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| CMS-PAS-HIN-17-003 | ||
| Elliptic flow of charm and strange hadrons in high-multiplicity pPb collisions at $\sqrt{\smash[b]{s_{\mathrm{NN}}}} = $ 8.16 TeV | ||
| CMS Collaboration | ||
| February 2018 | ||
| Abstract: First measurements of the elliptic flow of prompt $ \mathrm{D^{0}} $ mesons in comparison to $\mathrm{K^0_S}$, $\Lambda$, $\Xi^{-}$, and $\Omega^{-}$ hadrons in pPb collisions at $\sqrt{\smash[b]{s_{\mathrm{NN}}}} = $ 8.16 TeV are reported. The results are based on data collected by the CMS experiment at the LHC and are presented for particles at midrapidity with transverse momentum up to 8 GeV/c after correcting for the contribution of back-to-back jet correlations. The results are compared to PbPb collision data at $\sqrt{\smash[b]{s_{\mathrm{NN}}}} = $ 5.02 TeV for 30-50% centrality. A significant elliptic flow ($v_2$) signal is observed for all particles, in very high-multiplicity (about 200 charged particles) pPb events. When divided by the number of constituent quarks and studied as function of the transverse kinetic energy per quark, the $ \mathrm{D^{0}} $ $v_2$ values are observed to be significantly smaller than those of light flavor particles, an effect not observed in PbPb collisions. These results show a weaker collective flow associated with charm quarks than with light flavor quarks in high-multiplicity pPb collisions, and may indicate a weaker coupling between heavy quarks and the hypothesised hydrodynamic quark-gluon plasma. | ||
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Links:
CDS record (PDF) ;
inSPIRE record ;
CADI line (restricted) ;
These preliminary results are superseded in this paper, PRL 121 (2018) 082301. The superseded preliminary plots can be found here. |
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| Figures | |
png pdf |
Figure 1:
Example of the simultaneous fit to the invariant mass spectrum and $v_{2}^{S+B}(m_{\rm inv})$ in the $ {p_{{\mathrm {T}}}}$ interval 4.2-5 GeV/$c$ for events with 185 $ \leq {N_{\mathrm {trk}^{\mathrm {offline}}}} < $ 250. |
png pdf |
Figure 2:
Top: the $v_{2}^\text {sub}$ results for prompt $ {\mathrm {D^{0}}} $ meson, as well as for strange hadrons as a function of ${p_{{\mathrm {T}}}} $ for pPb collisions at $\sqrt{\smash[b]{s_{\mathrm{NN}}}} = $ 8.16 TeV with 185 $ \leq {N_{\mathrm {trk}^{\mathrm {offline}}}} < $ 250 (left) and PbPb collisions at $ \sqrt{\smash[b]{s_{\mathrm{NN}}}} = $ 5.02 TeV with centrality between 30 and 50% (right). Bottom: the $n_{\mathrm {q}}$-scaled $v_{2}^\text {sub}$ results. The $ {\mathrm {D^{0}}} $ $v_2$ data in PbPb are taken from Ref. [40]. The error bars correspond to statistical uncertainties, while the shaded areas denote the systematic uncertainties. |
| Summary |
| First measurements of elliptic azimuthal anisotropies for prompt $ \mathrm{D^{0}} $ mesons in comparison to $\mathrm{K^0_S}$, $\Lambda$, $\Xi^{-}$, and $\Omega^{-}$ hadrons in high-multiplicity pPb collisions at $\sqrt{\smash[b]{s_{\mathrm{NN}}}} = $ 8.16TeV are presented. Significant positive $v_2$ values are observed for $ \mathrm{D^{0}} $ mesons with ${p_{{\mathrm {T}}}} >$ 2 GeV/$c$. Comparing to strange hadron results, the $ \mathrm{D^{0}} $ $v_2$ values are found to be smaller at a given $ {p_{{\mathrm {T}}}}$ value, or at similar transverse kinetic energy per constituent quark after normalizing $v_2$ by the number of constituent quarks. This effect is not observed in PbPb collisions with centrality between 30 and 50%. These results may indicate a weaker coupling between heavy quarks and the hypothesised hydrodynamic QGP medium in small collision systems. |
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