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Measurements of semi-inclusive deep-inelastic scattering multiplicities for ${\pi }^{+}$and ${\pi }^{-}$from proton and deuteron targets are reported on a grid of hadron kinematic variables $z, P_T$, and ${\varphi }^{*}$for leptonic kinematic variables in the range $0.3<x<0.6$and $3<Q^2<5{\mathrm{GeV}}^2$. Data were acquired in 2018 and 2019 at Jefferson Lab Hall C with a 10.6 GeV electron beam impinging on 10-cm-long liquid hydrogen and deuterium targets. Scattered electrons and charged pions were detected in the High Momentum Spectrometer and Super High Momentum Spectrometer, respectively. The multiplicities were fitted for each bin in $(x,Q^2,z,P_t)$to extract the ${\varphi }^{*}$—independent $M_0$and the azimuthal modulations $\langle cos\left({\varphi }^{*}\right)\rangle$and $\langle cos\left(2{\varphi }^{*}\right)\rangle$. The $P_t$dependence of the $M_0$results was found to be remarkably consistent for the four cases studied: $ep\to e{\pi }^{+}X, ep\to e{\pi }^{-}X, ed\to e{\pi }^{+}X, ed\to e{\pi }^{-}X$over the range $0\text{GeV}<P_t<0.4\text{GeV}$, as were the multiplicities evaluated near ${\varphi }^{*}={180}^{\circ }$over the extended range $0\text{GeV}<P_t<0.7\text{GeV}$. The Gaussian widths of the $P_t$dependence exhibit a quadratic increase with $z$. The $cos\left({\varphi }^{*}\right)$modulations were found to be consistent with zero for ${\pi }^{+}$, in agreement with previous world data, while the ${\pi }^{-}$moments were, in many cases, significantly greater than zero. The $cos\left(2{\varphi }^{*}\right)$modulations were found to be consistent with zero. The higher statistical precision of this dataset of about 20 000 individual multiplicity values, compared with previously published data, should allow improved determinations of quark transverse momentum distributions and higher twist contributions. 

The experiment at Jefferson Lab has observed $p\overline{p}$and, for the first time, $\mathrm{\Lambda }\overline{\mathrm{\Lambda }}$and $p\overline{\mathrm{\Lambda }}$photoproduction from a proton target at photon energies up to 11.6 GeV. The angular distributions are forward peaked for all produced pairs, consistent with Regge-like $t$-channel exchange. Asymmetric wide-angle antibaryon distributions show the presence of additional processes. In a phenomenological model, we find consistency with a double- $t$-channel exchange process where antibaryons are created only at the middle vertex. The model matches all observed distributions with a small number of free parameters. In the hyperon channels, we observe a clear distinction between photoproduction of the $\mathrm{\Lambda }\overline{\mathrm{\Lambda }}$and $p\overline{\mathrm{\Lambda }}$systems but general similarity to the $p\overline{p}$system. We report both total cross sections and cross sections differential with respect to momentum transfer and the invariant masses of the created particle pairs. No narrow resonant structures were found in these reaction channels. The suppression of $s\overline{s}$quark pairs relative to $d\overline{d}$quark pairs is similar to what has been seen in other reactions. 

American Physics Society