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Measurement of the $\Lambda_c^+$ to $D^0$ production cross-section ratio in peripheral PbPb collisions

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Abstract

We report on a measurement of the $\Lambda_c^+$ to $D^0$ production ratio in PbPb collisions at $\sqrt{s_{\rm NN}}$= 5.02 TeV with the LHCb detector in the forward rapidity region $2 <y< 4.5$. The $\Lambda_c^+$ ($D^0$) hadrons are reconstructed via the decay channel $\Lambda_c^+\rightarrow pK^+\pi^-$ ($D^0 \rightarrow K^-\pi^+$) for $2<p_{\rm T}<8$ GeV$/c$ and in the centrality range of about 65-90. The results show no significant dependence on $p_{T}$, $y$ or the mean number of participating nucleons. They are also consistent with similar measurements obtained by the LHCb collaboration in pPb and Pbp collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV. The data agree well with predictions from PYTHIA in pp collisions at $\sqrt{s}$ = 5 TeV but are in tension with predictions of the Statistical Hadronization model.

Figures and captions

Invariant-mass spectra of (top) $ K ^- \pi ^+ $ and (bottom) $p K ^- \pi ^+ $ final states. The data are overlaid with the results of the fit.

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Lc_min[..].pdf [19 KiB]
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Lc_minv_full_new.pdf

Distributions of $\chi^2_{\text{IP}}$ of the $ D ^0$ (top) and $\Lambda ^+_ c $ (bottom) after background substraction. The data are overlaid with the results of the fit.

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D0_fprompt_full_new.pdf
Lc_fpr[..].pdf [18 KiB]
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Lc_fprompt_full_new.pdf

Prompt $R_{\Lambda ^+_ c / D ^0 }$ production ratios as a function of $\langle \mathrm{N_{part}} \rangle$ . The error bars along the y-axis (x-axis) represent the statistical uncertainties (RMS of the $\langle \mathrm{N_{part}} \rangle$ value), the boxes around the points the uncorrelated systematic uncertainties.

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npart.pdf

Prompt $R_{\Lambda ^+_ c / D ^0 }$ production ratios as a function of (left) $ p_{\mathrm{T}}$ and (right) rapidity. The error bars represent the statistical uncertainties, the boxes around the points the uncorrelated systematic uncertainties. Results are compared to the same measurement in $ p \mathrm{Pb}$ and $\mathrm{Pb} p $ collisions at $\sqrt{s_{\scriptscriptstyle\text{NN}}}$ = 5.02 TeV by the LHCb experiment [33].

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pt_pPb.pdf
y_pPb.pdf [15 KiB]
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y_pPb.pdf

Prompt $R_{\Lambda ^+_ c / D ^0 }$ production ratios as a function of (left) $ p_{\mathrm{T}}$ and (right) rapidity. The error bars represent the statistical uncertainties, the boxes around the points the uncorrelated systematic uncertainties. Results are compared to PYTHIA 8 [15] in $ p $ $ p $ collisions at $\sqrt{s}$ = 13 TeV (magenta band) and predictions from a Statical Hadronization Model [20] (blue band).

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pt_th.pdf
y_th.pdf [14 KiB]
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y_th.pdf

Animated gif made out of all figures.

 PAPER-2021-046.gif
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Tables and captions

values of $\langle \mathrm{N_{part}} \rangle$ in $N_c$ intervals, with $\sigma_{\rm part}$ indicating the total systematic uncertainty of $\langle \mathrm{N_{part}} \rangle$ .

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Value of the $k$ factor in intervals of $N_c$. The uncertainties are obtained from the statistical uncertainties of the different $ D ^0$ calibration samples in data and MC summed in quadrature.

 Table_2.pdf [51 KiB]
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Summary of the ranges of systematic uncertainties for the considered intervals of $N_c$, $ p_{\mathrm{T}}$ and $y$ for the $R_{\Lambda ^+_ c / D ^0 }$ ratio given in percentage.

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Results for the prompt $R_{\Lambda ^+_ c / D ^0 }$ production ratio, where the first uncertainties are statistical and the second systematic. A fully correlated systematic uncertainty of 5.16%, due to the limited knowledge of the external branching fractions, affects all the intervals.

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Supplementary Material [file]

Supplementary material full pdf

 supple[..].pdf [127 KiB]
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npart_STAR.pdf [14 KiB]
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npart_STAR.pdf
pt_ALICE.pdf [15 KiB]
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pt_ALICE.pdf
y_ALICE.pdf [14 KiB]
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y_ALICE.pdf

Created on 20 April 2024.