Performance Study of BESIII Trigger System Z.-A. Liu, D. Zhao, D. Jin, H. Xu, S. Wei, W. Gong, K. Wang, Q. Wang, N. Berge, K. Zhu, IHEP Q. An, USTC May

Performance Study of BESIII Trigger System

Z.-A. Liu, D. Zhao, D. Jin, H. Xu, S. Wei, W. Gong, K. Wang, Q. Wang, N.

Berge, K. Zhu, IHEP Q. An, USTC

May 25, 2010, Lisbon, RT2010

Outline

Brief hardware description Trigger table settings and Data samples Efficiency determination Summary

System Block diagram of BESIII Trigger

TCBA

Glo

bal T

rigg

er L

ogic

6.4 s

TOF FEE

MDC FEE

EMC FEE

MU FEE

TOFPR

MFT

Mu trackFastOR

Track Finder

Etotal Energy

Hit/Seg Count

Track Seg. Finder

BEPCII RF TTC

TC Sum

L1P

41.65 MHz

Track Match

Energy Balance

Cluster Counting

Fast Control

FC Daughters

Near Detectors Counting Room

499.8 MHz

High Lights: Optical Isolation-no ground loop current

May 25 2010 LIU,Zhen'An, RT2010,Lisbon 4

List of Trigger Conditions


List of Trigger Conditions(2)


List of Trigger Conditions(3)

Not used in data taking in 2009


Trigger Table settings for the 2009 ψ′ running.

Channel 0 is designed for endcap Bhabha events channels 1 to 5 for events with charged particles in

the barrel region and channel 11 for all-neutral events.


Trigger Table settings for the 2009 J/ψ running

Channel 0 is designed for endcap Bhabha events channels 1 to 5 for events with charged particles in the barrel region channel 11 for all-neutral events. The only difference with regards to the ψ′ running is the removal of cha

nnel 3 due to high noise.


Data Samples

Trigger settings for the 2009 ψ′ trigger test running.• Channel 0 is used for MDC trigger checks, • channel 1 for EMC trigger checks and • channel 2 for ToF trigger checks.• RUN 9903-9992 taken in May 2009

Trigger settings for the 2009 J/ψ trigger test running.• Channel 0 is used for MDC and ToF trigger checks, • channels 1, 2 and 3 for EMC trigger checks and • the other channels served as a backup• RUN 10583-1058, taken in July 2009


Sample Selection a polar angle ϑ in the range | cos ϑ| < 0.97 are considered. The barrel region is defined as | cos ϑ| < 0.8, the endcap region as 0.83 < | cos ϑ| < 0.97

Bhabha:• Two EMC showers with energy ± 10% beam energy• Showers with |cos(θ)| < 0.97 (< 0.8 for barrel),• shower opening angle > 166• Two good tracks with opening angle > 175• two Kalman-fitted tracks are required with their dis-tance of closest

approach to the origin < 1 cm in the radial direction and < 5 cm along the beam direction.

• Use EMC triggered events (channel 1) to check MDC and ToF• Use MDC/ToF triggered data (channels 2,3,4) to check EMC


Sample Selection(2) a polar angle ϑ in the range | cos ϑ| < 0.97 are con

sidered. The barrel region is defined as | cos ϑ| < 0.8, the endcap region as 0.83 < | cos ϑ| < 0.97

Charged Hadron:• good tracks with a distance of closest approach to the or

igin of less < 1 cm in the radial direction and < 5 cm along the beam direction.

• Two or more such tracks are required to be present in the event.

• If there are exactly two tracks, their opening angle is required to be less than 170◦ in order to suppress Bhabha and dimuon events


Sample Selection(3) a polar angle ϑ in the range | cos ϑ| < 0.97 are considered. The barrel region is defined as | cos ϑ| < 0.8, the endcap region as 0.83 < | cos ϑ| < 0.97

Dimuon Selection:• two good charged tracks with opposite charges and the spacial ang

le between them should be larger than 3.1 rad. • The definition of a good charged track is identical to the one in the

Bhabha selection. • In addtion we require that the momentum of each track is less than

2 GeV and the deposited energy in the EMC is less than 0.7 GeV.• The total four-momentum (E, px, py, pz) is required to fall in the (3.

2 4,−0.1 0.1,−0.1 0.1,−0.2 0.2)GeV region after assuming each track is muon


Sample Selection(4) a polar angle ϑ in the range | cos ϑ| < 0.97 are considered. The barrel region is defined as | cos ϑ| < 0.8, the endcap region as 0.83 < | cos ϑ| < 0.97

ψ′ −> π+π−J/ψ Selection:• Four good charged tracks, two positive and two negative. • The good charged tracks are defined as in the previous selections.• Then we assume the softer tracks of each charge are pions and ha

rder tracks are leptons. • After that assumption we also require the recoil mass of the two pio

ns to fall into the region (3.08, 3.12)GeV, • the invariant mass of two leptons is required to be in the region (3.0,

3.2)GeV, and the total energy of the event should be in the range (3, 4)GeV


Efficiency Determination Determination of Trigger Condition Efficiencies.

• N stands for the number of events,• sel for events passing the physics selection, • channel for events having triggered the reference chann

el and • condition for events with the trigger condition under stud

y active. • The reference channels used for the various data sample

s can be found in table


Efficiency Determination Determination of Trigger Channel Efficiencies. .

• N stands for the number of events,• sel for events passing the physics selection, • channel for events having triggered the reference channel and • condition for events with the trigger condition under study active. • The reference channels used for the various data samples can be fo

und in table


Trigger condition efficiencies for ψ′ data taking

The numbers have statistical errors of the order of 0.1% in efficiency


Trigger condition efficiencies for J/ψ data taking

The numbers have statistical errors of the order of 0.1% in efficiency


Determination of EMC Threshold behavior

Threshold energies and resolutions Threshold scan. At the end of the 2009 ψ′ running, a thresh

old scan was performed, where the settings for both low and medium thresholds were changed from run to run.


Trigger Channel Efficiencies Global trigger efficiencies for ψ′ running.

The statistical errors are below 0.1% in efficiency


Trigger Channel Efficiencies Global trigger efficiencies for J/ψ running.

The statistical errors are below 0.1% in efficiency


Conclusions BES III trigger efficiencies studied for both the 2009 ψ′and

J/ψ running. In general the efficiencies are high enough that they contrib

ute less than 0.5% overall efficiency loss for events with and energy deposition above 1 GeV and/or at least two charged tracks in the barrel.

For events not fulfilling these criteria, some care is needed as there are inefficiencies up to 3% (for endcap dimuons), stemming from localized inefficiencies in the EMC and global inefficiencies of the ToF system.

All efficiencies quoted here are valid only for the BES III active solid angle, i.e. the very forward and backward regions as well as the cracks between the barrel and the endcaps are not included.


Backups


ψ′： Group Channel（ GC）： Endcap，charged,Barrel charged, neutral

Here gcn is the efficiency of group channel n, cn is the efficiency of channel n, ǫn is the efficiency of condition n, P(n|m) is a conditional probability, i.e. the probability of condition n given condition m. Our readeres should notice that if the trigger conditions are not in dependent of each other, we have to consider the correlations of among them


J/ψ： Group Channel（ GC）： Endcap，charged,Barrel charged, neutral

Here gcn is the efficiency of group channel n, cn is the efficiency of channel n, ǫn is the efficiency of condition n, P(n|m) is a conditional probability, i.e. the probability of condition n given condition m. Our readeres should notice that if the trigger conditions are not in dependent of each other, we have to consider the correlations of among them

Documents

Performance Study of BESIII Trigger System Z.-A. Liu, D. Zhao, D. Jin, H. Xu, S. Wei, W. Gong, K. Wang, Q. Wang, N. Berge, K. Zhu, IHEP Q. An, USTC May