1. Measurement of the charged-pion polarizability.
- Author
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Adolph C, Akhunzyanov R, Alexeev MG, Alexeev GD, Amoroso A, Andrieux V, Anosov V, Austregesilo A, Badełek B, Balestra F, Barth J, Baum G, Beck R, Bedfer Y, Berlin A, Bernhard J, Bicker K, Bieling J, Birsa R, Bisplinghoff J, Bodlak M, Boer M, Bordalo P, Bradamante F, Braun C, Bressan A, Büchele M, Burtin E, Capozza L, Chiosso M, Chung SU, Cicuttin A, Colantoni M, Crespo ML, Curiel Q, Dalla Torre S, Dasgupta SS, Dasgupta S, Denisov OY, Dinkelbach AM, Donskov SV, Doshita N, Duic V, Dünnweber W, Dziewiecki M, Efremov A, Elia C, Eversheim PD, Eyrich W, Faessler M, Ferrero A, Filin A, Finger M Jr, Finger M, Fischer H, Franco C, du Fresne von Hohenesche N, Friedrich JM, Frolov V, Gautheron F, Gavrichtchouk OP, Gerassimov S, Geyer R, Gnesi I, Gobbo B, Goertz S, Gorzellik M, Grabmüller S, Grasso A, Grube B, Grussenmeyer T, Guskov A, Guthörl T, Haas F, von Harrach D, Hahne D, Hashimoto R, Heinsius FH, Herrmann F, Hinterberger F, Höppner Ch, Horikawa N, d'Hose N, Huber S, Ishimoto S, Ivanov A, Ivanshin Y, Iwata T, Jahn R, Jary V, Jasinski P, Jörg P, Joosten R, Kabuss E, Ketzer B, Khaustov GV, Khokhlov YA, Kisselev Y, Klein F, Klimaszewski K, Koivuniemi JH, Kolosov VN, Kondo K, Königsmann K, Konorov I, Konstantinov VF, Kotzinian AM, Kouznetsov O, Krämer M, Kroumchtein ZV, Kuchinski N, Kuhn R, Kunne F, Kurek K, Kurjata RP, Lednev AA, Lehmann A, Levillain M, Levorato S, Lichtenstadt J, Maggiora A, Magnon A, Makke N, Mallot GK, Marchand C, Martin A, Marzec J, Matousek J, Matsuda H, Matsuda T, Meshcheryakov G, Meyer W, Michigami T, Mikhailov YV, Miyachi Y, Moinester MA, Nagaytsev A, Nagel T, Nerling F, Neubert S, Neyret D, Nikolaenko VI, Novy J, Nowak WD, Nunes AS, Olshevsky AG, Orlov I, Ostrick M, Panknin R, Panzieri D, Parsamyan B, Paul S, Peshekhonov D, Platchkov S, Pochodzalla J, Polyakov VA, Pretz J, Quaresma M, Quintans C, Ramos S, Regali C, Reicherz G, Rocco E, Rossiyskaya NS, Ryabchikov DI, Rychter A, Samoylenko VD, Sandacz A, Sarkar S, Savin IA, Sbrizzai G, Schiavon P, Schill C, Schlüter T, Schmidt K, Schmieden H, Schönning K, Schopferer S, Schott M, Shevchenko OY, Silva L, Sinha L, Sirtl S, Slunecka M, Sosio S, Sozzi F, Srnka A, Steiger L, Stolarski M, Sulc M, Sulej R, Suzuki H, Szabelski A, Szameitat T, Sznajder P, Takekawa S, ter Wolbeek J, Tessaro S, Tessarotto F, Thibaud F, Uhl S, Uman I, Virius M, Wang L, Weisrock T, Wilfert M, Windmolders R, Wollny H, Zaremba K, Zavertyaev M, Zemlyanichkina E, Ziembicki M, and Zink A
- Abstract
The COMPASS collaboration at CERN has investigated pion Compton scattering, π(-)γ→π(-)γ, at center-of-mass energy below 3.5 pion masses. The process is embedded in the reaction π(-)Ni→π(-)γNi, which is initiated by 190 GeV pions impinging on a nickel target. The exchange of quasireal photons is selected by isolating the sharp Coulomb peak observed at smallest momentum transfers, Q(2)<0.0015 (GeV/c)(2). From a sample of 63,000 events, the pion electric polarizability is determined to be α(π)=(2.0±0.6(stat)±0.7(syst))×10(-4) fm(3) under the assumption α(π)=-β(π), which relates the electric and magnetic dipole polarizabilities. It is the most precise measurement of this fundamental low-energy parameter of strong interaction that has been addressed since long by various methods with conflicting outcomes. While this result is in tension with previous dedicated measurements, it is found in agreement with the expectation from chiral perturbation theory. An additional measurement replacing pions by muons, for which the cross-section behavior is unambiguously known, was performed for an independent estimate of the systematic uncertainty.
- Published
- 2015
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