Single Inclusive $π^\pm$ and $K^\pm$ Production in $e^+e^-$ Annihilation at center-of-mass Energies from 2.000 to 3.671GeV

Abstract

Using data samples with a total integrated luminosity of 253 $\rm pb^{-1}$ collected by the BESIII detector operating at the BEPCII collider, the differential cross-sections of inclusive $π^\pm$ and $K^\pm$ production, as a function of momentum and normalized by the total hadronic cross-section, are measured at center-of-mass energies from 2.000 to 3.671 GeV. The measured $π^{\pm}$ cross sections are consistent with the previously reported $π^{0}$ cross-sections by BESIII, while the $K^{\pm}$ cross sections are systematically higher than the $K^0_S$ cross sections by a factor of approximately 1.4. These new results are in agreement with state-of-the-art QCD analyses at next-to-next-to-leading order accuracy, particularly in the large hadron momentum region at energy scales down to 3 GeV. These findings support the validity of isospin symmetry in parton fragmentation processes.

Figures (2)

• Figure 1: Normalized differential cross sections of $e^+e^-\to\pi^{\pm}+X$ and $e^+e^-\to K^{\pm}+X$. The points with error bars are the measured values, where the uncertainties are the quadrature sum of the corresponding statistical and systematic uncertainties. Note that the observable has been scaled by an artificial factor in the plots and the line through the bin center is to group the points according to their center-of-mass energy. The cross section of the process $e^+e^-\to K^{\pm}+X$ exhibits enhancements in the high-momentum regions. These enhancements may be attributed to contributions from the process $e^+e^-\to K_2^{*\pm}(1430)K^\mp, K_1^{\pm}(1400)K^{\mp}, K_1^{\pm}(1270)K^{\mp}$BESIII:2022wxzBESIII:2020vtu.
• Figure 2: Normalized differential cross sections of $e^+e^-\to\pi^{\pm}+X$ and $e^+e^-\to K^{\pm}+X$. The points with error bars are the measured values, where the uncertainties are the quadrature sum of the corresponding statistical and systematic uncertainties. The $\pi^0$ and $K_S^0$ results at the same center-of-mass energies from previous measurements at BESIII BESIII:2022zit are also shown. The green and red bands denote the "NPC" NNLO calculations Gao:2024nkzGao:2024dbv with 1$\sigma$ limits, based on new global analyses by including SIA world data Gao:2024dbv and our new results. The blue band is the "NPC" NNLO calculation for $K_S^0$ by using $K^{\pm}$ fragmentation functions via isospin symmetry. Only the measurements on the right of the dotted lines are employed in the fit.