IJAZ AHMEDNational Centre for Physics1

IJAZ AHMEDNational Centre for Physics2 OUTLINES oLHC parametres oRPCs oOverview of muon trigger system oIdea of Muon trigger oRequirements of muon trigger oSource of muons oTriggering objects

IJAZ AHMEDNational Centre for Physics3 # of Interactions/ crossing  Cross-section of P-P collision σ(pp) = 70 mb  Luminosity=10**34 /cm**2*sec  Interactions rate = 40MHz Events / beam crossing  Time interval b/w each bunch crossing=25ns  Interactions per crossing =1 7.5  # of P-P bunches = 2835 out of 3564  Interactions / active crossing = 20x2835/3564=23

IJAZ AHMEDNational Centre for Physics4  Bakelite electrodes with ρ~10**10 Ω.cm  Gap width ~ 2mm  N = N o exp(ηd)  hd < 20 (Avalanche mode )  N/N o < 10**8  = (k/ηd ) =q el n o k/(ηd)λ/(η+ λ)exp(ηd)  1656 RPCs = 4000 m**2 Resistive Plate Chamber (RPC)

IJAZ AHMEDNational Centre for Physics5 Physics behind RPC  Gaseous Detector Efficiency > 98% Time Resolution < 2ns Rate capability >1 KHz/cm2 Power Consumption <2-3 W/m² Operating Plateau > 300 V Streamer probability < 10% Cluster size < 2 strips Low ionization potential gas mixture

IJAZ AHMEDNational Centre for Physics6 Transverse view of CMS Detector

IJAZ AHMEDNational Centre for Physics7 Requirements from Muon Trigger  Geometrical coverage, |η|=2.4  Latency<3.2 μs  Max. out put rate <15KHz  B.g should not exceed rate of prompt muons  4 highest Pt muons from each event  B.G rate < Prompt muon rate  Dead time: not allowed

IJAZ AHMEDNational Centre for Physics8 Physics goals  Inclusive single muon trigger |η|=<2, Pt cut ~ GeV  Inclusive double muon Trigger |η|=<2, Pt cut ~10 GeV  Triple muon trigger |η|=<2, Pt cut ~4 GeV

IJAZ AHMEDNational Centre for Physics9 Muon Trigger Components  PACT (Pattern comparator trigger)  RPC (Resistive plate chamber)  CSC (Cathode strip chamber)  DT (Drift tubes)  Track finder  Muon sorter  Global muon trigger

IJAZ AHMEDNational Centre for Physics10 Trigger Objects  Electron/photon  Muons  Jets  Transverse energy  Sum of T.Energy  Missing energy (neutrinos)

IJAZ AHMEDNational Centre for Physics11 Source of Muons  W, Z, Top, Higgs (prompt muons) Higgs (high luminosity)  B and c quark decay (severe B.G)  Hadron decay (pion, kaon (Low Luminosity)  Puchthrough of hadron shower  Cosmic muons (200 Hz/m**2)  Beam halo muons

IJAZ AHMEDNational Centre for Physics12 Transverse view of CMS Detector

IJAZ AHMEDNational Centre for Physics13 RPC segmentations

IJAZ AHMEDNational Centre for Physics14 Structure of L-1 Muon Trigger

IJAZ AHMEDNational Centre for Physics15 Principle of L1 GMT

IJAZ AHMEDNational Centre for Physics16 The Idea of Muon Trigger

IJAZ AHMEDNational Centre for Physics17 Trigger Levels in CMS Level-1 Trigger (e, , Jets, E T missing ) Latency: 3.2  s Input rate: 40 MHz Output rate: up to 100 kHz Custom designed electronics system High Level Trigger (several steps) More precise information from calorimeters, muon system, pixel detector and tracker Threshold, topology, mass, … criteria possible as well as matching with other detectors Latency: between 10 ms and 1 s Input rate: up to 100 kHz Output (data acquisition) rate: approx. 100 Hz Industrial processors and switching network

IJAZ AHMEDNational Centre for Physics18 Trigger Rates

IJAZ AHMEDNational Centre for Physics19 Track bending and strip width Single muon rate~1KHz/cm**2 RD-5 experiment Strip Geometry and Track Bending

IJAZ AHMEDNational Centre for Physics20 Track bending and strip length(Δη=0.1) Bending power ~17 Tm (barrel~ 8Tm at |η|=2.0 Strip Geometry and Track Bending

IJAZ AHMEDNational Centre for Physics21 Time of flight and signal propagation  Total time = T f + Ts + T rpc  If we require the time spread not to dominate the bunch crossing assignment precision it should not be longer than 5ns  Strip length= 2/3c x 5 x 10**-9 = 1m  Random coincidence by B.G of hits  False Trigger Strip Geometry and Track Bending

IJAZ AHMEDNational Centre for Physics22 Signal from RPC to GMT  Detector to Front end Electronics  Trigger Board  PAC ASICs  PAC->8 input strips  80 patterns per possible track  1 Tower->144 PACs  4 best muons->Global Muon Trigger

IJAZ AHMEDNational Centre for Physics23 Concluding remarks  Main advantage of the RPC Detector is that all the coordinates Ф, η and t are given by the same signal so no ambiguities can arise.  Superior time resolution of RPC allows us to use adjustable trigger gates shorter than 25 ns, which enables straightforward bunch crossing identification.