Use of photon detection to obtain a clean [pi]⁺[pi]⁻[pi]⁰ signal from p̄p annihilations
Date
1987
Authors
Mildenberger, Joseph L.
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Abstract
The availability of photon position information in the ASTERIX experiment has allowed the extraction of a very-nearly pure ?T+?T-?To signal from pp annihilations at rest in a gaseous H2 target. The conversion coordinates of the ,-rays from the decay of the 71'0 enable a three-constraint (3C) kinematic fit to be performed on candidate events. The extra constraints serve to almost totally eliminate the background events, consisting mainly of 7r+7r-27r0 and 7r+7r-37ro events. Monte Carlo simulations which take into account the momentum resolution for charged particles produce a missing-mass spectrum which agrees very well with the fit data. This is an improvement over data selected with a one-constraint (1C) kinematic fit, for which the level of contamination is estimated at ~ 14%. Such a clean set of 7r+ 71'- 71'0 events should allow a more reliable and accurate amplitudephase analysis to be done on the 7r+7r-7ro channnel. This technique is also applicable to other channels with neutral particles that decay to , -rays.