Double Chooz Energy Scale Calibration and systematics

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1 Double Chooz Energy Scale Calibration and systematics Emmanuel Chauveau First Worshop on Reactor Neutrino Experiment, Seoul October 6, 206 / 48

2 DC Energy Scale definition E vis = N pe f u (ρ, z) f PE/MeV fstab DATA (t) f qnl f equ flnl MC N pe linearised PE calibration f u(ρ, z) non-uniformity correction f PE/MeV absolute energy scale fstab DATA stability correction (drifts) f qnl charge non-linearity correction f equ equalisation of absolute energy scale f MC lnl light non-linearity correction Anchor point of energy scale = n-h target center (using 252 Cf source) 2 / 48

3 NB: DC data taking period configuration FD-I FD-II ND FD-I : far detector during single detector phase 4 PMTs switched off (strong flasher/light noise emitter) FD-II : far detector during multiple detector phase 4 PMTs are switched back ON better uniformity and light collection electronic gain increased by a factor 2 ND : near detector (multiple detector phase) same configuration as FD-II Calibration of 6 effective detectors: FD-I, FD-II and ND DATA, MC 3 / 48

4 Linearised-PE calibration 4 / 48

5 Linearised-PE calibration Quantisation on PMT signal by Flash ADC poor baseline estimation Consequence : electronic DC is function of charge when charge is small gain for PE vs baseline position Gain (charge a.u./pe) slope (non-linearity) intercept readout gain Charge (arbitrary units) gain vs charge for a given basline position Linearised-PE calibration = gain calibration including non-linear correction using 3 parameters : slope, intercept, readout gain (g0) Power cycle of FADC = baseline changes = non-linearity changes (slope) after each powercycle in DC, all PMTs need to be fully re-calibrated 5 / 48

6 Linearised-PE : calibration curves FD-I (203/0/30) Gain 40 FD-II (205/0/07) Gain 300 ND (205/0/26) Gain Charge Charge Charge FD-I FD-II ND Linearised-PE calibration curve (50 channels) FD-I FD-II FD-I FD-II 30 ND 40 ND G Slope 6 / 48

7 Linearised-PE : calibration curves FD-I (203/0/30) Gain 40 FD-II (205/0/07) Gain 300 ND (205/0/26) Gain PE PE PE FD-I FD-II ND Linearised-PE calibration curve (50 channels) FD-I FD-II FD-I FD-II 30 ND 40 ND G Slope 6 / 48

8 Linearised-PE : stability of calibration constants G0 FD-II Slope FD-II /0/ /0/ /0/ /0/07 G0 ND Slope ND /02/ /02/ /0/ /0/26 7 / 48

9 Linearised-PE : absolute PE Calibration ( alpha calibration ) Gain is measured with multiple PE fit G = α σ2 µ assuming α = Absolute scale α defined imposing : PE = PMT multiplicity (isolate from charge bias) Total PE DC-III (Gd-n) Preliminary PMT multiplicity PMT multiplicity = Total PE (at low charge region) MeV (calorimetric PE) Poisson Corrected Multiplicity α = Multiplicity TotalPE with Multiplicity = N PMT ln( N hits N PMT ) measurement of absolute scale with n-h capture from 252 Cf center (then drift of alpha scale are estimated with spallation n-h capture) 8 / 48

10 Uniformity corrections 9 / 48

11 Uniformity Maps gamma catcher target vertex are reconstructed with charge+time distribution of PMT data subdivide detector in bins (ρ, Z) measure for each bin the mean PE(ρ, Z) of n-h spallation capture build and interpolate a 2D map PE(ρ, Z)/PE(0, 0) 0 / 48

12 Uniformity Maps for DATA and MC target gamma catcher FD-I FD-II : more uniform (4 PMTs switched back on) FD-II vs ND : attenuation length of target LS smaller for ND some small difference in PMT orientation (measured with position survey) differences are understood with MC / 48

13 Uniformity Maps : Asymmetry DATA - MC Asymmetry : 2 (DATA - MC) / (DATA + MC) FAR DETECTOR I FAR DETECTOR II NEAR DETECTOR target non uniformity reproduced at % level same imperfections of MC wrt all detectors 2 / 48

(Evis : drift corrected) 3 build asymmetry DATA-MC of residual map : 2 (DATA - MC) / (DATA + MC) 4 uniformity

14 Uniformity systematics Usage of interleaved maps : runs are divided uniformly in 2 groups build non-uniformity correction with one group of runs map (PE) 2 build of residual map with the second group map 2 (Evis : drift corrected) 3 build asymmetry DATA-MC of residual map : 2 (DATA - MC) / (DATA + MC) 4 uniformity systematics = RMS of all bins of asymmetry map (driven by stats) ND DATA uniformity (map ) ND DATA residual (map 2) 3 / 48

15 Uniformity systematics Usage of interleaved maps : runs are divided uniformly in 2 groups build non-uniformity correction with one group of runs map (PE) 2 build of residual map with the second group map 2 (Evis : drift corrected) 3 build asymmetry DATA-MC of residual map : 2 (DATA - MC) / (DATA + MC) 4 uniformity systematics = RMS of all bins of asymmetry map (driven by stats) FD-I FD-II ND T [Gd] 0.2 % 0.24 % 0.23 % GC 0.26 % 0.25 % 0.43 % T+GC [Gd++] 0.25 % 0.25 % 0.39 % 3 / 48

16 Absolute Energy Calibration 4 / 48

17 Absolute energy calibration Definition of MeV scale by H capture with 252 center 252 ND DATA center (n-h) 500 χ 2 / ndf 3.69 / 9 Constant ± 7. Mean.0202 ± 0.00 Sigma ± ND DATA center χ / ndf / 5 n_events 2785 ± 5.3 mean 45.2 ± 0.23 sigma ± 0.86 At e-05 ±.433e s ± Alpha APLHA (absolute PE calibration) PEID PE/MEV ALPHA FD-I FD-II ND PE/MEV FD-I FD-II ND DATA (.053) DATA MC (.00) MC (NB: PE2MEV and ALPHA are fully anticorrelated) systematics associated to absolute calibration : NONE 5 / 48

18 Drift corrections [DATA only] 6 / 48

19 Drift : causes of time instabilities of energy response charge response instability (visible part) partially corrected by linearised-pe calibration Low baseline case baseline High baseline case threshold (pulse reconstruction) larger charge smaller charge PMT hit response instability (invisible part) corrected by measuring drift of α in relative over time energy dependant (large effect for low charge) Low baseline case High baseline case threshold (pulse reconstruction) hit recognised hit not recognised ("zero") 7 / 48

20 Drift of alpha and energy (FD-I) BiPo-22 Variation Variation DC-III (Gd-n) Preliminary Elapsed Days spallation H 0.98 DC-III (Gd-n) Elapsed Days spallation Gd Variation Variation DC-III (Gd-n) 0.96 DC-III (Gd-n) Elapsed Days Elapsed Days 8 / 48

21 Scaling of α drift BiPo 22 spallation n-h spallation n-gd RMS of stability Scaling of alpha best scaling factor BiPo 22 spallation n-h best alpha scale *Evis spallation n-gd 9 / 48

22 Drift of energy after alpha drift correction (FD-I) BiPo-22 Variation Variation Before stability correction After stability correction DC-III (Gd-n) Preliminary Elapsed Days spallation H DC-III (Gd-n) Elapsed Days spallation Gd Variation.04 Before stability correction After stability correction Variation.04 Before stability correction After stability correction DC-III (Gd-n) 0.96 DC-III (Gd-n) Elapsed Days Elapsed Days 20 / 48

23 Drift of BiPo, n-h IBD and n-gd spallation (FD-II, ND) before drift correction Relative energy scale α decay of 22 Po (CHARGE) n-h capture (CHARGE) n-gd capture (CHARGE) DC-IV(Moriond) PRELIMINARY FAR DETECTOR Relative energy scale α decay of 22 Po (CHARGE) n-h capture (CHARGE) n-gd capture (CHARGE) DC-IV(Moriond) PRELIMINARY NEAR DETECTOR Elapsed days since Jan Elapsed days since Jan 205 after drift Relative energy scale α decay of 22 Po ( MeV) n-h capture (2.2 MeV) n-gd capture (8 MeV) DC-IV(Moriond) PRELIMINARY FAR DETECTOR Relative energy scale α decay of 22 Po ( MeV) n-h capture (2.2 MeV) n-gd capture (8 MeV) DC-IV(Moriond) PRELIMINARY NEAR DETECTOR Elapsed days since Jan Elapsed days since Jan 205 FD RMS before Evis after Evis BiPo % 0.32% n-h(ibd) 0.33% 0.23% n-gd(sp) 0.32% 0.8% ND RMS before Evis after Evis BiPo % 0.45% n-h(ibd) 0.40% 0.2% n-gd(sp) 0.57% 0.29% 2 / 48

24 Drift correction : systematics Method : using RMS of EvisID s variation over time convolution of an error function with IBD spectrum Normalized α from Po 2 n-gd (µ-n) Normalized α from Po 2 n-gd (µ-n) 3 0 n-h (IBD) Signal MC (no osci.) 3 0 n-h (IBD) Signal MC (no osci.) 4 0 Error function 4 0 Error function 5 0 Folded spectrum 5 0 Folded spectrum Visible E (MeV) Visible E (MeV) FAR DETECTOR II NEAR DETECTOR FD-I FD-II ND 0.34 % 0.37 % 0.46 % 22 / 48

25 Charge Non Linearity (QNL) 23 / 48

26 MC and DATA QNL some charge non-linearity mainly arise from electronics QNL correction from n-gd/n-h measured with IBD delayed capture possible as LNL(n-H) = LNL(n-Gd) in terms of single gamma energy : n-h MeV / γ = 2.22 MeV/γ n-gd MeV / 3.6 γ = 2.2 MeV/γ only 2 points assume a linear QNL function 24 / 48

27 MC and DATA QNL some charge non-linearity mainly arise from electronics QNL correction from n-gd/n-h measured with IBD delayed capture possible as LNL(n-H) = LNL(n-Gd) in terms of single gamma energy : n-h MeV / γ = 2.22 MeV/γ n-gd MeV / 3.6 γ = 2.2 MeV/γ only 2 points assume a linear QNL function ND DATA 252 center before QNL correction after QNL correction Visible Energy (MeV) 24 / 48

28 MC and DATA QNL Gd/H adjusted to theoric ratio 7.937/2.224 with pol : b QNL + c QNL Evis FD-I DATA x EvisID FD-I MC x EvisID FD-II DATA x EvisID FD-II MC x EvisID ND DATA x EvisID ND MC x EvisID QNL correction.03 FD-I DATA FD-I MC.02 FD-II DATA FD-II MC.0 ND DATA ND MC Visible Energy (MeV) 25 / 48

29 2 2 2 QNL systematics QNL build to align n-gd/n-h using IBD delayed (uniform correction) but non-uniformity of QNL is observed with 252 Cf along Z-axis build QNL systematics from remaining QNL MC-to-DATA : error on slope c QNL and intercept b QNL from RMS with correlation of c QNL vs b QNL (for final fit) FD-I Z-axis χ / ndf / 42 p ± FD-II Z-axis χ / ndf.738e-05 / 2 p ± ND Z-axis χ / ndf 3.976e-05 / 3 p ± p ± p ± p ± RMS x RMS x RMS x RMS y RMS y RMS y QNL slope QNL slope QNL slope QNL intercept QNL intercept QNL intercept FD-I FD-II ND b QNL = ± b QNL = ± b QNL = ± 0.00 c QNL = 0 ± c QNL = 0 ± c QNL = 0 ± anti-correlation b QNL / c QNL = (all detectors) 26 / 48

30 IBD n-h equalisation 27 / 48

31 IBD n-h scale equalisation Ultimate correction factors to align absolute energy scale of 6 detectors to bring their IBD H peak to MeV (therefore Gd to MeV with QNL) This corrects all remaining imperfection of calibration: uniformity, stability, etc. FD-I DATA FD-I MC FD-II DATA.007 FD-II MC ND DATA.0039 ND MC IBD n-h IBD n-gd 3 FD-I DATA FD-I DATA FD-I MC FD-I MC 2 FD-II DATA 0.8 FD-II DATA FD-II MC 0.6 FD-II MC ND DATA ND MC 0.4 ND DATA ND MC before inter-detector QNL and IBD n-h equalisation 28 / 48

32 IBD n-h scale equalisation Ultimate correction factors to align absolute energy scale of 6 detectors to bring their IBD H peak to MeV (therefore Gd to MeV with QNL) This corrects all remaining imperfection of calibration: uniformity, stability, etc. FD-I DATA FD-I MC FD-II DATA.007 FD-II MC ND DATA.0039 ND MC IBD n-h IBD n-gd 3 FD-I DATA FD-I DATA 2 FD-I MC FD-II DATA 0.8 FD-I MC FD-II DATA FD-II MC 0.6 FD-II MC ND DATA ND MC 0.4 ND DATA ND MC after inter-detector QNL and IBD n-h equalisation 29 / 48

33 Light Non Linearity (LNL) 30 / 48

34 TARGET GAMMA CATCHER Light Non Linearity in DC Light non linearity araised from scintillation quenching (Birks) and Cerenkov light NEUTRINO TARGET FD-I TARGET ND TARGET.. DATA DATA MC MC Evis / Etrue Evis / Etrue Single Energy (MeV) γ FD-II TARGET : no data 0.85 ⁶⁸Ge ¹³⁷Cs ⁶⁰Co ⁴⁰K ²³²Cf ²⁰⁸Tl n-c Single Energy (MeV) γ GAMMA CATCHER FD-I GAMMA CATCHER FD-II GAMMA CATCHER ND GAMMA CATCHER... DATA DATA DATA.05 MC.05 MC.05 MC Evis / Etrue 0.95 Evis / Etrue 0.95 Evis / Etrue Single Energy (MeV) γ Single Energy (MeV) γ Single Energy (MeV) γ still some calibration points missing (source and environmental γ) target : good agreement of LNL between DATA and MC gamma catcher : kb in MC sligthly overestimated 3 / 48

35 LNL correction for MC Need to correct MC LNL to match DATA LNL NEAR DETECTOR.04 NT GC Weighted CV MC / Evis DATA Evis Single γ Energy (MeV) Fit function (arbitrary) : a LNL /Evis + b LNL Gd analysis : use NT curve with associated fit error Gd++ analysis : weighted with IBD proportion (NT: , GC: 0.574) 32 / 48

36 LNL correction (Gd++) a LNL /Evis + b LNL Fully UNCORRELATED correction FAR DETECTOR I.04 NT GC Weighted CV FAR DETECTOR II.04 NT [FD-I] GC Weighted CV NEAR DETECTOR.04 NT GC Weighted CV MC / Evis DATA Evis MC / Evis DATA Evis MC / Evis DATA Evis Single γ Energy (MeV) Single γ Energy (MeV) Single γ Energy (MeV) FD-I FD-II ND a LNL ± ± ± b LNL ± ± ± a LNL and b LNL correlation = - (constrained by LNL MeV) 33 / 48

37 LNL correction (Gd++) a LNL /Evis + b LNL Fully CORRELATED correction FAR DETECTOR I.04 NT GC Weighted CV FAR DETECTOR II.04 NT [FD-I] GC Weighted CV NEAR DETECTOR.04 NT GC Weighted CV MC / Evis DATA Evis MC / Evis DATA Evis MC / Evis DATA Evis Single γ Energy (MeV) Single γ Energy (MeV) Single γ Energy (MeV) FD-I, FD-II, ND a LNL ± b LNL ± a LNL and b LNL correlation = - (constrained by LNL MeV) (CV is average CV of previous slide and error covering all blue band of previous slide) 34 / 48

38 Summary of Systematics on Energy Scale 35 / 48

39 Summary of energy model (Gd) Energy model and systematics introduced in final fit to Evis MC : Evis MC Evis x (a LNL /Evis + b LNL ) x b st/u x (b QNL + c QNL x Evis) (simplified in a latter step as a + b x Evis + c x Evis 2 ) FD-I FD-II ND correlated a LNL ± ± ± ± b LNL.0057 ± ± ± ± b st/u ± ± ± x b QNL ± ± ± 0.00 x c QNL 0 ± ± ± x a LNL b LNL b st/u b QNL c QNL a LNL b LNL b st/u b QNL c QNL correlation matrix identical for FD-I, FD-II and ND 36 / 48

40 Summary tables (Gd++) Evis MC Evis x (a LNL /Evis + b LNL ) x b st/u x (b QNL + c QNL x Evis) (simplified in a latter step as a + b x Evis + c x Evis 2 ) FD-I FD-II ND correlated a LNL ± ± ± ± b LNL ± ± ± ± b st/u ± ± ± x b QNL ± ± ± 0.00 x c QNL 0 ± ± ± x a LNL b LNL b st/u b QNL c QNL a LNL b LNL b st/u b QNL c QNL correlation matrix identical for FD-I, FD-II and ND 37 / 48

41 Energy Resolution 38 / 48

42 Energy Resolution FAR DETECTOR I Energy Resolution σ/µ (%) ¹³⁷Cs ⁶⁸Ge n-h (²⁵²Cf) ⁶⁰Co DC-IV preliminary n-c (spallation) DATA MC n-gd (²⁵²Cf) Visible Energy (MeV) all calibration target center, except 37 Cs in guide tube n-c from spallation (DATA) and IBD (MC) worse energy resolution because not point source (integrated over GC volume) fit function: σ E vis = a 2 E vis + b 2 + c2 E 2 vis a: statistical b: constant c: electric noise FD-I FD-II ND a 7.84 ± 0.0 % 7.92 ± 0.7 % 8.46 ± 0.09 % b.87 ± 0.06 %.66 ± 0. %.58 ± 0.0 % c 2.49 ± 0.29 % 2.3 ± 0.35 % 2.32 ± 0.2 % 39 / 48

43 Energy Resolution FAR DETECTOR II Energy Resolution σ/µ (%) ¹³⁷Cs n-h (²⁵²Cf) DC-IV preliminary n-c (spallation) DATA MC n-gd (²⁵²Cf) Visible Energy (MeV) all calibration target center, except 37 Cs in guide tube n-c from spallation (DATA) and IBD (MC) worse energy resolution because not point source (integrated over GC volume) fit function: σ E vis = a 2 E vis + b 2 + c2 E 2 vis a: statistical b: constant c: electric noise FD-I FD-II ND a 7.84 ± 0.0 % 7.92 ± 0.7 % 8.46 ± 0.09 % b.87 ± 0.06 %.66 ± 0. %.58 ± 0.0 % c 2.49 ± 0.29 % 2.3 ± 0.35 % 2.32 ± 0.2 % 40 / 48

44 Energy Resolution NEAR DETECTOR Energy Resolution σ/µ (%) ¹³⁷Cs ⁶⁸Ge n-h (²⁵²Cf) ⁶⁰Co DC-IV preliminary n-c (spallation) DATA MC n-gd (²⁵²Cf) Visible Energy (MeV) all calibration target center, except 37 Cs in guide tube n-c from spallation (DATA) and IBD (MC) worse energy resolution because not point source (integrated over GC volume) fit function: σ E vis = a 2 E vis + b 2 + c2 E 2 vis a: statistical b: constant c: electric noise FD-I FD-II ND a 7.84 ± 0.0 % 7.92 ± 0.7 % 8.46 ± 0.09 % b.87 ± 0.06 %.66 ± 0. %.58 ± 0.0 % c 2.49 ± 0.29 % 2.3 ± 0.35 % 2.32 ± 0.2 % 4 / 48

45 Raw Charge vs Calibrated Energy 42 / 48

46 Raw Charge vs Calibrated Energy (FD-I) FAR DETECTOR I - IBD n-captures 500 raw charge FAR DETECTOR I - IBD n-captures 3 0 raw charge 000 visible energy 0 2 visible energy DC-IV preliminary Energy (MeV) DC-IV preliminary Energy (MeV) BLACK: raw charge x constant RED: visible energy (ESv) (calibrated with n-h peak) impact of energy reconstruction on energy resolution correction on Gd peak (linearised PE and QNL correction) remarkable accuracy already obtained with raw charge 43 / 48

47 Raw Charge vs Calibrated Energy (FD-II) FAR DETECTOR II - IBD n-captures FAR DETECTOR II - IBD n-captures raw charge visible energy 3 0 raw charge visible energy DC-IV preliminary Energy (MeV) 0 - DC-IV preliminary Energy (MeV) BLACK: raw charge x constant RED: visible energy (ESv) (calibrated with n-h peak) impact of energy reconstruction on energy resolution correction on Gd peak (linearised PE and QNL correction) remarkable accuracy already obtained with raw charge 44 / 48

48 Raw Charge vs Calibrated Energy (ND) NEAR DETECTOR - IBD n-captures 8000 raw charge visible energy DC-IV preliminary Energy (MeV) NEAR DETECTOR - IBD n-captures DC-IV preliminary raw charge visible energy Energy (MeV) BLACK: raw charge x constant RED: visible energy (ESv) (calibrated with n-h peak) impact of energy reconstruction on energy resolution correction on Gd peak (linearised PE and QNL correction) remarkable accuracy already obtained with raw charge 45 / 48

49 Energy Correlation 46 / 48

50 252 Cf prompt spectrum Prompt 252 Cf : large range of γ with Etot of 0 20 MeV direct comparison of energy scale with same source placed in FD and ND target center for high statistics run 252 Prompt Fission NT center FAR DETECTOR Asymmetry % / ndf 2 χ 55.9 / p ± NEAR DETECTOR p ± Visible Energy (MeV) no sign of relative ± 0.2 % in 0 0 MeV 47 / 48

51 48 / 48

Double Chooz Energy Scale Calibration and systematics

Double Chooz Energy Scale Calibration and systematics Emmanuel Chauveau First Worshop on Reactor Neutrino Experiment, Seoul October 6, 206 / 48 DC Energy Scale definition E vis = N pe f u (ρ, z) f PE/MeV