CT14QED parton distribution functions from isolated photon production in deep inelastic scattering

By C. Schmidt, J. Pumplin, D. Stump, C. Yuan. 2015

144 citations recorded by the source corpus.

We describe the implementation of quantum electrodynamic (QED) evolution at leading order (LO) along with quantum chromodynamic (QCD) evolution at next-to-leading order (NLO) in the CTEQ-TEA global analysis package. The inelastic contribution to the photon parton distribution function (PDF) is described by a two-parameter ansatz, coming from radiation off the valence quarks, and based on the CT14 NLO PDFs. Setting the two parameters to be equal allows us to completely specify the inelastic photon PDF in terms of the inelastic momentum fraction carried by the photon, ${p}_{0}^{\ensuremath{\gamma}}$, at the initial scale ${Q}_{0}=1.295\text{ }\text{ }\mathrm{GeV}$. We obtain constraints on the photon PDF by comparing with ZEUS data [S. Chekanov et al. (ZEUS Collaboration), Phys. Lett. B 687, 16 (2010)] on the production of isolated photons in deep inelastic scattering, $ep\ensuremath{\rightarrow}e\ensuremath{\gamma}+X$. For this comparison we present a new perturbative calculation of the process that consistently combines the photon-initiated contribution with the quark-initiated contribution. Comparison with the data allows us to put a constraint at the 90% confidence level of ${p}_{0}^{\ensuremath{\gamma}}\ensuremath{\lesssim}0.14%$ for the inelastic photon PDF at the initial scale of ${Q}_{0}=1.295\text{ }\text{ }\mathrm{GeV}$ in the one-parameter radiative ansatz. The resulting inelastic CT14QED PDFs will be made available to the public. In addition, we also provide CT14QEDinc PDFs, in which the inclusive photon PDF at the scale ${Q}_{0}$ is defined by the sum of the inelastic photon PDF and the elastic photon distribution obtained from the equivalent photon approximation.

Subfields: Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/52ed34fb0801a2c02ede53021a68f6cd36d85406

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In Nuclear and High Energy Physics

Citations in the corpus

Electroweak radiative corrections for collider physics (2019, methodology): “The photon PDF of the CT14qed PDF set [414], on the other hand, combined model assumptions and experimental input from ep → eγ + X data, achieving an accuracy at the level of 10−20%.”
Top-pair production at the LHC through NNLO QCD and NLO EW (2017, methodology): “We invite the 3The PDF sets MRST2004QED [47] and CT14QED [48] also include QED effects in the DGLAP evolution, but they are not NNLO QCD accurate.”
The Structure of the Proton in the LHC Precision Era (2017, background): “Thus, within such approaches the photon PDF is completely predicted within the specific model, up to any freedom in the model parameters, such as the choice of quark masses for MRST2004QED or the overall normalization for CT14QED.”
Lepton Number Violation: Seesaw Models and Their Collider Tests (2017, unknown): “1+LUXqed (lhaid=324900) [270], LUXqed17+PDF4LHC15 (lhaid=82200) [271, 272], and CT14 QED Inclusive (lhaid = 13300) [273].”
Illuminating the photon content of the proton within a global PDF analysis (2017, methodology): “s at the Born level are shown in Fig.4.1. Our aim is to assess the relative size of the PI contributions with respect to quark- and gluon-initiated subprocesses at the p s= 13 TeV LHC. See also Refs. [24,34,47{51] for recent studies. The results presented in this section have been obtained at leadin”
The photon content of the proton (2017, result): “Previous results on the photon PDF include MRST2004qed [17], NNPDF23 qed [18] and CT14qed inc [19] (all available within LHAPDF [20]) and the HKR16 set [21].”