Charged Hadrons IP resolution in -decays and reconstruction of CP- - - PowerPoint PPT Presentation

Charged Hadrons IP resolution in τ-decays and reconstruction of CP-mixing angle in H→ττ

• A. Raspereza, A. Tumasyan

Outline

• PV resolution in ggF / VBF H→ττ processes
• Charged hadron IP resolution in τ ± → π± + ν

and τ ± → π± + π0 + ν

• CP-mixing angle reconstruction in ggF/VBF

H→ττ

General Information

Datasets

Fall17 MC /GluGluHToTauTau_M125_13TeV_powheg_pythia8/RunIIFall17MiniAOD- 94X_mc2017_realistic_v10-v1/MINIAODSIM /VBFHToTauTau_M125_13TeV_powheg_pythia8/RunIIFall17MiniAOD-94X_mc2017_realistic_v10- v1/MINIAODSIM Phase II MC samples with noPU: /GluGluHToTauTau_M125_14TeV_powheg_pythia8/PhaseIITDRFall17MiniAOD- noPU_93X_upgrade2023_realistic_v2-v1/MINIAODSIM /VBFHToTauTau_M125_14TeV_powheg_pythia8/PhaseIITDRFall17MiniAOD- noPU_93X_upgrade2023_realistic_v2-v1/MINIAODSIM Phase II MC samples PU=200 /GluGluHToTauTau_M125_14TeV_powheg_pythia8/PhaseIITDRFall17MiniAOD- PU200_93X_upgrade2023_realistic_v2-v2/MINIAODSIM /VBFHToTauTau_M125_14TeV_powheg_pythia8/PhaseIITDRFall17MiniAOD- PU200_93X_upgrade2023_realistic_v2-v2/MINIAODSIM

CMSSW_9_4_0_patch1 Selected events with Ptτ > 35, ητ < 2.3, and decay mode ≤ 1 Gen-Reco τ-matching with cone 0.3

RECO PV vs GEN PV in ggF H→ττ

difference of charged hadron Vx, Vy, Vz Reco - Gen X Y Z

RECO PV vs GEN PV in VBF H→ττ

difference of charged hadron Vx, Vy, Vz Reco - Gen

Impact Parameter of charged hadron

PV Charged hadron Vertex Leading (in our case the only) charged hadron momentum Closest approach IP vector

Linear extrapolation was used for IP vector determination

RECO IP vs GEN IP in ggF H→ττ

difference of charged hadron IPx, IPy, IPz Reco - Gen

RECO IP vs GEN IP in VBF H→ττ

difference of charged hadron IPx, IPy, IPz Reco - Gen

RECO IP vs GEN IP in ggF H→ττ wrt Gen-Vertex

difference of charged hadron IPx, IPy, IPz Reco – Gen wrt Gen PV

CP-mixing angle reconstruction in H→ττ

• Eur. Phys. J. C (2014) 74:3164

CP-mixing angle: φ*CP is

• 1. prong 0

τ

+ → π + + ν

τ

• → π
• + ν

Angle between normalized IP*┴ of charged hadrons in π

+ π

• - ZMF
• 2. prong 1

τ

+ → ρ + + ν → π + + π 0 + ν

τ

• → ρ
• + ν → π
• + π

0 + ν

Angle between transverse components of neutral hadrons (π

0) momentums in

π

+ π

• - ZMF

CP-mixing angle reconstruction in H→ττ

prong 0-0 τ

+ → π + + ν and τ

• → π
• + ν

Angle between normalized IP*┴ of charged hadrons in π

+ π

• - ZMF

where arXiv:1510.03850v1

CP-mixing angle reconstruction in H→ττ

prong 1-1 τ

+ → ρ + + ν → π + + π 0 + ν and τ

• → ρ
• + ν → π
• + π

0 + ν

Angle between PT of neutral hadrons (π

0) in π + π

• - ZMF

where arXiv:1510.03850v1

2 categories: yτ > 0 or yτ < 0

where

CP-mixing angle reconstruction steps and combination

• First we set 4-momentum of charged hadrons: q+ and q–
• Reconstruction of charged hadron IP vector for 0-prong and

constructing (0, IP) 4-vector, or using 4-momentum vector of π

0 for

1-prong. Let’s denote these vectors p+ and p–

• Boost to π

+ π

• - ZMF and normalization: 𝑟

*± and 𝑞 *±

• For 1-prong yτ sign needs to be determined (for 0-prong it always +)
• If yτ < 0 then φ* = arcos (𝐪

*+

┴ · 𝐪

*–

┴) should be shifted by π to

combine with yτ > 0 category where φ* = arcos (𝐪 *+

┴ · 𝐪

*–

┴)

= 𝐫

*– · (𝐪 *+

┴ × 𝐪

*–

┴)

CP-mixing angle in ggF H→ττ for various categories of yτ

yτ > 0 yτ < 0 yτ > 0 and shifted yτ < 0

Fall17 samples Generator Level

CP-mixing angle with Fall17, Upgrade_noPU and Upgrade_200PU samples

Gen Reco Gen Reco

CP-mixing angle: ggF vs VBF (Fall17)

ggF ggF VBF VBF

What can be done to improve the results (separation power of φ*CP)

• Propagation of charged hadron track to the point of closest

approach taking into account magnetic field (might be better IP resolution)

• PV refitting excluding tracks from τ-decays

(might be better IP resolution)

Thank You