Abstract
We present predictions for heavy-quark production at the Large Hadron Collider making use of the overline{mathrm{MS}} and MSR renormalization schemes for the heavy-quark mass as alternatives to the widely used on-shell renormalization scheme. We compute single and double differential distributions including QCD corrections at next-to-leading order and investigate the renormalization and factorization scale dependence as well as the perturbative convergence in these mass renormalization schemes. The implementation is based on publicly available programs, MCFM and xFitter, extending their capabilities. Our results are applied to extract the top-quark mass using measurements of the total and differential toverline{t} production cross-sections and to investigate constraints on parton distribution functions, especially on the gluon distribution at low x values, from available LHC data on heavy-flavor hadro-production.
Highlights
We investigate the perturbative convergence in these schemes, by providing comparisons between physical quantities calculated at various levels of accuracy, and we discuss applications concerning the extraction of mass values and parton distribution functions (PDFs) from collider data
In the light of these observations, it will be worth to implement the transition to the other mass schemes directly in the MadGraph5_aMC@NLO program8 and in further Monte Carlo integrators/event generators, such that predictions for differential ttcross-sections in association with jets can be obtained in the format which is suitable for PDF fits in different mass schemes and with dynamical scales
In comparison to theory predictions in perturbative QCD, these data can be directly used for the extraction of heavy-quark masses, which are typically correlated with the value of the strong coupling constant αS(MZ)
Summary
In this work light quarks are assumed to be massless. For the heavy-quark masses, on the other hand, different renormalization schemes can be adopted and we briefly recall the relevant relations for the above mentioned cases of the MS, MSR and on-shell schemes. (2.3), (2.6) is renormalized in the MS scheme, the matrix elements, as well as the PDFs and the associated αS evolution used in the fixed-order massive calculations presented in this paper are all defined with a fixed number of light flavors nlf = 3 for charm and bottom production and nlf = 5 for top production, even at scales well above the heavy-quark mass value. In table 1 we compare the MS masses at the reference scale μref ≡ m(μref ), i.e. m(m), for charm-, bottom- and top-quarks with the pole masses mpole, obtained from the previous ones by retaining different numbers of terms in the conversion formula eq (2.3), and the MSR masses mMSR(R) at various numerical values of the R scale obtained by using eq (2.9) for the evolution. For bottom- or charmquarks on the other hand, the conversion of m(m) or mMSR(R) to the on-shell scheme demonstrates the poor convergence of the perturbative expansion already discussed above, cf. eq (2.6)
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