Evidence for the decay sigma+ --> pmu+ mu-

Area of Science:

• Particle Physics
• Hyperon Decays
• Rare Processes

Background:

• The Sigma+ hyperon is a baryon containing strange quark.
• Understanding hyperon decays provides insights into the Standard Model of particle physics.
• Previous searches for Sigma+ --> p mu+ mu- decay have not yielded evidence.

Purpose of the Study:

• To search for and report the first evidence of the Sigma+ --> p mu+ mu- decay.
• To measure the branching ratio of this rare decay.
• To investigate the properties of the dimuon system in this decay.

Main Methods:

• Analysis of data collected by the HyperCP (E871) experiment at Fermilab.
• Identification of Sigma+ hyperon decays into a proton and a dimuon pair.
• Statistical analysis to determine the significance and branching ratio of the observed decay.

Main Results:

• Observed three events consistent with the Sigma+ --> p mu+ mu- decay.
• Measured the branching ratio B(Sigma+ --> p mu+ mu-) = [8.6(+6.6)(-5.4)(stat)+/-5.5(syst)]x10(-8).
• The dimuon mass distribution suggests a possible intermediate neutral state (P0) with a mass of 214.3+/-0.5 MeV/c(2).

Conclusions:

• The first experimental evidence for the Sigma+ --> p mu+ mu- decay has been established.
• The measured branching ratio is consistent with theoretical predictions for rare hyperon decays.
• The potential intermediate neutral state warrants further investigation in future studies.