Local Performance of the Local
Cathode Strip Chamber Trigger
in a Muon Beam Test
Overview:
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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
Ghosts
Di-muons
• Occurs when 1 muon
returns two LCT’s
•Is the converse of a
Ghost
• Considered the same
LCT if it occurs on the
same strip AND
differs by less than
two wire groups
•If two LCT’s are
found and they don’t
fit the definition of a
Ghost, then it must be
a TRUE di-muon
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