English

Top-Quark Initiated Processes at High-Energy Hadron Colliders

High Energy Physics - Phenomenology 2015-06-11 v2

Abstract

In hadronic collisions at high energies, the top-quark may be treated as a parton inside a hadron. Top-quark initiated processes become increasingly important since the top-quark luminosity can reach a few percent of the bottom-quark luminosity. In the production of a heavy particle HH with mass mH>mtm_H > m_t, treating the top-quark as a parton allows us to resum large logarithms log(mH2/mt2\log(m_{H}^{2}/m_{t}^{2}) arising from collinear splitting in the initial state. We quantify the effect of collinear resummation at the 14-TeV LHC and a future 100-TeV hadron collider, focusing on the top-quark open-flavor process ggttˉHgg\to t\bar t H in comparison with ttˉHt\bar t \to H and tgtHtg\rightarrow tH at the leading order (LO) in QCD. We employ top-quark parton distribution functions with appropriate collinear subtraction and power counting. We find that (1) Collinear resummation enhances the inclusive production of a heavy particle with mHm_H\approx 5 TeV (0.5 TeV) by more than a factor of two compared to the open-flavor process at a 100-TeV (14-TeV) collider; (2) Top-quark mass effects are important for scales mHm_H near the top-quark threshold, where the cross section is largest. We advocate a modification of the ACOT factorization scheme, dubbed m-ACOT, to consistently treat heavy-quark masses in hadronic collisions; (3) The scale uncertainty of the total cross section in m-ACOT is of about 20 percent at the LO. While a higher-order calculation is indispensable for a precise prediction, the LO cross section is well described by the process ttˉHt\bar t\to H using an effective factorization scale significantly lower than mHm_H. We illustrate our results by the example of a heavy spin-0 particle. Our main results also apply to the production of particles with spin-1 and 2.

Keywords

Cite

@article{arxiv.1411.2588,
  title  = {Top-Quark Initiated Processes at High-Energy Hadron Colliders},
  author = {Tao Han and Joshua Sayre and Susanne Westhoff},
  journal= {arXiv preprint arXiv:1411.2588},
  year   = {2015}
}

Comments

30 pages, 9 figures, 1 table, matches version published in JHEP