EF with simple multi-particle states

Vishnu V. Zutshi

NIU/NICADD

Hadron Position Resolution

• Since Eflow invariably involves associating clusters near an extrapolated track …

• How to do this in a digital calorimeter ?

• Study this using charged pions

• Resolution is defined w.r.t. the MC extrapolated position

10 GeV charged pionsD

ensi

ty w

eigh

ted

Ene

rgy

wei

ghte

d

unweighted

10 GeV charged pions

“Density”

• Need a hierarchy in the absence of an energy measurement

• Clumpiness of the surrounding • A simple-minded realization of this used here:

di = (1/dRij) where dRij is the angular

distance between cell ‘i’ and cell ‘j’

10 GeV

unweighted

Density weighted

Mea

sure

d re

lati

ve to

the

ener

gy w

eigh

ted

reso

luti

ons

Cell area at first layer=

0.64cm2

Thanks Ben

10 GeV

Mea

sure

d re

lati

ve to

the

ener

gy w

eigh

ted

reso

luti

ons

Cell area at first layer=

4cm2

Density weighted

unweighted

10 GeV

Mea

sure

d re

lati

ve to

the

ener

gy w

eigh

ted

reso

luti

ons

Cell area at first layer=

6cm2

Density weighted

unweighted

10 GeV

Mea

sure

d re

lati

ve to

the

ener

gy w

eigh

ted

reso

luti

ons

Cell area at first layer=

9cm2

Density weighted

unweighted

10 GeV

Mea

sure

d re

lati

ve to

the

ener

gy w

eigh

ted

reso

luti

ons

Cell area at first layer=

12cm2Density weighted

unweighted

10 GeV

Mea

sure

d re

lati

ve to

the

ener

gy w

eigh

ted

reso

luti

ons

Cell area at first layer=

16cm2Density weighted

unweighted

2GeV Photons

maxima

maxima

maxim

a

Clustering

• Local ‘density’ maxima chosen as seed clusters

• Membership of each cell in the seed clusters decided with a distance function

• Calculate centroids

• Iterate steps 2 and 3 till distortion is below some threshold

Could be unique or shared

Parameters

• Cell thresholds

• How many layers to lump together

• Neighborhood for maxima search

• Minimum no. of layers hit

• Neighborhood for membership

• Proto-cluster definition

• Uniqueness of membership

10 GeV 0H

igh asymm

etryD

ensi

ty w

eigh

ted

10 GeV 0M

edium asym

metryD

ensi

ty w

eigh

ted

10 GeV 0L

ow asym

metry

Den

sity

wei

ghte

d

10 GeV 0L

ow asym

metry

Den

sity

wei

ghte

d

10 GeV 0

Recon. energy

Recon. mass

18%

10 GeV 0

Recon. energy

Recon. mass

Energy asymmetryA

= a

bs(E

–

E

)/(E

+

E

)

p

p

Den

sity

wei

ghte

d

p

p

Den

sity

wei

ghte

d

p

E/Egen

Eflow

Cal only

n

EMCal

HCal

n

n

EMCal

HCal

n

p

nre

cE ()

genE ()

Not reliable due to noncom

pensation

n

• Get the e/pi for the SD detector

• Scale the MC truth with that function

• Take the ratio of the reconstructed pion energy with the scaled MC truth

• This should have a mean of 1.0 (with an atrocious resolution) if things are working ok

n

Summary/Outlook

• A first pass clustering/track association algorithm exists applicable to EM/HAD, both analog/digital

• Encouraging results for multiparticle events• More detailed study to expand and enhance

(for instance particle id)• Move to jets• Feedback into calorimeter design