/ hep-ex CERN-PH-EP-2014-041 arXiv:1403.2644


Measurement of radiative widths of $a_2(1320)$ and $\pi_2(1670)$


Adolph, C. (Erlangen - Nuremberg U.) ; Akhunzyanov, R. (Dubna, JINR) ; Alekseev, M.G. (INFN, Trieste) ; Alexeev, G.D. (Dubna, JINR) ; Amoroso, A. (INFN, Turin) ; Andrieux, V. (DAPNIA, Saclay) ; Anosov, V. (Dubna, JINR) ; Austregesilo, A. (Munich, Tech. U.) ; Badelek, B. (Warsaw U.) ; Balestra, F. (INFN, Turin) ; Barth, J. (Bonn U.) ; Baum, G. (Bielefeld U.) ; Beck, R. (Bonn U., HISKP) ; Bedfer, Y. (DAPNIA, Saclay) ; Berlin, A. (Ruhr U., Bochum) ; Bernhard, J. (Mainz U., Inst. Kernphys.) ; Bicker, K. (Munich, Tech. U.) ; Bieling, J. (Bonn U.) ; Birsa, R. (INFN, Trieste) ; Bisplinghoff, J. (Bonn U., HISKP) ; Bodlak, M. (Charles U.) ; Boer, M. (DAPNIA, Saclay) ; Bordalo, P. (Lisbon, IST (main)) ; Bradamante, F. (CERN) ; Braun, C. (Erlangen - Nuremberg U.) ; Bressan, A. (INFN, Trieste) ; Buchele, M. (Freiburg U.) ; Burtin, E. (DAPNIA, Saclay) ; Capozza, L. (DAPNIA, Saclay) ; Chiosso, M. (INFN, Turin) ; Chung, S.U. (Brookhaven) ; Cicuttin, A. (INFN, Trieste) ; Crespo, M.L. (INFN, Trieste) ; Curiel, Q. (DAPNIA, Saclay) ; Dalla Torre, S. (INFN, Trieste) ; Dasgupta, S.S. (Matrivani Inst., Calcutta) ; Dasgupta, S. (INFN, Trieste) ; Denisov, O.Yu. (INFN, Turin) ; Donskov, S.V. (Kurchatov Inst., Moscow) ; Doshita, N. (Yamagata U.) ; Duic, V. (Trieste U.) ; Dunnweber, W. (Munich U.) ; Dziewiecki, M. (Warsaw U. of Tech.) ; Efremov, A. (Dubna, JINR) ; Elia, C. (INFN, Trieste) ; Eversheim, P.D. (Bonn U., HISKP) ; Eyrich, W. (Erlangen - Nuremberg U.) ; Faessler, M. (Munich U.) ; Ferrero, A. (DAPNIA, Saclay) ; Filin, A. (Kurchatov Inst., Moscow) ; Finger, M. (Charles U.) ; Finger jr, M. (Charles U.) ; Fischer, H. (Freiburg U.) ; Franco, C. (LIP, Lisbon) ; du Fresne von Hohenesche, N. (CERN) ; Friedrich, J.M. (Munich, Tech. U.) ; Frolov, V. (CERN) ; Gautheron, F. (Ruhr U., Bochum) ; Gavrichtchouk, O.P. (Dubna, JINR) ; Gerassimov, S. (Munich, Tech. U.) ; Geyer, R. (Munich U.) ; Gnesi, I. (INFN, Turin) ; Gobbo, B. (INFN, Trieste) ; Goertz, S. (Bonn U.) ; Gorzellik, M. (Freiburg U.) ; Grabmuller, S. (Munich, Tech. U.) ; Grasso, A. (INFN, Turin) ; Grube, B. (Munich, Tech. U.) ; Guskov, A. (Dubna, JINR) ; Guthorl, T. (Freiburg U.) ; Haas, F. (Munich, Tech. U.) ; von Harrach, D. (Mainz U., Inst. Kernphys.) ; Hahne, D. (Bonn U.) ; Hashimoto, R. (Yamagata U.) ; Heinsius, F.H. (Freiburg U.) ; Herrmann, F. (Freiburg U.) ; Hinterberger, F. (Bonn U., HISKP) ; Hoppner, Ch. (Munich, Tech. U.) ; Horikawa, N. (Chubu U.) ; d'Hose, N. (DAPNIA, Saclay) ; Huber, S. (Munich, Tech. U.) ; Ishimoto, S. (KEK, Tsukuba) ; Ivanov, A. (Dubna, JINR) ; Ivanshin, Yu. (Dubna, JINR) ; Iwata, T. (Yamagata U.) ; Jahn, R. (Bonn U., HISKP) ; Jary, V. (Prague, Tech. U.) ; Jasinski, P. (Mainz U., Inst. Kernphys.) ; Jorg, P. (Freiburg U.) ; Joosten, R. (Bonn U., HISKP) ; Kabuss, E. (Mainz U., Inst. Kernphys.) ; Ketzer, B. (Munich, Tech. U.) ; Khaustov, G.V. (Kurchatov Inst., Moscow) ; Khokhlov, Yu. A. (Moscow, MIPT) ; Kisselev, Yu. (Dubna, JINR) ; Klein, F. (Bonn U.) ; Klimaszewski, K. (Warsaw, Inst. Nucl. Studies) ; Koivuniemi, J.H. (Ruhr U., Bochum) ; Kolosov, V.N. (Kurchatov Inst., Moscow) ; Kondo, K. (Yamagata U.) ; Konigsmann, K. (Freiburg U.) ; Konorov, I. (Munich, Tech. U.) ; Konstantinov, V.F. (Kurchatov Inst., Moscow) ; Kotzinian, A.M. (INFN, Turin) ; Kouznetsov, O. (Dubna, JINR) ; Kral, Z. (Prague, Tech. U.) ; Kramer, M. (Munich, Tech. U.) ; Kroumchtein, Z.V. (Dubna, JINR) ; Kuchinski, N. (Dubna, JINR) ; Kunne, F. (DAPNIA, Saclay) ; Kurek, K. (Warsaw, Inst. Nucl. Studies) ; Kurjata, R.P. (Warsaw U. of Tech.) ; Lednev, A.A. (Kurchatov Inst., Moscow) ; Lehmann, A. (Erlangen - Nuremberg U.) ; Levorato, S. (INFN, Trieste) ; Lichtenstadt, J. (Tel Aviv U.) ; Maggiora, A. (INFN, Turin) ; Magnon, A. (DAPNIA, Saclay) ; Makke, N. (INFN, Trieste) ; Mallot, G.K. (CERN) ; Marchand, C. (DAPNIA, Saclay) ; Martin, A. (INFN, Trieste) ; Marzec, J. (Warsaw U. of Tech.) ; Matousek, J. (Charles U.) ; Matsuda, H. (Yamagata U.) ; Matsuda, T. (Miyazaki U.) ; Meshcheryakov, G. (Dubna, JINR) ; Meyer, W. (Ruhr U., Bochum) ; Michigami, T. (Yamagata U.) ; Mikhailov, Yu. V. (Kurchatov Inst., Moscow) ; Miyachi, Y. (Yamagata U.) ; Nagaytsev, A. (Dubna, JINR) ; Nagel, T. (Munich, Tech. U.) ; Nerling, F. (Freiburg U.) ; Neubert, S. (Munich, Tech. U.) ; Neyret, D. (DAPNIA, Saclay) ; Nikolaenko, V.I. (Kurchatov Inst., Moscow) ; Novy, J. (Prague, Tech. U.) ; Nowak, W.D. (Freiburg U.) ; Nunes, A.S. (LIP, Lisbon) ; Orlov, I. (Dubna, JINR) ; Olshevsky, A.G. (Dubna, JINR) ; Ostrick, M. (Mainz U., Inst. Kernphys.) ; Panknin, R. (Bonn U.) ; Panzieri, D. (INFN, Turin) ; Parsamyan, B. (INFN, Turin) ; Paul, S. (Munich, Tech. U.) ; Pesek, M. (Charles U.) ; Platchkov, S. (DAPNIA, Saclay) ; Pochodzalla, J. (Mainz U., Inst. Kernphys.) ; Polyakov, V.A. (Kurchatov Inst., Moscow) ; Pretz, J. (Aachen, Tech. Hochsch.) ; Quaresma, M. (LIP, Lisbon) ; Quintans, C. (LIP, Lisbon) ; Ramos, S. (Lisbon, IST (main)) ; Reicherz, G. (Ruhr U., Bochum) ; Rocco, E. (CERN) ; Rychter, A. (Warsaw U. of Tech.) ; Rossiyskaya, N.S. (Dubna, JINR) ; Ryabchikov, D.I. (Kurchatov Inst., Moscow) ; Samoylenko, V.D. (Kurchatov Inst., Moscow) ; Sandacz, A. (Warsaw, Inst. Nucl. Studies) ; Sarkar, S. (Matrivani Inst., Calcutta) ; Savin, I.A. (Dubna, JINR) ; Sbrizzai, G. (INFN, Trieste) ; Schiavon, P. (INFN, Trieste) ; Schill, C. (Freiburg U.) ; Schluter, T. (Munich U.) ; Schmidt, A. (Erlangen - Nuremberg U.) ; Schmidt, K. (Freiburg U.) ; Schmieden, H. (Bonn U., HISKP) ; Schonning, K. (CERN) ; Schopferer, S. (Freiburg U.) ; Schott, M. (CERN) ; Shevchenko, O.Yu. (Dubna, JINR) ; Silva, L. (LIP, Lisbon) ; Sinha, L. (Matrivani Inst., Calcutta) ; Sirtl, S. (Freiburg U.) ; Slunecka, M. (Dubna, JINR) ; Sosio, S. (INFN, Turin) ; Sozzi, F. (INFN, Trieste) ; Srnka, A. (Inst. Sci. Instruments, Brno) ; Steiger, L. (INFN, Trieste) ; Stolarski, M. (LIP, Lisbon) ; Sulc, M. (Liberec Tech. U.) ; Sulej, R. (Warsaw, Inst. Nucl. Studies) ; Suzuki, H. (Chubu U.) ; Szabelski, A. (Warsaw, Inst. Nucl. Studies) ; Szameitat, T. (Freiburg U.) ; Sznajder, P. (Warsaw, Inst. Nucl. Studies) ; Takekawa, S. (INFN, Turin) ; ter Wolbeek, J. (Freiburg U.) ; Tessaro, S. (INFN, Trieste) ; Tessarotto, F. (INFN, Trieste) ; Thibaud, F. (DAPNIA, Saclay) ; Uhl, S. (Munich, Tech. U.) ; Uman, I. (Munich U.) ; Vandenbroucke, M. (DAPNIA, Saclay) ; Virius, M. (Prague, Tech. U.) ; Vondra, J. (Prague, Tech. U.) ; Wang, L. (Ruhr U., Bochum) ; Weisrock, T. (Mainz U., Inst. Kernphys.) ; Wilfert, M. (Mainz U., Inst. Kernphys.) ; Windmolders, R. (Bonn U.) ; Wollny, H. (DAPNIA, Saclay) ; Zaremba, K. (Warsaw U. of Tech.) ; Zavertyaev, M. (Lebedev Inst.) ; Zemlyanichkina, E. (Dubna, JINR) ; Ziembicki, M. (Warsaw U. of Tech.)

Pages: 27

Abstract: The COMPASS Collaboration at CERN has investigated the reaction $\pi^- \gamma \rightarrow \pi^-\pi^-\pi^+$ embedded in the Primakoff reaction of $190~\textrm{GeV}$ pions scattering in the Coulomb field of a lead target, $\pi^- \text{Pb} \rightarrow \pi^-\pi^-\pi^+ \text{Pb}$. Exchange of quasi-real photons is selected by isolating the sharp Coulomb peak observed at momentum transfer below $0.001~(\text{GeV}/c)^2$. Using a partial-wave analysis the amplitudes and relative phases of the $a_2(1320)$ and $\pi_2(1670)$ mesons have been extracted, and the Coulomb and the diffractive contributions have been disentangled. Measuring absolute production cross sections we have determined the radiative width of the $a_2(1320)$ to be $\Gamma_0(a_2(1320) \rightarrow \pi\gamma) = (358 \pm 6_{\textrm{stat}} \pm 42_{\textrm{syst}})~\textrm{keV}$. As the first measurement, $\Gamma_0(\pi_2(1670) \rightarrow \pi\gamma) = (181 \pm 11_{\textrm{stat}} \pm 27_{\textrm{syst}})~\textrm{keV} \cdot (\textrm{BR}^{\textrm{PDG}}_{f_2 \pi}/\textrm{BR}_{f_2 \pi})$ is obtained for the radiative width of the $\pi_2(1670)$, where in this analysis the branching ratio $\textrm{BR}^{\textrm{PDG}}_{f_2 \pi}=0.56$ has been used. We compare these values to previous measurements and theoretical predictions.

Web-Page: http://inspirehep.net/record/1285361/files/fig1.png; http://inspirehep.net/record/1285361/files/fig10.png; http://inspirehep.net/record/1285361/files/fig11a.png; http://inspirehep.net/record/1285361/files/fig11b.png; http://inspirehep.net/record/1285361/files/fig12a.png; http://inspirehep.net/record/1285361/files/fig12b.png; http://inspirehep.net/record/1285361/files/fig12c.png; http://inspirehep.net/record/1285361/files/fig12d.png; http://inspirehep.net/record/1285361/files/fig2.png; http://inspirehep.net/record/1285361/files/fig3.png; http://inspirehep.net/record/1285361/files/fig4a.png; http://inspirehep.net/record/1285361/files/fig4b.png; http://inspirehep.net/record/1285361/files/fig5.png; http://inspirehep.net/record/1285361/files/fig6a.png; http://inspirehep.net/record/1285361/files/fig6b.png; http://inspirehep.net/record/1285361/files/fig6c.png; http://inspirehep.net/record/1285361/files/fig6d.png; http://inspirehep.net/record/1285361/files/fig6e.png; http://inspirehep.net/record/1285361/files/fig6f.png; http://inspirehep.net/record/1285361/files/fig7a.png; http://inspirehep.net/record/1285361/files/fig7b.png; http://inspirehep.net/record/1285361/files/fig7c.png; http://inspirehep.net/record/1285361/files/fig7d.png; http://inspirehep.net/record/1285361/files/fig7e.png; http://inspirehep.net/record/1285361/files/fig7f.png; http://inspirehep.net/record/1285361/files/fig8a.png; http://inspirehep.net/record/1285361/files/fig8b.png; http://inspirehep.net/record/1285361/files/fig9a.png; http://inspirehep.net/record/1285361/files/fig9b.png; http://inspirehep.net/record/1285361/files/arXiv:1403.2644.pdf


Note: 27 pages, 12 figures and 3 tables

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