1 / 11

110 likes | 244 Views

Carola Berger (SLAC) , Zvi Bern (UCLA), Lance Dixon (SLAC), Darren Forde (SLAC) , David Kosower (Saclay), Daniel Maitre (SLAC) , Yorgos Sofianatos (SLAC). Computation of Multi-Jet QCD Amplitudes at NLO. Overview. What’s the problem?.

Download Presentation
## Computation of Multi-Jet QCD Amplitudes at NLO

**An Image/Link below is provided (as is) to download presentation**
Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.
Content is provided to you AS IS for your information and personal use only.
Download presentation by click this link.
While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.
During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

**Carola Berger (SLAC), Zvi Bern (UCLA), Lance Dixon (SLAC),**Darren Forde (SLAC), David Kosower (Saclay), Daniel Maitre (SLAC), YorgosSofianatos (SLAC). Computation of Multi-Jet QCD Amplitudes at NLO**What’s the problem?**• Precise QCD amplitudes are needed to maximise the discovery potential of the LHC (2008). • NLO amplitudes 1-loop amplitudes.**“Famous” Les Houches experimentalist wish list, (2005)**What do we need? Six or more legs, until recently a bottleneck**What's the hold up?**• Calculating using Feynman diagrams is Hard! • Factorialgrowth in the number of Feynman diagrams. • Known results much simpler than would be expected!**A<n**R<n Rn The unitarity bootstrap • Use the most efficient approach for each piece, Unitarity cuts K3 On-shell recurrence relations A3 A2 A1 K1 K2 Recycle results of amplitudes with fewer legs “Glue” together trees to produce loops**Recursion relations**• On-shell recursion relations originally developed for massless tree amplitudes (Phys.Rev.Lett.94-Britto,Cachazo,Feng,Witten) • Very general, proof relies only on Factorization properties of amplitudes and Cauchy’s theorem. • Extended to massive particles, (JHEP 0507-Badger,Glover,Khoze,Svrcek) • All-plus and single-minus all-multiplicity amplitudes for a pair of massive scalars, An(φ,+,…,±,…,+, φ). (Phys.Rev.D73-Forde,Kosower) • Extended to one-loop amplitudes with no cut pieces. All-plus and single-minus helicity amplitudes, An(±,+,+,…,+), • Just gluons,(Phys.Rev.D71-Bern, Dixon, Kosower) • Both quarks and gluons with an arbitrary number of legs,(Phys.Rev.D71-Bern, Dixon, Kosower)**Including Unitarity Cuts**• Amplitudes with two or more negativity helicity legs contain cut terms. • Apply unitarity bootstrap; cut terms previously calculated (Nucl.Phys.B435&B425-Bern,Dixon,Dunbar,Kosower) • Adjacent 2-minus with 6 legs, (Phys.Rev.D73-Bern, Dixon, Kosower) • Minimal growth in “complexity” of solution with arbitrary numbers of legs, An(-,-,+,…,+),(Phys.Rev.D73 -Forde, Kosower)**Further Applications**• Non-adjacent 2-minus amplitude, An(-,+,…,-,…,+), (Phys.Rev.D75-Berger, Bern, Dixon, Forde, Kosower) • Three minus adjacent amplitude, An(-,-,-,+,…,+), (Phys.Rev.D74-Berger, Bern, Dixon, Forde, Kosower) • Important contributions to the recently derived complete six gluon amplitude.(Bern,Dixon,Kosower) (Berger,Bern,Dixon,Forde,Kosower) (Xiao,Yang,Zhu) (Bedford,Brandhuber,Spence,Travaglini) (Britto,Feng,Mastrolia) (Bern,Bjerrum-Bohr,Dunbar,Ita). • A Higgs boson plus arbitrary numbers of gluons or a pair of quarks for the all-plus and one-minus helicity combinations, An(φ,+,…,±,…,+). (Phys.Rev.D74-Berger, Del Duca, Dixon)**Increasing Efficiency**• Do better - use generalised unitarity for cut terms, • New techniques produce “compact” results in a direct manner. • Generally applicable, including “wish list” processes. Quadruple cuts, give box coefficients (Nucl.Phys.B725-Britto, Cachazo, Feng) Two-particle and triple cuts, give bubble and triangle coefficients (Phys.Rev.D-Forde)

More Related