Measurement of the charged-pion polarizability.
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.
Universität Erlangen-Nürnberg, Physikalisches Institut, 91054 Erlangen, Germany.
C
C
Adolph
Joint Institute for Nuclear Research, 141980 Dubna, Moscow Region, Russia.
R
R
Akhunzyanov
University of Turin, Department of Physics, 10125 Turin, Italy.
M G
MG
Alexeev
Joint Institute for Nuclear Research, 141980 Dubna, Moscow Region, Russia.
G D
GD
Alexeev
University of Turin, Department of Physics, 10125 Turin, Italy and Torino Section of INFN, 10125 Turin, Italy.
A
A
Amoroso
CEA IRFU/SPhN Saclay, 91191 Gif-sur-Yvette, France.
V
V
Andrieux
Joint Institute for Nuclear Research, 141980 Dubna, Moscow Region, Russia.
V
V
Anosov
CERN, 1211 Geneva 23, Switzerland and Technische Universität München, Physik Department, 85748 Garching, Germany.
A
A
Austregesilo
University of Warsaw, Faculty of Physics, 00-681 Warsaw, Poland.
B
B
Badełek
University of Turin, Department of Physics, 10125 Turin, Italy and Torino Section of INFN, 10125 Turin, Italy.
F
F
Balestra
Universität Bonn, Physikalisches Institut, 53115 Bonn, Germany.
J
J
Barth
Universität Bielefeld, Fakultät für Physik, 33501 Bielefeld, Germany.
G
G
Baum
Universität Bonn, Helmholtz-Institut für Strahlen- und Kernphysik, 53115 Bonn, Germany.
R
R
Beck
CEA IRFU/SPhN Saclay, 91191 Gif-sur-Yvette, France.
Y
Y
Bedfer
Universität Bochum, Institut für Experimentalphysik, 44780 Bochum, Germany.
A
A
Berlin
Universität Mainz, Institut für Kernphysik, 55099 Mainz, Germany.
J
J
Bernhard
CERN, 1211 Geneva 23, Switzerland and Technische Universität München, Physik Department, 85748 Garching, Germany.
K
K
Bicker
Universität Bonn, Physikalisches Institut, 53115 Bonn, Germany.
J
J
Bieling
Trieste Section of INFN, 34127 Trieste, Italy.
R
R
Birsa
Universität Bonn, Helmholtz-Institut für Strahlen- und Kernphysik, 53115 Bonn, Germany.
J
J
Bisplinghoff
Charles University in Prague, Faculty of Mathematics and Physics, 18000 Prague, Czech Republic.
M
M
Bodlak
CEA IRFU/SPhN Saclay, 91191 Gif-sur-Yvette, France.
M
M
Boer
LIP, 1000-149 Lisbon, Portugal.
P
P
Bordalo
University of Trieste, Department of Physics, 34127 Trieste, Italy and Trieste Section of INFN, 34127 Trieste, Italy.
F
F
Bradamante
Universität Erlangen-Nürnberg, Physikalisches Institut, 91054 Erlangen, Germany.
C
C
Braun
University of Trieste, Department of Physics, 34127 Trieste, Italy and Trieste Section of INFN, 34127 Trieste, Italy.
A
A
Bressan
Universität Freiburg, Physikalisches Institut, 79104 Freiburg, Germany.
M
M
Büchele
CEA IRFU/SPhN Saclay, 91191 Gif-sur-Yvette, France.
E
E
Burtin
CEA IRFU/SPhN Saclay, 91191 Gif-sur-Yvette, France.
L
L
Capozza
University of Turin, Department of Physics, 10125 Turin, Italy and Torino Section of INFN, 10125 Turin, Italy.
M
M
Chiosso
Technische Universität München, Physik Department, 85748 Garching, Germany.
S U
SU
Chung
Trieste Section of INFN, 34127 Trieste, Italy and Abdus Salam ICTP, 34151 Trieste, Italy.
A
A
Cicuttin
Torino Section of INFN, 10125 Turin, Italy.
M
M
Colantoni
Trieste Section of INFN, 34127 Trieste, Italy and Abdus Salam ICTP, 34151 Trieste, Italy.
M L
ML
Crespo
CEA IRFU/SPhN Saclay, 91191 Gif-sur-Yvette, France.
Q
Q
Curiel
Trieste Section of INFN, 34127 Trieste, Italy.
S
S
Dalla Torre
Matrivani Institute of Experimental Research & Education, Calcutta 700 030, India.
S S
SS
Dasgupta
Trieste Section of INFN, 34127 Trieste, Italy.
S
S
Dasgupta
Torino Section of INFN, 10125 Turin, Italy.
O Yu
OY
Denisov
Technische Universität München, Physik Department, 85748 Garching, Germany.
A M
AM
Dinkelbach
State Scientific Center Institute for High Energy Physics of National Research Center "Kurchatov Institute," 142281 Protvino, Russia.
S V
SV
Donskov
Yamagata University, Yamagata, 992-8510 Japan.
N
N
Doshita
University of Trieste, Department of Physics, 34127 Trieste, Italy.
V
V
Duic
Ludwig-Maximilians-Universität München, Department für Physik, 80799 Munich, Germany.
W
W
Dünnweber
Warsaw University of Technology, Institute of Radioelectronics, 00-665 Warsaw, Poland.
M
M
Dziewiecki
Joint Institute for Nuclear Research, 141980 Dubna, Moscow Region, Russia.
A
A
Efremov
University of Trieste, Department of Physics, 34127 Trieste, Italy and Trieste Section of INFN, 34127 Trieste, Italy.
C
C
Elia
Universität Bonn, Helmholtz-Institut für Strahlen- und Kernphysik, 53115 Bonn, Germany.
P D
PD
Eversheim
Universität Erlangen-Nürnberg, Physikalisches Institut, 91054 Erlangen, Germany.
W
W
Eyrich
Ludwig-Maximilians-Universität München, Department für Physik, 80799 Munich, Germany.
M
M
Faessler
CEA IRFU/SPhN Saclay, 91191 Gif-sur-Yvette, France.
A
A
Ferrero
State Scientific Center Institute for High Energy Physics of National Research Center "Kurchatov Institute," 142281 Protvino, Russia.
A
A
Filin
Charles University in Prague, Faculty of Mathematics and Physics, 18000 Prague, Czech Republic.
M
M
Finger
Charles University in Prague, Faculty of Mathematics and Physics, 18000 Prague, Czech Republic.
M
M
Finger
Universität Freiburg, Physikalisches Institut, 79104 Freiburg, Germany.
H
H
Fischer
LIP, 1000-149 Lisbon, Portugal.
C
C
Franco
CERN, 1211 Geneva 23, Switzerland and Universität Mainz, Institut für Kernphysik, 55099 Mainz, Germany.
N
N
du Fresne von Hohenesche
Technische Universität München, Physik Department, 85748 Garching, Germany.
J M
JM
Friedrich
CERN, 1211 Geneva 23, Switzerland.
V
V
Frolov
Universität Bochum, Institut für Experimentalphysik, 44780 Bochum, Germany.
F
F
Gautheron
Joint Institute for Nuclear Research, 141980 Dubna, Moscow Region, Russia.
O P
OP
Gavrichtchouk
Lebedev Physical Institute, 119991 Moscow, Russia and Technische Universität München, Physik Department, 85748 Garching, Germany.
S
S
Gerassimov
Ludwig-Maximilians-Universität München, Department für Physik, 80799 Munich, Germany.
R
R
Geyer
University of Turin, Department of Physics, 10125 Turin, Italy and Torino Section of INFN, 10125 Turin, Italy.
I
I
Gnesi
Trieste Section of INFN, 34127 Trieste, Italy.
B
B
Gobbo
Universität Bonn, Physikalisches Institut, 53115 Bonn, Germany.
S
S
Goertz
Universität Freiburg, Physikalisches Institut, 79104 Freiburg, Germany.
M
M
Gorzellik
Technische Universität München, Physik Department, 85748 Garching, Germany.
S
S
Grabmüller
University of Turin, Department of Physics, 10125 Turin, Italy and Torino Section of INFN, 10125 Turin, Italy.
A
A
Grasso
Technische Universität München, Physik Department, 85748 Garching, Germany.
B
B
Grube
Universität Freiburg, Physikalisches Institut, 79104 Freiburg, Germany.
T
T
Grussenmeyer
Joint Institute for Nuclear Research, 141980 Dubna, Moscow Region, Russia.
A
A
Guskov
Universität Freiburg, Physikalisches Institut, 79104 Freiburg, Germany.
T
T
Guthörl
Technische Universität München, Physik Department, 85748 Garching, Germany.
F
F
Haas
Universität Mainz, Institut für Kernphysik, 55099 Mainz, Germany.
D
D
von Harrach
Universität Bonn, Physikalisches Institut, 53115 Bonn, Germany.
D
D
Hahne
Yamagata University, Yamagata, 992-8510 Japan.
R
R
Hashimoto
Universität Freiburg, Physikalisches Institut, 79104 Freiburg, Germany.
F H
FH
Heinsius
Universität Freiburg, Physikalisches Institut, 79104 Freiburg, Germany.
F
F
Herrmann
Universität Bonn, Helmholtz-Institut für Strahlen- und Kernphysik, 53115 Bonn, Germany.
F
F
Hinterberger
Technische Universität München, Physik Department, 85748 Garching, Germany.
Ch
Ch
Höppner
Nagoya University, 464 Nagoya, Japan.
N
N
Horikawa
CEA IRFU/SPhN Saclay, 91191 Gif-sur-Yvette, France.
N
N
d'Hose
Technische Universität München, Physik Department, 85748 Garching, Germany.
S
S
Huber
Yamagata University, Yamagata, 992-8510 Japan.
S
S
Ishimoto
Joint Institute for Nuclear Research, 141980 Dubna, Moscow Region, Russia.
A
A
Ivanov
Joint Institute for Nuclear Research, 141980 Dubna, Moscow Region, Russia.
Yu
Y
Ivanshin
Yamagata University, Yamagata, 992-8510 Japan.
T
T
Iwata
Universität Bonn, Helmholtz-Institut für Strahlen- und Kernphysik, 53115 Bonn, Germany.
R
R
Jahn
Czech Technical University in Prague, 16636 Prague, Czech Republic.
V
V
Jary
Universität Mainz, Institut für Kernphysik, 55099 Mainz, Germany.
P
P
Jasinski
Universität Freiburg, Physikalisches Institut, 79104 Freiburg, Germany.
P
P
Jörg
Universität Bonn, Helmholtz-Institut für Strahlen- und Kernphysik, 53115 Bonn, Germany.
R
R
Joosten
Universität Mainz, Institut für Kernphysik, 55099 Mainz, Germany.
E
E
Kabuss
Technische Universität München, Physik Department, 85748 Garching, Germany.
B
B
Ketzer
State Scientific Center Institute for High Energy Physics of National Research Center "Kurchatov Institute," 142281 Protvino, Russia.
G V
GV
Khaustov
State Scientific Center Institute for High Energy Physics of National Research Center "Kurchatov Institute," 142281 Protvino, Russia.
Yu A
YA
Khokhlov
Joint Institute for Nuclear Research, 141980 Dubna, Moscow Region, Russia.
Yu
Y
Kisselev
Universität Bonn, Physikalisches Institut, 53115 Bonn, Germany.
F
F
Klein
National Centre for Nuclear Research, 00-681 Warsaw, Poland.
K
K
Klimaszewski
Universität Bochum, Institut für Experimentalphysik, 44780 Bochum, Germany.
J H
JH
Koivuniemi
State Scientific Center Institute for High Energy Physics of National Research Center "Kurchatov Institute," 142281 Protvino, Russia.
V N
VN
Kolosov
Yamagata University, Yamagata, 992-8510 Japan.
K
K
Kondo
Universität Freiburg, Physikalisches Institut, 79104 Freiburg, Germany.
K
K
Königsmann
Lebedev Physical Institute, 119991 Moscow, Russia and Technische Universität München, Physik Department, 85748 Garching, Germany.
I
I
Konorov
State Scientific Center Institute for High Energy Physics of National Research Center "Kurchatov Institute," 142281 Protvino, Russia.
V F
VF
Konstantinov
University of Turin, Department of Physics, 10125 Turin, Italy and Torino Section of INFN, 10125 Turin, Italy.
A M
AM
Kotzinian
Joint Institute for Nuclear Research, 141980 Dubna, Moscow Region, Russia.
O
O
Kouznetsov
Technische Universität München, Physik Department, 85748 Garching, Germany.
M
M
Krämer
Joint Institute for Nuclear Research, 141980 Dubna, Moscow Region, Russia.
Z V
ZV
Kroumchtein
Joint Institute for Nuclear Research, 141980 Dubna, Moscow Region, Russia.
N
N
Kuchinski
Technische Universität München, Physik Department, 85748 Garching, Germany.
R
R
Kuhn
CEA IRFU/SPhN Saclay, 91191 Gif-sur-Yvette, France.
F
F
Kunne
National Centre for Nuclear Research, 00-681 Warsaw, Poland.
K
K
Kurek
Warsaw University of Technology, Institute of Radioelectronics, 00-665 Warsaw, Poland.
R P
RP
Kurjata
State Scientific Center Institute for High Energy Physics of National Research Center "Kurchatov Institute," 142281 Protvino, Russia.
A A
AA
Lednev
Universität Erlangen-Nürnberg, Physikalisches Institut, 91054 Erlangen, Germany.
A
A
Lehmann
CEA IRFU/SPhN Saclay, 91191 Gif-sur-Yvette, France.
M
M
Levillain
Trieste Section of INFN, 34127 Trieste, Italy.
S
S
Levorato
Tel Aviv University, School of Physics and Astronomy, 69978 Tel Aviv, Israel.
J
J
Lichtenstadt
Torino Section of INFN, 10125 Turin, Italy.
A
A
Maggiora
CEA IRFU/SPhN Saclay, 91191 Gif-sur-Yvette, France.
A
A
Magnon
University of Trieste, Department of Physics, 34127 Trieste, Italy and Trieste Section of INFN, 34127 Trieste, Italy.
N
N
Makke
CERN, 1211 Geneva 23, Switzerland.
G K
GK
Mallot
CEA IRFU/SPhN Saclay, 91191 Gif-sur-Yvette, France.
C
C
Marchand
University of Trieste, Department of Physics, 34127 Trieste, Italy and Trieste Section of INFN, 34127 Trieste, Italy.
A
A
Martin
Warsaw University of Technology, Institute of Radioelectronics, 00-665 Warsaw, Poland.
J
J
Marzec
Charles University in Prague, Faculty of Mathematics and Physics, 18000 Prague, Czech Republic.
J
J
Matousek
Yamagata University, Yamagata, 992-8510 Japan.
H
H
Matsuda
University of Miyazaki, Miyazaki 889-2192, Japan.
T
T
Matsuda
Joint Institute for Nuclear Research, 141980 Dubna, Moscow Region, Russia.
G
G
Meshcheryakov
Universität Bochum, Institut für Experimentalphysik, 44780 Bochum, Germany.
W
W
Meyer
Yamagata University, Yamagata, 992-8510 Japan.
T
T
Michigami
State Scientific Center Institute for High Energy Physics of National Research Center "Kurchatov Institute," 142281 Protvino, Russia.
Yu V
YV
Mikhailov
Yamagata University, Yamagata, 992-8510 Japan.
Y
Y
Miyachi
Tel Aviv University, School of Physics and Astronomy, 69978 Tel Aviv, Israel.
M A
MA
Moinester
Joint Institute for Nuclear Research, 141980 Dubna, Moscow Region, Russia.
A
A
Nagaytsev
Technische Universität München, Physik Department, 85748 Garching, Germany.
T
T
Nagel
Universität Mainz, Institut für Kernphysik, 55099 Mainz, Germany.
F
F
Nerling
Technische Universität München, Physik Department, 85748 Garching, Germany.
S
S
Neubert
CEA IRFU/SPhN Saclay, 91191 Gif-sur-Yvette, France.
D
D
Neyret
State Scientific Center Institute for High Energy Physics of National Research Center "Kurchatov Institute," 142281 Protvino, Russia.
V I
VI
Nikolaenko
Czech Technical University in Prague, 16636 Prague, Czech Republic.
J
J
Novy
Universität Freiburg, Physikalisches Institut, 79104 Freiburg, Germany.
W-D
WD
Nowak
LIP, 1000-149 Lisbon, Portugal.
A S
AS
Nunes
Joint Institute for Nuclear Research, 141980 Dubna, Moscow Region, Russia.
A G
AG
Olshevsky
Joint Institute for Nuclear Research, 141980 Dubna, Moscow Region, Russia.
I
I
Orlov
Universität Mainz, Institut für Kernphysik, 55099 Mainz, Germany.
M
M
Ostrick
Universität Bonn, Physikalisches Institut, 53115 Bonn, Germany.
R
R
Panknin
University of Eastern Piedmont, 15100 Alessandria, Italy and Torino Section of INFN, 10125 Turin, Italy.
D
D
Panzieri
University of Turin, Department of Physics, 10125 Turin, Italy and Torino Section of INFN, 10125 Turin, Italy.
B
B
Parsamyan
Technische Universität München, Physik Department, 85748 Garching, Germany.
S
S
Paul
Joint Institute for Nuclear Research, 141980 Dubna, Moscow Region, Russia.
D
D
Peshekhonov
CEA IRFU/SPhN Saclay, 91191 Gif-sur-Yvette, France.
S
S
Platchkov
Universität Mainz, Institut für Kernphysik, 55099 Mainz, Germany.
J
J
Pochodzalla
State Scientific Center Institute for High Energy Physics of National Research Center "Kurchatov Institute," 142281 Protvino, Russia.
V A
VA
Polyakov
Universität Bonn, Physikalisches Institut, 53115 Bonn, Germany.
J
J
Pretz
LIP, 1000-149 Lisbon, Portugal.
M
M
Quaresma
LIP, 1000-149 Lisbon, Portugal.
C
C
Quintans
LIP, 1000-149 Lisbon, Portugal.
S
S
Ramos
Universität Freiburg, Physikalisches Institut, 79104 Freiburg, Germany.
C
C
Regali
Universität Bochum, Institut für Experimentalphysik, 44780 Bochum, Germany.
G
G
Reicherz
CERN, 1211 Geneva 23, Switzerland.
E
E
Rocco
Joint Institute for Nuclear Research, 141980 Dubna, Moscow Region, Russia.
N S
NS
Rossiyskaya
State Scientific Center Institute for High Energy Physics of National Research Center "Kurchatov Institute," 142281 Protvino, Russia.
D I
DI
Ryabchikov
Warsaw University of Technology, Institute of Radioelectronics, 00-665 Warsaw, Poland.
A
A
Rychter
State Scientific Center Institute for High Energy Physics of National Research Center "Kurchatov Institute," 142281 Protvino, Russia.
V D
VD
Samoylenko
National Centre for Nuclear Research, 00-681 Warsaw, Poland.
A
A
Sandacz
Matrivani Institute of Experimental Research & Education, Calcutta 700 030, India.
S
S
Sarkar
Joint Institute for Nuclear Research, 141980 Dubna, Moscow Region, Russia.
I A
IA
Savin
University of Trieste, Department of Physics, 34127 Trieste, Italy and Trieste Section of INFN, 34127 Trieste, Italy.
G
G
Sbrizzai
University of Trieste, Department of Physics, 34127 Trieste, Italy and Trieste Section of INFN, 34127 Trieste, Italy.
P
P
Schiavon
Universität Freiburg, Physikalisches Institut, 79104 Freiburg, Germany.
C
C
Schill
Ludwig-Maximilians-Universität München, Department für Physik, 80799 Munich, Germany.
T
T
Schlüter
Universität Freiburg, Physikalisches Institut, 79104 Freiburg, Germany.
K
K
Schmidt
Universität Bonn, Physikalisches Institut, 53115 Bonn, Germany.
H
H
Schmieden
CERN, 1211 Geneva 23, Switzerland.
K
K
Schönning
Universität Freiburg, Physikalisches Institut, 79104 Freiburg, Germany.
S
S
Schopferer
CERN, 1211 Geneva 23, Switzerland.
M
M
Schott
Joint Institute for Nuclear Research, 141980 Dubna, Moscow Region, Russia.
O Yu
OY
Shevchenko
LIP, 1000-149 Lisbon, Portugal.
L
L
Silva
Matrivani Institute of Experimental Research & Education, Calcutta 700 030, India.
L
L
Sinha
Universität Freiburg, Physikalisches Institut, 79104 Freiburg, Germany.
S
S
Sirtl
Joint Institute for Nuclear Research, 141980 Dubna, Moscow Region, Russia.
M
M
Slunecka
University of Turin, Department of Physics, 10125 Turin, Italy and Torino Section of INFN, 10125 Turin, Italy.
S
S
Sosio
Trieste Section of INFN, 34127 Trieste, Italy.
F
F
Sozzi
Institute of Scientific Instruments, AS CR, 61264 Brno, Czech Republic.
A
A
Srnka
Trieste Section of INFN, 34127 Trieste, Italy.
L
L
Steiger
LIP, 1000-149 Lisbon, Portugal.
M
M
Stolarski
Technical University in Liberec, 46117 Liberec, Czech Republic.
M
M
Sulc
National Centre for Nuclear Research, 00-681 Warsaw, Poland.
R
R
Sulej
Yamagata University, Yamagata, 992-8510 Japan.
H
H
Suzuki
National Centre for Nuclear Research, 00-681 Warsaw, Poland.
A
A
Szabelski
Universität Freiburg, Physikalisches Institut, 79104 Freiburg, Germany.
T
T
Szameitat
National Centre for Nuclear Research, 00-681 Warsaw, Poland.
P
P
Sznajder
University of Turin, Department of Physics, 10125 Turin, Italy and Torino Section of INFN, 10125 Turin, Italy.
S
S
Takekawa
Universität Freiburg, Physikalisches Institut, 79104 Freiburg, Germany.
J
J
ter Wolbeek
Trieste Section of INFN, 34127 Trieste, Italy.
S
S
Tessaro
Trieste Section of INFN, 34127 Trieste, Italy.
F
F
Tessarotto
CEA IRFU/SPhN Saclay, 91191 Gif-sur-Yvette, France.
F
F
Thibaud
Technische Universität München, Physik Department, 85748 Garching, Germany.
S
S
Uhl
Ludwig-Maximilians-Universität München, Department für Physik, 80799 Munich, Germany.
I
I
Uman
Czech Technical University in Prague, 16636 Prague, Czech Republic.
M
M
Virius
Universität Bochum, Institut für Experimentalphysik, 44780 Bochum, Germany.
L
L
Wang
Universität Mainz, Institut für Kernphysik, 55099 Mainz, Germany.
T
T
Weisrock
Universität Mainz, Institut für Kernphysik, 55099 Mainz, Germany.
M
M
Wilfert
Universität Bonn, Physikalisches Institut, 53115 Bonn, Germany.
R
R
Windmolders
CEA IRFU/SPhN Saclay, 91191 Gif-sur-Yvette, France.
H
H
Wollny
Warsaw University of Technology, Institute of Radioelectronics, 00-665 Warsaw, Poland.
K
K
Zaremba
Lebedev Physical Institute, 119991 Moscow, Russia.
M
M
Zavertyaev
Joint Institute for Nuclear Research, 141980 Dubna, Moscow Region, Russia.
E
E
Zemlyanichkina
Warsaw University of Technology, Institute of Radioelectronics, 00-665 Warsaw, Poland.
M
M
Ziembicki
Universität Erlangen-Nürnberg, Physikalisches Institut, 91054 Erlangen, Germany.
A
A
Zink