@article{3185926,
    title = "Direct photon production at low transverse momentum in proton-proton
collisions at root s=2.76 and 8 TeV",
    author = "Acharya, S. and Acosta, F. T. -. and Adamova, D. and Adolfsson, J. and and Aggarwal, M. M. and Rinella, G. Aglieri and Agnello, M. and Agrawal, N. and and Ahammed, Z. and Ahn, S. U. and Aiola, S. and Akindinov, A. and and Al-Turany, M. and Alam, S. N. and Albuquerque, D. S. D. and Aleksandrov, and D. and Alessandro, B. and Molina, R. Alfaro and Ali, Y. and Alici, A. and and Alkin, A. and Alme, J. and Alt, T. and Altenkamper, L. and and Altsybeev, I. and Andrei, C. and Andreou, D. and Andrews, H. A. and and Andronic, A. and Angeletti, M. and Anguelov, V. and Anson, C. and and Anticic, T. and Antinori, F. and Antonioli, P. and Anwar, R. and and Apadula, N. and Aphecetche, L. and Appelshaeuser, H. and Arcelli, S. and and Arnaldi, R. and Arnold, O. W. and Arsene, I. C. and Arslandok, M. and and Audurier, B. and Augustinus, A. and Averbeck, R. and Azmi, M. D. and and Badala, A. and Baek, Y. 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S. and and Willsher, E. and Windelband, B. and Witt, W. E. and Xu, R. and Yalcin, and S. and Yamakawa, K. and Yano, S. and Yin, Z. and Yokoyama, H. and Yoo, and I. -K. and Yoon, J. H. and Yurchenko, V. and Zaccolo, V. and Zaman, A. and and Zampolli, C. and Zanoli, H. J. C. and Zardoshti, N. and and Zarochentsev, A. and Zavada, P. and Zaviyalov, N. and Zbroszczyk, H. and and Zhalov, M. and Zhang, X. and Zhang, Y. and Zhang, Z. and Zhao, C. and and Zhigareva, N. and Zhou, D. and Zhou, Y. and Zhou, Z. and Zhu, H. and and Zhu, J. and Zhu, Y. and Zichichi, A. and Zimmermann, M. B. and Zinovjev, and G. and Zmeskal, J. and Zou, S. and ALICE Collaboration",
    journal = "Physical Review C",
    year = "2019",
    volume = "99",
    number = "2",
    publisher = "AMER PHYSICAL SOC",
    issn = "2469-9985, 2469-9993",
    doi = "10.1103/PhysRevC.99.024912",
    abstract = "Measurements of inclusive and direct photon production at midrapidity in
pp collisions at root 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."
}