LoopFest 2013 Summary Talk

L. Dixon LoopFest 2013 Summary 1

Lance Dixon (SLAC)Florida State University Tallahassee

May 15, 2013

Apologies in advance

• For skipping your favorite topic• For mangling the main point of your

presentation• For a certain chronological bias…

L. Dixon LoopFest 2013 Summary 2

Voyages of Discovery

• 500 Years Ago (April 2, 1513): Ponce de Leon discovers Florida

L. Dixon LoopFest 2013 Summary 3

Voyages of Discovery

• 1 Year Ago (July 4, 2012): ATLAS + CMS discover a bump at 125.5 GeV

L. Dixon LoopFest 2013 Summary 4

Korytov

How fast things change

• Higgs mass: a new precision parameter of SM

L. Dixon LoopFest 2013 Summary 5

Korytov

Can we use a precisemH(gg) – mH(ZZ)to learn about Higgs width?

Li

Also great progress on signal strength m’s

• Denominator = sSM x BrSM needed lots of theory already, e.g. sNNLO; more needed for LHC Run II

L. Dixon LoopFest 2013 Summary 6

Korytov

sHtot: NNLO N3LO?

• Motivated by poor convergence of series

L. Dixon LoopFest 2013 Summary 7

sHtot: NNLO N3LO first steps

• Convolution of splitting kernels

• Best performed

in Mellin space

with aid of HPLs,

Hsums, maps:

L. Dixon LoopFest 2013 Summary 8

Hoff

sHtot: NNLO N3LO first steps

• Soft limit (z 1)• Use “reverse unitarity”[Anastasiou, Melnikov]

• IBPs

turn MB integrals

into generalized

polylogs z(n)

L. Dixon LoopFest 2013 Summary 9

Dulat

Need more exclusive results

• Especially for WW (jet veto against top)• But also to separate gg, VBF, …

L. Dixon LoopFest 2013 Summary 10

H + 1 jet @ NNLO

• A successful marriage [Czakon]

of FKS and sector decomposition

• gg only so far:• Looking forward to

full results before

complaining about

scale dependence

being too small…

L. Dixon LoopFest 2013 Summary 11

Caola

H + 0 jet @ NNLL’ + NNLO

• SCET-based resummation, uses a global ET veto as intermediate step

L. Dixon LoopFest 2013 Summary 12

Walsh

H + 0 jet @ NNLL + NNLO

L. Dixon LoopFest 2013 Summary 13

Monni

Fairly close to previous plot at 25-30 GeV?

H + 1 jet exclusive

• Resum first for pTjet >> pT

veto

• Match to fixed order for pTjet ~ pT

veto

L. Dixon LoopFest 2013 Summary 14

Liu

H + 2 jets with central veto (VBF)

• HEJ based on high-energy factorization.• Very different from other programs for these cuts

– need to resolve, maybe using V+jets data?

L. Dixon LoopFest 2013 Summary 15

Smillie

High Statistics V + jets Data• Tevatron & LHC, expecially recent D0 (W) & ATLAS (Z) • Agreement very good in “bulk” (but not large rapidity, v. small HT)

L. Dixon LoopFest 2013 Summary 16

Paramonov

• Try to use to understand H + jets dynamics better

Speculation: Could this be related to large x pdfs? OwensCharge separated W + jets at LHC would offer opportunity to separate d(x), u(x) at large x

On Higgs Day (Monday)

• Hardly a word about supersymmetry – except virtually…

L. Dixon LoopFest 2013 Summary 17

Zerf

ILC as a Higgs factory

• Higgs @ 1% of total cross section, not 10-10

• e+e- Zh tagged Higgsabsolute Br’s,

total width

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Peskin

NNLO for more hadron collider processes!

• For a long time, only color singlet final states available at full NNLO, mostly 2 1 at Born level: H, W, Z, gg

• 2013 will be remembered as the year of 2 2 at NNLO

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Top at NNLO• Great performance:• Upgraded energy from 2 TeV to 8 TeV in just one year:

• Already constraining pdfs and stealthy stops:

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Mitov

OK for Tevatron

Need for LHC

Wish for NNLO differential distributions for pdf constraints –Huston

Jets @ NNLO

• Adaptation of antenna subtraction method to pp• Another case (like H + 1 jet) of remarkably small

scale variation in a

gluon-only

approximation

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Pires

LoopFest 2013 Summary 22

I Know, It’s Only NLO(But I Like It)*

L. Dixon

*With apologies to the Rolling Stones (founded 50 years ago)

LoopFest 2013 Summary 23

The NLO multiplicity frontier:

L. Dixon

Febres Cordero

W + 5 jets

New request from J. Huston:Did we say NLO? We meant NNLO

The NLO flexibility frontier: aMC@NLO

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Mattelaer

The NLO flexibility frontier: GoSam

*FKS/dipole subtractions sold separately

• Examples of

pp H + 3 jets @ NLO

pp gg + jet @ NLO

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Greiner

The NLO flexibility frontier: OpenLoops

*dipole/FKS/shower sold separately [or get in aMC@NLO]• Marriage of recursion and OPP (or Collier) tensor reduction

• Example:

pp WW*(j) enmn (j) + ...

including MEPS@NLO [SHERPA]

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Cascioli

region

The NLO flexibility (final?) frontier: BSM with FeynRules

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Degrande

Are analytic calculations of one-loop amplitudes obsolete?

• Not necessarily. NNLO benefits from their excellent numerical stability

• Also, MCFM far from obsolete, all analytic:• tZ• ttW• Zgj, Zgg• H Z g with MEM@NLO• MCFM MCDM?L. Dixon LoopFest 2013 Summary 28

Rontsch Williams

Merging NLO with showers• MC@NLO, POWHEG great – but accuracy

degrades as you add jets within sample• In past year, several implementations of

NLO merging

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Hoeche

W + jets

tt + jets

Another route to NLO merging?

• Use MiNLO nodal scale + Sudakov prescription [Hamilton et al.] modified so B+0j recovered without spoiling NLO B+1j

L. Dixon LoopFest 2013 Summary 30

Re

SUSY Shower Merging

• qq @ NLO

• l l @ NLO

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GavinHangst

~~

~~ ThierInside the [POWHEG] box,or waiting for the shower?

ttH signal & bkgd in same box

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Kardos

Most complexprocess inPOWHEG-BOXframework

Difficult searchchannel!

New physics in top final states

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Boughezal, Schulze

Importance of independent PDFs mostly agreeing now at NNLO

• For Higgs,

top@LHC:

L. Dixon LoopFest 2013 Summary 34

Huston

Importance of independent PDFs mostly agreeing now at NNLO

• For Drell Yan, VV, slepton pairs, …

L. Dixon LoopFest 2013 Summary 35

Huston

Loops & B’s

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Ligeti

Multi-Loop Integrals

• Will need more complex 2-loop amplitudes as NNLO QCD real radiation techniques have recently matured.

• 2 3 integrals not known yet• Only a few 2 2 integrals known

analytically, rest numerically• EW frontier at fewer legs, but 3 loops and

multiple masses

L. Dixon LoopFest 2013 Summary 37

Freitas

Numerical Multi-loop Integral Tools

• SecDec2.1

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Borowka

Landau singularitiesdetected via run time!

• Method for deforming contoursto make numerical integration overloop momenta possible Becker

Analytic Multi-loop Integral Tools

• Simplify IBP relations to identify 2 2 2-loop master integrals

• Adjust master integral basis to simplify differential equations arising from IBPs pure transcendental functions

L. Dixon LoopFest 2013 Summary 39

Henn

Schabinger

Bahamas Billfish Championship

• Trophy: Billfish Championship Ring designed by Monica Higgs

• Winner = Proud Angler Higgs Bos’n?L. Dixon LoopFest 2013 Summary 40

Summary of summary• It’s been a very stimulating and rewarding 3 days – lots

of great talks representing advances in loop calculation and allied fields across many fronts.

• A great time to be doing precision work for use at LHC.• Most importantly, thanks to those who made this meeting

possible and run so smoothly!• FSU: College of Arts & Sciences, Office of Research,

and Physics Department• Seth Quackenbush• Kathy Mork• Laura Reina

L. Dixon LoopFest 2013 Summary 41