Introduction to Dalitz plot fitters and techniques T. Evans 1 , J. - - PowerPoint PPT Presentation

Introduction to Dalitz plot fitters and techniques

• T. Evans1, J. Dalseno2

Cincinnati1, Santiago de Compostela2

• T. Evans1, J. Dalseno2

Joint LHCb-BESIII Amplitude Analysis Workshop 1/4

Introduction

⊲ Ten different packages being used inside LHCb for amplitude analysis. ⊲ Different languages and strategies used: c++, python, GPUs, TensorFlow, ⊲ Another interesting divide is between implicit and explicit styles. Implicit ⊲ Give a decay channel → automatically assign an amplitude to it. ⊲ This is the more common approach. Used by: AmpGen, Craft, GooFit, Laura++, Mint2 and zFit. Explicit ⊲ Provide the building blocks to write down the full amplitude, then write it, assign to a decay channel. ⊲ Tend to be more general computing frameworks that amplitude analyses are built ontop of. ⊲ Includes: cFit, Hydra, Ipanema and TensorFlowAnalysis (TFA).

⊲ The distinction is not entirely cleancut, as several have features of both approaches. ⊲ Could also be viewed more as a spectrum than a category.

• T. Evans1, J. Dalseno2

Joint LHCb-BESIII Amplitude Analysis Workshop 2/4

Feature table

AmpGen cFit Craft GooFit Hydra Ipanema Laura++ Mint2 TFA zFit C++ ✓ ✓ ✓ ✓ ✓ ✗ ✓ ✓ ✗ ✗ Python ✗ ✗ ✗ ✓ ✗ ✓ ✓ ✗ ✓ ✓ GPU accelerated ✗ ✗ ✗ ✓ ✓ ✓ ✗ ✗ ✓ ✓ > 3-body ✓ ✗ ✗ ✓ ✓ ✗ ✓ ✓ ✓ s-dependent full width ✓ ✗ ✗ ∼ ✗ ✗ ✓ ✗ ✗ Numerical dispersive mass ✓ ✗ ✗ ✗ ✗ ✗ ✓ ✗ ✗ Covariant spin ✓ ✗ ✗ ✓ ✗ ✓ ✓ ∼ ✗ S > 0 initial/final state ✓ ✗ ✗ ✗ ✗ ✗ ✓ ✓ WIP S >= 1

2 initial/final state

✓ ✗ ✗ ✗ ✗ ✗ ✗ ✓ WIP Photon polarisation ✓ ✗ ✗ ✗ ✗ ✗ ✓ ✗ Simultaneous B/D mass fit ✗ ✓ ✓ ✗ ✗ ✓ ✗ ✓ ✓ Integral by MC ✓ ✗ ✗ ✓ ✓ ✗ ✓ ✓ ✓ Double Dalitz capable ✓ ∼ ✗ ✗ ✗ WIP ✗ ✓ ✗ D Dalitz ✓ ✓ ✓ ✓ ✗ ✓ ✓ ✓ ✓ B Dalitz (SDP) ✗ ✗ ✓ ✗ ✗ ✓ ✗ ✓ ✗ B Amplitude (VV) ✓ ✗ ✗ ✓ ✓ ✗ ✓ ✓ WIP 1D mass resolution ✗ ✗ ✗ ✗ ✗ ✗ ✗ 2D mass convolution map ✗ ✗ ✗ ✗ ✗ ✓ ✗ Incoherent B0

s time

✗ ✗ ∼ ✗ ✓ WIP ✓ Coherent B0 time ✗ ✗ ∼ ✗ ✗ WIP ✗ Missing energy ✗ ✗ ✗ ✗ ✗ ✗ ✗

• T. Evans1, J. Dalseno2

Joint LHCb-BESIII Amplitude Analysis Workshop 3/4

Repositories

AmpGen github.com/GooFit/AmpGen/ cfit github.com/cfit/cfit GooFit github.com/GooFit/GooFit Hydra github.com/MultithreadCorner/Hydra Ipanema gitlab.cern.ch/bsm-fleet/Ipanema/ Laura++ laura.hepforge.org Mint2 github.com/jdalseno/Mint2 TFA gitlab.cern.ch/poluekt/TensorFlowAnalysis zFit github.com/zfit/zfit

• T. Evans1, J. Dalseno2

Joint LHCb-BESIII Amplitude Analysis Workshop 4/4

Timetable (Today and Tomorrow)

⊲ We didn’t assign a talk to each fitter ⊲ Instead picked out a more unique/cutting-edge feature to present ⊲ Efficiency variations in the phase space require a lot of MC to understand ⊲ Backgrounds come from sideband with different phase space volume ⊲ MVA solutions ⊲ s-dependent widths typically calculated for the final state

• eg. ω → π+π−

⊲ Using the PDG to determine partial width couplings for better pole parameter measurements ⊲ Spin formalisms ⊲ Helicity, covariant, pentaquark and B → Kππγ polarisation ⊲ Experimental resolution usually addressed in systematics ⊲ Modelling them in the fit with 1D and 2D approaches ⊲ Stand-alone fitters used to be unattractive due to reproducibility issues ⊲ Standardising with TensorFlowAnalysis and Analysis Preservation