1. Trigger Study For NEMO Phase 2 Tower
Bachir Bouhadef, Massimo Calamai, Mauro Morganti
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2. Outlines 1- NEMO Phase 2 Tower 2- Trigger for muon detection
3- Muon Life Time in NEMO Tower
4- Trigger Assumptions
5- MonteCarlo Simulation
7- Conclusion
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3. NEMO Phase 2 Tower 8 floors
8 m bars, vertical dist. = 40 m, Htot = 450 m
32 OM, 18 hydrophones
oceanographic instrumentation
The OM: 10” Hamamatsu R7081,
Front End Module, Time Calibration, LED beacons
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4. Triggers for muon detection
After space, time and a charge calibration, triggers are the first step for reaserching candidate muon hits.
Most of triggers are based on arrival time of hits and a charge threshold,
and assuming that all PMTs are equivalent identical.
Triggers efficiencies and their rates are estimated by a Montecarlo simulation
before being applied on raw data.
Our starting point was : is it possible to use only time hits rather than with
the charge information ?
Reasons could be : different PMTs or not well calibrated PMTs.
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5. 1- Muon life Time in Nemo Phase 2 Tower (direct and diffuse photons)
Using Mupage to generate vertical muon
tracks with Zenith angle 0-3°
Muon life Time is the time difference
between the first and the last photons of
the muon track.
Without
background
Direct photons
Direct and diffuse photons
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6. 1- Muon life Time in Nemo Tower (direct and diffuse photons)
Muon tracks with Zenith angle 0-85°.
Without background
Most of the muon track hits are
Within a Time Windows (TD).
We need at least 5 hits in different PMTs
to reconstruct the muon track.
We must look for a number of hits N
in a fixed time windows.
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7. Time Difference Distribution of the background
An optimal time windows for the trigger selection would be TW= ns
Probabilty of having 3, 4, 5, 6, 7, 8 hits in TW 1400 ns ?
We generate a background on 31 47kHz to study time
difference distributions.
Time different distribution between the
1st and 3th,…., 8th hit.
As the number of hits increses the mean time
difference distribution increases.
t3-t1
t4-t1
8 hits in TW=1400
t8-t1
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8. Time Difference Distribution of the background
Time difference distribution of the conditional probabilities (right), and
their integrales (left).
2hits in TW
3hits in TW
......
8hits in TW
2hits in TW
3hits in TW
......
8hits in TW
Black curve: probability distribution of having 2 hits in a TW=1400ns given that
the 3° is outside TW.
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9. Time Difference Distribution of the background
Probability of having 1,2, ... , 8 hits in TW given that 2end,....9th are not in the TW
N8TW1400 ≡ N7TW1000
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10. Time Difference Distribution of the background
Table of the Estimated rates
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11. Trigger Assumptions and Cuts
The fact that we need 5 hits, and in TW=1400ns with 8 consecutive hits we have at least 3 hits from backgound (60% ~ 30%+17.4%+7.8%+2.7%+0.7%....).
We can also look for 7 hits in TW=1200ns (N7TW1200)
or 6 hits in TW=1000ns (N6TW1000).
The selected sorted hits must have # pmt_id, which means
we can have more than 8 hits but take
only 8 that have # pmt_id.
How the Trigger works ?
8 hits
9 hits
Time
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12. Trigger Efficiency
Trigger efficiencies for N6TW1000 (black), N7TW1000 (red) and
T8TW1400 (bright green), at 47.2kHz (left) and 60 (right).
We can achieve a better efficiency by using
small N number of hits, but the corresponding
rates will increase.
The efficieny increases as the background rates
increase.
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13. Trigger Efficiencies INFN-Pisa 13 INFN-Pisa
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14. Trigger Efficiency 1 4 N8TW1400 (black)2 3 4
N8TW1400 (black)
L1SC (aqua)(1-2 or 3-4 in 20ns, or 1-3, 2-3, 2-4 in 100ns)
L1FC (bright green) between to adjacent floors.
N8TW1400 gives neary simlar effciency to L1SC with a lower background rate
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15. Trigger Cuts
After having 8 hits we have study the following possible cuts:
SC (1-2, 3-4) with Time windows 20 ns .
SC (2-3) with Time windows 100 ns .
FC with Time windows 300ns.
1- Cut_1 (black): t8-t1 <TW=1400
2- Cut_2 (red): Cut_1 & SC > 0 (1-2,1-3 or 2-3,4-3, 4-2)
3- Cut_3 (bright green): Cut_1 & FC>0
4- Cut_4 (bright blue): Cut_1 & SC > 0 & FC > 0
5- Cut_5 (yellow): Cut_1 & ( (SC > 0 & FC > 0) || SC>1 || FC>1))
6- Cut_6 (green): Cut_1 & (SC>0 || FC>0))
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16. Trigger Efficiency
Trigger Efficiency for TW=1200 (left) and TW= kHz
Cut_4 (bright blue) has the worst efficieceny in these triggers is
Cut_4 = Cut_1 & SC > 0 & FC > 0
1400ns
1200ns
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17. Trigger Rates We observe a trigger efficiency > 75%
with hits track higher than 15 for
N8TW1400 @ 47.2kHz and 60kHz.
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18. Triggers Comparaisons
Cut_1 (black) and Cut_4 (blue) for 47.2kHz (dash line) and 60kHz.
The background increases the trigger efficiency
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19. Triggers Comparaisons
Hits of detected muons
Hits of missed muons
Hits of detected muons
Hits of missed muons
@ 47.2 kHz
@ 60.0 kHz
@ 47.2 kHz
@ 60.0 kHz
Distibution total number of hits of
muon tracks
Distibution number of PMTs by
muon tracks
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20. Trigger Rates Estimated rates on simulated and raw data INFN-Pisa 20
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21. NEMO Phase 3 Tower Time Windows can be reduced,
14 floors
8 m bars, vertical dist. = 20 m
48 OM
Time Windows can be reduced,
which means low backgrund rates.
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22. Conclusion
1 – Full montecarlo for trigger test was done and tested on Raw Data.
2 - We have seen that selecting N hits in a TW as a first step reduces
drasticaly the background trigger rates.
3- The tigger is not based on Charge threshold.
4 – The efficiency of these triggers are optimistics.
6- These triggers will be tested on CPU-GPUs.
7- We have seen that N7TW1000 gives better efficiency with same rates as
N8TW N6TW still under studies.
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