Preliminary Design of Trigger System for BES III

Zhen’an LIU

Inst of High Energy Physics,Beijing

Oct. 14 2001

Zhen'An LIU, Oct 13-15 2001

BESIII Workshop, IHEP, BEIJING

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Outline

Introduction

Estimation of event rate

The principle of BESIII trigger

Subsystems Description

Summary

Zhen'An LIU, Oct 13-15 2001

BESIII Workshop, IHEP, BEIJING

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Introduction

BEPCI: low luminosity(310 30cm-2s-1). Single bunch mode bunch separation: 800ns trigger:latch-process-decision

e-

RFRF SR

e+

IP

BEPCII

BESIII

BEPCII: double ring high luminosity(10 33cm-2s-1). multi-bunch mode bunch separation 8ns

TRIGGER FOR BESII CAN NOT BE USED IN BESIII

Zhen'An LIU, Oct 13-15 2001

BESIII Workshop, IHEP, BEIJING

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Introduction(2)

BES III: new vertex detector new MDC new TOF new EMC(barrel BGO

endcap CsI) superconducting magnet new muon counter

new FEE for all subdetectors

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A NEW TRIGGER SYSTEM MUST BE DESIGNED !

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Estimation of event rate

Good physics events(J/, at BEPCII/BESIII)Bhabha and radiative Bhabha scattering

Machine background Coulomb scattering, Bremsstrahlung with

residual gas Touscheck scattering

Cosmic Ray background

Purpose:To accept all interested eventsTo rejects as much background as possible

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Background from Lost particles

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Background from Lost particles

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Machine backgroundIntensity: IBEPCII = (1.1+1.1) A, ( 1.1 1013 e )

( 40 IBEPC)

Lifetime: BEPCII = 3.5~3.8 hr

(0.5 BEPC)

Lost rate: (dn/dt) BEPCII = 8.7 108/s

(80 dn/dt BEPC)

Lost rate(BESIII): (dn/dt) BESIII 1.3 107 /s

N beam-BEPCII = 13MHz (80 N beam-BEPC)

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Layer 1HV OFF

1HV ON

2 3 4 5 6 7 8 9 10

Total channelsin each layer

64 128 192 256 224 272 320 368 416 464 512

Channelscalculated

>58 >124 >182 >251 >217 >262 >314 >364 >400 >441 >492

NBES2 37.38 333.8 374.9 265.3 312.9 252.1 303.6 226.4 193.6 139.4 89.76dE/dX NPBES2 107.0 955.7 1073 759.6 895.8 721.8 869.2 648.2 554.3 399.1 257.0

NBES2 27.95 223.5 147.0 109.0 118.5 119.1 109.9 117.2 96.39 85.74 53.88dE/dX“and”TIME NPBES2 80.02 639.9 420.9 312.1 339.3 341.0 314.6 335.5 276.0 245.5 154.3

BG measurement of MDC in BES2

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Machine background

BEPC/BESII 15Hz at DAQ Single wire of 1st

layer of MDC

BEPCII/BESIII 30KHz on single

MDC wire at R=17cm

1500 Hz (DAQ)

Fig:Backgrounds rate vs beam current

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Flux Beijing=170 m-2 s-1

N =1500 /s

BESI/II:•T window = 40 ns•95% suppressed•N cosmic = 1 Hz

Cosmic ray background

BESIII:•No time window• similar geometrical size to BESI/II•Same # of cosmic rays hitting on BESIII•Using Vertex counter

N cosmic = 20 Hz

Zhen'An LIU, Oct 13-15 2001

BESIII Workshop, IHEP, BEIJING

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Good physics +Bhabha events

Luminosity LBEPCII = 1 1033 cm-2 s-1

Optimized to J/ and energy

N J/ = 1500 HzN J/ = 1500 Hz

N ´= 420 HzN ´= 420 Hz

N BB = £ BB = 550 Hz (| cos |< 0.95)

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BESIII Workshop, IHEP, BEIJING

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Total event rate

Total event rate

= good event rate

+ cosmic event rate

+ bhabha rate

+ machine background rate

= ~ 3000 Hz

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BESIII Workshop, IHEP, BEIJING

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The principle of BESIII trigger

Trigger requirement no dead time or small total dead time Flexibility

Constraints from BEPCII 93 bunches in the ring (8 ns separation)

Latch-process-decision mode not possible in 8ns

Pipeline must be used in FEE & trigger

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Trigger pipeline

Constraints due to Detectors Tdrift MDC = 500 ns(C3 H8 + small cell), signals from

different collisions mixed together

Trigger pipeline clock: RF division (fRF=499.8MHz)

20MHz (fRF/24) all trigger promitives are processed every 50ns

Trigger latency

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The principle of BESIII trigger(2)Hardware trigger + software filter(L2)FEE signal splitted:trigger + FEE pipeline

Trigger pipeline clock 20MHz

Level 1(L1): 2.4 sFEE Control Logic checks L1 with pipeline clockL1 YES:moves pipeline data to readout

buffer

L1 No: overwritten by new data

Detector

switch

BESIII FEE pipeline and Data flow

Level 1FEEpipeline

Readoutbuffer

Farms

Disk

Time Reference

0 s

2.4s

Ev.Filter

(L2)

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Glo

bal T

rigg

er L

ogic

2.4 s

Schematic of BES III Trigger

VC

TOF

MDC

EMC

MU

DISC

DISC

DISC

Mu trackDISC

BTE Sum

Hit Count

Track Finder

Tile Processor

Total Ener Sum

Hit/Seg Count

Track Seg. Finder

L0 trigger Logic

DAQ

RF TTC

Tile Sum

FEE

L1P

L0P

CLOCK

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Subsystem Description

MDC Trigger

EMC Trigger

Trigger Timing and Control

Global Trigger Logic

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Trigger for MDC

MDC: 5740 wires, 36 layers in 9 super-

layers 6 stereo superlayers 3 axial superlayers

•Trigger:•Axial superlayers for trigger•PT > 150 MeV•step1: track segment finding•step 2:track-finding

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Track Segment Finder Reference layer: second layer in

each super-layers Segment definition

3/4 logic in a superlayers Track segments:

Superlayer 1: 66 Superlayer 2: 162 superlayer 3: 192 superlayer 4 270

Track finder Reference Segment: second

superlayer

(track reference: 162) Track definition

all 4 segments in 4 superlayers

MDC Tracking

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Track Segment finding

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MDC track combination MC Calculation

MC Private code random P(0.15-1.547GeV),

initial angle in phi B = 1.0 T Ask for all superlayers with

segment hit

combinations for each reference segment ~ 117

realization with CPLD or FPGA

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EMC(Barrel) trigger

BEMC: 19360 BGO crystals 88 rings along Z 44 rings with 240 crystals(inner) 44 rings with 200 crystals(outer)

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Tile:30( )22(z)

Z

TILE:25( )22(z)

BTE:25cellsBTE:30cells

Totoal Energy Trigger:

sum of all tile signals

thresholds

Segmentation:

8() 4(z) = 32 segments

Vthl and Vthh

No. Of segments

Event time

Basic Trigger element(BTE):

BTE1:FEE sum of 30 cells

BTE2:FEE sum of 25 cells

Tile:

Tile1:sum of 23 BTE’s

Tile2:sum of 23 BTE’s

EMC(Barrel) Trigger

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BESIII Workshop, IHEP, BEIJING

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Trigger Timing and Control(TTC)

fRF= 499.8 MHz

fRF /12 40MHz FEE TDC clock

fRF/24 20MHz trigger & FEE pipeline clock

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Global Trigger LogicInputs: subdetector primitives

Time adjustment

trigger table

Prescaling of some event types

System Configuration

Trigger data readout

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SummaryPipeline will be used

Hardware trigger + software filter

Hardware: level 0 + level 1(L0 is spare signal for FEE)

Latency:L0- 200 ns, L1- 2.4 s

Monte Carlo simulation undergoing backgrounds Subsystem trigger scheme

Collaboration domestic and international

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BESIII Workshop, IHEP, BEIJING

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THANK YOU !

WELCOME COLLABORATIONS!