Addendum to multiplicities of charged pions, kaons and unidentified charged hadrons on an isoscalar target measured by COMPASS Collaboration

TL;DR

This work updates COMPASS isoscalar SIDIS multiplicities by applying radiative corrections derived from the DJANGOH Monte Carlo, instead of the previously used TERAD-based estimates. The two-step procedure combines $rc_{\rm DIS}$ from TERAD with $rc_{\rm had}$ from DJANGOH to yield $RC_{\rm DJANGOH}$, which is tabulated in a 3D $(x,y,z)$ framework and shows notable differences from $RC_{\rm TERAD}$, especially for $\pi^{\pm}$ at low $x$ and high $z$. Implementing $dM_{\rm new}/dz = dM_{\rm previous}/dz \times (rc_{\rm DIS}/rc_{\rm had})_{\rm TERAD} \times RC_{\rm DJANGOH}$ yields updated isoscalar multiplicities, with changes up to about 12% in certain kinematic regions and smaller corrections for kaons due to prior conservative handling. The new results, which supersede earlier measurements, are consistent with recently published proton multiplicities and are made publicly available on HEPData to ensure reproducibility and cross-target comparability.

Abstract

The COMPASS Collaboration has recently published an article "Multiplicities of positive and negative pions, kaons, and unidentified hadrons from deep-inelastic scattering of muons off a liquid hydrogen target", Phys. Rev. D 112 (2025) 012002. In contrast to earlier COMPASS publications on similar topics, the aforementioned article features an enhanced treatment of QED radiative corrections, employing the DJANGOH Monte Carlo generator. This methodological improvement led to corrections that are up to 12% larger in the low-x, high-z region compared to the previously applied ones. To ensure consistent treatment of COMPASS data sets obtained using both isoscalar and proton targets, this paper presents an updated set of isoscalar multiplicities based on DJANGOH-derived radiative corrections. The present results supersede those published in Phys. Lett. B 764 (2017) 1 and Phys. Lett. B 767 (2017) 133.

Figures (4)

• Figure 1: Left panel: comparison of $RC$ factors for positive pions in a selected $(x,y)$ bin as a function of $z$ using DJANGOH-MC (red circles) and TERAD from Ref. comp_pi (black circles), right panel: comparison of $RC$ factors for positive kaons in a selected $(x,y)$ bin as a function of $z$ using DJANGOH-MC (red squares) and based on TERAD from Ref. comp_K (black squares).
• Figure 2: Left panel: the values of $RC_{\rm DJANGOH}$ for $\pi^{\pm}$ and ${\rm K}^{\pm}$ in a selected $(x,y)$ bin as a function of $z$ (for clarity staggered horizontally), right panel: the values of $RC_{\rm DJANGOH}$ obtained for proton and isoscalar targets in a selected $(x,y)$ bin as a function of $z$.
• Figure 3: Values of ${\rm d} M^{\pi^{+}}_{\rm ratio-1} /{\rm d}z$ as a function of $z$ for nine bins of $x$ and five bins of $y$ (for clarity staggered vertically by $\alpha$).
• Figure 4: Values of ${\rm d}M^{K^{+}}_{\rm ratio-1} /{\rm d}z$ as a function of $z$ for nine bins of $x$ and five bins of $y$ (for clarity staggered vertically by $\alpha$).