Clustering of very low energy particles

Carmen IglesiasIFIC-University of Valencia

Dpt. Fisica AMN

ATLAS Calorimetry Calibration Workshop, Štrba, Slovakia Dec 1 - 4, 2004

INDEX Summary of the last analysis Topoclusters in 8.2.0 Study the overlapping Preliminary Combined TB analysis

Tile Noise = 70 MeV, LArEM Noise = 70 MeV Tile Noise = 25 MeV, LArEM Noise = 70 MeV Seed_cut=4, Neigh_cut=2 CaloNoiseTool aplied

Very preliminary!!!

Summary of the last analysis

phi

eta

Seed Cell

Neighbour Cell

Summary last analysis (I) Use samples of single particles at very low Et (VLE), (because this is the range of

energy better to apply Energy Flow Algorithm) at eta=0.3 and phi=1.59: 0’s of 1, 3, 5, 10 and 30 GeV Neutrons of 1, 3, 5, 10 and 30 GeV +’s of 1, 3, 5, 10 and 30 GeV

in order to generated ntuples with 1000 events.

Start with these thresholds for Seed Cell and Neighbour cells of the Topocluster: Seed: E_cell/_noise=30 ->usual cut for particles of normal ET Neighbour: E_cell/_noise=3Compare different thresholds of the Noise in EM for the reconstruction of CaloTopoCluster of VLE particles: EM Noise=10 MeV (Non realistic case, only to check with VLE particles) EM Noise=70 MeV (Fix Value by default for EM cal in Sven’s code) CaloNoiseTool=true (package with a model for the electronic noise)

Repeat the analysis for lower threshold of Seed Cell and Neighbour cells : Seed: E_cell/_noise=6, 5, 4 -> cut for particles of very low ET Neighbour: E_cell/_noise=3, 2.5, 2

Summary last analysis (II) First, calculate the ET deposited in all CELLs of the calorimeter and consider it as

the “reference Energy Flow”, i.e., the best resolution that could be reach for the most sophisticated algorithm taking into account the whole ET in all the calorimeter.

For 0’s, compare the resolution of “reference Energy Flow” with the resolution of: Sliding Window Cluster EGAMMA cluster TOPOcluster in EM calorim: XXX_topoEM

For +’s and neutrons, compare the resolution of “reference Energy Flow” with : TOPOcluster in EM and Tile: XXX_topoEM and XXX_topoTile (7.8.0 release) PT of TRACKS from XKalman

Finally, study the ET inside a cone with a radius R=2+2

Neutral pions Cone’s centred in - coord of EGAMMA cluster Cone’s centred in - coord of TOPO cluster in EM cal Cone’s centred in - coord of TRUTH generated 0

Charged pions Cone’s centred in - of TRUTH generated Cone’s centred in - of TRACK position at 2nd layer

Neutrons Cone’s centred in - of TRUTH generated neutrons

Summary of the preliminary conclusions In TOPOCLUSTER using CaloNoiseTool package and applying:

Seed_cut: E_cell/_noise = 4 Neighbour_cut: E_cell/_noise = 2

obtain the best values of resolution for +'s, 0's and neutrons (Even better than EGamma resolution for 0’s)

eliminate the low efficiency of TOPOclusters for single particles at 1, 3, and 5GeV.

obtain the largest amount of ET deposited inside the TOPOclusters (Even larger than the ET deposited insider EGamma clusters for 0’s)

The best algo for the recon of the clusters from single particles at very low ET is: For ’s: Track-cone with R<0.2

TOPO give good results but worse than the two cone algorithms. For neutrons: Truth-cone with R<0.2

TOPO with Seed_cut=4 and Neigh_cut=2 is very near and it’s better at 1 and 3 GeV. For 0’s: Truth-cone with R<0.1

but TOPO is very near and it’s better at 1 GeV. EGAMMA give worse resolution, in general, is a better algo at 1 GeV

TOPO algorithm is very competitive for neutrons and 0’s, for ’s TOPO is a good algo but not enough, for now (I must test 8.2.0 release still)

Topoclusters in 8.2.0

Release 8.2.0 Reconstruction Packages

RecExample-00-00-94 RecExCommon-00-02-09 RecExTB-00-00-27

Calorimeter Packages CaloRec-02-02-19

Main Changes in this Release: “super-cluster”: one cluster for all calorim (EM+HEC+FCal+TCal=1region)

Splitter: Split clusters based on topological neighboring and E density defined local maxima. 

Information about cells wich form the TOPOcluster

Can use macro ROOT

The cells in a cluster are searched for local maxima by means of energy density. The so found local maxima are used as seeds for a topological clustering as in the CaloTopo-ClusterMaker.

I can analyse the ET of the cells inside TOPOcluster I can study the best cut in ET of cell without and with noise.

TopoClusters in 8.2.0

ET resolution Mean of ET_Cluster/ET_gen

ET (GeV) 7.8.0 8.2.0 % improv 7.8.0 8.2.0 % improv

1 64.31 --- 0.357 49.7

3 57.54 46.19 24.6 0.406 0.681 40.4

5 40.41 34.04 18.7 0.498 0.687 27.5

10 23.98 22.43 7.5 0.643 0.749 14.9

30 12.39 11.94 4.1 0.770 0.811 4.1

neu

ET resolution Mean of ET_Cluster/ET_gen

ET (GeV) 7.8.0 8.2.0 % improv 7.8.0 8.2.0 % improv

1 56.30 44.57 26.3 0.528 1.05 49.7

3 45.65 38.87 17.4 0.5807 0.8708 41,9

5 33.82 30.65 10.3 0.6522 0.8412 22.5

10 22.41 20.84 7.5 0.7613 0.864 11.9

30 13.91 13.36 4.1 0.8128 0.8515 4.9

+’s

ET Resolution and Mean of ET_Cluster/ET_gen are better than in 7.8.0 Release, even when the noise is applied. This improvement is larger at very low ET

Use samples of ±’s, neutrons

and 0’s

(instead of only single particles)

Estimate the existence of overlapping (a neutral hadron inside the cluster defined from the track of the charged pion) and its influence in the ET resolution Particles far away in R space Particles closer in R space (R=0.1) Particles closer in R space below 0.1

Generate Root-tuples using: 8.2.0 (without Splitter) 8.2.0 (with Splitter)

Do plots with Macro ROOT and see the maximum density points

Study the overlappingEfficiency of algorithm is limited by the overlap between neutral and charged particles in the cell of the calorimeter

compare the multiplicity and the ET resolution

Samples (nearby particles)

Particles closer in R space (R=0.1) Pi0pimneu10d1010: 0=10GeV +-=10GeV neu=10 GeV Pi0pimneu555d1010: 0=5GeV +-=5GeV neu=5GeV

Particles closer in R space below 0.1 Pi0pim77d05: 0=7GeV +-=7GeV in a distance R=0.05 Pi0pimneu555d0505: 0=5GeV +-=5GeV neu=10 GeV at R=0.05 and R=0.05 Pi0pip1010d05: 0=10GeV +-=10GeV in a distance R=0.05 Pi0pip55d07: 0=5GeV +=5GeV in a distance R=0.07

Froidevaux’s EFlow results: as long as particles not closer than R=0.1, Eflow performance is stable…(but still needs improvement!)

Froidevaux’s EFlow results: as R between particles decrease below 0.1, Eflow responseDegrades and develops significant tails (there is were the full use of ATLAS calor granularity, lateral and longitudinal, will surely provide improvements)

In generalPi0pim55: 0=5GeV +-=5GeVPi0pip28: 0= 2GeV +=8GeV Pi0pip82: 0= 8GeV +=2GeV

Multiparticles samples based on DC1 events simulated with electronic noise (but without pile-up) in the barrel region (||<1.5)

Particles far away in R space Pi0pimneu10hfar: 0=10GeV -+=10GeV neu=10 GeV Pi0pimneu10hfareta2 Pi0pimneu5hfar: 0=5GeV +=5GeV neu=5GeV Pi0pimneu5hfareta2

=0.35 and =1.63

ROOT plots: Particles far away in R spacePi0pimneu10hfar (N0 Splitter)

Is possible to distinguish 3 cluster from ECAL Middle layer up to Tile 2

ROOT plots: Particles closer in R space (R=0.1)Pi0pimneu10d1010

Is possible to distinguish 3 cluster but only at the end of ECAL and in TILE

ROOT plots: Particles closer in R space below 0.1Pi0pip1010d05 (N0 Splitter)

The two cluster are very closevery difficult to distinguish!!

ET resolution Calculate resolution with and without Splitter Cluster applied in Topoclusters:

Particles far away in R space

Particles closer in R space (R=0.1)

Particles closer in R space below 0.1 (R=0.05 and R=0.07)

ET Resolution Mean of ET_Cluster/ET_gen

No Splitter Splitter No Splitter Spliter

pi0pimneu10hfar 10.26 10.21 0.8171 0.8185

pi0pimneu5hfar 14.97 14.70 0.7535 0.7543

No Splitter Splitter No Splitter Spliter

pi0pimneu10d1010 9.34 9.32 0.8282 0.8287

pi0pimneu555d1010 13.96 14.17 0.7715 0.7717

No Splitter Splitter No Splitter Spliter

pi0pim77d05 11.87 11.89 0.8969 0.8975

pi0pimneu555d0505 14.51 14.55 0.7786 0.7801

pi0pip1010d05 9.04 9.00 0.9093 0.91

pi0pip55d07 14.77 14.74 0.8926 0.8944

First conclusions Very similar results!!, even in the case of particles generated to be very

close (R=0.05 and R=0.07)

EtDensityCut: All local maximum candidates must also pass it, specifying the min Et divided by the volume of the cell in order to be accepted as local max. The default value corresponds to Et= 500 MeV in a LArEM barrel layer 2 cell EtDensityCut = 500*MeV/600000*mm3

Very low energetic particles don't produce big local maxima as I I lowered the Seed_cut for topocluster maker I might to try lowering the seed cut in the splitter by the same factor I going to investigate the deposited ET in a LArEM barrel layer 2 cell by

Charged Hadrons at VLE Neutral Hadrons at VLE

ET deposited in EM cell of 2nd layerCharged pions

Neutral pions

the mean ET deposited in cell of EM on the 2nd layer for ±’s and 0’s at very low ET is ~280 MeV. So I'm going to change the EtDensityCut from the default value (500*MeV/600000*mm3) to 250*MeV/600000*mm3.

ET resolution with Splitter BUT the value of ET Resolution using the default EtDensityCut and

250*MeV/600000*mm3 in the 3 cases: Particles far away in R space Particles closer in R space (R=0.1) Particles closer in R space below 0.1 (R=0.05 and R=0.07)

are identical !!!

Even when I try to repeat the ROOT plots, I obtain the same plots!!

so :

From my results(*), I only can conclude that Splitter cluster can not be used tostudy the overlap of particle at very low energy (only useful for energetic particles)

(*) I don’t think that it will be a code fault because I was talking with S. Menke about the way to change EtDensityCut value in the code (in CaloRec/share/CaloTopoCluster_jobOptions.py)

Preliminary Combined TB analysis (8.8.0)

Offline reconstruction root-tuple CALO/168 contains the eta, phi, energy (in MeV) per LAr cell

CALO/169 contains the same for Tile cell TB/Tree contains the information about clusters

we have, for the time being, 4 times the final number of variables in the ntuple : em and combined clusters (sliding window), topo_em and topo_tile clusters.

nhit: total number of cells ecell: total energy NCells: number of cells in ntuple ECells: energy (MeV)

EtaCells: eta PhiCells: phi

DetCells: pseudo identifier

Emcluster: clusters from the sliding window algorithmTbemclusters: clusters from an algorithm that have been used in previous test beam. It has been added to allow comparison. It is a window of 3 by 3 cells.Emclusters and tbemclusters use only cells from the Larg calorimeter.Cmbclusters: sliding window clusters but they are done on towers (larg+tile) and not anymore on cells. It is not working for the moment because of a coordinateproblem between LAr and Tile, LAr is shifted with respect to Tile by "half module" :

TileCal has just 3 modules -0.15 < eta < +0.15 LAr has -0.2 < eta < 0.2,i.e. there are 3 slices with =0.1 in Tile and 4 slices in LAr, shifted by half of the slice

topo_em & topo_tile clusters:

Preliminary Results (TileNoise=70.0MeV)

By default LArEM Noise=70.0MeV and in this case this value is also used for Tile

ET Resolutionrun EM_SW TB_EM_SW TOPO_Em TOPO_Tile TOPO_total

9 GeV 2101022 8.91 7.26 9.44 70.49 11.54

8 GeV 2101024 10.09 8.15 10.80 57.34 13.93

7 GeV 2101086 11.73 9.11 12.36 46.03 16.56

6 GeV 2101025 13.47 10.35 14.24 41.87 38.50

5 GeV 2101026 17.01 12.64 18.40 35.17 39.88

3 GeV 2101087 16.19 22.34 71.12 23.80 33.33

2 GeV 2101088 14.15 73.84 70.15 22.84 40.20

1 GeV 2101089 ---- 63.14 59.76 ---------- -------

Very strange plots at 1 GeV: may be due to the low number of cluster well-defined

For TOPO_Tile the ET resolution decrease with the energy instead of increasing!!! There is a big lost of energy in Tile from 9 to 5 GeV, but from 3 GeV it decrease

Very bad result at very low energy (3, 2 and 1 GeV) for TOPO_Em

= 0.20

Sliding Window give an slightly better resolution than Topo

Mean Value of ET_cluster/ET_generatedrun EM_SW TB_EM_SW TOPO_Em TOPO_Tile TOPO_total

9 GeV 2101022 1.108 1.015 1.048 0.221 1.061

8 GeV 2101024 1.076 0.9841 1.012 0.2588 1.029

7 GeV 2101086 1.065 0.974 0.9978 0.29 1.011

6 GeV 2101025 1.053 0.9622 0.981 0.3479 0.9106

5 GeV 2101026 1.021 0.9341 0.9393 0.4259 0.7064

3 GeV 2101087 1.187 0.8738 0.5521 0.6884 0.8787

2 GeV 2101088 1.629 0.3937 0.4946 1.029 1.144

1 GeV 2101089 ---- 0.6067 0.7152 ---------- -------

There is a big lost of energy in Tile

For Sliding Window EM seems as the cluster energy is larger than the generated energymay be due to double counted??

Electron contamination distort the pions distribution for very low ET pions

Preliminary Results (TileNoise=25.0MeV)

From CIS analysis Richard claims that we have 1.6 ADC counts per channel which gives:1.6/1023*800/64/1.1*sqrt(2) = 0.025 GeV - electronics noise per cell

e/pi samples ET ResolutionTileNoise=70.0MeV

Seed_Cut=4, Neigh_Cut=3

TileNoise=25.0MeV Seed_Cut=4, Neigh_Cut=2

TOPO_Em TOPO_Tile

TOPO_total TOPO_Em TOPO_Tile TOPO_total

9 GeV 9.44(*) 70.49 11.54 9.89(*) 101.46 11.82

8 GeV 10.80(*) 57.34 13.93 11.44(*) 90.44 14.17

7 GeV 12.36(*) 46.03 16.56 12.89(*) 79.50 17.42

6 GeV 14.24(*) 28.56 17.64 14.51(*) 28.35 15.67

5 GeV 18.40(*) 25.56 22.30 18.67(*) 25.70 20.57

3 GeV 30.68(*) 23.80 33.33 33.01(*) 23.98 32.52

2 GeV 70.15(*) 22.84 40.20 71.45(*) 22.22 37.98

= 0.20

run SW EM SW TB EM TOPO_Em TOPO_Tile TOPO_total

9 GeV 2101179 23.51 22.07(*) 15.26(*) 84.70 19.40

7 GeV 2101180 20.56 15.67(*) 19.76(*) 25.38 32.17

6 GeV 2101154 13.69 10.44(*) 15.18(*) 26.44 16.37

5 GeV 2101166 15.42 12.64(*) 19.84(*) 23.12 23.53

4 GeV 2101151 14.42 20.93(*) 22.44(*) 21.18 42.22

=0.45

TileNoise=25.0MeV, Seed_Cut=4, Neigh_Cut=2Pions

(*) distributons with tails in left side

What is happening in TILE?Changing TileNoise from 70 to 25 MeV increase the bad defined topocluster with low energy (lower than ET generated) and its distorts the ET distribution. It will be needed to apply new cuts!!!

Why it happens only at larger ET?Cell_Cut = |E/noise|>Threshold so as noise has decrease to 25MeV, at larger E as 7, 8 and 9 GeV more cluster can pass the threshold.

What is happening in LArEM?In SW TB EM and TOPO_Em the distribution of ET resolution has tails in left side.These tails decrease with the ET of the particles. WHY?

Tails means cluster with ET lower than generated ET. So clusters has been reconstructed not completly.Seed_Cut = |E/noise|>Tcell so as E decrease it’s more difficult for the Seed_cellpass the threshold, but decreasing Tcell we’ll too much not real clusters.Neighbor_Cut = |E/noise|>Tneigh , again as E decrease it’s more difficult for the Neighbor cells pass the threshold and for this reason the cluster is not reconstructed So, if we have reduce the tails, we must put: longer (lightly) the Seed_cut lower the Neighbor_Cut

9 GeV 3 GeV

Electrons TileNoise=25.0MeV, Seed_Cut=4, Neigh_Cut=2

run SW EM SW TB EM TOPO_Em

9 GeV 2101204 9.26 8.27(*) 11.10(*)

8 GeV 2101057 10.56 8.90 (*) 12.52 (*)

5 GeV 2101200 15.50 13.56(*) 19.82(*)

=0.40 (*) with a peak near 0

9 GeV

8 GeV

- The best resolution from SW TB EM, i.e., clusters from an algorithm used in previousTB (3x3), but it has peaks near 0 (cluster with very low ET respect to the generated ET)- Clusters from the sliding window algorithm SW EM has not these peaks.(???)

The peaks near 0 values decrease with the ET of the particles

Next Steps:

Sort time plans: reconstruct CombinedTB data using CaloNoiseTool. (For this Workshop was imposible for me )

In future TestBeam release this tool will be available. (person in charge: Matthieu LECHOWSKI)

May be Preliminary results about it nex week during SW workshop at CERN???

Change the Threshold value for Seed_Cut and Neigh_Cut in order to validate my hipothesis

"Clustering of very low energy particles" ATLAS NOTE in preparation More Analysis with Combined TB real data Comparation with Combined TB Simulation data

…Complete Clustering analysis for Rome Physics Workshop