HCAL Pre-‐CD-‐1 Conceptual Design
Review November 2nd, 2017
Conclusions from Pythia Analyses • Response from different detector configura4ons does not depend on R
9/20/17 Rosi Reed -‐ HCal 2
Songkyo Lee
Conclusions from Pythia Analyses • Response from different detector configura4ons does not depend on R or strongly on pT
9/20/17 Rosi Reed -‐ HCal 3
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Raghav Elayavalli
Conclusions from Pythia Analyses • Response from different detector configura4ons does not depend on R or strongly on pT
• Response slowly degrades with removal of interac4on lengths with ac4ve readout – There is no cliff that we fall off of – inclusive observables are rela4vely insensi4ve
– Unfolding will start to become difficult – Minimal fragmenta4on bias will increase
• Will have further study
9/20/17 Rosi Reed -‐ HCal 4
Jet in Heavy Ion Collisions • Large, fluctua4ng background in heavy-‐ion collisions complicates jet analyses – Combinatorial jets – Changes Jet Energy Scale (JES) – Changes Jet Energy Resolu4on (JER) – Jet finding Efficiency
• Solu4ons involve – Background subtrac4on – Selec4on of “hard” processes – Unfolding
9/20/17 Rosi Reed -‐ HCal 5
Jet in Heavy Ion Collisions • Large, fluctua4ng background in heavy-‐ion collisions complicates jet analyses – Combinatorial jets – Changes Jet Energy Scale (JES) – Changes Jet Energy ResoluKon (JER) – Jet finding Efficiency
• Solu4ons involve – Background subtracKon – Selec4on of “hard” processes – Unfolding
9/20/17 Rosi Reed -‐ HCal 6
These are the key aspects that pertain specifically to the HCAL design
Background SubtracKon
• sPHENIX MIE, subtrac4on rou4ne à arxiv:1203.1353
• We are con4nuing to work on this à 2 features not yet implemented: – Refinement of exclusion region defini4on in first itera4on step
– Flow es4ma4on / modula4on
• It is important to note that the background is determined for each calorimeter layer separately!
7 Rosi Reed -‐ sPHENIX Collabora4on Mee4ng -‐ June 2017
8 Rosi Reed -‐ sPHENIX Collabora4on Mee4ng -‐ June 2017
arxiv:1203.1353
For now using R=0.2, pTreco > 25 GeV jets before subtracKon as exclusion regions”
No v2 modulaKon yet
Background SubtracKon • Algorithm adjusts the addi4on to the JES by the UE, and requires: – Creates 0.1x0.1-‐towerized version of CEMC – Crea4on of towers from all 3 calorimeter subsystems
– Default jet reconstruc4on • Es4mates UE contribu4on to towers in η=0.1 rings – Separate for each layer – Creates new UE-‐subtracted tower containers
• Jet reconstruc4on has been modified to handle nega4ve-‐E tower inputs
9 Rosi Reed -‐ sPHENIX Collabora4on Mee4ng -‐ June 2017
Jet Response • Background smears reconstructed momentum – Increases JER – Depends on R and pT
• Can decrease reconstruc4on efficiency
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Erin Bossard
Erin Bossard
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ReconstrucKon Efficiency • Truth jets are associa4on with closest reco jet within ΔR < Ran4-‐kT – If this fails, the jet is not reconstructed
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� Larger jets and lower pT jets can be obscured by the fluctua4ng background
pp
AA
Erin Bossard
Erin Bossard
Rosi Reed -‐ sPHENIX Collabora4on Mee4ng -‐ June 2017
11
Jet Energy Scale • For high momentum jets, the JES is
similar in pp and AA • Defect in the JES at low-‐pT in AA à
suspect cause is the crude exclusion seed selec4on – Low-‐pT (hard scakering) jets are
included in the es4mate of the background à over subtrac4ng
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� Mean value of: pT,reco / pT,truth � Determined by Gaussian fit
� Uses default simula4ons � Linear tower calibra4on à
assumed sampling frac4ons � no addi4onal jet-‐level
calibra4on
Erin Bossard
Erin Bossard
Rosi Reed -‐ sPHENIX Collabora4on Mee4ng -‐ June 2017
12
Jet Energy ResoluKon • In HI collisions JER increases with increasing R
• Rapidly increases for pT,truth ~ average background
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Erin Bossard
Erin Bossard
pp
AA
� Width of pT,reco / pT,truth distribu4on � Determined by Gaussian fit
Rosi Reed -‐ sPHENIX Collabora4on Mee4ng -‐ June 2017
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Embedding into HIJING (R =0.4 jets)
• Comparison of default and Al no readout – Versus pT,jet – Inclusive
9/20/17 Rosi Reed -‐ HCal 14
Raghav Kunnawalkam Elayavalli
Embedding into HIJING
• Inclusive jet observables in HI collisions follow the same trend as in PYTHIA studies
• For high pT jets, background has minimal effect
• Addi4onal smearing due to UE added in quadrature with smearing from reduced IHCAL could reduce analysis window
9/20/17 Rosi Reed -‐ HCal 15
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Outlook to CDR • Current sPHENIX design similarity to LHC experiments has allowed reasonable knowledge transfer
• There do not seem to be any gaping holes in the methods needed for compensa4ng for the background in HI collisions with respect to the design with any IHCAL configura4on discussed so far
• However, a fluctua4ng background with a fluctua4ng detector response can be complicated.
9/20/17 Rosi Reed -‐ HCal 16
Outlook to CDR • New performance plots with respect to the development that has taken place – Regenerate plots of JES/JER vs R and pT with the latest geometry
• Incorpora4on of JEWEL (a jet quenching model) will allow us to look at quenched versus non-‐quenched jets – Small difference between quark and gluon jets indicates this will not be a dominate effect
• Benchmark background subtrac4on methods versus different calorimeter systems
9/20/17 Rosi Reed -‐ HCal 17
Back Up
9/20/17 Rosi Reed -‐ HCal 18
HCAL Descoping – Jet perspecKve • What impact does each inner HCAL configura4on have on the JES and JER? – How much can we correct in unfolding?
• Do the configura4ons increase the bias with respect to fragmenta4on? – Quark vs Gluon jets – High z jets – Dis4nguishing modifica4on of the fragmenta4on
• How does this effect the background removal techniques in HI collisions?
• We want to push the kinema4c reach to create jet probes which overlap with LHC kinema4cs
9/20/17 Rosi Reed -‐ HCal 19
Inclusive Jet ResoluKon vs R
Different HCAL configura4ons have a minimal dependence on R for inclusive jets
9/20/17 Rosi Reed -‐ HCal 20
Songkyo Lee
• d
9/20/17 Rosi Reed -‐ HCal 21
Songkyo Lee
We can study effects/configura4ons with one or two R choices
Inclusive Jet ResoluKon vs R
FragmentaKon
• Inclusive jet performance shows minimal difference however, the impact on high-‐z or other “special” jets can be substan4al – Modifica4on of the fragmenta4on func4on is a key sPHENIX measure
– The ability to dis4nguish jet quenching effects from quark vs gluon will be important
• sPHENIX is a next genera4on detector and should be able to make next genera4on jet measurements
9/20/17 Rosi Reed -‐ HCal 22
Highest z Charged Hadron (π, K, p)
9/20/17 Rosi Reed -‐ HCal 23
Default
JES à 1.29 corr JER à 13.0%
Al IHCal
More punch through?
Al IHCal NO READOUT
100%/√(50) = 14.1%
Red -‐ all jets Black -‐ 0.2 < z < 0.4 Blue -‐ z > 0.6
JES à 1.29 corr JER à 13.1%
JES à 1.36 corr JER à 15.1% Jamie
Nagle
Correc4on of 1.29 indicates a Calo scale issue
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Entries 13082Mean 0.2838Mean y 41.42Std Dev 0.2153Std Dev y 6.095
JES/EM fracKon (SS310) JES Correc4on of 1.29 • CEMC energy scale set for EM
showers! For a jet with a high z π0 • Ereco ~ Etruth As EM frac4on decreases, Ereco decreases • IHCal inves4ga4ons as a
func4on of leading z hadron à walking up and down this curve
High peak in CEMC energy frac4on à “miscalculated” by using the EM energy scale to calculate the CEMC tower energy • Suppresses the correla4on with
reco jet energy
9/20/17 Rosi Reed -‐ HCal 24
Jamie Nagle
John Lajoie
Electron IdenKficaKon
• An4protonsà main source of fake electrons at low pT
• The worse case: low pT an4-‐protons steel frame example – Hadron rejec4on for 90% electron ID – Just E/p cut: 5.11+/-‐ 0.26 – 2D cut: 5.05 +/-‐ 0.25
9/20/17 Rosi Reed -‐ HCal 25
Sasha Lebedev
Set up – Jet Shape Observables • Analysis code à developed to study jets with forward instrumenta4on:
• Same PYTHIA 8 jets (R = 0.4, pT,jet > 50 GeV) • 3 Different reconstructed jets collec4ons – Primary Par4cle Jets -‐ No muons, neutrinos – Track Jets -‐ Tracks require ndf>60, χ2/ndf<1.5, DCA2D<0.1cm
– Calorimeter Tower Jets -‐ Require tower energy > 100 MeV • 3 condi4ons – SS310, Al, and Al without readout • “Matched” jets require track and tower jets match the primary jet within ΔR<0.3
9/20/17 Rosi Reed -‐ HCal 26
Jet Shape in HCAL
9/20/17 Rosi Reed -‐ HCal 27
Matched tower jets à Etower with respect to the jet axis
Inner HCAL Outer HCAL
Less energy in the inner HCAL and more in the outer HCAL with Al • Look at normalized distribu4ons to see whether shape changes
John Lajoie
Jet Shape in HCAL
9/20/17 Rosi Reed -‐ HCal 28
Matched tower jets à Etower with respect to the jet axis • Normalize by area and integral to look at the shape
Small difference in the shape in the inner HCAL between SS and Al à A likle broader, at a scale < R
Inner HCAL Outer HCAL
John Lajoie
Combined Jets • Combine the tower and track jets to use the best informa4on from both – Similar to par4cle flow à uses truth informa4on instead of a real clustering algorithm
• Point each track jet cons4tuent into the calorimeter, sum up the energy it contributed to the tower jet in each calorimeter segment
• Combine the tower and track jet informa4on: – Expected E/p resolu4on calculated using measured quan44es – If the ptrack resolu4on is beker than Etower resolu4on à add track to jet
– If the Etower resolu4on is beker, rescale ptrack to Etower, add track to jet
– Remaining Etower à“neutral energy” à add to jet 9/20/17 Rosi Reed -‐ HCal 29
9/20/17 Rosi Reed -‐ HCal 30
Tower JES/JER – degrada4on is visible but small compared to the SS310 baseline:
Tower Jets
Combined Jets
JES ResoluKon
SS310 0.744 9.3%
Al 0.724 9.8%
Al (no IHCAL)
0.691 10.7%
<neutral frac4on> >~0.33, due to CEMC energy scale?
Jet Energy Scale
John Lajoie
9/20/17 Rosi Reed -‐ HCal 31
Use the “black hole” to add back E within R=0.4 of the combined jet axis
Shape of the low side largely remains the same? • Low side tail not due to leakage? • Imperfec4ons in combina4on algorithm?
• Jet axis resolu4on?
AccounKng for Leakage
John Lajoie
Default
Al IHCal
Al IHCal NO READOUT
Jet Flavor/FragmentaKon Bias I
9/20/17 Rosi Reed -‐ HCal 32
light quarks
gluons
Light Quarks Gluons JES Resolu4on JES Resolu4on
SS310 0.749 9.4% 0.722 8.0%
Al 0.727 9.7% 0.702 9.0%
Al (no IHCAL)
0.694 10.7% 0.671 10.0%
• Separate response for light quark (u+d) and gluon jets • Require Eparton >50% Ejet
• JES is a few % lower for gluon jets than for quark jets à JER is a bit beker
• The difference between q/g jets is ~ to the difference between SS310 and Al.
Tower Jets John Lajoie
Embedding into HIJING
• Chris has produced HIJING Files for embedding: – 0-‐4 fm: /sphenix/data/data02/rescope-‐2017-‐09-‐08/inner_hcal_al/sHijing/fm_0-‐4
– Other b ranges (0-‐12, 5-‐9, 9-‐11): /sphenix/data/data02/rescope-‐2017-‐09-‐08/inner_hcal_al/sHijing/fm_<b range>/
• JER is degraded due to fluctua4ng background • JES correc4on via background subtrac4on is necessary – Atlas itera4ve rou4ne subtracts layer by layer à How do descoping op4ons effect this?
9/20/17 Rosi Reed -‐ HCal 33
Conclusions • The differences between SS, Al and Al without read-‐out – Not large for inclusive jet observables
• Including first look at embedded jets – Does not have much R dependence – Can maker for fragmenta4on/flavor analyses
• JES difference for q/g ~ SS310/Al difference • Need to to properly set the CEMC energy scale • Combined jets show a proper PF algo might get the JES close to 1 – Leakage is s4ll an issue
9/20/17 Rosi Reed -‐ HCal 34
Concerns/Thoughts • We should combine 85% EMCal + descoped HCAL – Could simply cut on |ηjet|<0.85-‐R – We have an increase in sta4s4cs due to addi4onal years, but will lose on the acceptance
• Need clear communica4on over default and other poten4al configura4ons – Understanding Calo/Tracking even for the default
• Person-‐power as always • Jet-‐trees will be produced for pp/AA – Help with person-‐power – Keep details consistent
9/20/17 Rosi Reed -‐ HCal 35
Back-‐up
9/20/17 Rosi Reed -‐ HCal 36
Some thoughts
• Simula4ons have become increasingly realis4c – Great progress, and indica4ons are that simpler simula4ons were reasonable
• However, addi4onal development both in the simula4ons and our understanding is vital – Even without descoping – We also do not know how more realis4c simula4ons will affect the response 9/20/17 Rosi Reed -‐ HCal 37
JES/EM fracKon (SS310) Reco jet energy vs. reco jet EM fracKon
9/20/17 Rosi Reed -‐ HCal 38
The CEMC energy frac4on is peaked highà “miscalculated” by using the EM energy scale to calculate the CEMC tower energy. • Suppresses the correla4on with reco jet energy.
John Lajoie
Jet Response vs z (π+,π-‐)
•
• Mean +/-‐ RMS • Shiz in response visible here, some z dependence
• But this not the full story
9/20/17 Rosi Reed -‐ HCal 39
z =pTruthT ,particle
pTruthT , jet
Highest z Charged Hadron (π, K, p) R = 0.4
9/20/17 Rosi Reed -‐ HCal 40 Inclusive jets, jets with 0.2 < z < 0.4, and jets with z > 0.6.
Jamie Nagle
Combined Jets • Combine the tower and track jets to use the best informa4on from both:
– Analysis code includes bookeeping of par4cle energy contribu4on to calorimeter tower energy • This uses truth informa4on (think of it as perfect clustering/cluster spli{ng)
– Point each track jet cons4tuent into the calorimeter, sum up the energy it contributed to the tower jet in each calorimeter segment
– Combine the tower and track jet informa4on: • Expected energy/momentum resolu4on calculated using measured quan44es:
– Track momentum resolu4on δpT /pT = 0.005 + (0.001*pT) – Sort EM/hadronic par4cles by CEMC tower energy frac4on > 0.9 – CEMC resolu4on 0.12/sqrt(E) for EM par4cles,
CEMC+HCAL resolu4on 0.15 + 0.7/sqrt(E) for hadrons • If the track momentum resolu4on is beker than the tower resolu4on, add the track to
the combined jet • If the calorimeter energy resolu4on is beker, rescale the track total momentum to match
the tower energy. – Improves energy resolu4on but keeps improved poin4ng resolu4on of tracking (eta,phi)
• Remaining tower energy azer all par4cles is “neutral energy” and is added to the combined jet.
– This is similar to a par4cle flow algorithm, with the excep4on that it uses truth informa4on instead of a real clustering/cluster spli{ng algorithm
– Gives an idea of what is the best you could possibly do, or how much informa4on is in principle available for you to take advantage of • Leakage out the back is a loss of informa4on.
9/20/17 Rosi Reed -‐ HCal 41
Jet Flavor/FragmentaKon Bias II
9/20/17 Rosi Reed -‐ HCal 42
light quarks
gluons
Combined jets show a slightly different response for quarks and gluons (missing soz hadron tracks?)
Combined Jets
Comparison with “old” results
• JES has shized downwards with new default – Old: 0.83+/-‐0.09 – New: 0.78 +/-‐ 0.10
9/20/17 Rosi Reed -‐ HCal 43
Jet Response • For high pT jets, it seem the default and the Al are not so different – On average
• Looks similar to Ragav’s trend
• Compare: – Default: 0.78 +/-‐ 0.10
– Al: 0.78+/-‐0.10 – Al no readout: 7.4 +/-‐0.11
9/20/17 Rosi Reed -‐ HCal 44
Jet Shape II
9/20/17 Rosi Reed -‐ HCal 45
For matched tower jets, look at the distribu4on of tower energies with respect to the jet axis. Normalize the Al distribu4on to the SS310 integral to look at the shape.
Inner HCAL Outer HCAL
There is a small difference in shape for the inner HCAL, energy distribu4on pushed out a likle, but at a scale that is smaller than the jet reconstruc4on radius.
Larger Jet Radius
9/20/17 Rosi Reed -‐ HCal 46
Combined jets, re-‐run with R=0.8 for comparison – likle change.
Combined Combined + BH
With the R=0.8 the BH seems to pick up a likle more energy.
η/φ ResoluKon
9/20/17 Rosi Reed -‐ HCal 47
Nothing special here, this just shows the improved η/φ resolu4on of the combined just by using the tracking direc4on and the calorimeter energy.