Measurement of the transverse-momentum fraction of strange hadrons from jet-like correlation structures in pp collisions at $\sqrt{s} = 13$ TeV

Abstract

The first measurements of the average transverse-momentum fraction ($\langle z \rangle$) as a function of transverse momentum ($p_{\rm T}$) for strange baryons ($Λ$ and $\barΛ$) and strange mesons ($K_{\rm S}^0$), produced in mini-jets defined through angular correlations in pp collisions at $\sqrt{s} = 13$ TeV, are reported by the ALICE Collaboration at the LHC. The observable is obtained using a novel method, where the angular correlation between the strange hadrons and inclusive charged hadrons is weighted by the $p_{\rm T}$ of correlated particles at small angular distance. As a function of strange particles' $p_{\rm T}$, the results reveal a flat trend for strange mesons and a decreasing trend for strange baryons in the measured $p_{\rm T}$ region, indicating distinct hadronization mechanisms for $K_{\rm S}^0$ and $Λ$($\barΛ$). The measurements are compared to Monte Carlo models, namely PYTHIA~8 (with both Monash and Color Rope tunes) and the AMPT (A Multi-Phase Transport) model with string melting. None of these models provides a satisfactory description of the $\langle z \rangle$ distributions at low and intermediate $p_{\rm T}$.

Figures (3)

• Figure 1: Example of the fully corrected $p_{\rm T}$-weighted correlation functions for ${\rm K}^{0}_{\rm{S}}$--primary charged-particles correlation (top) and for $\Lambda$ ($\overline{\Lambda}$)--primary charged-particles correlation (bottom).
• Figure 2: The average transverse-momentum fraction ($\langle z \rangle$) for $\Lambda$ ($\overline{\Lambda}$) (blue) and ${\rm K}^{0}_{\rm{S}}$ (red) as a function of $p_{\rm T}^{\rm s}$ in minimum bias pp collisions at $\sqrt{s}~=~13$ TeemV. The $p_{\rm T}^{\rm s}$ ranges from 0.6 to 20 GeemV/$c$. Statistical and systematic uncertainties of $\langle z \rangle$ are represented by vertical error bars and empty boxes, respectively. Data points are drawn at the corresponding average $p_{\rm T}^{\rm s}$ values in each interval. The horizontal bars represent the $p_{\rm T}^{\rm s}$ interval widths. The statistical and systematic uncertainties of the average $p_{\rm T}^{\rm s}$ values are negligible.
• Figure 3: The average transverse-momentum fraction ($\langle z \rangle$) for ${\rm K}^{0}_{\rm{S}}$ (top) and $\Lambda$ ($\overline{\Lambda}$) (bottom) in data compared with model calculations. The data are compared to Pythia $8$ with the Monash tune (red band), the Color Rope tune (green band) and the AMPT model with the string melting (blue band). For both Pythia $8$ tunes, the hatched bands represent the results excluding ${\rm K}^{0}_{\rm{S}}$ triggers coming from decays of the resonances ${\rm K}^{*}(892)^{0}$, ${\rm K}^{*}(892)^{\pm}$, and $\phi(1020)$, and $\Lambda$ ($\overline{\Lambda}$) triggers coming from decays of $\Sigma^{\pm}$, $\Xi^{-}$, $\Omega^{-}$ and their corresponding antiparticles.