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5 results on '"MAMI-A1"'

1. A new measurement of the structure functions $P_{LL}-P_{TT}/epsilon$ and $P_{LT}$ in virtual Compton scattering at $Q^2=$ 0.33 (GeV/c)$^2$

Author

Collaboration, The MAMI-A1, Janssens, P., Doria, L., Achenbach, P., Gayoso, C. Ayerbe, Baumann, D., Bernauer, J. C., Bensafa, I. K., Böhm, R., Bosnar, D., Burtin, E., D'Hose, N., Defaÿ, X., Ding, M., Distler, M. O., Fonvieille, H., Friedrich, J., Friedrich, J. M., Laveissière, G., Makek, M., Marroncle, J., Merkel, H., Müller, U., Nungesser, L., Pasquini, B., Pochodzalla, J., Postavaru, O., Potokar, M., Ryckbosch, D., Majos, S. Sanchez, Schlimme, B. S., Seimetz, M., Širca, S., Tamas, G., Van de Vyver, R., Van Hoorebeke, L., Van Overloop, A., Walcher, Th., Weinriefer, M., Collaboration, The MAMI-A1, Janssens, P., Doria, L., Achenbach, P., Gayoso, C. Ayerbe, Baumann, D., Bernauer, J. C., Bensafa, I. K., Böhm, R., Bosnar, D., Burtin, E., D'Hose, N., Defaÿ, X., Ding, M., Distler, M. O., Fonvieille, H., Friedrich, J., Friedrich, J. M., Laveissière, G., Makek, M., Marroncle, J., Merkel, H., Müller, U., Nungesser, L., Pasquini, B., Pochodzalla, J., Postavaru, O., Potokar, M., Ryckbosch, D., Majos, S. Sanchez, Schlimme, B. S., Seimetz, M., Širca, S., Tamas, G., Van de Vyver, R., Van Hoorebeke, L., Van Overloop, A., Walcher, Th., and Weinriefer, M.

Abstract

The cross section of the $ep \to e' p' \gamma$ reaction has been measured at $Q^2 = 0.33$ (GeV/c)$^2$. The experiment was performed using the electron beam of the MAMI accelerator and the standard detector setup of the A1 Collaboration. The cross section is analyzed using the low-energy theorem for virtual Compton scattering, yielding a new determination of the two structure functions $P_LL}-P_{TT}/epsilon$ and $P_{LT}$ which are linear combinations of the generalized polarizabilities of the proton. We find somewhat larger values than in the previous investigation at the same $Q^2$. This difference, however, is purely due to our more refined analysis of the data. The results tend to confirm the non-trivial $Q^2$-evolution of the generalized polarizabilities and call for more measurements in the low-$Q^2$ region ($\le$ 1 (GeV/c)$^2$)., Comment: 9 pages, 10 figures. EPJA version. slight revisions in the text and figures

Published
2008
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2. A new measurement of the structure functions $P_{LL}-P_{TT}/epsilon$ and $P_{LT}$ in virtual Compton scattering at $Q^2=$ 0.33 (GeV/c)$^2$

Author

Collaboration, The MAMI-A1, Janssens, P., Doria, L., Achenbach, P., Gayoso, C. Ayerbe, Baumann, D., Bernauer, J. C., Bensafa, I. K., Böhm, R., Bosnar, D., Burtin, E., D'Hose, N., Defaÿ, X., Ding, M., Distler, M. O., Fonvieille, H., Friedrich, J., Friedrich, J. M., Laveissière, G., Makek, M., Marroncle, J., Merkel, H., Müller, U., Nungesser, L., Pasquini, B., Pochodzalla, J., Postavaru, O., Potokar, M., Ryckbosch, D., Majos, S. Sanchez, Schlimme, B. S., Seimetz, M., Širca, S., Tamas, G., Van de Vyver, R., Van Hoorebeke, L., Van Overloop, A., Walcher, Th., Weinriefer, M., Collaboration, The MAMI-A1, Janssens, P., Doria, L., Achenbach, P., Gayoso, C. Ayerbe, Baumann, D., Bernauer, J. C., Bensafa, I. K., Böhm, R., Bosnar, D., Burtin, E., D'Hose, N., Defaÿ, X., Ding, M., Distler, M. O., Fonvieille, H., Friedrich, J., Friedrich, J. M., Laveissière, G., Makek, M., Marroncle, J., Merkel, H., Müller, U., Nungesser, L., Pasquini, B., Pochodzalla, J., Postavaru, O., Potokar, M., Ryckbosch, D., Majos, S. Sanchez, Schlimme, B. S., Seimetz, M., Širca, S., Tamas, G., Van de Vyver, R., Van Hoorebeke, L., Van Overloop, A., Walcher, Th., and Weinriefer, M.

Abstract

The cross section of the $ep \to e' p' \gamma$ reaction has been measured at $Q^2 = 0.33$ (GeV/c)$^2$. The experiment was performed using the electron beam of the MAMI accelerator and the standard detector setup of the A1 Collaboration. The cross section is analyzed using the low-energy theorem for virtual Compton scattering, yielding a new determination of the two structure functions $P_LL}-P_{TT}/epsilon$ and $P_{LT}$ which are linear combinations of the generalized polarizabilities of the proton. We find somewhat larger values than in the previous investigation at the same $Q^2$. This difference, however, is purely due to our more refined analysis of the data. The results tend to confirm the non-trivial $Q^2$-evolution of the generalized polarizabilities and call for more measurements in the low-$Q^2$ region ($\le$ 1 (GeV/c)$^2$)., Comment: 9 pages, 10 figures. EPJA version. slight revisions in the text and figures

Published
2008
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3. Beam-helicity asymmetry in photon and pion electroproduction in the Delta(1232) resonance region at Q^2= 0.35 (GeV/c)^2

Author

Collaboration, the MAMI-A1, Bensafa, I. K., Achenbach, P., Antelo, M. Ases, Ayerbe, C., Baumann, D., Böhm, R., Bosnar, D., Burtin, E., Defaÿ, X., D'Hose, N., Ding, M., Distler, M. O., Doria, L., Fonvieille, H., Friedrich, J. M., Friedrich, J., Llongo, J. Garcia, Janssens, P., Manas, G. Jover, Kohl, M., Laveissiere, G., Lloyd, M., Makek, M., Marroncle, J., Merkel, H., Merle, P., Müller, U., Nungesser, L., Pasquini, B., Benito, R. Perez, Pochodzalla, J., Potokar, M., Rosner, G., Majos, S. Sanchez, Seimetz, M., Sirca, S., Spitzenberg, T., Tamas, G., Van de Vyver, R., Van Hoorebeke, L., Walcher, Th., Weis, M., Collaboration, the MAMI-A1, Bensafa, I. K., Achenbach, P., Antelo, M. Ases, Ayerbe, C., Baumann, D., Böhm, R., Bosnar, D., Burtin, E., Defaÿ, X., D'Hose, N., Ding, M., Distler, M. O., Doria, L., Fonvieille, H., Friedrich, J. M., Friedrich, J., Llongo, J. Garcia, Janssens, P., Manas, G. Jover, Kohl, M., Laveissiere, G., Lloyd, M., Makek, M., Marroncle, J., Merkel, H., Merle, P., Müller, U., Nungesser, L., Pasquini, B., Benito, R. Perez, Pochodzalla, J., Potokar, M., Rosner, G., Majos, S. Sanchez, Seimetz, M., Sirca, S., Spitzenberg, T., Tamas, G., Van de Vyver, R., Van Hoorebeke, L., Walcher, Th., and Weis, M.

Abstract

The beam-helicity asymmetry has been measured simultaneously for the reactions (e p \to e p \gamma) and (e p \to e p \pi^0) in the $\Delta (1232)$ resonance region at $Q^2=$ 0.35 (GeV/c)$^2$. The experiment was performed at MAMI with a longitudinally polarized beam and an out-of-plane detection of the proton. The results are compared with calculations based on Dispersion Relations for virtual Compton scattering and with the MAID model for pion electroproduction. There is an overall good agreement between experiment and theoretical calculations. The remaining discrepancies may be ascribed to an imperfect parametrization of some $\gamma^{(*)} N \to \pi N$ multipoles, mainly contributing to the non-resonant background. The beam-helicity asymmetry in both channels ($\gamma$ and $\pi^0$) shows a good sensitivity to these multipoles and should allow future improvement in their parametrization., Comment: 7 pages, 8 figures, version to appear in EPJA

Published
2006
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4. Beam-helicity asymmetry in photon and pion electroproduction in the Delta(1232) resonance region at Q^2= 0.35 (GeV/c)^2

Author

Collaboration, the MAMI-A1, Bensafa, I. K., Achenbach, P., Antelo, M. Ases, Ayerbe, C., Baumann, D., Böhm, R., Bosnar, D., Burtin, E., Defaÿ, X., D'Hose, N., Ding, M., Distler, M. O., Doria, L., Fonvieille, H., Friedrich, J. M., Friedrich, J., Llongo, J. Garcia, Janssens, P., Manas, G. Jover, Kohl, M., Laveissiere, G., Lloyd, M., Makek, M., Marroncle, J., Merkel, H., Merle, P., Müller, U., Nungesser, L., Pasquini, B., Benito, R. Perez, Pochodzalla, J., Potokar, M., Rosner, G., Majos, S. Sanchez, Seimetz, M., Sirca, S., Spitzenberg, T., Tamas, G., Van de Vyver, R., Van Hoorebeke, L., Walcher, Th., Weis, M., Collaboration, the MAMI-A1, Bensafa, I. K., Achenbach, P., Antelo, M. Ases, Ayerbe, C., Baumann, D., Böhm, R., Bosnar, D., Burtin, E., Defaÿ, X., D'Hose, N., Ding, M., Distler, M. O., Doria, L., Fonvieille, H., Friedrich, J. M., Friedrich, J., Llongo, J. Garcia, Janssens, P., Manas, G. Jover, Kohl, M., Laveissiere, G., Lloyd, M., Makek, M., Marroncle, J., Merkel, H., Merle, P., Müller, U., Nungesser, L., Pasquini, B., Benito, R. Perez, Pochodzalla, J., Potokar, M., Rosner, G., Majos, S. Sanchez, Seimetz, M., Sirca, S., Spitzenberg, T., Tamas, G., Van de Vyver, R., Van Hoorebeke, L., Walcher, Th., and Weis, M.

Abstract

The beam-helicity asymmetry has been measured simultaneously for the reactions (e p \to e p \gamma) and (e p \to e p \pi^0) in the $\Delta (1232)$ resonance region at $Q^2=$ 0.35 (GeV/c)$^2$. The experiment was performed at MAMI with a longitudinally polarized beam and an out-of-plane detection of the proton. The results are compared with calculations based on Dispersion Relations for virtual Compton scattering and with the MAID model for pion electroproduction. There is an overall good agreement between experiment and theoretical calculations. The remaining discrepancies may be ascribed to an imperfect parametrization of some $\gamma^{(*)} N \to \pi N$ multipoles, mainly contributing to the non-resonant background. The beam-helicity asymmetry in both channels ($\gamma$ and $\pi^0$) shows a good sensitivity to these multipoles and should allow future improvement in their parametrization., Comment: 7 pages, 8 figures, version to appear in EPJA

Published
2006
Full Text
View/download PDF

5. Beam-helicity asymmetry in photon and pion electroproduction in the Delta(1232) resonance region at Q^2= 0.35 (GeV/c)^2

Author

Collaboration, the MAMI-A1, Bensafa, I. K., Achenbach, P., Antelo, M. Ases, Ayerbe, C., Baumann, D., Böhm, R., Bosnar, D., Burtin, E., Defaÿ, X., D'Hose, N., Ding, M., Distler, M. O., Doria, L., Fonvieille, H., Friedrich, J. M., Friedrich, J., Llongo, J. Garcia, Janssens, P., Manas, G. Jover, Kohl, M., Laveissiere, G., Lloyd, M., Makek, M., Marroncle, J., Merkel, H., Merle, P., Müller, U., Nungesser, L., Pasquini, B., Benito, R. Perez, Pochodzalla, J., Potokar, M., Rosner, G., Majos, S. Sanchez, Seimetz, M., Sirca, S., Spitzenberg, T., Tamas, G., Van de Vyver, R., Van Hoorebeke, L., Walcher, Th., Weis, M., Collaboration, the MAMI-A1, Bensafa, I. K., Achenbach, P., Antelo, M. Ases, Ayerbe, C., Baumann, D., Böhm, R., Bosnar, D., Burtin, E., Defaÿ, X., D'Hose, N., Ding, M., Distler, M. O., Doria, L., Fonvieille, H., Friedrich, J. M., Friedrich, J., Llongo, J. Garcia, Janssens, P., Manas, G. Jover, Kohl, M., Laveissiere, G., Lloyd, M., Makek, M., Marroncle, J., Merkel, H., Merle, P., Müller, U., Nungesser, L., Pasquini, B., Benito, R. Perez, Pochodzalla, J., Potokar, M., Rosner, G., Majos, S. Sanchez, Seimetz, M., Sirca, S., Spitzenberg, T., Tamas, G., Van de Vyver, R., Van Hoorebeke, L., Walcher, Th., and Weis, M.

Abstract

The beam-helicity asymmetry has been measured simultaneously for the reactions (e p \to e p \gamma) and (e p \to e p \pi^0) in the $\Delta (1232)$ resonance region at $Q^2=$ 0.35 (GeV/c)$^2$. The experiment was performed at MAMI with a longitudinally polarized beam and an out-of-plane detection of the proton. The results are compared with calculations based on Dispersion Relations for virtual Compton scattering and with the MAID model for pion electroproduction. There is an overall good agreement between experiment and theoretical calculations. The remaining discrepancies may be ascribed to an imperfect parametrization of some $\gamma^{(*)} N \to \pi N$ multipoles, mainly contributing to the non-resonant background. The beam-helicity asymmetry in both channels ($\gamma$ and $\pi^0$) shows a good sensitivity to these multipoles and should allow future improvement in their parametrization., Comment: 7 pages, 8 figures, version to appear in EPJA

Published
2006
Full Text
View/download PDF

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