Zang, P;
- Zhamkochyan, S
We report measurements of the parity-conserving beam-normal single-spin
elastic scattering asymmetries $B_n$ on $^{12}$C and $^{27}$Al, 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 $B_n$ on $^{12}$C and provide a first measurement on $^{27}$Al.
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
degrees, and the average $Q^2$ for both targets was 0.02437 GeV$^2$ (Q=0.1561
GeV). The asymmetries are $B_n$ = -10.68 $\pm$ 0.90 stat) $\pm$ 0.57 (syst) ppm
for $^{12}$C and $B_n$ = -12.16 $\pm$ 0.58 (stat) $\pm$ 0.62 (syst) ppm for
$^{27}$Al. 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 (theta < 10 degrees) data from $^{1}$H to $^{27}$Al can be
described by the same slope out to $Q \approx 0.35$ GeV. Larger-angle data from
other experiments in the same Q range are consistent with a slope about twice
as steep.