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Measurement of longitudinal spin asymmetries for weak boson production in polarized proton-proton collisions at RHIC

The collaboration
Phys.Rev.Lett. 113 (2014) 072301, 2014.

Abstract (data abstract)
BNL-RHIC. We report measurements of single- and double- spin asymmetries for $W^{\pm}$ and $Z/\gamma^*$ boson production in longitudinally polarized $p+p$ collisions at $\sqrt{s} = 510$ GeV by the STAR experiment at RHIC. The asymmetries for $W^{\pm}$ were measured as a function of the decay lepton pseudorapidity, which provides a theoretically clean probe of the proton's polarized quark distributions at the scale of the $W$ mass. The results are compared to theoretical predictions, constrained by recent polarized deep inelastic scattering measurements, and show a preference for a sizable, positive up antiquark polarization in the range $0.05<x<0.2$.

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Data from Figure 1

10.17182/hepdata.73441.v1/t1

$E_T^e$ distribution of $W^{\pm}$ candidate events, background contributions, and sum of backgrounds and W -> ev MC signal. This plot...

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Data from Figure 1

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$E_T^e$ distribution of $W^{\pm}$ candidate events, background contributions, and sum of backgrounds and W -> ev MC signal. This plot...

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Data from Figure 1

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$E_T^e$ distribution of $W^{\pm}$ candidate events, background contributions, and sum of backgrounds and W -> ev MC signal. This plot...

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Data from Figure 1

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$E_T^e$ distribution of $W^{\pm}$ candidate events, background contributions, and sum of backgrounds and W -> ev MC signal. This plot...

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Data from Figure 2a

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Signed $P_T$-balance distribution for e+/e- candidates reconstructed in the EEMC.

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Data from Figure 2b

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Distribution of the product of the TPC reconstructed charge sign and $E_T/p_T$.

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Data from Figure 3

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Distribution of the invariant mass of Z/$\gamma^*$ -> e+ e- candidate events, with MC for comparison.

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Data from Figure 4

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Longitudinal single-spin asymmetry $A_L$ for W+ production as a function of lepton pseudorapidity.

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Data from Figure 4

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Longitudinal single-spin asymmetry $A_L$ for W- production as a function of lepton pseudorapidity.

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Data from Figure 4

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Longitudinal single-spin asymmetry $A_L$ for W+ production as a function of lepton pseudorapidity.

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Data from Figure 5

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Longitudinal double-spin asymmetry $A_{LL}$ for W+ production as a function of lepton pseudorapidity.

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Data from Figure 5

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Longitudinal double-spin asymmetry $A_{LL}$ for W- production as a function of lepton pseudorapidity.

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Data from Figure 5

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Longitudinal double-spin asymmetry $A_{LL}$ for theory $W^{+/-}$ production as a function of lepton pseudorapidity.