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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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slide1

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.
slide2

Towers 8+9 represent 92% of the rate

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

slide3

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 ()
slide4

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

slide5
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
slide6

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?

slide7

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).

slide8

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)

slide9

HO-RPC Mapping

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

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

slide10

Trigger Algorithm

HO provides extra “RPC plane”

slide11

 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)

slide12

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

slide14

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

Deser.

Deser.

Rx

Rx

Deser.

Deser.

Rx

Deser.

Rx

Deser.

Rx

Rx

Deser.

Deser.

Rx

Rx

Deser.

Deser.

Rx

Rx

Deser.

Deser.

Rx

Rx

Deser.

Deser.

Rx

Rx

Deser.

Deser.

Rx

Rx

Deser.

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

slide18

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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