Charged kaon and proton multiplicities in semi-inclusive deep-inelastic scattering with 11 GeV electrons

Abstract

Measurements of SIDIS multiplicities for charged kaons and protons from proton and deuteron targets are reported on a grid of hadron kinematic variables $0.3<z<0.7$ and $P_t<0.6$ GeV for leptonic variables $0.3<x<0.6$ and $3<Q^2<6$ GeV${}^2$. Data were acquired in 2018-2019 at Jefferson Lab Hall C with 10.2 and 10.6~GeV electron beams impinging on 10-cm-long liquid hydrogen and deuterium targets. Electrons (hadrons) were detected in the HMS (SHMS) spectrometers. Multiplicities were fitted for each bin in $(x,Q^2,z,P_t)$ as $M_0[1+A\cos (\ddot{I}{•}^{\ast })+B\cos (2\ddot{I}{•}^{\ast })]$. The kaon kinematic range spans the regions where transverse-momentum-dependent factorization can be applied in SIDIS, and a `soft' central region where other processes are of critical importance. The kaon to pion ratios of $M_0$ are in reasonable agreement with predictions using the DSS fragmentation functions for $K^{+}$, but are mostly well below them for $K^{-}$. The kaon azimuthal modulations are consistent with zero. The kinematic range for protons is centered on the `soft' central region. The proton-to-pion multiplicity ratios are more than an order-of-magnitude larger than TMD predictions at the lowest value of $W^2$, decreasing to as little as a factor of two at the highest value of $W^2$. No significant difference is observed between proton and deuteron targets. These trends are consistent with Lund Monte Carlo predictions. The proton values of $A$ are consistently positive, with an average value of approximately 0.01, while $B$ is consistent with zero.

19 pages, 11 figures, to be submitted to Phys. Rev. C