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Evidence for an excited hyperon state in pp --> pK+Y0*
I Zychor1, V Koptev, M Büscher
1The Andrzej Sołtan Institute for Nuclear Studies, 05400 Swierk, Poland.
Physical Review Letters
|February 21, 2006
Summary
Researchers observed a neutral excited hyperon (Y0*) in a proton-proton collision experiment. Its mass and width suggest it might be an exotic particle not predicted by current quark models.
Area of Science:
- Nuclear Physics
- Particle Physics
- Hadron Spectroscopy
Background:
- Investigating the properties of excited hyperons is crucial for understanding baryon structure.
- The existence of exotic particles beyond the Standard Model is a key area of research.
Purpose of the Study:
- To search for and characterize a neutral excited hyperon (Y0*) produced in proton-proton collisions.
- To determine the mass, width, and production cross-section of the observed Y0* state.
Main Methods:
- Experiments were conducted using the ANKE spectrometer at COSY-Jülich with a proton beam at 3.65 GeV/c.
- Two decay channels (Y0* --> pi+X- and pi-X+) were simultaneously analyzed for consistent results.
Main Results:
- Evidence for a neutral excited hyperon (Y0*) was observed.
- The determined parameters are M(Y0*) = (1480 +/-15) MeV/c2 and gamma(Y0*) = (60 +/- 15) MeV/c2.
- The production cross-section is on the order of a few hundred nanobarns.
Conclusions:
- The observed Y0* could be the sigma(1480) resonance or a lambda hyperon, but its isospin remains undetermined.
- The Y0* state is not predicted by relativistic quark models, suggesting it may possess exotic properties.
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