| Crystal Barrel Collaboration (2007) | |||||||||||||
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| Measurements of two-body branching ratios for pp annihilations at rest in liquid and gaseous (12 ae STP ) hydrogen are reported. Channels studied are pp ! 0 0 , 0 j, K 0 L K 0 S , + \Gamma and K + K \Gamma . The results are critically compared with those from other experiments. Values of the fraction of P-state annihilation for a range of target densities from 0.002 ae STP to liquid H 2 are determined. 1 Introduction In a previous paper [1] we have reported a measurement of the branching ratio BR( 0 0 ; liq) for the annihilation reaction pp ! 0 0 at rest in liquid hydrogen. Further details about this measurement and results for a wide range of other two-body channels are given in [2]. As pointed out in [1] our measured branching ratio for the 0 0 channel, with detection of all 4 photons, is significantly larger than previously measured values where only 2 or 3 photons from the decay of the 2 pions were detected. When combined with the branching ratio measu... | |||||||||||||
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