ATLAS physics studies

Lian-You SHAN

On behalf of AtlasClusterChina

TeV 4 @ Tango

Aug 25, 2009

+ Introduction+ Published studies+ Studies on going+ Possible Studies later+ Summary

Lian-You SHAN TeV 3 @ Tango, Aug 25, 2009 2

+ A brief report of past works– For your review – Thanks to ACC colleagues for the contributions

+ An presentation of works ongoing– For your suggestions, corrections

+ A short list of future possible works– For your ideas, collaborations


+ Three works to ATL-COM-PHYS-2008/CERN-OPEN-2008-20

– ttH/WH production ( ACP-2008-199, IHEP )– W pola & top S-corr ( ACP-2008-073, SDU )– WZ x-sec ( ACP-2008-064, USTC )– Other works unfortunately late (single top, RPVemu)

+ CSC-BOOK : the official/biggest publication– At least till 2008 before real data

Many test-beam exps, mature reconstruction, analysis-SW– A balance among many factors

Physics impact, luminosity, experimental feasibility Experiences, International competition/collaboration


+ Physics motivation+ Event selection+ Preliminary results+ Systematics


21

t ))(

(YnlWWHHnl

nl

CBrMILN


Nnl(n=2,3): observed events in ttH-WW* n-lepton final states L: LHC integrated luminosity εnl: total efficiency of n-lepton final states I(MH): the integral over the parton momentum in initial states, propagator of gluon or quark in middle states and lepton/jet phase space in the final states Cnl: the combination factor of branching of W decays

Directly measures only: (ttH)*Br(HWW)=Nnl/(LnlCnl)

Ndata - Nbkg

Systematic errors

Yt


ttH2b4j2l2Vl6jets + 2samecharge lep. +

MissEt Possible BGs:

tt(1l), tt(2l), ttZ, ttW, tttt, ttWnq, ttbb...

ttH2b2j3l3Vl4jets + 3leptons + MissEt

Possible BGs:tt(2l),ttZ,ttW,tttt,ttWnq,ttbb

Backgrounds come from: Non-isolated leptons from jets Gluon-jets are similar to

quark-jets ( Worse in NLO ) Electron-jet overlapping

Lepton Isolation is crucial9 Mhiggs pionts from 120 to 200

GeVDefault CSC results of

MHiggs=160GeV

b

b

4 light jets

2 leptons

P

P

b

b2 light jets

3 leptons

P

P

Try a survival from huge backgrounds:•Jet inefficiency/multiplicity•Faked electron•NonIsolated muon from semileptonic heavy flavor


Basic selection e, mu, C4-jet: |η|<2.5; Pt>15 GeV/c e(Egamma): isEM=0x3FF,author=1,3 mu(StacoMu): IscombinedMuon=1 Calo Isolation: etcone20<10 GeV Track Isolation: trkPtmax20<2.0 GeV/c Cone Isolation:muon: R(mu,jet)>0.25 electron: R(e,jet) > 0.2 or R(e,jet)<0.1 and Eele/Ejet>0.65 ( Remove related jet ) Isolation: Nlepton>=2/3, Njets>=6/4 Nlep=2/3,Same charge (for 2L) Zveto: (75,100) (lep Pt> 6GeV/c) Muon_Pt > 20GeV/c

Baseline selection

Elec: eff=70.5%

Muon: eff=92.7%


ttH(HWW) Cut flow

2L

3L


Result uncertainties dominated by Background systematic uncertainty to estimate and correct it by real data driven method is essential !

precision(160GeV):

2L : 69%

3L : 66%

Combined: 47%

Can not sleep for backgrounds

Can not awake without errors

2L : S/B ~ 1.87/11.1

3L : S/B ~ 0.82/3.7


Combined systematic uncertainties

Take 10% Take 10%

+4.9% -1.8%

+0.0% -4.4%

A work competed/collaborated among France, German, and finally Chinese dominate CSC


A necessary supplementary/conformation of higgs productionNeeds a high luminosity >= 100 fb-1 , needs more efforts

+ Huge σtt@LHC ~ 850pb, BrtWb~1+ W polarization :

+ Top pair spin correlation :

– Precise Measurement of F & A parameters– Please refer to Zong-Guo’s talk this morning for theory interests


222

0 2cosΨ1

2cosΨ1

2sinΨ

23

dcosΨdN1 +F+F+F=

N RL

spin=1/2 1 1/2

)coscos1(41

)(cos)(cos1

212121

2

AddNd

N

1 21 1 (1 cos )

cos 2 DdN A

N d

L L R R L R R L

L L R R L R R L

σ(t t )+σ(t t )-σ(t t )-σ(t t )σ(t t )+σ(t t )+σ(t t )+(t t )

0.422A

0.290DA


0.0010.6950.304

0.422 -0.29 SM prediction


A very good/precise measurement on hadronic colliders !

+ Common backgrounds/base in ATLAS– Early data measurement

+ Precise test of SM– Possible detection of anomalous TGC

+ Focus on l±ν l+ l – channel– ZZ & Zjet dominate the backgrounds– 3 isolated high pT leptons, large MET, BDT tried


+ Skipping many analisis details :

+ Skipping many systematics details :


σS = 9.2%, σB = 18.3% Errors included

At different Lumi : 0.1, 1, 10 and 30 fb−1

+ All above published studies are still on going– Real data needs more efforts/works– Your supports for funds

+ Four progressive works in addition– RPV emu ( USTC )– Single top ( NJU & SDU )– Measurement of Z+( USTC )– ZH->ZW*W observation ( IHEP )– All results are preliminary, NOT official to show


' ''2

1 1ˆˆ ˆ ˆ ˆ ˆ ˆ ˆ ˆ ˆ ˆ2 2

ijk k kijijka b a b a b

R ab i j k ab i j k i j ab i iW L L E L Q D U D D L H

R-parity violating sneutrio resonance to e

-- Tri-linear on-spontaneous B- & L-number violation interactions stable proton

-- Bi-linear couplings neutrino mass for oscillation -- Constraints from indirect low energy experiments

Parity in SUSY can be partially violated in generic super-potential: 2 31 S L BR

10-20 folded improvement on RPV parameter sensitivity would be expected @ATLAS

Signal ( Comphep/pythia) and relevant backgrounds samples simulatedPID and event selection defined and backgrounds fraction estimatedUncertainties and suitable statistics investigated


Single top measurement

• The only known way to directly measure CKM matrix element Vtb

t-channel(~247pb)

W+t channel(~66pb)

s-channel(~11pb)

• Try to distinguish s-channel from t-channel production mode to test SM• Suffer top pair backgrounds, Smaller S-channel even suffer T channel backgrounds

PID and event selection defined and backgrounds fraction estimatedIn improving by echniques fromm MultiVariable Analysis



Presice test of SM

detect possible ZZ/Zanomaly SM ISR SM FSR Anomalous ZZ Anomalous Z

Joint ATLAS Z+group

proposed data driven analysis on Z+Jet Determine EM-like jet fake to gamma from di-jet sample

Fit the PDF of “prompt”gamma from Monte Carlo samples

+ SM Higgs should be observed/confirmed here– More important if theory of fermion-forbic Higgs

+ Measurement of σZH/σWH g∝ 2z / g2

w

– Combined with WH->W*W channel– expecting some errors cancelled

+ Progress– Relevant signal/backgrounds samples produced– Basic cut flow established– Some variables seem useful especially in MVA


+ Fermion-forbic Higgs ?+ W1 production in jWZj ( USTC & IHEP )

– H-J HE, Y-P KUANG, Y-H QI, B. ZHANG Phys. Rev. D 78, 031701(R) (2008)

+ VBF Higgs production with semi-leptonic W– CSC-NOTE discussed, overwhelming backgrounds

+ W+W+ production via anomalous HVV– Expect helps on generator from Theory side

+ ξ++ to same-charged lepton pair+ Seeming feasible, needing generator

+ SUSY study ? (e final state, USTC )



bb

ggtau

WW

ZZ

cc

γ γ Z γ

• bb, cc, tautau drop more steeply

• Zγ, especially γγ, increase much.

• WW starts dominance earlier

• ZZ contributes more

• Only below 200GeV

+ Larger γγ relatively+ important ZZ eventhough small branch+ WW significance in semileptonic mode


bb tautau gamma Zgamma WW ZZ

H SUSY Higgs

qqH

★★★ ★★★★★★

★?★★★★?★

★★★★★

channel lumi

1 qqH->qqWW*->qqjjlν 0.5

3qqH->qqZZ*

qq4l 70

qqjjll 6

+ Seems possible in experiment– ttbar, WZjets, ZZ, Zjets…– 3 isolated high pT leptons– large MET, 2 Forward jet tag– Possible Z/W1 reconstruction

+ Models are not what we care– Only if observable at lower luminosity– Only if executable generator presented– Thanks to Prof.CHEN, J.G.BIAN Z.X.ZHANG in CMS

Also thanks to Prof. HAN, B.ZHANG Lian-You SHAN TeV 3 @ Tango, Aug 25, 2009 26


W

W*

W

WH

V

V

q1

q2

Toooo many backgrounds !Forward jets as Handles to pick up signal from backgroundsReasonable signal production x-sec ~ hundred of fbYour precise estimation/calculation on signal and backgrounds ?

+ Many works done– Computing facility established and improved– Work quality is in improving

+ Many subjects are in exploration– Dynamical Balance among real data,

competition...– Progress with vitality– Expect &Thanks for your suggestions&helps

generators



Thanks !

you are welcome !


+ Not forbidden in theory

+ No gluon-gluon production– , nor decay to gluons

+ Decay to photons changed



Take : Γhff = 0.15* Γ0hff for all

From ZPC 53, (1992) 507

Documents

ATLAS physics studies