Patients (pts) presenting to the emergency department (ED) with a primary diagnosis of atrial fibrillation (AF) are often admitted. To reduce hospitalizations, ED cardioversion (CV) protocols are often used. We propose an alternative protocol to discharge stable pts to a specialized AF clinic within

Polarisation-dependent differential cross sections σT associated with the target asymmetry T have been measured for the reaction γp→→pπ0 with transverse target polarisation from π0 threshold to photon energies of 190 MeV. The data were obtained using a frozen-spin butanol target with the Crystal Ball / TAPS detector set-up and the Glasgow photon tagging system at the Mainz Microtron MAMI. Results for σT have been used in combination with our previous measurements of the unpolarised cross section σ0 and the beam asymmetry Σ for a model-independent determination of S- and P-wave multipoles in the π0 threshold region, which includes for the first time a direct determination of the imaginary part of the E0+ multipole.

New results are reported from a measurement of π^{0} electroproduction near threshold using the p(e,e^{'}p)π^{0} reaction. The experiment was designed to determine precisely the energy dependence of s- and p-wave electromagnetic multipoles as a stringent test of the predictions of chiral perturbation theory (ChPT). The data were taken with an electron beam energy of 1192 MeV using a two-spectrometer setup in Hall A at Jefferson Lab. For the first time, complete coverage of the ϕ_{π}^{*} and θ_{π}^{*} angles in the pπ^{0} center of mass was obtained for invariant energies above threshold from 0.5 up to 15 MeV. The 4-momentum transfer Q^{2} coverage ranges from 0.05 to 0.155 (GeV/c)^{2} in fine steps. A simple phenomenological analysis of our data shows strong disagreement with p-wave predictions from ChPT for Q^{2}>0.07 (GeV/c)^{2}, while the s-wave predictions are in reasonable agreement.

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The low $Q^2$ slopes of the the transition form factors provide a unique method to measure the sizes of the neutral pseudo-scalar mesons, since they do not have electromagnetic form factors. From the slope one obtains the"axial transition RMS radius"$ R_{PS,A} = \sqrt{}$ for each PS meson. The present status of theory and experiment for these quantities are presented. A comparison of the $ R_{PS,A}$ is presented along with the electromagnetic and scalar radii of the $\pi^{\pm}$ mesons and the proton. We observe the striking similarity of the values of axial transition radii of all of the pseudoscalar mesons to each other and to the charge radius of the $\pi^{\pm}$. In the $Q^2$ = 0 limit the transition form factor is a measure of the pseudo-scalar meson radiative width (lifetime) and is a possible fourth (unexploited) method to perform such a measurement. The $\pi^{0} \rightarrow \gamma \gamma$ decay rate is a test of QCD at the confinement scale. There is a firm QCD prediction with a theoretical uncertainty of $\simeq $ 1 \% which calls for an experimental test at the same level of accuracy. There are three methods that have been utilized to perform this measurement and the present status of the experimental tests are outlined. The current accuracy is significantly less than the theoretical uncertainty. The efforts to improve this are briefly summarized.

C. Mertz, C. Vellidis, R. Alarcon, D.H. Barkhuff, A.M. Bernstein, W. Bertozzi, V. Burkert, J. Chen, J.R. Comfort, G. Dodson, S. Dolfini, K. Dow, M. Farkhondeh, J.M. Finn, S. Gilad, R.W. Gothe, X. Jiang, K. Joo, N.I. Kaloskamis, A. Karabarbounis, J.J. Kelly, S. Kowalski, C. Kunz, R.W. Lourie, J.I. McIntyre, B.D. Milbrath, R. Miskimen, J.H. Mitchell, C.N. Papanicolas, C.F. Perdrisat, A.J. Sarty, J. Shaw, S.-B. Soong, D. Tieger, C. Tschalær, W. Turchinetz, P.E. Ulmer, S. Van Verst, G.A. Warren, L.B. Weinstein, S. Williamson, R.J. Woo, A. Young Department of Physics and Astronomy, Arizona State University, Tempe, Arizona 85287 Institute of Accelerating Systems and Applications and Department of Physics, University of Athens, Athens, Greece Institute for Nuclear and Particle Physics and Department of Physics, University of Virginia, Charlottesville, Virginia 22901 Department of Physics, Laboratory for Nuclear Science and Bates Accelerator Center, Massachusetts Institute of Technology,

We report new p(e, e′p) π ° measurements in the Δ + (1232) resonance at the low momentum transfer region utilizing the magnetic spectrometers of the A1 Collaboration at MAMI. The mesonic cloud dynamics are predicted to be dominant and appreciably changing in this region while the momentum transfer is sufficiently low to be able to test chiral effective field theory calculations. The results disagree with predictions of constituent quark models and are in reasonable agreement with dynamical calculations with pion cloud effects, chiral effective field theory and lattice calculations. The reported measurements suggest that improvement is required to the theoretical calculations and provide valuable input that will allow their refinements.

A fundamental property of QCD is the presence of the chiral anomaly, which is the dominant component of the pi(0) -> gamma gamma decay rate. Based on this anomaly and its small (similar or equal to 4.5%) chiral correction, a prediction of the pi(0) lifetime can be used as a test of QCD at confinement scale energies. The interesting experimental and theoretical histories of the pi(0) meson are reviewed, from discovery to the present era. Experimental results are in agreement with the theoretical prediction, within the current (similar or equal to 3%) experimental error; however, they are not yet sufficiently precise to test the chiral corrected result, which is a firm QCD prediction and is known to similar or equal to 1% uncertainty. At this level there exist experimental inconsistencies, which require attention. Possible future work to improve the present precision is suggested. DOI: 10.1103/RevModPhys.85.49

A precision measurement of the differential cross sections $d\sigma/d\Omega$ and the linearly polarized photon asymmetry $\Sigma \equiv (d\sigma_\perp - d\sigma_\parallel) \slash (d\sigma_\perp + d\sigma_\parallel)$ for the $\vec{\gamma} p \rightarrow \pi^0p$ reaction in the near-threshold region has been performed with a tagged photon beam and almost $4\pi$ detector at the Mainz Microtron. The Glasgow-Mainz photon tagging facility along with the Crystal Ball/TAPS multi-photon detector system and a cryogenic liquid hydrogen target were used. These data allowed for a precise determination of the energy dependence of the real parts of the $S$- and all three $P$-wave amplitudes for the first time and provide the most stringent test to date of the predictions of Chiral Perturbation Theory and its energy region of agreement with experiment.

A precision measurement of the differential cross sections d sigma/d Omega and the linearly polarized photon asymmetry Sigma equivalent to (d alpha(perpendicular to) - d sigma(parallel to))/(d alpha(perpendicular to) + d sigma(parallel to) for the (gamma) over right arrowp -> pi(0) p reaction in the near-threshold region has been performed with a tagged photon beam and almost 4 pi detector at the Mainz Microtron. The Glasgow-Mainz photon tagging facility along with the Crystal Ball/TAPS multiphoton detector system and a cryogenic liquid hydrogen target were used. These data allowed for a precise determination of the energy dependence of the real parts of the S- and all three P-wave amplitudes for the first time and provide the most stringent test to date of the predictions of chiral perturbation theory and its energy region of agreement with experiment.

With the availability of the new neutral pion photoproduction from the proton data from the A2 and CB-TAPS Collaborations at Mainz it is mandatory to revisit Heavy Baryon Chiral Perturbation Theory (HBChPT) and address the extraction of the partial waves as well as other issues such as the value of the low-energy constants, the energy range where the calculation provides a good agreement with the data and the impact of unitarity. We find that, within the current experimental status, HBChPT with the fitted LECs gives a good agreement with the existing neutral pion photoproduction data up to ∼170 MeV and that imposing unitarity does not improve this picture. Above this energy the data call for further improvement in the theory such as the explicit inclusion of the Δ(1232). We also find that data and multipoles can be well described up to ∼185 MeV with Taylor expansions in the partial waves up to first order in pion energy.

Small angle electron scattering with intense electron beams opens up the possibility of performing almost real photon induced reactions with thin, polarized hydrogen and few body targets, allowing for the detection of low energy charged particles.This promises to be much more effective than conventional photon tagging techniques. For photo-pion reactions some fundamental new possibilities include: tests of charge symmetry in the N-N system by measurement of the neutron-neutron scattering length ann in the γD→ π+nn reaction; tests of isospin breaking due to the mass difference of the up and down quarks; measurements with polarized targets are sensitive to πN phase shifts and will test the validity of the Fermi-Watson (final state interaction) theorem. All of these experiments will test the accuracy and energy region of validity of chiral effective theories.

A precision measurement of the differential cross sections dσ/dΩ and the linearly polarized photon asymmetry Σ≡(dσ⊥-dσ∥)/(dσ⊥+dσ∥) for the γp→π0p reaction in the near-threshold region has been performed with a tagged photon beam and almost 4π detector at the Mainz Microtron. The Glasgow-Mainz photon tagging facility along with the Crystal Ball/TAPS multiphoton detector system and a cryogenic liquid hydrogen target were used. These data allowed for a precise determination of the energy dependence of the real parts of the S- and all three P-wave amplitudes for the first time and provide the most stringent test to date of the predictions of chiral perturbation theory and its energy region of agreement with experiment.

A precision measurement of the differential cross sections dσ/dΩ and the linearly polarized photon asymmetry Σ≡ (dσ_⊥ - dσ_∥) (dσ_⊥ + dσ_∥) for the γ⃗ p →π^0p reaction in the near-threshold region has been performed with a tagged photon beam and almost 4π detector at the Mainz Microtron. The Glasgow-Mainz photon tagging facility along with the Crystal Ball/TAPS multi-photon detector system and a cryogenic liquid hydrogen target were used. These data allowed for a precise determination of the energy dependence of the real parts of the S- and all three P-wave amplitudes for the first time and provide the most stringent test to date of the predictions of Chiral Perturbation Theory and its energy region of agreement with experiment.

D. Hornidge, ∗ P. Aguar Bartolomé, J. R. M. Annand, H. J. Arends, R. Beck, V. Bekrenev, H. Berghäuser, A. M. Bernstein, A. Braghieri, W. J. Briscoe, S. Cherepnya, M. Dieterle, E. J. Downie, P. Drexler, C. Fernández-Ramı́rez, L. V. Filkov, D. I. Glazier, P. Hall Barrientos, E. Heid, M. Hilt, I. Jaegle, O. Jahn, T. C. Jude, V. L. Kashevarov, 2 I. Keshelashvili, R. Kondratiev, M. Korolija, A. Koulbardis, D. Krambrich, S. Kruglov, B. Krusche, A. T. Laffoley, V. Lisin, K. Livingston, I. J. D. MacGregor, J. Mancell, D. M. Manley, E. F. McNicoll, D. Mekterovic, V. Metag, S. Micanovic, D. G. Middleton, 2 K. W. Moores, A. Mushkarenkov, B. M. K. Nefkens, M. Oberle, M. Ostrick, P. B. Otte, B. Oussena, P. Pedroni, F. Pheron, A. Polonski, S. Prakhov, J. Robinson, T. Rostomyan, S. Scherer, S. Schumann, M. H. Sikora, A. Starostin, I. Supek, M. Thiel, A. Thomas, L. Tiator, M. Unverzagt, D. P. Watts, D. Werthmüller, and L. Witthauer

High precision measurements of the differential cross sections for π0 photoproduction at forward angles for two nuclei, 12C and 208Pb, have been performed for incident photon energies of 4.9-5.5 GeV to extract the π0→γγ decay width. The experiment was done at Jefferson Lab using the Hall B photon tagger and a high-resolution multichannel calorimeter. The π0→γγ decay width was extracted by fitting the measured cross sections using recently updated theoretical models for the process. The resulting value for the decay width is Γ(π0→γγ)=7.82±0.14(stat)±0.17(syst)  eV. With the 2.8% total uncertainty, this result is a factor of 2.5 more precise than the current Particle Data Group average of this fundamental quantity, and it is consistent with current theoretical predictions.