Sep 10 – 13, 2019
University of Perugia (Italy)
Europe/Zurich timezone

Evidence for $\Sigma^+ \to p \mu^+ \mu^-$ decays at LHCb

Sep 12, 2019, 4:00 PM
Aula Magna (University of Perugia (Italy))

Aula Magna

University of Perugia (Italy)

Piazza dell'Università 1, 06123 Perugia (Italy)


Francesco Dettori (Universita e INFN, Cagliari (IT))


A search for the very rare $\Sigma^+ \to p \mu^+ \mu^-$ performed within the LHCb experiment is presented. An evidence for this decay was seen by the HyperCP collaboration, with the invariant mass of the dimuon pairs surprisingly found peaking at 214 MeV/c2, leading to the hypothesis of an intermediate (unknown) particle mediating this decay (known as HyperCP anomaly).
Thanks to the copious production of $\Sigma$ hyperons at LHC and to the acceptance for relatively long lived particles the LHCb experiment is able to search for these decays.
A strong evidence for the Sigma->p mu mu decay is presented and a measurement of its branching fraction performed relative to the Sigma-> p pi0 decay. No peaking structure is observed in the dimuon invariant mass, putting a stringent limits on the existence of the putative particle and pointing to a resolution of the HyperCP anomaly. Prospects for observing the decay at Standard Model level with Run 2 data and for additional observables are also shown.

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