π-mesonic decay of the hypertriton

Abstract

The π-mesonic decay of the hypertriton is calculated based on a hypertriton wavefunction and 3N scattering states, which are rigorous solutions of 3-body Faddeev equations using realistic NN and hyperon-nucleon interactions. The total π-mesonic decay rate is found to be 92% of the free Λ decay rate, which is close to the experimental data. Together with the nonmesonic decay the total life time of 3 Λ H is predicted to be 2.78 × 10 −10 sec which is 6 % larger than for the free Λ particle. The differential decay rate is evaluated as a function of the pion momentum. The decay into the N + d + π channel is stronger than in the 3N + π channel in contrast to the situation for the nonmesonic decay. The ratio for the decay rate into 3 He + π − to the decay rate into all channels including π − is found to be 0.40, which is close to the experimental value. We visualise the decay into the dominant channel p + d + π − in a Dalitz plot. Finally we compare the polarisation of the outgoing proton in free unpolarised Λ-decay to the polarisation of 3 He in unpolarised 3 Λ H-decay and we compare the closely related asymmetry of π − emitted parallel and antiparallel with respect to the spin-direction for a polarised Λ to the corresponding asymmetry for a polarised 3 Λ H. 21.80.+a, 21.45.+v, 23.40.-s Typeset using REVT E X * present address:

(Anti)hypertriton lifetime puzzle

“…Therefore, a meaurement of the precise lifetime of hypernucleus could provide a tool to investigate of hyeron-nucleon interaction [1][2][3][4][5][6][7]. The most simple hypernucleus is hypertriton, which is a bound state of a proton, a neutron, and a hyperon (Λ or Ξ), it is bound with respect to the Λ-d threshold by 0.136±0.05 MeV.…”

Production of (Anti-)(Hyper)nuclei in Pb–Pb Collisions Measured with ALICE at the LHC

“…The mean lifetimes of light Λ-hypernuclei (A ≤ 4) are expected to be very similar to that of the free Λ, if the Λ in the hypernucleus is weakly bound [21]. The measured mean lifetimes of light hypernuclei such as 3 Λ H [3,[22][23][24][25][26][27][28] are not known as precisely as the Λ lifetime, and theoretical predictions [21,[29][30][31][32][33][34][35][36] are scattered over a large range, too. Recently, a statistical combination of the experimental 3 Λ H mean lifetime estimates available in literature was published, providing an average value τ = ( 216 +19…”

On the Measurement of the Lifetime of Hydrogen Hyperisotopes at J-PARC and JLab

“…Moreover, also the two-body decay reaction could be considered (BR∼0.25 [16] From the table it is evident that, if the 3 Λ H production cross section is only one tenth of the 4 Λ H one, the measurement is not feasible with the present K1.8 intensity.…”

“…If the three-body 3 Λ H mesonic decay reaction is considered, 3 [16]), the expected 3 Λ H decay rate can be evaluated as:…”

“…From the theoretical point of view, since 3 Λ H has a very small Λ binding energy, it is expected that the constituent Λ spends most of the time far from the deuteron core and that the lifetime is accordingly very close to the free Λ value. Total decay width values Γ( 3 Λ H) = (1.03 ÷ 1.10) Γ Λ have been evaluated in [15] and a lifetime of 256 ps is predicted in [16]. For 4 Λ H, which has a quite higher Λ binding energy, the only available calculation [17] gives an overestimated value, 264.1 ps, due to underestimate of the non-mesonic decay rate, which is, however, expected to be quite small for A=4.…”