Direct photon production at low transverse momentum in proton-proton collisions at $\sqrt{s}$ = 2.76 and 8 TeV

Measurements of inclusive and direct photon production at mid-rapidity in pp collisions at $\sqrt{s}$ = 2.76 and 8 TeV are presented by the ALICE experiment at the LHC. The results are reported in transverse momentum ranges of 0.4 < $p_{T}$ < 10 GeV/$c$ and 0.3 < $p_{T}$ < 16 GeV/$c$, respectively. Photons are detected with the electromagnetic calorimeter (EMCal) and via reconstruction of e$^{+}$e$^{-}$ pairs from conversions in the ALICE detector material using the central tracking system. For the final measurement of the inclusive photon spectra the results are combined in the overlapping $p_{T}$ interval of both methods. Direct photon spectra, or their upper limits at 90% C.L. are extracted using the direct photon excess ratio $R_{\gamma}$, which quantifies the ratio of inclusive photons over decay photons generated with a decay-photon simulation. An additional hybrid method, combining photons reconstructed from conversions with those identified in the EMCal, is used for the combination of the direct photon excess ratio $R_{\gamma}$ , as well as the extraction of direct photon spectra or their upper limits. While no significant signal of direct photons is seen over the full $p_{T}$ range, $R_{\gamma}$ for $p_{T}$ > 7 GeV/$c$ is at least one $\sigma$ above unity and consistent with expectations from next-to-leading order pQCD calculations.