Observation of a J{sup PC}=1{sup -+} Exotic Resonance in Diffractive Dissociation of 190 GeV/c {pi}{sup -} into {pi}{sup -{pi}-{pi}+}

• Published in: Physical review letters Vol. 104; no. 24
• Main Authors: Alekseev, M. G., Colantoni, M., Denisov, O. Yu, Maggiora, A., Alexakhin, V. Yu, Alexeev, G. D., Efremov, A., Finger, M. Jr, Gavrichtchouk, O. P., Gushterski, R., Guskov, A., Ivanov, O., Ivanshin, Yu, Komissarov, E. V., Kroumchtein, Z. V., Maximov, A. N., Nagaytsev, A., Olshevsky, A. G., Perevalova, E., Peshekhonov, D. V.
• Format: Journal Article
• Language: English
• Published: United States 18-06-2010
• Subjects: A1-1260 MESONS; A2-1320 MESONS; ACCELERATORS; ANGULAR MOMENTUM; AXIAL VECTOR MESONS; BARYONS; BEAMS; BOSONS; CERN SPS SYNCHROTRON; CYCLIC ACCELERATORS; ELEMENTARY PARTICLES; ENERGY RANGE; EXOTIC RESONANCES; FERMIONS; GEV RANGE; HADRONS; HYPERONS; MATHEMATICAL MODELS; MESON BEAMS; MESONS; MEV RANGE; MOMENTUM TRANSFER; MULTIPERIPHERAL MODEL; PARTIAL WAVES; PARTICLE BEAMS; PARTICLE MODELS; PARTICLE PRODUCTION; PARTICLE PROPERTIES; PERIPHERAL MODELS; PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; PI2-1670 MESONS; PION BEAMS; PIONS; PIONS MINUS; PIONS PLUS; PSEUDOSCALAR MESONS; QUANTUM NUMBERS; RESONANCE PARTICLES; SIGMA BARYONS; SIGMA-1660 BARYONS; SPIN; STRANGE PARTICLES; SYNCHROTRONS; TENSOR MESONS
• ISSN: 0031-9007; 1079-7114
• DOI: 10.1103/PHYSREVLETT.104.241803

The COMPASS experiment at the CERN SPS has studied the diffractive dissociation of negative pions into the {pi}{sup -{pi}-{pi}+} final state using a 190 GeV/c pion beam hitting a lead target. A partial wave analysis has been performed on a sample of 420 000 events taken at values of the squared 4-momentum transfer t{sup '} between 0.1 and 1 GeV{sup 2}/c{sup 2}. The well-known resonances a{sub 1}(1260), a{sub 2}(1320), and {pi}{sub 2}(1670) are clearly observed. In addition, the data show a significant natural-parity exchange production of a resonance with spin-exotic quantum numbers J{sup PC}=1{sup -+} at 1.66 GeV/c{sup 2} decaying to {rho}{pi}. The resonant nature of this wave is evident from the mass-dependent phase differences to the J{sup PC}=2{sup -+} and 1{sup ++} waves. From a mass-dependent fit a resonance mass of (1660{+-}10{sub -64}{sup +0}) MeV/c{sup 2} and a width of (269{+-}21{sub -64}{sup +42}) MeV/c{sup 2} are deduced, with an intensity of (1.7{+-}0.2)% of the total intensity.