Study of flavor dependence of the baryon-to-meson ratio in proton-proton collisions at $\sqrt{s}=13\text{ }\text{ }\mathrm{TeV}$

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Study of flavor dependence of the baryon-to-meson ratio in proton-proton collisions at $\sqrt{s} = 13 TeV$

S. Acharya et al. (ALICE Collaboration)

Phys. Rev. D 108, 112003 – Published 8 December 2023

Abstract

The production cross sections of $D^{0}$ and $Λ_{c}^{+}$ hadrons originating from beauty-hadron decays (i.e., nonprompt) were measured for the first time at midrapidity ( $| y | < 0.5$ ) by the ALICE Collaboration in proton-proton collisions at a center-of-mass energy $\sqrt{s} = 13 TeV$ . They are described within uncertainties by perturbative QCD calculations employing the fragmentation fractions of beauty quarks to baryons measured at forward rapidity by the LHCb Collaboration. The $b \bar{b}$ production cross section per unit of rapidity at midrapidity, estimated from these measurements, is $d σ_{b \bar{b}} / d y |_{| y | < 0.5} = 83.1 \pm 3.5 (stat) \pm 5.4 (syst)_{- 3.2}^{+ 12.3} (extrap) μ b$ . The baryon-to-meson ratios are computed to investigate the hadronization mechanism of beauty quarks. The nonprompt $Λ_{c}^{+} / D^{0}$ production ratio has a similar trend to the one measured for the promptly produced charmed particles and to the $p / π^{+}$ and $Λ / K_{S}^{0}$ ratios, suggesting a similar baryon-formation mechanism among light, strange, charm, and beauty hadrons. The $p_{T}$ -integrated nonprompt $Λ_{c}^{+} / D^{0}$ ratio is found to be significantly higher than the one measured in $e^{+} e^{-}$ collisions.

Received 8 September 2023
Accepted 15 November 2023

DOI:https://doi.org/10.1103/PhysRevD.108.112003

Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Funded by SCOAP³.

Physics Subject Headings (PhySH)

Hadron-hadron interactions Particle production

Bottom quark

Nuclear Physics

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Vol. 108, Iss. 11 — 1 December 2023

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Figure 1
Invariant-mass distributions of the $D^{0}$ - and $Λ_{c}^{+}$ -hadron candidates and their charge conjugates produced in pp collisions at $\sqrt{s} = 13 TeV$ and reconstructed at midrapidity, shown in a selected $p_{T}$ range. The values for the Gaussian mean $μ$ , width $σ$ , and raw yield $S$ are reported. Top row: $D^{0} \to K^{-} π^{+}$ meson candidates measured in the $2 < p_{T} < 4 GeV / c$ interval. Middle row: $Λ_{c}^{+} \to p K_{S}^{0}$ baryon candidates measured in the $2 < p_{T} < 4 GeV / c$ interval. Bottom row: $Λ_{c}^{+} \to {pK}^{-} π^{+}$ baryon candidates measured in the $2 < p_{T} < 4 GeV / c$ interval. The corresponding BDT probability minimum threshold for the candidate selection is reported. The left (right) column corresponds to the prompt (nonprompt) $D^{0}$ - and $Λ_{c}^{+}$ -hadron candidates enriched sample.
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Figure 2
Raw-yield distribution as a function of the BDT-based selection employed in the $χ^{2}$ -minimization procedure adopted for the determination of $f_{nonprompt}$ of $D^{0}$ in $2 < p_{T} < 4 GeV / c$ (top left panel), $Λ_{c}^{+} \to {pK}^{-} π^{+}$ in $4 < p_{T} < 6 GeV / c$ (top right panel), and $Λ_{c}^{+} \to p K_{S}^{0}$ in $6 < p_{T} < 8 GeV / c$ (bottom left panel). Bottom right panel: $f_{nonprompt}$ fraction as function as $p_{T}$ obtained for the set of selection criteria adopted in the analysis of for nonprompt $D^{0}$ , $Λ_{c}^{+} \to {pK}^{-} π^{+}$ , and $Λ_{c}^{+} \to p K_{S}^{0}$ hadrons.
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Figure 3
$p_{T}$ -differential production cross sections of nonprompt $D^{0}$ and $Λ_{c}^{+}$ hadrons in pp collisions at $\sqrt{s} = 13 TeV$ compared with predictions obtained with fonll calculations [13, 14, 15] adopting $f (b \to B)$ and $f (b \to Λ_{b}^{0})$ fragmentation fractions measured in $e^{+} e^{-}$ collisions [61] and LHCb Collaboration [39] (left panel) and the tamu model [49] (right panel) combined with pythia8 [50, 58] for the $h_{b} \to h_{c} + X$ decay kinematics.
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Figure 4
Beauty production cross section per rapidity unit at midrapidity obtained from from dielectron [66] and nonprompt $J / ψ$ [3], $D^{0}$ , and $Λ_{c}^{+}$ hadrons measured in pp collisions at $\sqrt{s} = 13 TeV$ compared to FONLL [13, 14, 15] and NNLO [22] predictions. The average $d σ_{b \bar{b}} / d y$ of the estimates from the $D^{0}$ and $Λ_{c}^{+}$ hadrons is also reported.
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Figure 5
Left: $p_{T}$ -differential ratios of nonprompt $Λ_{c}^{+}$ - and $D^{0}$ -hadron cross sections compared with predictions obtained with fonll calculations [13, 14, 15] and pythia8 [50, 58] for the $h_{b} \to h_{c} + X$ decay kinematics. The contributions from beauty mesons and from the $Λ_{b}^{0}$ baryon are depicted separately. Right: $p_{T}$ -differential ratios of prompt [27] and nonprompt $Λ_{c}^{+}$ - and $D^{0}$ -hadron cross sections compared with predictions obtained with the tamu model [36, 49] and pythia8 for the $h_{b} \to h_{c} + X$ decay kinematics.
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Figure 6
Non-prompt $Λ_{c}^{+} / D^{0}$ , prompt $Λ_{c}^{+} / D^{0}$ [27], $Λ / K_{S}^{0}$ [67], and $p / π^{+}$ [67] ratios measured in pp collisions at $\sqrt{s} = 13 TeV$ at midrapidity ( $| y | < 0.5$ ) compared with the $Λ_{b}^{0} / (B^{0} + B^{+})$ ratio measured by the LHCb Collaboration at forward rapidity ( $2.5 < y < 4$ ) [39] and with predictions obtained with the pythia8 MC generator with the Monash 2013 tune [50, 58] and the clr-blc modes 0, 2, and 3 [37] in the corresponding rapidity range with respect to data.
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Physical Review D

covering particles, fields, gravitation, and cosmology

Study of flavor dependence of the baryon-to-meson ratio in proton-proton collisions at $\sqrt{s} = 13 TeV$

S. Acharya et al. (ALICE Collaboration)

Phys. Rev. D 108, 112003 – Published 8 December 2023

Abstract

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Physical Review D

covering particles, fields, gravitation, and cosmology

Study of flavor dependence of the baryon-to-meson ratio in proton-proton collisions at s=13 TeV

S. Acharya et al. (ALICE Collaboration)

Phys. Rev. D 108, 112003 – Published 8 December 2023

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Study of flavor dependence of the baryon-to-meson ratio in proton-proton collisions at $\sqrt{s} = 13 TeV$