MotivationGeneral 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.

HO Scintillators in RPC Muon Trigger Conceptual design

HO Scintillators in RPC Muon Trigger Conceptual design

J. F. de Trocóniz, UA-Madrid

Towers 8+9 represent 92% of the rate

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

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 ()

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

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

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 pefor “quiet” QIEs.

Is this performance good enough? Can be achieved systematically at

CMS?

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).

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)

Electronic Noise

HO-RPC Mapping Equilibrium between large acceptance and simplicity (hardware implementation) Minimal Map

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

HO provides extra “RPC plane”

Trigger Algorithm

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)

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

ORCA Results

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

SPLITTER

S-linkto DAQ

to Level-1 trigger

90 m @ 1.6Gbit/s

up to 5 m LVDS @ 80MHz

QIE

GOLQIE

QIE

HTR(Readout)Board

Optical Tx

Optical Tx

HCAL Front-end

New 'Optical SLB'

HTR Configuration for HO

P2

P1

8

88-way fiber in

8-way fiber in

FPGA

Rx Deser.Rx Deser.Rx Deser.Rx Deser.

Rx Deser.Rx Deser.Rx Deser.Rx Deser.Rx Deser.Rx Deser.Rx Deser.Rx Deser.

Rx Deser.Rx Deser.Rx Deser.Rx Deser.

Rx Deser.Rx Deser.Rx Deser.Rx Deser.

Rx Deser.Rx Deser.Rx Deser.Rx Deser.Rx Deser.Rx Deser.Rx Deser.Rx Deser.

Rx Deser.Rx Deser.Rx Deser.Rx Deser.

SLBSLB

SLB

SLB

SLB

SLB

FPGA

Outputs toRPC Crate

Total of 48 calorimeter channels per HTR

DAQout

Front-end datainputs

Example of cabling scheme satisfying

all constraints at HO and RPC ends

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