Understanding Neutrino Events at Liquid Argon Detectors Shirley Li Collaborator: A. Friedland Precision Investigations of the Neutrino Sector, July 2019

Measuring 𝛿 CP and MH ~1000 km 0.5—5 GeV 𝜈 𝜇 𝜈 𝑒 DUNE CDR Need to measure 𝑁( 𝐸 𝜈 𝑒 ) Shirley Li (SLAC) 2/31

Detects charged particles above thresholds DUNE detector 40 kton liquid argon TPC DUNE and NOvA Detects charged particles above thresholds Shirley Li (SLAC) 3/31

The overarching question How well can we measure neutrino energy? Simulated with GENIE+FLUKA Friedland & Li, 2018 Shirley Li (SLAC) 4/31

No consensus in the field Energy resolution from prior work Romeri, Fernandez-Martinez & Sorel, 2016 Shirley Li (SLAC) 5/31

Two types of performance studies Fast Monte Carlo type DUNE CDR See physical connection; not quantitative Shirley Li (SLAC) 6/31

Two types of performance studies Full propagation type Romeri, Fernandez-Martinez & Sorel, 2016 Complete; hide physical connection Shirley Li (SLAC) 7/31

No consensus in the field Energy resolution from prior work Romeri, Fernandez-Martinez & Sorel, 2016 Shirley Li (SLAC) 8/31

Our goal: Understanding the physics of energy reconstruction Shirley Li (SLAC)

Calorimetric energy reconstruction Signal: 𝜈 𝑙 +𝐴→𝑙+𝑋 Simulated with GENIE+FLUKA Friedland & Li, 2018 Separate 𝑙 and hadronic system 𝐸 𝑙 : total collected charge -> energy 𝐸 ℎ : total collected charge -> energy 𝐸 𝜈 = 𝐸 𝑙 + 𝐸 ℎ or 𝐸 𝜈 =𝑓( 𝐸 𝑙 , 𝐸 ℎ ) How to characterize its performance? Shirley Li (SLAC) 10/31

Calorimetric energy reconstruction Signal: 𝜈 𝑙 +𝐴→𝑙+𝑋 Should work perfectly if 𝐸 𝑙 →ionization dE dx → charge Problem arises if 𝐸 ℎ → ionization missing energy Understanding missing energy is the key Shirley Li (SLAC) 11/31

Hadronic system Prompt 𝜈 vertex: 𝜈 𝑙 +𝐴→𝑙+𝑋 Friedland & Li, 2018 GENIE default model 30 – 40% of neutrino energy, large fluctuations Shirley Li (SLAC) 12/31

Multiple species contribute, large fluctuations Hadronic system GENIE simulation Friedland & Li, 2018 Varied composition Multiple species contribute, large fluctuations Shirley Li (SLAC) 13/31

Prompt neutrons are the biggest issue Missing energy in 𝐸 ℎ After primary vertex Friedland & Li, 2018 Prompt neutrons are the biggest issue Shirley Li (SLAC) 14/31

Secondary particle propagation Charged particles Friedland & Li, 2018 Many re-interactions Shirley Li (SLAC) 15/31

Secondary particle propagation Friedland & Li, 2018 Neutrons Simulated with FLUKA Neutron deposit ~ 50% of its energy in ionization Shirley Li (SLAC) 16/31

Secondary particle propagation Friedland & Li, 2018 Neutrons Simulated with GENIE+FLUKA Extremely challenging to reconstruct neutrons Shirley Li (SLAC) 17/31

Secondary particle propagation Friedland & Li, 2018 Neutrons Simulated with GENIE+FLUKA Extremely challenging to reconstruct neutrons Shirley Li (SLAC) 17/31

Secondary particle propagation Friedland & Li, 2018 Neutrons Simulated with GENIE+FLUKA Extremely challenging to reconstruct neutrons Shirley Li (SLAC) 17/31

After full propagation Missing energy in 𝐸 ℎ Recombination: Nuclear breakup: 𝑝+40Ar→3𝑝+𝑋 Energy -> nuclear binding energy Thresholds Neutrons After full propagation charge ∝ 1 1+0.1 𝑑𝐸 𝑑𝑥 Friedland & Li, 2018 Shirley Li (SLAC) 18/31

Missing energy in 𝐸 ℎ Reducible vs. irreducible Friedland & Li, 2018 Reducible vs. irreducible Reducible: threshold, rec Irreducible: nucl, 𝜈, neutron Irreducible missing energy has to be simulated correctly Shirley Li (SLAC) 19/31

Energy reconstruction results Friedland & Li, 2018 CDR th: method as it is Charge: collect all charges with no thresh. Best rec: no thresh., correct for recombination Shirley Li (SLAC) 20/31

Two types of performance studies Shirley Li (SLAC)

Two types of performance studies Full propagation Fast Monte Carlo DUNE CDR Romeri, Fernandez-Martinez & Sorel, 2016 Shirley Li (SLAC) 22/31

Protons Energy distribution 23/31 Friedland & Li, in prep Shirley Li (SLAC) 23/31

Protons Energy distribution 24/31 Friedland & Li, in prep Shirley Li (SLAC) 24/31

Large missing energy fraction Protons Friedland & Li, in prep Visible energy Large missing energy fraction Shirley Li (SLAC) 25/31

Neutron-created charges are important Protons Friedland & Li, in prep Energy resolution Neutron-created charges are important Shirley Li (SLAC) 26/31

Charged pions Friedland & Li, in prep Shirley Li (SLAC) 27/31

Neutrons Friedland & Li, in prep Shirley Li (SLAC) 28/31

Friedland & Li, 2018 Shirley Li (SLAC) 29/31

Conclusions Basic performance of liquid argon were not understood We understand missing energy of neutrino events: neutrons, nuclear breakup, recombination Improve reconstruction strategy Details in arXiv:1811.06159, PRD 2019 Test beam data will be crucial for simulation validation Shirley Li (SLAC) 30/31

Outlook A framework to evaluate neutrino-nucleus cross section uncertainty impact on oscillations Full propagation studies guarantee no missing physics fastMC type studies need full, correct inputs Easy to see physics connections Shirley Li (SLAC) 31/31

Backup

Bi-probability plot

Comparisons to other work Friedland & Li, 2018 Romeri, Fernandez-Martinez & Sorel, 2016 Further studies warranted Shirley Li (SLAC)