Measurement of the $\mathbf{B^0}$-meson production cross section in proton--proton collisions at $\mathbf{\sqrt{\textit{s}}=13.6}$ TeV

Abstract

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$^{-}π^+$ decay channel, followed by the D$^-\to$K$^+π^-π^-$ 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 ${\rm d}σ({\rm B^0})/{\rm d} y|_{|y|<0.5} = 24.2 \pm 1.4~(\text{stat.}) \pm 2.6~(\text{syst.})_{-0.3}^{+0.2}~(\text{extrap.})~μ{\rm b}$.

Figures (9)

• Figure 1: Recall efficiency for non-prompt $\mathrm{D^\pm}$ mesons estimated as the ratio between the yield from the offline-trigger-selected dataset and the yield extracted by applying the same selection criteria to a minimum-bias data sample, as described in the text.
• Figure 2: Invariant-mass distributions of $\mathrm {B^0}$-meson candidates in the $1 < p_\mathrm{T}\xspace < 23.5 ~ \mathrm{GeV}/c\xspace$ (top), $2 < p_\mathrm{T}\xspace < 4 ~ \mathrm{GeV}/c\xspace$ (bottom-left), and $10 < p_\mathrm{T}\xspace < 14 ~ \mathrm{GeV}/c\xspace$ (bottom-right) intervals. The contributions of the different partially and mis-reconstructed decays to the total fit function (blue) are reported on top of the combinatorial background fit function (red dashed line) with filled colour-coded areas. The values of the signal counts ($S$) are reported in the text.
• Figure 3: Acceptance-times-efficiency factors for $\mathrm {B^0}$ mesons as a function of $p_\mathrm{T}$. For each $p_\mathrm{T}$ interval, the acceptance correction is shown (green), then multiplied by both trigger and BDT selection efficiencies (blue).
• Figure 4: $p_\mathrm{T}$-differential production cross section of $\mathrm {B^0}$ mesons measured at midrapidity ($|y|<0.5$) in pp collisions at $\sqrt{s}\xspace=13.6~\mathrm{TeV}\xspace$ compared with FONLL Cacciari:2012ny, GM-VFNS(mod-$\mu_\mathrm{R,F}$) Kniehl:2007erqBenzke:2019usl, GM-VFNS(SACOT-$m_\mathrm{T}$) Helenius:2023wkn, and $k_\mathrm{T}$-factorisation Guiot:2021vnpBarattini:2025wbo calculations (left panel) and ratios of the data to the theoretical predictions (right panel). Statistical uncertainties are depicted as vertical error bars, and systematic uncertainties as boxes. The systematic uncertainties related to normalisation are quoted separately as text.
• Figure 5: $p_\mathrm{T}$-differential production cross section of $\mathrm {B^0}$ mesons measured at midrapidity ($|y|<0.5$) in pp collisions at $\sqrt{s}\xspace=13.6~\mathrm{TeV}\xspace$ compared with $k_\mathrm{T}$-factorisation Guiot:2021vnpBarattini:2025wbo calculations. The contributions to the predicted $\mathrm {B^0}$ production cross section arising from gluon and beauty-quark fragmentation into a $\mathrm {B^0}$ meson are also shown. Statistical uncertainties are depicted as vertical error bars, and systematic uncertainties as boxes. The systematic uncertainties related to normalisation are quoted separately as text.