We determine a new set of parton distribution functions (ABMP16), the strong coupling constant αs and the quark masses mc, mb and mt in a global fit to next-to-next-to-leading order (NNLO) in QCD. ...The analysis uses the MS¯ scheme for αs and all quark masses and is performed in the fixed-flavor number scheme for nf=3, 4, 5. Essential new elements of the fit are the combined data from HERA for inclusive deep-inelastic scattering (DIS), data from the fixed-target experiments NOMAD and CHORUS for neutrino-induced DIS, data from Tevatron and the LHC for the Drell-Yan process and the hadro-production of single-top and top-quark pairs. The theory predictions include new improved approximations at NNLO for the production of heavy quarks in DIS and for the hadro-production of single-top quarks. The description of higher twist effects relevant beyond the leading twist collinear factorization approximation is refined. At NNLO, we obtain the value αs(nf=5)(MZ)=0.1147±0.0008.
NLO PDFs from the ABMP16 fit Alekhin, S.; Blümlein, J.; Moch, S.
The European physical journal. C, Particles and fields,
06/2018, Letnik:
78, Številka:
6
Journal Article
Recenzirano
Odprti dostop
We perform a global fit of parton distribution functions (PDFs) together with the strong coupling constant
α
s
and the quark masses
m
c
,
m
b
and
m
t
at next-to-leading order (NLO) in QCD. The ...analysis applies the
MS
¯
renormalization scheme for
α
s
and all quark masses. It is performed in the fixed-flavor number scheme for
n
f
=
3
,
4
,
5
and uses the same data as the previous ABMP16 fit at next-to-next-to-leading order (NNLO). The new NLO PDFs complement the set of ABMP16 PDFs and are to be used consistently with NLO QCD predictions for hard scattering processes. At NLO we obtain the value
α
s
(
n
f
=
5
)
(
M
Z
)
=
0.1191
±
0.0011
compared to
α
s
(
n
f
=
5
)
(
M
Z
)
=
0.1147
±
0.0008
at NNLO.
We compute the static contribution to the gravitational interaction potential of two point masses in the velocity-independent five-loop (and 5th post-Newtonian) approximation to the harmonic ...coordinates effective action in a direct calculation. The computation is performed using effective field methods based on Feynman diagrams in momentum-space in d=3−2ε space dimensions. We also reproduce the previous results including the 4th post-Newtonian order.
We calculate the potential contributions of the motion of binary mass systems in gravity to the fifth post–Newtonian order ab initio using coupling and velocity expansions within an effective field ...theory approach based on Feynman amplitudes starting with harmonic coordinates and using dimensional regularization. Furthermore, the singular and logarithmic tail contributions are calculated. We also consider the non–local tail contributions. Further steps towards the complete calculation are discussed. We calculate all but the rational O(ν2) contributions to the bound state energy for circular motion and periastron advance K(Eˆ,j). Comparisons are given to results in the literature.
We calculate the unpolarized and polarized three–loop anomalous dimensions and splitting functions PNS+,PNS− and PNSs in QCD in the MS‾ scheme by using the traditional method of space–like off shell ...massless operator matrix elements. This is a gauge–dependent framework. For the first time we also calculate the three–loop anomalous dimensions PNS±,tr for transversity directly. We compare our results to the literature.
We calculate the motion of binary mass systems in gravity up to the sixth post–Newtonian order to the GN3 terms ab initio using momentum expansions within an effective field theory approach based on ...Feynman amplitudes in harmonic coordinates. For these contributions we construct a canonical transformation to isotropic and to EOB coordinates at 5PN and agree with the results in the literature 1,2 by Bern et al. and Damour. At 6PN we compare to the Hamiltonians in isotropic coordinates either given in 1 or resulting from the scattering angle. We find a canonical transformation from our Hamiltonian in harmonic coordinates to 1, but not to 2. This implies that we also agree on all observables with 1 to the sixth post–Newtonian order to GN3.
The ABM parton distributions tuned to LHC data Alekhin, S.; Blümlein, J.; Moch, S.
Physical review. D, Particles, fields, gravitation, and cosmology,
03/2014, Letnik:
89, Številka:
5
Journal Article
We calculate the motion of binary mass systems in gravity up to the fourth post–Newtonian order. We use momentum expansions within an effective field theory approach based on Feynman amplitudes in ...harmonic coordinates by applying dimensional regularization. We construct the canonical transformations to ADM coordinates and to effective one body theory (EOB) to compare with other approaches. We show that intermediate poles in the dimensional regularization parameter ε vanish in the observables and the classical theory is not renormalized. The results are illustrated for a series of observables for which we agree with the literature.
Within an effective field theory method to general relativity, we calculate the fifth-order post–Newtonian (5PN) Hamiltonian dynamics also for the tail terms, extending earlier work on the potential ...contributions, working in harmonic coordinates. Here we calculate independently all (local) 5PN far-zone contributions using the in–in formalism, on which we give a detailed account. The five expansion terms of the Hamiltonian in the effective one body (EOB) approach, q82,q63,q44,d5¯ and an, can all be determined from the local contributions to the periastron advance Kloc,h(Eˆ,j), without further assumptions on the structure of the symmetric mass ratio, ν, of the expansion coefficients of the scattering angle χk. The O(ν2) contributions to the 5PN EOB parameters have been unknown in part before. We perform comparisons of our analytic results with the literature and also present numerical results on some observables.
A
bstract
We present a method to calculate the
x
-space expressions of massless or massive operator matrix elements in QCD and QED containing local composite operator insertions, depending on the ...discrete Mellin index
N
, directly, without computing the Mellin-space expressions in explicit form analytically. Here
N
belongs either to the even or odd positive integers. The method is based on the resummation of the operators into effective propagators and relies on an analytic continuation between two continuous variables. We apply it to iterated integrals as well as to the more general case of iterated non-iterative integrals, generalizing the former ones. The
x
-space expressions are needed to derive the small-
x
behaviour of the respective quantities, which usually cannot be accessed in
N
-space. We illustrate the method for different (iterated) alphabets, including non-iterative
2
F
1
and elliptic structures, as examples. These structures occur in different massless and massive three-loop calculations. Likewise the method applies even to the analytic closed form solutions of more general cases of differential equations which do not factorize into first-order factors.
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