IAS Program on High Energy Physics, Jan 12, 2017
Top-TaggingattheEnergyFrontier
MinhoSon
KAIST
WorkinprogresswithZhenyuHanandBrockTweedie
jet
q
jet
q’
q
q’
jet
b
Slowly moving top
Fastly moving top
p" ∼ O(sub − TeV)
b
jet
q
q’ Almost QCD-like jet
b
Super-Fastly moving top
p" ∼ O(afew×10TeV)
q
q’
jet
b
Fastly moving top
p" ∼ O(sub − TeV)
Sub-TeV top-tagging is sort of well-established
q
How would top-tagging performance
evolve with much higher 𝑝6 ?
q’ Almost QCD-like jet
b
Super-Fastly moving top
p" ∼ O(afew×10TeV)
Many challenges arise as tops enter into
hyper-boosted regime
Instability from soft radiation
QCD-jet
Pert.Emission
neartheboundary
QCD-jet
𝒑𝑻 ∼ 𝟔𝐓𝐞𝐕
𝒑𝒔𝒐𝒇𝒕
∼ 𝟓𝐆𝐞𝐕
𝑻
𝑹∼𝟏
Spuriousmassscale
𝒔𝒐𝒇𝒕
𝒎𝟐 ∼ 𝒑𝑻 𝒑𝑻
𝑹𝟐 ∼ 𝒎𝟐𝒕𝒐𝒑
Borrowed a discussion from Larkoski, Maltoni, Selvaggi 2015
Instability from soft radiation
Top-jet
Top-jet
𝒑𝑻
ContaminationfromISR
𝒑𝑰𝑺𝑹
𝑻
Borrowed a discussion from Larkoski,
Maltoni, Selvaggi 2015
𝑹∼𝟏
Fluctuationoftop-jetmassforFIXED cone
𝟐
𝟐
𝒎𝟐 ∼ 𝒎𝟐𝒕𝒐𝒑 + 𝒑𝑻 𝒑𝑰𝑺𝑹
𝑻 𝑹 ∼ 𝑶 𝟏 ×𝒎 𝒕𝒐𝒑
If
𝒑𝑰𝑺𝑹
𝑻
𝒎𝟐𝒕𝒐𝒑
∼
𝒑𝑻 𝑹𝟐
∼ 𝟓𝟎𝐆𝐞𝐕if
𝒑𝑻 ∼ 𝐟𝐞𝐰×𝒎𝒕𝒐𝒑
Moderately boosted
∼ 𝟓𝐆𝐞𝐕if 𝒑𝑻 ∼ 𝐟𝐞𝐰×𝒎𝒕𝒐𝒑 ×𝟏𝟎
Hyper-boosted
Instability from soft radiation vs Shrinking jet size
Top-jet
Top-jet
𝒑𝑻
ContaminationfromISR
𝒑𝑰𝑺𝑹
𝑻
𝑹 ∼ #/𝒑𝑻
Krohn, Thaler,Wang2009
Han2014
Larkoski,Maltoni,Selvaggi 2015
Fluctuationoftop-jetmassforSHRINKING cone
𝟐
𝟐
𝒎𝟐 ∼ 𝒎𝟐𝒕𝒐𝒑 + 𝒑𝑻 𝒑𝑰𝑺𝑹
𝑻 𝑹 ∼ 𝒎 𝒕𝒐𝒑
𝑰𝑺𝑹
𝒑
𝟏 + 𝜷𝟐𝑹 𝑻
𝒑𝑻
Withshrinkingcone
𝒎𝒕𝒐𝒑
𝑹 ∼ 𝜷𝑹
,
𝒑𝑻
𝐞. 𝐠.𝜷𝑹~𝟒
EW-strahlung at high pT
QCD-jet
𝒑𝑻
W/Z-emission
QCD-jet
𝑾/𝒁
E.g. ∼ 6% at 5 TeV quark-jet (unpolarized)
Splitting functions (momentum integrated)
𝜶 𝟏+ 𝟏−𝒙
𝑷𝒒→𝑾𝑻 ∼ 𝑬𝑾
𝝅
𝒙
𝑷𝒒→𝑾𝑳 ∼
𝜶𝑬𝑾 𝟏 − 𝒙
𝝅
𝒙
𝟐
𝒑𝟐𝑻
𝐋𝐨𝐠
𝟏 − 𝒙 𝒎𝟐𝑾
Dead cone, FSR, and shrinking cone
𝑹𝒅𝒆𝒂𝒅𝒄𝒐𝒏𝒆 ∼
𝟐𝒎𝒕𝒐𝒑
𝒑𝑻
Deadconecapturestopdecayproducts
,butnoradiationfromtop.Relevantforsuccessfultop
tagging
𝐸. 𝑔. 𝑋 → 𝑡𝑡̅
G. Salam, talk given at
LHC New Physics Forum, IWH, Heidelberg, 23-26 Feb, 2009
𝑋
𝑡
CapturingFSRbeforedecayisimportantto
reconstructthecorrectresonancemass
wheretopsweredecayedfrom
∼ 0.43𝛼k ln 𝑅opq forquark-jet
Salam2010
‘TowardsJetography’
Instrumental challenge
Detectorgranularityisbecomingabigproblem.
ATLAS/CMS
hasthreelayersofmainsub-detectors
One𝐇𝐂𝐀𝐋 cell
0.1x0.1
Typical jet
R=0.5
One𝐄𝐂𝐀𝐋 cell
0.02x0.02
Instrumental challenge
Detectorgranularityisbecomingabigproblem.
Cluster of
’many ’ CAL cells
0.5 jet from W
0.5 jet from W
jet
Top-quark
0.5 b-jet
b-jet
q
b
jet
q’
Slowly
moving top
Instrumental challenge
Detectorgranularityisbecomingabigproblem.
ATLAS/CMS
hasthreelayersofmainsub-detectors
0.5 jet
from etal13’
W
Spannowsky
One𝐇𝐂𝐀𝐋 cell
0.1x0.1
0.5 jet from W
Top-quark
0.5 b-jet
One𝐄𝐂𝐀𝐋 cell
0.02x0.02
Instrumental challenge
Detectorgranularityisbecomingabigproblem.
ATLAS/CMS
hasthreelayersofmainsub-detectors
0.5 jet from W
One𝐇𝐂𝐀𝐋 cell
0.1x0.1
0.5 jet from W
Top-quark
0.5 b-jet
One𝐄𝐂𝐀𝐋 cell
0.02x0.02
FCC (Future Circular Collider)
FCC-hh (CERN),CEPC(China)
100 TeV collider
∼ 7x upgrade of CM energy
E.g.3TeV topatthe
LHC wouldexpect~20
TeV topsat100TeV
Current proposal
for the future detector
𝐄𝐂𝐀𝐋, 𝐇𝐂𝐀𝐋
𝐓𝐫𝐚𝐜𝐤𝐞𝐫
2x
4x
14TeV
Looks like the detector technology can not catch up with
the energy upgrade
Capability
attheLHC
+
FCC
proposal
Understanding our current detector better
is a KEY-ingredient to predict our future
capability
→
Capability
attheFCC
ExistingLiterature
Katz,MS,Tweedie,Spethmann 2011,2012
Snowmass2013
Schaetzel,Spannowsky 2013
CMSPASJME-14-0022014
Spannowsky,Stoll2015
Larkoski,Maltoni,Selvaggi 2015
….
*Listedonly studiesonW/Z/H/tops-taggers
Outline
WewillfocusonJHUTopTagger +N-subjettiness
1. Optimize JHU TopTagger + N-subjettiness at particle level
We will newly show that N-subjettiness is not just an alternative to other top-taggers,
but it adds a new information to improve top/gluon discrimination
2. Introduce various detector models
We will illustrate how one can combine information, scattered in here and there in subdetectors, to extract a meaningful result
3. Optimize JHU TopTagger + N-subjettiness in various
detector models
This step will establish the “robustness of shape variables vs declustering variables
against different detector configurations”
Top-jetsize
JHU TopTagger with CMS type cuts
𝑅opq = 𝛽Ž ×
Top
Ateachbranch,
𝑚q
𝑝6
€‚ oƒ
‚ q„€opq
‡
𝛽… × € ˆ ∶minangulardist.
‚
𝛿€ = €
𝛿… =
cell
𝒋𝒕𝒐𝒑
𝒋𝟏
Firstiteration
𝒋𝟏
𝒋𝟐
𝒋𝟐𝟏 𝒋𝟐𝟐
Hardsplitting
Softsplitting
cell
𝒋𝟏𝟏
Seconditeration
𝒋𝟏𝟏 𝒋𝟏𝟐
𝒋𝟐
cell cell
cell
𝒋𝟏𝟐
cell cell cell cell
cell cell
cell
subjet 3
subjet 1 subjet 2
3 (or 4)subjets
Cutsontwovariables:𝑚‡Œ• ,𝑚q„€
*Insteadofm• andcosθ intheoriginalJHUTopTagger
N-subjettiness
• exploitsradiationpatternaround Nsubjet axes
min ∑ 𝑝6 𝑖 min Δ𝑅 𝑖, 𝑗œ› , … . , Δ𝑅 𝑖, 𝑗œ•
𝜏• ≡
∑𝑝6 𝑖 𝑅
Weightedsumoverconsitituent’s pT
:smallerweight,Δ𝑅(𝑖, 𝚥̂),forsmaller
distance.Preferstobesmallforthe
rightnumber ofaxesfound
Thaler,TilburgJHEP1103
Top:threelocalizedenergyclusters
N-subjettiness
Thaler,TilburgJHEP1103
• exploitsradiationpatternaround Nsubjet axes
min ∑ 𝑝6 𝑖 min Δ𝑅 𝑖, 𝑗œ› , … . , Δ𝑅 𝑖, 𝑗œ•
𝜏• ≡
∑𝑝6 𝑖 𝑅
Weightedsumoverconsitituent’s pT
:smallerweight,Δ𝑅(𝑖, 𝚥̂),forsmaller
distance.Preferstobesmallforthe
rightnumber ofaxesfound
Thaler,TilburgJHEP1103
Top:threelocalizedenergyclusters
N-subjettiness
Thaler,TilburgJHEP1103
• exploitsradiationpatternaround Nsubjet axes
min ∑ 𝑝6 𝑖 min Δ𝑅 𝑖, 𝑗œ› , … . , Δ𝑅 𝑖, 𝑗œ•
𝜏• ≡
∑𝑝6 𝑖 𝑅
Thaler,TilburgJHEP1103
ü N-subjettiness is qualitatively different from other top taggers based on mass/pT-drops and it
has been introduced as an alternative for top tagger
ü We observe that combining other top taggers with N-subjettiness can give 𝑂(1) improvement
in top/gluon discrimination
Forsimilardiscussion,CMSPASJME-13-007,Adamsetal15’
Optimization
JHU Top-tagger with CMS-type cuts
& N-subjettiness
Clustering/declustering/cutparameter
𝑅¡¢£¤¥¦£ = 1.0
‡
𝑅opq ≡ 𝛽Ž × € ˆ:Shrinking jet-conesize
‚
𝛿€ :pT asymmetrycut
𝑚‡Œ• :minjetpairmass
‡
,𝛿… ≡ 𝛽… × € ˆ :minangularseparation
‚
𝑚q„€ :reco- topmass
𝜏¾¿ ≡ 𝜏¾ /𝜏¿:N-subjettiness
Optimizationoversevenparameters
Tag/mistag Rate≡ #§¨©ª¤ª«¬£-£®««¢¬
#¯«¢«©°£«¬±¤£®›%³"±¤¢¬-±
Signal:continuum 𝑡𝑡̅ → 𝜇 + 𝑗𝑒𝑡𝑠
Quark/gluon: 𝑞𝑍 → 𝑞 𝜈𝜈̅ , 𝑔𝑍 → 𝑔(𝜈𝜈̅ )
:samplesarerestrictedto 𝜂 < 1.0,𝑝6 = [𝑝6 − 1%, 𝑝6 + 1%] GeV
Top/gluon/quark discrimination at particle level
Withgluon-optimized
parameters
Flavordependentoptimizations:
Withquark-optimized
parameters
N-subjettiness dominates
JHU/CMS tagger dominates
𝛽Ž ∼ 4, 𝛽… ∼ 0.7, 𝛿 … ∼ 0.03 forrelevanttagefficiencies
•
Simultaneous optimizations of the quark and gluon jets are possible
•
N-subjettiness adds extra discriminating power for gluon-jets, not quark-jets
Top/gluon discrimination at particle level
𝑝6 -dependentoptimizationsontop/gluon-jets:
Twoseparateoptimizations: JHUwithCMS-typecutswithout vswithN-subjettiness (combined tagger)
Nearly scale-invariant
Better performance due
to N-subjettiness for
gluon-jets
Optimizedparametersareroughlyunchanged,e.g.optimized𝛽Ž and𝛽… stayfixed,simple ∼ 1/𝑝6 scalingworks
Introducingdetectoreffect
Whatisagooddetectormodel?
Itistheonethatminimallybreaksthe‘scaleinvariance’and
bringstheresultbacktoourexpectationatthe‘particle-level’
Introducingdetectoreffect
Whiletherealdetectorsareinsanely complicated,ourtoydetectormodel wouldcatchthe
leading effects.However, weareaiming tobeasclosetotherealityaspossible
HCALcellsizeservesasacut-off inmanypheno- studies
q RawHCAL
Final state particles
Schaetzel, Spannowsky 2013
Introducingdetectoreffect
Whiletherealdetectorsareinsanely complicated,ourtoydetectormodel wouldcatchthe
leading effects.However, weareaiming tobeasclosetotherealityaspossible
Finalstateparticlesintothreedifferentsub-detectors
:rawcalorimetercellsasinputsfor jetclustering
q RawECAL&HCAL
Hadrons
Photons, nonisolated electrons
Muons, isolated
electrons
Toydetectormodels
Cartoonic picture of our toy detector model
𝜋
𝜋
𝜋
ü Use every bit of information from
three layers of sub-detectors
𝜋
Repeat with trackers
(track flow,particle flow)
Katz,MS,Spethmann,Tweedie,2011,2012(SeeAppendicesof1010.5253/1204.0525)
Toydetectormodels
Combining information is not unique
Toydetectormodels
Combining information is not unique
q EM-flow
ECALsarelocallyrescaledtotheenergy ofthefull
calorimeter, andHCALcellsdiscarded
Katz,MS,Spethmann,Tweedie2011,2012
(SeeAppendicesof1010.5253/1204.0525)
RescaleECALcellsby
ÂÃÄÅÆ ÇÂÈÄÅÆ
ÂÃÄÅÆ
EÊË¡Ì
›
EÂË¡Ì
¿
EÂË¡Ì
Detectorwith
ECAL&HCAL
E › ′ÂË¡Ì
E ¿ ′ÂË¡Ì
Detectorwithonly
rescaledECAL
*RescaledECALcellsareinputforthejetclustering
Toydetectormodels
Combining information is not unique
q EM-flow
ECALsarelocallyrescaledtotheenergy ofthefull
calorimeter, andHCALcellsdiscarded
Katz,MS,Spethmann,Tweedie2011,2012
q Track-flow
RescaleECALcellsby
Similarlyrescaletracksby
Schatzel, Spannowsky 2014
Larkoski,Maltoni,Selvaggi 2015
q Particle-flow
Rescaletracksby
ÂÃÄÅÆ ÇÂÈÄÅÆ
ÂÃÄÅÆ
ÂÃÄÅÆ ÇÂÈÄÅÆ
ÂÎÏÐÑÒÓ
ÂÈÄÅÆ
andleaveEÂË¡Ì
ÂÎÏÐÑÒÓ
as-is
*PERFECTtrackingefficiencyisassumed.Realityisworsethanthisperfectcase
Cartoon
Pseudo-CMStypeEvent
q EM-flow
q Track-flow
q Particle-flow
Two crucial detector effects added to be more realistic
1.Energy-smearingintonearbycalorimetercells
2.HadronsdeposittheirenergiesinECALcells
Unlike the situation in this cartoon, hadrons
have O(1) chance to leave their energies
(e.g. via Nuclear interaction) in ECAL
before reaching HCAL.
O(20%) of jet energy becomes absorbed in
the ECAL in this manner
Two crucial detector effects added to be more realistic
1.Energy-smearingintonearbycalorimetercells
2.HadronsdeposittheirenergiesinECALcells
GEANT4
• ECALsmearing pattern/hadron-energy-deposit-in-ECAL willbesimulated
withGEANT4whereasHCALsmearingpatternwillbedonebysimpleansatz
UpgradedversionofMS,Spethmann,Tweedie2012(SeeAppendix of1204.0525)
EnergysmearingintonearbyECALcells
ü Themostimportant ingredient inourdetectormodel
Aparticlehitting
singleECALcell
±
𝜋
5x5ECALcellsunderneath oneHCALcell
𝟐. 𝟐𝐜𝐦
𝟐𝟐𝐜𝐦
𝐏𝐛𝐖𝐎𝟒(𝐂𝐌𝐒)
EnergysmearingintonearbyECALcells
Idealsituation
NOsmearing
±
𝜋
:allenergyisdeposited
inasingleECALcell
5x5ECALarrays
EnergysmearingintonearbyECALcells
Inreality
Smearing
±
𝜋
:energyissmearedinto
nearbyECALcells
ü Sensitivetojetsubstructure
variables
Lightercolorrepresentsless energydeposit
5x5ECALarrays
Smearing effectbecomesextremelyimportant injetsubstructureanalysisof
thehyper-boosted heavyparticles(e.g.top/H/Z/W)
WesimulateECALsmearingbyGEANT
1.
2.
3.
Prepare9x9ECALcellswithsamedimensionasCMSECAL
Shootsingle𝑒 ± , 𝜋 ± beamsonto ECALrepeatedly
Buildupalibraryofshoweringprofilesfor𝑒, 𝜋 beams
ü e-inducedshowersasproxiesfor e andγ
ü 𝜋-inducedshowersasproxyfor allhadrons
Energyisfixedtobe100GeV
𝑒 ±, 𝜋 ±
q ParticlehittingaECALcellisreplacedwitha
randomlychosensmearingprofilefromthe
library
*Correlationbetweencellsareautomaticallyfoldedin
5x5ECALarrays
WesimulateECALsmearingbyGEANT
singleECALcell
𝐈𝐦𝐩𝐚𝐜𝐭𝐩𝐨𝐢𝐧𝐭
𝑒 ±, 𝜋 ±
ü
Impactpointisnotalwaysatthecenterof
ECALcell.Itleadstoasymmetricpattern.
Wesub-divide ECALinto9x9=81sub-cells
totakeintoaccountasymmetricshowering
pattern
5x5ECALarrays
- Wedonotsimulateasymmetricdetectorgeometry,e.g.particlecanhitacellwithanangle
Electron-inducedECALshoweringpatternbyGEANT
𝟏𝟎𝐆𝐞𝐕𝒆¥ beam
𝟏𝟎𝟎𝐆𝐞𝐕𝒆¥ beam
Eâ«ãã/E¤¢â¤¬«¢£«ã«â£©-¢,notw.r.tE£-£°ã¬«³-§¤£
- NearlypT-independent.Itjustifiesourproxiessimulatedat100GeV
Pion-inducedECALshoweringpatternbyGEANT
𝟏𝟎𝟎𝐆𝐞𝐕𝝅± beam
3𝐓𝐞𝐕𝝅± beam
Eâ«ãã/E¤¢â¤¬«¢£³¤-¢,notw.r.tE£-£°ã¬«³-§¤£
- NearlypT-independent.Itjustifiesourproxiessimulatedat100GeV
ProfileansatzforHCAL
𝐇𝐂𝐀𝐋𝐜𝐞𝐥𝐥
𝟓×𝟓𝐄𝐂𝐀𝐋𝐜𝐞𝐥𝐥𝐬
2𝑟
𝑓 𝑟 ∝ ¿
𝑟 + 𝑅¿
𝑒 ±, 𝜋 ±
𝐸¤¢
𝐸-¨£
¿
75%containmentinacentrallystruckcell
95%within 3x3arrayaboutit
Grindhammer,Rudowicz,Peters1990
CMSNOTE2006-138
ReplaceallparticlesflowingoutthebackofanECALcellwitha
continuousangularenergydistributionaccordingtotheaboveansatz
Spuriousstructureduetosmearing
Smearing intonearbycellscanintroduce spurious structurewhena rescaling
isdone withineachHCALcell
Mini-jetclustering
ü dealswithHCALenergyspreading:
e.g.inEM-flow,theentirecollectionofECALandHCALcellsareclustered
intomini-jetswiththeanti-𝒌𝑻 algorithm withthesizecomparabletothe
HCALsize.Rescalingiscarriedoutwithineachmini-jet
𝐄𝐂𝐀𝐋
𝐇𝐂𝐀𝐋
Validation of our approach against CMS high pT W-jet
CMSPASJME-14-002
With no trackers
With perfect trackers
Threebenchmarkscenarios
Model
Tracking:
twoextremes
LHC
ECAL
material
ECALcell
HCAL cell
CMS-type
(PbWOú )
0.02× 0.02
0.1× 0.1
FCC1
Perfect/absent
PbWOú
(Leadtungstate)
0.01× 0.01
0.05× 0.05
FCC2
Perfect/absent
PureW
(Tungsten)
0.005× 0.005
0.05× 0.05
q RawECAL&HCAL
We will see how these detector models
perform in three benchmark LHC/FCC
detectors
q EM-flow
q Track-flow
q Particle-flow
q Particle-level
-
EffectiveMoliereradiusofpureWisbiggerthanwhatisassumed.ConsiderPureWasaplace-holder
foranynewmaterialwithahalf-sizedeffectiveMoliereradius
Filteredtop-jetmass & 𝝉𝟑𝟐 of10TeVtop/gluonatFCC1
: equivalentsituation to5TeVtop/gluon attheLHC
-
pile-upandmagneticfieldarenotincluded inthisstudy
N-subjettiness is doing great
whenever tracks are available
𝜏¾¿ seems to probe a property within JHU/CMS
subjets, rather than in-between them
5TeVtop/gluondiscriminationatFCC1
:equivalentto2.5TeV top/gluon-jetsattheLHC
• Particle-flow is universally the best option (as it should be)
• Track-flow works better with N-subjettiness, and EM-flow is less effective at
capitalizing on N-subjettiness
gluon mistag rate
Gluon, at 50% top-tag rate (detector level)
τ32+mJ
JHU/CMS
combined
0.1
raw ECAL & HCAL
EM-flow
→ FCC2
track-flow
particle-flow
→ FCC2
particle-level
0.01
1
10
1
FCC1
FCC2
𝐄𝐂𝐀𝐋𝟐𝐱, 𝐇𝐂𝐀𝐋𝟐𝐱
𝐄𝐂𝐀𝐋𝟒𝐱, 𝐇𝐂𝐀𝐋𝟐𝐱
comparedtoCMS-typeECAL,HCAL
10
1
10
p (TeV)
T
•
•
JHU/CMS tagger never fully competitive with N-subjettiness (except for EM-flow at 10TeV)
Combined tagger is universally better
ü FCC2 brings EM-flow, particle-flow to the similar level of half-𝑝6 jets at FCC1
Comparisontoanexistingstudyusingtrack-basedvariables
Larkoski,Maltoni,Selvaggi 2015
*WefirstvalidatedourprocedurebyreproducingLarkoski etal.
When tracks are not available, JHU/CMS tagger does most job
When tracks are available, 𝜏¾¿ does most job
Comparisontoanexistingstudyusingtrack-basedvariables
Larkoski,Maltoni,Selvaggi 2015
*WefirstvalidatedourprocedurebyreproducingLarkoski etal.
Perfect (solid red) vs. imperfect
(solid black) tracking
Note that Larkoski et al. (dotted black)
scaned over 𝜏¾¿ with the fixed jet mass window
ECAL 2x
EM-flow can cover up to 20
TeV at FCC2 ∼ 10TeV at FCC1
StrongMagnetsatFCC
ü Beneficialtohigh-𝑝6 physics.Ithurtslow-𝑝6 physics
𝑝 6ÿ…Œq = 0.15×
B
r
× ÿ#$
T
𝑚
CMS:4T,1.5m
FCC:6T,6m
~0.9GeV
~5.4GeV
• Thisimpliesthat𝑂(100GeV) processsuchasHiggs physicsbecomeslow-𝑝6
physicsat100TeV!
E.g.𝐻 → 𝑏𝑏' withlow𝑝6 willbesignificantly under-reconstructed duetolost
tracks(Weneedtomakesurethatwearecapableofrestoringthelosttracksbacktoour
jetsviatrackreconstruction,e.g.particle-flow)
Inasituationthatstrong magneticfield becomesproblematic, ithurtshigh-𝑝6 tracking
efficiency,but
EM-flowisinsensitivetothisissue
Toconclude
q TheperformanceofouroptimizationofJHUTopTagger combinedwithNsubjettiness
1.
2.
3.
4.
Quark- andgluon-jetscanbesimultaneouslyoptimizedwithinJHUTopTagger
AddingN-subjettiness toe.g.JHUTopTagger,canmake𝑂(1) improvementof
top/gluondiscrimination
N-subjettiness iseffectivewhentracksareavailable
JHUismorerobustthanN-subjettiness undermorepessimisticdetectorassumptions
q EM-flowlooksverypromising.Itcansolelycoverupto20TeVtopsassuming
FCC2configuration(ECAL4x,HCAL2x)
1. Trackersbecomecrucialtotagtopsbeyond it
2. UnlesstheFCCdetectorsareconstructedwithnear-perfecttrackers,someadditional
investmentinECALgranularitywouldbebeneficial