TeV Muons Status Report

Dimitri BourilkovUniversity of Florida

CMS PRS/ Meeting, June 7, 2005, CERN

D.Bourilkov TeV Muons 2

Introduction

• Goal of the study: understand quantitatively the physics of TeV muons - why (and to what extent) are they special

• At UF we have seven samples of Z’ -> μ+μ- with masses 0.2, 0.5, 1.0, 1.5, 3.0, 4.0, 5.0 TeV generated to study TeV muons and the mass resolution (41500 events)

• CMKIN_4_0_0, OSCAR_3_6_3, ORCA_8_7_1 used to produce digis and DST; filter after CMKIN to retain only muons and Final State Radiation

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Study of Material Effects

• Collect energy deposits along the muon trajectories by matching objects in a rapidity-phi cone around the tracks

• ECAL clusters: EGClus_E5x5

• Jets: JetIC5A_E (ECAL+HCAL deposits)

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Energy Loss in ECAL - Flat

<p> = 415 GeV <p> = 2569 GeV

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Energy Loss in ECAL+HCAL – Slowly Rising

<p> = 415 GeV <p> = 2569 GeV

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Energy Losses

<p>

[GeV]

<EECAL>

[GeV]

% of tracks

% > 20 GeV

<EJET>

[GeV]

% of tracks

% > 50 GeV

185.2 19.75 0.50 0.14 18.95 9.7 0.44

414.8 19.39 1.4 0.40 25.73 16.0 1.4

711.5 21.45 2.5 0.74 29.67 25.9 2.4

955.2 16.06 4.5 1.1 36.18 34.7 3.6

1659. 21.53 8.6 1.8 36.05 52.7 6.8

2109. 16.77 11.3 2.6 40.36 58.3 10.1

2569. 19.31 13.0 3.4 41.65 66.0 12.9

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Muon Reconstruction

• Compare info from different muon objects by reconstructing the Z’ mass in different ways

• Start with the global muon reconstructor MuonGLB_…

• Saw some problems: tried taking the muon momentum from MuonGLB_out, eta and phi at the vertex

• Added the jet energy to the muon momentum to compensate for the energy loss

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Mass Resolution @ 500 GeV

GLB

GLB_outGLB_out

+ JetCOR

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Mass Resolution @ 5000 GeV

GLB

GLB_out GLB_out

+ JetCOR

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Comparison of Reconstructors

Generated mass

[GeV]

(Rec – Gen)GLB

[GeV]

(Rec – Gen) GLB_out

[GeV]

(Rec – Gen)GLB_out + JetCOR[GeV]

201.7 +- 10.7 0.58 +- 4.96 -6.8 +- 5.01 -3.9 +- 8.04

502.2 +- 21.2 1.05 +- 19.3 -6.3 +- 17.9 -0.4 +- 21.3

1002. +- 28.8 -0.81 +- 49.1 -8.2 +- 47.9 3.8 +- 51.1

1501. +- 35.2 -5.8 +- 86.4 -9.8 +- 80.1 10.0 +- 86.2

2999. +- 44.2 -21.0 +- 208. -17.0 +- 179.9 18.6 +- 183.6

3998. +- 47.9 -38.9 +- 300.3 -27.9 +- 236.1 19.6 +- 245.3

4999. +- 49.8 -48.3 +- 400.4 -33.2 +- 328.1 20.0 +- 334.7

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Some Observations

• The jet energy correction is overcorrecting the muon momenta – is this connected to the correction coming mostly from HCAL and from electromagnetic showers?

• The global muon reconstructor is less performant for TeV muon momenta – is this coming from the tracker? Will be investigated next

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Outlook

• Energy losses are flat with muon momentum in the ECAL, slowly rising in the HCAL; in first order their size depends on the material budget, only weakly on the muon momentum

• The frequency of energy losses rises with muon momentum, so we have two competing effects: the losses occur more often, but their impact (as % of the muon energy) is going down

• The global muon reconstructor shows problems for muon momenta >~ 1 TeV (are they coming from tracker?)

• Here a combination of the muon momentum at the edge of the muon chambers with the angles at origin works better ?!

• Adding the jet energy helps to some extent to cure the energy loss (actually overcorrecting the effect); the price to pay is a small deterioration of the mass resolution