1. May 2006 Hadronic Calibration Workshop Jet Session at Munich
Jet Energy Calibration Using E/p of Single Charge Isolated Hadrons from Tau Decay
J. Lu, D. M. Gingrich
University of Alberta
May 2006 Hadronic Calibration Workshop Jet Session at Munich
04/19/2006

2. Outline General Introduction: The single charged isolated
hadrons from tau (W) decay: E/p=1. The precise measurement of their momentum (precision 0.5%) in the inner detector can be used to calibrate the energy measured in the calorimeters (precision 5-10%). Main issue is how to separate π+ and π+ π0 (ρ0) from tau decay. QCD background and Minimum bias events will affect E/p calibration.
Data sample and event selections.
Some results and outlook.
04/19/2006

3. Data sample TAUOLA BR (%) τ±→e±υeυτ 18.1 τ±→μ±υμυτ 17.6 τ±→π±υτ 11.1%
Sample 1: Rome MC production: 4807 (sample A3), inclusive Z to tau tau tight filtered. 49K AOD
/castor/cern.ch/grid/atlas/datafiles/rome/recov10/rome recov10.A3_Ztautau_tightfilter
Sample 2: Rome MC production: 4124, 88.2 K AOD events (Z +jet, Z to tautau)
/castor/cern.ch/grid/atlas/datafiles/rome/recov10NONT/rome recov10NONT.Sherpa_ZJ1tautau
Sample 3: Run 4801 filtered, 50K (Z)
pp →Z+ x and pp →Z+jet+X combined in the same luminosity
Atlas release
TAUOLA
BR (%)
τ±→e±υeυτ
18.1
τ±→μ±υμυτ
17.6
τ±→π±υτ
11.1%
τ±→K±υτ
0.7%
τ±→ρ±υτ with ρ→ π± π0
24.2%
τ±→a1±υτ
with a1±→ π± π±/0 π-/+/0
13.0
τ±→K*±υτ
1.3
τ±→(mπ±+n π0) υτ
5.6
04/19/2006

4. Z to tautau, tau to single charge hadron event selection
Trigger satisfy one of the following:
Tau jet with ETmiss>30 GeV
one lepton with PT>20 GeV, ETmiss>20 GeV
ETmiss<1000 GeV
Only one charge track in Tau Jet from AOD container
PT>20 GeV, |η| < 2.5, ETmiss>10 GeV for electron trigger
Tau likelihood greater than 4.
ΔR between tau jet and electron >0.4, energy deposition in hadronic calorimeter >1GeV
ΔR between tau jet and photon >0.4
Energy calibration factor in Rome should be multiplied by a factor of 1.08
04/19/2006

5. E/P ratio without π0 separation
Fit in the range
Mean: 1.079±0.008, σ: 0.172±0.008
Fit in the range
Mean: 1.010±0.010, σ: 0.093±0.012
1. Nucleon is a spin half particle, whose spin receives
contribution from quark and orbital angular momentum.
2. HERMES studys nuclear spin structure by DIS, i.e deep
inelastic scattering of electron or positron beam scattering
from nuclear targets, which means exchange virtual photon has sufficient virtuallity Q2 to resolve the individual quark
Q2>1
3. By using polarized beam, the interaction is ssensitive to the orientation of quark and nuclear spin, because quark can observe the virtual photon only if the quark spin is opposite the quark spin, because the hard interation conerve helicity.
4. Using this technique, it was found quark spin contribution Delta Sigma is small, leaving large room of contribution from gluon and orbital angular momentum
Nucleon spin puzzle
6.(point to DVCS plot: two hard scattering vertex, the nuclear stays intact in the ground state)
5. The recent theretical development of GPDs (two quark correltion function) may help us Lq, while the DVCS
can access GPDs.
Large E/p tail, mean E/p depends on the fit region
(Gaussian plus third-order polynomial fit)
04/19/2006

6. Calibration without π0 separation
If in the first month LHC running we collect 100 fb-1, around 2000 tau jet events passing E/p event selections without π0 separation . The statistics uncertainty for E/p mean is around Statistics is not enough for further π0 separation.
It is possible to calibrate to E/p bias without π0 separation. E/p bias induced by π0 is (1±1)%
by only fit in the narrow region around peak.
E/p bias induced by QCD background and pile up is small, less than 1%.
These conclusions will be cross-checked by CSC samples.
04/19/2006

7. Ratio of energy deposited in EM calo and hadronic calo ----- for π0 separation
Same total entries
Good separation of h± and h±+nπ0 for EM/Had<0.05. Try other variables to separate h± and
h±+nπ0 for EM/Had>0.05
EM/Hadronic
<0.02
<0.03
<0.05
<0.1
<0.2
Eff (e2, %) h+
4.68
7.16
10.46
17.08
21.76
Eff(e1, %) h+ + nπ0
0.15
0.29
2.06
7.64
e1/e2
0.021
0.028
0.12
0.35
1. Nucleon is a spin half particle, whose spin receives
contribution from quark and orbital angular momentum.
2. HERMES studys nuclear spin structure by DIS, i.e deep
inelastic scattering of electron or positron beam scattering
from nuclear targets, which means exchange virtual photon has sufficient virtuallity Q2 to resolve the individual quark
Q2>1
3. By using polarized beam, the interaction is ssensitive to the orientation of quark and nuclear spin, because quark can observe the virtual photon only if the quark spin is opposite the quark spin, because the hard interation conerve helicity.
4. Using this technique, it was found quark spin contribution Delta Sigma is small, leaving large room of contribution from gluon and orbital angular momentum
Nucleon spin puzzle
6.(point to DVCS plot: two hard scattering vertex, the nuclear stays intact in the ground state)
5. The recent theretical development of GPDs (two quark correltion function) may help us Lq, while the DVCS
can access GPDs.
04/19/2006

8. Variables to separate τ→h±υ and τ→(h±+ nπ0)υ
EM/Had >0.05
Width of energy deposition in strips >0.005
Fraction of energy deposited in ΔR ( ) >0.08
EM radius of τ > 0.07
After this 3 variables cuts: efficiency h±: 12.0%,
h± +nπ0: 4.7%, not strong separation
Another variable: the number of strips in the strip layer of the EM calo
with energy deposition above a threshold. But not in the “TauJetCollection” AOD container.
04/19/2006

9. E/P ratio with π0 separation
EM/Had>0.05 and other 3 variable cuts
Mean: 1.030±0.020, σ: 0.044±0.027
EM/Had<0.05 is applied
Mean: 1.012±0.019,
σ: 0.023±0.024
1. Nucleon is a spin half particle, whose spin receives
contribution from quark and orbital angular momentum.
2. HERMES studys nuclear spin structure by DIS, i.e deep
inelastic scattering of electron or positron beam scattering
from nuclear targets, which means exchange virtual photon has sufficient virtuallity Q2 to resolve the individual quark
Q2>1
3. By using polarized beam, the interaction is ssensitive to the orientation of quark and nuclear spin, because quark can observe the virtual photon only if the quark spin is opposite the quark spin, because the hard interation conerve helicity.
4. Using this technique, it was found quark spin contribution Delta Sigma is small, leaving large room of contribution from gluon and orbital angular momentum
Nucleon spin puzzle
6.(point to DVCS plot: two hard scattering vertex, the nuclear stays intact in the ground state)
5. The recent theretical development of GPDs (two quark correltion function) may help us Lq, while the DVCS
can access GPDs.
Gaussian plus third-order polynomial fit
04/19/2006

10. Calibration with π0 separation
Using ratio of energy deposition in EM calorimeter and hadronic calorimeter <0.05 can greatly reduce π0 contamination, the lower the cut, the better. In this case, the hadronic calorimeter can be calibrated.
If in the first month LHC running we collect 1 fb-1, around 1000 tau jet events passing E/p event selections without π0 separation . The statistics uncertainty for E/p mean is around The long tail from π0 contribution is highly reduced.
E/p bias induced by QCD background, π0 and pile up is around (2±2)%.
These conclusions will be cross-checked by CSC samples.
A note using Rome sample: ATL-COM-PHYS
Another ATLAS note with CSC sample will be produced.
04/19/2006