HYP2018: 13th International Conference on Hypernuclear and Strange Particle Physics

Feasibility of lifetime measurements on hyperhydrogens with the photon beams

Not scheduled

15m

2nd Floor

Abstract Submission

Speaker

Dr Sho Nagao (Tohoku University)

Description

Decay processes of Lambda hypernuclei up to $p$-shell have been measured with many experiments such as the bubble-chambers, the emulsions, and the missing mass spectroscopies. Theoretical calculations are good agreements with these experimental results especially for the mesonic weak decay (MWD) processes, in which a hypernucleus decays emitting with a pion. Decay processes of $s$-shell hypernuclei are dominated with the well-understanding MWD processes because the final states are not forbitten by the Pauli principle. Decay width would be estimated well in our frameworks. However, recent results of hypertriton reported by heavy-ion experiments have a surprise because their results are consistently supported more than 20% shorter lifetime than Lambda’s lifetime. That is unexpected results, furthermore, this short lifetime is difficult to reproduce in any theoretical frameworks. In order to settle this “puzzle”, some experimental projects were launched. We started a new project to study the decay processes of Lambda hypernuclei with the photon beam at ELPH Tohoku. We aim to produce the hypertriton with the $(\gamma,K^+)$ reaction from a $^3$He target. One of our advantages is better S/N ratio of the hypertriton because the hypertriton would be identified with missing mass technique. In addition, our approach is a different method to obtain the lifetime. namely, the lifetime would be deduced with direct timing measurement. New tagging photon beams are available with the energy range of 0.8-1.26 GeV, that is suitable energy for hypernuclear production. Momenta of $K^+$ would be measured by Neutral Kaon Spectrometer 2 (NKS2), that has large solid angles. The decay timing would be measured with newly developed high-timing-resolution counters (TDL) which have 50 ps time-resolution. I will introduce our new project and expected results with detail simulation. Status of detector preparations are also shown in this presentation.