This article reports the measurement of the transverse-momentum ($p_{ \rm T}$) differential production cross section of B$^0$ mesons in proton-proton collisions at a centre-of-mass energy of $\sqrt{ s}=13.6$ TeV with the ALICE detector at the CERN LHC. For the first time, the B$^0$ production cross section is measured at midrapidity ($|y|<0.5$) down to $p_{ \rm T}=1~\mathrm{ GeV}/c$ at LHC energies. The B$^0$ mesons and their charge conjugates were reconstructed via the B$^{ 0}\to$D$^{ -}\pi^+$ decay channel, followed by the D$^-\to$K$^+\pi^-\pi^-$ decay. The measured $p_{ \rm T}$-differential production cross section is described within uncertainties by state-of-the-art models based on perturbative quantum-chromodynamics calculations. Its rapidity dependence is also studied by computing the $p_{ \rm T}$-differential ratios between the ALICE measurement and the one of B$^+$ mesons performed by the LHCb Collaboration at forward rapidity. The B$^0$ production cross section per unit of rapidity at midrapidity is ${ \rm d}\sigma({ \rm B^0})/{ \rm d} y|_{ |y|<0.5} = 24.2 \pm 1.4~(\text{ stat.}) \pm 2.6~(\text{ syst.})_{ -0.3}^{ +0.2}~(\text{ extrap.})~\mu{ \rm b}$.
Categories: hep-ex nucl-ex