scholarly journals Two-loop helicity amplitudes for gg → ZZ with full top-quark mass effects

2021 ◽  
Vol 2021 (5) ◽  
Author(s):  
Bakul Agarwal ◽  
Stephen P. Jones ◽  
Andreas von Manteuffel
Keyword(s):  
Top Quark ◽  
Quark Mass ◽  
Parametric Representation ◽  
Top Quark Mass ◽  
Quark Loop ◽  
Linear Combinations ◽  
Feynman Integrals ◽  
Field Techniques ◽  
Helicity Amplitudes ◽  
Finite Integrals

Abstract We calculate the two-loop QCD corrections to gg → ZZ involving a closed top-quark loop. We present a new method to systematically construct linear combinations of Feynman integrals with a convergent parametric representation, where we also allow for irreducible numerators, higher powers of propagators, dimensionally shifted integrals, and subsector integrals. The amplitude is expressed in terms of such finite integrals by employing syzygies derived with linear algebra and finite field techniques. Evaluating the amplitude using numerical integration, we find agreement with previous expansions in asymptotic limits and provide ab initio results also for intermediate partonic energies and non-central scattering at higher energies.

scholarly journals ZH production in gluon fusion: two-loop amplitudes with full top quark mass dependence

2021 ◽  
Vol 2021 (3) ◽  
Author(s):  
Long Chen ◽  
Gudrun Heinrich ◽  
Stephen P. Jones ◽  
Matthias Kerner ◽  
Jonas Klappert ◽  
...  
Keyword(s):  
Top Quark ◽  
Quark Mass ◽  
Gluon Fusion ◽  
Top Quarks ◽  
Mass Dependence ◽  
Finite Part ◽  
Top Quark Mass ◽  
Helicity Amplitudes ◽  
Quark Mass Dependence ◽  
Loop Amplitudes

Abstract We present results for the two-loop helicity amplitudes entering the NLO QCD corrections to the production of a Higgs boson in association with a Z -boson in gluon fusion. The two-loop integrals, involving massive top quarks, are calculated numerically. Results for the interference of the finite part of the two-loop amplitudes with the Born amplitude are shown as a function of the two kinematic invariants on which the amplitudes depend.

scholarly journals Neutrino masses, vacuum stability and quantum gravity prediction for the mass of the top quark

2021 ◽  
Vol 2021 (1) ◽  
Author(s):  
Guillem Domènech ◽  
Mark Goodsell ◽  
Christof Wetterich
Keyword(s):  
Quantum Gravity ◽  
Top Quark ◽  
Quark Mass ◽  
Scalar Potential ◽  
Planck Scale ◽  
Neutrino Masses ◽  
Top Quark Mass ◽  
Vacuum Stability ◽  
Intermediate Scale ◽  
Yukawa Couplings

Abstract A general prediction from asymptotically safe quantum gravity is the approximate vanishing of all quartic scalar couplings at the UV fixed point beyond the Planck scale. A vanishing Higgs doublet quartic coupling near the Planck scale translates into a prediction for the ratio between the mass of the Higgs boson MH and the top quark Mt. If only the standard model particles contribute to the running of couplings below the Planck mass, the observed MH∼ 125 GeV results in the prediction for the top quark mass Mt∼ 171 GeV, in agreement with recent measurements. In this work, we study how the asymptotic safety prediction for the top quark mass is affected by possible physics at an intermediate scale. We investigate the effect of an SU(2) triplet scalar and right-handed neutrinos, needed to explain the tiny mass of left-handed neutrinos. For pure seesaw II, with no or very heavy right handed neutrinos, the top mass can increase to Mt ∼ 172.5 GeV for a triplet mass of M∆ ∼ 108GeV. Right handed neutrino masses at an intermediate scale increase the uncertainty of the predictions of Mt due to unknown Yukawa couplings of the right-handed neutrinos and a cubic interaction in the scalar potential. For an appropriate range of Yukawa couplings there is no longer an issue of vacuum stability.

scholarly journals Invariant-mass distribution of top-quark pairs and top-quark mass determination

2020 ◽  
Vol 44 (9) ◽  
pp. 091001
Author(s):  
Wan-Li Ju ◽  
Guoxing Wang ◽  
Xing Wang ◽  
Xiaofeng Xu ◽  
Yongqi Xu ◽  
...  
Keyword(s):  
Invariant Mass ◽  
Mass Distribution ◽  
Top Quark ◽  
Quark Mass ◽  
Invariant Mass Distribution ◽  
Mass Determination ◽  
Top Quark Mass ◽  
Quark Pairs ◽  
Top Quark Pairs

scholarly journals Optimising top-quark threshold scan at CLIC using genetic algorithm

2021 ◽  
Vol 2021 (7) ◽  
Author(s):  
K. Nowak ◽  
A.F. Żarnecki
Keyword(s):  
Genetic Algorithm ◽  
Pair Production ◽  
Top Quark ◽  
Quark Mass ◽  
Mass Measurement ◽  
Production Cross ◽  
Model Parameters ◽  
Top Quark Mass ◽  
Systematic Uncertainties ◽  
Pair Production Cross Section

Abstract One of the important goals at the future e+e− colliders is to measure the top-quark mass and width in a scan of the pair production threshold. However, the shape of the pair-production cross section at the threshold depends also on other model parameters, as the top Yukawa coupling, and the measurement is a subject to many systematic uncertainties. Presented in this work is the study of the top-quark mass determination from the threshold scan at CLIC. The most general approach is used with all relevant model parameters and selected systematic uncertainties included in the fit procedure. Expected constraints from other measurements are also taken into account. It is demonstrated that the top-quark mass can be extracted with precision of the order of 30 to 40 MeV, including considered systematic uncertainties, already for 100 fb−1 of data collected at the threshold. Additional improvement is possible, if the running scenario is optimised. With the optimisation procedure based on the genetic algorithm the statistical uncertainty of the mass measurement can be reduced by about 20%. Influence of the collider luminosity spectra on the expected precision of the measurement is also studied.

scholarly journals Top quark mass studies with t t ¯ j $$ t\overline{t}j $$ at the LHC

2018 ◽  
Vol 2018 (3) ◽  
Author(s):  
G. Bevilacqua ◽  
H. B. Hartanto ◽  
M. Kraus ◽  
M. Schulze ◽  
M. Worek
Keyword(s):  
Top Quark ◽  
Quark Mass ◽  
Top Quark Mass

scholarly journals Full top quark mass dependence in Higgs boson pair production at NLO

2016 ◽  
Vol 2016 (10) ◽  
Author(s):  
S. Borowka ◽  
N. Greiner ◽  
G. Heinrich ◽  
S.P. Jones ◽  
M. Kerner ◽  
...  
Keyword(s):  
Higgs Boson ◽  
Pair Production ◽  
Top Quark ◽  
Quark Mass ◽  
Mass Dependence ◽  
Top Quark Mass ◽  
Boson Pair ◽  
Boson Pair Production ◽  
Quark Mass Dependence
Sign in / Sign up

Export Citation Format

Share Document