Scale and isolation sensitivity of diphoton distributions at the LHC


Precision measurements of diphoton distributions at the LHC display some tension with theory predictions, obtained at next-to-next-to-leading order (NNLO) in QCD. We revisit the theoretical uncertainties arising from the approximation of the experimental photon isolation by smooth-cone isolation, and from the choice of functional form for the renormalisation and factorisation scales. We find that the resulting variations are substantial overall, and enhanced in certain regions. We discuss the infrared sensitivity at the cone boundaries in cone-based isolation in related distributions. Finally, we compare predictions made with alternative choices of dynamical scale and isolation prescriptions to experimental data from ATLAS at 8 TeV, observing improved agreement. This contrasts with previous results, highlighting that scale choice and isolation prescription are potential sources of theoretical uncertainty that were previously underestimated.

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  1. [1]

    ATLAS collaboration, Measurements of Higgs boson properties in the diphoton decay channel with 36 fb1 of pp collision data at \( \sqrt{s} \) = 13 TeV with the ATLAS detector, Phys. Rev. D 98 (2018) 052005 [arXiv:1802.04146] [INSPIRE].

  2. [2]

    CMS collaboration, A measurement of the Higgs boson mass in the diphoton decay channel, Phys. Lett. B 805 (2020) 135425 [arXiv:2002.06398] [INSPIRE].

  3. [3]

    ATLAS collaboration, Search for new phenomena in high-mass diphoton final states using 37 fb1 of proton–proton collisions collected at \( \sqrt{s} \) = 13 TeV with the ATLAS detector, Phys. Lett. B 775 (2017) 105 [arXiv:1707.04147] [INSPIRE].

  4. [4]

    CMS collaboration, Search for physics beyond the standard model in high-mass diphoton events from proton-proton collisions at \( \sqrt{s} \) = 13 TeV, Phys. Rev. D 98 (2018) 092001 [arXiv:1809.00327] [INSPIRE].

  5. [5]

    S. Frixione, Isolated photons in perturbative QCD, Phys. Lett. B 429 (1998) 369 [hep-ph/9801442] [INSPIRE].

  6. [6]

    OPAL collaboration, Measurement of isolated prompt photon production in photon photon collisions at \( \sqrt{s_{ee}} \) = 183 GeV–209 GeV, Eur. Phys. J. C 31 (2003) 491 [hep-ex/0305075] [INSPIRE].

  7. [7]

    SM, NLO Multileg Working Group collaboration, The SM and NLO Multileg Working Group: Summary report, in the proceedings of the 6th Les Houches Workshop on physics at TeV colliders, June 8–26, Les Houches, France (2009), arXiv:1003.1241 [INSPIRE].

  8. [8]

    Z. Hall and J. Thaler, Photon isolation and jet substructure, JHEP 09 (2018) 164 [arXiv:1805.11622] [INSPIRE].

    ADS  Article  Google Scholar 

  9. [9]

    E.W. Glover and A.G. Morgan, Measuring the photon fragmentation function at LEP, Z. Phys. C 62 (1994) 311 [INSPIRE].

    ADS  Article  Google Scholar 

  10. [10]

    S. Catani, L. Cieri, D. de Florian, G. Ferrera and M. Grazzini, Diphoton production at hadron colliders: a fully-differential QCD calculation at NNLO, Phys. Rev. Lett. 108 (2012) 072001 [Erratum ibid. 117 (2016) 089901] [arXiv:1110.2375] [INSPIRE].

  11. [11]

    J.M. Campbell, R. Ellis, Y. Li and C. Williams, Predictions for diphoton production at the LHC through NNLO in QCD, JHEP 07 (2016) 148 [arXiv:1603.02663] [INSPIRE].

    ADS  Article  Google Scholar 

  12. [12]

    H.A. Chawdhry, M.L. Czakon, A. Mitov and R. Poncelet, NNLO QCD corrections to three-photon production at the LHC, JHEP 02 (2020) 057 [arXiv:1911.00479] [INSPIRE].

    ADS  Article  Google Scholar 

  13. [13]

    F. Siegert, A practical guide to event generation for prompt photon production with Sherpa, J. Phys. G 44 (2017) 044007 [arXiv:1611.07226] [INSPIRE].

    ADS  Article  Google Scholar 

  14. [14]

    S. Amoroso et al., Les Houches 2019: physics at TeV colliders: standard model working group report, in the proceedings of the 11th Les Houches Workshop on Physics at TeV Colliders: PhysTeV Les Houches, June 10–28, Les Houches, France (2019), arXiv:2003.01700 [INSPIRE].

  15. [15]

    M.A. Ebert and F.J. Tackmann, Impact of isolation and fiducial cuts on qT and N-jettiness subtractions, JHEP 03 (2020) 158 [arXiv:1911.08486] [INSPIRE].

    ADS  MathSciNet  Article  Google Scholar 

  16. [16]

    S. Catani, L. Cieri, D. de Florian, G. Ferrera and M. Grazzini, Diphoton production at the LHC: a QCD study up to NNLO, JHEP 04 (2018) 142 [arXiv:1802.02095] [INSPIRE].

    ADS  Article  Google Scholar 

  17. [17]

    ATLAS collaboration, Measurements of integrated and differential cross sections for isolated photon pair production in pp collisions at \( \sqrt{s} \) = 8 TeV with the ATLAS detector, Phys. Rev. D 95 (2017) 112005 [arXiv:1704.03839] [INSPIRE].

  18. [18]

    S. Catani, M. Fontannaz, J. Guillet and E. Pilon, Isolating prompt photons with narrow cones, JHEP 09 (2013) 007 [arXiv:1306.6498] [INSPIRE].

    ADS  Article  Google Scholar 

  19. [19]

    S. Catani, M. Fontannaz, J.P. Guillet and E. Pilon, Cross-section of isolated prompt photons in hadron hadron collisions, JHEP 05 (2002) 028 [hep-ph/0204023] [INSPIRE].

  20. [20]

    T. Binoth, J.P. Guillet, E. Pilon and M. Werlen, A Full next-to-leading order study of direct photon pair production in hadronic collisions, Eur. Phys. J. C 16 (2000) 311 [hep-ph/9911340] [INSPIRE].

  21. [21]

    S. Frixione and G. Ridolfi, Jet photoproduction at HERA, Nucl. Phys. B 507 (1997) 315 [hep-ph/9707345] [INSPIRE].

  22. [22]

    S. Catani and B.R. Webber, Infrared safe but infinite: soft gluon divergences inside the physical region, JHEP 10 (1997) 005 [hep-ph/9710333] [INSPIRE].

  23. [23]

    M. Grazzini, S. Kallweit and M. Wiesemann, Fully differential NNLO computations with MATRIX, Eur. Phys. J. C 78 (2018) 537 [arXiv:1711.06631] [INSPIRE].

    ADS  Article  Google Scholar 

  24. [24]

    NNPDF collaboration, Parton distributions from high-precision collider data, Eur. Phys. J. C 77 (2017) 663 [arXiv:1706.00428] [INSPIRE].

  25. [25]

    T. Binoth, J. Guillet, E. Pilon and M. Werlen, Beyond leading order effects in photon pair production at the Tevatron, Phys. Rev. D 63 (2001) 114016 [hep-ph/0012191] [INSPIRE].

  26. [26]

    CDF collaboration, Measurement of the cross section for prompt isolated diphoton production using the full CDF Run II data sample, Phys. Rev. Lett. 110 (2013) 101801 [arXiv:1212.4204] [INSPIRE].

  27. [27]

    D0 collaboration, Measurement of the differential cross sections for isolated direct photon pair production in \( p\overline{p} \) collisions at \( \sqrt{s} \) = 1.96 TeV, Phys. Lett. B 725 (2013) 6 [arXiv:1301.4536] [INSPIRE].

  28. [28]

    CMS collaboration, Measurement of differential cross sections for the production of a pair of isolated photons in pp collisions at \( \sqrt{s} \) = 7 TeV, Eur. Phys. J. C 74 (2014) 3129 [arXiv:1405.7225] [INSPIRE].

  29. [29]

    ATLAS collaboration, Measurement of isolated-photon pair production in pp collisions at \( \sqrt{s} \) = 7 TeV with the ATLAS detector, JHEP 01 (2013) 086 [arXiv:1211.1913] [INSPIRE].

  30. [30]

    J.M. Campbell, R.K. Ellis and C. Williams, Direct photon production at next-to-next-to-leading order, Phys. Rev. Lett. 118 (2017) 222001 [Erratum ibid. 124 (2020) 259901] [arXiv:1612.04333] [INSPIRE].

  31. [31]

    X. Chen, T. Gehrmann, N. Glover, M. Höfer and A. Huss, Isolated photon and photon+jet production at NNLO QCD accuracy, JHEP 04 (2020) 166 [arXiv:1904.01044] [INSPIRE].

    ADS  Google Scholar 

  32. [32]

    J.M. Campbell, J. Rojo, E. Slade and C. Williams, Direct photon production and PDF fits reloaded, Eur. Phys. J. C 78 (2018) 470 [arXiv:1802.03021] [INSPIRE].

    ADS  Article  Google Scholar 

  33. [33]

    J.M. Campbell and C. Williams, Triphoton production at hadron colliders, Phys. Rev. D 89 (2014) 113001 [arXiv:1403.2641] [INSPIRE].

    ADS  Article  Google Scholar 

  34. [34]

    R. Abdul Khalek et al., Phenomenology of NNLO jet production at the LHC and its impact on parton distributions, Eur. Phys. J. C 80 (2020) 797 [arXiv:2005.11327] [INSPIRE].

    ADS  Article  Google Scholar 

  35. [35]

    S. Badger, A. Guffanti and V. Yundin, Next-to-leading order QCD corrections to di-photon production in association with up to three jets at the Large Hadron Collider, JHEP 03 (2014) 122 [arXiv:1312.5927] [INSPIRE].

    ADS  Article  Google Scholar 

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Correspondence to James Whitehead.

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ArXiv ePrint: 2009.11310

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Gehrmann, T., Glover, N., Huss, A. et al. Scale and isolation sensitivity of diphoton distributions at the LHC. J. High Energ. Phys. 2021, 108 (2021).

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  • NLO Computations
  • QCD Phenomenology