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Centrality dependence of J/$\psi$ and $\psi$(2S) production and nuclear modification in p-Pb collisions at $\sqrt{s_{\rm NN}} =$ 8.16 TeV

The collaboration
JHEP 02 (2021) 002, 2021.

Abstract (data abstract)
The inclusive production of the J/$\psi$ and $\psi$(2S) charmonium states is studied as a function of centrality in p--Pb collisions at a centre-of-mass energy per nucleon pair $\sqrt{s_{\rm NN}} = 8.16$ TeV at the LHC. The measurement is performed in the dimuon decay channel with the ALICE apparatus in the centre-of-mass rapidity intervals $-4.46 < y_{\rm cms} < -2.96$ (Pb-going direction) and $2.03 < y_{\rm cms} < 3.53$ (p-going direction), down to zero transverse momentum ($p_{\rm T}$). The J/$\psi$ and $\psi$(2S) production cross sections are evaluated as a function of the collision centrality, estimated through the energy deposited in the zero degree calorimeter located in the Pb-going direction. The $p_{\rm T}$-differential J/$\psi$ production cross section is measured at backward and forward rapidity for several centrality classes, together with the corresponding average $\langle p_{\rm T} \rangle$ and $\langle p^{2}_{\rm T} \rangle$ values. The nuclear effects affecting the production of both charmonium states are studied using the nuclear modification factor. In the p-going direction, a suppression of the production of both charmonium states is observed, which seems to increase from peripheral to central collisions. In the Pb-going direction, however, the centrality dependence is different for the two states ':' the nuclear modification factor of the J/$\psi$ increases from below unity in peripheral collisions to above unity in central collisions, while for the $\psi$(2S) it stays below or consistent with unity for all centralities with no significant centrality dependence. The results are compared with measurements in p--Pb collisions at $\sqrt{s_{\rm NN}} = 5.02$ TeV and no significant dependence on the energy of the collision is observed. Finally, the results are compared with theoretical models implementing various nuclear matter effects.

• #### Table 1

Data from Figure 2 (Left)

10.17182/hepdata.100166.v1/t1

The $p_{\rm T}$-differential inclusive J/$\psi$ cross sections for six centrality classes at backward ($-4.46 < y_{\rm cms} < -2.96$) centre-of-mass...

• #### Table 2

Data from Figure 2 (Right)

10.17182/hepdata.100166.v1/t2

The $p_{\rm T}$-differential inclusive J/$\psi$ cross sections for six centrality classes at forward ($2.03 < y_{\rm cms} < 3.53$) centre-of-mass...

• #### Table 3

Data from Table 3

10.17182/hepdata.100166.v1/t3

• #### Table 6

Data from Figure 5 (Left) and Figure 7

10.17182/hepdata.100166.v1/t6

The $p_{\rm T}$-differential inclusive J/$\psi$ $Q_{\rm pPb}$ for six centrality classes at backward ($-4.46 < y_{\rm cms} < -2.96$) centre-of-mass...

• #### Table 7

Data from Figure 5 (Right) and Figure 8

10.17182/hepdata.100166.v1/t7

The $p_{\rm T}$-differential inclusive J/$\psi$ $Q_{\rm pPb}$ for six centrality classes at forward ($2.03 < y_{\rm cms} < 3.53$) centre-of-mass...

• #### Table 8

Data from Figure 6 (Left)

10.17182/hepdata.100166.v1/t8

The ratio of inclusive J/$\psi$ $Q_{\rm pPb}$ between peripheral to central collisions ($Q_{\rm PC}$) as function of $p_{\rm T}$ for...

• #### Table 9

Data from Figure 6 (Right)

10.17182/hepdata.100166.v1/t9

The ratio of inclusive J/$\psi$ $Q_{\rm pPb}$ between peripheral to central collisions ($Q_{\rm PC}$) as a function of $p_{\rm T}$...

• #### Table 10

Data from Figure 9 (Left)

10.17182/hepdata.100166.v1/t10

B.R.$_{\psi(\rm 2S)\rightarrow\mu^{+}\mu^{-}}{\sigma_{\psi(\rm 2S)}}$/B.R.$_{J/\psi\rightarrow\mu^{+}\mu^{-}}{\sigma_{\rm J/\psi}}$ as a function of $\langle N_{\rm coll} \rangle$ at backward ($-4.46 < y_{\rm cms} < -2.96$)...

• #### Table 11

Data from Figure 9 (Right)

10.17182/hepdata.100166.v1/t11

B.R.$_{\psi(\rm 2S)\rightarrow\mu^{+}\mu^{-}}{\sigma_{\psi(\rm 2S)}}$/B.R.$_{J/\psi\rightarrow\mu^{+}\mu^{-}}{\sigma_{\rm J/\psi}}$ as a function of $\langle N_{\rm coll} \rangle$ at forward ($2.03 < y_{\rm cms} < 3.53$)...

• #### Table 12

Data from Figure 10 (Left)

10.17182/hepdata.100166.v1/t12

• #### Table 14

Data from Figure 11 (Left)

10.17182/hepdata.100166.v1/t14

Inclusive $\psi$(2S) $Q_{\rm pPb}$ as a function of $\langle N_{\rm coll} \rangle$ at backward ($-4.46 < y_{\rm cms} < -2.96$)...

• #### Table 15

Data from Figure 11 (Right)

10.17182/hepdata.100166.v1/t15

Inclusive $\psi$(2S) $Q_{\rm pPb}$ as a function of $\langle N_{\rm coll} \rangle$ at forward ($2.03 < y_{\rm cms} < 3.53$)...

• #### Table 16

Extrapolated values from Figure 1 (in red) of ALICE-PUBLIC-2020-007

10.17182/hepdata.100166.v1/t16

• #### Table 18

Extrapolated values from Figure 2 of ALICE-PUBLIC-2020-007

10.17182/hepdata.100166.v1/t18

The rapidity differential inclusive J/$\psi$ cross sections extrapolated from existing measurements for backward ($-4.46 < y < -2.96$) rapidity interval...

• #### Table 19

Extrapolated values from Figure 2 of ALICE-PUBLIC-2020-007

10.17182/hepdata.100166.v1/t19

The rapidity differential inclusive J/$\psi$ cross sections extrapolated from existing measurements for forward ($2.03 < y < 3.53$) rapidity interval...

• #### Table 20

Extrapolated values from Figure 3 (in blue) of ALICE-PUBLIC-2020-007

10.17182/hepdata.100166.v1/t20

The $p_{\rm T}$-differential inclusive J/$\psi$ cross sections extrapolated from existing measurements at backward ($-4.46 < y < -2.96$) rapidity in...

• #### Table 21

Extrapolated values from Figure 3 (in red) of ALICE-PUBLIC-2020-007

10.17182/hepdata.100166.v1/t21

The $p_{\rm T}$-differential inclusive J/$\psi$ cross sections extrapolated from existing measurements at forward ($2.03 < y < 3.53$) rapidity in...

• #### Table 22

Extrapolated values from Figure 4 of ALICE-PUBLIC-2020-007

10.17182/hepdata.100166.v1/t22

The values of $\langle p_{\rm T} \rangle$ and $\langle p^{2}_{\rm T} \rangle$ of inclusive J/$\psi$ at backward (\$-4.46 < y...