Femtoscopy of non-identical particle pairs has been instrumental for precision measurements of both two-particle sources and the final-state interactions in high-energy elementary and heavy-ion collisions. The majority of measurements assessing the source properties are based on identical particle pairs, providing direct access to the characteristics of the single-particle source. The work in this paper demonstrates, via femtoscopy measurements of charged pion-deuteron pairs in Pb-Pb collisions at $\sqrt{s_{\rm NN}} = 5.02$ TeV, the feasibility of accessing the characteristics of the single-particle femtoscopic source by using particle pairs with large mass differences such as pions and deuterons. The first experimental results of the measurement of deuteron source sizes in ultrarelativistic heavy-ion collisions are presented. The results show good agreement with the trend derived from other charged hadrons such as pions, kaons, and protons as a function of transverse mass, indicating similar source properties
Submitted to: PRC
e-Print: arXiv:2504.02333 | PDF | inSPIRE
CERN-EP-2025-075
Figure group
Figure 1
Upper row: $\rm \uppi^{+}d \oplus \uppi^{-}\overline{d}$ correlation functions in three centrality classes with Coulomb (Lednick\'y--Lyuboshitz, denoted as L-L) fits shown as orange bands. Bottom row: $\rm \uppi^{-}d \oplus \uppi^{+}\overline{d}$ correlation functions in three centrality classes with L--L fits including both Coulomb and strong interaction shown as blue bands. The data are shown after non-femtoscopic background subtraction and corrections (see text for more details). The statistical and systematic uncertainties of the experimental data are represented by lines and boxes, respectively Bandwidths represent the systematic uncertainties related to the fit. The bottom sub-panels display the data-to-fit differences normalized by the statistical uncertainty $\sigma_{\rm stat}$. |  |
Figure 2
Values of $R_{\rm inv}$ as a function of $m_{\rm T}$ for Pb--Pb collisions at $\sqrt{s_{\text{NN}}} =$ 5.02 TeV for d and $\rm \bar{d}$, together with other mesons and baryons ($\uppi^{\pm}$, K$^{\pm}$, K$^{0}_{\rm S}$, p, $\rm \bar{p}$) taken from Ref. and rescaled to $\sqrt{s_{\text{NN}}} =$ 5.02 TeV The red, green, and blue colors stand for $0-10\%$, $10-30\%$, and $30-50\%$ centrality intervals, respectively. The bands correspond to power-law fits of the femtoscopic sources for all previously measured particles, with the width representing the uncertainty in the pion source measurements Statistical uncertainties are shown as lines. Systematic uncertainties arising from the analysis settings and from the pion source calculations based on rescaled data are shown with open and full boxes, respectively. |  |