& Combined Analysis with Daya Bay and Bugey-3 Andy Blake, - PowerPoint PPT Presentation

Latest Sterile Neutrino Results from MINOS+ & Combined Analysis with Daya Bay and Bugey-3 Andy Blake, Lancaster University (for the MINOS+ collaboration) NuFact Conference, Uppsala University Tuesday 26 th September, 2017

Overview u The MINOS & MINOS+ experiments The MINOS+ Collabora1on u Beyond three flavours ➣ 3+1 sterile model u Searching for sterile ν ’s in MINOS & MINOS+ ➣ ν µ disappearance ➣ ν µ ➔ ν e appearance u Combined analysis with Argonne · Athens · Brookhaven · Caltech · Cambridge · Campinas · Cincinna1 · Daya Bay & Bugey-3 Fermilab · Goiás · Harvard · Holy Cross · Houston · IIT · Indiana · Iowa State · Lancaster · Manchester · Minnesota-Twin Ci1es · Minnesota-Duluth · OLerbein · Oxford · PiLsburgh · Rutherford · São Paulo · South Carolina · Stanford · Sussex · Texas A&M · Texas-Aus1n · TuSs · UCL · Warsaw · William & Mary Andy Blake, Lancaster University Slide 2

The MINOS/MINOS+ Experiments Far Detector Near Detector (Soudan mine) (Fermi Laboratory) 735 km from beam target 1 km from beam target 5.4 kton mass 1 kton mass u The MINOS (2005-12) and MINOS+ (2013-16) experiments represent more than a decade of long-baseline neutrino physics. ➣ Precision measurements of standard three-flavour oscillations. ➣ Searches for new phenomena beyond standard oscillations. u Experiment is now over, but data analysis continues. Latest results are based on a combined analysis of MINOS with ~50% of MINOS+ data. Andy Blake, Lancaster University Slide 3

The NuMI Accelerator Beam ‘Neutrinos from the Main Injector’ p u The MINOS/MINOS+ detectors were located on-axis in the NuMI beam, resulting in a wide-band spectrum. u MINOS operated using a low-energy beam configuration. ➣ Both neutrino and anti-neutrino data sets were collected. u MINOS+ coincided with the NOvA era, and ran in a medium-energy beam. Andy Blake, Lancaster University Slide 4

MINOS & MINOS+ Data u MINOS & MINOS+ collected >25 × 10 20 POT accelerator neutrino data during 11 years of operation. Low-energy beam Medium-energy beam Neutrino mode (10.6 × 10 20 POT) Neutrino mode (9.7 × 10 20 POT) Antineutrino mode (3.4 × 10 20 POT) Special beam configurations To be analysed MINOS (2005-12) MINOS+ (2013-16) 5.8 × 10 20 POT analysed so far Andy Blake, Lancaster University Slide 5

The MINOS Detectors u MINOS/MINOS+ Near and Far Detectors Veto were functionally similar . Shield ➣ Segmented, sampling, tracking 8m steel/scintillator calorimeters. ➣ Magnetised with ~1.2T field for charge-sign determination. Coil u Each detector measured energy spectrum and flavour composition of NuMI beam. ➣ ν µ CC, ν e CC and NC interactions were identified and measured using Last MINOS+ Neutrino! event topology and calorimetry. u Neutrino oscillations studied by combining information from both detectors. ➣ Cancellation of systematics. u Far Detector also collected 60 kton-years atmospheric neutrino data. Andy Blake, Lancaster University Slide 6

Neutrino Interactions ν µ Charged Current (CC) Neutral Current (NC) ν e Charged Current (CC) SIMULATION ν X e - µ - muon track hadronic shower electromagnetic shower ν µ + N µ - + X ν + N ν + X ν e + N e - + X Andy Blake, Lancaster University Slide 7

Standard Oscillations u Latest standard oscillation results are based on a combined analysis of accelerator and atmospheric data from MINOS and MINOS+. ➣ Neutrinos, antineutrinos, ν µ disappearance, ν µ ➔ ν e appearance. ➣ Analysis includes 48 kton-years atmospheric neutrino data. u Observed data are well-described by three-flavour neutrino oscillations. Andy Blake, Lancaster University Slide 8

Standard Oscillations u Analysis of three-flavour oscillations yields precision measurements of Δ m 2 32 and sin 2 θ 23 parameters: Normal Hierarchy: Inverted Hierarchy: u The data from MINOS+ improve the standard oscillation measurement, but also significantly enhance searches for new physics. Andy Blake, Lancaster University Slide 9

Sterile Neutrino Oscillations u The wideband L/E coverage of MINOS and MINOS+ generates strong sensitivity to oscillations involving sterile neutrinos. u The MINOS/MINOS+ data have been ν 4 analysed using a “3+1” model of ν e sterile neutrinos: ν μ ➣ 3 active flavours ( ν e , ν µ , ν τ ). ν τ Δm 2 41 ν s ➣ Add 1 sterile flavour ( ν S ) and 1 extra mass state ( ν 4 ). ν 3 ν 2 ⇒ 4 × 4 neutrino mixing matrix. ν 1 u Neutrino oscillations are described by 12 parameters [3-flavour, 4-flavour] :   U e 4 Mass splittings: Δ m 2 32 , Δ m 2 21 , Δ m 2 41 U P MNS U µ 4   Mixing angles: θ 12 , θ 23 , θ 13 , θ 14 , θ 24 , θ 34   U τ 4   CP-violating phases: δ 13 , δ 14 , δ 24 U s 1 U s 2 U s 3 U s 4 ⇒ 6 new oscillation parameters. Andy Blake, Lancaster University Slide 10

Sterile Neutrino Signatures u The combined data from MINOS and MINOS+ are sensitive to the third mass splitting and all three additional mixing angles: (1) ν µ disappearance analysis : ➣ Search for presence of additional oscillations in ν µ CC spectrum due to third mass splitting. ★ Predominantly sensitive to Δ m 2 41 and θ 24 . ➣ Search for anomalous disappearance in spectrum of NC events arising from ν µ ➔ ν s oscillations. ★ Additional sensitivity to θ 24 , plus some sensitivity to θ 34 . (2) ν µ ➔ ν e appearance analysis : ➣ Search for anomalous ν µ ➔ ν e appearance in ν e CC spectrum at energies above three-flavour oscillations. ★ Predominantly sensitive to θ 14 and θ 24 . Andy Blake, Lancaster University Slide 11

Sterile Neutrino Signatures u Sterile neutrino oscillations can occur in both MINOS detectors. In the case of ν µ disappearance : ➣ Small Δ m 2 41 (> Δ m 2 32 ) (10 -3 – 10 -1 eV 2 ) Far Detector: additional oscillations above 3-flavour oscillation maximum. Near Detector: no effect. ➣ Medium Δ m 2 41 (10 -1 – 1 eV 2 ) Far Detector: oscillations become rapid and average out, causing a constant depletion (“counting experiment”). Near Detector: no effect. ➣ Large Δ m 2 41 (1 – 10 2 eV 2 ) Far Detector: constant depletion. Near Detector: oscillations. Andy Blake, Lancaster University Slide 12

ν µ Disappearance Analysis u Previous MINOS sterile analysis * based on Far/Near Ratio ratio of Near and Far energy spectra. ➣ Many systematics cancel in this ratio. u But Far/Near ratio method has limitations: ➣ Uncertainty dominated by Far statistics. ➣ High- Δ m 2 41 oscillations cancel in ratio. u For combined MINOS/MINOS+ analysis, have now developed a two-detector fit . Two-Detector Fit Input oscillation parameters: θ 24 = 0.2; Δ m 2 41 = 80 eV 2 * P. Adamson et al. , Phys. Rev. Lett. 117, 151803 (2016) Andy Blake, Lancaster University Slide 13

Two-Detector Fit u Combine ν µ CC and NC data from MINOS (neutrino-mode) and MINOS+ into single analysis, using simultaneous two-detector fit. u Treatment of 3+1 oscillation parameters Full covariance matrix for same as previous MINOS analysis: CC-selected events ➣ Fitted: Δm 2 41 , Δm 2 32 , θ 23 , θ 24 , θ 34 . ➣ Set to zero: θ 14 , δ 13 , δ 14 , δ 24 . ND ➣ Global best-fits: Δm 2 21 , θ 12 , θ 13 . u Statistical and systematic uncertainties enter fit via covariance matrices. FD ➣ Have incorporated 44 sources of systematic uncertainty. ➣ In particular, now utilise a-priori flux prediction from Minerva * . FD ND ➣ Many uncertainties cancel via matrix cross-terms. * L. Aliaga et al. , Phys. Rev. D 94, 092005 (2016) Andy Blake, Lancaster University Slide 14

Sterile Neutrino Sensitivity Addition of MINOS+ 90% C.L. data and use of new fitting method yield significant improvement in sensitivity compared with previous MINOS analysis. MINOS PRL (2016) : P. Adamson et al ., Phys. Rev. Lett. 117, 151803 (2016) Andy Blake, Lancaster University Slide 15

Observed Energy Spectra CC-selected events NEAR DETECTOR FAR DETECTOR Andy Blake, Lancaster University Slide 16

Observed Energy Spectra NC-selected events NEAR DETECTOR FAR DETECTOR Andy Blake, Lancaster University Slide 17

Exclusion Contours u Confidence limits in ( Δ m 2 41 , θ 24 ) are constructed using the Feldman-Cousins method. ➣ Note: χ 2 is minimised with respect to Δ m 2 32 , θ 23 and θ 34 in each bin of this 2D space. u A strong exclusion limit on the mixing angle θ 24 is obtained over several decades in Δ m 2 41 . u The exclusion limit calculated using the observed data falls within ±2 σ sensitivity band. u Obtain the following 1D limits at Δ m 2 41 =0.5eV 2 : Andy Blake, Lancaster University Slide 18

Comparison with Other Experiments u New MINOS & MINOS+ limit improves upon the previous MINOS analysis. ➣ Limit on θ 24 is world-leading for much of Δ m 2 41 range. u Results increase tension with with hints from global fits * . ➣ e.g. fit from Gariazzo et al. is displayed in ( Δ m 2 41 , θ 24 ) parameter space by setting |U e4 | 2 =0.023. (This fit doesn’t include data from MINOS or IceCube) * S. Gariazzo, C. Giunti, M. Laveder, Y.F. Li, E.M. Zavanin, J. Phys. G43, 033001 (2016) Andy Blake, Lancaster University Slide 19