Double Chooz results at the double detector phase

Transcription

1 Double Chooz results at the double detector phase Thiago Bezerra SUBATECH IN2P3/CNRS, Nantes / France on behalf of the Double Chooz Collaboration Neutrino Oscillation Workshop 2018 Rosa Marina, Ostuni / Italy

2 HIGHLIGHTS 2

3 HIGHLIGHTS -> Double Chooz Near+Far results (as presented at Neutrino 2018) 3

4 HIGHLIGHTS -> Double Chooz Near+Far results (as presented at Neutrino 2018) -> First ND measurement of MCSpF (world-best to date) 4

5 HIGHLIGHTS -> Double Chooz Near+Far results (as presented at Neutrino 2018) -> First ND measurement of MCSpF (world-best to date) -> Spectral bump discussion 5

6 HIGHLIGHTS -> Double Chooz Near+Far results (as presented at Neutrino 2018) -> First ND measurement of MCSpF (world-best to date) -> Spectral bump discussion distortion 6

7 DC-IV FIT RESULTS Data-MC fit including Bugey 4 normalization 7

8 DC-IV FIT RESULTS Data-MC fit including Bugey 4 normalization sin22θ13 = ± (stat.+syst.) Neutrino2018 8

9 DC-IV FIT RESULTS Data-MC fit including Bugey 4 normalization sin22θ13 = ± (stat.+syst.) Neutrino2018 Multi detector fit robust against spectral distortion 9

10 THE SLIDE ON REACTOR NEUTRINOS 10

11 ENERGY RECONSTRUCTION Response uniformity VERY GOOD NEAR - FAR AGREEMENT Time variations No Near-to-Far slope! s =

12 DC STATISTICS / EFFICIENCY Small Gd-target (8.3 t) and only two reactors Total n-capture (TnC) improves statistics factor 2.5! (captures on Gd+H+C -> leak immune!) 12

13 BACKGROUND REDUCTION Delayed E spectrum (data and MC) before and after cuts Cumulative rejection per cut -> Good data/mc agreement for IBD candidates -> Efficient background supression with cuts/vetoes IBD efficiency and background rejection 13

14 SIGNAL AND BACKGROUNDS 210k IBDs 90k IBDs Ev./day FD Ev./day ND Cosmogenic BG (9Li) 2.62 ± ± 1.48 Fast n 2.50 ± ± 0.31 Accidental BG 4.13 ± ± 0.01 IBD candidates S/B>10! 14

15 BOTH REACTORS OFF DATA OFF Total ~25 days (~17 for ND) ND (ev./day) FD (ev./day) OFF-OFF I (2012) ± 1.2 OFF-OFF II (2017) 39.6 ± ± 0.9 Rate+Shape values 38.5 ± ± 0.3 Background understanding All numbers within 1σ 15

16 VALIDATION OF BACKGROUND MODEL 16

17 MORE DC θ13 FITS 17

18 MORE DC θ13 FITS Norm. Pushes up 18

19 MORE DC θ13 FITS FD-II (Flux Cancelation) Pushes up 19

20 MORE DC θ13 FITS Complementary Fits 20

21 NORMALIZATION - ND VS BUGEY4 21

22 NORMALIZATION - ND VS BUGEY4 1.0% unc. NEW! 1.4% unc. New value: 1.5% unc. (arxiv: ) (5.91 ± 0.09) 22

23 NORMALIZATION - ND VS BUGEY4 1.0% unc. NEW! 1.4% unc. DC ND Fission Fraction (2 reactors weighted) 235U -> New value: 1.5% unc. (arxiv: ) (5.91 ± 0.09) 238U -> Pu -> Pu -> B4 (DC fuel corrected) = (5.77 ± 0.08) x cm2/fission 23

24 MORE DC θ13 FITS 24

25 FLUX ERROR BUDGET & SINGLE DETECTOR FIT 25

26 FLUX ERROR BUDGET & SINGLE DETECTOR FIT 26

27 FLUX ERROR BUDGET & SINGLE DETECTOR FIT -> Distortion causes c2 to blow up c2 (x1 -> x4 error) w/ Data: FD+B4 = 105 -> 53 ( 74 DoF) 27

28 FLUX ERROR BUDGET & SINGLE DETECTOR FIT -> Distortion causes c2 to blow up c2 (x1 -> x4 error) w/ Data: FD+B4 = 105 -> 53 ( 74 DoF) FD+ND = 182 -> 93 (112 DoF) 28

29 FLUX ERROR BUDGET & SINGLE DETECTOR FIT -> Distortion causes c2 to blow up -> Corroborated with Data c2 (x1 -> x4 error) w/ Data: FD+B4 = 105 -> 53 ( 74 DoF) FD+ND = 182 -> 93 (112 DoF) 29

30 WORLDWIDE COMPARISON OF RESULTS 30

31 WORLDWIDE COMPARISON OF RESULTS <~2σ difference (systematics!) 31

32 WORLDWIDE COMPARISON OF RESULTS <~2σ difference (systematics!) Intl. Reactor-q13 Workshops: Combined (DC/DYB/RENO) effort to understand systematics 32

33 SPECTRAL DISTORTION COMPARISON (SHAPE ONLY) 33

34 SPECTRAL DISTORTION COMPARISON (SHAPE ONLY) Good agreement to first order 34

35 SPECTRAL DISTORTION COMPARISON (SHAPE & RATE) 35

36 SPECTRAL DISTORTION COMPARISON (SHAPE & RATE) -> Excess in agreement with Flux model 36

37 SPECTRAL DISTORTION COMPARISON (SHAPE & RATE) -> Excess in agreement with Flux model -> Empirical fit: negative slope and double peak -> Width significant larger than energy resolution 37

38 SPECTRAL DISTORTION COMPARISON (SHAPE & RATE) -> Excess in agreement with Flux model -> Empirical fit: negative slope and double peak -> Width significant larger than energy resolution 38

39 SUMMARY -> Three Years of Double Chooz 2 detectors data:

40 SUMMARY -> Three Years of Double Chooz 2 detectors data: > Novel IBD detection : Total Neutron Capture - Improved statistics & systematics 45

41 SUMMARY -> Three Years of Double Chooz 2 detectors data: > Novel IBD detection : Total Neutron Capture - Improved statistics & systematics -> Good background control (S/B > 10) -> Confirmed background model with Reactor-off Data! 46

42 SUMMARY -> Three Years of Double Chooz 2 detectors data: > Novel IBD detection : Total Neutron Capture - Improved statistics & systematics -> Good background control (S/B > 10) -> Confirmed background model with Reactor-off Data! -> New result: sin22q13 = ± (w/ 15 months of data) 47

43 SUMMARY -> Three Years of Double Chooz 2 detectors data: > Novel IBD detection : Total Neutron Capture - Improved statistics & systematics -> Good background control (S/B > 10) -> Confirmed background model with Reactor-off Data! -> New result: sin22q13 = ± (w/ 15 months of data) -> Single Detector Fit protected with a new Flux error budget 48

44 SUMMARY -> Three Years of Double Chooz 2 detectors data: > Novel IBD detection : Total Neutron Capture - Improved statistics & systematics -> Good background control (S/B > 10) -> Confirmed background model with Reactor-off Data! -> New result: sin22q13 = ± (w/ 15 months of data) -> Single Detector Fit protected with a new Flux error budget -> Spectral bump distortion: A rate+shape inspection 49

45 SUMMARY -> Three Years of Double Chooz 2 detectors data: > Novel IBD detection : Total Neutron Capture - Improved statistics & systematics -> Good background control (S/B > 10) -> Confirmed background model with Reactor-off Data! -> New result: sin22q13 = ± (w/ 15 months of data) -> Single Detector Fit protected with a new Flux error budget -> Spectral bump distortion: A rate+shape inspection -> Best MCSpF measurement to date: (5.71 ± 0.06) x cm2/fission 50

46 SUMMARY -> Three Years of Double Chooz 2 detectors data: > Novel IBD detection : Total Neutron Capture - Improved statistics & systematics -> Good background control (S/B > 10) -> Confirmed background model with Reactor-off Data! -> New result: sin22q13 = ± (w/ 15 months of data) -> Single Detector Fit protected with a new Flux error budget -> Spectral bump distortion: A rate+shape inspection -> Best MCSpF measurement to date: (5.71 ± 0.06) x cm2/fission -> sin22q13 sensitivity improvement: extra data and better proton number measurement under consideration -> ~<

47 IN MEMORY OF... Herve de Kerret (Spokesperson ) 52

48 THANK YOU! DOUBLE CHOOZ COLLABORATION 53

49 BACKUPS

50 SCINTILLATOR STABILITY Cf at center FD-I -> Optical and chemical stability of Gd-scintillator (7 years) -> Gd fraction (center) stable on < 0.1% level DAQ upgrade FD-II 55

51 NEUTRINO PRODUCTION / DETECTION Np Pth (t) N (t) f 2 4 L Ef exp Mean cross section per fission (Near detector!) + ν e + p e +n Delayed: n on Gd (H) 30 (200) μs 8 (2.2) MeV Prompt: > 1MeV E vis=e ν 0.8 MeV 56

52 DETECTOR DESIGN Inner detector: Outer Veto: Plastic scintillator Target (r = 1.2 m): - Acrylic vessel t Gd-scintillator (1 g/l Gd) Gamma Catcher (0.55 m): - Acrylic vessel - 18 t liquid scintillator 7m Inner Veto: - Steel - 70 t LS - 78 PMTs (8 ) Buffer (1.05 m): - Steel vessel - 80 t oil PMTs (10 ) 57

53 NEAR TO FAR RATIO Data-to-Data Fit Output Data-to-MC Fit Output Data to data result: sin22θ13 = ±

54 SENSITIVITY PROJECTION -> Double Chooz final sensitivity: 0.009~0.010! 59