CMS-PAS-HIN-18-017

CMS-PAS-HIN-18-017
Measurement of prompt $\rm{D_{s}^{+}}$ production in pp and PbPb collisions at ${\sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}} =$ 5.02 TeV
CMS Collaboration
November 2019

Abstract: The transverse momentum ( $p_{\mathrm{T}}$ ) spectra of prompt $\mathrm{D_{s}^{+}}$ mesons and charge conjugates are measured in pp and PbPb collisions at a center-of-mass energy of 5.02 TeV per nucleon pair using the CMS detector at the LHC. The measurement is performed through the ${\mathrm D_{s}^{+}} \to \phi \pi^{+} \to \mathrm{K^{+}K^{-}}\pi^{+}$ decay channels with the $\mathrm{D_{s}^{+}}$ rapidity range $\|y\| <$ 1.0 . The $\mathrm{D_{s}^{+}}$ production in the $p_{\mathrm{T}}$ range from 2 (6) GeV/ $c$ to 40 GeV/ $c$ in pp (PbPb) collisions is measured. Suppression of the $\mathrm{D_{s}^{+}}$ nuclear modification factor ( $R_{\mathrm{AA}}$ ) in PbPb collisions suggests a strong interaction between charm quarks and the quark-gluon plasma. The double ratio of prompt $\mathrm{D_{s}^{+}}$ to prompt ${\mathrm D^{0}}$ production in pp and PbPb is consistent with a PHSD model calculation and consistent with unity, which indicates that strange charm meson enhancement in PbPb collisions is not significant in the measured $\mathrm{D_{s}^{+}}$ $p_{\mathrm{T}}$ interval.
Links: CDS record (PDF) ; inSPIRE record ; CADI line (restricted) ;

Figures & Tables	Summary	References	CMS Publications

Figures
png pdf	Figure 1: Invariant mass distributions of ${\mathrm D_{s}^{+}}$ candidates with ${p_{\mathrm{T}}} =$ 6-8 GeV/ $c$ (left) and 10-20 GeV/ $c$ (right) in pp (top) and PbPb (bottom) collisions at 5.02 TeV. The red solid line represents the full fit and the blue dashed line represents the background component.
png pdf	Figure 1-a: Invariant mass distributions of ${\mathrm D_{s}^{+}}$ candidates with ${p_{\mathrm{T}}} =$ 6-8 GeV/ $c$ (left) and 10-20 GeV/ $c$ (right) in pp (top) and PbPb (bottom) collisions at 5.02 TeV. The red solid line represents the full fit and the blue dashed line represents the background component.
png pdf	Figure 1-b: Invariant mass distributions of ${\mathrm D_{s}^{+}}$ candidates with ${p_{\mathrm{T}}} =$ 6-8 GeV/ $c$ (left) and 10-20 GeV/ $c$ (right) in pp (top) and PbPb (bottom) collisions at 5.02 TeV. The red solid line represents the full fit and the blue dashed line represents the background component.
png pdf	Figure 1-c: Invariant mass distributions of ${\mathrm D_{s}^{+}}$ candidates with ${p_{\mathrm{T}}} =$ 6-8 GeV/ $c$ (left) and 10-20 GeV/ $c$ (right) in pp (top) and PbPb (bottom) collisions at 5.02 TeV. The red solid line represents the full fit and the blue dashed line represents the background component.
png pdf	Figure 1-d: Invariant mass distributions of ${\mathrm D_{s}^{+}}$ candidates with ${p_{\mathrm{T}}} =$ 6-8 GeV/ $c$ (left) and 10-20 GeV/ $c$ (right) in pp (top) and PbPb (bottom) collisions at 5.02 TeV. The red solid line represents the full fit and the blue dashed line represents the background component.
png pdf	Figure 2: Product of acceptance and efficiency for prompt ${\mathrm D_{s}^{+}}$ (Red) and nonprompt ${\mathrm D_{s}^{+}}$ (Blue) as a function of ${p_{\mathrm{T}}}$ in pp (left) and PbPb (right) collisions at 5.02 TeV.
png pdf	Figure 2-a: Product of acceptance and efficiency for prompt ${\mathrm D_{s}^{+}}$ (Red) and nonprompt ${\mathrm D_{s}^{+}}$ (Blue) as a function of ${p_{\mathrm{T}}}$ in pp (left) and PbPb (right) collisions at 5.02 TeV.
png pdf	Figure 2-b: Product of acceptance and efficiency for prompt ${\mathrm D_{s}^{+}}$ (Red) and nonprompt ${\mathrm D_{s}^{+}}$ (Blue) as a function of ${p_{\mathrm{T}}}$ in pp (left) and PbPb (right) collisions at 5.02 TeV.
png pdf	Figure 3: Invariant mass fit of kaon pair of ${\rm D_{s}^{+}}$ candidate in pp (left) and PbPb (right) collisions at 5.02 TeV.
png pdf	Figure 3-a: Invariant mass fit of kaon pair of ${\rm D_{s}^{+}}$ candidate in pp (left) and PbPb (right) collisions at 5.02 TeV.
png pdf	Figure 3-b: Invariant mass fit of kaon pair of ${\rm D_{s}^{+}}$ candidate in pp (left) and PbPb (right) collisions at 5.02 TeV.
png pdf	Figure 4: ${p_{\mathrm{T}}}$ differential cross section of ${\rm D_{s}^{+}}$ in pp and PbPb at 5.02 TeV. The vertical bars (boxes) represent the statistical (systematic) uncertainties. The red dots reprsent $p_{\mathrm{T}}$ -differential cross section of ${\rm D_{s}^{+}}$ in pp collisions and the blue dots represnt $p_{\mathrm{T}}$ -differential corrected yield of ${\rm D_{s}^{+}}$ mesons scaled by $T_{\mathrm{AA}}$ in PbPb collisions. The black solid line represent the PYTHIA 8 calculation. The lower panel shows the ratio between data and PYTHIA 8 calculation.
png pdf	Figure 5: (left) nuclear modification factor of ${\rm D_{s}^{+}}$ (right) ${\rm D_{s}^{+}}$ / ${\rm D^{0}}$ in pp and PbPb. The vertical bars (boxes) represent the statistical (systematic) uncertainties. The lower panel shows the double ratio of ${\rm D_{s}^{+}}$ / ${\rm D^{0}}$ in PbPb over in pp. The magenta and violet lines show the PHSD [59] [60] calculation, and the green line shows the TAMU [61] calculation. The global systematic uncertainty is represented by the grey box at ${\rm R_{\mathrm{AA}}} =$ 1.
png pdf	Figure 5-a: (left) nuclear modification factor of ${\rm D_{s}^{+}}$ (right) ${\rm D_{s}^{+}}$ / ${\rm D^{0}}$ in pp and PbPb. The vertical bars (boxes) represent the statistical (systematic) uncertainties. The lower panel shows the double ratio of ${\rm D_{s}^{+}}$ / ${\rm D^{0}}$ in PbPb over in pp. The magenta and violet lines show the PHSD [59] [60] calculation, and the green line shows the TAMU [61] calculation. The global systematic uncertainty is represented by the grey box at ${\rm R_{\mathrm{AA}}} =$ 1.
png pdf	Figure 5-b: (left) nuclear modification factor of ${\rm D_{s}^{+}}$ (right) ${\rm D_{s}^{+}}$ / ${\rm D^{0}}$ in pp and PbPb. The vertical bars (boxes) represent the statistical (systematic) uncertainties. The lower panel shows the double ratio of ${\rm D_{s}^{+}}$ / ${\rm D^{0}}$ in PbPb over in pp. The magenta and violet lines show the PHSD [59] [60] calculation, and the green line shows the TAMU [61] calculation. The global systematic uncertainty is represented by the grey box at ${\rm R_{\mathrm{AA}}} =$ 1.

Tables
png pdf	Table 1: Summary of systematic uncertainties. The ranges quoted cover the ${p_{\mathrm{T}}}$ bins.

Summary

In this note, the

$p_{\mathrm{T}}$ -differential cross sections of prompt

$\mathrm{D_s}$ mesons and prompt

$\mathrm{D_s}$ nuclear modification factors in central rapidity (

$|y| <$ 1) in pp and PbPb collisions at

${\sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}} =$ 5.02 TeV are presented. The prompt

$\mathrm{D_s}$

$p_{\mathrm{T}}$ -differential cross section in pp is found to be significantly lower than PYTHIA 8 calculations. The nuclear modification of prompt

$\mathrm{D_s}$ is below unity which indicates strong interaction between charm quarks and the QGP medium. The ratio of prompt

$\mathrm{D_s}$ /

$\mathrm{D^0}$ in pp is consistent with PYTHIA 8 and model calculations. The double ratio of prompt

$\mathrm{D_s}$ /

$\mathrm{D^0}$ in PbPb over pp is consistent with unity, which is in agreement with the PHSD calculation. The

$\mathrm{D_s}$ production in PbPb collsions do not show a significant enhancement relative to in pp collisions in the measured

${p_{\mathrm{T}}}$ range. Low

${p_{\mathrm{T}}}$ measurements with higher precision from the upcoming high-luminosity LHC heavy-ion runs could provide clearer information about the charm quark hadronization in QGP.

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