Tra racking Hyper Bo cking Hyper Boosted sted Top Q p Qua uarks - PowerPoint PPT Presentation

Tra racking Hyper Bo cking Hyper Boosted sted Top Q p Qua uarks @ 100 T rks @ 100 TeV eV Michel Mi chele Sel e Selva vaggi ggi (CP3) (CP3) An Andr drew w Lar Larko koski ski (MIT), Fabi abio Mal altoni (CP CP3) Flavo vor r and Top Ph Phys ysics @ @ 100 100 TeV Work rkshop , 2015 2015 12 , 2015 2015 Beijin Be ijing – J – Jan anuar ary 12 Be Beijin ijing – J – Jan anuar ary 12 12

Why Why boosted boosted tops tops ? • Interest for a 100 TeV p-p collider is increasing • Would potentially be able to look for undiscovered particles up to tens of TeV masses • These heavy resonances will decay to highly boosted top qua p quarks ks, W/Z bosons, H ... • Several techniques for identifying jet sub-structure exist, and are widely used in ATLAS and CMS Do currently used techniques work at the Terascale? Can we think of some observables that can help? Can we set constraints on future detectors?

Boosted tops Boosted tops min. distance to resolve two partons: ∆R ≈ 2 m / p T ex for top: p T = 200 GeV → R ~ 2 p T = 1 TeV → R ~ 0.4 p T = 10 TeV → R ~ 0.05

Techniques echniques on on the the market market • Jet Mass • N-subjettiness Thale aler, V , Van an T Tilb ilburg 1011.2268 1011.2268 • Grooming (pruning, trimming) ● Shap ape Krohn e t al. 0912.1342 et al. 0912.1342 ● Kin inemat matic ics • CMS/JHU Top Tagger CMS-PAS-JME13-007 ● Sof oft r remov moval al • HepTopTagger Plehn, Spannowsky 1112.4441 • Event deconstruction Soper, Spannowsky 1402.1189 • Neural Networks Almeida et al. 1501.05968

Event Event display display

Analysis Analysis Setup Setup • MadGraph5 (LO event generation) q q → q q (bkg) g g → g g (bkg) p p → t had t had (signal) • Detector simulation: DELPHES (more later and back-up) - CMS (present) - SppC-FCC (future) • Look at observable shapes (not total event rate)

Na Naive Ana ive Analysis lysis

Jet et Mass Mass • Naive approach, do p T ~ ~ 1 T 1 TeV eV what works at the LHC • Reconstruct “fat - jets”

Jet et Mass Mass • Naive approach, do p T ~ ~ 3 T 3 TeV eV what works at the LHC • Reconstruct “fat – jets” Mass gets shifted towards higher values

Jet et Mass Mass • Naive approach, do p T ~ ~ 5 T 5 TeV eV what works at the LHC • Reconstruct “fat – jets” Mass gets shifted towards higher values

Jet et Mass Mass • Naive approach, do p T ~ ~ 10 T 10 TeV eV what works at the LHC • Reconstruct “fat - jets” Mass gets shifted towards higher values

Soft Emissions Soft Emissions We are clustering very confined decay products ΔR ~ 0.05 with a large cone size R= 1.0 Soft QCD emissions can produce large contributions to the jet mass: e.g. 5 GeV emission at the edge of the cone, for jet p T = 5 TeV adds m top to the jet mass !!

Soft Emissions Soft Emissions ● Effect on jet p T from ISR/U ISR/UE goes like R 2 assuming uniform density/area → jet mass ~ R 2 ● Top FSR also contributes outside the dead-cone region, R d.c ~ m t / p T

Soft Emissions Soft Emissions ● Best choice seems to choose a jet radius, big enough to contain top decay products, small enough to reject soft contamination: R ~ m t / p T ( we take 4 m / p T )

Jet et Mass Mass (shrinking shrinking cone) cone) p T ~ ~ 1 T 1 TeV eV Prescription: • Cluster jets with fixed size R = 1.0, derive jet p T • Re-cluster “proto-jet” constituents with R = 4 mt / p T , keep hardest.

Jet et Mass Mass (shrinking shrinking cone) cone) p T ~ ~ 3 T 3 TeV eV Distributions overlap with increasing p T Due to increasing boost, decay products, begin to merge into single calo-cells, hence worsening mass resolution

Jet et Mass Mass (shrinking shrinking cone) cone) p T ~ ~ 5 T 5 TeV eV Distributions overlap with increasing p T Due to increasing boost, decay products, begin to merge into single calo-cells, hence worsening mass resolution

Jet et Mass Mass (shrinking shrinking cone) cone) p T ~ ~ 8 T 8 TeV eV Distributions overlap with increasing p T Eventually jet cone size become comparable to calo cell size

Jet et Mass Mass (shrinking shrinking cone) cone) p T ~ ~ 10 T 10 TeV eV Distributions overlap with increasing p T Eventually jet cone size become comparable to calo cell size

Detector considerations Detector considerations From the exp. persepective, boosted analysis relies on: • go good a d angul ngular r res esolut ution • good energy/momentum resolution • ex for CMS: Tracking → ∆R ~ 0.002 ∆p/p ~ 5-10% @1TeV ECAL → ∆R ~ 0.02 ∆E/E ~1% @1TeV HCAL → ∆R ~ 0.1 ∆E/E ~5% @1TeV Charged Tracks will play a major role jet structure ID in highly boosted regimes

Detector Detector considerations considerations ● Make maximal use of measured information on charged particles (for better angular resolution, more robust against pile-up) ● Look at observables built on tracking (or Particle-Flow) ● Modify DELPHES tracking to make it more realistic in a dense environment (efficiency drop if track appears to be close to the jet core, angular smearing)

Tra rack Ba ck Based O sed Observa bservables bles

Rescaled Rescaled Char Charged ged Jet et Mass Mass Track based jet Mass Calorimeter based jet Mass

arXiv:1108.2701 Jet et Structur Structure e (Nsub Nsub ratio) ratio) Calorimeter based Track based

arXiv:1411.0665 Jet et Structur Structure e (D 3 ) Track based Calorimeter based

Performance Performance (light) light)

Performance Performance (gluon) gluon)

Performance Performance

Summary Summary and and outlook outlook ● In highly boosted regime, constituents merge inside calorimeter cells. Tracks have better angular resolution and can be used. ● We cluster tracks into “top jet” with a shrinking cone size, in order to reduce soft unwanted contamination, and build shape and mass observable out of charged constituents. ● We used DELPHES for detector simulation (and improved tracking for this study) ● We have shown that tracking based observables can discriminate between QCD and top at extreme energies (where calorimeter will fail)

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