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Observation of a New Narrow Axial-Vector Meson a1(1420).
C Adolph1, R Akhunzyanov2, M G Alexeev3
1Universität Erlangen-Nürnberg, Physikalisches Institut, 91054 Erlangen, Germany.
Physical Review Letters
|September 5, 2015
Summary
The COMPASS Collaboration discovered a new exotic a1 meson, the a1(1420), decaying into f0(980)π. This finding advances understanding of exotic particles in high-energy physics.
Area of Science:
- Particle Physics
- Hadron Spectroscopy
Background:
- Diffractive dissociation of pions provides insights into hadron structure.
- Understanding exotic mesons is crucial for advancing the Standard Model of particle physics.
Purpose of the Study:
- To investigate the 3π (three-pion) final state from pion diffractive dissociation.
- To identify and characterize new mesonic states, particularly exotic ones.
Main Methods:
- Measurement of diffractive dissociation of 190 GeV/c pions using a stationary hydrogen target at CERN.
- Partial-wave analysis (PWA) employing an 88-wave isobar model across various 3π mass and four-momentum transfer bins.
Main Results:
- Observation of a narrow peak in the f0(980)π channel with J(PC)=1(++).
- Identification of a new a1 meson, denoted as a1(1420), with a mass of 1414 MeV/c² and a width of 153 MeV/c².
- The a1(1420) was observed to decay exclusively into the f0(980)π channel, suggesting exotic properties.
Conclusions:
- The newly identified a1(1420) meson exhibits characteristics suggestive of an exotic nature due to its specific decay channel.
- This discovery contributes to the ongoing search for and characterization of non-conventional hadronic states.
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