NNLO QCD corrections to three-photon production at the LHC

Abstract

We compute the NNLO QCD corrections to three-photon production at the LHC. This is the first NNLO QCD calculation for a 2 → 3 process. Our calculation is exact, except for the scale-independent part of the two-loop finite remainder which is included in the leading color approximation. We estimate the size of the missing two-loop corrections and find them to be phenomenologically negligible. We compare our predictions with available 8 TeV measurement from the ATLAS collaboration. We find that the inclusion of the NNLO corrections eliminates the existing significant discrepancy with respect to NLO QCD predictions, paving the way for precision phenomenology in this process.

Pentagon functions for scattering of five massless particles

“…In fact, the analytic JHEP12(2020)167 form of amplitudes can be directly reconstructed from their numerical evaluations over finite fields [8]. This approach has lead to remarkable progress in calculation of planar five-point amplitudes [17,[20][21][22][23][24][25][26][27][28][29]35]. We expect that our results will open a possibility of extending these methods to non-planar sector.…”

“…Evaluation of the planar subset of the pentagon functions 9 takes approximately 40% of the total evaluation time. Comparing to the evaluation times of the planar pentagon functions of [53] reported in [35], we observe that the planar subset of our implementation evaluates approximately 100 times faster.…”

“…Important progress has been made in evaluation of five-point amplitudes and integrals with one massive leg [32][33][34]. The first cross JHEP12(2020)167 section computation of a 2 → 3 process was carried out in [35], where the planar two-loop amplitudes for the qq → γγγ process were evaluated on a small set of phase space points to construct an interpolating function.…”

Analytic integration of soft and collinear radiation in factorised QCD cross sections at NNLO

“…The literature is too vast to be comprehensively cited, but the main characteristics and some important applications of the most developed methods can be found in refs. [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24]. It must also be mentioned that subtraction is not the only possible approach to the problem: an alternative viewpoint is provided by slicing methods, where an infrared cutoff is introduced to isolate the singular regions of the radiative phase space, and approximate expressions for the matrix elements are employed below the cutoff scale.…”

Analytic double-soft integrated subtraction terms for two massive emitters in a back-to-back kinematics

“…Currently, theoretical predictions with NNLO QCD accuracy exist for many LHC processes. They were obtained using slicing methods that include q T - [9][10][11][12] and Njettiness [13][14][15][16] slicing; as well as subtraction schemes such as antenna subtraction [17][18][19][20][21][22][23][24][25][26][27], JHEP07(2020)011 geometric subtraction [28], the STRIPPER framework [29][30][31][32][33], local analytic sector subtraction [34,35], the CoLoRFull method [36][37][38][39][40][41][42][43][44][45][46][47] and other approaches, e.g. the projectionto-Born method [48].…”