HO Scintillators in RPC Muon Trigger
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HO Scintillators in RPC Muon Trigger Conceptual design. J. F. de Trocóniz, UA-Madrid. Motivation General rule for muon triggers: Never neglect a possible backup reduction factor. It will always come back to you. Even if RPC trigger works just fine from the beginning one still wants to:

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Motivation general rule for muon triggers

HO Scintillators in RPC Muon Trigger

Conceptual design

J. F. de Trocóniz, UA-Madrid

Motivation

General rule for muon triggers:

  • Never neglect a possible backup reduction factor. It will always come back to you.

    Even if RPC trigger works just fine from the beginning one still wants to:

  • Reduce rate in regions with only 4 or 3 RPC planes available.

  • Reduce pt thresholds as much as possible. HO should be better than any pre-scale.


Motivation general rule for muon triggers

Towers 8+9 represent 92% of the rate

(pt> 10 GeV, || <1.24), but only 16% of the acceptance


Motivation general rule for muon triggers

HO Characteristics

  • 10 mm Bicron scintillator tiles positioned between coil and MB1 RPC

  • 1 plastic for Wheels ±1, ±2.

    2 plastics separated by 15 cm iron slab in Wheel 0.

  • Covers the full MB1 system (barrel + overlap) up to || < 1.24 (Tower 9)

  • Typical cell size: 40 cm () × 50 cm ()

  • Granularity: 0.087 () × 0.087 ()


Motivation general rule for muon triggers

  • HO matches well muon system in r-  view (MB1)

    : 0.087  5 deg  16 RPC strips  OK

  • Not that well in r-

    : 0.087 (HCAL standard tower size)  detailed HO – RPC map needed


  • Motivation general rule for muon triggers

    HO Readout

    • Standard HCAL readout:

      Fibers HPD (G=2500)  QIE (T=25 ns)

    • 90% of energy in two samples (phase independent of HCAL)

    • More light:

      • Thicker plastics,

      • 4 WLS loops/tile,

      • shorter fiber path

  • Designed to give 10 pe / mip

  • Trigger: Energy-over-threshold bit


  • Motivation general rule for muon triggers

    Test beam results

    Actual performance of HO system (Wheel 1 scintillators) measured at 2002 test beam (Jim Rohlf).

    • 6 pe/mip/plastic Gaussian noise at normal incidence.

      • 1.5 pe-equivalent/bucket

      • can be improved to 0.9 pe

        for “quiet” QIEs.

    Is this performance good enough?

    Can be achieved systematically at CMS?


    Motivation general rule for muon triggers

    HO Performance

    Simulated with CMSIM123

    280 MeV/mip/plastic at normal incidence  6 pe

    0.9 pe/bucket  64 MeV

    Geometrical acceptance: 93%

    Signal width dominated by photo-statistics.

    HO threshold at 1% tile occupancy 150 MeV (1 MeV deposited).

    Similar efficiency for 1.5 pe/bucket of noise, but 8 pe at signal peak, for EHO > 150 MeV (3% tile occupancy).


    Motivation general rule for muon triggers

    Electronic Noise

    Backgrounds

    p-p interactions (1034 cm-2 s-1): < 2 Hz/cm2

    Neutron-induced conversions: < 10 Hz/cm2 (MB1 level)

    n-p elastic collisions: < 25 Hz/cm2 (for EHO > 150 MeV)


    Motivation general rule for muon triggers

    HO-RPC Mapping

    Equilibrium between large acceptance and simplicity (hardware implementation) Minimal Map

    Acceptance always larger than 90% (often much larger).


    Motivation general rule for muon triggers

    Trigger Algorithm

    HO provides extra “RPC plane”


    Motivation general rule for muon triggers

     Require HO confirmation for low-quality RPC coincidences

    Built-in high efficiency (low quality RPC muons are ~30%)

    Remarkable threshold stability (allows tuning at CMS)


    Motivation general rule for muon triggers

    Rate reduction

    • RPC noise trigger rates simulated using ORCA

      (50 Hz/cm2, nominal neutrons)

    • Large sample: 110 Mevents, corresponding to 4.4 s of LHC.

    • High quality noise trigger fraction much smaller than 1%.

      For 0.9 pe/bucket,EHO > 150 MeVReduction factor = 100

      For 1.5 pe/bucket, EHO > 150 MeV Reduction factor = 30

      Low-pt rates w/ HO comparable to high-pt w/o HO


    Motivation general rule for muon triggers

    ORCA Results


    Motivation general rule for muon triggers

    Connecting Hardware(preliminary)

    • Processing of HO signals performed at HTR boards (4 boards/sector,

      2 FPGA/board).

    • Provide energy-over-threshold programmable bit (possibly -dependent).

    • All OR-ing corresponding to the HO-RPC  map also handled here

    • Input fibers organized according to constraints at HO end.

    • SLB cards organize HTR bits into bit streams, and transmit to RPC Trigger Boards using GOLs (32 bits/bx)

    • Output streams organized according to constraints at RPC end.


    Hcal ho in rpc trigger

    TRIGGER

    BOARD

    READOUT

    BOARD

    HCAL (HO) in RPC Trigger

    HCAL Front-end

    QIE

    GOL

    to Level-1 trigger

    QIE

    New 'Optical SLB'

    QIE

    HTR

    (Readout)

    Board

    Optical Tx

    SPLITTER

    Optical Tx

    90 m @ 1.6Gbit/s

    S-link

    to DAQ

    up to 5 m LVDS @ 80MHz


    Htr configuration for ho

    Rx

    Rx

    Deser.

    Deser.

    Rx

    Rx

    Deser.

    Deser.

    Rx

    Deser.

    Rx

    Deser.

    Rx

    Rx

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    Rx

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    Rx

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    Rx

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    Rx

    Rx

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    Rx

    Rx

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    Rx

    Rx

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    Rx

    Rx

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    Rx

    Rx

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    Deser.

    Rx

    Rx

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    Deser.

    Rx

    Rx

    Deser.

    Deser.

    8-way fiber in

    Rx

    Rx

    Deser.

    Deser.

    Rx

    Rx

    Deser.

    Deser.

    8-way fiber in

    Rx

    Rx

    Deser.

    Deser.

    HTR Configuration for HO

    Total of 48 calorimeter channels per HTR

    SLB

    SLB

    FPGA

    P1

    Outputs to

    RPC Crate

    SLB

    SLB

    SLB

    P2

    SLB

    DAQ

    out

    FPGA

    Front-end data

    inputs

    8

    8


    Motivation general rule for muon triggers

    Example of cabling scheme satisfying all constraints at HO and RPC ends


    Motivation general rule for muon triggers

    Conclusions

    Investigating how to incorporate HO into RPC trigger:Geometrical integration, RPC+HO extended algorithm, basic lines of hardware implementation established.

    If HO performance at 2002 test beam achieved systematically at CMS  RPC trigger rate reduced by 100.

    Efficiency O(90%) stable as a function of HO energy threshold (allows tuning).

    Implications much more important in case RPC noise can be reduced to 5 Hz/cm2 consider HO to improve efficiency (less restrictive algorithms, tower 6, “classic” 3/4).

    HO is now part of the L1 Trigger Baseline


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