Jet EtMiss Meeting 29 th September 2009

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Nadia Davidson, Naoko Kanaya

E/p Analysis Update

Jet EtMiss Meeting29th September 2009

2

Review

E/p

Hadron track momentum

will be very accurate

p

Energy deposited

by hadrons in the

calorimeter will not

be well known in

early data.

E

∆R

The ratio E/p allows the energy reconstruction of hadrons in the calorimeters to be validated.

Tracks matched to clusters can be used to

study properties of the clusters (or sum of

clusters) close to the track. For example:

- Hadronic calibration

- Shower profiles

- Noise suppression

- pi0's associated with tracks

This can help to improve jet and tau jet

reconstruction. eg. Choice of hadronic

showering model, modifying the material

description of ATLAS

Trigger for E/p study (1)Good track selection

• Track isolation : No tracks around good track within dR=0.4• Calorimeter isolation : ∑EHCAL

dR=0.4-1.0 < 1%PTRK

Isolated track selection

• pT>500MeV• NSI ≥7• |d0|<2mm, |z0sin|<10(100) mm for physics process (singlepart)• chi2/ndof < 2.5• NTRT≥ 1 if ||<2.0

Trigger Menu• 1E31 Menu • Event rate is calculated inclusively (event weight=∑PS unless >1)• Use mibias, single,double diffractive, J0-J5, W

https://twiki.cern.ch/twiki/bin/view/Atlas/L31TriggerMenuReference (although given menu is slightly different)

Calorimeter response • Cells associated to topo clusters around track within dR<0.4• Energy summed up at EM scale

Naoko Kanaya

Trigger for E/p study (2)

menu e10_mediumMbSp(+Trk)

object rate (Hz) 7.4 (21)4.2 (8.5)

Dominant trigger menu(1E31)

Trigger bias…?We don’t have L1 track trigger.Do not use a candidate track if it matches to only one active e// trigger object in the event, dR<0.2 (except jet)…similarly to tag&prove method

Reject

Active triggerobject

Rate of isolated tracks with pT>500MeV

menu e10_medium2e5_medium

2mu4

event rate (Hz) 0.90.240.12

Rate of isolated tracks with pT>5GeV* Not unique rate, event rate is given in ()

Lepton trigger threshold

… Inclusive event rate is 150Hz in my analysis

w/o HCAL Isolation

43 HzpT>500MeV

Trigger for E/p study (3)

Rate (Hz) 1.10.70.1

Day1/=0.11.9k11020

PT distribution (remove active trigger objects)

* Assume ~flat eta distribution

- minimum bias DPD can be useful for low pT scale 10Hz x 1/50 x (1/5+4/5*0.7) -> 250 tracks/0.1/day (minbias, pT>500MeV)

- No suitable DPD for high pT isolated tracks.

Possible to run unseeded IDSCAN/isolation on Jet stream at EF?

If not…

pT>5GeV 2.9Hz1.3Hz

pT (GeV)4-77-1111-20

Situation will be worse in the presence of the pileup. Also we need quite a lot of statistics for better precision.(Quantitative study is on going…)

Matching to soletrigger objects

High pT single track?Is it possible to analyze all ESD? If so, we have enough statistics with pT<10GeV

E/p measurement in data (1)In TestBeam, study is done in only a limited region and also for pions while we need to verify E/p response in the whole region (||<2.5) and also our analysis is flavor blind (/K/P~60/30/10). Geant4 may give different performance for different primary and target (calorimeter and dead material).

<>=0.58<>=0.57<>=0.54

pT=0.5-7GeV||<2

sim14.2.10.1/reco14.2.25.8

This effect is negligible (may not be seen) at the beginning of the experiment.But the fraction may change e.g. due selection criteria, It will be checked.

E/p measurement in data (2)Not only E/p but other calorimeter response variable, such as shower shapesis also useful to validate geant4 physics list.

To avoid distortion from background:

Compute variables by subtracting/unfolding background Compute variables using cells within a limited region (one closest cluster) Use ECAL as a filter and compute variables using HCAL.

CENTER_LAMBDAin the closest cluster

MinBiasSingle pi

MinBiasSingle pi

EHAD/PTKR

(dR<0.4)

Normalized

The size of the closest cluster is not sufficiently small distorted by contamination

Small deviation is seen.Need to check…

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Energy in the Hadronic CalorimeterHad. Cal.

EM Cal.

Hadron shower

Showers from

other particles

Track momentum Track η

Red - Single PionsRed - Single Pions

Black - Min. BiasBlack - Min. Bias<E

had/p><E

had/p>

<Ehad

/p> is consistent

with the reference single pion

sample to within <0.01

(or 10%)

Can be measured in early data?

ResidualsResiduals

Non-pileup Sample

Cuts: same as slide 3

+ B layer cut

+ ptrk

/Σptrk

>0.1

- cut on E in HAD cal. 1.0-0.4

was not used

Non-pileup Sample

Cuts: same as slide 3

+ B layer cut

+ ptrk

/Σptrk

>0.1

- cut on E in HAD cal. 1.0-0.4

was not used

Nadia Davidson

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Energy Close to the Track

EM Cal.

Hadron shower

Showers from

other particles

Had. Cal.

The energy in a

narrow cone of ΔR < 0.05

Results are within about

0.02 (or 5%) of the

single pion reference

sample.

Had. Cal. Hadron shower



Black - Min. BiasBlack - Min. Bias<E

0.05/p><E

0.05/p>

Can be measured in early data?

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Total EnergyHad. Cal.

EM Cal.

Hadron shower

Showers from

other particles


Black - Min. BiasBlack - Min. Bias

Track momentum Track η E/p distribution

Approx 15% extra

energy from

contaminating

Source. Background

Is approx. flat in eta.

Large tail

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Data-driven Background Estimation Hadrons are classified as either early showering or late showering (mips) based on the

energy deposition in the hadronic calorimeter compared to the electromagnetic calorimeter (in the green core region).

The contaminating energy is measured in the electromagnetic calorimeter (blue) region for

late showering pions.

The contaminating energy distribution is unfolded from the distribution for all pions (late and

early showering)

Had Cal.

EM Cal.

core coneΔR

mip

Late showering hadronsThere is little overlap between hadron

Showers and showers of other particles

Hadron

shower

Showers

from other

particles

Early Showering hadronsThere is overlap between hadron

showers and showers of other particles

Hadron

shower

Showers from

other particles

Had Cal.

EM Cal.

Region where

background

was measured

See CSC Book

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E/p with Background Subtracted

There is systematic error in the way the background is estimated:

- Choose ΔRMIP

too small and there is pion leakage out of the cone

- Choose ΔRMIP

too large and we may miss some of the correlated background


Single PionsSingle Pions

MinBias (MinBias (ΔRΔRmipmip=0.04)=0.04)




Single PionsSingle Pions





<E/p><E/p>

The background estimate is reasonably stable with respect to the choice of narrow cone

… some work is still needed to quantify the uncertainty from this.

… MIP selection should also be varied.

MIPs selected with:

400 MeV < EEM

< 700 MeV

0.3 < EHAD

/ptrk

< 0.9

MIPs selected with:

400 MeV < EEM

< 700 MeV

0.3 < EHAD

/ptrk

< 0.9

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Distribution Recovery using Fitting

Use a predicted shape to perform a fit for the convolved E/p distribution

• Easier to estimate the statistical error

• Works better with lower statistics

• No regularisation of the noise required (so less systemic error if the

shape is well know).

E/p measured

= E/p background

* E/p isolated

Get from data

Fit a convolution:

fbackground

* fisolated

Get from data

Fit a convolution:

fbackground

* fisolated

Get from data.

Fit: fbackground

Get from data.

Fit: fbackground

Result: fisolated

Result: fisolated

Minuit was used to perform a chi2 minimisation which allows a

simultaneous fit of E/pmeasured

and E/pbackground

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Fit for Hadrons in Minimum Bias

expexp exp

free

free

exp

bifurcated

gaussian

exp

Note: Error band are approximate.

chi2/ndf=200/132chi2/ndf=200/132

pink - fit

black - data points

Black histogram – result

from iterative unfolding

(using TSpectrum::Deconvolution)

Predicted shape

6 parameters

P = 1-2 GeV, |η|<0.8

7 parameters

ResultMeasured

Background

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Fit for Single Pion Monte-Carlo

chi2/ndf=150/94chi2/ndf=150/94

ResultMeasured

Background

We need to deconvolute the noise for a fair

comparison with minimum bias hadrons (this should

not effect the mean).

Comparison of the min. bias and single pion fits will be the next step

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Conclusion/Plans There is still a lot to do:

• Study systematics of the unfolding method.

• See if fitting is a good alternative to unfolding.

• Study the possibility of a special trigger (unseeded track trigger at

EF) if ESD/DPD is not sufficient.

• See how well we can recover quantities from all cells (rather than

Topo-Clusters cells).

• Repeat with PHOJET minimum bias Monte-Carlo.

• Repeat with another hadronic showering model (eg. FTFP_BERT)

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Back-up Slides

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Selection of “good” tracks

Red – bad tracks (no matched truth particle, or a truth which comes from an ID interaction)Black – good tracks (all others)

Minimum

bias

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Result of track selection

Tracks from

minimum bias

monte-carlo

Tracks (>10 GeV)

from J0 monte-carlo

(J0 = dijets of

8-17 GeV)

Bad and “fake”

tracks are removed

before after

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Mean, sigma, prob. of no cluster

<E/p>isolated

= <E/p>measured

- <E/p>background

<E/p>isolated

= <E/p>measured

- <E/p>background

σ2isolated

= σ2measured

- σ2background

σ2isolated

= σ2measured

- σ2background

P(E/p=0)isolated

=P(0)measured

/P(0)background

P(E/p=0)isolated

=P(0)measured

/P(0)background

Not okayNot okayOkayOkay Maybe okayMaybe okay

Red-

Single Pions

Red-

Single Pions

Black -

Min. Bias

Black -

Min. Bias

Results obtained for MIP selection of EHAD

/Ptrk

> 0.3 and ΔRmip

=0.1

Residual

Value

Non pile-up

events

21

Systematics - Particle Species

Pile-up eventsConsistent within statistical precision

Documents

Jet EtMiss Meeting 29 th September 2009