Fit of the dielectron mass spectrum in INEL (left) and HM (right) pp collisions in the $2 < p_{\rm T,ee} < 3$ GeV/$c$ interval with a three-component fit function to extract the fraction of direct photons to inclusive photons $r$. Statistical and systematic uncertainties of the data are displayed as vertical bars and boxes, respectively. The resulting fraction of direct photons $r$ is shown together with its statistical uncertainty. The templates for dielectrons from LF, HF and direct photons are shown as different dashed lines, and the resulting fit is shown as a solid magenta line. The contributions from $\pi^{0}$ and $\eta$ mesons are also shown as separate lines. See the Appendix A of this letter for the fits of the dielectron mass spectrum in other pair transverse momentum intervals.

Direct photon fraction $r$ as a function of $p_{\rm T}$ extracted from fits to dielectron spectra in INEL (left) and HM (right) pp collisions. Statistical and systematic uncertainties of the data are displayed as vertical bars and boxes, respectively. The results in INEL pp collisions are compared to theoretical calculations of Refs. [18] and [35]. The results from HM pp data are compared to theoretical calculations of Ref. [18] for INEL pp collisions scaled by an empirical factor 7 based on Pythia calculations (blue band). The red and green bands show the calculations of Ref. [35] scaled by the factor of 4.5$-$7.5, with the width of the bands representing the range of the applied scaling factor (see the text for more details).

Direct-photon cross section (left) and invariant differential yield (right) as a function of $p_{\rm T}$ in INEL and HM pp collisions, respectively. Statistical and systematic uncertainties of the data are displayed as vertical bars and boxes, respectively. The results in INEL pp collisions are compared to theoretical calculations from Refs. [18] and [35]. The results from HM pp data are compared to theoretical calculations for INEL pp collisions scaled by an empirical factor of 4.5$-$7.5 (for Shen's calculations) and of 7 (for Vogelsang's model), see text for details. The uncertainty for Shen's pQCD calculations (green band) comes from the variation of the scaling factor, whereas the uncertainty of Vogelsang's pQCD results (blue band) is the original model uncertainty scaled by factor 7. The data points are plotted and the ratios are evaluated at the $p_{\rm T}$ values determined according to the Lafferty$-$Wyatt prescription, with the corresponding uncertainties being smaller than the marker size.

Direct photon yield at midrapidity as a function of charged-particle multiplicity ${\rm{d}N_\rm{ch}/\rm{d}\eta}$. The results from this letter are shown as full blue markers and are compared to theoretical calculations for prompt (open green circle) and prompt+thermal (open red square) yields for INEL pp collisions at $\sqrt{s} = 13$ TeV . The results from the STAR, PHENIX and ALICE collaborations are shown as full markers of various colours, and the band shows $N_{\rm coll}$-based extrapolation of pQCD calculations for pp collisions at $\sqrt{s} = 200$ GeV. The Pb$-$Pb results are compared with the theoretical prediction by Gale , which includes prompt, pre-equilibrium and thermal photons. The prompt-photon yield is computed with NLO pQCD using the INCNLO code  together with the nCTEQ15 nuclear parton distribution function, and the BFG-II fragmentation function.

Fit of the dielectron mass spectrum in INEL (left) and HM (right) pp collisions in the $1 < p_{\rm T,ee} < 2$ GeV/$c$ interval with a three-component fit function to extract the fraction of direct photons to inclusive photons $r$. Statistical and systematic uncertainties of the data are displayed as vertical bars and boxes, respectively. The resulting fraction of direct photons $r$ is shown together with its statistical uncertainty. The templates for dielectrons from LF, HF and direct photons are shown as different dashed lines, and the resulting fit is shown as a solid magenta line. The contributions from $\pi^{0}$ and $\eta$ mesons are also shown as separate lines.

Fit of the dielectron mass spectrum in INEL (left) and HM (right) pp collisions in the $3 < p_{\rm T,ee} < 6$ GeV/$c$ interval with a three-component fit function to extract the fraction of direct photons to inclusive photons $r$. Statistical and systematic uncertainties of the data are displayed as vertical bars and boxes, respectively. The resulting fraction of direct photons $r$ is shown together with its statistical uncertainty. The templates for dielectrons from LF, HF and direct photons are shown as different dashed lines, and the resulting fit is shown as a solid magenta line. The contributions from $\pi^{0}$ and $\eta$ mesons are also shown as separate lines.