Energy Dependence of Polarized $\mathbf{\gamma\gamma\rightarrow e^{+}e^{-}}$ in Peripheral Au+Au Collisions at RHIC

The STAR collaboration
Phys.Rev.C 111 (2025) 014909, 2025.

Abstract
We report the differential yields at mid-rapidity of the Breit-Wheeler process ($\gamma\gamma\rightarrow e^{+}e^{-}$) in peripheral Au+Au collisions at $\sqrt{s_{_{\rm{NN}}}} = $ 54.4 GeV and 200 GeV with the STAR experiment at RHIC, as a function of energy $\sqrt{s_{_{\rm{NN}}}}$, $e^{+}e^{-}$ transverse momentum $p_{\rm T}$, $p_{\rm T}^{2}$, invariant mass $M_{ee}$ and azimuthal angle. In the invariant mass range of 0.4 $<$$M_{ee}$$<$ 2.6 GeV/$c^{2}$ at low transverse momentum ($p_{\rm T}$$ < $0.15 GeV/$c$), the yields increase while the pair $\sqrt{\langle p_{\rm T}^{2} \rangle}$ decreases with increasing $\sqrt{s_{_{\rm{NN}}}}$, a feature is correctly predicted by the QED calculation. The energy dependencies of the measured quantities are sensitive to the nuclear form factor, infrared divergence and photon polarization. The data are compiled and used to extract the charge radius of the Au nucleus.

  • Table from Fig. 6(a)

    Data from Fig. 6(a)

    10.17182/hepdata.153885.v1/t1

    '54.4 GeV, Centrality: 40-60%'

  • Table from Fig. 6(b)

    Data from Fig. 6(b)

    10.17182/hepdata.153885.v1/t2

    '54.4 GeV, Centrality: 60-80%'

  • Table from Fig. 6(c)

    Data from Fig. 6(c)

    10.17182/hepdata.153885.v1/t3

    '54.4 GeV, Centrality: 80-100%'

  • Table from Fig. 6(d)

    Data from Fig. 6(d)

    10.17182/hepdata.153885.v1/t4

    '200 GeV, Centrality: 80-100%'

  • Table from Fig. 7(a)

    Data from Fig. 7(a)

    10.17182/hepdata.153885.v1/t5

    '54.4 GeV, Centrality: 40-60%'

  • Table from Fig. 7(b)

    Data from Fig. 7(b)

    10.17182/hepdata.153885.v1/t6

    '54.4 GeV, Centrality: 60-80%'

  • Table from Fig. 7(c)

    Data from Fig. 7(c)

    10.17182/hepdata.153885.v1/t7

    '54.4 GeV, Centrality: 80-100%'

  • Table from Fig. 7(d)

    Data from Fig. 7(d)

    10.17182/hepdata.153885.v1/t8

    '200 GeV, Centrality: 80-100%'

  • Table1 from Fig. 8(a)

    Data from Fig. 8(a)

    10.17182/hepdata.153885.v1/t9

    '$0.4 < M_{ee} < 0.76 GeV/c^{2}$, Centrality: 40-60%'

  • Table2 from Fig. 8(a)

    Data from Fig. 8(a)

    10.17182/hepdata.153885.v1/t10

    '$0.4 < M_{ee} < 0.76 GeV/c^{2}$, Centrality: 60-80%'

  • Table3 from Fig. 8(a)

    Data from Fig. 8(a)

    10.17182/hepdata.153885.v1/t11

    '$0.4 < M_{ee} < 0.76 GeV/c^{2}$, Centrality: 80-100%'

  • Table1 from Fig. 8(b)

    Data from Fig. 8(b)

    10.17182/hepdata.153885.v1/t12

    '$0.76 < M_{ee} < 1.2 GeV/c^{2}$, Centrality: 40-60%'

  • Table2 from Fig. 8(b)

    Data from Fig. 8(b)

    10.17182/hepdata.153885.v1/t13

    '$0.76 < M_{ee} < 1.2 GeV/c^{2}$, Centrality: 60-80%'

  • Table3 from Fig. 8(b)

    Data from Fig. 8(b)

    10.17182/hepdata.153885.v1/t14

    '$0.76 < M_{ee} < 1.2 GeV/c^{2}$, Centrality: 80-100%'

  • Table1 from Fig. 8(c)

    Data from Fig. 8(c)

    10.17182/hepdata.153885.v1/t15

    '$1.2 < M_{ee} < 2.6 GeV/c^{2}$, Centrality: 40-60%'

  • Table2 from Fig. 8(c)

    Data from Fig. 8(c)

    10.17182/hepdata.153885.v1/t16

    '$1.2 < M_{ee} < 2.6 GeV/c^{2}$, Centrality: 60-80%'

  • Table3 from Fig. 8(c)

    Data from Fig. 8(c)

    10.17182/hepdata.153885.v1/t17

    '$1.2 < M_{ee} < 2.6 GeV/c^{2}$, Centrality: 80-100%'

  • Table from Fig. 9(a)

    Data from Fig. 9(a)

    10.17182/hepdata.153885.v1/t18

    '54.4 GeV, Centrality: 40-60%'

  • Table from Fig. 9(b)

    Data from Fig. 9(b)

    10.17182/hepdata.153885.v1/t19

    '54.4 GeV, Centrality: 60-80%'

  • Table from Fig. 9(c)

    Data from Fig. 9(c)

    10.17182/hepdata.153885.v1/t20

    '54.4 GeV, Centrality: 80-100%'

  • Table from Fig. 9(d)

    Data from Fig. 9(d)

    10.17182/hepdata.153885.v1/t21

    '200 GeV, Centrality: 80-100%'

  • Table1 from Fig. 10

    Data from Fig. 10

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    'Centrality: 40-60%'

  • Table2 from Fig. 10

    Data from Fig. 10

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    'Centrality: 60-80%'

  • Table from Fig. 10

    Data from Fig. 10

    10.17182/hepdata.153885.v1/t24

    'Centrality: 80-100%'

  • Table from Fig. 11(a)

    Data from Fig. 11(a)

    10.17182/hepdata.153885.v1/t25

    '54.4 GeV, Centrality: 40-60%'

  • Table from Fig. 11(b)

    Data from Fig. 11(b)

    10.17182/hepdata.153885.v1/t26

    '54.4 GeV, Centrality: 60-80%'

  • Table from Fig. 11(c)

    Data from Fig. 11(c)

    10.17182/hepdata.153885.v1/t27

    '54.4 GeV, Centrality: 80-100%'

  • Table from Fig. 11(d)

    Data from Fig. 11(d)

    10.17182/hepdata.153885.v1/t28

    '200 GeV, Centrality: 80-100%'

  • Table from Fig. 12(a)

    Data from Fig. 12(a)

    10.17182/hepdata.153885.v1/t29

    '$-2$ as a function of $p_{T}$ @ 200 GeV, Centrality: 80-100%'

  • Table from Fig. 12(b)

    Data from Fig. 12(b)

    10.17182/hepdata.153885.v1/t30

    '$-2$ as a function of $p_{T}$ @ 200 GeV, UPC'

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