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Direct numerical computation and its application to the higher-order radiative corrections

Direct numerical computation and its application to the higher-order radiative corrections. K Kato, E de Doncker, T Ishikawa and F Yuasa ACAT2017, 21-25 August 2017 University of Washington, Seattle. Introduction.

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Direct numerical computation and its application to the higher-order radiative corrections

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  1. Direct numerical computation and its application to the higher-order radiative corrections K Kato, E de Doncker, T Ishikawa and F Yuasa ACAT2017, 21-25 August 2017 University of Washington, Seattle

  2. Introduction • Precise theoretical prediction in HEP need of the large scale computation ( many particle final states, higher order radiative correction,…) sometimes beyond man-power solution: automated system for QFT • Library for multi-loop integrals is required for the general external momenta, various masses in EW/SUSY, to be used as a vital unit in an automated system for the perturbative computation

  3. Library for multi-loop integrals Analytical methods and Numerical methods QFT symbolic Expr. Data numerical DCM(Direct Computation Method), A ‘maximally’ numerical methodNumerical Integral + Series extrapolation

  4. multi-loop integrals and singularity singularity  regularization  numerical integration Target Case-2 : UV divergence Take n off 4, finite [M0] Case-1 : zero denominator keep finite [M2] Case-3 : IR divergence Take n off 4 or finite All cases are already handled by DCM

  5. DCM: Direct computation method DCM= regularized integration + series extrapolation Calculate the integral with finite ’s ….. For finite values, the integral is convergent numerically. Estimate the integral by extrapolation • Extrapolationby Wynn’s algorithm • Linear solver (LU decomposition)

  6. Numerical integration Numerical integration packages DQ … DQAGE/DQAGS routine in Quadpack package (http://www.netlib.org/quadpack/) ParInt package … Adaptive method (https://cs.wmich.edu/parint/) DE … Double exponential formula (http://www.sciencedirect.com/science/article/pii/S037704270000501X) Parallel computing in multi-core environment MPI(Message Passing Interface) … distributed memory OpenMP(Multi-Processing) … shared memory

  7. extrapolation  Integration  Wynn’s algorithm Input Linear solver Larger n is NOT always good, but an appropriate n exists.

  8. ACAT2016 DCM 4 3 2 Box Loops Vertex Self energy UV divergencein integral part massless (computed) dimension of integral 5 n 8 7 4 6 massive

  9. 3-loop vertex(scalar) massless E de Doncker and F Yuasa Procedia Computer Science 108C (2017) 1773–1782 Analytic results (a) T. Gehrmann, G. Heinrich, T. Huber, and C. Studerus (2006) (b,c) G. Heinrich, T. Huber, and D. Maˆıtre. (2008)

  10. Result (a) 4-dim. analytic Integral by ParInt on thor cluster (4 x 16 procs., MPI) in long double precision. Max 50B evaluation. 332s per iteration. Extrapolation by linear solver.

  11. Result (b,c) 6-dim. analytic analytic Integral by ParInt on thor cluster (4 x 16 procs., MPI) in long double precision. Evaluation (b) max 125B (c) max 80B

  12. ACAT2017 DCM 4 3 2 Box Loops Vertex Self energy UV divergencein integral part massless (computed) dimension of integral 5 4 7 6 n 6 8 massive

  13. GRACE .fin .mdl .rin modelfile Theory Diagram generator Process Userinput diagram description Drawer amplitude generator Make file etc. Diagrams(figure) Kinematics library LOOP TREE PS file symbolic code REDUCE, Form etc. FORTRAN code kinematics code generated code LibraryCHANEL, loop convergence information BASES(MC integral) parameter file Cross sections distributions SPRING (EG manager) Events

  14. GRACEH-H 2-loop 2point function in EW(w NLG, no tadpole) … 3082 diagrams(inc. C.T.) 2-loop diagrams H H 416 544 72(& reversed) 18 4-dim. L.F. 3-dim. L.F.(1 dim. Trivial) 3-dim. 2-dim. Product of 2 1-loop 52 55 128 103 2-dim. （L.F.)(1 dim. Trivial) others L.F. = some diagrams includes light fermions to make zero denominator to be processed by double regularization Counter terms 163

  15. GRACE 2-loop H tadpole in EW(w NLG) … 1934 diagrams(inc. C.T.) H Common to H-H 2-loop 52 18 202 Product of 2 1-loop (HH 1-loop) x (1-loop tadpole) Counter terms 55 531 158 918

  16. N is generated by GRACEas REDUCE code 2-loop amplitude Transformation After the loop integral FORTRAN code for G is made by REDUCE filter for each topology

  17. Variable transformation for each topology (J=Jacobian) Feynman parameter integral is calculated by DCM Polynomials of x’s universal

  18. performance Z t W t W Z H H Z H H H t t W 1 h/ Coef. (II) 20s / Coef. (I) 10s / Coef. (I) 0.6 s / Coef. (I) L.F. 246/416 L.F. 188/545 Heavy cases with light fermion(not yet) : double extrapolation  Parallel computing (I) Intel(R) Xeon(R) CPU E5-1660 0 @ 3.30GHz (II) Intel(R) Xeon(R) CPU E3-1280 v5 @ 3.70GHz Wynn’s algorithm (15 terms) DQ numerical integration Also show agreement with DE

  19. conclusion • DCM works well for the calculation of multi-loop integrals up to 8 dimensional parameter space. • Application to the 2-loop radiative corrections in full electro-weak theory seems to be possible within a practical computational time and resources.

  20. Thank you!

  21. 3-loop self-energyFiniteintegrals ,no extrapolation Comparison with Laporta(s=1, m=1) Absolute tolerance= 5 x 10−8, Max evaluations = 5B, T64 on thor cluster with p = 64 processes (distributed over four 16-core nodes)

  22. 3-loop self-energyUV-div. (up to 3rd order) E5-2687W v3 @ 3.10GHz Quadraple prec. 40 thread (5) Ladybug DCM (DE) C-1= 0.92370 ± 0.434 x 10−3 C0=−2.4201 ± 0.424 x 10−1 Laporta (s=1, m=1) Other diagrams are also computed. Comparison with analytical results is OK. 0.49493857234 0.53603234731 0.57465585827 0.6106239846 0.6438487350 0.6743208746 0.702092730 0.7272628131 0.749962533 0.7703450682 0.7885762731 0.804827478 0.819269932 0.832070673 0.843389581 0.85337740 0.8621745 0.869910 6-dim. Max eval =(102)6=1012 extrapolation (1,2) (1,2) (1,2) linear solver (1,0) (0,1) (0,1) Divergence order (Gamma, Integral) 0.92370 0.9236528

  23. 4-loop self-energymassless, finite and UV div. (1) -0.001736111111109 -0.016927083381 -0.011842916 Elapsed : 48s : ParInt, thor cluster 64 threads (2) 5.1846392 -2.582434 70.39877 Elapsed : 4.8h : DE, CPU KEKSC(SR-16000,64thread) Analytic results: P.A. Baikov and K.G.Chetrykin NPB 837 (2010) 186-220 (3) 55.585150 Elapsed : 554 seval.300B, ParInt, thor cluster 64 threads (4) 52.017714 Elapsed : 659 seval.275B, ParInt, thor cluster 64 threads

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