Extracting neutrino oscillation parameters using a simultaneous fit of the ν e appearance and ν µ disappearance data in the NOvA experiment Prabhjot Singh , University of Delhi, India On Behalf of the NOvA Collaboration DPF 2017 Fermilab August 03, 2017 Prabhjot Singh, Delhi University (DU) NOvA Analysis August 03, 2017 1 / 20
Current questions in neutrino physics Ordering of the neutrino masses: Normal or Inverted ν µ ν e ν τ δ CP hierarchies ? π 2 3 sin 2 θ 23 0 1 CP violation : do the neutrinos sin 2 θ 23 and anti-neutrinos oscillate ∆ m 2 32 differently? 3 ∆ m 2 32 sin 2 θ 13 π 2 0 θ 23 angle: is the mixing π 3 1 between ν µ and ν τ maximal or 0 Normal Hierarchy Inverted Hierarchy Inverted Hierarchy Normal Hierarchy not? Prabhjot Singh, Delhi University (DU) NOvA Analysis August 03, 2017 2 / 20
Introduction to the NOvA Experiment NOvA (NuMI Off-axis ν e Appearance) is a two detector, long baseline, neutrino oscillation experiment NuMI (Neutrinos at Main Injector) beam is 97.5% ν µ FD Ash River, MN NOvA is 14.6 mrad off-axis from the NuMI beam, observed energy spectrum peaks at 2 GeV peak 8 1 0 Near detector, ND, on-site at k Fermilab. m Far detector, FD, at Ash River, MN, 810 km from the target. ND Oscillation channels Fermilab, IL ν µ → ν µ disappearance ν µ → ν e appearance Anti-neutrino modes Prabhjot Singh, Delhi University (DU) NOvA Analysis August 03, 2017 3 / 20
NOvA Detectors NOvA detectors are functionally identical Polyvinyl chloride (PVC) and low Z scintillator detectors. NOvA cells are arranged in alternating horizontal and vertical planes for 3D tracking. The ND is used to measure the beam before oscillations and the FD measures the oscillated spectrum. Prabhjot Singh, Delhi University (DU) NOvA Analysis August 03, 2017 4 / 20
NuMI (Neutrinos at Main Injector) beam A beam of high energy protons from the Main Injector are impinge on a fixed graphite target producing pions and kaons. Magnetic horns selects particles of the desired charge & momentum and focus them into a narrow beam. Charged pions and kaons spontaneously decay into muons and neutrinos. Rock after absorber filters out muons neutrinos produced in decay pipe. We are left with the neutrino beam. Prabhjot Singh, Delhi University (DU) NOvA Analysis August 03, 2017 5 / 20
Neutrino events in NOvA ν µ CC p ν μ μ ν e CC p ν e e NC π γ π 0 ν p γ 1m 1m 3 10 10 2 10 q (ADC) ν µ CC is the signal for the ν µ (¯ ν µ ) disappearance anaysis. ν e CC is the signal for the ν e (¯ ν e ) appearance anaysis. NC is a background in above analyses. Prabhjot Singh, Delhi University (DU) NOvA Analysis August 03, 2017 6 / 20
Extrapolation: ND Role ND spectra are used to predict the signal and backgrounds in the FD. Both ν µ → ν µ disappearance and ν µ → ν e appearance analyses use ν µ ’s in the ND. The P( ν α → ν β ) and the simulated spectra from ND and FD are used in the form of Far over Near, F/N, ratios to make the FD predictions. Prediction in the FD × P ( ν µ ! ν µ ) ‘s in the ND 1.0 2.0 3.0 4.0 5.0 Energy (GeV) × F N Prediction in the FD 1.0 2.0 3.0 4.0 5.0 Energy (GeV) × P ( ν µ ! ν e ) Energy (GeV) Prabhjot Singh, Delhi University (DU) NOvA Analysis August 03, 2017 7 / 20
Extrapolation: Far detector signal prediction The reconstructed ND ν µ CC energy spectrum is used to correct the FD simulated prediction. True energy distribution is corrected so that the reconstructed data & MC agree at the ND. The FD and ND MC spectra along with the oscillation probability for the ν µ → ν µ disappearance and ν µ → ν e appearance are used to extrapolate corrected ND true spectra to the FD. The extrapolated true energy distrbution is converted to the reconstructed energy distrbution by using E true → E reco distribution. Prabhjot Singh, Delhi University (DU) NOvA Analysis August 03, 2017 8 / 20
Decomposition and Extrapolation of Backgrounds in ν e appearance We use deep learning to seperate the signal and backgrounds into 3 bins of ID confidence from least ν e like to the most ν e like. The ν e selected beam ν e CC, ν µ CC and NC interactions in the ND are backgrounds in the FD. NOvA Preliminary 0.75 < CVN < 0.87 0.87 < CVN < 0.95 0.95 < CVN < 1 Data 3000 POT MC Beam ν e The ND spectrum is decomposed into MC ν CC 20 µ NC, beam ν e CC and ν µ CC. 10 MC NC 2000 × Events / 3.72 Each component is extrapolated from 1000 the ND to the FD for background predictions in the FD. 0 0 1 2 3 4 0 1 2 3 4 0 1 2 3 4 5 Reconstructed neutrino energy (GeV) See talk: Least ν e -like Most ν e -like Deep Learning Applications in the NOvA Experiment (Divided into bins of event classifier) - Fernanda Psihas Prabhjot Singh, Delhi University (DU) NOvA Analysis August 03, 2017 9 / 20
Extrapolation: Systematic uncertainties Systematic uncertainties in the analysis are extrapolated from the ND to the FD using the same extrapolation technique. The ND Data is replaced by the ND prediction under a systematic shift. The corrected ND true energy spectra is extrapolated to the FD. Systematically shifted prediction (MEC) “Corrected” prediction Prabhjot Singh, Delhi University (DU) NOvA Analysis August 03, 2017 10 / 20
Systematic uncertainties in the ν µ disappearance and ν e appearance analyses Systematic uncertainties are included as nuisance parameters in the fit for all analyses. The functionally identical near and far detectors allow most uncertainties to cancel when predicting the FD spectrum. Rel. E scale Normalization had Rel. E scale µ ν Cross Sections Abs. E scale µ Beam bkgd. norm. Calibration Normalization Abs. E scale had Beam Scintillation model Cross-sections & FSI Detector Response Neutrino flux Value of δ Total syst. error CP Total syst. error Statistical error Statistical error − 20 − 10 0 10 20 − 20 − 10 0 10 20 2 -3 Uncertainty on sin ( 10 ) θ × Signal uncertainty (%) 23 In the disappearance analysis, uncertainties due to detector response are dominant but smaller than the statistical uncertainties. In the appearance analysis, cross section uncertainties are important for signal, but small compared to statistical uncertainties. Prabhjot Singh, Delhi University (DU) NOvA Analysis August 03, 2017 11 / 20
ν µ fit to the disappearance data NOvA Preliminary NOvA Preliminary Ratio with unosc. (bkg subtracted) 1.5 20 20 NO ν A 6.05 × 10 POT-equiv. NOvA 6.05 × 10 POT-equiv. 120 Best fit prediction Data 100 Events / 0.25 GeV Unoscillated prediction Best fit prediction 1 Data 80 60 0.5 40 20 0 0 0 1 2 3 4 5 0 1 2 3 4 5 Reconstructed neutrino energy (GeV) Reconstructed neutrino energy (GeV) Disappearance data is fit for the ∆ m 2 NOvA Preliminary 32 and sin 2 θ 23 parameters. NOvA Preliminary 3.5 Normal Hierarchy, 90% CL NOvA 2016 Expected 473 events, observe 78 events, NOvA 2015 clear evidence of neutrino oscillations. ) T2K 2014 2 eV 3 MINOS 2014 -3 (10 Best fit in the Normal Hierarchy: 32 2 ∆ m 2 32 = (2 . 67 ± 0 . 11) × 10 3 eV 2 m ∆ 2.5 sin 2 θ 23 = 0 . 404 +0 . 030 − 0 . 022 or 0 . 624 +0 . 022 − 0 . 030 2 0.3 0.4 0.5 0.6 0.7 2 sin θ Maximal-mixing disfavoured at 2.6 σ . 23 Prabhjot Singh, Delhi University (DU) NOvA Analysis August 03, 2017 12 / 20
ν e fit to the appearance data 0.75 < CVN < 0.87 0.87 < CVN < 0.95 0.95 < CVN < 1 20 NH 1 20 6.05 × 10 POT equiv. FD Data Best Fit Events / 0.5 GeV 15 Background 0.8 10 23 0.6 θ 2 sin 5 0.4 0.2 0 1 2 3 1 2 3 1 2 3 Reconstructed energy (GeV) 1 σ 2 σ 3 σ NH 1 π π 0 3 2 Appearance data is fit for the sin 2 θ 23 0.8 and δ CP parameters. 23 0.6 θ 2 Constrain parameters sin 0.4 sin 2 2 θ 13 = 0.085 ± 0.005, 0.2 ∆ m 2 32 = +2.44 ± 0.06 (NH) 1 σ 2 σ 3 σ IH ∆ m 2 32 = -2.49 ± 0.06 (IH) 0 π π 0 3 π 2 π Observe 33 events in the FD, > 8 σ 2 δ 2 CP significance of ν e appearance. Prabhjot Singh, Delhi University (DU) NOvA Analysis August 03, 2017 13 / 20
Simultaneous fit of the disappearance and appearance data The constraints on the oscillation parameters can be improved by 0.7 combining NOvA’s ν e appearance data with its ν µ disappearance data. 0.6 23 Appearance and disappearance data θ 0.5 2 are simultaneous fit for the sin 2 θ 23 , sin 0.4 δ CP and ∆ m 2 32 parameters. 0.3 1 σ 2 σ 3 σ Best Fit sin 2 2 θ 13 = 0.085 ± 0.005 is a NH π π 0.7 0 3 π 2 π constraint from the reactor experiments. 0.6 23 0.5 θ Two statistically degenerate best fit 2 sin points are in Normal Hierarchy: 0.4 sin 2 θ 23 = 0 . 404, δ CP = 1 . 48 π and sin 2 θ 23 = 0 . 623, δ CP = 0 . 74 π 0.3 1 2 3 Best Fit σ σ σ IH π π 0 3 2 π π Inverted Hierarchy with lower θ 23 2 δ 2 CP octant for all values of δ CP is rejected at > 93% CL. Prabhjot Singh, Delhi University (DU) NOvA Analysis August 03, 2017 14 / 20
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