NNLO vs parton-showers - THEP Mainz

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Validation• We compare our fixed order prediction to• the LO parton shower event generator HERWIG• incorporates LO hard-scattering amplitudes with partonshower• includes leading logs to all orders and LO color resummation• MC@NLO (Frixione, Webber)• incorporates NLO matrix elements with the parton showerfrom HERWIG• resummed Higgs p Tdistribution (Bozzi, Catani, de Florian, Grazzini)• matches NNLO with NNLL• combines to the ‘highest posssible’ accuracy fixed order andresummation effects20
What can we learn?• It is not obvious from first principles that the efficiencies in theevent generators and the fixed-order prediction agree:• The physics approximations in fixed-order and parton-showersare different; therefore ...• ... a disagreement means that at least one of these approachesdoes not describe the physics process correctly in the signalphase-space (i.e. after the selection cuts)• On the other hand: A good agreement would give confidence inour tools.21
Page 2 and 3: MotivationGluon fusion has been a t
Page 4 and 5: Inclusive Higgs cross-section• Hi
Page 8 and 9: “Scary” cut efficiencies• Cut
Page 11 and 12: Sector decomposition for diff. cros
Page 13 and 14: H WW at NNLO(CA, Dissertori, Stoeck
Page 15 and 16: Jet Veto• jet-veto has no impact
Page 17 and 18: Maximum transverse momentum• agai
Page 19: Are these results reliable?• We c
Page 23 and 24: • ... and at NNLO:• both spectr
Page 25 and 26: Cut variables: NNLO vs MC@NLO• je
Page 27 and 28: The di-photon channel(stuied by Dis
Page 29 and 30: Two-loop gg h amplitude in the MSS

NNLO vs parton-showers - THEP Mainz

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