Abstract

This article presents differential measurements of the asymmetry between $\Lambda_b^0$ and $\overline{\Lambda}_b^0$ baryon production rates in proton-proton collisions at centre-of-mass energies of $\sqrt{s}=7$ and $8\,\textrm{TeV}$ collected with the LHCb experiment, corresponding to an integrated luminosity of $3\,\textrm{fb}^{-1}$. The $\Lambda_b^0$ baryons are reconstructed through the inclusive semileptonic decay $\Lambda_b^0\rightarrow\Lambda_c^+\mu^-\overline{\nu}_{\mu}X$. The production asymmetry is measured both in intervals of rapidity in the range $2.15<y<4.10$ and transverse momentum in $2<p_T<27\,\textrm{GeV}/c$. The results are found to be incompatible with symmetric production with a significance of 5.8 standard deviations for both $\sqrt{s}=7$ and $8\,\textrm{TeV}$ data, assuming no $C\!P$ violation in the decay. There is evidence for a trend as a function of rapidity with a significance of 4 standard deviations. Comparisons to predictions from hadronisation models in PYTHIA and heavy-quark recombination are provided. This result constitutes the first observation of a particle-antiparticle asymmetry in $b$-hadron production at LHC energies.

Table 1

Data from Table 4 and Figure 9 (left)

10.17182/hepdata.114013.v1/t1

$\Lambda_{b}^{0}$ production asymmetry in bins of $\Lambda_{b}^{0}$ rapidity for proton-proton collisions at $\sqrt{s} = 7$ TeV. The first uncertainty is...
Table 2

Data from Table 4 and Figure 9 (left)

10.17182/hepdata.114013.v1/t2

$\Lambda_{b}^{0}$ production asymmetry in bins of $\Lambda_{b}^{0}$ rapidity for proton-proton collisions at $\sqrt{s} = 8$ TeV. The first uncertainty is...
Table 3

Data from Table 5 and Figure 9 (right)

10.17182/hepdata.114013.v1/t3

$\Lambda_{b}^{0}$ production asymmetry in bins of $\Lambda_{b}^{0}$ $p_T$ for proton-proton collisions at $\sqrt{s} = 7$ TeV. The first uncertainty is...
Table 4

Data from Table 5 and Figure 9 (right)

10.17182/hepdata.114013.v1/t4

$\Lambda_{b}^{0}$ production asymmetry in bins of $\Lambda_{b}^{0}$ $p_T$ for proton-proton collisions with $\sqrt{s} = 8$ TeV. The first uncertainty is...
Table 5

Data for Figure 12 (top); Figure 24? analysis note

10.17182/hepdata.114013.v1/t5

Covariance matrix of the statistical uncertainty on $\Lambda_{b}^{0}$ production asymmetry in bins of $\Lambda_{b}^{0}$ rapidity for proton-proton collisions with $\sqrt{s}...
Table 6

Data for Figure 12 (top); Figure 24? analysis note

10.17182/hepdata.114013.v1/t6

Covariance matrix of the statistical uncertainty on $\Lambda_{b}^{0}$ production asymmetry in bins of $\Lambda_{b}^{0}$ rapidity for proton-proton collisions with $\sqrt{s}...
Table 7

Data from Figure 24 analysis note

10.17182/hepdata.114013.v1/t7

Covariance matrix of the systematic uncertainty on $\Lambda_{b}^{0}$ production asymmetry in bins of $\Lambda_{b}^{0}$ rapidity for proton-proton collisions with $\sqrt{s}...
Table 8

Data from Figure 24? in analysis note

10.17182/hepdata.114013.v1/t8

Covariance matrix of the systematic uncertainty on $\Lambda_{b}^{0}$ production asymmetry in bins of $\Lambda_{b}^{0}$ rapidity for proton-proton collisions with $\sqrt{s}...
Table 9

Figure 13 (left)

10.17182/hepdata.114013.v1/t9

Measured, normalised distribution of $p_T, y$ from background-subtracted $\Lambda_{b}^{0}$ candidates for $\sqrt{s} = 7$ TeV. Distribution is not corrected for...
Table 10

Figure 13 (right)

10.17182/hepdata.114013.v1/t10

Measured, normalised distribution of $p_T, y$ from background-subtracted $\Lambda_{b}^{0}$ candidates for $\sqrt{s} = 8$ TeV. Distribution is not corrected for...

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