Commissioning with cosmic rays of the Commissioning with cosmic rays of the Commissioning with cosmic rays of the Commissioning with cosmic rays of the Commissioning with cosmic rays of the Commissioning with cosmic rays of the ALICE Muon Trigger System ALICE Muon Trigger System ALICE Muon Trigger System ALICE Muon Trigger System ALICE Muon Trigger System ALICE Muon Trigger System Claudio Geuna Journées de Rencontre Jeunes Chercheurs 2009
Commissioning with cosmic rays of the ALICE Muon Trigger System Commissioning with cosmic rays of the ALICE Muon Trigger System OUTLINE : OUTLINE : 1) Overview of the trigger system of the ALICE Muon Spectrometer. 1) Overview of the trigger system of the ALICE Muon Spectrometer. 2) Commissioning measurements and results . . 2) Commissioning measurements and results Claudio Geuna JRJC2009 Claudio Geuna JRJC2009
Commissioning with cosmic rays of the ALICE Muon Trigger System Commissioning with cosmic rays of the ALICE Muon Trigger System Alice experiment A Large Ion Collider Experiment ALICE experiment @LHC is specifically dedicated to ultra-relativistic heavy-ion collisions Claudio Geuna JRJC2009 Claudio Geuna JRJC2009
Commissioning with cosmic rays of the ALICE Muon Trigger System Commissioning with cosmic rays of the ALICE Muon Trigger System The Muon Spectrometer (I) Forward muon Forward muon spectrometer spectrometer Angular acceptance Angular acceptance 2 0 < θ <9 0 2 0 < θ <9 0 Pseudorapidity -4 < η < -2.5 study of the production study of the production of open heavy flavour of open heavy flavour and heavy quarkonia and heavy quarkonia (J/ Ψ and ϒ ) through (J/ Ψ and ϒ ) through the muon ( µ ) decay channel the muon ( µ ) decay channel Claudio Geuna JRJC2009 Claudio Geuna JRJC2009
Commissioning with cosmic rays of the ALICE Muon Trigger System Commissioning with cosmic rays of the ALICE Muon Trigger System The Muon Spectrometer (II) Interaction Dipole vertex Absorber Magnet the components components the Muon filter Trigger chambers 5 m 5 m 0 0 0 0 20 m 20 m Tracking chambers Claudio Geuna JRJC2009 Claudio Geuna JRJC2009
Commissioning with cosmic rays of the ALICE Muon Trigger System Commissioning with cosmic rays of the ALICE Muon Trigger System The trigger system: Muon Trigger Chambers 2 trigger stations ( MT1 and MT2 ) located at about 16 m from the IP and 1 m apart from each other placed behind an iron muon filter Layout of the trigger stations and the iron wall installed in the Alice cavern. Claudio Geuna JRJC2009 Claudio Geuna JRJC2009
Commissioning with cosmic rays of the ALICE Muon Trigger System Commissioning with cosmic rays of the ALICE Muon Trigger System The trigger system: Muon Trigger Chambers 2 stations , of two planes each total area: ~ 140 m 2 ~ 6.5 m 72 RPCs of 3 different shapes and dimensions : ~1.6 m 2 ÷ 2.1 m 2 20992 strips and front- end channels ~ strip pitch: 5 . 5 10-45 mm(~1/2/4 cm) m strip length: 170÷720 mm Claudio Geuna JRJC2009 Claudio Geuna JRJC2009
Commissioning with cosmic rays of the ALICE Muon Trigger System Commissioning with cosmic rays of the ALICE Muon Trigger System The principle of the trigger (I) GOAL : GOAL : • Selection of (muon) tracks pointing to I.P. Selection of (muon) tracks pointing to I.P. with p with p t above 2 thresholds: t above 2 thresholds: low p low p t cut = 1 GeV/c t cut = 1 GeV/c high p high p t cut = 2 GeV/c t cut = 2 GeV/c Trigger signals for Trigger signals for • single single µ , like-sign and unlike-sign µ pairs µ , like-sign and unlike-sign µ pairs PRINCIPLE: PRINCIPLE: cut on deviation between MT1and MT2 • cut on p cut on p t t cut on deviation between MT1and MT2 select tracks in a road of a given width select tracks in a road of a given width Claudio Geuna JRJC2009 Claudio Geuna JRJC2009
Commissioning with cosmic rays of the ALICE Muon Trigger System Commissioning with cosmic rays of the ALICE Muon Trigger System The principle of the trigger (II) GOAL: GOAL: • Selection of (muon) tracks pointing to I.P. Selection of (muon) tracks pointing to I.P. with p with p t above 2 thresholds: t above 2 thresholds: low p low p t t cut cut = 1 GeV/c = 1 GeV/c high p high p t t cut cut = 2 GeV/c = 2 GeV/c Trigger signals for Trigger signals for • single single µ µ , like-sign and unlike-sign , like-sign and unlike-sign µ µ pairs pairs PRINCIPLE : PRINCIPLE : cut on • cut on p cut on p t t cut on deviation between MT1and deviation between MT1and MT2 MT2 select tracks in a road of select tracks in a road of a given width a given width Dipole Dipole Magnet Magnet integral magnetic field of 3 Tm Claudio Geuna JRJC2009 Claudio Geuna JRJC2009
Commissioning with cosmic rays of the ALICE Muon Trigger System Commissioning with cosmic rays of the ALICE Muon Trigger System Resistive Plate Chambers (I) A Resistive Plate Chamber Resistive Plate Chamber (RPC) is a planar geometry gaseous detector (RPC) is a planar geometry gaseous detector A Claudio Geuna JRJC2009 Claudio Geuna JRJC2009
Commissioning with cosmic rays of the ALICE Muon Trigger System Commissioning with cosmic rays of the ALICE Muon Trigger System Resistive Plate Chambers (II) Gas mixtures: avalanche vs streamer The difference between the streamer and avalanche modes lies in the gas mixture (quenchers ) and HV applied between the two electrodes. Main advantages of streamer and avalanche RPC operation Operation mode Advantages Operation mode Advantages Streamer Spatial resolution Streamer Spatial resolution No amplification needed No amplification needed Lower noise rate Lower noise rate Avalanche Time resolution Avalanche Time resolution Rate capability Rate capability ALICE MuonTrigger RPCs ALICE MuonTrigger RPCs Slower ageing Slower ageing Typical avalanche operation voltages ~ 10 kV Typical streamer operation voltages ~ 8 kV Claudio Geuna JRJC2009 Claudio Geuna JRJC2009
Commissioning with cosmic rays of the ALICE Muon Trigger System Commissioning with cosmic rays of the ALICE Muon Trigger System Resistive Plate Chambers (III) ALICE : both A-A and p-p data-taking Requirements for A-A data taking: • Spatial resolution 1 cm • Occupancy as low as possible (few % Pb-Pb) and cluster-size as close as possible to 1 • Rate capability 3 Hz/cm 2 (Pb-Pb) and 25 Hz/cm 2 (Ar-Ar) • Time resolution 2 ns Requirements for p-p data taking: • Expected muon trigger rate much lower than in A-A collisions • Rate capability 100 Hz/cm 2 • Goal: detector lifetime Claudio Geuna JRJC2009 Claudio Geuna JRJC2009
Commissioning with cosmic rays of the ALICE Muon Trigger System Commissioning with cosmic rays of the ALICE Muon Trigger System Resistive Plate Chambers (IV) RPC performances Low resistivity bakelite: Rate capability up to 100 Hz/cm 2 (p-p) ρ = 2÷8 10 9 Ω cm Dual threshold Time resolution 2 ns Front End Electronics 10 mV - 80 mV Claudio Geuna JRJC2009 Claudio Geuna JRJC2009
Commissioning with cosmic rays of the ALICE Muon Trigger System Commissioning with cosmic rays of the ALICE Muon Trigger System Resistive Plate Chambers (IV) RPC performances Low resistivity bakelite: Rate capability up to 100 Hz/cm 2 (p-p) ρ = 2÷8 10 9 Ω cm Dual threshold Time resolution 2 ns Front End Electronics 10 mV - 80 mV Requirements for A-A data taking: Spatial resolution 1 cm Occupancy as low as possible (< % Pb-Pb) and cluster-size as close as possible to 1 Streamer mode Claudio Geuna JRJC2009 Claudio Geuna JRJC2009
Commissioning with cosmic rays of the ALICE Muon Trigger System Commissioning with cosmic rays of the ALICE Muon Trigger System Resistive Plate Chambers (IV) RPC performances Low resistivity bakelite: Rate capability up to 100 Hz/cm 2 (p-p) ρ = 2÷8 10 9 Ω cm Dual threshold Time resolution 2 ns Front End Electronics 10 mV - 80 mV Requirements for A-A data taking: Requirements for p-p data taking: Spatial resolution 1 cm Expected muon trigger rate much lower than in A-A Occupancy as low as collisions possible (< % Pb-Pb) and cluster-size as close as Goal: detector lifetime possible to 1 Streamer mode “Highly saturated” avalanche mode Claudio Geuna JRJC2009 Claudio Geuna JRJC2009
Commissioning with cosmic rays of the ALICE Muon Trigger System Commissioning with cosmic rays of the ALICE Muon Trigger System Resistive Plate Chambers (V) The two gas mixtures in detail..... Claudio Geuna JRJC2009 Claudio Geuna JRJC2009
Commissioning with cosmic rays of the ALICE Muon Trigger System Commissioning with cosmic rays of the ALICE Muon Trigger System OUTLINE : OUTLINE : 1) Overview of the trigger system of the ALICE Muon Spectrometer 1) Overview of the trigger system of the ALICE Muon Spectrometer 2) Commissioning measurements and results 2) Commissioning measurements and results Claudio Geuna JRJC2009 Claudio Geuna JRJC2009
Commissioning with cosmic rays of the ALICE Muon Trigger System Commissioning with cosmic rays of the ALICE Muon Trigger System Muon Spectrometer commissioning with cosmic rays: goals - Global test of the Muon Spectrometer Claudio Geuna JRJC2009 Claudio Geuna JRJC2009
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