z(700) data and calibration

Dijet Mass and Calibration 1

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Z(700) Data and CalibrationZ(700) Data and CalibrationZ(700) Data and CalibrationZ(700) Data and Calibration

Dan Green

Fermilab

June, 2001


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Dijet LEGO Plot - FullDijet LEGO Plot - FullDijet LEGO Plot - FullDijet LEGO Plot - Full

Z’(700) events - full LEGO plot and tracker correlation. Jet 1 is largely hadronic.


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Zoom to R = 0.5Zoom to R = 0.5Zoom to R = 0.5Zoom to R = 0.5

Structure of Jet1 in ECAL, HCAL, and tracker correlation. Attempt to resolve individual pions/photons. ECAL is very finely grained.


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Clustering in ECAL + HCALClustering in ECAL + HCALClustering in ECAL + HCALClustering in ECAL + HCAL

Start in ECAL - seed > 0.2 GeV. Add ECAL clusters for R < 0.025 (3 x 3) and ET > 0.1 GeV. Then, look in HCAL , 3 x 3 (0.125) behind. Call the result a pion interacting in ECAL (flag = 1) if HCAL energy > 0.5 x ECAL energy, else a photon (flag = 0). For HCAL seed has ET > 0.2 GeV and cluster R < 0.125 ( 3 x 3).


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# Towers in a Cluster# Towers in a Cluster# Towers in a Cluster# Towers in a Cluster

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8Towers in Cluster vs ET in ECAL

ETE(GeV)

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wer

s in

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12Towers in Cluster in HCAL vs ET

ETH(GeV)#

Tow

ers

in H

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Clu

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High ET clusters have a “large” number of towers. Low ET are limited to 1 or 2 towers in both ECAL and HCAL.


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Clusters Clusters Clusters Clusters

10-1

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10-1

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ECAL, HCAL Within a Cluster

ETE(GeV)

ETH

(GeV

)

For found clusters, if there is ECAL and HCAL energy, then ~ 1/2 is in ECAL.


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Flags of ClustersFlags of ClustersFlags of ClustersFlags of Clusters

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Cluster Flag and ET

Flag = 0 (gamma), 1 (pion in ECAL), 2 (pion in HCAL)

ETC

(GeV

)


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Zoom in R < 0.5, ClusteringZoom in R < 0.5, ClusteringZoom in R < 0.5, ClusteringZoom in R < 0.5, Clustering

Clustering is needed to correct for different calibrations which depend on the choice of photon or pion. Jet 1 is confirmed to be largely hadronic.


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Clusters in a JetClusters in a JetClusters in a JetClusters in a Jet

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40Dijet Z(700) Data

# of clusters in a Jet

A jet with R = 0.7 has ~ 200 HCAL towers. The number of clusters in the jet is <nc> = 32. The average cluster has 1.1 HCAL towers. Thus the occupation is fairly sparse.


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Missing Energy - Cluster/CalibrateMissing Energy - Cluster/CalibrateMissing Energy - Cluster/CalibrateMissing Energy - Cluster/Calibrate

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Raw Calor Data

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nd C

alib

rate

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Missing ET(GeV) for Z(700)

<ET> = 32.7 GeV --> 31.9 GeV. <Sum(ET)> = 630 GeV. Calibration using the single particle test beam procedure leads to only marginal improvement.


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Jet Seed Jet Seed Jet Seed Jet Seed

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18HCAL Seed for Jet

ETS(GeV)-4 -3 -2 -1 0 1 2 3 4 5

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20HCAL Jet Seed

ys

Look for maximum ET in HCAL. That cluster is a “seed” for the jet. Jet kinematics is defined by a cone centered on the seed as jet axis.


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Jet Finding and R ChoiceJet Finding and R ChoiceJet Finding and R ChoiceJet Finding and R Choice

0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1620

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Cone Radius

Dije

t M

ass

(GeV

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With no pileup events, a cone radius of R = 0.7 is used.


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Dijets - ET Dijets - ET Dijets - ET Dijets - ET

Use assumed calibration for ECAL and HCAL. There are some rather badly measured dijet masses. Low mass can be gluon radiation, but high mass is due to mismeasures. The kinematic maximum is M/2 of 350 GeV.

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18Jet ET, Z(700)

ET(GeV)


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Dijets - Jet Mass = 0 ?Dijets - Jet Mass = 0 ?Dijets - Jet Mass = 0 ?Dijets - Jet Mass = 0 ?

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30Dijet Z(700) Data, Jet1 Mass

MJ1(GeV)

Treat clusters as massless particles. This means that the jet has a mass.


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Dijet MassDijet MassDijet MassDijet Mass

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60Cluster and Correct - MJJ

MJJ(GeV)

<M> = 549 GeV

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40MJJ for Z(700), Cut Jet3

MJJ(GeV)

Clustered/calibrated ET of Jet 3 < 50 GeV


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Dijet Mass and Third jetDijet Mass and Third jetDijet Mass and Third jetDijet Mass and Third jet

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350Third Jet in Z(700)

MJJ(GeV)

ETJ

3(G

eV)

Third Jet is searched for and those with ETJ3 > 50 GeV are removed. This cut removes some major mismeasures of mass.


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Next StepsNext StepsNext StepsNext Steps

• Calibration does not appear to be the major cause of jet resolution.

• At high mass, the typical particle energy in a jet is still rather small.

• Magnetic field sweeping must be taken into account.

• Poor resolution at low momentum can be addressed using the tracking information.


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Track/Calor ClusterTrack/Calor ClusterTrack/Calor ClusterTrack/Calor Cluster

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1000Tracking and calorimeter Clusters (calibrated), flag > 0, |y|<3

PT(GeV)

ET(

GeV

)

Number of clusters and number of tracks are well correlated, as is the sum of PT and ET.


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Match in y, phi, ETMatch in y, phi, ETMatch in y, phi, ETMatch in y, phi, ET

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dy /0.087

dphi

/ 0

.087

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(PT-ET) / sigma(ET)

dy and dphi have peaks at 0 with widths in 0.087 units. Cut on |dy /0.087| < 1 and |dphi /0.087 < 1.5. Peak in PT-ET / 100% sqrt(PT) is evident.


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Z(700) - Track/Cal MatchZ(700) - Track/Cal MatchZ(700) - Track/Cal MatchZ(700) - Track/Cal Match

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(PT - ET) / 100% sqrt(PT)

Match simultaneously in y, phi and ET. Note that ET is systematically < PT


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Replace Clusters -> TracksReplace Clusters -> TracksReplace Clusters -> TracksReplace Clusters -> Tracks

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MJJ (Clustered)

MJJ

(Tr

ack

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Only ~ 50 tracks in |y| < 3 strike the calorimetry with PT > 1 GeV. Of those only ~ 15 match to calorimeter clusters in y, phi, and ET.


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Replace Core, R < 0.13?Replace Core, R < 0.13?Replace Core, R < 0.13?Replace Core, R < 0.13?

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MJJ(GeV)

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1000Replace flg > 0 Clusters with Tracks, R < 0.13

MJJ (clusters -> track matches)

MJJ

(clu

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cks

* co

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Core - Clusters , flg > 0Core - Clusters , flg > 0Core - Clusters , flg > 0Core - Clusters , flg > 0

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30MJJ4 - Cluster, Track Match, Core Match, ETJ3 < 50 GeV

MJJ(GeV)

z(700) data and calibration

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