Anna Kaczmarska Przegląd IFJ PAN, 6.02.09 Kraków Tau leptons as an exciting probe for New Physics...

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Anna Kaczmarska Przegląd IFJ PAN, 6.02.09 Kraków Tau leptons as an exciting Tau leptons as an exciting probe for New Physics in probe for New Physics in ATLAS ATLAS Anna Kaczmarska NZ14, Institute of Nuclear Physics PAN, Cracow 1. ATLAS experiment 2. Tau decays’ properties 3. Tau signatures of New Physics 4. Taus in Standard Model channels: Z→ττ, W→τν, ttbar 5. Conclusions Results based on Monte-Carlo simulations at 14 TeV pp centre of mass energy

Transcript of Anna Kaczmarska Przegląd IFJ PAN, 6.02.09 Kraków Tau leptons as an exciting probe for New Physics...

Page 1: Anna Kaczmarska Przegląd IFJ PAN, 6.02.09 Kraków Tau leptons as an exciting probe for New Physics in ATLAS Anna Kaczmarska NZ14, Institute of Nuclear Physics.

Anna Kaczmarska

Przegląd IFJ PAN, 6.02.09 Kraków

Tau leptons as an exciting Tau leptons as an exciting probe for New Physics in probe for New Physics in

ATLASATLAS Anna Kaczmarska NZ14, Institute of Nuclear Physics PAN, Cracow

1. ATLAS experiment2. Tau decays’ properties3. Tau signatures of New Physics4. Taus in Standard Model channels:

Z→ττ, W→τν, ttbar5. Conclusions

Results based on Monte-Carlo simulations at 14 TeV pp centre of mass energy

Page 2: Anna Kaczmarska Przegląd IFJ PAN, 6.02.09 Kraków Tau leptons as an exciting probe for New Physics in ATLAS Anna Kaczmarska NZ14, Institute of Nuclear Physics.

Anna Kaczmarska

Przegląd IFJ PAN, 6.02.09 Kraków

ATLAS (A Toroidal LHC ApparatuS)ATLAS (A Toroidal LHC ApparatuS)

Energy-scale:e/γ ~0.1%muons ~0.1%Jets ~1%

Muon Detectors: fast response for trigger, good p resolution

Electromagnetic Calorimeters: excellent e/γ identification, E and angular resolution, response uniformity

Hadron Calorimeters: Good jet and ET miss performance

Inner Detector: high efficiency tracking, good impact parameter resolution

•40MHz beam crossing•Readout: 160M channels (3000 km cables)•Raw data = 320Mbyte/sec (1TB/hour)

Page 3: Anna Kaczmarska Przegląd IFJ PAN, 6.02.09 Kraków Tau leptons as an exciting probe for New Physics in ATLAS Anna Kaczmarska NZ14, Institute of Nuclear Physics.

Anna Kaczmarska

Przegląd IFJ PAN, 6.02.09 Kraków

τ decay

π0

π+

π-

π+

τ jet

Decay modes Branching ratio

leptonic 35.2%

1-prong (τ→nπ0π±ν) 49.5%

3-prong (τ→nπ0π±ππ±ν) 14.6%

Tau hadronic decays in detector:●Decay products very collimated • Low track multiplicity • Displaced secondary vertex

Main sources of fake taus: QCD jets, electrons, muons

Tau reconstruction in ATLASTau reconstruction in ATLASIFJ PAN: Anna KaczmarskaElżbieta Richter-Wąs

Two ways for reconstruction of taus in ATLAS

Using tracks as seeds and energy from Energy Flow method (using Tracker + EM Calorimeter)

Using calorimeter clusters as seeds and energy only from calorimeters

Two ways for reconstruction of taus in ATLAS

Using tracks as seeds and energy from Energy Flow method (using Tracker + EM Calorimeter)

Using calorimeter clusters as seeds and energy only from calorimeters

Reconstruction efficiency for candidates reconstructed with both seeds (1P/3P):• τ’s in signal events ~60%• fake τ’s from QCD jets ~4-8%

Page 4: Anna Kaczmarska Przegląd IFJ PAN, 6.02.09 Kraków Tau leptons as an exciting probe for New Physics in ATLAS Anna Kaczmarska NZ14, Institute of Nuclear Physics.

Anna Kaczmarska

Przegląd IFJ PAN, 6.02.09 Kraków

Tau ID Algorithms:

Cut analysis, Projected Likelihood Probability Density Estimator with Range Searches, Neural Network, Boosted Decision Tree

Tau identification in ATLASTau identification in ATLASIFJ PAN: Marcin WolterAndrzej Zemła

Neural Network

Efficiency of tau identification

Reje

cti

on

of

fakes f

rom

QC

D jets

30%

~600

~1000

Both reconstruction algorithms provide variables discriminating between taus and fakes from QCD background

Radius of EM shower

Dedicated algorithms for rejection of fake candidates from electronsEfficiency (reco τ) = 95%Rejection (e reco as τ) = 60

+

ATLAS

Page 5: Anna Kaczmarska Przegląd IFJ PAN, 6.02.09 Kraków Tau leptons as an exciting probe for New Physics in ATLAS Anna Kaczmarska NZ14, Institute of Nuclear Physics.

Anna Kaczmarska

Przegląd IFJ PAN, 6.02.09 Kraków

Higgs and New Physics signatures with tau Higgs and New Physics signatures with tau leptonsleptons

Higgs Processes

Standard Model

VBF production, H→ττ

MSSM Higgs

bbH/A , H/A→ττ H+ in tt→H+b Wb,

gb→bH+, H+→τν

SUSY signatures with τ’s in final states

discovery

tau polarization measurement to constrain the underlying SUSY model

Extra dimensions… exotic physics…

Page 6: Anna Kaczmarska Przegląd IFJ PAN, 6.02.09 Kraków Tau leptons as an exciting probe for New Physics in ATLAS Anna Kaczmarska NZ14, Institute of Nuclear Physics.

Anna Kaczmarska

Przegląd IFJ PAN, 6.02.09 Kraków

To understand performance of complex detector

calibration, particle reconstruction algorithms, triggers… etc

To measure basic SM processes (cross-sections…) and compare them to theory and various Monte-Carlo tools

SM processes are background for New Physics

Direct sensitivity new physics (e.g. rare top decays .. )

Standard Model signatures with tau leptonsStandard Model signatures with tau leptons

Looking for New Physics is very exciting but first we have to … rediscover Standard Model

• Large statistics even with low luminosity

- analysis possible already with 100 pb-1 of integrated luminosity

• All of those channels have tau signatures: Z→ττ, W→τν, ttbar→W(τ)W(l/jj)bb

LHC will be a factory of W, Z and top

Page 7: Anna Kaczmarska Przegląd IFJ PAN, 6.02.09 Kraków Tau leptons as an exciting probe for New Physics in ATLAS Anna Kaczmarska NZ14, Institute of Nuclear Physics.

Anna Kaczmarska

Przegląd IFJ PAN, 6.02.09 Kraków

ZZ→τ→τ(lepton)(lepton)ττ(had)(had) events eventsIFJ PAN: Anna KaczmarskaElżbieta Richter-Wąs

Z→τ(e/μ)τ(had) will provide a statistically significant sample of τ leptons for 100 pb-1

measurement of the cross-section and the τ-ID efficiency

selected by lepton trigger -> unbiased sample of τ(had) decays

measurement of the τ trigger efficiencies

detector calibration: ETmiss and τ-jet energy scale determination (precision ~3%)

Expect

ed e

vents

in 1

00

pb

-

1

• Cross check between τ(e)τ(had) and τ(μ)τ(had) final states• Use of opposite-sign and same-sign e/μ-τ(had) events to control background •Dominant backgrounds

• QCD jets • We

Signal-to-background ratio 6:1 Visible mass (GeV)

Page 8: Anna Kaczmarska Przegląd IFJ PAN, 6.02.09 Kraków Tau leptons as an exciting probe for New Physics in ATLAS Anna Kaczmarska NZ14, Institute of Nuclear Physics.

Anna Kaczmarska

Przegląd IFJ PAN, 6.02.09 Kraków

WW→τν →τν eventseventsIFJ PAN: Paweł MaleckiElżbieta Richter-Wąs

The most abundant source of τ‘s in SM processes

measurement of the cross-section

branching ratios for leptonic W decays: BR(W→τν)/BR(W→eν)

ratio of the τ and electron electroweak coupling to charged current: gτ/ge

• Triggered on single tau + ETmiss

• Dominant backgrounds• QCD jets • We

•Signal purity and cross-section estimated on the basis of characteristic double peak structure in the track multiplicity distribution.

Signal-to-background ratio 3:1

Expect

ed e

vents

in 1

00

pb

-

1

Track multiplicity of tau candidates

ATLAS

Page 9: Anna Kaczmarska Przegląd IFJ PAN, 6.02.09 Kraków Tau leptons as an exciting probe for New Physics in ATLAS Anna Kaczmarska NZ14, Institute of Nuclear Physics.

Anna Kaczmarska

Przegląd IFJ PAN, 6.02.09 Kraków

Gives larger pT range of τ’s complementary to that from the W and Z processes

studies of τ trigger and tau ID efficiency

to complete the scan of the ttbar channels for cross-section measurements

to search for the effects beyond the SM in the top quark decay:

IFJ PAN: Tadeusz SzymochaInvolvement starting now

ttbar eventsttbar events

bHtRebt

btR 1),(

• ttbar→W(τν )W( qq‘ )bb channel• about 300 signal events with S:B

of 20:1 are expected for 100 pb-1

• ttbar →W(τν )W(lν)bb channel• dominated by W→lν+3jets events. • about 67 events can be observed

with S:B of 1:1 for 100 pb-1

τ t t

Page 10: Anna Kaczmarska Przegląd IFJ PAN, 6.02.09 Kraków Tau leptons as an exciting probe for New Physics in ATLAS Anna Kaczmarska NZ14, Institute of Nuclear Physics.

Anna Kaczmarska

Przegląd IFJ PAN, 6.02.09 Kraków

Events with τ’s from Standard Model will be observed with the first data of LHC

excellent possibility of understanding detector performance

Tau leptons will be the key to the Higgs and New Physics discovery:

SM Higgs, MSSM Higgs, SUSY, extra dimensions, new theories…

ATLAS group in IFJ PAN strongly involved in:

τ leptons reconstruction and identification algorithms

Standard Model physics with τ’s in final states

SummarySummary

We hope to have early measurements with tau data this year!

Important for our success are strong links with expertise of IFJ PAN Theory group (NO4), MC package Tauola for tau decays

Leading role of IFJ PAN group in preparation of 9 Internal Notes documenting expected tau performance  (2007-2008); E. Richter-Was convener of the ATLAS Tau WG in years 2007-2008

External funding:

EU Marie Curie reintegration grant 2006-2007; Polish Government grant 2007-2008 (supplement to EU MC grant); Polish Government grant N202 006434 2008-2010; IN2P3 Collaboration 08-129 IFJ PAN- LAPP Annecy

Page 11: Anna Kaczmarska Przegląd IFJ PAN, 6.02.09 Kraków Tau leptons as an exciting probe for New Physics in ATLAS Anna Kaczmarska NZ14, Institute of Nuclear Physics.

Anna Kaczmarska

Przegląd IFJ PAN, 6.02.09 Kraków

Backup Slides

Page 12: Anna Kaczmarska Przegląd IFJ PAN, 6.02.09 Kraków Tau leptons as an exciting probe for New Physics in ATLAS Anna Kaczmarska NZ14, Institute of Nuclear Physics.

Anna Kaczmarska

Przegląd IFJ PAN, 6.02.09 Kraków

Why are tau leptons so interesting?Why are tau leptons so interesting?

massive particles measurable lifetime undergo electroweak interaction only production and decay well separated in time

potential for measurement of the polarisation, spin correlations, parity

excellent knowledge about tau decay modes from low-energy experiments

however ..... several decay modes possible jet-like signature huge background from QCD multi-jet production

Make it quite difficult for being observed in the experimental environment of pp collisions at ATLAS

Ideal signature to probe “New Physics” !

Page 13: Anna Kaczmarska Przegląd IFJ PAN, 6.02.09 Kraków Tau leptons as an exciting probe for New Physics in ATLAS Anna Kaczmarska NZ14, Institute of Nuclear Physics.

Anna Kaczmarska

Przegląd IFJ PAN, 6.02.09 Kraków

The very first beam-splash event in ATLAS

13

10:19, 10th September 2008

Online displayOffline display

The LHC has been fully installed and it started operation with single beams on 10.09.08. Now it is delayed until summer 2009 after an incident that happened on 19.10.08

Page 14: Anna Kaczmarska Przegląd IFJ PAN, 6.02.09 Kraków Tau leptons as an exciting probe for New Physics in ATLAS Anna Kaczmarska NZ14, Institute of Nuclear Physics.

Anna Kaczmarska

Przegląd IFJ PAN, 6.02.09 Kraków

Page 15: Anna Kaczmarska Przegląd IFJ PAN, 6.02.09 Kraków Tau leptons as an exciting probe for New Physics in ATLAS Anna Kaczmarska NZ14, Institute of Nuclear Physics.

Anna Kaczmarska

Przegląd IFJ PAN, 6.02.09 Kraków