Inclusive $\pi^0$, $\eta$, and direct photon production at high transverse momentum in $p+p$ and $d+$Au collisions at $\sqrt{s_{NN}}=200$ GeV

The collaboration
Phys.Rev.C 81 (2010) 064904, 2010.

Abstract (data abstract)
We report a measurement of high-$p_T$ inclusive $\pi^0$, $\eta$, and direct photon production in p+p and d+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV at midrapidity (0 < $\eta$ < 1). Photons from the decay $\pi^0$ -> $\gamma\gamma$ were detected in the Barrel Electromagnetic Calorimeter of the STAR experiment at the Relativistic Heavy Ion Collider. The $\eta$ -> $\gamma\gamma$ decay was also observed and constituted the first eta measurement by STAR. The first direct photon cross section measurement by STAR is also presented, the signal was extracted statistically by subtracting the $\pi^0$, $\eta$, and $\omega$(782) decay background from the inclusive photon distribution observed in the calorimeter. The analysis is described in detail, and the results are found to be in good agreement with earlier measurements and with next-to-leading order perturbative QCD calculations.

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Data from Figure 22a

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Cross sections for inclusive $\pi^0$ production in p + p and d + Au collisions at $\sqrt{s_{NN}}$ = 200 GeV....

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Data from Figure 24a

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The $\eta/\pi^0$ ratio measured in p + p collisions at $\sqrt{s_{NN}}$ = 200 GeV, compared to the PHENIX measurements [27]...

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Data from Figure 24b

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The $\eta/\pi^0$ ratio measured in d + Au collisions at $\sqrt{s_{NN}}$ = 200 GeV, compared to the PHENIX measurements [27]...

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Data from Figure 25a

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Nuclear modification factor $R_{dA}$ for $\pi^0$, d + Au, compared to the STAR $\pi^{+-}$ [23,24] and PHENIX $\pi^0$ measurements [27,28]....

• #### Figure 25b

Data from Figure 25b

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Nuclear modification factor $R_{dA}$ for eta, d + Au, compared to PHENIX $\eta$ measurements [27,28]. Nucleon-nucleon inelastic cross section $\sigma^{NN}$...

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Data from Figure 26

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Nuclear modification factor $R_{CP}$ for $\pi^0$ measured in d + Au collisions, compared to STAR $\pi^{+-}$ measurements [24]. Peripheral d...

• #### Figure 27a

Data from Figure 27a

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Direct photon yield in p + p collisions at $\sqrt{s_{NN}}$ = 200 GeV in terms of the double ration $R_{\gamma}$....

• #### Figure 27b

Data from Figure 27b

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Direct photon yield in d + Au collisions at $\sqrt{s_{NN}}$ = 200 GeV in terms of the double ration $R_{\gamma}$....

• #### Figure 28

Data from Figure 28

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Cross sections for direct photon production at midrapidity in p + p and d + Au collisions at $\sqrt{s_{NN}}$ =...