idenficaonandenergycalibraonof ......wtaunu, ztautau and ttbar events from data tau reconstruction...
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Iden%fica%on and energy calibra%on of hadronically decaying tau leptons with the
ATLAS experiment.
Almut Pingel Niels Bohr Ins3tute
on behalf of the ALTAS collabora3on
ICHEP, Valencia (Spain) 3 July 2014
Physics with Taus
3 July 2014 Almut Pingel (NBI) -‐ ICHEP2014 2
[GeV]Tm0 100 200 300 400 500 600
Even
ts /
20 G
eV
1
10
210
310
410
510
Selection+HHeavy
Data 2012oTrue misIDoAJet
Uncertainty = 250 GeV ( x 10)+Hm
maxh
) = 50, MSSM m`tan(
-1 Ldt = 19.5 fb0 = 8 TeVs
ATLAS Preliminary
ln(1
+S/B
) w. E
vent
s / 1
0 G
eV
010203040506070
[GeV]ooMMCm
60 80 100 120 140 160 180 200
w. D
ata-
Bkg.
0
10=1)µ( oo A(125)H=1)µ( oo A(110)H=1)µ( oo A(150)H
Data=1)µ( oo A(125)H
oo AZOthersFakesUncert.
ATLAS Preliminary VBF+Boostedoo AH
-1 L dt = 20.3 fb0 = 8 TeVs
[GeV]Z’m500 1000 1500 2000
) [pb
]oo
AZ’(
BR ×) Z’
App(
m
-310
-210
-110
1
ATLASPreliminary
-1L dt = 19.5 fb0 = 8 TeVs channelhadohado
Expected limitm 1±Expected m 2±Expected
Observed limitSSMZ’
th. uncert.SSMZ’
Higgs à ττ Charged Higgs search Z’ à ττ search
SM physics: Zàττ , Rbar, tau polariza3on in Wàτν, … Beyond SM: SUSY searches, charged Higgs, Z’, …
See backup for documenta3on of performance and physics results
Hadronic Tau Decays in ATLAS
29 May 2012 Almut Pingel (NBI) - Atlas Weekly 2
Tau Object
Tau Identification (tau ID)
discrimination against QCD
jets
Muon Vetosuppression of muon
fakes additional to muon overlap removal
Electron Vetosuppression of electron fakes additional to
electron overlap removal
Tau Energy Scale (TES)
calibration of energy, eta
tag&probe analysestests and measurements of efficiencies and TES, using Wtaunu, Ztautau and ttbar
events from data
Tau Reconstructionseeded by jets, track
and vertex association, calculation of
identification variables
3 July 2014 Almut Pingel (NBI) -‐ ICHEP2014 3
Trigger
Reconstruc3on
Discrimina3on against electrons
Discrimina3on against muons
Energy calibra3on
T&P measurements
Discrimina3on against QCD jets
Tau Lepton
• mτ = 1.777 GeV • Most taus decay inside beam pipe • Hadronic decays: 65% – Mainly charged + neutral pions – 1 or 3 tracks – Energy deposits in EM and HAD calorimeters
• Main background: QCD jets • Reconstruc3on: – Seeded by an3-‐kT jets (R < 0.4) – Tracks: pT > 1 GeV, dR < 0.2
3 July 2014 Almut Pingel (NBI) -‐ ICHEP2014 4
Hadronic Tau Decay Characteris3cs
corecorrf
0 0.2 0.4 0.6 0.8 1 1.2
Sam
ple
Frac
tion
/ 0.0
20.02
0.04
0.06
0.08
0.1
0.12
0.14
0.16 ντ →, W ττ →Z,Z’
Data 2012 (jets)
= 8 TeVs, -1 L dt = 740 pb∫ > 15 GeV
Tp1-prong,
ATLAS Preliminary
3 July 2014 Almut Pingel (NBI) -‐ ICHEP2014 5
• Isola3on • Lateral shape – Narrow energy deposi3on – Small track to jet axis distance
• Leading track momentum frac3on • Secondary vertex • Invariant mass • π0 informa3on • Longitudinal shower shape • Transi3on radia3on in TRT
Centrality frac3on
τ
Tau Iden3fica3on
VtxN0 5 10 15 20 25 30
Sign
al E
ffici
ency
0
0.2
0.4
0.6
0.8
1
1.2
TauBDT looseTauBDT mediumTauBDT tight
1 Prong| < 2.5d > 15 GeV, |
Tp
= 8TeVsSimulation 2012, Preliminary ATLAS
3 July 2014 Almut Pingel (NBI) -‐ ICHEP2014 6
• Boosted Decision Trees (BDTs) • Separately for jets (tau ID) and electrons (e-‐veto) • Separately for 1-‐prong and 3-‐prong taus • Minimum tau pT : 15 GeV • Pile-‐up corrected input variables à pile-‐up robust
Signal Efficiency0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
Inve
rse
Back
grou
nd E
ffici
ency
1
10
210
310
410
TauBDT Summer 2012
TauBDT Winter 2013
1 Prong| < 2.5d > 15 GeV, |
Tp
= 8 TeVsData+Simulation 2012,
Preliminary ATLAS
Signal eff. vs number of ver3ces Background rejec3on vs signal eff.
Tau Energy Scale (TES)
3 July 2014 Almut Pingel (NBI) -‐ ICHEP2014 7
• Energy scales for taus: EM scale à LC scale à TES
• TES: compensate differences of reconstructed and true visible energy (MC based) – Specific hadron mix – Energy loss on the way – Pile-‐up contribu3ons
• Specific for number of tracks =1 and >1, different η-‐regions
Momentum resolu3on
Energy response
Performance Measurements
3 July 2014 Almut Pingel (NBI) -‐ ICHEP2014 8 8
• Z à τe/μ τhad tag-‐and-‐probe analysis on 2012 data
• Requirements on – visible mass mvis(e/μ, τhad-‐vis) – missing ET (direc3on, transverse mass)
to suppress Z à ll, W à lν
Performance Measurements
3 July 2014 Almut Pingel (NBI) -‐ ICHEP2014 9
trackc+cN
0 1 2 3 4 5 6 7 8 9
Even
ts
02000400060008000
1000012000140001600018000200002200024000
ATLAS Preliminary
= 8 TeVs, -1 L dt = 8.5 fb0
channel, BDT Medium IDhadoµoAZ
Data 2012Fit
o1-prong omulti-prong
electronsjets
9
trackc+cN
0 2 4 6 8 10 12 14 16
Even
ts
0
5000
10000
15000
20000
25000
30000
35000 ATLAS Preliminary
= 8 TeVs, -1 L dt = 8.5 fb0
channel, Before IDhadoµoAZ
Data 2012Fit
)ooA (Zo
electronsjets
Medium tau ID
No tau ID • Z à τe/μ τhad tag-‐and-‐probe
analysis on 2012 data • Requirements on – visible mass mvis(e/μ, τhad-‐vis) – missing ET (direc3on, transverse mass)
to suppress Z à ll, W à lν • Data-‐driven background
es3ma3on for jet background: Template fit of extended track mul3plicity
Performance Measurement: tau ID
Tau ID BDT Score0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
Even
ts0
1000
2000
3000
4000
5000
6000
7000
Even
ts
0
2000
4000
6000
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10000
12000
14000
16000
18000
20000Data 2012
(OS-SS)ooAZW+jets (Data driven)
ll (OS-SS)A*aZ/
Top (OS-SS)Other (OS-SS)Same SignStat. Unc.
-1 L dt = 20 fb0 = 8 TeVs PreliminaryATLAS
(full sim.)ooAZ
Tau ID BDT Score0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1D
ata/
MC
0.60.8
11.21.4
3 July 2014 Almut Pingel (NBI) -‐ ICHEP2014 10
Loose Medium Tight
Scal
e Fa
ctor
0.8
0.9
1
1.1
1.2
1.3 ATLAS Preliminary = 8 TeVs, -1 L dt = 8.5-14.3 fb0
Data 2012BDT ID, Inclusive
channelhadoµoAZ channelhadoeoAZ channelihadoAW
+jets channelhadoAtt combinationhadolepoAZ
• Data/MC correc3on factors: – Combina3on of Z à τμ τhad and Z à τe τhad results
– No pT dependence, small η dependence (barrel/end-‐cap)
– Uncertain3es: (2 – 6)% • Cross check: W à τν and Rbar:
Consistent results in all channels • Outlook: “Con3nuous” Data/MC
correc3on factors à explore full BDT score in physics analysis
Performance Measurement: TES
3 July 2014 Almut Pingel (NBI) -‐ ICHEP2014 11
• (a): Deconvolu3on method – Single par3cle response – Low pileup data taking, MC
• (b): Z à τμ τhad tag-‐and-‐probe – Invariant mass distribu3on – 2012 data
• Uncertain3es on total TES (a), Data/MC differences (a,b)
• Uncertain3es: (2 – 4)%, depending on η, ET, number of tracks
[GeV]vism20 40 60 80 100 120
Even
ts /
3 G
eV0
1000
2000
3000
4000
5000
6000
Even
ts /
3 G
eV
0
2000
4000
6000
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10000 Data 2012 (OS-SS)ooAZ
(OS-SS)llA*aZ/+jets (OS-SS)W
Top (OS-SS)Other (OS-SS)Same SignStat. Unc.
-1 Ldt = 20.3 fb0 = 8 TeVs
PreliminaryATLAS
(full sim.)ooAZ
[GeV]vism20 40 60 80 100 120D
ata/
MC
0.60.8
11.21.4
Invariant mass
TES Uncertainty
Summary
• BDTs for discrimina3on of hadronic tau decays from jets and electrons
• Tau energy scale to restore the true visible energy • Performance measurements on data for valida3on – MC/Data scale factors around 1 – Uncertain3es < 6% (ID) and < 4% (TES)
• All algorithms / measurements are stable with changing pile-‐up condi3ons!
3 July 2014 Almut Pingel (NBI) -‐ ICHEP2014 12
Summary
3 July 2014 Almut Pingel (NBI) -‐ ICHEP2014 13
Thank you J
à Visit also the poster on “Iden3fica3on of hadronically decaying tau leptons with the ATLAS experiment” by Dirk Duschinger!
• BDTs for discrimina3on of hadronic tau decays from jets and electrons
• Tau energy scale to restore the true visible energy • Performance measurements on data for valida3on – Data/MC correc3on factors around 1 – Uncertain3es < 6% (ID) and < 4% (TES)
• All algorithms / measurements are stable with changing pile-‐up condi3ons!
BACKUP
3 July 2014 Almut Pingel (NBI) -‐ ICHEP2014 14
Tau Performance
• Tau Iden3fica3on: ATLAS-‐CONF-‐2013-‐064, hRps://cds.cern.ch/record/1562839
• Tau energy scale: ATLAS-‐CONF-‐2013-‐044, hRps://cds.cern.ch/record/1544036
• Tau trigger: ATLAS-‐CONF-‐2013-‐006, hRps://cds.cern.ch/record/1510157
• hRps://twiki.cern.ch/twiki/bin/view/AtlasPublic/TauPublicCollisionPlots
3 July 2014 Almut Pingel (NBI) -‐ ICHEP2014 15
Physics with Taus (CONF notes) • Higgs à ττ: ATLAS-‐CONF-‐2013-‐108,
hRps://cds.cern.ch/record/1632191 • Charged Higgs: ATLAS-‐CONF-‐2013-‐090,
hRps://cds.cern.ch/record/1595533 • Z prime: ATLAS-‐CONF-‐2013-‐066, hRps://cds.cern.ch/record/1562841 • SUSY with taus: ATLAS-‐CONF-‐2013-‐026,
hRps://cds.cern.ch/record/1525882 • Rbar: ATLAS-‐CONF-‐2012-‐032,
hRps://cds.cern.ch/record/1432198 • Tau polariza3on in W à τν events, ATLAS-‐CONF-‐2012-‐009,
hRps://cds.cern.ch/record/1428549 • Z à ττ: ATLAS-‐CONF-‐2012-‐006, hRps://cds.cern.ch/record/1426991
Complete list: hRps://twiki.cern.ch/twiki/bin/view/AtlasPublic/CONFnotes
3 July 2014 Almut Pingel (NBI) -‐ ICHEP2014 16
Physics with Taus (published) • SUSY with taus: Phys.LeR. B723 (2013) 15-‐32,
hRp://arxiv.org/abs/1212.1272 • ttbar: Eur. Phys. J. C, 73 3 (2013) 2328,
hRp://arxiv.org/pdf/1211.7205v2.pdf • Z prime: Phys. LeR. B 719 (2013) 242-‐260,
hRp://arxiv.org/abs/1210.6604 • More SUSY with taus: Eur.Phys.J. C72 (2012) 2215,
hRp://arxiv.org/abs/1210.1314 • SM Higgs: JHEP (2012) 070, hRp://arxiv.org/abs/1206.5971 • More Rbar with taus: Phys. LeR. B 717 (2012) 89-‐108,
hRp://arxiv.org/abs/1205.2067
Complete list: hRps://twiki.cern.ch/twiki/bin/view/AtlasPublic/Publica3ons
3 July 2014 Almut Pingel (NBI) -‐ ICHEP2014 17
Electron Veto
• Signal eff. (taus) vs background efficiency (electrons) • Candidates pass loose BDT tau ID and are not overlapping with 3ght electrons
3 July 2014 Almut Pingel (NBI) -‐ ICHEP2014 18
Signal efficiency0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
Back
grou
nd e
ffici
ency
-410
-310
-210
-110| < 0.80d |)0.00 | < 1.37d |)0.80 | < 1.52d |)1.37 | < 2.00d |)1.52 | < 2.47d |)2.00
ATLAS PreliminarySimulation
= 8 TeVs
TauID electron vetoWinter 2013
Muon Veto
• Cut-‐based veto • Candidates not overlapping with reconstructed muons
• Muons fake taus by failing muon reconstruc3on – Inefficient detector regions – Low momentum muons – Significant energy loss in HAD calorimeter
3 July 2014 Almut Pingel (NBI) -‐ ICHEP2014 19
EMf0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
Frac
tion
of re
cons
truct
ed ta
us0
0.020.040.060.08
0.10.120.140.160.180.2
True muonsTrue taus
ATLASPreliminary2012 Simulation
d
-2.5 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2 2.5
Frac
tion
of re
cons
truct
ed ta
us
0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
0.16
0.18
True muonsTrue taus
ATLAS Preliminary2012 Simulation
Performance Measurement: Trigger
Effic
ienc
y0
0.10.20.30.40.50.60.70.80.9
1
Data 2012 ooAMC Z
Data stat. error MC stat. error
Data sys. error
-1 L dt = 20.3 fb0 = 8 TeVs
PreliminaryATLAS
all-pronghad
oµAooAZ20 GeV tau trigger
[GeV]T
Offline tau p0 20 40 60 80 100
MC
¡/D
ata
¡
0.80.9
11.11.2
Stat. (Data)Stat. (MC)Sys.
3 July 2014 Almut Pingel (NBI) -‐ ICHEP2014 20
• Z à τμ τhad events • Efficiency wrt. offline iden3fied
taus (BDT medium) • 20 GeV tau trigger – Plateau: pT > 35 GeV
• Uncertainty: (2 – 8)%
• Combined triggers to achieve low pT thresholds – Higgs à ττ : Di-‐tau trigger – Charged Higgs: tau + ETmiss
Number of primary vertices0 5 10 15 20 25
Effic
ienc
y
0
0.2
0.4
0.6
0.8
1
L1
L1 + L2
L1 + L2 + EF
-1 L dt = 20.3 fb0 = 8 TeVs
PreliminaryATLAShad
oµAooAZ
all-prong
20 GeV tau trigger
Trigger efficiency vs nVtx and pT
Performance Measurement: Tau ID
• mT = Sqrt( 2 ·∙ pT(lep) ·∙ ETmiss ·∙ ( 1 − cos ∆φ(lep, ETmiss) ) • No addi3onal leptons in event • 42 GeV < mvis (lep, tau) < 82 GeV • cos ∆φ(lep, ETmiss) + cos ∆φ(tau, ETmiss) > −0.15 • OS charge (lep, tau) • mT < 50 GeV • ∆φ(tau, lep) > 2.4
3 July 2014 Almut Pingel (NBI) -‐ ICHEP2014 21
|d|0 0.5 1 1.5 2 2.5
Scal
e Fa
ctor
0.85
0.9
0.95
1
1.05
1.1
1.15
1.2ATLAS Preliminary
= 8 TeVs, -1 L dt = 8.5-10.5 fb0Data 2012
BDT Medium ID, Inclusive
channelhadoµoAZ channelhadoeoAZ
Combination (binned)Combination (overall)
Extended Track Mul3plicity Tracks are added to the core tracks if they sa3sfy: • 0.2 < dR(track, tau axis) < 0.6 • pT(track) > 500 MeV • pT(core track) / pT (track) ·∙ dR(core track, track) < 0.4
for at least one of the core tracks
Core tracks sa3sfy: • pT(track) > 1 GeV, dR(track, tau axis) < 0.2
General track requirements (distances wrt tau vertex): • # pixel hits ≥ 2, # pixel + SCT hits ≥ 7 • |d0| ≤ 1.0 mm (transverse distance of closest approach) • |z0 ·∙ sin θ| ≤ 1.5 mm (longitudinal distance of closest appr.) 3 July 2014 Almut Pingel (NBI) -‐ ICHEP2014 22
ATLAS detector
3 July 2014 Almut Pingel (NBI) -‐ ICHEP2014 23
ATLAS Collabora3on, The ATLAS Experiment at the CERN Large Hadron Collider, JINST 3 (2008) S08003
Outlook
Many studies ongoing: • Refine reconstruc3on of decay products (tracks, neutral
pions, tau decay substructure) • Improve energy and posi3on resolu3on • BeRer reject jets, electrons, muons • Update iden3fica3on at trigger level • Provide “con3nuous” MC/Data correc3on factors
à explore full BDT score in physics analysis (instead of pre-‐defined working points)
3 July 2014 Almut Pingel (NBI) -‐ ICHEP2014 24
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