A
bstract
We present the application of a novel reduction technique for one-loop scattering amplitudes based on the combination of the integrand reduction and Laurent expansion. We describe the ...general features of its implementation in the computer code N
inja
, and its interface to G
o
S
am
. We apply the new reduction to a series of selected processes involving massive particles, from six to eight legs.
A
bstract
We complete the analytic evaluation of the master integrals for the two-loop non-planar box diagrams contributing to the top-pair production in the quark-initiated channel, at ...next-to-next-to-leading order in QCD. The integrals are determined from their differential equations, which are cast into a canonical form using the Magnus exponential. The analytic expressions of the Laurent series coefficients of the integrals are expressed as combinations of generalized polylogarithms, which we validate with several numerical checks. We discuss the analytic continuation of the planar and the non-planar master integrals, which contribute to
q q
→
tt
in QCD, as well as to the companion QED scattering processes
ee
→ μμ and
e
μ →
e
μ.
Unitarity-Cuts and Berry’s Phase Mastrolia, Pierpaolo
Letters in mathematical physics,
02/2010, Letnik:
91, Številka:
2
Journal Article
Recenzirano
Elaborating on the observation that two-particle unitarity-cuts of scattering amplitudes can be computed by applying Stokes’ theorem, we relate the optical theorem to the Berry phase, showing how the ...imaginary part of arbitrary one-loop Feynman amplitudes can be interpreted as the flux of a complex 2-form.
We present an interface between the multipurpose Monte Carlo tool MadGraph5_aMC@NLO and the automated amplitude generator GoSam. As a first application of this novel framework, we compute the NLO ...corrections to Formula omitted Formula omitted and Formula omitted Formula omitted matched to a parton shower. In the phenomenological analyses of these processes, we focus our attention on observables which are sensitive to the polarisation of the top quarks.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Here, we present an interface between the multipurpose Monte Carlo tool MadGraph5_aMC@NLO and the automated amplitude generator GoSam. As a first application of this novel framework, we compute the ...NLO corrections to pp→ tt¯H and pp→ tt¯γγ matched to a parton shower. In the phenomenological analyses of these processes, we focus our attention on observables which are sensitive to the polarisation of the top quarks.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
We present an interface between the multipurpose Monte Carlo tool
MadGraph5_aMC@NLO
and the automated amplitude generator
GoSam
. As a first application of this novel framework, we compute the NLO ...corrections to
p
p
→
t
t
¯
H
and
p
p
→
t
t
¯
γ
γ
matched to a parton shower. In the phenomenological analyses of these processes, we focus our attention on observables which are sensitive to the polarisation of the top quarks.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
We present the master integrals needed for the calculation of the two-loop QCD corrections to the forward–backward asymmetry of a quark–antiquark pair produced in electron–positron annihilation ...events. The Abelian diagrams entering in the evaluation of the vector form factors were calculated in a previous paper. We consider here the non-Abelian diagrams and the diagrams entering in the computation of the axial form factors, for arbitrary space-like momentum transfer
Q
2 and finite heavy quark mass
m. Both the UV and IR divergences are regularized in the continuous
D-dimensional scheme. The master integrals are Laurent-expanded around
D=4 and evaluated by the differential equation method; the coefficients of the expansions are expressed as 1-dimensional harmonic polylogarithms of maximum weight 4.
After a general introduction about the calculation of one-loop scattering amplitudes via integrand-level techniques, which led to the construction of efficient and automated computational tools for ...NLO predictions, we briefly describe an approach to the reduction of scattering amplitudes based on integrand-level reduction via multivariate polynomial division also applicable beyond one-loop amplitudes. We also review the main features of the GoSam 2.0 automated framework for NLO calculations and show some of its application to Standard Model processes involving the production massive particles, such as the Higgs boson or top-quark pairs, obtained embedding of the virtual amplitudes produced by GoSam within existing Monte Carlo tools.
We complete the analytic evaluation of the master integrals for the two-loop non-planar box diagrams contributing to the top-pair production in the quark-initiated channel, at next-to-next-to-leading ...order in QCD. The integrals are determined from their differential equations, which are cast into a canonical form using the Magnus exponential. The analytic expressions of the Laurent series coefficients of the integrals are expressed as combinations of generalized polylogarithms, which we validate with several numerical checks. We discuss the analytic continuation of the planar and the non-planar master integrals, which contribute to q q → tt in QCD, as well as to the companion QED scattering processes ee → μμ and eμ → eμ.
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