View
3
Download
0
Category
Preview:
Citation preview
Trigger in ATLAS (and CMS)
1
NICA/SPD workshop, PRAGA, 12.02.2014
V.Kukhtin, JINR, Dubna
Outline
- LHC, CMS and ATLAS
- the main parameters important for design of the trigger system
- multi-level trigger,
- 1st, 2nd and 3d level triggers
- conclusions
2 NICA/SPD workshop, PRAGA, 12.02.2014
8 intersection points
4 experiments
3 NICA/SPD workshop, PRAGA, 12.02.2014
2 general purpose detector - CMS and ATLAS on the floor 4 NICA/SPD workshop, PRAGA, 12.02.2014
CMS detector
5 NICA/SPD workshop, PRAGA, 12.02.2014
ATLAS detector
6 NICA/SPD workshop, PRAGA, 12.02.2014
Calorimeters
7 NICA/SPD workshop, PRAGA, 12.02.2014
Muon spectrometer
8 NICA/SPD workshop, PRAGA, 12.02.2014
The main boundary conditions
for the trigger system design:
bunch crossing frequency( information appearance frequency )
rates of PP-interactions, energy -> variety of interesting physical processes
event size
mass storage capacity
9 NICA/SPD workshop, PRAGA, 12.02.2014
Clock is distributed from P4 to the detectors
LHC
10 NICA/SPD workshop, PRAGA, 12.02.2014
One wants to record all physics -common objects
11 NICA/SPD workshop, PRAGA, 12.02.2014
12 NICA/SPD workshop, PRAGA, 12.02.2014
The table of different trigger rates
Какие же триггеры и какие их пороги выбраны в
первом уровне
Отметить, что пороги загружаемы
Светимость уменьшается – частоту записи на
носители оставляем постоянной – снижаются
требования
Live time of the beams ->
luminosity, rates goes down ->
change thresholds setting to keep output rate constant
13 NICA/SPD workshop, PRAGA, 12.02.2014
The conditions shown above determine the basic features of the trigger
and data acquisition system:
a multi-level trigger with pipelined front-end readout and
hierarchical data acquisition architecture.
The functional scheme reflects the nature of the expected event selection
chain:
a level-1 trigger with negligible dead time and with the shortest possible
latency , making an identification of the bunch crossing containing the event
of interest;
a level-2 trigger with programmable algorithms based on local data;
a level-3 trigger for which the full detector information will be used.
Trigger logic
14 NICA/SPD workshop, PRAGA, 12.02.2014
15 NICA/SPD workshop, PRAGA, 12.02.2014
L1 receives its input from the Calo. and Muon
detector signals stored to front-end pipelines,
pending L1 decision
designed to provide latency < 2.5 mks and
output rate 75 kHz(->100 kHz
If L1=“TRUE”, data from each detector -> ROB
and made available for HLT for further analysis
HLT = L2 + EF, farms of commodity processors,
connected by fast dedicated network
L2 is based on fast custom algorithm,
processing data within RoI provided by L1.
designed output rate ~ 3 kHz,
processing time – 40 ms/ev
EF is based on mostly offline algorithms to
reconstruct the data with greater precision
than L2.
designed to reduce the rate to ~ 400 Hz,
processing time ~ 4s/ev
Schematic of ATLAS trigger
16 NICA/SPD workshop, PRAGA, 12.02.2014
Trigger L1
17 NICA/SPD workshop, PRAGA, 12.02.2014
Some details of the L1 trigger - Calorimeter
18 NICA/SPD workshop, PRAGA, 12.02.2014
Some details of the L1 trigger - Muon spectrometer
19 NICA/SPD workshop, PRAGA, 12.02.2014
20 NICA/SPD workshop, PRAGA, 12.02.2014
Thresholds are changed within the beam life-time to keep
event output rate ~ constant
L1 – thresholds setting
21 NICA/SPD workshop, PRAGA, 12.02.2014
High level trigger
22 NICA/SPD workshop, PRAGA, 12.02.2014
Trigger performance
23 NICA/SPD workshop, PRAGA, 12.02.2014
Encore un fois
The ATLAS trigger scheme
24 NICA/SPD workshop, PRAGA, 12.02.2014
Conclusions
The multilevel trigger approach
takes into account all physics processes of interest;
permits to realize fast reconstruction algorithms with
the dedicated electronics;
permits to apply offline algorithms for events reconstruction;
permits to get reasonable output rate for data storage without
loosing data quality.
HIGGS boson was found with this trigger logic !!!!!!!!!!!!!!!
Such approach to the trigger construction for the NICA detectors seems to be
very reasonable
25 NICA/SPD workshop, PRAGA, 12.02.2014
Backup slides
26 NICA/SPD workshop, PRAGA, 12.02.2014
27 NICA/SPD workshop, PRAGA, 12.02.2014
28 NICA/SPD workshop, PRAGA, 12.02.2014
29 NICA/SPD workshop, PRAGA, 12.02.2014
30 NICA/SPD workshop, PRAGA, 12.02.2014
Recommended