The Heavy Photon Search experiment took its first data in a 2015 engineering run using a 1.056 GeV, 50 nA electron beam provided by CEBAF at the Thomas Jefferson National Accelerator Facility, searching for an electro-produced dark photon. Using 1.7 days (1170 nb$^{-1}$) of data, a search for a resonance in the $e^{+}e^{-}$ invariant mass distribution between 19 and 81 MeV/c$^{2}$ showed no evidence of dark photon decays above the large QED background, confirming earlier searches and demonstrating the full functionality of the experiment. Upper limits on the square of the coupling of the dark photon to the Standard Model photon are set at the level of 6$\times$10$^{-6}$. In addition, a search for displaced dark photon decays did not rule out any territory but resulted in a reliable analysis procedure that will probe hitherto unexplored parameter space with future, higher luminosity runs.

Differential cross sections for Compton scattering from the proton have been measured at scattering angles of 55°, 90°, and 125° in the laboratory frame using quasimonoenergetic linearly (circularly) polarized photon beams with a weighted mean energy value of 83.4 MeV (81.3 MeV). These measurements were performed at the High Intensity Gamma-Ray Source facility at the Triangle Universities Nuclear Laboratory. The results are compared to previous measurements and are interpreted in the chiral effective field theory framework to extract the electromagnetic dipole polarizabilities of the proton, which gives α_{E1}^{p}=13.8±1.2_{stat}±0.1_{BSR}±0.3_{theo},β_{M1}^{p}=0.2∓1.2_{stat}±0.1_{BSR}∓0.3_{theo} in units of 10^{-4}  fm^{3}.

We present new precision measurements of the elastic electron-proton scattering cross section for momentum transfer (Q^{2}) up to 15.75  (GeV/c)^{2}. Combined with existing data, these provide an improved extraction of the proton magnetic form factor at high Q^{2} and double the range over which a longitudinal or transverse separation of the cross section can be performed. The difference between our results and polarization data agrees with that observed at lower Q^{2} and attributed to hard two-photon exchange (TPE) effects, extending to 8  (GeV/c)^{2} the range of Q^{2} for which a discrepancy is established at >95% confidence. We use the discrepancy to quantify the size of TPE contributions needed to explain the cross section at high Q^{2}.

We report high-precision measurements of the Deeply Virtual Compton Scattering (DVCS) cross section at high values of the Bjorken variable x_B. DVCS is sensitive to the Generalized Parton Distributions of the nucleon, which provide a three-dimensional description of its internal constituents. Using the exact analytic expression of the DVCS cross section for all possible polarization states of the initial and final electron and nucleon, and final state photon, we present the first experimental extraction of all four helicity-conserving Compton Form Factors (CFFs) of the nucleon as a function of x_B, while systematically including helicity flip amplitudes. In particular, the high accuracy of the present data demonstrates sensitivity to some very poorly known CFFs.

We report measurements of the exclusive neutral pion electroproduction cross section off protons at large values of x_{B} (0.36, 0.48, and 0.60) and Q^{2} (3.1 to 8.4  GeV^{2}) obtained from Jefferson Lab Hall A experiment E12-06-014. The corresponding structure functions dσ_{T}/dt+εdσ_{L}/dt, dσ_{TT}/dt, dσ_{LT}/dt, and dσ_{LT^{'}}/dt are extracted as a function of the proton momentum transfer t-t_{min}. The results suggest the amplitude for transversely polarized virtual photons continues to dominate the cross section throughout this kinematic range. The data are well described by calculations based on transversity generalized parton distributions coupled to a helicity flip distribution amplitude of the pion, thus providing a unique way to probe the structure of the nucleon.

Differential cross sections for elastic Compton scattering from $^4$He have been measured with high statistical precision at the High Intensity $\gamma$-ray Source at laboratory scattering angles of $55^\circ$, $90^\circ$, and $125^\circ$ using a quasi-monoenergetic photon beam with a weighted mean energy value of $81.3$ MeV. The results are compared to previous measurements and similar fore-aft asymmetry in the angular distribution of the differential cross sections is observed. This experimental work is expected to strongly motivate the development of effective-field-theory calculations of Compton scattering from $^4$He to fully interpret the data.

The Compton scattering cross section from He-4 has been measured with high statistical accuracy over a scattering angle range of 40 degrees-159 degrees using a quasimonoenergetic 61-MeV photon beam at the High Intensity Gamma-Ray Source. The data are interpreted using a phenomenological model sensitive to the dipole isoscalar electromagnetic polarizabilities (alpha(s) and beta(s)) of the nucleon. These data can be fit with the model using values of alpha(s) and beta(s) that are consistent with the currently accepted values. These data will serve as benchmarks of future calculations from effective field theories and lattice quantum chromodynamics.

S. Riordan, 2, 3 S. Abrahamyan, B. Craver, A. Kelleher, A. Kolarkar, J. Miller, G.D. Cates, N. Liyanage, B. Wojtsekhowski, ∗ A. Acha, K. Allada, B. Anderson, K.A. Aniol, J.R.M. Annand, J. Arrington, T. Averett, A. Beck, 8 M. Bellis, W. Boeglin, H. Breuer, J.R. Calarco, A. Camsonne, J.P. Chen, E. Chudakov, L. Coman, B. Crowe, F. Cusanno, D. Day, P. Degtyarenko, P.A.M. Dolph, C. Dutta, C. Ferdi, C. Fernández-Ramı́rez, R. Feuerbach, 5 L.M. Fraile, G. Franklin, S. Frullani, S. Fuchs, F. Garibaldi, N. Gevorgyan, R. Gilman, 8 A. Glamazdin, J. Gomez, K. Grimm, J.-O. Hansen, J.L. Herraiz, D.W. Higinbotham, R. Holmes, T. Holmstrom, D. Howell, C.W. de Jager, X. Jiang, M.K. Jones, J. Katich, L.J. Kaufman, M. Khandaker, J.J. Kelly, † D. Kiselev, W. Korsch, J. LeRose, R. Lindgren, P. Markowitz, D.J. Margaziotis, S. May-Tal Beck, 8 S. Mayilyan, K. McCormick, Z.-E. Meziani, R. Michaels, B. Moffit, S. Nanda, V. Nelyubin, T. Ngo, D.M. Nikolenko, B. Norum, L. Pentchev, C.F. Perdrisat, E. Piasetzky, R. Pomatsalyuk, D. Protopopescu, A.J.R. Puckett, V.A. Punjabi, X. Qian, Y. Qiang, B. Quinn, I. Rachek, R.D. Ransome, P.E. Reimer, B. Reitz, J. Roche, G. Ron, O. Rondon, G. Rosner, A. Saha, M.M. Sargsian, B. Sawatzky, J. Segal, M. Shabestari, A. Shahinyan, Yu. Shestakov, J. Singh, S. Širca, P. Souder, S. Stepanyan, V. Stibunov, V. Sulkosky, S. Tajima, W.A. Tobias, J.M. Udias, G.M. Urciuoli, B. Vlahovic, H. Voskanyan, K. Wang, F.R. Wesselmann, J.R. Vignote, S.A. Wood, J. Wright, H. Yao, and X. Zhu

The electric form factor of the neutron was determined from studies of the reaction 3 He ! ð ~e; e 0 n Þ pp in quasielastic kinematics in Hall A at Jefferson Lab. Longitudinally polarized electrons were scattered off a polarized target in which the nuclear polarization was oriented perpendicular to the momentum transfer. The scattered electrons were detected in a magnetic spectrometer in coincidence with neutrons that were registered in a large-solid-angle detector. More than doubling the Q 2 range over which it is known, we find G nE ¼ 0 : 0236 (cid:1) 0 : 0017 ð stat Þ (cid:1) 0 : 0026 ð syst Þ , 0 : 0208 (cid:1) 0 : 0024 (cid:1) 0 : 0019 , and 0 : 0147 (cid:1) 0 : 0020 (cid:1) 0 : 0014 for Q 2 ¼ 1 : 72 , 2.48, and 3 : 41 GeV 2 , respectively.

The electric form factor of the neutron was determined from studies of the reaction 3He(e,e'n)pp in quasielastic kinematics in Hall A at Jefferson Lab. Longitudinally polarized electrons were scattered off a polarized target in which the nuclear polarization was oriented perpendicular to the momentum transfer. The scattered electrons were detected in a magnetic spectrometer in coincidence with neutrons that were registered in a large-solid-angle detector. More than doubling the Q2 range over which it is known, we find G(E)(n)=0.0236±0.0017(stat)±0.0026(syst), 0.0208±0.0024±0.0019, and 0.0147±0.0020±0.0014 for Q(2)=1.72, 2.48, and 3.41 GeV2, respectively.

Return to work (RTW) and other treatment outcomes of coronary artery bypass graft (CABG) and percutaneous transluminal coronary angioplasty (PTCA) patients were compared. Consecutive patients at one centre (n = 112 CABG and 119 PTCA patients) were interviewed 6-18 months following treatment (groups were similar in sex and social class). Pre-treatment employment levels were similar (41 and 38% for CABG and PTCA groups, respectively). PTCA patients were more likely to smoke, have angina, have less advanced cardiovascular disease and have been advised to stop working for medical reasons pre-treatment. Post-treatment levels of employment increased significantly. RTW rates were similar for CABG and PTCA groups (59 and 68% respectively). Both groups had reduced smoking to similar levels. The PTCA group continued to have higher levels of angina. For those without angina, PTCA patients were significantly more likely to return to work (73 vs 55%, P < 0.01). Both CABG and PTCA resulted in increased employment post-treatment.

Three dimensional body surface maps provide more information on the gee-spatial distribution of cardiac elactrieal activity.It is hypo thesised that this information could facilitate the diagnosis of acute MI in early cases where standard methods are equivocal.To date these techniques have been confined to the laboratory and have yet to find clinical application.An important first step is the assessment of their diagnostic value among patients with established MI.All 82 consecutive patients admitted to the RVH cardiac unit with first presentation ofchastpaln suggestive of MI were mapped at 24 hours using a Corazonix BSM-32 predieter which measured QRS and STT iso-lntegrals using 32 leads.Of the 82 patients, 57 (69.5%) had an initial diagnostic ECG with subsequent confirmatory enzyme elevation.A further 25 (30.5%)presented with nondiagnostic ECG f'mdings.Fifteen of this group had an MI as confirmed by an increase in cardiac enzymes.For comparative purposes, 54 consols were recruited and mapped, all with normal ECG and no IHD risk factors.A series of discriminant function analyses were performed to assess sensitivity and specificity.Using a subset of the 32 QRS and the 32 STT iso-integralmeasurements, selected by a stepwise forward algorithm, a sensitivity of 94.7% (54/57) and a specificity of 90.7% (49/54) was obtained.When all measurements were analysed together, better results were obtained: sensitivity 10070 (57]57) and specificity 96.3 (42/ 54).In further multivariate analysis, map topography differed significantly (p<< 0.01) between males and females.Separating the data according to sex and using all QRS and sTr iso-integral measurements, 100% specificity and sensitivity resulted.Despite these findings, each of the derived discriminam functions had difficulty in classifying the 25 cases belonging to the possible MI group.The best results obtainable were: a sensitivity of 60% and a specificity of 60%.This suggests that further analysis is required to identify the topography of these patients.