Measurement of $B^+$, $B^0$ and $\Lambda_b^0$ production and nuclear modification in $p$Pb collisions at $\sqrt{s_\mathrm{NN}}=8.16 ~~\text {TeV}$

The production of $B^+$, $B^0$ and $\Lambda^0_b$ hadrons is studied in proton-lead collisions at a centre-of-mass energy per nucleon pair of $\sqrt{s_\mathrm{NN}}=8.16~~\text {TeV}$ with the LHCb detector at the LHC. The measurement uses an integrated luminosity of $12.2\pm0.3\mathrm{nb}^{-1}$ for the proton beam projecting into the LHCb detector (positive rapidity) and $18.6\pm0.5\mathrm{nb}^{-1}$ for the lead beam projecting into the LHCb detector (negative rapidity). Nuclear effects in proton-lead data are probed by double-differential cross-sections, forward-to-backward cross-section ratios and nuclear modification factors of the beauty hadrons. The double-differential cross-sections are measured as function of the beauty hadron transverse momentum and rapidity in the nucleon-nucleon centre-of mass frame. Forward-to-backward cross-section ratios and nuclear modification factors indicate a significant nuclear suppression at positive rapidity compared to $pp$ collisions and compared to negative rapidity. The baryon-to-meson ratio of $\Lambda^0_b$ over $B^0$ is reported as well and exhibits a value consistent with the same measurements in $pp$ collisions at positive rapidity, whereas tensions are observed at negative rapidity.