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Yu Bai (IHEP, Beijing)On behalf of the SUSY Weak Production team
ACCM 23, Mar 3, 2013
Search of SUSY Weak Production with hadronic taus
SUSY Approval Meeting 2
Support note: https://cds.cern.ch/record/1500884
Editors:Anyes TaffardChristophe ClementFederica LeggerXuai Zhuang
Editorial Board:Dan Tovey (chair)Shirkma BresslerMasahiro KuzeSadrine Laplace
Present study on 20.69 fb-1 , √s=8 TeV Data
Conference note: https://cds.cern.ch/record/1519195
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Outline
• Introduction
• Signal grids
• Object and event selection
• Signal region definition
• Background estimation
• Results
• Interpretation
• Summary
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Introduction
Either for natural SUSY, or heavy scalars, it is fairly generic for the gauginos to be light.
Higgs into di-photon rate can be enhanced via staus without changing the Higgs to WW/ZZ rates, so light stau with large mixing may help
First study of direct gaugino through the final states with at least two taus, which is complementary of emu final states .
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Signal GridsDirect Gaugino Decay
pMSSM Signal Grid: • Heavy Squarks and Gluinos• tan β = 50• M1 = 50 GeV• M2 and μ ranging from 100 to
500 GeV• Mass of stau fixed at 95 GeV,
other sleptons are heavy
Mode A (chargino-neutralino decay):
Mode C (chargino-chargino decay):
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Objects Pre-Selection
Electrons and muons• Base line Selection• Overlap removal
Taus• Baseline• Overlap removal• Loose tauid• Tight tauid(at least 1 in each event)
MET : Egamma10NoTau
Trigger : Di-tau trigger || soft-met trigger• Di-tau Trigger: EF_tau29Ti_medium1_tau20Ti_Medium_1• Soft-met Trigger: EF_xe80_tclcw
Jet :• Baseline• Overlap removal • L25: light jet• B20: bjet• F30: forward jet
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SR definition Two SRs have been defined
require at least 1 OS tau pair
one SR is after jet veto
another SR is only applying
bjet veto
Suppress Z+jets BG through Z-veto
MET>40 GeV to suppress fake tau background
Apply large mT2 cut to enhance SUSY sensitivity
mT2 cut has been optimized
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SR Optimization - mode A
mT2 > 80 GeV mT2 > 90 GeV mT2 > 100 GeV
m
T2 je
t vet
o
mT2
b-ve
to
• mT2 jet-veto: pick mT2 >90 GeV (similar performance)• mT2 b-veto: mT2 >100 GeV (best performance)• Other models are checked, consistent with mode A
8
5fb-1 data usedmT2 jet vetoMt2>80GeV: 3Mt2>90GeV: 2Mt2>100GeV: 1mT2 b-vetoMt2>80GeV: 20Mt2>90GeV: 4Mt2>100GeV: 2
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Background components in SRs
Two classes of backgrounds: fake tau (qcd+W, ~75-80%) and real tau background (top, Z+jets, diboson)
Fake tau background: estimated with data-driven approach (ABCD method) Real tau background: use MC simulation
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Background Estimation : fake tau background
• Fake Background
• QCD di-jet (2 fake tau)
• W+jets (1 fake tau)
• Can be estimated together due to same fake
tau character
• Not modeled well in MC due to fake rate
• Huge cross section, limited MC statistics
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The ABCD method
Use transfer factor (TF) from QCD events (low mT2 region from data) and take the TF difference between QCD and W+jets as systematics
• Variables:
• mT2 , tauid• Base line control region
• A high mT2, loose tauid• B low mT2,, loose tauid• C low mT2, tight+medium tauid
• extrapolation from A to D through a TF (C/B)
• Alternative ABCD method checked (W CR-AB)
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Correlation between tauid and mT2
mT2 jet veto mT2 b-veto
No strong correlation between tau id and mT2
The correlation has been taken into account to syst.
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Fake tau background purity
mT2 jet veto mT2 b-veto
2 lo
ose
taui
d ti
ght t
au v
eto
1 tig
ht ta
u +
1med
ium
tau
• In QCD+W CR-C,B (low mT2 region) , QCD + W purity is high (>96%)
• In QCD+W CR-A (high mT2 region), QCD+W purity is ~90%
• non fake tau bkg in CR-A has been subtracted from MC and taken into account to syst.
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Signal contamination in region AmT2 jet-veto mT2 b-veto
Mod
e A
Mod
e C
The SUSY contamination in the QCD+W control region A is around 10% for SR OS-mT2 and OS-mT2-nobjet
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Fake tau background estimation: Result
mT2 jet veto mT2 b-veto
Good Data/MC Agreement in non-signal region (mT2 < 90 GeV)
QCD+W Results:In mT2 -jet veto region : • 8.38+/-2.98
In mT2 b-veto region : • 12.23+/-4.48
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Kinematic distributions
Good data/MC agreement for leading and next leading tau pt and eta distributions
The ABCD method works well
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Validation of QCD+W estimation I
We validated QCD+W estimation in different SM bkg enriched region.
The QCD+W control region definition is close to SM BG validation regions but use loose tau id
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Validation of QCD+W estimation I
Good data/MC agreement in all BG enriched VRs
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Validation of QCD+W estimation II: Alternative ABCD Method
We also checked the QCD+W estimation using CRs with different bkg components (1L+1M w/o tight).
Good data/MC agreement in alternative ABCD method
The ABCD method proves to be reliable even change the components in the control regions
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Real Tau Background Estimation and Validation
top and Z+jets:
No event left at one of the SRs due to low statistics use “ABCD”-like MC driven estimation as default CR definition is similar as QCD+W CR definition but from
MC events (loose tau id, remove MET cut)
Diboson has reasonable statistics, use the MC simulation directly and validated with above “ABCD”-like method
we use two different sets of SFs for real and fake taus. This is why we don't check that all taus are real when we use MC
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Real Tau Background
The numbers in SRs are consistent between MC prediction and MC-driven estimation within statistical uncertainty
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Results Results from SM
Bkg estimation are compared with the total number of data events in table 19
mT2 distribution for data and SM bkg in eash SR is at fig 20.
The observed and expected number of events in the table (together with uncertainty) are used to calculate the exclusion limit
22
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Model independent upper limits on the visible cross-section
Table 22 shows the model-independent upper limits based on the observed and expected number of events in each SR
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Best Exclusion Limits – simplified model
Masses of degenerate and are excluded up to 300-330 GeV in the chargino-neutralino simplified model for light (below 50-100 GeV); In the chargino-chargino simplified model, we exclude masses of 200< <330GeV for very light ( below 30-50GeV)
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Best Exclusion Limits - pMSSM
Holes formed due to relatively lower signal yield with higher statistical err.
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Summary Two signal regions with high mT2 cut have been defined
and optimized No significant excess observed in the signal regions.
Given exclusion limits with pMSSM and simplified model (mode A,C)
Masses of degenerate and are excluded up to 300-330 GeV in the chargino-neutralino simplified model for light (below 50-100 GeV)
In the chargino-chargino simplified model, we exclude masses of 200< <330GeV for very light (below 30-50GeV)
Aiming at Moriond CONF note
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Backup
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Acceptance*Efficiency of at least two taus for signal grid
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Triggers
Using following Oring trigger:
• EF tau29Ti medium1 tau20Ti medium1 => 2taus, pT
leading > 40 , pTnext-leading > 25 GeV
• EF xe80 tclcw, =>MET> 150 GeV
Good Turn-on Curve
Efficiency of EF_xe80_tclcw
Trigger Matching• Leading tau matches to EF tau29Ti medium1• Next Leading tau matches to tau20Ti medium1
Tau Trigger Reweighting
• Use TauSF from tau performance group recommendation
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Datasets Data : 20.69 fb-1 , √s=8 TeV (JetTauEtmiss Stream)
Standard Model MC:
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Objects and Events Selection
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Overlap removal
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mT2 without MET cut
mT2 b-vetomT2 jet-veto
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Systematic Uncertainty of QCD+W estimation
Correlation between tauid and mT2 : difference between high mT2 region and low mT2 region
• high mT2 : 40 GeV< mT2 < 90 GeV• low mT2 : mT2 < 40 GeV
transfer factor difference: •
• T_W : from MC• f_W: from fitting on W MC mT2 distribution• W fraction in region A: 17%
Non QCD/W backgrounds in region A• Systematic uncertainty taken from background study
Statistic uncertainty in region A
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W fraction estimation
OS-mT2
OS-mT2 -nobjet
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The result of fake tau background estimation
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mt2 distribution of alternative ABCD method
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Correlation between tauid and mt2 in alternative ABCD method
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Results from alternative ABCD method
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Result with alternative JVF Cut(>0.25)
D: SR (medium + tight tau, mT2>90GeV) A: Top/Z/Diboson Control Region: close to SR except
using loose tauID and remove met cut CB: Normalization Region, close to D,A except
40<mT2<80GeV for OS mT2 region
We can extrapolate from Top/Z/Diboson Control region A to signal region D trough a transfer factor from C/B: D = A* C/B
A D
B C
Loose Medium Tau ID
MT2Signal Region
Top/Z/Diboson Control Region
2012/11/20 41
ABCD-like method
Normalization Region
SUSY BG Meeting
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mt2 distribution of Z+jets
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Z+jets mt2 fit
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Z+jets systematic uncertainty: mt2 jet-veto
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Z+jets systematic uncertainty: mt2 b-veto
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mt2 distribution of top
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mt2 fit of top
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Top estimation systematic uncertainty : mt2 jet-veto
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Top estimation systematic uncertainty : mt2 b-veto
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Diboson samples and events number(raw number) in SR
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Diboson systematic uncertainty : mt2 jet-veto
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Diboson systematic uncertainty : mt2 b-veto
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ABCD-like diboson estimation
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Acceptance of at least two taus for pMSSM
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Acceptance of at least two taus for modeA/C
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Signal Optimisation
• Signal Region– SR@OSmt2 mt2>90GeV– SR@OSmt2-nobjet mt2>100GeV
• Signal Mode– Pmssm– Simplified modeA– Simplified modeC
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Signal Optimization• Background estimation in Signal region:
– The number of events with 5 fb-1 are scaled to 20.69 fb-1.
– Systematical uncertainty is quoted as 15%.
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SR opt with 5fb-1 data@OSMT2
modeA
modeC
pMSSM
Data (5fb-1) Mt2>80GeV: 3 Mt2>90GeV: 2 Mt2>100GeV: 1
Mt2>80GeV Mt2>90GeV Mt2>100GeV
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SR opt with 5fb-1 data@OSMT2-nobjet
modeA
modeC
pMSSM
Data (5fb-1) Mt2>80GeV: 20 Mt2>90GeV: 4 Mt2>100GeV: 2
Mt2>80GeV Mt2>90GeV Mt2>100GeV
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Zn check for two modeA grids• OSmt2 modeA• mt2>80@ C1 = 150 N1 = 50 s = 23.3351 b = 11.9228 significance = 4.51045• mt2>90@ C1 = 150 N1 = 50 s = 18.8384 b = 7.94852 significance = 4.51581• mt2>100@ C1 = 150 N1 = 50 s = 16.2078 b = 3.97426 significance = 5.20883
• mt2>80@ C1 = 250 N1 = 100 s = 9.86776 b = 11.9228 significance = 2.10468• mt2>90@ C1 = 250 N1 = 100 s = 6.83389 b = 7.94852 significance = 1.83262• mt2>100@ C1 = 250 N1 = 100 s = 4.65025 b = 3.97426 significance = 1.76165
• OSmt2-nobjet modeA• mt2>80@ C1 = 150 N1 = 50 s = 41.1117 b = 79.4852 significance = 2.35261• mt2>90@ C1 = 150 N1 = 50 s = 32.6729 b = 15.897 significance = 5.19816• mt2>100@ C1 = 150 N1 = 50 s = 24.8696 b = 7.94852 significance = 5.65192
• mt2>80@ C1 = 250 N1 = 100 s = 18.947 b = 79.4852 significance = 1.10004• mt2>90@ C1 = 250 N1 = 100 s = 12.4417 b = 15.897 significance = 2.23432• mt2>100@ C1 = 250 N1 = 100 s = 9.16587 b = 7.94852 significance = 2.41341
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Expected signal yields(21fb-1)SR@OSmt2: pMSSM
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Expected signal yields(21fb-1) SR@OSmt2-nobjet: pMSSM
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Signal yields at x/y axis (OSmt2)
• RunNb=164475 mu=100;M2=100 signal yield=0+0RunNb=164476 mu=110;M2=100 signal yield=39.9135+26.3983RunNb=164477 mu=120;M2=100 signal yield=40.9171+25.6674RunNb=164478 mu=140;M2=100 signal yield=16.2225+15.4187RunNb=164479 mu=160;M2=100 signal yield=0RunNb=164480 mu=180;M2=100 signal yield=0RunNb=164481 mu=210;M2=100 signal yield=0RunNb=164482 mu=250;M2=100 signal yield=0RunNb=164483 mu=300;M2=100 signal yield=0RunNb=164484 mu=350;M2=100 signal yield=0RunNb=164485 mu=400;M2=100 signal yield=0RunNb=164486 mu=450;M2=100 signal yield=0RunNb=164487 mu=500;M2=100 signal yield=0RunNb=164488 mu=100;M2=110 signal yield=0RunNb=164501 mu=100;M2=120 signal yield=50.8324+27.6802RunNb=164527 mu=100;M2=160 signal yield=1.46859+3.08171RunNb=164540 mu=100;M2=180 signal yield=6.33867+6.13021RunNb=164553 mu=100;M2=210 signal yield=13.1495+8.33708RunNb=164566 mu=100;M2=250 signal yield=4.85258+4.5601RunNb=164579 mu=100;M2=300 signal yield=27.8572+11.0293RunNb=164592 mu=100;M2=350 signal yield=9.70794+7.27852RunNb=164605 mu=100;M2=400 signal yield=0RunNb=164618 mu=100;M2=450 signal yield=0RunNb=164631 mu=100;M2=500 signal yield=0
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Expected signal yields(21fb-1) OSmt2-jetveto(left) / OSmt2-bjetveto(right)
modeA
modeC
modeA
modeC
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Cross-section upper limits for Dstau samples
• A rough idea of the value. • More will be done soon.• Better exclusion cross-section upper limits is
provided by OSmt2 jet veto SR.
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164604:mu=500,M2=350• Cut 0 : 10000 no cut• Cut 1 : 10000.000977 GRL cut• Cut 2 : 10000.000977 LAr hole veto + TTC incomplete event veto• Cut 3 : 9953.8867188 jet cleaning + LarError cut • Cut 4 : 9868.9423828 >= 1 primary vertex with >4 tracks• Cut 5 : 9735.7275391 cosmic muon veto+ Bad muon veto• Cut 6 : 3053.902832 at least 2leptons• Cut 7 : 822.21057129 tau-tau (pt>40,25GeV or MET>150GeV) ***• Cut 8 : 430.58502197 tau-tau with trigger match• Cut 22 : 78.932563782 //SR4: OS && jet veto &&Z veto && MET>40• Cut 24 : 30.94043541 && mT2_new > 90 ***• Cut 25 : 224.74725342 SR5:OS && bjet veto && zveto• Cut 26 : 185.11817932 && MET>40GeV• Cut 27 : 49.082584381 && mT2 > 100 GeV
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164602:mu=400,M2=350• Cut 0 : 10000 no cut• Cut 1 : 10000.000977 GRL cut• Cut 2 : 10000.000977 LAr hole veto + TTC incomplete event veto• Cut 3 : 9963.6582031 jet cleaning + LarError cut • Cut 4 : 9873.9707031 >= 1 primary vertex with >4 tracks• Cut 5 : 9744.5654297 cosmic muon veto+ Bad muon veto• Cut 6 : 3345.3520508 at least 2leptons• Cut 7 : 819.33990479 tau-tau (pt>40,25GeV or MET>150GeV) ***• Cut 8 : 480.61099243 tau-tau with trigger match• Cut 22 : 77.047554016 //SR4: OS && jet veto &&Z veto && MET>40• Cut 24 : 18.065355301 && mT2_new > 90 ***• Cut 25 : 220.07788086 SR5:OS && bjet veto && zveto• Cut 26 : 177.69471741 && MET>40GeV• Cut 27 : 34.182556152 && mT2 > 100 GeV
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Exclusion Limits – mode A
Masses of degenerate and are excluded up to 300-330 GeV in the chargino-neutralino simplified model for light (below 50-100 GeV)
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Exclusion Limits – mode C
In the chargino-chargino simplified model, we exclude masses of 200< <330GeV for very light ( below 30-50GeV)
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Exclusion Limits - pMSSM
Holes formed due to relatively lower signal yield with higher statistical err.
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