The COMPASS experiment at the CERN SPS has studied the diffractive dissociation of negative pions into the π−π−π+ 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′ between 0.1 and 1 GeV2/c2. The well-known resonances a1(1260), a2(1320), and π2(1670) are clearly observed. In addition, the data show a significant natural-parity exchange production of a resonance with spin-exotic quantum numbers JPC=1−+ at 1.66 GeV/c2 decaying to ρπ. The resonant nature of this wave is evident from the mass-dependent phase differences to the JPC=2−+ and 1++ waves. From a mass-dependent fit a resonance mass of (1660±10+0−64) MeV/c2 and a width of (269±21+42−64) MeV/c2 are deduced, with an intensity of (1.7±0.2)% of the total intensity.
Observation of a J(PC)=1(-+) Exotic Resonance in Diffractive Dissociation of 190 GeV/c pi(-) into pi(-)pi(-)pi(+) RID D-4627-2011
PANZIERI, Daniele;
2010-01-01
Abstract
The COMPASS experiment at the CERN SPS has studied the diffractive dissociation of negative pions into the π−π−π+ 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′ between 0.1 and 1 GeV2/c2. The well-known resonances a1(1260), a2(1320), and π2(1670) are clearly observed. In addition, the data show a significant natural-parity exchange production of a resonance with spin-exotic quantum numbers JPC=1−+ at 1.66 GeV/c2 decaying to ρπ. The resonant nature of this wave is evident from the mass-dependent phase differences to the JPC=2−+ and 1++ waves. From a mass-dependent fit a resonance mass of (1660±10+0−64) MeV/c2 and a width of (269±21+42−64) MeV/c2 are deduced, with an intensity of (1.7±0.2)% of the total intensity.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
