Validity check of the KATIE parton level event generator in the kt-factorization and collinear frameworks

In the present paper, we check and study the validity of the KATIE parton level event generator by calculating the inclusive electron-proton (ep) dijet and the proton-proton (pp) Drell-Yan electron-pair production's differential cross sections in the k(t)- and collinear factorization frameworks. The MartinRyskin-Watt (MRW) unintegrated parton distribution functions (UPDFs) are used as the input UPDFs. The results are compared with those of ZEUS ep inclusive dijet and ATLAS p-p Drell-Yan electron-pair productions, experimental data. The KATIE parton level event generator can directly calculate the cross sections in the k(r)-factorization framework. It was noticed by van Hameren, the author of KATIE, that the lab to the Breit transformation in this generator was not correctly implemented, so the produced output did not cover the ep ZEUS experimental data in which the mentioned transformation is applied. The author of the code fixed the bug by implementing the correct transformation in the KATIE parton event generator. Then, we could appropriately produce the ep inclusive dijet differential cross section, in comparison with those of ZEUS data. It is also shown that the Martin-Ryskin-Watt at the next-to-leading order level, with the angular ordering constraint, can successfully predict the ATLAS p-p Drell-Yan data. Finally, as it is expected, we conclude that the k(t) factorization is an appropriate tool for the small longitudinal parton momenta and high center of mass energies, with respect to the collinear one.

Automated summary

In this paper, the validity of the KATIE parton level event generator is checked and studied by calculating inclusive electron-proton and proton-proton dijet and Drell-Yan electron-pair production's differential cross sections in k(t)- and collinear factorization frameworks. Results show that KATIE can calculate cross sections in the k(r)-factorization framework, and the implemented correct transformation fixes the mismatch with experimental data, demonstrating that k(t) factorization is suitable for small longitudinal parton momenta and high center of mass energies.