The COMPASS Collaboration at CERN has investigated the pi(-)gamma -> pi(-)pi(-)pi(+) reaction at center-of-momentum energy below five pion masses, root s < 5m(pi), embedded in the Primakoff reaction of 190 GeV pions impinging on a lead target. Exchange of quasireal photons is selected by isolating the sharp Coulomb peak observed at smallest momentum transfers, t' < 0.001 GeV2/c(2). Using partial-wave analysis techniques, the scattering intensity of Coulomb production described in terms of chiral dynamics and its dependence on the 3 pi-invariant mass m(3 pi) = root s were extracted. The absolute cross section was determined in seven bins of root s with an overall precision of 20%. At leading order, the result is found to be in good agreement with the prediction of chiral perturbation theory over the whole energy range investigated.

First Measurement of Chiral Dynamics in π^{-}γ→π^{-}π^{-}π^{+}

AMOROSO, Antonio;BALESTRA, Ferruccio;BERTINI, Raimondo Pietro;CHIOSSO, Michela;GARFAGNINI, Raffaello;GNESI, IVAN;GRASSO, Antonino;PANZIERI, Daniele;PIRAGINO, Guido;SOSIO, Stefano;TAKEKAWA, STEFANO;
2012

Abstract

The COMPASS Collaboration at CERN has investigated the pi(-)gamma -> pi(-)pi(-)pi(+) reaction at center-of-momentum energy below five pion masses, root s < 5m(pi), embedded in the Primakoff reaction of 190 GeV pions impinging on a lead target. Exchange of quasireal photons is selected by isolating the sharp Coulomb peak observed at smallest momentum transfers, t' < 0.001 GeV2/c(2). Using partial-wave analysis techniques, the scattering intensity of Coulomb production described in terms of chiral dynamics and its dependence on the 3 pi-invariant mass m(3 pi) = root s were extracted. The absolute cross section was determined in seven bins of root s with an overall precision of 20%. At leading order, the result is found to be in good agreement with the prediction of chiral perturbation theory over the whole energy range investigated.
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192001-1
192001-6
PACS 12.39.Fe; PACS 13.60.Le; PACS 25.80.Dj
C. Adolph;M. G. Alekseev;V. Y. Alexakhin;Y. Alexandrov;G. D. Alexeev;A. Amoroso;A. A. Antonov;A. Austregesilo;B. Badelek;F. Balestra;J. Barth;G. Baum;Y. Bedfer;J. Bernhard;R. Bertini;M. Bettinelli;K. A. Bicker;R. Birsa;J. Bisplinghoff;P. Bordalo;F. Bradamante;C. Braun;A. Bravar;A. Bressan;E. Burtin;D. Chaberny;M. Chiosso;S. U. Chung;A. Cicuttin;M. L. Crespo;S. D. Torre;S. Das;S. S. Dasgupta;O. Y. Denisov;L. Dhara;S. V. Donskov;N. Doshita;V. Duic;W. Duennweber;M. Dziewiecki;A. Efremov;C. Elia;P. D. Eversheim;W. Eyrich;M. Faessler;A. Ferrero;A. Filin;M. Finger;J. F. M.;H. Fischer;C. Franco;N. d. Fresne;J. M. Friedrich;R. Garfagnini;F. Gautheron;O. P. Gavrichtchouk;R. Gazda;S. Gerassimov;R. Geyer;M. Giorgi;I. Gnesi;B. Gobbo;S. Goertz;S. Grabmueller;A. Grasso;B. Grube;R. Gushterski;A. Guskov;F. Haas;D. v. Harrach;T. Hasegawa;F. H. Heinsius;F. Herrmann;C. Hess;F. Hinterberger;N. Horikawa;C. Hoeppner;N. d'Hose;S. Huber;S. Ishimoto;O. Ivanov;Y. Ivanshin;T. Iwata;R. Jahn;P. Jasinski;G. Jegou;R. Joosten;E. Kabuss;D. Kang;B. Ketzer;G. V. Khaustov;Y. A. Khokhlov;Y. Kisselev;F. Klein;K. Klimaszewski;S. Koblitz;J. H. Koivuniemi;V. N. Kolosov;K. Kondo;K. Koenigsmann;I. Konorov;V. F. Konstantinov;A. Korzenev;A. M. Kotzinian;O. Kouznetsov;M. Kraemer;Z. V. Kroumchtein;F. Kunne;K. Kurek;L. Lauser;A. A. Lednev;A. Lehmann;S. Levorato;J. Lichtenstadt;A. Maggiora;A. Magnon;N. Makke;G. K. Mallot;A. Mann;C. Marchand;A. Martin;J. Marzec;F. Massmann;T. Matsuda;W. Meyer;T. Michigami;Y. V. Mikhailov;M. A. Moinester;A. Morreale;A. Mutter;A. Nagaytsev;T. Nagel;F. Nerling;S. Neubert;D. Neyret;V. I. Nikolaenko;W. . D.;A. S. Nunes;A. G. Olshevsky;M. Ostrick;A. Padee;R. Panknin;D. Panzieri;B. Parsamyan;S. Paul;E. Perevalova;G. Pesaro;D. V. Peshekhonov;G. Piragino;S. Platchkov;J. Pochodzalla;J. Polak;V. A. Polyakov;G. Pontecorvo;J. Pretz;C. Quintans;J. . F.;S. Ramos;V. Rapatsky;G. Reicherz;A. Richter;E. Rocco;E. Rondio;N. S. Rossiyskaya;D. I. Ryabchikov;V. D. Samoylenko;A. Sandacz;M. G. Sapozhnikov;S. Sarkar;I. A. Savin;G. Sbrizzai;P. Schiavon;C. Schill;T. Schlueter;L. Schmitt;K. Schoenning;S. Schopferer;W. Schroeder;O. Y. Shevchenko;H. . W.;L. Silva;L. Sinha;A. N. Sissakian;M. Slunecka;G. I. Smirnov;S. Sosio;F. Sozzi;A. Srnka;M. Stolarski;M. Sulc;R. Sulej;P. Sznajder;S. Takekawa;J. T. Wolbeek;S. Tessaro;F. Tessarotto;A. Teufel;L. G. Tkatchev;S. Uhl;I. Uman;M. Vandenbroucke;M. Virius;N. V. Vlassov;R. Windmolders;W. Wislicki;H. Wollny;K. Zaremba;M. Zavertyaev;E. Zemlyanichkina;M. Ziembicki;N. Zhuravlev;A. Zvyagin
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