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The RPC LVL muon trigger Cross Rate

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					  The ATLAS RPC Level-1 Muon Trigger:
         Design and Simulation
                      Francesco Conventi
                 University of Naples and INFN Naples
                             on behalf of
                Naples and ROMA1 Level-1 Trigger group




VIIth Workshop on Resistive Plate Chambers and Related Detectors
                              Overview

                               LHC machine and ATLAS
                               detector
                               Physics @ LHC
                               Muon Spectrometer
                               Trigger/DAQ in ATLAS
LHC   and ATLAS detector
Level-1   Muon Trigger
                            Trigger chambers: RPC
Level-1   Simulation       Level -1 RPC Trigger Logic
                            and segmentation

                                Detector description
                                Coincidence Windows
                                Physics performances
ATLAS experiment @ LHC
                          LHC Radius              4.2 km
                         Circumference            ~27 km

                             Energy               14 TeV

                           Luminosity           1034 cm-2s-1

                       bunch crossing rate   40 MHz (tbc=25 ns)

                         protons/bunch             ~1011


                                ATLAS detector


Muon Spectrometer

Hadronic calorimeter

EM calorimeter

Inner Detector
                        The ATLAS physics program
The high energy and luminosity of the LHC offers a large range of physics opportunities:
  Higgs boson searches (113.5 GeV/c < mH < 1 TeV/c)
  SUSY
  Precision measurements (W and t quark)
                                                For mH > 130 GeV/c the best experimental
  B physics                                             signature come from the

         SM Higgs branching fractions                     H  4 μ decay mode
         The ATLAS Muon Spectrometer
                     Sector 5
 view                            Barrel: | η | < 1.1
                                  Tracking with MDTs
                                       Layout M
                                  Triggering with RPCs

                                  End cap: 1 < | η | < 2.7
                                  Tracking with MDTs & CSCs
                                  Triggering with TGCs
                                        2-meter wide hole




                                       Layout P



                                                                h view
Acceptance :     |h | < 2.7
pT Resolution:
       ~10%      pT 1    TeV/c           3 stations of RPCs!
       <3%       pT < 250 GeV/c
 L LENGTH
                The ATLAS Muon Spectrometer
mal view : 35 mm
     The Magnet systems                                      8 separate coils
                         Y (cm)                              Huge dimension: 20 m in
                                                             diameter, 25 m in length
                                                             Toroidal configuration in the
                                                             Barrel region: Tracks deflelcting
                                                             mainly in the h side.

                                                                  RPC
                                                                  MDT


                                                    X (cm)
 e, CEA/DAPNIA/SEDI   CHEP 24/03/2003   12
         Moore
                      H4 μ   (MH= 130 GeV/c)
                      Muon Spectrometer standalone

                                             Deflection depends on
                                             the pT value!

                      MH(reconstructed)=129.5 GeV/c                                    h view
                                             σ= 3.1 GeV/c
                                           The triggering chambers: RPC
        h readout               Bakelite
           strips                Plates                          Each ATLAS Units is composed by
HV                                               Foam            two independent RPC layer!!

                                                               Grounded
                                                                planes

                          Gas                                   More than 1000 RPCs will be
                                                                installed in the BARREL region for
                                                                a total of coverage of 3650 m2

       Graphite                             readout
      electrodes                                                           2  readout strips
                       PET spacers            strips

The ATLAS RPCs Units:                      ATLAS RPC Requirements:                      Layer2
  Gas mixture:                               High efficiency and time
                                           resolution (1 ns)
C2H2F4 94.7% - C4H10 5% - SF6 0.3%                                         Layer1
                                            High rate capability (100
Working in Avalanche Mode                  Hz/cm2)
                                             Resolution of 5-10 mm in
 Readout strips:                           the  projection (2nd
2 orthogonal readout strips allowing       coordinate measurements)
                                                                          2 h readout strips
the measurements of h and 
coordinate
ATLAS RPC: Production and Test status*
                                                                RPC Efficiency

                                                 98% of tested units have
                                                 Efficiency > 97%



                                                 2% of Efficiency is lost
                                                because of the PET spacers
    Naples Cosmic rays Test Station             and border effects

 Preliminary Test Results on 250 RPCs
                                   Plateau @ 10 kV
                                   (Naples conditions)




*for details see P. Iengo’s presentation @ RPC 2003
 Interaction rate (1 GHz)
                                             The ATLAS Trigger/DAQ scheme
                                                                    The Level 1 Logic
     Level-1 Trigger
        output: 100 KHz


                                All data
   Level-2 Trigger              Region Of Interest
           output: 1 KHz        Rejection factor ~102
                                Latency ~10 ms

                                   Events reconstruction
  Level-3 Trigger (EF)             Rejection factor ~10
                                   Latency ~1 s

           DAQ (100 Hz)

                                                            Data from Calorimeter ⊕ μ Spectrometer
Bunch-crossing                   40 MHz
                                                             Bunch Crossing Identification
Luminosity                       1034 cm-2 s-1
                                                             Region of Interest determination
tot (p +p  X)                   80 mb                     Rejection factor 104
                                                             Latency ~ 2.5 μs
Interactions rate = tot  L     109 Hz
Interactions/bunch-crossing      25
                                      Basic principle
Level1 Trigger Logic in the
                               (Physics): Selection of events
   Spectrometer Barrel         with muons having a large
                               trasverse momentum (pT)
                                (Trigger): Identification of
                               candidate muon tracks
                               coming from the interaction
                               vertex within a pT range.
                               (Algorithm): Demand a
                               coincidence of hits in
                               different RPCs chamber
                               within geometrical road.


                              Level-1 algorithm performed in
                              both h and  projections
                              2 pT regimes:
                               Low-pt ( μ < 10 GeV/c) with
                              RPC1 and RPC2
                               High-pt ( μ  20 GeV/c) with
                              RPC2 and RPC3 ⊕ Low-pT
  32
Trigger           RPC
Sectors


                                                       h strips

                                   strips

                          A trigger sector in the η projection




A trigger
 sector
            RPCs located in the
            MIDDLE and OUTER
                  sectors
                   Level-1μ Trigger segmentation
 All the relevant functions needed for the barrel trigger algorithm are
performed by the COINCIDENCE MATRIX ASIC (CMA)
  About 4000 CMA in the whole barrel
                                                                            Off detector

     RPC n.3           High Pt CMA (x4)            High Pt PAD              Sector
                                                       (x6/7)
                                                                                Logic

                                                                                   MUCTPI
     RPC n.1                                        Low Pt PAD
                           Low Pt CMA (x4)
     RPC n.2                                                    (x6/7)

On detector

The CM A board
  Timing and shaping the
signals from RPCs
 Trigger algorithm (3 pT
threshold)
 Majority logic
 Readout
                                                                          ROI
                                              Projection of a PAD
                                              onto the pivot plane




                      A PAD corresponds to
                      2 eta-CMs and 2 phi-CMs

The position of a ROI is given by overlap of an eta-CM with a phi-CM
The Coincidence Matrix
  Asic (CMA) scheme
Level-1 μ Trigger: Simulation
A code with very detailed simulation of the logic of the basic hardware
components and of the related readout format run in the ATLAS offline
simulation framework (ATHENA).
   RPC positions and structure are derived from an ASCII database
   (AMDB) which includes also detailed informations on inactive volumes
   (PET spacers, border)

   Detector response has been modelled                  RPC        97%
according to the behavior of RPCs measured
in laboratory test using GEANT3 package              Cluster size   1.2
   Level-1 simulation: The algorithm
   Associate to each pivot strip a   The width of the COINCIDENCE
  COINCIDENCE WINDOW in the          WINDOW depends on:
 Low-pT and in the High pT system     The pT threshold
                                       η coordinate
                     pT>(pT)thr
   pT<(pT)thr                         Muon Spectrometer layout   pT>(pT)thr
RPC3
High-pT
                                                                    pT<(pT)thr


RPC2
Pivot
            OK                              OK
          KO                                 KO
RPC1
Low-pT
                 Coincidence window
Level-1 simulation: The coincidence windows              |h|=1.05


                                                  Bdl (Tm)
      Coincidence Windows width




 0                                1
                                       η



                                        An automatic procedure is
                                      able to determine the ~ 20000
                                      foreseen Coincidence Windows
                                           in the Spectrometer

                                                    6 GeV

                                                    8 GeV

                                                   10 GeV
Level-1 simulation: Acceptance
                ATLAS Support structures

                    Low-pT acceptance: μ hit (at least)
                    3 out of 4 readout planes (in both η
                    and  projections)
                    High-pT acceptance: Low-pT ⊕ (at
                    least) ½ planes in the outer station.
Level-1 simulation: Trigger performances
                       A large sample of single muon events with a wide pT
Single muons           range has been tracked in the simulated detector,
                       processed using the simulation code and applying
                       the predefined Coincidence windows




Trigger Efficiency curves for 90% (nominal) efficiency at threshold
               Level-1 simulation: Trigger rates
Using the Level-1 Efficiency curves we may estimate the rates with different threshold.

       pT _ cutoff                                Level-1
                                                 Efficiency
Rp =       
           0
                 p   ( pT )   (pT) dpT

  Muon            6 GeV        20 GeV
 sources        threshold     threshold
                                                       Major source in the Low-pT
  /K                7100        680
                                                       Great uncertainty on σ
   b                 1400        500

   c                  800        210

   W                   3         26

   t            negligible negligible

  Low-pT Trigger rates ~ 10 kHz                Inclusive μ cross-section @ LHC
 High-pT Trigger rates ~ 1.5 kHz                  (prompt μ and /K decay)
                 Conclusions
The ATLAS Barrel Level-1 muon trigger is a big and complex
system:
   Extremely high initial interactions rate (1 GHz)
   Large RPCs system (~1000 Units, 3650 m2)
   Trigger electronics reduces informations from 350k readout
   channels to 400 32-bit words
   Flexible pT selection system (Low/High pT )
   Events rejection factor 104

Big efforts from both hardware and software community:
   Production, QC and Tests of the RPCs
   Developments of very detailed simulation code

Simulation results confirm the design performances of the
Level-1 RPC system
   Selection efficiency for all the High/Low pT thresholds and
   trigger rates

				
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posted:12/19/2010
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Description: The RPC LVL muon trigger Cross Rate