Local Performance of the Local Cathode Strip Chamber Trigger in a Muon Beam Test

Local Performance of the Local Cathode Strip Chamber Trigger

in a Muon Beam Test

Overview:

• Introduction to LHC

• Overview of CMS

• Overview of Trigger Architecture

• Overview of Cathode Strip Chamber (CSC)

• Level-1 Trigger System

• Plots for efficiency

• Conclusion

LHC

• 14 TeV center of mass energy• 27 km circumference

CMS (Compact Muon Solenoid)

CMS

What is a muon?

Muons are point particles identical to electrons except over 200 times more massive (105.2 MeV)

The illustration shows the smaller orbit for muons in a hydrogynic atom due to their mass

CMS

Why Muons?

•Muons are penetrating.

•Electrons are too light to make it through absorbers

•Taus are too unstable to make it through absorbers

•Hadrons interact strongly with matter

Trigger Architecture

• Need Trigger System to filter out data

Cathode Strip Chambers (CSC)

• Provide 3-D tracks of charged particles called Local Charge Tracks (LCT’s)

Level-1 Trigger System

Level-1 Trigger System

• ALCT and CLCT find 2-D tracks

• TMB receives and correlates these tracks to make a 3-D Correlated LCT

• MPC receives up to 18 LCT’s from the different TMB’s and selects the best 3

• SR/SP receives the 3 LCT’s from the TMB

2004 Test Beam

• 100GeV muons for asynchronous run

• 100GeV pions for synchronous run (along with muons)

ALCT Trigger Modes• Trigger Mode 0:

Accelerator Pattern or Collision Pattern

• Trigger Mode 1: Acc. Pattern Only

• Trigger Mode 2: Collision Pattern Only

• Trigger Mode 3: Acc. Or Coll. But Acc. Pattern vetoes Coll.

Coll. Pattern Acc. Pattern

Ghosts and Di-Muons

• Occurs when 1 muon returns two LCT’s

• Considered the same LCT if it occurs on the same strip AND differs by less than two wire groups

Ghosts

•Is the converse of a Ghost

•If two LCT’s are found and they don’t fit the definition of a Ghost, then it must be a TRUE di-muon

Di-muons

Ghost and Di-Muon Rates

Ghost Rates Di-muons Rates

Angle vs. ALCT Trigger Mode

Different Collision Patterns

Coll. Pattern vs. ALCT Trigger Mode

Number of Layers Required?

There Are six possible layers

We can require any number of those six; the default is 4 out of six

This means that if any 4 of those layers matches then it is an LCT

Minimum Number of Layers Required vs. ALCT Trigger Mode (for “Miss4” Pattern)

Ghost Rates for Miss4 Coll. Pattern

Conclusions

• Miss4 has high efficiency and provides very good discrimination against collision vs. accelerator patterns

• Other parameters varied: ALCT delay, with and without an iron block, old and new ALCT firmware