N3LO calculation of the B to Xs gamma photon spectrum including complete light-fermion corrections, two massive fermion loops, and large-Nc terms, with improved results in kinetic and MSR mass schemes.
Automated Solution of First Order Factorizable Systems of Differential Equations in One Variable
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abstract
We present an algorithm which allows to solve analytically linear systems of differential equations which factorize to first order. The solution is given in terms of iterated integrals over an alphabet where its structure is implied by the coefficient matrix of the differential equations. These systems appear in a large variety of higher order calculations in perturbative Quantum Field Theories. We apply this method to calculate the master integrals of the three--loop massive form factors for different currents, as an illustration, and present the results for the vector form factors in detail. Here the solution space emerging is given by the cyclotomic harmonic polylogarithms and their associated special constants. No special basis representation of the master integrals is needed. The algorithm can be applied as well to more general cases factorizing at first order, which are based on more general alphabets, iterated integrals and associated constants.
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UNVERDICTED 2representative citing papers
In the single-term splitting function model, complex maps turn DGLAP contour integrals into Laplace transforms whose inverse yields Barnes integrals for the Bessel solution.
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The photon-energy spectrum in $B\to X_s\gamma$ to N$^3$LO: light-fermion and large-$N_{\rm c}$ corrections
N3LO calculation of the B to Xs gamma photon spectrum including complete light-fermion corrections, two massive fermion loops, and large-Nc terms, with improved results in kinetic and MSR mass schemes.
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Analytical solution to DGLAP integro-differential equation via complex maps in domains of contour integrals
In the single-term splitting function model, complex maps turn DGLAP contour integrals into Laplace transforms whose inverse yields Barnes integrals for the Bessel solution.