analysis of events with large met in cruzet3...

Alfredo Gurrola

Anwar Bhatti, Teruki Kamon, Shuichi Kunori,

Latife NukhetVergili, Ming Yan

Presenting on behalf of the HCAL-ROC Group

MET Working Group Meeting Aug. 19, 2008

Analysis of Events with Large MET

in CRUZET3 Data

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OutlineGoal : The primary goal of this talk is to outline our current

understanding of the cause of high MET events in CRUZET3

data. I present the progress that has been made toward being

able to categorize & remove these events. We hope to get feedback

as we move toward analyzing CRUZET4 data.

High MET events in CRUZET3 data

Event classification: HPD noise, RBX noise, etc.

What characterizes each type of high MET event? (event displays, etc.)

Variables for “noise” filtering

MET rates before & after filtering

“Noise” filter applied to a SUSY LM2 sample

Other possible filtering methods

Conclusion: Summary & Comments2

High MET Events in CRUZET3

MET > 200 GeV:

Event Rate: 0.9836 Hz

Run # 51490 CRUZET3 data showed that there were a large

number of high MET events.

• Using the RAW data files, events with MET > 50

GeV were re-reconstructed to include the DIGI

information in addition to RecHits, Jets, MET, etc.

already included in the RECO files.

• Run 51490 (Muon+HCAL triggers): (2.7M events)

• 50 < MET < 100 GeV : 17663 events

• 100 < MET < 300 GeV : 9371 events

• 300 < MET < 500 GeV : 2047 events

• 500 < MET < 1000 GeV : 1737 events

• 1000 < MET : 1265 events

• Run 51047 (MuonTrigger): (5.8M events)

• 50 < MET < 100 GeV : 605 events

• 100 < MET < 300 GeV : 216 events

• 300 < MET < 500 GeV : 17 events

• 500 < MET < 1000 GeV : 15 events

• 1000 < MET : 5 events3

Event ClassificationThere are several types of occurances that can contribute to high MET

events. For best overall efficiency (in terms of MET “cleaning”), we

must first categorize the types of events so that one can gain an idea on

how to proceed to remove/clean these high MET events.

RBX noise events

Electronics failure in the entire readout box produces large rechit energies

HPD noise events

Electronics failure in a single HPD produces large rechit energies

Muon/Air shower signal

Real muon showers in the calorimeter and produces large rechit energies

EB abnormal events

Noise in ECAL produces huge rechit energies4

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 15 - 2 16 - 2

11 59 29 19 67 16 - 42 32 20 11 26 35 12 - 27 20 16 41

12 9 8 2 6 13 2 2 - 5 7 11 - 3 3 5 7 1 6

13 29 13 2 11 33 14 9 4 10 38 13 5 45 5 15 10 10 15

14 4 4 - 8 2 1 7 8 6 8 6 7 6 7 6 8 10 10

iPhi

iEta

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 15 - 2 16 - 2

31 1 1 1 1 1 1 1 1 - 1 1 1 1 1 - - 1 -

32 2 3 1 2 2 2 2 2 4 2 2 1 2 2 1 1 1 1

33 4 3 3 3 3 3 4 3 3 2 3 2 5 3 3 2 2 2

34 8 8 8 8 7 8 7 5 6 6 7 4 6 4 5 5 3 3

iPhi

iEta

RBX Noise Consider an event that passed the HCAL trigger:

Run 51490 : Event # 242453; MET = 749 GeV; Erechit > 1.5 GeV

Consider an event that passed the muon trigger:


“Flat” energy profile – A similar trend is seen for the adjacent slices

Energy of HCAL

Rec Hits (GeV)

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Electronics failure in the entire readout box produces rechits

with large energies (muon does NOT traverse the calorimeter)

RBX Noise

Run 51047 : Event # 1259085

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RBX Noise RateWhat is the RBX noise event rate?

# of RBX noise events for Run 51490 :

50 < MET < 100 GeV : 10 events out of 100 scanned events




MET > 1000 GeV : 1 event out of 100 scanned events

Only 100 events were scanned per MET skim section. Therefore, we must

scale the number of RBX noise events by some scale factor to obtain an

estimate of the event rate that corresponds to the full statistics.

50 < MET < 100 GeV : 10 x (17663/100) ~ 1766 events

100 < MET < 300 GeV : 25 x (9371 / 100) ~ 2342 events

300 < MET < 500 GeV : 21 x (2047 / 100) ~ 430 events

500 < MET < 1000 GeV : 7 x (1737 / 100) ~ 121 events

MET > 1000 GeV : 1 x (1265 / 100) ~ 13 events

MET > 50 GeV:

Rate: ~ 0.5 Hz

MET > 100 GeV:

Rate: ~ 0.3 Hz

Estimate !7

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 15 - 2 16 - 2

7 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

8 0 0 0 0 0 166 68 0 0 2 0 0 0 0 0 0 0 0

9 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

10 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

iPhi

iEta

HPD Noise

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 15 - 2 16 - 2

7 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

8 4 2 5 6 7 3 5 362 648 2 4 5 13 2 2 2 2 0

9 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

10 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

iPhi

iEta

Consider an event that passed the HCAL trigger:


Consider an event that passed the muon trigger:


Narrow energy profile - Noise is only seen along 1 particular slice

The HPD noise rate is ~ 3 (1) Hz for MET > 50 (100) GeV

Energy of HCAL

Rec Hits (GeV)

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High MET Event (Muon Shower) Consider events that passed the muon trigger:

# of events for Run 51047 that produced high MET due to muon showers in HF



300 < MET < 500 GeV : 1 event out of 17 scanned events

500 < MET < 1000 GeV : 1 event out of 15 scanned events

MET > 1000 GeV : 1 event out of 5 scanned events

Only 100 events were scanned for some MET skim sections. Therefore, we must

scale the number of events caused by muon showers by some scale factor to

obtain an estimate of the event rate that corresponds to the full statistics.

50 < MET < 100 GeV : 16 x (605/100) ~ 97 events

100 < MET < 300 GeV : 11 x (216 / 100) ~ 24 events

300 < MET < 500 GeV : 1 x 1 = 1 event

500 < MET < 1000 GeV : 1 x 1 = 1 event

1000 < MET : 1 x 1 = 1 event

Similarly, the rate is 0.05 Hz (0.015 Hz) for MET>50 (100) GeV in HB and HE .

MET > 50 GeV:

HF Rate: ~ 0.0083 Hz

MET > 100 GeV:

HF Rate: ~ 0.0018 Hz

Estimate !9

High MET Event (Muon Shower) A muon traverses only the HCAL region and produces large

amounts of energy in HCAL.

Run 51047 : Event # 1597384

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EB Abnormal Events Some examples of events with high MET caused by ECAL noise:

Run 51490: Event # 237817; MET = 1.06E13 GeV; rechit time = -7.08E14 ns



Run 51490: Event # 2350776; MET = 1615 GeV; rechit time = -8.28E4 ns

Run 51490: Event # 347714; MET = 231 GeV; rechit time = -2.00E4 ns

For Run 51490, roughly 212 EB abnormal events were found.

Total runtime for Run 51490 ~ 10,000 seconds

ECAL noise is random relative to the muon and HCAL triggers

0.7 second live time

Event rate for EB abnormal events is ~ 300 Hz for run 51490.

NOTE: The rate is < 1 Hz in run 51047. We need to keep monitoring.

wrong rechit time!

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EB Abnormal Events

Run 51490 : Event # 4132998

Large amounts of rechit energies show up in ECAL – muon does

not create large MET (muon does not shower in the calorimeter)

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Filtering High MET Events• There are two questions that should be asked as one proceeds to

attempt to filter out “bad” events.

1) How can we filter out “bad” events after reconstruction has taken place?

• Case 1: A cosmic event is NOT in coincidence with a “real” event.

• Monojets, energy of associated tracks vs. calojet energy, etc.

• Case 2: A cosmic event is in coincidence with a “real” event.

• This will be more difficult to untangle. We need to develop the most simple methods

that are effective at removing “bad” events, but yet have high signal efficiencies.

2) Can we filter out “bad” events before event reconstruction takes place?

• I will not discuss this in a lot of detail in this talk, but I will comment on it later.

Let’s consider the case when a cosmic event overlaps a “real” event.

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• How can we filter out “bad” events after reconstruction has taken place?

• Samples:

• SUSY_LM2 (CMSSW_1_6_7)

• CRUZET3 Run #51490

• Compute the Had. or Em. energy fraction for jets with PT > 100 GeV (IterativeCone5)

• Define our HCAL “noise” filter: Require the highest PT jet to have EHCAL/E < 0.98

• Define our ECAL “noise” filter: Require the highest PT jet to have EECAL/E < 0.98

“Noise” Filter

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MET > 200 GeV:

Pre-Filtering – Rate: 0.9836 Hz

Had Filter - Rate: 0.026 Hz

Had+EmFilter – Rate: 0.00055 Hz

“Noise” Filter

How effective is the “noise” filter?

• Apply it to Run 51490

• 0 overflow entries after applying both filters

Before Filter – All TriggersAfter Filters – All Triggers

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“Noise” Filter

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MuonTrigger HCAL Trigger

“Noise” Filter

SUSY_LM2

Pre-Filter

SUSY_LM2

After Filtering

• Does the filter have high efficiency for “real” signal events?

• Apply the filter to a SUSY LM2 sample

• 7,041 events analyzed

• 7,011 events remain after the HCAL fraction requirement is applied

• Relative Efficiency = 7011 / 7041 ~ 99.6 %

• 6,883 events remain after the ECAL fraction requirement is applied

• Relative Efficiency = 6883 / 7011 ~ 98.2 %

• Efficiency loss occurs mostly for MET < 100 GeV

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• There are limitations to the previous filter.

• The filter will not remove high MET events caused by both HCAL and ECAL noise

(e.g. ECAL noise and RBX noise occur simultaneously).

• The current filter will not remove events where “noise” (or a cosmic muon) produces

a high PT jet that is NOT the highest PT jet in the event.

• Can we require ALL jets to satisfy the HCAL & ECAL fractional energy requirements?

• Probably NOT! e.g If a signal event has > 10 jets, the signal efficiency can drop < 90%

• In any case, we need to develop other methods or variables.

• Can we develop simple algorithms that can be easily implemented in HLT?

• Rechit energy profile, # of rechits above threshold, etc.

• Work in progress (Ming Yan, Alfredo Gurrola, …)

Let’s consider other possible methods or algorithms …

“Noise” Filter

Energy Profile (Preliminary)SUSY_LM2

CRUZET3

= 0

CRUZET3

= 0

High MET events caused by RBX noise and

muon showers are characterized by “flat”

energy profiles in and

• consider the energy profile of towers relative

to the seed tower of jets (IterativeCone5)

• difference in between a particular

tower and the seed tower

• difference in between a particular

tower and the seed tower

•There’s discrimination in both and

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Additional Methods (Preliminary)• Possible HPD noise filter :

• We have already seen that HPD noise is characterized by very narrow energy profiles

• Noise occurs in only 1 slice

• We can use an isolation type algorithm to remove HPD noise from the MET calculation

(see talk by Ming Yan at the Jets + MET Topology meeting):

1) Count the # of RecHits with Energy > X per cell (iphi, ieta)

2) If the above # is > Y, then count the # of RecHits above threshold in the adjacent cells in iphi

3) If there are 0 RecHits above threshold in the “isolation” region (adjacent cells), tag this as HPD noise

• Prelimary results: For Run 51490, how many events were found that satisfied the

above criteria?

• 1466 out of 1737 events with 500 < MET < 1000 GeV (X = 50, Y = 10)

• 1054 out of 1265 events with MET > 1000 GeV (X = 50, Y = 10)

• 12403 out of 17663 events with 50 < MET < 100 GeV (X = 25, Y = 4)

• Are ALL of these events HPD noise ? How efficient is the algorithm ? What are the fake rates ?

• We are developing similar algorithms using an energy profile type analysis similar the

one discussed in the previous slides (takes into account the MET dependence of X & Y).

2121

Additional Methods (Preliminary)• Pulse Shape Analysis :

• Noise in both ECAL and HCAL will produce pulse shapes with very random

structures relative to a “true” signal pulse shape

• Consider an event that passed the HCAL Trigger (RBX noise) …

• The pulse shapes correspond to that of 1 particular event per sample coming from

the highest PT jet (PT > 100 GeV)

SUSY LM2

Run 51490 : Event # 525371

MET = 501.936 GeV

Summary and Comments• We have a better understanding of the source of high MET events in CRUZET3 data

• We have been able to obtain a very simple filter that is extremely effective at removing “bad” high MET events while maintaining a high signal efficiency

• CRUZET3 Run 51490: 7 (2) events remain out of 3.7M events with MET > 100 (200) GeV

• The remaining events are most likely due to muons that produce energy in both ECAL and HCAL

• There’s currently work in progress to untangle the source of the remaining high MET events.

• SUSY LM2: ~ 98 % absolute efficiency

• Optimization is still needed (e.g. Should we consider ALL jets?)

• Additional filtering algorithms are currently being considered.

• Energy profile in and (preliminary results were already shown)

• # of rechits above threshold (isolation type algorithm) – see talk by Ming Yan

• Timing – ECAL noise produces large negative values of rechit times (HCAL and cosmic muon/air shower happens randomly with respect to the LHC clock)

• Pulse shape analysis (“noise” is random relative to the “LHC clock”)

• …

• Should we consider applying MET corrections instead of discarding the events?

Need to

be tested!

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We welcome feedback and ideas

analysis of events with large met in cruzet3...

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