cometadata/datacite-titles-descriptions-related-identifiers huggingface dataset:
DOI: 10.17182/hepdata.144439.v1/t58
title: "Eff_SRD_bin2" of "A search for top-squark pair production, in final states containing a top quark, a charm quark and missing transverse momentum, using the 139 fb$^{-1}$ of $pp$ collision data collected by the ATLAS detector"

description: Signal efficiency in the SRD1000 region in the $\tilde{t}_1 - \tilde\chi^0_1$ mass plane, assuming BR$(\tilde{t}_1 \rightarrow t + \tilde\chi^0_1) = 0.5$.
description: No data abstract available.
DOI: 10.17182/hepdata.144439.v1/t59
title: "Acc_SRD_bin3" of "A search for top-squark pair production, in final states containing a top quark, a charm quark and missing transverse momentum, using the 139 fb$^{-1}$ of $pp$ collision data collected by the ATLAS detector"

description: Signal acceptance in the SRD1250 region in the $\tilde{t}_1 - \tilde\chi^0_1$ mass plane, assuming BR$(\tilde{t}_1 \rightarrow t + \tilde\chi^0_1) = 0.5$. Please mind that the acceptance given in the table is multiplied by factor of $10^{3}$ (a factor of 10 larger than in the plots).
description: No data abstract available.
DOI: 10.17182/hepdata.144439.v1/t60
title: "Eff_SRD_bin3" of "A search for top-squark pair production, in final states containing a top quark, a charm quark and missing transverse momentum, using the 139 fb$^{-1}$ of $pp$ collision data collected by the ATLAS detector"

description: Signal efficiency in the SRD1250 region in the $\tilde{t}_1 - \tilde\chi^0_1$ mass plane, assuming BR$(\tilde{t}_1 \rightarrow t + \tilde\chi^0_1) = 0.5$.
description: No data abstract available.
DOI: 10.17182/hepdata.144439.v1/t61
title: "Acc_SRD_bin4" of "A search for top-squark pair production, in final states containing a top quark, a charm quark and missing transverse momentum, using the 139 fb$^{-1}$ of $pp$ collision data collected by the ATLAS detector"

description: Signal acceptance in the SRD1500 region in the $\tilde{t}_1 - \tilde\chi^0_1$ mass plane, assuming BR$(\tilde{t}_1 \rightarrow t + \tilde\chi^0_1) = 0.5$. Please mind that the acceptance given in the table is multiplied by factor of $10^{3}$ (a factor of 10 larger than in the plots).
description: No data abstract available.
DOI: 10.17182/hepdata.144439.v1/t62
title: "Eff_SRD_bin4" of "A search for top-squark pair production, in final states containing a top quark, a charm quark and missing transverse momentum, using the 139 fb$^{-1}$ of $pp$ collision data collected by the ATLAS detector"

description: Signal efficiency in the SRD1500 region in the $\tilde{t}_1 - \tilde\chi^0_1$ mass plane, assuming BR$(\tilde{t}_1 \rightarrow t + \tilde\chi^0_1) = 0.5$.
description: No data abstract available.
DOI: 10.17182/hepdata.144439.v1/t63
title: "Acc_SRD_bin5" of "A search for top-squark pair production, in final states containing a top quark, a charm quark and missing transverse momentum, using the 139 fb$^{-1}$ of $pp$ collision data collected by the ATLAS detector"

description: Signal acceptance in the SRD1750 region in the $\tilde{t}_1 - \tilde\chi^0_1$ mass plane, assuming BR$(\tilde{t}_1 \rightarrow t + \tilde\chi^0_1) = 0.5$. Please mind that the acceptance given in the table is multiplied by factor of $10^{3}$ (a factor of 10 larger than in the plots).
description: No data abstract available.
DOI: 10.17182/hepdata.144439.v1/t64
title: "Eff_SRD_bin5" of "A search for top-squark pair production, in final states containing a top quark, a charm quark and missing transverse momentum, using the 139 fb$^{-1}$ of $pp$ collision data collected by the ATLAS detector"

description: Signal efficiency in the SRD1750 region in the $\tilde{t}_1 - \tilde\chi^0_1$ mass plane, assuming BR$(\tilde{t}_1 \rightarrow t + \tilde\chi^0_1) = 0.5$.
description: No data abstract available.
DOI: 10.17182/hepdata.144439.v1/t65
title: "Acc_SRD_bin6" of "A search for top-squark pair production, in final states containing a top quark, a charm quark and missing transverse momentum, using the 139 fb$^{-1}$ of $pp$ collision data collected by the ATLAS detector"

description: Signal acceptance in the SRD2000 region in the $\tilde{t}_1 - \tilde\chi^0_1$ mass plane, assuming BR$(\tilde{t}_1 \rightarrow t + \tilde\chi^0_1) = 0.5$. Please mind that the acceptance given in the table is multiplied by factor of $10^{3}$ (a factor of 10 larger than in the plots).
description: No data abstract available.
DOI: 10.17182/hepdata.144439.v1/t66
title: "Eff_SRD_bin6" of "A search for top-squark pair production, in final states containing a top quark, a charm quark and missing transverse momentum, using the 139 fb$^{-1}$ of $pp$ collision data collected by the ATLAS detector"

description: Signal efficiency in the SRD2000 region in the $\tilde{t}_1 - \tilde\chi^0_1$ mass plane, assuming BR$(\tilde{t}_1 \rightarrow t + \tilde\chi^0_1) = 0.5$.
description: No data abstract available.
DOI: 10.17182/hepdata.144480.v2/t1
title: "Figure 3" of "Reaction plane correlated triangular flow in Au+Au collisions at $\mathbf{\sqrt{s_{\textrm{NN}}}=3}$ GeV"

description: Event plane resolutions for calculating $v_3\{\Psi_1\}$ as a function of centrality from $\sqrt{s_{\textrm{NN}}}=3$ GeV Au+Au collisions at STAR.
description: No data abstract available.
DOI: 10.17182/hepdata.144480.v2/t2
title: "Figure 4" of "Reaction plane correlated triangular flow in Au+Au collisions at $\mathbf{\sqrt{s_{\textrm{NN}}}=3}$ GeV"

description: $v_3\{\Psi_1\}$ vs. centrality for $\pi^+$, $\pi^-$, and protons using the event plane method in $\sqrt{s_{\textrm{NN}}}=3$ GeV Au+Au collisions at STAR.
description: No data abstract available.
DOI: 10.17182/hepdata.144480.v2/t3
title: "Figure 5" of "Reaction plane correlated triangular flow in Au+Au collisions at $\mathbf{\sqrt{s_{\textrm{NN}}}=3}$ GeV"

description: $v_3\{\Psi_1\}$ vs. centrality for $K^+$, and $K^-$ using the event plane method in $\sqrt{s_{\textrm{NN}}}=3$ GeV Au+Au collisions at STAR.
description: No data abstract available.
DOI: 10.17182/hepdata.144480.v1/t1
title: "Figure 3" of "Reaction plane correlated triangular flow in Au+Au collisions at $\mathbf{\sqrt{s_{\textrm{NN}}}=3}$ GeV"

description: Event plane resolutions for calculating $v_3\{\Psi_1\}$ as a function of centrality from $\sqrt{s_{\textrm{NN}}}=3$ GeV Au+Au collisions at STAR.
description: No data abstract available.
DOI: 10.17182/hepdata.144480.v1/t2
title: "Figure 4" of "Reaction plane correlated triangular flow in Au+Au collisions at $\mathbf{\sqrt{s_{\textrm{NN}}}=3}$ GeV"

description: $v_3\{\Psi_1\}$ vs. centrality for $\pi^+$, $\pi^-$, and protons using the event plane method in $\sqrt{s_{\textrm{NN}}}=3$ GeV Au+Au collisions at STAR.
description: No data abstract available.
DOI: 10.17182/hepdata.144480.v1/t3
title: "Figure 5" of "Reaction plane correlated triangular flow in Au+Au collisions at $\mathbf{\sqrt{s_{\textrm{NN}}}=3}$ GeV"

description: $v_3\{\Psi_1\}$ vs. centrality for $K^+$, and $K^-$ using the event plane method in $\sqrt{s_{\textrm{NN}}}=3$ GeV Au+Au collisions at STAR.
description: No data abstract available.
DOI: 10.17182/hepdata.144480.v2/t4
title: "Figure 6" of "Reaction plane correlated triangular flow in Au+Au collisions at $\mathbf{\sqrt{s_{\textrm{NN}}}=3}$ GeV"

description: $v_3\{\Psi_1\}$ vs. rapidity for protons in three large centrality bins from a symmetric acceptance across midrapidity in $\sqrt{s_{\textrm{NN}}}=3$ GeV Au+Au collisions at STAR. Protons exhibit an increasingly negative slope as the centrality increases.
description: No data abstract available.
DOI: 10.17182/hepdata.144480.v2/t5
title: "Figure 7" of "Reaction plane correlated triangular flow in Au+Au collisions at $\mathbf{\sqrt{s_{\textrm{NN}}}=3}$ GeV"

description: $v_3\{\Psi_1\}$ vs. rapidity for protons in three large centrality bins from only the backward region in $\sqrt{s_{\textrm{NN}}}=3$ GeV Au+Au collisions at STAR. Note that the $p_{\mathrm{T}}$ acceptance extends to a lower limit than in Fig. 6.
description: No data abstract available.
DOI: 10.17182/hepdata.144480.v2/t6
title: "Figure 8" of "Reaction plane correlated triangular flow in Au+Au collisions at $\mathbf{\sqrt{s_{\textrm{NN}}}=3}$ GeV"

description: $v_3\{\Psi_1\}$ vs. $p_{\mathrm{T}}$ for protons in three large centrality bins in $\sqrt{s_{\textrm{NN}}}=3$ GeV Au+Au collisions at STAR. $v_3\{\Psi_1\}$ becomes increasingly negative as $p_{\mathrm{T}}$ and centrality increase.
description: No data abstract available.
DOI: 10.17182/hepdata.144480.v1/t4
title: "Figure 6" of "Reaction plane correlated triangular flow in Au+Au collisions at $\mathbf{\sqrt{s_{\textrm{NN}}}=3}$ GeV"

description: $v_3\{\Psi_1\}$ vs. rapidity for protons in three large centrality bins from a symmetric acceptance across midrapidity in $\sqrt{s_{\textrm{NN}}}=3$ GeV Au+Au collisions at STAR. Protons exhibit an increasingly negative slope as the centrality increases.
description: No data abstract available.
DOI: 10.17182/hepdata.144480.v1/t5
title: "Figure 7" of "Reaction plane correlated triangular flow in Au+Au collisions at $\mathbf{\sqrt{s_{\textrm{NN}}}=3}$ GeV"

description: $v_3\{\Psi_1\}$ vs. rapidity for protons in three large centrality bins from only the backward region in $\sqrt{s_{\textrm{NN}}}=3$ GeV Au+Au collisions at STAR. Note that the $p_{\mathrm{T}}$ acceptance extends to a lower limit than in Fig. 6.
description: No data abstract available.
DOI: 10.17182/hepdata.144480.v1/t6
title: "Figure 8" of "Reaction plane correlated triangular flow in Au+Au collisions at $\mathbf{\sqrt{s_{\textrm{NN}}}=3}$ GeV"

description: $v_3\{\Psi_1\}$ vs. $p_{\mathrm{T}}$ for protons in three large centrality bins in $\sqrt{s_{\textrm{NN}}}=3$ GeV Au+Au collisions at STAR. $v_3\{\Psi_1\}$ becomes increasingly negative as $p_{\mathrm{T}}$ and centrality increase.
description: No data abstract available.
DOI: 10.17182/hepdata.144506.v1/t1
title: "Signal region 9-bin grid yields" of "Search for non-resonant production of semi-visible jets using Run~2 data in ATLAS"

description: The post-fit yields in the nine bins of the $(p_\textrm{T}^{\textrm{bal}}, |\phi_{\textrm{max}} - \phi_{\textrm{min}}|)$ grid. Error band includes all the systematic uncertainties.
description: No data abstract available.
DOI: 10.17182/hepdata.144506.v1/t2
title: "$H_{\text{T}}$ distribution" of "Search for non-resonant production of semi-visible jets using Run~2 data in ATLAS"

description: The post-fit distributions of HT for the SR. Data are compared with background predictions, and six signal predictions covering a representative mediator mass and invisible fraction range are overlaid. The uncertainties include all systematic and statistical components. The last bin contains the overflow.
description: No data abstract available.
DOI: 10.17182/hepdata.144506.v1/t3
title: "$E_{\text{T}}^{\text{miss}}$ distribution" of "Search for non-resonant production of semi-visible jets using Run~2 data in ATLAS"

description: The post-fit distributions of $E_{\text{T}}^{\text{miss}}$ for the SR. Data are compared with background predictions, and six signal predictions covering a representative mediator mass and invisible fraction range are overlaid. The uncertainties include all systematic and statistical components. The last bin contains the overflow.
description: No data abstract available.
DOI: 10.17182/hepdata.144506.v1/t10
title: "SVJ R$_{inv}$ = 0.8 limits" of "Search for non-resonant production of semi-visible jets using Run~2 data in ATLAS"

description: Observed 95% CL limits on the t-channel production cross-section for semi-visible jets for R$_{inv}$ = 0.8.
description: No data abstract available.
DOI: 10.17182/hepdata.144506.v1/t11
title: "SVJ R$_{inv}$ = 0.9 limits" of "Search for non-resonant production of semi-visible jets using Run~2 data in ATLAS"

description: Observed 95% CL limits on the t-channel production cross-section for semi-visible jets for R$_{inv}$ = 0.9.
description: No data abstract available.
DOI: 10.17182/hepdata.144506.v1/t12
title: "Signal cross-section" of "Search for non-resonant production of semi-visible jets using Run~2 data in ATLAS"

description: The LO theory prediction (for λ=1).
description: No data abstract available.
DOI: 10.17182/hepdata.144506.v1/t4
title: "$p_\textrm{T}^{\textrm{bal}}$ distribution" of "Search for non-resonant production of semi-visible jets using Run~2 data in ATLAS"

description: The post-fit distributions of $p_\textrm{T}^{\textrm{bal}}$ for the SR. Data are compared with background predictions, and six signal predictions covering a representative mediator mass and invisible fraction range are overlaid. The uncertainties include all systematic and statistical components. The last bin contains the overflow.
description: No data abstract available.
DOI: 10.17182/hepdata.144506.v1/t5
title: "|$\phi_{\textrm{max}} - \phi_{\textrm{min}}$| distribution" of "Search for non-resonant production of semi-visible jets using Run~2 data in ATLAS"

description: The post-fit distributions of |$\phi_{\textrm{max}} - \phi_{\textrm{min}}$| for the SR. Data are compared with background predictions, and six signal predictions covering a representative mediator mass and invisible fraction range are overlaid. The uncertainties include all systematic and statistical components. The last bin contains the overflow.
description: No data abstract available.
DOI: 10.17182/hepdata.144506.v1/t6
title: "SVJ R$_{inv}$ = 0.1 limits" of "Search for non-resonant production of semi-visible jets using Run~2 data in ATLAS"

description: Observed 95% CL limits on the t-channel production cross-section for semi-visible jets for R$_{inv}$ = 0.1.
description: No data abstract available.
DOI: 10.17182/hepdata.144506.v1/t7
title: "SVJ R$_{inv}$ = 0.2 limits" of "Search for non-resonant production of semi-visible jets using Run~2 data in ATLAS"

description: Observed 95% CL limits on the t-channel production cross-section for semi-visible jets for R$_{inv}$ = 0.2.
description: No data abstract available.
DOI: 10.17182/hepdata.144506.v1/t8
title: "SVJ R$_{inv}$ = 0.4 limits" of "Search for non-resonant production of semi-visible jets using Run~2 data in ATLAS"

description: Observed 95% CL limits on the t-channel production cross-section for semi-visible jets for R$_{inv}$ = 0.4.
description: No data abstract available.
DOI: 10.17182/hepdata.144506.v1/t9
title: "SVJ R$_{inv}$ = 0.6 limits" of "Search for non-resonant production of semi-visible jets using Run~2 data in ATLAS"

description: Observed 95% CL limits on the t-channel production cross-section for semi-visible jets for R$_{inv}$ = 0.6.
description: No data abstract available.
DOI: 10.17182/hepdata.144506.v1/t13
title: "Cutflow table for 6 signal points" of "Search for non-resonant production of semi-visible jets using Run~2 data in ATLAS"

description: Cutflow table for 6 signals of different mediator masses and R$_{inv}$ fractions.
description: No data abstract available.
DOI: 10.17182/hepdata.144507.v1/t1
title: "Table 1" of "Observation of $WZ\gamma$ production in $pp$ collisions at $\sqrt{s}=13$ TeV with the ATLAS detector"

description: Events in bins of the photon $p_{\mathrm{T}}^{\gamma}$ in the SR.
description: It reports the observation of $WZ\gamma$ production and a measurement of its cross-section using $140.1 \pm 1.2$ fb$^{-1}$ of proton-proton collision data recorded at a center-of-mass energy of 13 TeV by the ATLAS detector at the Large Hadron Collider.

The $WZ\gamma$ production cross-section, with both the $W$ and $Z$ bosons decaying leptonically (leptons are either electron or muon), is measured in a fiducial phase-space region defined such that the leptons and the photon have high transverse momentum and the photon is isolated. The cross-section is found to be $2.01 \pm 0.30 (stat.) \pm 0.16 (syst.) fb$. The corresponding Standard Model predicted cross-section calculated at next-to-leading order in perturbative quantum chromodynamics and at leading order in the electroweak coupling constant is $1.50 \pm 0.06 fb$. The observed significance of the $WZ\gamma$ signal is $6.3\sigma$, compared with an expected significance of $5.0\sigma$.
DOI: 10.17182/hepdata.144507.v1/t2
title: "Table 2" of "Observation of $WZ\gamma$ production in $pp$ collisions at $\sqrt{s}=13$ TeV with the ATLAS detector"

description: Events in bins of the $p_{\mathrm{T}}^{\ell_{1}}$ in the SR.
description: It reports the observation of $WZ\gamma$ production and a measurement of its cross-section using $140.1 \pm 1.2$ fb$^{-1}$ of proton-proton collision data recorded at a center-of-mass energy of 13 TeV by the ATLAS detector at the Large Hadron Collider.

The $WZ\gamma$ production cross-section, with both the $W$ and $Z$ bosons decaying leptonically (leptons are either electron or muon), is measured in a fiducial phase-space region defined such that the leptons and the photon have high transverse momentum and the photon is isolated. The cross-section is found to be $2.01 \pm 0.30 (stat.) \pm 0.16 (syst.) fb$. The corresponding Standard Model predicted cross-section calculated at next-to-leading order in perturbative quantum chromodynamics and at leading order in the electroweak coupling constant is $1.50 \pm 0.06 fb$. The observed significance of the $WZ\gamma$ signal is $6.3\sigma$, compared with an expected significance of $5.0\sigma$.
DOI: 10.17182/hepdata.144507.v1/t3
title: "Table 3" of "Observation of $WZ\gamma$ production in $pp$ collisions at $\sqrt{s}=13$ TeV with the ATLAS detector"

description: Events in bins of the $m(\ell\ell)$ in the SR.
description: It reports the observation of $WZ\gamma$ production and a measurement of its cross-section using $140.1 \pm 1.2$ fb$^{-1}$ of proton-proton collision data recorded at a center-of-mass energy of 13 TeV by the ATLAS detector at the Large Hadron Collider.

The $WZ\gamma$ production cross-section, with both the $W$ and $Z$ bosons decaying leptonically (leptons are either electron or muon), is measured in a fiducial phase-space region defined such that the leptons and the photon have high transverse momentum and the photon is isolated. The cross-section is found to be $2.01 \pm 0.30 (stat.) \pm 0.16 (syst.) fb$. The corresponding Standard Model predicted cross-section calculated at next-to-leading order in perturbative quantum chromodynamics and at leading order in the electroweak coupling constant is $1.50 \pm 0.06 fb$. The observed significance of the $WZ\gamma$ signal is $6.3\sigma$, compared with an expected significance of $5.0\sigma$.
DOI: 10.17182/hepdata.144507.v1/t4
title: "Table 4" of "Observation of $WZ\gamma$ production in $pp$ collisions at $\sqrt{s}=13$ TeV with the ATLAS detector"

description: Events in bins of the $E_{miss}^T$ in the SR.
description: It reports the observation of $WZ\gamma$ production and a measurement of its cross-section using $140.1 \pm 1.2$ fb$^{-1}$ of proton-proton collision data recorded at a center-of-mass energy of 13 TeV by the ATLAS detector at the Large Hadron Collider.

The $WZ\gamma$ production cross-section, with both the $W$ and $Z$ bosons decaying leptonically (leptons are either electron or muon), is measured in a fiducial phase-space region defined such that the leptons and the photon have high transverse momentum and the photon is isolated. The cross-section is found to be $2.01 \pm 0.30 (stat.) \pm 0.16 (syst.) fb$. The corresponding Standard Model predicted cross-section calculated at next-to-leading order in perturbative quantum chromodynamics and at leading order in the electroweak coupling constant is $1.50 \pm 0.06 fb$. The observed significance of the $WZ\gamma$ signal is $6.3\sigma$, compared with an expected significance of $5.0\sigma$.
DOI: 10.17182/hepdata.144508.v1/t1
title: "Measured and predicted fiducial cross sections" of "Observation of $W\gamma\gamma$ triboson production in proton-proton collisions at $\sqrt{s} = 13$ TeV with the ATLAS detector"

description: The measured fiducial $W(\rightarrow e\nu / \mu\nu)\gamma\gamma$ integrated cross section compared with both the signal event generator predictions.
description: This letter reports the observation of $W(\ell\nu)\gamma\gamma$ production in proton-proton collisions. This measurement uses the full Run~2 sample of events recorded at a \com energy of $\sqrt{s} = 13$~TeV by the ATLAS detector at the LHC, corresponding to an integrated luminosity of 140~fb$^{-1}$. Events with a leptonically-decaying $W$ boson and at least two photons are considered. The background-only hypothesis is rejected with an observed and expected significance of $5.6$ standard deviations. The inclusive fiducial production cross section of $W(e\nu)\gamma\gamma$ and $W(\mu\nu)\gamma\gamma$ events is measured to be $\sigma_{\mathrm{fid}} = 13.8 \pm 1.1 (\mathrm{stat}) \substack{+2.1 \\ -2.0} (\mathrm{syst}) \pm 0.1 (\mathrm{lumi})$~fb, in agreement with the Standard Model prediction.
DOI: 10.17182/hepdata.144510.v1/t1
title: "Figure 1" of "Observation of direct-photon collective flow in sqrt(s_NN)=200 GeV Au+Au collisions"

description: $v_2$ in minimum bias collisions, using two different reaction plane detectors: (solid black circles) BBC and (solid red squares) RXN for (a) $\pi^0$, (b) inclusive photon, and (c) direct photon.
description: The second Fourier component $v_2$ of the azimuthal anisotropy with respect to the reaction plane was measured for direct photons at midrapidity and transverse momentum ($p_T$) of 1-13 GeV/$c$ in Au+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV. Previous measurements of this quantity for hadrons with $p_T$ &lt; 6 GeV/$c$ indicate that the medium behaves like a nearly perfect fluid, while for $p_T$ &gt; 6 GeV/$c$ a reduced anisotropy is interpreted in terms of a path-length dependence for parton energy loss. In this measurement with the PHENIX detector at the Relativistic Heavy Ion Collider we find that for $p_T$ &gt; 4 GeV/$c$ the anisotropy for direct photons is consistent with zero, as expected if the dominant source of direct photons is initial hard scattering. However, in the $p_T$ &lt; 4 GeV/$c$ region dominated by thermal photons, we find a substantial direct photon $v_2$ comparable to that of hadrons, whereas model calculations for thermal photons in this kinematic region significantly underpredict the observed $v_2$.
DOI: 10.17182/hepdata.144510.v1/t2
title: "Figure 2a" of "Observation of direct-photon collective flow in sqrt(s_NN)=200 GeV Au+Au collisions"

description: Centrality dependence of $v_2$ (a, c, e) for (solid-black circles) $\pi^0$, (solid-red squares) inclusive photons, and (b, d, f) (solid-black circles) direct photons measured with the BBC detector for (a),(b) minimum-bias (c),(d) 0%-20% centrality, and (e),(f) 20%-40% centrality.
description: The second Fourier component $v_2$ of the azimuthal anisotropy with respect to the reaction plane was measured for direct photons at midrapidity and transverse momentum ($p_T$) of 1-13 GeV/$c$ in Au+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV. Previous measurements of this quantity for hadrons with $p_T$ &lt; 6 GeV/$c$ indicate that the medium behaves like a nearly perfect fluid, while for $p_T$ &gt; 6 GeV/$c$ a reduced anisotropy is interpreted in terms of a path-length dependence for parton energy loss. In this measurement with the PHENIX detector at the Relativistic Heavy Ion Collider we find that for $p_T$ &gt; 4 GeV/$c$ the anisotropy for direct photons is consistent with zero, as expected if the dominant source of direct photons is initial hard scattering. However, in the $p_T$ &lt; 4 GeV/$c$ region dominated by thermal photons, we find a substantial direct photon $v_2$ comparable to that of hadrons, whereas model calculations for thermal photons in this kinematic region significantly underpredict the observed $v_2$.