The CMS Muon Detector Thomas Hebbeker Aachen July 2001 Searching for New Physics with High Energy...
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Transcript of The CMS Muon Detector Thomas Hebbeker Aachen July 2001 Searching for New Physics with High Energy...
The CMS Muon Detector
Thomas HebbekerAachen July 2001
Searching for New Physics with High Energy Muons
Outline
• LHC and CMS
• energy, luminosity, background
• discoveries with muons
• muons in CMS
• detectors for muons
• Aachen muon project
LHC at CERN
Large
Hadron
Collider
27 km circumference
14 TeV c.m.e. (p p)
1200 TeV (Pb Pb)
p + p A + A
no antiparticles !
p p
Center of Mass Energy
Relevant:center of mass energy of colliding constituents (q, g)
Required:
capability to produce new particles with masses up to 1 TeV !
s
p p
gluon
quark
Rough estimate:
Need:
ss 3
1
2
1
TeVTeVs 14126
s
Cross Section and Luminosity
Total inelastic cross section
LN
Event rate
Pointlike cross section
p
p2252 1010 cmfm
2362
10 cms
BACKGROUND
SIGNAL
strong
electroweak
scmL //10 234 huge background !
particles /s1110100 particles /collision
> 1/hour
CMS
Compact
Muon
Solenoid
diameter = 22 m 15 m
weight = 14500 t
Excellent signaturefor new physics
magnet type
length = 42 m 22 m
B
Muon
Discovery: 1933 (Kunze), 1937 (Anderson, Neddermeyer)
s = ½
m = 0.106 GeV
= 2.20 s
Decay length:
L = c ~ E/m c E = 1 TeV:
L ~ 6000 km „stable“
ee
ee
Rabi: „Who ordered that ?“
e m600
Muons and Discoveries - Examples
Tau Lepton:
Bottom
quark:
seee '
SLAC 1975
Martin Perl et al.
Fermilab
1977
Leon
Lederman
et al.
Ap
bb
9.5 GeV
Upsilon
New Physics at the LHC ?
Supersymmetric Particles:
Chargino :
(partner of W)
Neutralino :
(partner of Z,)
Smuon :
(partner of muon)
Hadron Colliders and Muons
Background (frequent):
strong interaction
-> quarks, gluons
( LHC: ~ 20 p – p collision events per bunch crossing )
Interesting events (rare):
electroweak processes,
decays of heavy particles
-> Leptons
Hadron Colliders and Muons
one bunch crossing
(= 20 events superimposed):
inside detector
high energy
high energy
B
abso
rber
Muon Properties NO strong interaction
electromagnetic interaction:
• NO (little) radiation
• ionisation
long lifetime
GeVm 106.0
energy loss negligible if
m large
decay length exceeds 100 m if
m small
e
no good
no g
ood
weak interaction
muon mass
The Central CMS Muon Chambers
muon
2 m
30 c
m
2 x 4 layers
„bending“
4 layers
„nonbending“drift cell
honeycomb layer
The Drift Cell
drift region
v = 5.7 cm / s ~ constE ~ 2 kV/cm ~ const
amplification
E ~ 1/r -> 150 kV /cm
distance = time/v
m 250~
2.5m
distance+3600
V+1800 V
-1800 V 5
0 e
510~A
50m
Q ~ 500 fC -> amplifier
(Transverse) Momentum Measurement
B field + coordinate measurements + vertex
constraint: TeV
p
p
p
%20
multiple scattering (iron,calorimeters):
muon detector alone:
%8
3.5
m
precision m100
iron, B
T5.1
vertex (interaction point)
m20
0
Outlook
• Muon chamber production:
– started 2001,– first chambers will be installed in 2002
• LHC and CMS will start data taking in 2006
... Higgs ...
... chargino ... stop ... smuon...
... ...
... extra dimensions ...
... tohu ... vabohu..
... gravitons ...
? ?
Muons and CMS
• muons from new particles
• muons from W decays
• muons from bottom decays
• low energy hadron decay products
• cosmic muons
collision rate: 40 MHz
100 Hz
100 kHz
> 1 MHz
10 kHz
transverse momenta > 3 GeV: << 1 Hz ?
TRIGGER: transverse momenta > 20 GeV:
1 kHz
Background (central detector):
hadron „punchthrough“
neutron induced )( * eAAn
2/10 cmHz