The COMPASS Collaboration at CERN has measured diffractive dissociation of 190  GeV/c pions into the π−π−π+ final state using a stationary hydrogen target. A partial-wave analysis (PWA) was performed in bins of 3π mass and four-momentum transfer using the isobar model and the so far largest PWA model consisting of 88 waves. A narrow peak is observed in the f0(980)π channel with spin, parity and C-parity quantum numbers JPC=1++. We present a resonance-model study of a subset of the spin-density matrix selecting 3π states with JPC=2++ and 4++ decaying into ρ(770)π and with JPC=1++ decaying into f0(980)π. We identify a new a1 meson with mass (1414+15−13)  MeV/c2 and width (153+8−23)  MeV/c2. Within the final states investigated in our analysis, we observe the new a1(1420) decaying only into f0(980)π, suggesting its exotic nature.

Observation of a New Narrow Axial-Vector Mesona1(1420)

BRADAMANTE, FRANCO;BRESSAN, Andrea
;
DALLA TORRE, SILVIA;DASGUPTA, SHUDDHA SHANKAR;DUIC, VENICIO;LEVORATO, STEFANO;Makke, Nour;MARTIN, ANNA;MATOUSEK, JAN;SBRIZZAI, GIULIO;SOZZI, FEDERICA;TAKEKAWA, STEFANO;
2015

Abstract

The COMPASS Collaboration at CERN has measured diffractive dissociation of 190  GeV/c pions into the π−π−π+ final state using a stationary hydrogen target. A partial-wave analysis (PWA) was performed in bins of 3π mass and four-momentum transfer using the isobar model and the so far largest PWA model consisting of 88 waves. A narrow peak is observed in the f0(980)π channel with spin, parity and C-parity quantum numbers JPC=1++. We present a resonance-model study of a subset of the spin-density matrix selecting 3π states with JPC=2++ and 4++ decaying into ρ(770)π and with JPC=1++ decaying into f0(980)π. We identify a new a1 meson with mass (1414+15−13)  MeV/c2 and width (153+8−23)  MeV/c2. Within the final states investigated in our analysis, we observe the new a1(1420) decaying only into f0(980)π, suggesting its exotic nature.
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http://journals.aps.org/prl/pdf/10.1103/PhysRevLett.115.082001
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11368/2846976
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