20180921 11:17 
[PUBDB201803555]
Preprint/Report
Ablinger, J. ; Blümlein, J. ; Round, M. ; et al
Numerical Implementation of Harmonic Polylogarithms to Weight w = 8
[DESY13064; DOTH1712; arXiv:1809.07084]
We present the FORTRANcode HPOLY.f for the numerical calculation of harmonic polylogarithms up to w = 8 at an absolute accuracy of $\sim 4.9 \cdot 10^{15}$ or better. Using algebraic and argument relations the numerical representation can be limited to the range $x \in [0, \sqrt{2}1]$. [...]
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20180920 10:28 
[PUBDB201803546]
Journal Article/Report
Alekhin, S. ; Bluemlein, J. ; Moch, S. .
NNLO PDFs for the LHC
[DESY18150; DOTH1819; arXiv:1808.08404]
We consider some trends, achievements and a series of remaining problems in the precision determination of parton distribution functions. For the description of the scaling violations of the deepinelastic scattering data, forming the key ingredients to all PDF fits, a solid theoretical framework is of importance [...]
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ddc:530
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20180918 10:46 
[PUBDB201803526]
Preprint/Report
Blümlein, J. ; Schneider, C.
Computer algebra tools for Feynman integrals and related multisums
[DESY18160; DOTH1821; arXiv:1809.06168]
In perturbative calculations, e.g., in the setting of Quantum Chromodynamics (QCD) one aims at the evaluation of Feynman integrals. Here one is often faced with the problem to simplify multiple nested integrals or sums to expressions in terms of indefinite nested integrals or sums. [...]
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20180905 11:44 
[PUBDB201803385]
Preprint/Report
Blümlein, J. ; Freitas, A. d. ; Van Hoeij, M. ; et al
The $\rho$ parameter at three loops and elliptic integrals
[DESY18117; DOTH1815; arXiv:1807.05287]
We describe the analytic calculation of the master integrals required to compute the twomass threeloop corrections to the $\rho$ parameter. In particular, we present the calculation of the master integrals for which the corresponding differential equations do not factorize to first order. [...]
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20180905 09:55 
[PUBDB201803372]
Preprint/Report
Alekhin, S. ; Bluemlein, J. ; Moch, S. O.
NNLO PDFs for the LHC
[DESY18150; DOTH1819; arXiv:1808.08404]
We consider some trends, achievements and a series of remaining problems in the precision determination of parton distribution functions. For the description of the scaling violations of the deepinelastic scattering data, forming the key ingredients to all PDF fits, a solid theoretical framework is of importance [...]
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20180905 09:47 
[PUBDB201803370]
Preprint/Report
Ablinger, J. ; Blümlein, J. ; Marquard, P. ; et al
Massive three loop form factors in the planar limit
[DESY18118; DOTH1814; arXiv:1807.05943]
We present the color planar and complete light quark QCD contributions to the three loop heavy quark form factors in the case of vector, axialvector, scalar and pseudoscalar currents. We evaluate the master integrals applying a new method based on differential equations for general bases, which is applicable for any first order factorizing systems. [...]
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20180827 14:18 
[PUBDB201803195]
Preprint/Report
Blümlein, J.
Iterative Noniterative Integrals in Quantum Field Theory
[DESY18143; DOTH1708; arXiv:1808.08128]
Single scale Feynman integrals in quantum field theories obey difference or differential equations with respect to their discrete parameter $N$ or continuous parameter $x$. The analysis of these equations reveals to which order they factorize, which can be different in both cases. [...]
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20180827 13:24 
[PUBDB201803190]
Preprint/Report
Alekhin, S. ; Bluemlein, J. ; Kulagin, S. ; et al
Strange and nonstrange distributions from the collider data
[DESY18144; DOTH1818; arXiv:1808.06871]
We check the stability of the ABMP16 fit with respect to modifications of quark PDFs suggested in the recent literature: the strange sea enhancement and a positive nonvanishing $d/u$ ratio at $x \to 1$. These possibilities are examined using test versions of the ABMP16 PDF fit which demonstrate no need of those changes. [...]
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20180807 09:49 
[PUBDB201802763]
Preprint/Report
Ablinger, J. ; Blümlein, J. ; Freitas, A. d. ; et al
Twomass threeloop effects in deepinelastic scattering
[DESY18119; DOTH1816; arXiv:1807.07855]
We report on recent results on the twomass corrections for massive operator matrix elements at 2 and 3loop orders in QCD. These corrections form the building blocks of the variable flavor number scheme. [...]
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20180801 14:57 
[PUBDB201802739]
Report/Journal Article
Alekhin, S. ; Blümlein, J. ; Moch, S.O.
NLO PDFs from the ABMP16 fi
[DESY18026; DOTH1728; arXiv:1803.07537]
We perform a global fit of parton distribution functions (PDFs) together with the strong coupling constant $\alpha_s$ and the quark masses $m_c, m_b$ and $m_t$ at nexttoleading order (NLO) in QCD. The analysis applies the $\overline{MS}$ renormalization scheme for αs and all quark masses. [...]
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ddc:530
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