Measurement of $\Upsilon(1{\rm S})$ elliptic flow at forward rapidity in Pb-Pb collisions at $\sqrt{s_{\rm{NN}}}=5.02$ TeV

The ALICE collaboration Acharya, Shreyasi ; Adamova, Dagmar ; Adhya, Souvik Priyam ; et al.
Phys.Rev.Lett. 123 (2019) 192301, 2019.
Inspire Record 1742764 DOI 10.17182/hepdata.91161

The first measurement of the $\Upsilon(1{\rm S})$ elliptic flow coefficient ($v_2$) is performed at forward rapidity (2.5 $<$ $y$ $<$ 4) in Pb-Pb collisions at $\sqrt{s_{\rm NN}} = 5.02$ TeV with the ALICE detector at the LHC. The results are obtained with the scalar product method and are reported as a function of transverse momentum ($p_{\rm{T}}$) up to 15 GeV/$c$ in the 5-60% centrality interval. The measured $\Upsilon(1{\rm S})$ $v_2$ is consistent with zero and with the small positive values predicted by transport models within uncertainties. The $v_2$ coefficient in 2 $<$ $p_{\rm T}$ $<$ 15 GeV/$c$ is lower than that of inclusive J/$\psi$ mesons in the same $p_{\rm{T}}$ interval by 2.6 standard deviations. These results, combined with earlier suppression measurements, are in agreement with a scenario in which the $\Upsilon$(1S) production in Pb-Pb collisions at LHC energies is dominated by dissociation limited to the early stage of the collision whereas in the J/$\psi$ case there is substantial experimental evidence of an additional regeneration component.

4 data tables

The J/$\psi$ $v_2$ coefficient as a function of $p_{\rm T}$ in 5-60% centrality interval in Pb-Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV.

The $\Upsilon$(1S) $v_2$ coefficient as a function of $p_{\rm T}$ in 5-60% centrality interval in Pb-Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV.

The J/$\psi$ $v_2$ coefficient in three centrality intervals integrated over the transverse momentum range 2~$<$~$p_{\rm T}$~$<$~15 GeV/$c$ in Pb-Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV.

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Study of J/$\psi$ azimuthal anisotropy at forward rapidity in Pb-Pb collisions at $\sqrt{{\textit s}_{\rm NN}}$ = 5.02 TeV

The ALICE collaboration Acharya, Shreyasi ; Torales - Acosta, Fernando ; Adamova, Dagmar ; et al.
JHEP 02 (2019) 012, 2019.
Inspire Record 1706006 DOI 10.17182/hepdata.88308

The second ($v_2$) and third ($v_3$) flow harmonic coefficients of J/$\psi$ mesons are measured at forward rapidity (2.5 $<$ $y$ $<$ 4.0) in Pb-Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV with the ALICE detector at the LHC. Results are obtained with the scalar product method and reported as a function of transverse momentum, $p_{\rm{T}}$, for various collision centralities. A positive value of J/$\psi$ $v_3$ is observed with 3.7$\sigma$ significance. The measurements, compared to those of prompt D$^0$ mesons and charged particles at mid-rapidity, indicate an ordering with $v_{\rm n}$(J/$\psi$) $<v_{\rm n}$(D$^0$) $<v_{\rm n}$(h$^\pm$) (n = 2, 3) at low and intermediate $p_{\rm{T}}$ up to 6 GeV/$c$ and a convergence with $v_2$(J/$\psi$) $\approx v_2$(D$^0$) $\approx v_2$(h$^\pm$) at high $p_{\rm{T}}$ above 6-8 GeV/$c$. In semi-central collisions (5-40% and 10-50% centrality intervals) at intermediate $p_{\rm{T}}$ between 2 and 6 GeV/$c$, the ratio $v_3/v_2$ of J/$\psi$ mesons is found to be significantly lower (4.6$\sigma$) with respect to that of charged particles. In addition, the comparison to the prompt D$^0$-meson ratio in the same $p_{\rm{T}}$ interval suggests an ordering similar to that of the $v_2$ and $v_3$ coefficients. The J/$\psi$ $v_2$ coefficient is further studied using the Event Shape Engineering technique. The obtained results are found to be compatible with the expected variations of the eccentricity of the initial-state geometry.

12 data tables

The J/$\psi$ $v_2$ coefficient as a function of $p_{\rm T}$ in 0-10% centrality interval in Pb-Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV.

The J/$\psi$ $v_2$ coefficient as a function of $p_{\rm T}$ in 10-30% centrality interval in Pb-Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV.

The J/$\psi$ $v_2$ coefficient as a function of $p_{\rm T}$ in 30-50% centrality interval in Pb-Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV.

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