$^3_Λ\mathrm{H}$ and $^3_{\barΛ}\mathrm{\bar{H}}$ lifetime measurement in Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}} = $ 5.02 TeV via two-body decay

An improved value for the lifetime of the (anti-)hypertriton has been obtained using the data sample of Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}} = $ 5.02 TeV collected by the ALICE experiment at the LHC. The (anti-)hypertriton has been reconstructed via its charged two-body mesonic decay channel and the lifetime has been determined from an exponential fit to the d$N$/d($ct$) spectrum. The measured value, $\tau$ = 242$^{+34}_{-38}$ (stat.) $\pm$ 17 (syst.) ps, is compatible with all the available theoretical predictions, thus contributing to the solution of the longstanding hypertriton lifetime puzzle.

 

Phys.Lett. B797 (2019) 134905
HEP Data
e-Print: arXiv:1907.06906 | PDF | inSPIRE

Figures

Figure 1

Invariant mass distribution of (\elio, $\pi^-$) and (\antielio, $\pi^+$) for the four $ct$ intervals used to determine the \hyptriton and \antihyptriton lifetime. The solid blue curve represents the function used to perform the fit and the red dashed curve represents the background component.
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Figure 2

Efficiency$\times$acceptance as a function of $ct$ for \hyptriton (red square), \antihyptriton (blue square) and \hyptriton+\antihyptriton (black open circle) in the same $ct$ intervals selected for the raw yields extraction.
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Figure 3

Corrected d$N$/d($ct$) spectrum fitted with an exponential function (red line) used to extract the (\hyptriton + \antihyptriton) lifetime. The bars and boxes represent the statistical and systematic uncertainties, respectively.
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Figure 4

Lifetime value $\tau$ determined from the minimization of the log-likelihood ratio --log($\lambda(\tau)$). The statistical uncertainty is evaluated at a confidence level of 68$\%$ (red dashed lines) with the log-likelihood ratio (blue line).
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Figure 5

Collection of the \hyptriton lifetime measurements obtained with different experimental techniques. The vertical lines and boxes are the statistical and systematic uncertainties respectively. The orange band represents the average of the lifetime values and the lines at the edge correspond to 1$\sigma$ uncertainty. The dashed-dotted lines are four theoretical predictions.
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