Two-pion femtoscopic correlations in Be+Be collisions at $\sqrt{s_{\text{NN}}}=16.84$ GeV measured by the NA61/SHINE at CERN

This paper reports measurements of two-pion Bose-Einstein (HBT) correlations in Be+Be collisions at a beam momentum of 150$AGeV\mathrm{/}\mathit{\text{c}}$ by the $NA61\mathrm{/}SHINE$ experiment at the CERN SPS accelerator. The obtained momentum space correlation functions can be well described by a Lévy distributed source model. The transverse mass dependence of the Lévy source parameters is presented, and their possible theoretical interpretations are discussed. The results show that the Lévy exponent $\alpha$ is approximately constant as a function of $m_{\mathrm{T}}$ , and far from both the Gaussian case of $\alpha =2$ or the conjectured value at the critical endpoint, $\alpha =0.5$. The radius scale parameter $R$ shows a slight decrease in $m_{\mathrm{T}}$, which can be explained as a signature of transverse flow. Finally, an approximately constant trend of the intercept parameter $\lambda$ as a function of $m_{\mathrm{T}}$ was observed, different from measurement results at RHIC.