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1 N e w νµ νe o s c illa t io n s re s u lt s fro m t h e MIN O S E x pe rim e n t J e ff de J o n g (o n b e h a lf o f t h e MIN O S C o lla b o ra t io n ) O x fo rd U n iv e rs it y , A p ril 2 7 MINOS results, 1

2 In it ia l R e s u lt s fo r νµ νe o s c illa t io n s in MIN O S J e ff de J o n g (o n b e h a lf o f t h e MIN O S C o lla b o ra t io n ) O x fo rd U n iv e rs it y , Ma r 1 0 MINOS results, 2

3 So what do we know? They Exist and can be detected! (Take that Pauli) Reines & Cowan 1959, BNL/CERN 1962, DONUT(FNAL) 2000 There are 3 (light) flavours of neutrino: ντ νµ νe constrained by Z-mass measured by LEP experiments(n=2.9840±0.0082) neutrinos have mass Σmi<0.7eV (cosmological constraints), m e<2ev (beta decay) The Mass eigenstates are not the flavour eigenstates. U e1 e = U 1 U 1 U e2 U 2 U 2 U e3 U 3 U MINOS results, 3

4 Neutrinos Oscillate! Produced in flavour states But Propagate in mass states(basic QM) Mass States Weak States νl νi l νi E2 = p2 + m2 νi(t) W > = e -i Et νi > ν born as one weak flavor will become a mixture of weak flavors as it propagates >Σ νf(l) > exp[-il(mj2/2e)] U*f,j νj 2 P = L MINOS results, 4

5 Neutrinos Oscillate! Produced in flavour states But Propagate in mass states(basic QM) Mass States Weak States νl νi l νi E2 = p2 + m2 νi(t) W > = e -i Et νi > ν born as one weak flavor will become a mixture of weak flavors as it propagates P(να νβ) = δαβ 4 R(U αiuβiuαju βj)sin [1.27Δm ij(l/e)] * * 2 2 i>j +2 I(U*αiUβiUαjU*βj)sin[2.54Δm2ij(L/E)] [L] km [E] GeV [ m2] ev2 i>j two-neutrino case: P =sin 2 sin 1.27 m L / E MINOS results, 5

6 PMNS Mixing Matrix Neutrino Mixing is governed by the PMNS Mixing Matrix e 1 0 = 0 c 23 0 s 23 0 s 23 c 23 c 13 0 i s 13 e Atmospheric terms CP s 13 e i 0 c 13 CP Unknown terms c12 s 12 0 s 12 c Solar,reactor terms Can be parameterized with 3 real angles(θ12, θ23, θ13) and 1 complex phase(δcp) For oscillations also need two independent mass scales ( m232, m212) So what do we know? MINOS results, 6

7 PMNS Mixing Matrix Neutrino Mixing is governed by the PMNS Mixing Matrix e 1 0 = 0 c 23 0 s 23 0 s 23 c 23 c 13 0 i s 13 e Atmospheric terms o o Mixing Angles 23=45 ±5 Mass Scales CP s 13 e i 0 c 13 CP Unknown terms c12 s e e normal mass hierarchy m 221= 7.6±0.2 x10 5 ev 2 m2>m1! Normal Mass Hierarchy =34o ±3o 13 11o (90% CL) m3>m2? e s 12 c 12 0 Solar,reactor terms 2 m32 = 2.43±0.13 x10 3 ev 2 Heirarchy? Inverted Mass Hierarchy m232 2 m e e e 2 m12 m 2 23 inverted mass hierarchy MINOS results, 7

8 Whats Left? 1) Is there a non-maximal mixing between the νμ and ντ states? Is θ23 45? 2) What's the mass hierarchy? Is Δm232 > 0? 3) Is there an νe component to the ν3 mass state? Is θ13 0? 4) Is there CP violation in the lepton sector? Is δcp 0? (Is θ13 0?) MINOS can potential address these questions MINOS results, 8

9 Measuring θ13 Best limit by CHOOZ reactor neutrino experiment: disappearance of ν from a reactor 2 e sin 2θ13< m L P e e 1 sin 2 13 sin 4E appearance of νe in a νµ beam m 31 L P e sin 2 13 sin 23 sin 4E MINOS can explore P(νµ νe) MINOS is the first experiment to probe θ13 with a sensitivity below the CHOOZ limit. Phys.Lett.B466: ,1999 MINOS results, 9

10 Matter Effects All neutrinos can interact with electrons in matter via the neutral current (NC) interaction α = e, µ, τ But electron neutrinos can also interact with electrons via the charged current (CC) interaction If electron neutrinos travel through matter (like the Earth) instead of vacuum, the probability to observe them is altered due to the matter effect! MINOS results, 10

11 νe appearance in MINOS e sub-dominant oscillation mode P e sin 23 sin 2 13 sin 1.27 m31 L/E However, as electron neutrinos propagate through matter, they will be affected by matter effects: 2 2 P e sin 23 sin sin A 1 2 A 1 sin A sin A 1 sin A A 1 sin A sin A 1 2 sin 13 cos sin2 12 sin2 23 cos A A 1 2 sin 13 sin sin2 12 sin2 23 G f ne L E A= 2 11GeV = m m m L = 4E O s c illa t io n pro b a b ilit y s e n s it iv e t o : θ1 3, C P -ph a s e δ, a n d t h e m a s s h ie ra rc h y MINOS results, 11

12 First Results F it t in g t h e o s c illa t io n h y po t h e s is t o o u r da t a Plot shows 90% limits in δcp vs. sin22θ13 shown at the MINOS best fit value for Δm232 and sin22θ23. for both mass hierarchies A Feldman-Cousins method was used. Observed 35 events Expected 27 ± 5(stat) ± 2(syst) a 1.5 σ excess MINOS results, 12

13 The MINOS Experiment Iron scintillator calorimeters, functionally identical Far Detector: Spectrum after oscillations 5.4 kt, 8m x 8m x 30m, 484 steel/scintillator planes, veto shield Near Detector Spectrum before oscillations 1 kt, 3.8m x 4.8 m x 15m, 282 steel planes, 153 steel/scintillator planes Steel/scintillator planes: 1-inch thick steel planes alternating with planes of scintillator strips 735 km MINOS results, 13

14 The MINOS Detectors Steel 2.54 cm Fe Extruded PS scintillator strips 4.1 x 1 cm, up to 8m long in FD Scintillator Orthogonal orientations of strips Wavelength-shifting fibre U V planes +/- 450 Clear Fibre cables M64 M16 Jeff depmt Jong, Multi-anode Alternative planes are orthogonal to each other for 3-D reconstruction of events Polystyrene scintillator strips contain wavelengthshifting fibres which are then read out by multianode PMTs M64 for ND, and M16 for FD Scintillator strip width of 4.1cm 1.1 Moliere radii Steel plane thickness of 2.54cm 1.44 radiation lengths University of Oxford MINOS results, 14

15 Detector Calibration Light Injection: - UV LEDs illuminate the fibers directly - Used to monitor gains and linearity Through-going Cosmic Muons: - Drift - change of response with time - Strip-to-strip response variations by channel - Attenuation light attenuation in the fiber - at FD: avg energy ~200 GeV, ~0.5 Hz - at ND: avg energy ~55 GeV, ~15 Hz MINOS results, 15

16 Detector Calibration Absolute Energy Calibration - CalDet - a small scale version of the MINOS detectors (60 planes) - e,µ,p,π beams w/ momenta GeV/c at CERN ~6% Absolute Error Relative Energy Calibration - CalDet/Near/Far relative energy calibration with stopping muons (momentum measured by range) - relative energy calibration is important for an oscillation measurement ~ 2% Relative Error MINOS results, 16

17 The NuMI beam 120 GeV protons 5 or 6 booster batches in MI 4.0x1013 protons on target(pot) per spill(design-3x1013 max) 1.9s rep rate ~10 ms spill window beam power 400 kw(at 270 kw) MINOS results, 17

18 Neutrino Production w/ NuMI Neutrinos at the Main Injector (NuMI) Beam Stats. Beam Stats. ~ 275 kw,1018 POT/day,3x1013POT/10 µs spill Two magnetic focusing horns guide positive mesons down the decay pipe Neutrino beam energy is tunable by modifying the target position wrt the horns. Run in low energy(le) configuration as peak is closer to the expected oscillation minima LE Beam Composition , 1.3 e e MINOS results, 18

19 Integrated POTs New MINOS Results for an exposure of 7x1020 protons-on-target Run 4 Anti-ν running Accelerator Shutdown Run 3 Accelerator Shutdown Run 2 Accelerator Shutdown Run 1 Initial Result (~3e20 POT) This Result (~7e20 POT) MINOS results, 19

20 Neutrino Interactions νµ CC Event νµ µ ν ν Z W N X ν CC Event NC Event N γ 0 π γ (+X) e νe e W N X MINOS results, 20

21 Neutrino Interactions νµ CC Event NC Event ν CC Event e UZ VZ 3.5m long µ track+ hadronic activity at vertex 1.8m short event, often diffuse 2.3m short, with typical EM shower profile MINOS results, 21

22 Electron Neutrino Appearance Analysis Analysis Procedure MINOS selects CC-νe events by shower topology MINOS measures backgrounds in Near Detector before oscillations, predicts Far Detector background after oscillations ND background after νe selection is separated into its components by using different beam configurations The number of ND background events is extrapolated to the FD (oscillations are taken into account) A FD background prediction is obtained => look for an excess of νe events in the FD data. => At largest values only expect 2-3% of FD interactions to be νe MINOS results, 22

23 νµ dissappearance Analysis Primary goal of the MINOS Experiment: Phys.Rev.Lett.101:131802,200 8 measure the νµ CC spectrum at the Far Detector look for νµ disappearance 2008 Results based on 3.4x102 0 POT MINOS results, 23

24 νµ dissappearance Analysis Primary goal of the MINOS Experiment: Phys.Rev.Lett.101:131802,200 8 measure the νµ CC spectrum at the Far Detector look for νµ disappearance Oscillation Parameters 2 sin % CL m232 = 2.43± ev Results based on 3.4x102 0 POT MINOS results, 24

25 The Backgrounds 1) Neutral Current (NC) interactions 2) νµ Charged Current (νµ CC) interactions present at the near detector 3) beam νe Charged Current (beam νe CC) interactions (νe intrinsic to the beam, not due to oscillations) 4) νt Charged Current (ντ CC) interactions From νµ ντ oscillations Far detector only MINOS results, 25

26 νe Selections S e le c t in g νe e v e n t s 29 ton First, data quality cuts are applied beam quality cuts detector quality cuts 4 kton timing cuts cosmic rejection cuts (based on steepness) Fiducial volume cuts Near Detector 1m < z < 5m, r < 0.8m Far Detector 0.5m < z < 14.3m, 16.3m < z < 28m, 0.5m < r < 3.7m νe preselection cuts to reduce obvious backgrounds νe selection pid based on shower topology MINOS results, 26

27 νe Pre-selections track planes < 25 remove obvious long track CC-νµ events track-like planes < 16 remove events where track extends much outside shower MINOS results, 27

28 νe Pre-selections track planes < 25 remove obvious long track CC-νµ events track-like planes < 16 remove events where track extends much outside shower number of showers > 0 events have to have at least one reconstructed shower MINOS results, 28

29 νe Pre-selections track planes < 25 remove obvious long track CC-νµ events track-like planes < 16 remove events where track extends much outside shower number of showers > 0 events have to have at least one reconstructed shower 1.0 GeV < reco. energy < 8.0 GeV hones in on signal region MINOS results, 29

30 νe Pre-selections track planes < 25 remove obvious long track CC-νµ events track-like planes < 16 remove events where track extends much outside shower number of showers > 0 events have to have at least one reconstructed shower 1.0 GeV < reco. energy < 8.0 GeV hones in on signal region at least 5 contiguous shower planes with minimum energy deposition of 1MeV each MINOS results, 30

31 νe Pre-selections track planes < 25 remove obvious long track CC-νµ events track-like planes < 16 remove events where track extends much outside shower number of showers > 0 events have to have at least one reconstructed shower 1.0 GeV < reco. energy < 8.0 GeV hones in on signal region at least 5 contiguous shower planes with minimum energy deposition of 1MeV each Before After Raw MC Estimates MINOS results, 31

32 νe Shower Selection Pre-selections select shower like events, need to distinguish from Create an ANN-11 based on e shower properties Longitudinal Energy Profile by plane architecture? Transverse Energy Profile by strip MINOS results, 32

33 νe Shower Selection Pre-selections select shower like events, need to distinguish Neutral Current νe CC event from MINOS results, 33

34 νe Shower Selection Pre-selections select shower like events, need to distinguish Neutral Current Create an ANN-11 based on EM shower propertie Maximum sensitivity for ANN>0.7 from νe CC event MINOS results, 34

35 νe Shower Selection Pre-selections select shower like events, need to distinguish Neutral Current Create an ANN-11 based on e shower properties Maximum sensitivity for ANN>0.7 Final Signal:Background ratio 1:2 Selection Efficiencies: νe from CC event Signal 42% NC -5.4% CC -0.4% MINOS results, 35

36 Selected ND Data ND provides high-statistics data sample due to proximity to beam source and high event rate MINOS neutrino interactions occur in kinematic region where little experimental data available due to this particle showers in MINOS detectors hard to model => data/mc differences discrepancy is within the uncertainties of the MC model Errors are very similar in both detectors => most cancel out MINOS results, 36

37 Selected ND Data ND provides high-statistics data sample due to proximity to beam source and high event rate MINOS neutrino interactions occur in kinematic region where little experimental data available due to this particle showers in MINOS detectors hard to model => data/mc differences discrepancy is within the uncertainties of the MC model Errors are very similar in both detectors => they cancel out Want to use a data-driven decomposition MINOS results, 37

38 Near Detector Decomposition Standard spectrum consists mostly of NC events and CC νµ with short tracks Some data was taken with beam focusing horns turned off => different spectrum without focusing peak Standard Some other data taken in high-energy beam configuration with a different target position events in those special data are higher true energy => fewer mis-ided CC-νµ High Energy Horn Off MINOS results, 38

39 Data Driven Background Separation HORN-OFF HIGH-ENERGY STANDARD Use these 3 data sets to measure the 3 background components in the standard sample... MINOS results, 39

40 Data Driven Background Separation HIGH-ENERGY HORN-OFF STANDARD MC doesn't model the absolute event rate well BUT the MC does model the relative event rate well For example The relative rate of NC interactions between the standard configuration and the horn off configuration. Similarly: R HE / Std NC,R Off / Std CC,R HE /Std CC,R Off / Std e CC R,R Off / Std NC HE / Std e CC MINOS results, 40

41 Data Driven Background Separation HORN-OFF HIGH-ENERGY STANDARD Using: - Total measured rate in each beam configuration - Relative interaction rates for each background component from the MC simulation Can fit for the background components in the standard sample (in bins of energy) MINOS results, 41

42 Data Driven Background Separation HIGH-ENERGY HORN-OFF STANDARD N Std N Off N HE = N NC N =R =R Off / Std NC HE /Std NC CC N CC N NC R N NC R e Off / Std CC HE / Std CC N CC N CC Off /Std e CC HE / Std e CC R N CC R N CC e e (in bins of energy) MINOS results, 42

43 Data Driven Background Separation NC: (64±5)% νµ-cc: (23±5)% νe-cc: (13±3)% MINOS results, 43

44 Background Prediction How to use the near detector data to make the background prediction at the far detector? For a simple approximation, one need only correct for differences in flux (~1/R2) and fiducial volume between the near and far detectors. For more accurate extrapolation, need to consider beam geometry, oscillation (νµ disappearance), detector effects, etc. These things affect each background component differently we need to extrapolate each background component from ND to FD separately! MINOS results, 44

45 Far Detector Extrapolation We predict the event rate(for each interaction type) in bins of energy by rescaling the ND data by the MC Far/Near ratio: Far detector neutrino energy spectrum will be similar to the Near detector neutrino energy spectrum scaled by 1/R2 (modulo neutrino oscillations) MC provides corrections due to differences between the two detectors MINOS results, 45

46 Data-Driven Signal Prediction To interpret the results in terms of θ1 3, must predict the number of signal events expected as a function of θ1 3 1) Use νµ CC events in the near detector data to get a data-based prediction of the νµ CC spectrum at the far detector (like the νµ disappearance analysis) 2) Apply the νµ νe oscillation probability to estimate the number of νe appearing at the far detector 3) Correct for cross section and selection efficiency to predict the number of signal events selected by the analysis To study signal efficiency: Take a muon-removed event and add a simulated electron simulates a signal-like event with a real hadronic shower! MINOS results, 46

47 Signal Efficiency Correction Apply the muon removal, electron addition process to ND data and MC Find the νe selection efficiency in these signal-like samples The ratio of data to MC efficiency is used to correct the signal efficiency Data-driven signal efficiency = ( ) % MINOS results, 47

48 Systematic Uncertainties most systematics are evaluated by generating special MC with modified parameters in both the Near and Far detectors. This modified MC is used to extrapolate and calculate the difference with the standard results many errors cancel out in the Far/Near extrapolation MINOS results, 48

49 Systematic Uncertainties most systematics are evaluated by generating special MC with modified parameters in both the Near and Far detectors. This modified MC is used to extrapolate and calculate the difference with the standard results many errors cancel out in the Far/Near extrapolation t h e s t a t is t ic a l u n c e rt a in t y do m in a t e s a t o v e r 1 4 % MINOS results, 49

50 Far Detector Prediction Total NC νμ CC beam νe ντ CC Background Prediction for 7x1020 POT (stat) (sys) Expected signal at Chooz limit: 24 events => 3.2σ signal at this limit MINOS results, 50

51 Far Detector Prediction Total NC νμ CC beam νe ντ CC Background Prediction for 7x1020 POT (stat) (sys) Expected signal at Chooz limit: 24 events => 3.2σ signal at this limit Sensitivity MINOS results, 51

52 Side Band Analysis F a r/n e a r Diffe re n c e s It is crucial that we understand our Far/Near differences well for this analysis. Most of them will be taken care of by the MC, however, we want to see if there are unexpected Far/Near differences not taken into account. => It was decided to look at sidebands prior to unblinding the main analysis box. Looked at: - Anti-PID sideband - Muon Removed sideband MINOS results, 52

53 Side Band Analysis-AntiPID ANN < 0.5 Predicted (stat.), observed 327 events, 0.75 excess Signal expected at CHOOZ limit: 13 events Good agreement (region chosen not to be sensitive to signal). Tested the whole FD extrapolation chain + agreement between prediction and data MINOS results, 53

54 Muon Removed SideBand Use muon removed data events in FD and measure selection efficiency for these showers => compare with prediction derived from FD MR MC and ND MR data and MC Average rejection rates (stat. errors only): data: 92.8 ± 0.9 % pred: ± 0.05 % agreement within 0.86σ This sideband is important to test the background shower selection. Agreement is reasonable, within statistical errors. MINOS results, 54

55 Final Box Opening Result of Blind Analysis for an Exposure of 7.0x1020 protons on target MINOS results, 55

56 νe selected FD Data MINOS results, 56

57 νe selected FD Data If θ13 is at the CHOOZ limit MINOS results, 57

58 νe selected FD Data MINOS results, 58

59 νe selected FD Data Background Prediction : 49.1±7.0(stat)±2.7(syst) Observed Signal : 54 Signal Excess : 4.9 events (0.7σ) MINOS results, 59

60 νe selected FD Data Background Prediction : 49.1±7.0(stat)±2.7(syst) Observed Signal : 54 Signal Excess : 4.9 events (0.7σ) MINOS results, 60

61 νe selected FD Data Background Prediction : 49.1±7.0(stat)±2.7(syst) Observed Signal : 54 Signal Excess : 4.9 events (0.7σ) MINOS results, 61

62 Final Contours Final contours calculated using a Feldman Cousins method Results given for normal and inverted mass hierarchies, calculated for MINOS best fit value of: m232= ev 2 The obtained limits are in the case of: 2 =0 sin at 90% C.L., for normal mass hierarchy sin at 90% C.L. for inverted mass hierarchy The obtained best fits are in the case of sin =0.027 sin =0.055 =0 : for normal mass hierarchy for inverted mass hierarchy MINOS results, 62

63 Summary & Outlook F uture and u t u reana A nlys a lyiss is a nsdummary S u m m a ry MINOS observed 54 events with a predicted background of (stat.) (syst.). This small 4.9 event excess yields a limit of sin2(2θ13) < 0.12 at δ=0 for the normal mass hierarchy. The MINOS experiment is the first experiment to have been able to probe the θ13 angle with sensitivity beyond the CHOOZ limit MINOS results, 63

64 Summary & Outlook F u t u re A n a ly s is a n d S u m m a ry MINOS observed 54 events with a predicted background of (stat.) (syst.). This small 4.9 event excess yields a limit of sin2(2θ13) < 0.12 at δ=0 for the normal mass hierarchy. The MINOS experiment is the first experiment to have been able to probe the θ13 angle with sensitivity beyond the CHOOZ limit MINOS will take at least 2x1020 POT more neutrino data this year, and has already accumulated ~2x1020 POT anti-neutrino data Analysis improvements, combined with the additional data, could yield a substantial increase (20%) in sensitivity for an improved analysis next year MINOS results, 64

65 Acknowledgements I would like to thank Anna Holin, Greg Pawloski, Lisa Whitehead & Ryan Patterson for allowing me the use of their slides. The MINOS Collaboration would like to thank the many Fermilab groups who provided technical expertise and support in the design, construction, installation and operation of the MINOS experiment. Thank you to the Accelerator Division for the neutrinos! We also acknowledge the financial support from DOE; NSF; STFC(UK); the University of Athens, Greece; Brazil's FAPESP, CNPq, and CAPES. We are grateful to the University of Minnesota and the Minnesota Department of Natural Resources for hosting us. MINOS results, 65

66 Backup Slides MINOS results, 66

67 Initial Results Pre v io u s MINOS Re s u lt fo r x POT e xp o s u re PRL ( ): Expected: 27 ± 5(stat.) ± 2(syst.) Observed: 35 events Difference: 1.5 σ Th e o b ta in e d lim its a re in th e c a s e o f CP-Vio la tin g p h a s e sin a t 9 0 % C.L., fo r n o rm a l m a s s h ie ra rc h y sin a t 9 0 % C.L. fo r in v e rte d m a s s h ie ra rc h y : =0 MINOS results, 67

68 FD Data Distributions FD d a ta d is trib u tio n s lo o k re a s o n a b le MINOS results, 68

69 Far/Near Differences 2 detectors are very similar but there are small differences Fiducial Volume and flux (geometrical effects and oscillations) Readout patterns: Light level differences due to differences in fiber length Multiplexing in the Far (8 fibers per PMT pixel) Single ended readout in the Near (Double ended in the Far) Photomultipliers (M64 in Near, M16 in Far) Different gains Different front end electronics Different pixel-to-pixel crosstalk patterns Higher rates in the Near detector (hence different readouts) Event Rates Relative energy calibration The certainty to which we know these effects enters as a systematic on the Far/Near extrapolation MINOS results, 69

70 Oscillation Likelihood maybe> MINOS results, 70

71 Decomposition Cross-Check De c o m po s in g t h e N D b a c k g ro u n ds - Mu o n R e m o v a l Me t h o d Muon-removed events are used to model the NC background and an ad-hoc correction of the ND MC using the MR Data/MC ratios on a bin-by-bin basis is carried out: MRcorr. NC =NC Std.MC DATA MR /MC MR corr. MRcorr. CC =Data NC Beam e MINOS results, 71

72 Decomposition Cross-Check C o m pa ris o n o f N D Da ta De c o m po s itio n R e s u lt s Multi-Beam Multi-Beam Multi-Beam The two methods agree well within errors The ND spectra are ready to be extrapolated to the Far Detector MINOS results, 72

73 Near/Far Differences 2 detectors are very similar but there are small differences Fiducial Volume and flux (geometrical effects and oscillations) Readout patterns: Light level differences due to differences in fiber length Multiplexing in the Far (8 fibers per PMT pixel) Single ended readout in the Near (Double ended in the Far) Photomultipliers (M64 in Near, M16 in Far) Different gains Different front end electronics Different pixel-to-pixel crosstalk patterns Event Rates Higher rates in the Near detector (hence different readouts) Relative energy calibration The certainty to which we know these effects enters as a systematic on the Far/Near extrapolation MINOS results, 73