16 research outputs found
On the Light Massive Flavor Dependence of the Large Order Asymptotic Behavior and the Ambiguity of the Pole Mass
We provide a systematic renormalization group formalism for the mass effects
in the relation of the pole mass and short-distance masses
such as the mass of a heavy quark ,
coming from virtual loop insertions of massive quarks lighter than . The
formalism reflects the constraints from heavy quark symmetry and entails a
combined matching and evolution procedure that allows to disentangle and
successively integrate out the corrections coming from the lighter massive
quarks and the momentum regions between them and to precisely control the large
order asymptotic behavior. With the formalism we systematically sum logarithms
of ratios of the lighter quark masses and , relate the QCD corrections for
different external heavy quarks to each other, predict the virtual quark mass corrections in the pole-
mass relation, calculate the pole mass differences for the top, bottom and
charm quarks with a precision of around MeV and analyze the decoupling of
the lighter massive quark flavors at large orders. The summation of logarithms
is most relevant for the top quark pole mass , where the
hierarchy to the bottom and charm quarks is large. We determine the ambiguity
of the pole mass for top, bottom and charm quarks in different scenarios with
massive or massless bottom and charm quarks in a way consistent with heavy
quark symmetry, and we find that it is MeV. The ambiguity is larger than
current projections for the precision of top quark mass measurements in the
high-luminosity phase of the LHC.Comment: 45 pages + appendix, 6 figures, v2: journal versio
The MSR Mass and the Renormalon Sum Rule
We provide a detailed description and analysis of a low-scale short-distance
mass scheme, called the MSR mass, that is useful for high-precision top quark
mass determinations, but can be applied for any heavy quark . In contrast to
earlier low-scale short-distance mass schemes, the MSR scheme has a direct
connection to the well known mass commonly used for
high-energy applications, and is determined by heavy quark on-shell self-energy
Feynman diagrams. Indeed, the MSR mass scheme can be viewed as the simplest
extension of the mass concept to renormalization scales
. The MSR mass depends on a scale that can be chosen freely, and
its renormalization group evolution has a linear dependence on , which is
known as R-evolution. Using R-evolution for the MSR mass we provide details of
the derivation of an analytic expression for the normalization of the renormalon asymptotic behavior of the pole mass in
perturbation theory. This is referred to as the
renormalon sum rule, and can be applied to any perturbative series. The
relations of the MSR mass scheme to other low-scale short-distance masses are
analyzed as well.Comment: 42 pages + appendices, 6 figures, v2: Refs and Appendix B added,
Fig.3 changed from nl=4 to nl=5, v3: journal versio
Monte Carlo Top Quark Mass Calibration
The most precise top quark mass measurements use kinematic reconstruction
methods, determining the top mass parameter of a Monte Carlo event generator,
. Due to the complicated interplay of hadronization and parton
shower dynamics in Monte Carlo event generators relevant for kinematic
reconstruction, relating to field theory masses is a non-trivial
task. In this talk we report on a calibration procedure to determine this
relation using hadron level QCD predictions for 2-Jettiness in
annihilation, an observable which has kinematic top mass sensitivity and a
close relation to the invariant mass of the particles coming from the top
decay. The theoretical ingredients of the QCD prediction are reviewed. Fitting
2-Jettiness calculations at NLL/NNLL order to PYTHIA 8.205, we find
that agrees with the MSR mass
within uncertainties. At NNLL we find . can differ from the pole
mass by up to , and using the pole mass
generally leads to larger uncertainties. At NNLL we find as the fit result. In contrast,
converting obtained at NNLL to the pole mass
gives a result for that is substantially larger and
incompatible with the fit result. We also explain some theoretical aspects
relevant for employing the C-parameter as an alternative calibration
observable.Comment: Talk presented at the 13th International Symposium on Radiative
Corrections (RADCOR 2017), St. Gilgen, Austria, 24-29 September 2017. 7
pages, 1 figur
Top Quark Mass Calibration for Monte Carlo Event Generators
United States. Department of Energy (DE-SC0011090
On the Light Massive Flavor Dependence of the Top Quark Mass
We provide a systematic renormalization group formalism for the mass effects in the relation of the pole mass and short-distance masses such as the MS mass of a heavy quark Q, coming from virtual loop insertions of massive quarks lighter than Q with the main focus on the top quark. The formalism reflects the constraints from heavy quark symmetry and entails a combined matching and evolution procedure that allows to disentangle and successively integrate out the corrections coming from the lighter massive quarks and the momentum regions between them and also to precisely control the large order asymptotic behavior. With the formalism we systematically sum logarithms of ratios of the lighter quark masses and heavy quark mass, predict the
O
α
s
4
virtual quark mass corrections in the pole-
MS
Ì…
mass relation and calculate the pole mass differences for the top, bottom and charm quarks with a precision of around 20 MeV
Calibration of the top quark mass for Monte-Carlo event generators
© Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND 4.0). The most precise top quark mass measurements use kinematic reconstruction methods, determining the top mass parameter of a Monte Carlo event generator, mtMC. Due to the complicated interplay of hadronization and parton shower dynamics in Monte Carlo event generators, relating mtMC to field theory masses is a non-trivial task. In this talk we present a calibration procedure to determine this relation using hadron level QCD predictions for 2-Jettiness in e+e- annihilation, an observable which has kinematic top mass sensitivity and has a close relation to the invariant mass of the particles coming from the top decay. The theoretical ingredients of the QCD prediction are explained. Fitting e+e- 2-Jettiness calculations at NLL/NNLL order to PYTHIA 8.205, we find that mtMC agrees with the MSR mass at the scale 1 GeV within uncertainties, mtMC ≃ mtMSR1GeV, but differs from the pole mass by 900/600 MeV
Top quark mass calibration for Monte-Carlo event generators
The most precise top quark mass measurements use kinematic reconstruction methods, determining the top mass parameter of a Monte Carlo event generator, mMCt. Due to the complicated interplay of hadronization and parton shower dynamics in Monte Carlo event generators, relating mMCt to field theory masses is a non-trivial task. In this talk we present a calibration procedure to determine this relation using hadron level QCD predictions for 2-Jettiness in e+e- annihilation, an observable which has kinematic top mass sensitivity and has a close relation to the invariant mass of the particles coming from the top decay. The theoretical ingredients of the QCD prediction are explained. Fitting e+e- 2-Jettiness calculations at NLL/NNLL order to PYTHIA 8.205, we find that mMCt agrees with the MSR mass at the scale 1 GeV within uncertainties, mMCt mMSRt;1GeV, but differs from the pole mass by 900/600MeV
Summing logarithms and factorization for massive quark initiated jets and the Pythia top quark mass
© Copyright owned by the author(s) under the terms of the Creative Commons. The most precise top quark mass measurements use kinematic reconstruction methods, determining the top mass parameter of a Monte Carlo event generator, mtMC. Due to the complicated interplay of hadronization and parton shower dynamics in Monte Carlo event generators, relating mtMC to field theory masses is a non-trivial task. In this talk we present a calibration procedure to determine this relation using hadron level QCD predictions for 2-Jettiness in e+e- annihilation, an observable which has kinematic top mass sensitivity and has a close relation to the invariant mass of the particles coming from the top decay. The theoretical ingredients of the QCD prediction are explained. Fitting e+e-2-Jettiness calculations at NLL/NNLL order to PYTHIA 8.205, we find that mtMC agrees with the MSR mass at the scale 1 GeV within uncertainties, mtMC≃ mtMCmt, IGeVMSR, but differs from the pole mass by 900/600MeV
Top Quark Mass Calibration for Monte Carlo Event Generators
The most precise top quark mass measurements use kinematic reconstruction methods, determining the top mass parameter of a Monte Carlo event generator, . Due to hadronization and parton shower dynamics, relating to a field theory mass is difficult. We present a calibration procedure to determine this relation using hadron level QCD predictions for observables with kinematic mass sensitivity. Fitting 2-Jettiness calculations at NLL/NNLL order to Pythia 8.205, differs from the pole mass by / MeV, and agrees with the MSR mass within uncertainties,