scholarly journals Top-quark pair production at next-to-next-to-leading order QCD in electron positron collisions

2016 ◽  
Vol 2016 (12) ◽  
Author(s):  
Long Chen ◽  
Oliver Dekkers ◽  
Dennis Heisler ◽  
Werner Bernreuther ◽  
Zong-Guo Si
2015 ◽  
Vol 748 ◽  
pp. 74-78 ◽  
Author(s):  
Stefan Höche ◽  
Frank Krauss ◽  
Philipp Maierhöfer ◽  
Stefano Pozzorini ◽  
Marek Schönherr ◽  
...  

Author(s):  
S. Höche ◽  
P. Maierhöfer ◽  
N. Moretti ◽  
S. Pozzorini ◽  
F. Siegert

2021 ◽  
Vol 81 (4) ◽  
Author(s):  
A. M. Sirunyan ◽  
◽  
A. Tumasyan ◽  
W. Adam ◽  
F. Ambrogi ◽  
...  

AbstractThis paper presents new sets of parameters (“tunes”) for the underlying-event model of the $${\textsc {herwig}} \,7$$ H E R W I G 7 event generator. These parameters control the description of multiple-parton interactions (MPI) and colour reconnection in $${\textsc {herwig}} \,7$$ H E R W I G 7 , and are obtained from a fit to minimum-bias data collected by the CMS experiment at $$\sqrt{s}=0.9$$ s = 0.9 , 7, and $$13 \,\text {Te}\text {V} $$ 13 Te . The tunes are based on the NNPDF 3.1 next-to-next-to-leading-order parton distribution function (PDF) set for the parton shower, and either a leading-order or next-to-next-to-leading-order PDF set for the simulation of MPI and the beam remnants. Predictions utilizing the tunes are produced for event shape observables in electron-positron collisions, and for minimum-bias, inclusive jet, top quark pair, and Z and W boson events in proton-proton collisions, and are compared with data. Each of the new tunes describes the data at a reasonable level, and the tunes using a leading-order PDF for the simulation of MPI provide the best description of the data.


2020 ◽  
Vol 80 (9) ◽  
Author(s):  
Hao Yang ◽  
Zi-Qiang Chen ◽  
Cong-Feng Qiao

AbstractWe calculate the next-to-leading order (NLO) quantum chromodynamics (QCD) corrections to the exclusive processes $$\gamma +\gamma \rightarrow {\mathcal {Q}}+{\mathcal {Q}}$$ γ + γ → Q + Q , with $${\mathcal {Q}}=J/\psi ,\ \eta _c,\ \Upsilon $$ Q = J / ψ , η c , Υ , or $$\eta _b$$ η b , in the framework of non-relativistic QCD (NRQCD) factorization formalism. The cross sections at the SuperKEKB electron–positron collider, as well as at the future colliders, like the circular electron positron collider (CEPC) and the international linear collider (ILC), are evaluated. Numerical result indicates that the processes for $$J/\psi $$ J / ψ -pair production and $$\eta _c$$ η c -pair production are hopefully observable at the Belle II detector within the next decade.


2019 ◽  
Vol 99 (5) ◽  
Author(s):  
Helenka Casler ◽  
Matthew Manganel ◽  
Miguel C. N. Fiolhais ◽  
Andrea Ferroglia ◽  
António Onofre

2003 ◽  
Vol 18 (08) ◽  
pp. 1357-1364 ◽  
Author(s):  
W. BERNREUTHER ◽  
A. BRANDENBURG ◽  
Z. G. SI ◽  
P. UWER

Top quark-antiquark [Formula: see text] pairs will be produced copiously at the Tevatron collider and in huge numbers at the LHC. This will make possible detailed investigations of the properties and interactions of this quark flavor. The analysis and interpretation of future data requires precise predictions of the hadronic production of [Formula: see text] pairs and of their subsequent decays. In this talk the reactions [Formula: see text], [Formula: see text] are considered and results are presented of our calculation6 of the dilepton angular distribution at next-to-leading order QCD, keeping the full dependence on the spins of the intermediate [Formula: see text] state. The angular distribution is determined for different choices of reference axes that can be identified with the t and [Formula: see text] spin axes. While the QCD corrections to the leading-order distribution turn out to be small in the case of the LHC, we find them to be sizeable in the case of the Tevatron and find, moreover, the angular distribution to be sensitive to the parton content of the proton.


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