NOvA (with focus on the mass hierarchy) Jeff Hartnell University of Sussex Solvay Workshop, Brussels 30 th November 2017
IntroducAon • NOvA experiment and physics goals – NuMI beam – NOvA detectors • Mass hierarchy via MSW maHer effect • Nue and nuebar appearance probabiliAes • Results: – Muon neutrino disappearance – NC analysis – Electron neutrino appearance • Future sensiAvity Jeff Hartnell, Solvay 2017 2
NOvA Overview • “ ConvenAonal ” beam Ash River • Two-detector experiment: • Near detector – measure beam composiAon – energy spectrum • Far detector – measure oscillaAons and search for new physics Ash River 810 km Jeff Hartnell, Solvay 2017 3
The NOvA CollaboraAon Argonne, AtlanAco, Banaras Hindu University, Caltech, Cochin, InsAtute of Physics and Computer science of the Czech Academy of Sciences, Charles 242 Collaborators University, CincinnaA, Colorado State, Czech Technical University, Delhi, JINR, Fermilab, Goiás, IIT GuwahaA, Harvard, IIT Hyderabad, U. Hyderabad, 49 institutions Indiana, Iowa State, Jammu, Lebedev, Michigan State, Minnesota-Twin 7 countries CiAes, Minnesota-Duluth, INR Moscow, Panjab, South Carolina, SD School of Mines, SMU, Stanford, Sussex, Tennessee, Texas-AusAn, Tu[s, UCL,Virginia, Wichita State, William and Mary, Winona State Jeff Hartnell, Solvay 2017 4
Physics Goals Results from 3 different oscillation analyses ¨ Disappearance of ν µ CC events ¨ Appearance of ν e CC ¤ clear suppression as a events funcAon of energy ¤ 2016 analysis results θ 13 , θ 23 , δ CP , PRL 118.151802 and Mass Hierarchy sin 2 (2 θ 23 ) � � ∆ m 2 � ¤ 2 GeV neutrinos � 32 enhances maHer ¨ Deficit of NC events? effects ¤ ±30% effect ¤ suppression of NCs could be evidence of oscillaAons involving a sterile ¤ 2016 analysis results neutrino in PRL 118.231801. ¤ Fit to 3+1model ¤ new! ∆ m 2 41 , θ 34 , θ 24 Jeff Hartnell, Solvay 2017 5
NuMI Beam On-axis Off-axis Jeff Hartnell, Solvay 2017 6
A NO 𝜉 A cell NO 𝜉 A detectors To APD Extruded PVC cells filled with 11M liters of scintillator instrumented with 𝜇 -shifting fiber and APDs 1560 cm Far detector: 14-kton, fine-grained, low- Z , highly-active tracking calorimeter → 344,000 channels 32-pixel APD Near detector: Fiber pairs 0.3-kton version of 4 cm ⨯ 6 cm from 32 cells the same → 20,000 channels Jeff Hartnell, Solvay 2017 7
Long-baseline neutrino oscillations 𝜉 𝜈 disappearance: …to leading order experimental data are consistent with unity (“maximal mixing”) Need a leap in precision on 𝜄 23 (and � m 2 ) 32 𝜉 e appearance: …plus potentially large CPv and Daya Bay reactor experiment: matter effect sin 2 (2 𝜄 13 ) = 0.084 ± 0.005 modifications! Non-zero 𝜄 opens the long- baseline appearance channel, and… Jeff Hartnell, Solvay 2017 8
StarAng with ν μ 1 ν µ ν τ 0.8 Oscillation Probability 0.6 0.4 0.2 ν e 1000 2000 L/E (km/GeV) Jeff Hartnell, Solvay 2017 9
How does the mass hierarchy come into play? Δ m 2 31 and Δ m 2 32 differ by 3% Small effect JUNO’s planned measurement involves this Jeff Hartnell, Solvay 2017 10
MaHer Effect & Mass Hierarchy • Neutrinos (and anAneutrinos) travel through maHer not anAmaHer – electron density causes asymmetry (fake CPv!) • via specifically CC coherent forward elasAc scaHering – different Feynman diagrams for ν e and ν e interacAons with electrons so different amplitudes Arrows flip for antineutrinos Jeff Hartnell, Solvay 2017 11
Long-baseline 𝜉 𝜈 → 𝜉 e A more quantitative sketch… For fixed L / E = 0.4 km/MeV At right: P ( 𝜉 ⎺ 𝜈 → 𝜉 ⎺ e ) vs. P ( 𝜉 𝜈 → 𝜉 e ) plotted for a single neutrino energy and baseline Jeff Hartnell, Solvay 2017 12
Long-baseline 𝜉 𝜈 → 𝜉 e A more quantitative sketch… For fixed L / E = 0.4 km/MeV At right: P ( 𝜉 ⎺ 𝜈 → ⎺ e ) vs. P ( 𝜉 𝜈 → 𝜉 e ) 𝜉 plotted for a single neutrino energy and baseline Measure these probabilities (an example measurement of each shown) Also: Both probabilities ∝ sin 2 𝜄 23 Jeff Hartnell, Solvay 2017 13
Non-maximal mixing scenario inverted% • If θ 23 non-maximal hierarchy Θ 23%>% 45 o Θ 23%<% 45 o then effect of octant normal% is important hierarchy • Big effect, +/- 20% Jeff Hartnell, Solvay 2017 14
Effect of Increasing Energy 𝜉 𝜈 → 𝜉 NOvA T2K DUNE A more quantitative sketch… For fixed L / E = 0.4 km/MeV 8 L = 1300 km, <E> = 3.2 GeV 7 Normal Mass Hierarchy Inverted Mass Hierarchy ⎺ 𝜈 → 𝜉 𝜉 ⎺ 𝜉 𝜈 → 𝜉 ) 6 " = 0 " = # /2 ino ! e )> [%] " = # 5 " = 3 # /2 4 <P( ! µ 3 2 1 2 2 $ 13 = 0.09 sin 0 0 1 2 3 4 5 6 7 8 <P( ! µ ! e )> [%] 2 GeV 0.6 GeV 3 GeV Increasing Energy [ à bigger matter effect and hence bigger fake CP violation] Jeff Hartnell, Solvay 2017 15
The measurements Jeff Hartnell, Solvay 2017 16
Event Types ν µ CC p Long, straight track ν μ μ ~5m ν e CC p Shorter, wider, fuzzy shower ν e e ~2.5m NC ν Diffuse activity from nuclear recoil system 1m 1m 3 10 2 10 10 q (ADC) 17 Jeff Hartnell, Solvay 2017
𝜉 𝜈 disappearance • Identify contained 𝜉 𝜈 CC events in each detector • Measure their energies • Extract oscillation information from differences between the Far and Near energy spectra (simulated 𝜉 𝜈 CC event) Jeff Hartnell, Solvay 2017 18
ν μ Near Detector Data ν μ μ ν μ – ν μ Jeff Hartnell, Solvay 2017 19 –
ν μ Far Detector Data NOvA Preliminary 20 Prediction, no systs. Normal Hierarchy 1- syst. range σ Prediction with systs. 15 Events / 0.25 GeV Backgrounds Data 10 5 0 0 1 2 3 4 5 Reconstructed neutrino energy (GeV) 78 events observed in FD – 473±30 with no oscilla5on – 82 at best oscillaAon fit – 3.9 beam BG + 2.7 cosmic Jeff Hartnell, Solvay 2017 20
ν μ ν μ Disappearance Result � ts, NOvA Preliminary � 3.5 Normal Hierarchy, 90% CL NOvA 2016 T2K 2014 ) 2 eV � MINOS 2014 ν μ 3 � -3 (10 om 32 2 m ∆ 2.5 𝟑 � 𝜾 𝟑𝟒 𝜠𝒏 𝟒𝟑 No FC Correction 2 0.3 0.4 0.5 0.6 0.7 2 sin θ 23 Best Fit (in NH): Maximal mixing � = 2 . 67 ± 0 . 12 × 10 − 3 eV 2 � � � ∆ m 2 32 excluded at 2.6 σ – sin 2 θ 23 = 0 . 40 +0 . 03 − 0 . 02 (0 . 63 +0 . 02 − 0 . 03 ) Driven by bins in oscillation dip (1-2 GeV). Forcing maximal mixing gives: 32 = (2 . 46) × 10 − 3 eV 2 ∆ m 2 Jeff Hartnell, Solvay 2017 21
Neutral Current Result (NOvA’s first 2017 dataset result, presented at NuFact Sep/17) Jeff Hartnell, Solvay 2017 22
NC Far Detector Data & Results Observed 214 NC candidates Prediction 191.16 ± 13.82(stat.)±21.99 (syst.) 2 � θ 23 Δ𝑛 32 δ 𝐷𝑄 ’s No depletion of NC events observed � θ 23 δ 24 NOvA sees no evidence for ν s mixing � 𝜄 24 𝜄 34 – +0.080 (𝑡𝑧𝑡𝑢. ) θ 𝟐. 𝟐𝟘𝟏 ± 0.160 (𝑡𝑢𝑏𝑢. ) −0.130 No NC disappearance → R = +0.143 (𝑡𝑧𝑡𝑢. ) θ 𝟐. 𝟐𝟘𝟏 ± 0.123 (𝑡𝑢𝑏𝑢. ) −0.124 +0.142 (𝑡𝑧𝑡𝑢. ) ’s two degenerate best fit points θ 𝟐. 𝟐𝟖𝟘 ± 0.123 (𝑡𝑢𝑏𝑢. ) −0.124 2 θ 23 Δ𝑛 32 δ 𝐷𝑄 +0.142 (𝑡𝑧𝑡𝑢. ) θ 𝟐. 𝟐𝟖𝟕 ± 0.123 (𝑡𝑢𝑏𝑢. ) −0.124 Jeff Hartnell, Solvay 2017 23 2 Δ 𝑛 41 – 𝜾 𝟑𝟓 𝜾 𝟒𝟓 “ ” –
𝜉 e appearance • Identify contained 𝜉 e CC candidates in each detector • Use Near Det. candidates to predict beam backgrounds in the Far Detector • Interpret any Far Det. excess over predicted backgrounds as 𝜉 e appearance (simulated 𝜉 e CC event) Jeff Hartnell, Solvay 2017 24
ν ν e Near Detector Data � ν Select ν e CC interacAons with 73% efficiency and 76% purity • � Use ND data to predict background in FD • – NC, CC, beam ν e each propagate differently � 𝑡/ 𝑡 + 𝑐 beam ν e up by 4% – constrain beam ν e using selected ν µ CC spectrum � NC up by 17% – constrain ν µ CC using Michel Electron distribuAon ν µ CC up by 10% � Jeff Hartnell, Solvay 2017 25 –
PredicAon ¨ Extrapolate each component in bins of energy and CVN output NOvA Simulation 50 Total events expected 2 NOvA FD sin =0.4-0.6 θ 23 ¨ Expected event counts depend 20 6.05 10 POT equiv. × 40 on oscillaAon parameters 30 Signal events 20 (±5% systematic uncertainty): 10 NH NH, 3 π /2, IH, π /2, IH 0 π π 0 3 2 π π 28.2 11.2 2 δ 2 CP Background by component (±10% systematic uncertainty): Total BG NC Beam ν e ν µ CC ν τ CC Cosmics 8.2 3.7 3.1 0.7 0.1 0.5 Jeff Hartnell, Solvay 2017 26
ν e Far Detector Data NOvA Preliminary 0.75 < CVN < 0.87 0.87 < CVN < 0.95 0.95 < CVN < 1 20 NH FD Data Events / 0.5 GeV Bin Best Fit Prediction • Observe 33 15 Total Background Cosmic Background events 20 6.05 × 10 POT equiv. 10 Ø background 8.2 ± 0.8 CVN=0.991 5 E=1.63 GeV 0 1 2 3 1 2 3 1 2 3 Reconstructed neutrino energy (GeV) >8 σ electron neutrino appearance signal Jeff Hartnell, Solvay 2017 27
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