Status & results of PFA studies at U. Iowa Mat Charles Usha - - PowerPoint PPT Presentation

Status & results of PFA studies at U. Iowa

Mat Charles Usha Mallik

1

Event Type

e+e− → Z1Z2 qq (light jets) νν (light jets)

CM energy: 500 GeV

• This produces jets that have realistic energies,

but without excessive overlap.

• No confusion from jet-finding when calculating

dijet mass.

2

Barrel angle cuts

• For e+e− → ZZ, Z → light jets, jets tend to be

produced at small angles.

• In most events, a lot of energy goes down the

beampipe and resolution is lousy even with perfect pattern recognition.

• So we will look only at barrel events, defined by one
• f:
• Thrust of reconstructed jet has |cosϑ| < 0.8
• Generated quark has |cosϑ| < 0.8 in truth info
• Turns out not to make a big difference which we use.

3

acme0605

)

2

Dijet mass residual (GeV/c 50 60 70 80 90 100 110 120 130 Entries per 1 GeV bin 20 40 60 80 100

: 85.7482524

90

µ : 6.91099016

90

RMS

Event mass in barrel Width for physics: 6.9 GeV

Below Z mass ⇒ bias

4

acme0605

)

2

Dijet mass residual (GeV/c

• 40
• 30
• 20
• 10

10 20 30 40 Entries per 1 GeV bin 20 40 60 80 100

: -5.23752828

90

µ : 6.12522086

90

RMS

Mass residuals in barrel Width for algorithm development: 6.1 GeV

5

acme0605

)

2

Dijet mass residual (GeV/c

• 40
• 30
• 20
• 10

10 20 30 40 Entries per 1 GeV bin 50 100 150 200 250 300

: -5.14835757

90

µ : 6.09970774

90

RMS

Mass residuals in barrel (alternate angle cut) Almost no change w.r.t. nominal barrel cut

6

acme0605_steel_scint

)

2

Dijet mass (GeV/c 50 60 70 80 90 100 110 120 130 Entries per 1 GeV bin 20 40 60 80 100 120

: 83.7073796

90

µ : 7.27732482

90

RMS

Event mass in barrel Width for physics: 7.3 GeV Bias even worse

7

acme0605_steel_scint

)

2

Dijet mass residual (GeV/c

• 40
• 30
• 20
• 10

10 20 30 40 Entries per 1 GeV bin 20 40 60 80 100 120 140

: -7.35414919

90

µ : 6.52988089

90

RMS

Mass residuals in barrel Width for algorithm development: 6.5 GeV

8

)

2

Dijet mass (GeV/c 50 60 70 80 90 100 110 120 130 Entries per 1 GeV bin 20 40 60 80 100

: 87.349175

90

µ : 6.64252395

90

RMS

acme0605_w_rpc

Event mass in barrel Width for physics: 6.6 GeV Bias moderate

9

)

2

Dijet mass residual (GeV/c

• 40
• 30
• 20
• 10

10 20 30 40 Entries per 1 GeV bin 20 40 60 80 100 120

: -3.82898492

90

µ : 5.69404332

90

RMS

acme0605_w_rpc

Mass residuals in barrel Width for algorithm development: 5.7 GeV

10

)

2

Dijet mass (GeV/c 50 60 70 80 90 100 110 120 130 Entries per 1 GeV bin 20 40 60 80 100 120

: 88.3217593

90

µ : 6.80778351

90

RMS

acme0605_steel_rpc

Event mass in barrel Width for physics: 6.8 GeV Bias smaller

11

acme0605_steel_rpc

Mass residuals in barrel

)

2

Dijet mass residual (GeV/c

• 40
• 30
• 20
• 10

10 20 30 40 Entries per 1 GeV bin 20 40 60 80 100 120 140

: -2.55145842

90

µ : 5.87387943

90

RMS

Width for algorithm development: 5.9 GeV

12

Summary

Design RMS90 of mass (including Γ) RMS90 of residuals (no Γ) Bias

acme0605 [w/scint]

6.9 GeV 6.1 GeV −5.2 GeV

acme0605_steel_scint

7.3 GeV 6.5 GeV −7.4 GeV

acme0605_w_rpc

6.6 GeV 5.7 GeV −3.8 GeV

acme0605_steel_rpc

6.8 GeV 5.9 GeV −2.6 GeV

For this real (i.e. confused) PFA:

• RPCs give noticeably better resolution and smaller

bias than scintillators

• Tungsten gives somewhat better resolution than steel

13

Next steps

• Code is in CVS (but considered unstable)
• rg.lcsim.contrib.uiowa.NonTrivialPFA
• rg.lcsim.contrib.uiowa.NonTrivialPFAWrapper
• rg.lcsim.contrib.uiowa.NonTrivialPFAWrite
• Work with Ron to feed the PFA output into his

analysis tools (we are close!)

• Look again at the origin of the bias
• For energy sums it was an excess of (neutral → charged) confusion over

(charged → neutral)... is that still true for the dijet mass?

• Algorithm development, testing of new components
• Move on to next event type (4 jets)

14