A preliminary ν μ CC 0 π event selection in SBND Rhiannon Jones - University of Liverpool, UK On behalf of the SBND collaboration New Perspectives, Fermilab Monday 10 th June 2019
SBND MicroBooNE ICARUS The SBN Program 110 470 600 Baseline [m] 112 89 476 Argon mass [t] BNB Target Hall S B N D ( N D ) MicroBooNE ICARUS (FD) M i n i B o o N E o i n t r u e N r e s t o o B B ) N B ( m e a B
Electric field The Short Baseline Light detection system e - e - Near Detector, SBND drift drift Liquid argon time projection chamber ● 112 tonnes of liquid argon ○ 4 x 4 x 5 m 3 ○ 110 m from the neutrino source ○ y z TPC 1 TPC 2 500 V/cm electric field across the TPC ● Anode Anode Neutrinos interact and ionise the argon ○ Cathode plane x wire planes wire planes ν μ Field drifts ionisation electrons towards ○ one of the anode plane assemblies (APAs) 2 electron drift volumes ● Connected at the centre by the cathode ○ plane assembly All TPC components are now at Fermilab! ● Installation will begin this year ○ 2 of our APAs have been unpacked and aligned, the Running by the beginning of 2021 ○ second 2 are here at Fermilab, awaiting the same 3
The physics program of SBND Near detector in the SBN oscillation ● Unprecedentedly high statistics ● analysis ~ 7,000,000 ν μ events over 3 years ○ Characterise the initial flux of the ○ ~20 times μ BooNE, ~10 times ICARUS ○ neutrinos Confirm or rule out the existence of light ○ Will make high-precision cross-section ● sterile neutrinos measurements of neutrino interactions with argon nuclei at ~1 GeV SBN sensitivity to ν μ → ν e oscillations SBN sensitivity to ν μ → ν x oscillations x 10 3 SBND event rate, 3 years of running 100 80 Δm 2 (eV 2 ) 60 40 20 0 0 0.5 1 1.5 2 2.5 3 4 sin 2 2 θ μe sin 2 2 θ μμ arXiv:1503.01520 Neutrino energy, [GeV]
Cross-sections in the Neutrino scattering cross-section data few-GeV energy range G. Zeller, arXiv:1305.7513 [hep-ex], 2013 1.4 ν cross-section [10 -38 cm 2 GeV -1 ] 1.2 Neutrino interactions in the few GeV ● 1.0 energy region are very interesting Boundary between perturbative and 0.8 ○ non-perturbative regimes 0.6 QE, RES and DIS cross-over ■ Historically, very little data in this region 0.4 ○ 0.2 Interactions on heavy nuclei are not yet ● 0 well understood 10 -1 10 1 10 2 1 Neutrino energy, [GeV] Many unconstrained models exist ○ Datasets from recent experiments are SBND will provide data in this energy region ● starting to help constrain these models with huge statistics giving us tighter constraints ○ Such as MINERvA and MiniBooNE on these neutrino-nuclei models 5
http:/ /news.fnal.gov/2015/10/microboone-sees-first-accelerator-born- neutrinos-2/ ν μ CC 0 π in SBND LArTPC LArTPC detector technology: ● Bubble chamber ○ resolution capability (~mm) Automated event processing ○ Bubble Calorimetry chamber ○ https:/ /vms.fnal.gov/asset/detail?recid=1743008&recid=1743008 Can distinguish individual ● Final state charged current topologies in SBND particles in the final state of the x 10 3 SBND event rate, 3 years of running neutrino interaction 100 ν μ CC 0 π is the most simple and 80 ● abundant final state in SBND: 60 1 muon and any number of protons 40 20 Expect to see ~4,000,000 ● ν μ CC 0 π events in 3 years 0 6 0 0.5 1 1.5 2 2.5 3 Neutrino energy, [GeV]c
Using the ν μ CC 0 π final state in SBND n μ - μ - FSI ν μ FSI FSI p ν μ ν μ p π ± A Multiple p b s o Bound nucleon scattering r p t i o n n interactions p μ - x 10 6 2.5 SBND event rate, 3 years of running Nuclear target neutrino experiments don’t ● GENIE v02.12.10, Default+MEC 2 necessarily observe the products of the initial interaction which took place 1.5 Can use exclusive final state topologies, ● 1 such as ν μ CC 0 π, to discriminate between 0.5 neutrino-argon interaction models Distinguishing power in the proton ○ 0 0 1 2 3 4 5 6 multiplicity of the final state 7 Proton multiplicity in the true ν μ CC 0 π final state
ν μ CC 0 π f inal state particles in SBND Neutrino vertex Wire number p Monte Carlo SBND ● Time, TDC p p ν μ CC 0 π events μ - ν μ CC 0 π 3p signal event in the SBND MC sample ● Resolution allows for straightforward particle identification by-eye Neutrino vertex Wire number ● Final states with interesting p Time, TDC ‘Hammer’ signal event in the SBND MC sample physical characteristics μ - p Need to ensure our software can reconstruct and select these events 8
Selecting ν -Ar interaction final state particles 40 dE/dx [MeV/cm] ● Use calorimetry to distinguish protons from muons & pions G4 MC Predictions 35 Proton ― 30 Kaon ― Pion ― ● Use case: Fit the bragg peak of a reconstructed track to the 25 Muon ― theoretical peak under a certain particle hypothesis • Recorded stopping track 20 15 Fitting to the proton hypothesis has the strongest ● 10 discrimination power 5 0 Fraction of true particles [arb] Particle-gun 0 5 10 15 20 25 30 Residual range [cm] ArgoNeuT, JINST 7, P10019, 2012 samples Protons are correctly distinguished from Protons muons and pions 98% of the time when tested on a BNB sample! Muons 0 50 100 150 200 250 χ 2 under proton hypothesis
μ Selecting ν -Ar interaction final Use geometrical features of the event to find state particles muons All tracks contained: Compare lengths of all ● n ℒ particles to determine if a muon exists Fiducial volume of the TPCs p Longest ⇒ muon ● π Single track escapes: π Check if the neutrino ● vertex is far from the 5 . 5 % e v e n t s h a v e a p n exiting border s i n g l e e s c a p i n g t r a c k ν μ Large ℒ ⇒ muon exits ● 9 5 . 9 % e s c a p i n g t r a c k s a r e μ 10
Performance of the selection in SBND Selected → Main sources of ν μ CC Inclusive ν μ CC 0 π ↓ True topological impurities: ν μ CC 0 π 39,100 32,650 Pion-proton mis-ID ν μ CC 1 π 8,386 3,218 8.5% in 0 π ν μ CC Other 658 70 Incorrect-muon finding 5.6% in 0 π , 5.8% in Inc. ν μ NC 2,967 2,130 Efficiency 92.0% 76.9% Efficiency: Signal / Total true Purity 94.2% 85.8% Purity: Signal / Total selected No external backgrounds (cosmic rays and dirt muons) included in the selection yet 11
Summary SBND will drastically increase the amount of neutrino interaction data on ● heavy nuclei in the few-GeV energy range The LArTPC detector technology allows us to observe final state particles ● at bubble chamber resolution We can utilise particle selections to produce high-precision cross-section ○ measurements on exclusive final state topologies Oscillation measurements can also be made using exclusive final states to help ○ constrain the interaction systematic uncertainties Understanding neutrino interactions on argon will help future experiments ● like DUNE probe new and interesting physics 12
Backup slides 13
Neutrino-nuclear interactions CC QE on C 12 CC QE on free-nuclei is a theoretically well ● L. Alvarez-Ruso, arXiv:1012.3871 (Neutrino 2010) understood process 8 σ [x 10 -38 cm 2 ] 𝜉 μ + n → μ - + p 7 Models were built on neutrino interactions on ○ 6 free-nuclei 5 Don’t work for interactions on nuclear targets ○ Experiments use nuclear targets! ○ 4 3 Experiments such as MiniBooNE saw an ● excess of events 2 Known as the quasi-elastic puzzle MiniBooNE data ○ 1 The data is QE-like, not true QE ○ 0 Tuning free model parameters & including ○ 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 the 2p-2h process helps fix this Neutrino energy, [GeV] 14
μ vs. π : z-angle & momentum Took pions as the comparable particle ● since they rival the individuality of the muon’s MIP property Looking at the characteristics of the ● true particles, does this support the theory that the muon is most likely to escape when the neutrino vertex is sufficiently far from the fiducial border? Since the muons tend to have higher ● momenta and are more forward going: Yes! 15
Finding escaping Tentative fiducial border definition: muons X = 10 Y = 20 Z = 10 In an event with 1 ● Δy escaping particle, we can use the TPC to determine π ℒ if this particle is a muon ○ Using its properties as a Fiducial volume of the TPC Δx p MIP and the neutrino primary final state lepton ● If a particle exists and the neutrino interaction vertex y is far from the border the z particle exits from ( ℒ is large) , ask if that particle is likely to be a muon x 16
Escaping track rates Arb. units The true muon is the escaping particle When the neutrino vertex is The true muon is not the escaping particle further than ~50 cm from the escaping fiducial border, the escaping track becomes significantly more likely to be a muon 0 50 100 150 200 250 300 350 400 450 500 Distance of the neutrino vertex from the escaped fiducial border [cm] 17
Quantities within this sample Total events with contained, reconstructed neutrino vertex 65,830 True vertex also contained 96.3% Maximum 1 escaping track 99.9% Exactly 1 escaping track 5.5% Of these, only the true muon escapes 95.9% Adding cosmics has reduced the ‘free’ muons to be 4.9% of the sample 18
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