MadGraph/MadEvent

MadGraph/MadEvent

5Cargese Summer School July 2010Tim StelzerActivities Lecture 1 SM + Partonic Cross Sections + Collaboration? 1) Generate partonic diagrams gg > tt~, gg > tt~h 2) Create account, repeat exercise 2) Generate subprocesses?

Lecture 2 (Hadronic Collisions) MC integration. Full explanation 1) Generate pp > tt~ > bb~mu+e- ve~ vm, pp > h > tt~bb~, background pp>tt~bb~, mbb>100, gg>h and backgrounds 3) Download onto local computers and perform analysis 4) Generate events, determine cuts

Lecture 3 (Radiation/Hadronization) 1) Create a new model1PT Distributions

Cargese Summer School July 2010Tim Stelzer48Mbb Distributions

Cargese Summer School July 2010Tim Stelzer49

Cargese Summer School July 2010Tim Stelzer50 ears/bushel x 183 bushels/acre 200-400 kernals/cob = 2.7 M /acre Or 1 kernal in 500 Acres

6

The Challenge

1 / 1,000,000,00014Cargese Summer School July 2010Tim StelzerTop quark 1/billion 1/100 billion. Speed 10^9 / second. 8m x 16m x 0.5m = 500 billion grains of sand.50 ears/bushel x 183 bushels/acre 200 kernals/cob = 200,000/acre Or 1 kernal in 5000 Acres 5Discoveries at hadron colliders(adapted from MLM)

Peak (easy)

Shape (medium)

Rate (hard)

22Cargese Summer School July 2010Tim StelzerAdd images MonaLisa, Seurat, Le Bateauby Matisse caused a minor stir when theMuseum of Modern Art, which housed it, hung the print upside-down for 46 days in1961until Genevieve Habert, a stockbroker, noticed the mistake and notified a guard. Habert later informed theNew York Timeswho in turn notified Monroe Wheeler, the Museum's art director. As a result, the artwork was rehung properly.[1] 7SuperSymmetry at LHC

23Cargese Summer School July 2010Tim Stelzer8New MC shows much harder!

24Cargese Summer School July 2010Tim Stelzer9Discovery Path @ LHCRediscover Standard Model

Identify excess

Identify nature of excess

Repeat

26Cargese Summer School July 2010Tim Stelzer10

Standard Model

udd

MatterLeptons Quarks

Force Carrierse-ndudu30

Cargese Summer School July 2010Tim StelzerMost successful Theory in Science 30 orders of magnitudephoton mass < 10-18 eV , TevatOscar W. Greenberg colorron > 1012 eV

Anti-matter Relativity

Details

32Cargese Summer School July 2010Tim StelzerPerturbation Theory

34Cargese Summer School July 2010Tim StelzerExample: e+e- m+m-Scattering cross section

Feynman Diagrams

37Cargese Summer School July 2010Tim Stelzer14gQEDZQEDW+-QEDgQCDhQED(m)Feynman Rules!

Partial list from SM

38Cargese Summer School July 2010Tim Stelzer15Add picture of FeynmanThese are basic building blocks, combine to form allowed diagramse.g. u u~ -> t t~

Draw Feynman diagrams:gg -> tt~ (gg -> bb~ e+ ve j j )gg -> tt~h Determine order for each diagramFeynman Rules!Order is QCD222

45Cargese Summer School July 2010Tim Stelzer16Add picture of FeynmanDraw Feynman diagrams + determine order (QED, QCD):gg -> tt~

gg -> tt~h

gg -> tt~bb~ (QCD only)Feynman Rules!Partial list from SM

Cargese Summer School July 2010Tim Stelzer17Add picture of Feynman

50Cargese Summer School July 2010Tim StelzerRegister

60http://madgraph.hep.uiuc.edu/Cargese Summer School July 2010Tim StelzerMadGraphUser Requests: gg -> tt~bb~QCD Order = 4QED Order =0

MadGraph Returns:Feynman diagrams Self-Contained Fortran Code for |M|^2

SUBROUTINE SMATRIX(P1,ANS)CC Generated by MadGraph II Version 3.83. Updated 06/13/05C RETURNS AMPLITUDE SQUARED SUMMED/AVG OVER COLORSC AND HELICITIESC FOR THE POINT IN PHASE SPACE P(0:3,NEXTERNAL)CC FOR PROCESS : g g -> t t~ b b~CC Crossing 1 is g g -> t t~ b b~ IMPLICIT NONECC CONSTANTSC Include "genps.inc" INTEGER NCOMB, NCROSS PARAMETER ( NCOMB= 64, NCROSS= 1) INTEGER THEL PARAMETER (THEL=NCOMB*NCROSS)CC ARGUMENTSC REAL*8 P1(0:3,NEXTERNAL),ANS(NCROSS)C

401:05Cargese Summer School July 2010Tim Stelzer20storyHadron Colliders

1:10Cargese Summer School July 2010Tim StelzerExerciseList processes for signal pp > h > tt~bb~e.g. uu~ > h > tt~ bb~

List processes for background pp > tt~bb~e.g. uu~ > tt~bb~

List processes for reducible background pp>ttjje.g. uu~ > tt~gg1:20Cargese Summer School July 2010Tim Stelzer22HomeworkPlay w/ MadGraph siteTry pp > h > tt~bb~Go to wiki pageWatch John Ellis on Daily showView event animation 1:30Cargese Summer School July 2010Tim Stelzer23End---Day 1

Cargese Summer School July 2010Tim StelzerCargese Summer School July 2010Tim Stelzer25Parton Distribution Functions (Measured)Evolution+SplittingHard ScatteringShowering FragmentationHadronizatione-e+ Cargese Summer School July 2010Tim Stelzer26Hadron Collider Master Formula

Probability of finding parton a having momentum fraction x in proton 1.

Leading order Next-to-leading order Next-to-next-to-leading orderLong distance (measured + th)Short distance (expansion)Cargese Summer School July 2010Tim StelzerLO: Technical Challenges (3 jets @ LHC)Identify all subprocesses (gg->ggg, qg->qgg)

For each one, calculate amplitude:

Square amplitude, sum over spins & color, integrate over phase

Cargese Summer School July 2010Tim StelzerExercisestt~ production pp>tt~> bb~m+e- ve~ vmtt~+Higgs: pp>h>tt~bb~ (QCD=2,QED=2)tt~h background: pp>tt~bb~ QCD=99, QED=0tH: pp>tHj (QCD=0, QED=3)Try using proc_card method.

Cargese Summer School July 2010Tim StelzerMadGraphUser Requests: gg -> tt~bb~QCD Order = 4QED Order =0

MadGraph Returns:Feynman diagrams Self-Contained Fortran Code for |M|^2

SUBROUTINE SMATRIX(P1,ANS)CC Generated by MadGraph II Version 3.83. Updated 06/13/05C RETURNS AMPLITUDE SQUARED SUMMED/AVG OVER COLORSC AND HELICITIESC FOR THE POINT IN PHASE SPACE P(0:3,NEXTERNAL)CC FOR PROCESS : g g -> t t~ b b~CC Crossing 1 is g g -> t t~ b b~ IMPLICIT NONECC CONSTANTSC Include "genps.inc" INTEGER NCOMB, NCROSS PARAMETER ( NCOMB= 64, NCROSS= 1) INTEGER THEL PARAMETER (THEL=NCOMB*NCROSS)CC ARGUMENTSC REAL*8 P1(0:3,NEXTERNAL),ANS(NCROSS)C

408Cargese Summer School July 2010Tim Stelzer30storyWeb Process SpecificationInitial stateu u~> b b~ t t~Final state / AZcExcluded particles> hRequired particles> b b~ t (t~ >W- b~)Decay Chain

10Cargese Summer School July 2010Tim Stelzer31http://madgraph.hep.uiuc.edu/Examine the following processesuu~ > tt~bb~ QED=99, QCD=99uu~ > tt~bb~ QED=2, QCD=2uu~ > tt~ bb~ /AZ QED=2, QCD=2uu~ > h > tt~bb~ QED=2, QCD=99uu~ > tt~ (h > bb~) QED=2, QCD=99

What would you use to generatePure QCD background (dominant)Full background SM w/o HiggsWhat would you use for Signal?U: AngelsP: _ _ _ _ _ _20DCargese Summer School July 2010Tim Stelzer32Integrating to get cross sections(and events too)!

Large number of dimensions (3N-4)+2

Sharply peaked

Cargese Summer School July 2010Tim Stelzer33Integrals as averages

Only works for f(x) = 150Cuts OKIndependent of NEvent GenerationOnly OptionCargese Summer School July 2010Tim StelzerIndependent of # dimensionsDoesnt require smooth34Importance Sampling

52Cargese Summer School July 2010Tim Stelzer35Importance Sampling (a la VEGAS)

53Cargese Summer School July 2010Tim Stelzer36Too Good To Be True?

Works in multiple dimensionsP(x,y,z) = p(x)*p(y)*p(z)But, peaks must be aligned w/ axis of integration variables!54Cargese Summer School July 2010Tim Stelzer37Multi-channelCant map these peaks

Solution Multi-channel, each channel solves one peak

Cargese Summer School July 2010Tim Stelzer38Multi-channel

=+

55Cargese Summer School July 2010Tim Stelzer39Single Diagram EnhancedKey IdeaAny individual diagram is easy to integrateDivide based on diagramsN Independent IntegralsErrors add in QuadratureParallel in NatureWhat about Interference terms?

Cargese Summer School July 2010Tim Stelzer40

pp > tt~ (h > bb~)2210Lets Play!

Cargese Summer School July 2010Tim StelzerBreak

Cargese Summer School July 2010Tim Stelzer42ExerciseLook at run results for signal pp > tt~ (h>bb~)Which channels contributeWhich diagrams contribute3 sanity checks

Look at plots Compare w/ plots for QCD background (ttbb) PSDSDEPCPtM55Cargese Summer School July 2010Tim Stelzer43Check 1 (process symmetry)

Cargese Summer School July 2010Tim Stelzer44Check 2 (Diagram Symmetry)

Cargese Summer School July 2010Tim Stelzer45Check 3 (Enhancements)

Cargese Summer School July 2010Tim Stelzer46Check 4 (process contributions)

1607Cargese Summer School July 2010Tim Stelzer47