Jun 2 – 7, 2019
Carnegie Mellon University
America/New_York timezone

Independent determination of Lambda Decay Parameter

Jun 3, 2019, 5:30 PM
Rangos 2 (Seidl)

Rangos 2


Contributed Electroweak Probes Fundamental Symmetries


Maxim Mai (The George Washington University)


The asymmetry parameter $\alpha_-$ of the parity-violating weak decay $\Lambda \rightarrow p \pi^-$ is a result of interference between $s$- and $p$-waves. The BESIII collaboration recently reported a value of $\alpha_-$ as 0.750(9)(4) - which is significantly higher than the current PDG value of 0.642(13).

In the same time, most of the polarization observables (from CLAS measurements) also depend on the value of $\alpha_-$. We show, that a higher value of the decay parameter is obtained when constraints from spin-algebra (Fierz identities) are implemented into the analysis of the photoproduction data.

Such, independently obtained value is significantly closer to the BESIII value than the quoted PDG value and implies also a closer agreement with vanishing matter/antimatter asymetry ratio $(\alpha_-+\alpha_+)/(\alpha_--\alpha_+)$.

Early Consideration No
Graduate Student No

Primary authors

Prof. David Ireland (University of Glasgow) Prof. Michael Doering (GWU) Maxim Mai (The George Washington University) Dr Deborah Roenchen (HISKP, Bonn) Dr Johann Haidenbauer (Forschungszentrum Julich) Dr Derek Glazier (University of Glasgow) Dr Roderick Murray-Smith (University of Glasgow)

Presentation materials