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The CMS Muon Detector

The CMS Muon Detector. Searching for New Physics with High Energy Muons. Thomas Hebbeker Aachen July 2001. Outline. LHC and CMS energy, luminosity, background discoveries with muons muons in CMS detectors for muons Aachen muon project. LHC at CERN. 27 km circumference.

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The CMS Muon Detector

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  1. The CMS Muon Detector Searching for New Physics with High Energy Muons Thomas Hebbeker Aachen July 2001

  2. Outline • LHC and CMS • energy, luminosity, background • discoveries with muons • muons in CMS • detectors for muons • Aachen muon project

  3. LHC at CERN 27 km circumference 14 TeV c.m.e. (p p) 1200 TeV (Pb Pb) Large Hadron Collider p + p A + A no antiparticles ! p p

  4. LHC

  5. LHC superconducting magnets 8.3 T 1.9 K 14.3 m 1232 x

  6. Center of Mass Energy Required: capability to producenew particleswith masses up to 1 TeV ! gluon p p quark Relevant: center of mass energy of colliding constituents (q, g) Rough estimate: Need:

  7. Cross Section and Luminosity Event rate > 1/hour strong p Total inelastic cross section BACKGROUND p electroweak SIGNAL Pointlike cross section huge background ! particles /s 100 particles /collision

  8. Cross Sections at Hadron Colliders

  9. CMS Compact Muon Solenoid diameter = 22 m 15 m length = 42 m 22 m weight = 14500 t Excellent signature for new physics B magnet type

  10. CMS Detector

  11. Muon s = ½ m = 0.106 GeV t = 2.20 ms Discovery: 1933 (Kunze), 1937 (Anderson, Neddermeyer) Rabi: „Who ordered that ?“ L =b g ct~ E/m ct Decay length: „stable“ E = 1 TeV: L ~ 6000 km

  12. Cosmic Rays = Atmospheric Muons = 0.5 mSv = 50 mrem

  13. Muons and Discoveries - Examples Bottom quark: Tau Lepton: SLAC 1975 Martin Perl et al. Upsilon 9.5 GeV Fermilab 1977 Leon Lederman et al.

  14. New Physics at the LHC ? Higgs boson:

  15. New Physics at the LHC ? Supersymmetric Particles: Chargino : (partner of W) Neutralino : (partner of Z, g) Smuon : (partner of muon)

  16. 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

  17. Hadron Colliders and Muons high energy one bunch crossing (= 20 events superimposed): absorber high energy B inside detector

  18. Particle Detection

  19. Muon Properties muon mass • NO strong interaction • electromagnetic interaction: • NO (little) radiation • ionisation • long lifetime energy loss negligible if large no good weak interaction decay length exceeds 100 m if no good small

  20. Higgs event in CMS tracker

  21. Higgs event in CMS tracker

  22. Higgs event in CMS tracker

  23. Higgs event in CMS tracker

  24. Higgs event in CMS

  25. Higgs event in CMS

  26. The CMS Muon Detector

  27. The Central CMS Muon Detector

  28. The CMS magnet m yoke B = 1.5T yoke yoke yoke superconducting coil yoke B = 4 T m

  29. The Central CMS Muon Chambers honeycomb layer muon 2 m 30 cm 2 x 4 layers „bending“ 4 layers „nonbending“ drift cell

  30. The Drift Cell 2.5m distance +3600 V +1800 V 50mm 50 e -1800 V drift region amplification E ~ 2 kV/cm ~ const E ~ 1/r -> 150 kV /cm v = 5.7 cm / ms ~ const distance = time/v Q ~ 500 fC -> amplifier

  31. (Transverse) Momentum Measurement muon detector alone: precision 3.5 m iron, B vertex (interaction point) B field + coordinate measurements + vertex constraint: multiple scattering (iron,calorimeters):

  32. CMS Muon (transv.) Momentum Resolution

  33. Chamber Production in Aachen

  34. Chamber Production Experts

  35. Chamber Gluing

  36. Layer with I-Beams, Wires and End Pieces 4 cm

  37. Measurement of Wire Position CCD camera resolution = few microns

  38. Determination of Wire Tension (3 N)

  39. Yoke: Installation of first wheel

  40. 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... ... jnsmsoiu... ... extra dimensions ... ... tohu ... vabohu.. ... gravitons ... ? ?

  41. Muons and CMS collision rate: 40 MHz transverse momenta > 3 GeV: • muons from new particles • muons from W decays • muons from bottom decays • low energy hadron decay products • cosmic muons << 1 Hz ? 100 Hz 100 kHz > 1 MHz 10 kHz TRIGGER: transverse momenta > 20 GeV: 1 kHz Background (central detector): hadron „punchthrough“ neutron induced

  42. Electron Drift in Gas typical values: l = 3 mm t = 30 ps E = 1 kV/cm v = 5 cm/ms

  43. Avalanche in Wire Chamber d = 50 mm E ~ 1/r avalanche very close to wire

  44. Muon mean timer

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