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

The collaboration
No Journal Information, 2018

Abstract (data abstract)
CERN-LHC. 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 $0.4<p_{\rm T}<10$ GeV/c and $0.3<p_{\rm T}<16$ 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 $p_{\rm T}$ 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 $p_{\rm T}$ range, $R_\gamma$ for $p_{\rm T}>7$ GeV/c is at least one $\sigma$ above unity and consistent with expectations from next-to-leading order pQCD calculations.

• #### Table 1

Data from Fig. 4

10.17182/hepdata.88395.v1/t1

Double Ratio RGAMMA in inelastic pp collisions at center-of-mass energy 2.76 TeV. RGAMMA is the ratio of inclusive GAMMA to...

• #### Table 2

Data from Fig. 4

10.17182/hepdata.88395.v1/t2

Double Ratio RGAMMA in inelastic pp collisions at center-of-mass energy 8 TeV. RGAMMA is the ratio of inclusive GAMMA to...

• #### Table 3

Data from Fig. 5

10.17182/hepdata.88395.v1/t3

Invariant differential cross section of inclusive GAMMA produced in inelastic pp collisions at center-of-mass energy 2.76 TeV, the uncertainty of...

• #### Table 4

Data from Fig. 5

10.17182/hepdata.88395.v1/t4

Invariant differential cross section of inclusive GAMMA produced in inelastic pp collisions at center-of-mass energy 8 TeV, the uncertainty of...

• #### Table 5

Data from Fig. 5

10.17182/hepdata.88395.v1/t5

Invariant differential cross section of direct GAMMA produced in inelastic pp collisions at center-of-mass energy 2.76 TeV, the uncertainty of...

• #### Table 6

Data from Fig. 5

10.17182/hepdata.88395.v1/t6

Invariant differential cross section of direct GAMMA produced in inelastic pp collisions at center-of-mass energy 8 TeV, the uncertainty of...

• #### Table 7

Data from not in paper

10.17182/hepdata.88395.v1/t7

Invariant differential yield of inclusive GAMMA produced in inelastic pp collisions at center-of-mass energy 2.76 TeV. Values are given in...

• #### Table 8

Data from not in paper

10.17182/hepdata.88395.v1/t8

Invariant differential yield of inclusive GAMMA produced in inelastic pp collisions at center-of-mass energy 8 TeV. Values are given in...

• #### Table 9

Data from not in paper

10.17182/hepdata.88395.v1/t9

Invariant differential yield of direct GAMMA produced in inelastic pp collisions at center-of-mass energy 2.76 TeV. Values are given in...

• #### Table 10

Data from not in paper

10.17182/hepdata.88395.v1/t10

Invariant differential yield of direct GAMMA produced in inelastic pp collisions at center-of-mass energy 8 TeV. Values are given in...