New Cluster Moments for Jet Cleaning Atlas Reco meeting Sven Menke, - - PowerPoint PPT Presentation

New Cluster Moments for Jet Cleaning

Atlas Reco meeting Sven Menke, MPP M¨ unchen

• 4. Oct 2011, CERN

Definition of the new cluster moments Example distributions Use for jet cleaning

Definition of the new cluster moments

Some quantities for jet cleaning are still calculated on the CaloCell level Most notably the quality and the amount of negative energy could so far not be extracted from clusters on the AOD The following new moments make this information now available on AODs, such that jet cleaning code can be written to use clusters and not cells:

• BADLARQ_FRAC: the energy fraction inside the cluster carried by cells

with a quality larger than Qmin (4000 by default)

• ENG_POS: the sum of the energies of all positive cells
• SIGNIFICANCE: the ratio of the cluster energy over the cluster noise:

Eclus/ σnoise, where the sum runs over all cells

• S. Menke, MPP M¨

unchen New Cluster Moments for Jet Cleaning Atlas Reco meeting, 4. Oct 2011, CERN 2

Example distributions

Plots are from 1000 single pion MC events (3820 clusters) Only one cluster had bad quality – and the fraction is 1.4.

• it’s larger than 1 because it had

−260 MeV negative and +610 MeV positive energy – i.e. the bad cell had +500 MeV Positive energy (in MeV) reflects the simulation of pion energies flat in logE Significance is on average 3 orders of magnitude smaller than energy in MeV

• signals above 1 GeV start to be

significant

• but this depends of course on the

region in the calorimeter

c.getMomentValue(CaloClusterMoment::BADLARQ_FRAC) 0.2 0.4 0.6 0.8 1 1.2 1.4 1 10

2

10

3

10 c.getMomentValue(CaloClusterMoment::ENG_POS) 200 400 600 800 1000 1200 1400 1600 1800

3

10 × 1 10

2

10

3

10 c.getMomentValue(CaloClusterMoment::SIGNIFICANCE) 200 400 600 800 1000 1200 1400 1600 1 10

2

10

3

10

• S. Menke, MPP M¨

unchen New Cluster Moments for Jet Cleaning Atlas Reco meeting, 4. Oct 2011, CERN 3

Use for jet cleaning

For jet cleaning the sampling fractions and time can be computed as before since all 24 sampling energies and the cluster time are available

• n AOD

Jet quality fraction can be computed like so: fjet =

clusters fcluster × Eem−scale cluster

/Eem−scale

jet

If different regions (EM/HEC) need to be distinguished the λcenter moment of the cluster and its η can be used to compute the region it is in Negative jet energy can be computed like so: Eneg

jet = clusters Eem−scale cluster

− Epos

cluster

More info is on the Twiki: ClusterMoments

• S. Menke, MPP M¨

unchen New Cluster Moments for Jet Cleaning Atlas Reco meeting, 4. Oct 2011, CERN 4