Taikan Suehara, ILC physics mini-workshop, 2009/01/21 page 1 SUSY and Tau-pair analysis with full...

Taikan Suehara, ILC physics mini-workshop, 2009/01/21 page 1

SUSY and Tau-pair SUSY and Tau-pair analysisanalysis

with full simulationwith full simulationin ILD detector modelin ILD detector model

Taikan Suehara

ICEPP, The Univ. of Tokyo


Benchmark processes:

Physics process for Physics process for optimizationoptimization

Processes (e+e-)

√S(GeV)

Observables

Comments

ZH, ZHe+e-X, 250 , mH mH=120GeV, test materials and ID

X 250 , mH mH=120GeV, test P/P

ZH, Hcc, Z 250 Br(Hcc) Test heavy flavour tagging and anti-tagging of light quarks and gluon

, Zqq 250 Br(Hqq) Same as above in multi-jet env.

Z* 500 AFB, Pol( Test 0 reconstruction and rec. aspects of PFA

tt, tbW, Wqq’ 500 AFB, mtop Test b-tagging and PFA in multi-jet events. mtop=175GeV

500 m Point 5 of Table 1 of BP report.W/Z separation by PFA


Tau-pairTau-pair


Motivation of tau-pair studyMotivation of tau-pair study• Detector challenge:

– A few particles in very narrow angle (=140)• Esp. 0 reconstruction from 2 s

• Physics motivation:– Anomalous coupling with Z’

• Cross section• Angular distribution (AFB)

– Charge ID is easy (cf. jet)• Polarization

– Angular distribution of decay daughters


1. Number of track <= 6– Veto hadronic events

2. Specialized jet clustering (TaJet)– Customized to taus (several particles within narrow angle)– 1 positive & 1 negative jets required for further analyses

3. Opening angle > 178deg– Suppress WW to llbackground

4. 40 < Evis < 450 GeV -> and Bhabha rejection

5. 2-electron and 2-muon veto– For bhabha and ee-> veto– E-ID by Ecal/total deposit, -ID by hit/track energy

6. |cos| < 0.9 for both jets– Bhabha is completely suppressed by this cut

BG suppression cutsBG suppression cuts


Result of SM suppression cutResult of SM suppression cut

Preliminary: luminosity not normalized, not contained.

All Tau#tr cut only

1108578

69489

Angle cut

139499

19504

Evis cut

26589

18996

ee, cut

19403

17378

cos cut

15284

14808

Remaining bhabhais 0 in 0.1 fb-1

-> Bhabha backgroundis < 10% of signal(Need more eventsfor precise estimation)


• # of bg events is much smaller than signal events– If we precisely estimate bg amount, statistical error of signal only

concerns to and AFB measurements• Effective cross section after cut is 490 fb (21.3% acceptance)

– Corresponds to 0.2 % error in and 0.28% error in AFB at 500 fb-1

Forward-backward asymmetryForward-backward asymmetry

SM calculation(Red: left, Blue: right)


Decay modes in ADecay modes in Apolpol analysis analysis


AApolpol calculation ( calculation ( mode) mode)

Stat errorin 500fb-1

Pol estat shift estat shiftGLD 47.17%± 4.54% 1.25% -7.01% 54.89%± 4.67% 1.28% -4.49%GLD' 49.45%± 4.52% 1.25% -9.76% 52.11%± 4.64% 1.28% -7.65%J 4LDC 49.14%± 4.60% 1.28% -12.41% 52.20%± 4.68% 1.30% -10.28%LDC' 52.72%± 4.30% 1.22% -5.46% 57.95%± 4.49% 1.27% -3.25%GLD -25.62%± 4.77% 1.35% -6.20% -25.41%± 5.23% 1.48% -7.58%GLD' -24.04%± 4.79% 1.36% -9.23% -23.33%± 5.18% 1.47% -9.81%J 4LDC -28.57%± 4.88% 1.38% -7.58% -27.73%± 5.22% 1.48% -9.63%LDC' -18.93%± 4.63% 1.33% -6.57% -19.11%± 5.12% 1.48% -6.15%

Apol (count) Apol(linear fit)

eL(80%)

eR(80%)

Value shift due to the mode BG

Values obtained bysignal-only events!


• Clear difference observed in invariant mass distributions.– LDC’s best, larger is better in Jupiter geometries.– Mark confirmed the granularity affects the mass distributions.

• Three candidates in mode selection– No 0 mass cut, 0 cut with left edge included / excluded

and and 00 reconstruction reconstruction


AApolpol calculation ( calculation ( mode) mode)

Pol estat shift estat shiftGLD 34.06%± 4.26% 1.17% -2.68% 34.53%± 6.78% 1.86% -1.66%GLD' 38.66%± 4.30% 1.19% -3.59% 42.62%± 7.36% 2.04% -1.10%J 4LDC 34.86%± 4.47% 1.24% -4.24% 36.30%± 8.24% 2.29% 0.79%LDC' 35.62%± 4.13% 1.17% -3.36% 36.81%± 6.05% 1.72% -0.99%GLD -28.33%± 4.87% 1.37% 4.91% -30.89%± 8.32% 2.35% 3.70%GLD' -30.87%± 5.00% 1.42% 3.67% -34.26%± 9.36% 2.66% 0.88%J 4LDC -35.34%± 5.38% 1.52% 2.53% -36.45%± 11.18% 3.16% -1.90%LDC' -32.70%± 4.89% 1.41% 2.89% -32.46%± 7.86% 2.27% -0.49%

Apol (nopimasscut) Apol(wpimasscut)

eL(80%)

eR(80%)

Stat errorin 500fb-1

Value shift due to the mode BG

Values obtained bysignal-only events!


Tau-pair SummaryTau-pair Summary• Tau-pair events are analyzed in ILD framework.• SM background can be efficiently removed

by appropriate cuts.– Bhabha statistics is short -> need pre-selection– No events– Weighting of background is needed-> All will be performed in ILD reference detector for LOI

• Apol analysis is implemented, showing larger and highly granulated detectors give better performance.

• Up to 5 TeV Z’ boson can be measured by measuring anomaly to the tau-pair production.


SUSYSUSY


• Qqbar 4jet events, 130(chargino),30(neutralino) fb• 500 fb-1 with full simulation• Chargino/neutralino must be separated by

identifying daughter W/Z.• Main BG: SM WW -> 4 jets (10000 fb), aa_WW etc.

SUSY jet modeSUSY jet mode


• # of tracks > 20– Remove leptonic events

• 150 GeV < Evis < 300 GeV– Remove 2-photon and qq/qqqq events

• Maximum lepton energy: < 20 GeV– Remove semileptonic events

• All jet > 5 GeV– Remove 2-jet / misclustering events

• |cos()| < 0.9 for all jets– Remove t-channel events

(sneutrino is heavy in point5)• All jets have at least 2 tracks

– Remove taus• Missing Pt > 10 GeV

– Remove 2-photon, WW events

SM Rejection cutsSM Rejection cuts


SM background rejectionSM background rejection

SM background is well suppressed.(need more aa_qqqq events)

LDC’


Di-jet mass distributionDi-jet mass distribution

All combination, reco, point5


Di-jet mass SM backgroundDi-jet mass SM background

No specific structure, I don’t include it now (need more stat.)


Fitting ch1/ne2 combinedFitting ch1/ne2 combined

Chi-square/NDF is around1, not so bad. (Fitting range isrestricted, fit is single-2dgaus each for W/Z with pol1 bg,8 params)


• Chargino amount: 52.8 +/- 1.06 (2.0%)• Neutralino amount: 7.57 +/- 0.46 (6.1%)

– All 8 parameters are float.– Not normalized to cross section.– Neutralino is not so good.

• Chargino/neutralino is different by about 20% (less neutralino)– Acceptance by SM rejection cut might be

different – need to be checked

Stat. error (preliminary)Stat. error (preliminary)


22 distribution / mass cut distribution / mass cut


• SUSY mass is determined by kinematics– Daughter W/Zs have characteristic energy

distribution• Fitting function:

– For neutralino: erf(left) x erfc(right)– For chargino: erf(left),

conbolution of linear and erfc for right• Generator-level energy distributions (by

Akiya):

Mass fit of chargino/neutralinoMass fit of chargino/neutralino

Chargino (W) Neutralino (Z)


Chargino mass fitChargino mass fit

MC cut and nocut shape is almost the same (wo left edge).No significant difference between geometries can be seen.


• Fitting function:3rd polynomial (4 param) (center) / 0 (edge) convoluted with a Gaussian with as linear function of energy (2 param)edge position: 2 param, total # of parameters = 8

• Cheat fitting:1. fix edge positions at true value, fit other 6 parameters.2. fix those 6 parameters and fit edge positions.

• No significant difference between geometries.

Chargino mass fit resultsChargino mass fit resultsinput unit

Chargino mass 215.41 ± 1.15 216.29 ± 1.55 214.99 ± 1.20 210.21 GeVLSP mass 121.59 ± 0.72 120.78 ± 0.89 120.40 ± 0.76 117.36 GeVChargino (cheat) 210.51 ± 0.56 210.67 ± 0.51 210.46 ± 0.52 210.21 GeVLSP (cheat) 117.59 ± 0.58 117.61 ± 0.47 117.49 ± 0.46 117.36 GeVWidth L (cheat) 3.59 ± 0.11 3.30 ± 0.08 3.46 ± 0.12 GeVWidth R (cheat) 3.79 ± 0.21 3.69 ± 0.17 3.67 ± 0.19 GeV

GLD GLD' J 4LDC


Neutralino mass fitNeutralino mass fit

Distribution in LDC is slightly broader (worse resolution).Chargino background might not be negligible for lower edge.


• Fitting function:Error function (left) x Complementary error function (right)Width of left and right is the same, # of parameters = 4

• Cheat fitting:Same as chargino

• J4LDC gives slightly larger width than other two.Corresponding fitting error is enhanced.

Neutralino mass fit resultsNeutralino mass fit resultsinput unit

Xn2 mass 214.61 ± 0.50 215.31 ± 0.46 214.04 ± 0.63 210.21 GeVLSP mass 120.51 ± 0.33 120.88 ± 0.32 120.40 ± 0.36 117.36 GeVXn2 (cheat) 214.06 ± 0.36 214.67 ± 0.36 214.14 ± 0.39 210.21 GeVLSP (cheat) 120.34 ± 0.31 120.78 ± 0.31 120.42 ± 0.34 117.36 GeVWidth (cheat) 7.42 ± 0.20 7.20 ± 0.22 8.04 ± 0.21 GeV

GLD GLD' J 4LDC


Angular distributionAngular distribution

W decay angle Chargino production angle

Detailed analysis is to be done.


• SUSY benchmark is ongoing• Cross section is obtained from 2d W/Z

mass spectrum• W/Z mass separation is feasible• Preliminary mass fit result is obtained

SUSY summarySUSY summary


Short commentsShort commentson Jet Clusteringon Jet Clustering


Motivation of new jet clusteringMotivation of new jet clustering• Most of important physics processes

have multi-jet final states (usually with number of heavy flavor jets)– ZHH: 6 jets with 4 b-jets

• Cross section of Z to ll and nn mode is too small (~0.06fb), analysis of 6-jet final states (~0.13fb) is inevitable.

• ttbar background (~1pb) is very severe. 4 b-tagging with high tagging/anti-tagging efficiency is necessary.

– ttH: 6-8 jets with 4 b-jets– tt: (mostly as background) 6 jets with 2 b-jets


SampleSample

IP

Traditional jet clustering (not using vertex info)


SampleSample

IP

Off-vertex tracks

Jet clustering with Vertex info

Finding a secondary vertexFinding jet-coresAssociate fragments


Modified ZVTOP sampleModified ZVTOP sample


• ZVTOP – done well with slight modification– Large-angle particles are missing? – need check

• Clustering algorithm using vertices– Implemented – might be not so bad– Without vertex, performance is almost the

same as traditional Durham method• Angular distribution of reconstructed jets

– Slightly worse in new clustering• Might be due to mis-vertexing (about 1/5-10 events)

• Flavor tagging performance – now checking– Can be done within ~2 weeks

Performance/CommentsPerformance/Comments

Taikan Suehara, ILC physics mini-workshop, 2009/01/21 page 1 SUSY and Tau-pair analysis with full...

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