reactor θ13(the ultimate measurement?)
Kyoto University (Japan)
December 2012

Anatael Cabrera(アナタエル カブレラ)
CNRS / IN2P3
Double Chooz @ APC (Paris)
12年12月6日木曜日

will the reactor-θ13 be theultimate measurement?
the best for long time…
(so must get it right!)
this seminar: tell you how we are doing that…
12年12月6日木曜日

3

le menu…

•les apéritives...
•neutrino oscillation (a fast reminder)•neutrino oscillation status•global impact of θ13 (a few examples)•les plats…
•reactor neutrinos: (a fast)why?
•review on reactor θ experiments results•le dessert…
•today & tomorrow on reactor θ systematics•conclusions?
13

13

Anatael Cabrera (CNRS-IN2P3 & APC)
12年12月6日木曜日

4neutrino oscillations…
(very fast reminder)
Anatael Cabrera (CNRS-IN2P3 & APC)
12年12月6日木曜日

5neutrino oscillations: a cartoon

Let’s take νμ (a good example) to start with…

“propagation” in vacuum/matter

disappearance experiment goal
appearance experiment goal

Anatael Cabrera (CNRS-IN2P3 & APC)
12年12月6日木曜日

“mixing”: a common phenomenon in Nature
quantum view…

“any weak-flavour να is regarded as linear
combination of 3 (more?) mass νi’s”

example(for 2ν’s)…
νe = α1ν(m1) + α2ν(m2)rough analogy in common life…

να = 0.5•ν1 + 0.5•ν2
Anatael Cabrera (CNRS-IN2P3 & APC)

12年12月6日木曜日

7neutrino oscillations: the true ingredients…

Mixing in the leptonic sector (θ)→PMNS matrix (à la CKM)
Non-degenerate mass spectrum (Δm2)→macroscopic (i.e. overkm’s!!) quantum interference
L,E to be tuned (i.e. experimental setup)→measure P(Lo,ΔΕ)
solution for 2ν’s…

Anatael Cabrera (CNRS-IN2P3 & APC)
12年12月6日木曜日

8

ν-oscillations knowledge…
Anatael Cabrera (CNRS-IN2P3 & APC)
12年12月6日木曜日

3(νe,νμ,ντ)T = U (ν1,ν2,ν3)T, where U looks likethe “CKM”
θ13 <11o & “dirac”δCPθ23~45osub-leading

P(νμ→νμ)σ ~12%“solar”!

θ12~33osub-leading“atmospheric”!

P(νe→νx)P(νe→νe) & P(νμ→νe)

σ ~5%

σ ~2%

σ ~6%

knowledge on
θ13 & δCP [later]
Fogli et al arXiv:1106.6028
12年12月6日木曜日

Anatael Cabrera (CNRS-IN2P3 & APC)

10

Lisi et al opinion (Sept. 2012)

Anatael Cabrera (CNRS-IN2P3 & APC)
12年12月6日木曜日

why θ13?

11•θ must be measured•free parameterr in SM (like in CKM➞ parameter constraints)•test U unitarity (hard)→ sensitive to ≥3νs (steriles?)•a non-zero θ13 is necessary (but not sufficient) to measure δ …
•value important to measure the Mass Hierarchy (MH): ±Δm•θ13 helps to improve our global knowledge…
•via global analyses (1205.5254, 1205.4018, 1209.3023, etc)
•θ23 octant [example later]•δ (Dirac phase) [example later]•θ oscillations observed➞ validation of 3ν oscillation model•confirms 3ν families (like seeing the ν in 2000 by DONUT)•a “discovery”? [within a well established framework]•“solar” & “atmospheric”➞ main channels for oscillations so far•θ13➞ discriminate flavour unification models…
•U + U ➞ quark-lepton unification flavour model•example: Barr et al (hep-ph/1208.6546), etc…
13

PMNS

CP

2

31

CP

13

τ

PMNS

CKM

Anatael Cabrera (CNRS-IN2P3 & APC)
12年12月6日木曜日

12globalθ

13

impact…
Anatael Cabrera (CNRS-IN2P3 & APC)
12年12月6日木曜日

what we all want to know…

13•consistent reactor-θ13 result (all reactor experiments)•good knowledge➞high precision•constraint 3ν model & discriminate against predictions•good agreement➞high accuracy (relevant when high precision)•constraint 3ν model & discriminate against predictions•observe E/L distortion•flux normalisation➞flux(DB or RENO)< flux(DC) [FD only]•consistency between reactor and beam θ13 too…
•beam-θ13 less precise (other observables)➞ (still) it must be consistent•δ rather insensitive to θ13 (but need a θ13≠0)•mass hierarchy is more sensitive to θ13•atmospheric-νs➞ INO, PINGU, ORCA, etc•reactor-νs➞ Daya Bay II (amplitude of interference term)•if inconsistency/tension found➞ new physics/systematics? (exciting!)
CP

Anatael Cabrera (CNRS-IN2P3 & APC)
12年12月6日木曜日

combining baselines→ Δm231 measurement?
3 experiments→ 3x θ13(a) measurements
Ndetected/Nexpected

1206.6017 by DC-Tohoku team (Suekane-sama)

14

(a)
1
0.98
0.96

Daya BayDaya Bay
Double Chooz
Double Chooz
RENO
RENO
-3
Δm2=2.99e , sin22θ=0.089

(a)

(a)

0.94
0.92

(b)
(b)

(b)
0.9
0.88
0

(b)
200

400

600

800

1000

1200 1400 1600 1800 2000
Flux-weighted baseline(m)FIG. 3. Baseline dependence of ν̄e survival probabilities.
Dashed and/or dotted lines are expected oscillation pattern•3x difference
baselines
results
onexperimentθ13
calculatedusing sin2 2θ
in eachand
13 measured
2
MINOS∆m̃32 . results→
The calculated
disappearance
probabilities
2•combine
betterconstraintΔm31
ypotheticalsensitivity
true parameFIG. flux2. Same as fig.-1 but disappearance probab
correspondto the plots
valuesassumingof the expectedlines at their22−3 MINOS)
2
2•beams(i.e.
Δmaveragedbaselines.
line= isexpectationfrom errors
the are calculated from measured sin2 2θ13 .
are ∆m
= 2.32×10
eVTheandsolidsinmeasure2θ
0.092.
(a) 32 (complementary)
their
2
2
probable
∆m
and
sin
2θ
measuredby this analysis.
nes ifmost
disappearance
probabilitiesareas
13 measured
13•important physics (evenif less precision
than MINOS)(b) Allowed regions after combining the three reacments. The contour lines correspond to, from inner
Anataelare,
Cabrera(CNRS-IN2P3& APC)
Same
as fig.-1
but a hypothe
rameters andFIG.
their5.errors
σ,12年12月6日木曜日
2σtwo
anddimensional
3σ significances.
Disappearance
error ofof the fourthwith baseline 2.5 km is added. ∆m̃231
uncertainty
on baseline

15

impact to the θ23 octant…
Anatael Cabrera (CNRS-IN2P3 & APC)
12年12月6日木曜日

16

Lisi et al @ Shenzhen‘2012

Anatael Cabrera (CNRS-IN2P3 & APC)
12年12月6日木曜日

17

Lisi et al @ Shenzhen‘2012

Anatael Cabrera (CNRS-IN2P3 & APC)
12年12月6日木曜日

18

impact to δCP info…
Anatael Cabrera (CNRS-IN2P3 & APC)
12年12月6日木曜日

19

Lisi et al @ Shenzhen‘2012

Anatael Cabrera (CNRS-IN2P3 & APC)
12年12月6日木曜日

20

Lisi et al @ Shenzhen‘2012

Anatael Cabrera (CNRS-IN2P3 & APC)
12年12月6日木曜日

21

why reactors are so cool?
Anatael Cabrera (CNRS-IN2P3 & APC)
12年12月6日木曜日

22•discovery of neutrinos (1956→ Nobel Prize 1995)•Pauli’s hypothesis (Nobel Prize)•today’s best measurement of “solar” Δm (KamLAND)•LMA solution & high precision “Solar-ν” physics•best (ever?) measurement of θ …
•this talk→ today’s status (+ my prospect) review•very sensitive way to explore Sterile-ν existence…
•very-short baseline experiments➞ “reactor anomaly”•ν industry➞ IAEA non-proliferation•(future) best precision θ /Δm & Mass Hierarchy•Daya Bay II in preparation(?)•complementary input in the neutrino oscillation quest…
•NSI (short L), over-constraint 3ν-model, etc…
2

12

13

12

2

12

Anatael Cabrera (CNRS-IN2P3 & APC)
12年12月6日木曜日

23

KamLAND’s E/L (reactor-νs)

the most beautiful (to me) E/L so far...
KamLAND-2008

Anatael Cabrera (CNRS-IN2P3 & APC)
12年12月6日木曜日

the coolest reason for us...

24

P(νe→νe) ~ 1 - sin2 (2θ13) sin2(Δm232Lo/E)[plot: E = 3MeV, sin2 (2θ13) = 0.1, Δm232=2.5x10-3eV2]

Solar Δm212
Dominated“near”“far”
detector detector
(ND)
(FD)
Atmospheric Δm232
Dominated

ND→ reduce all correlated systematic uncertainties
ND→ isolates from other physics (reactor anomaly→ fast oscillation)
Anatael Cabrera (CNRS-IN2P3 & APC)
12年12月6日木曜日

25

reactor monitor

ON

OFF

Backgrounds always ON (radio-activity & μ-related)➞ signal can be OFF (or significantly reduce)[ask your solar-neutrino colleagues how cool this might be…]
Anatael Cabrera (CNRS-IN2P3 & APC)
12年12月6日木曜日

26

reactorθ

13

measurement…
Anatael Cabrera (CNRS-IN2P3 & APC)
12年12月6日木曜日

θ13 measurement by reactors

27•3 experiments➞ Daya Bay (DB), Double Chooz (DC) & RENO•θ best measurement worldwide from reactors•hard to improve (or re-trigger dedicated experimental activity)•θ13 measurement to ~5% precision (eventually)➞ use by beams•high precision➞ due to multi-detector technique•high accuracy➞ due to several experiments (any bias?)•oscillation signature➞ θ13 measure via both rate+shape•rate-only = “any deficit” is numerically associated to θ13 (BG, etc)
•results are rate driven➞ only DC uses shape to some extent•beams to use the “reactor θ13”➞ further insight in neutrino oscillations•ν appearance: first appearance experiment (T2K➞ 5σs soon!!)•rich physics…
•O(1%) precision measurement of Δm 32, θ23 (T2K, NOνA)•further (with some luck)➞ δ and MH (also with atmospheric)•over-constraint 3ν oscillation scenario➞ NSI, sterile, exotic, etc
13

e

2

Anatael Cabrera (CNRS-IN2P3 & APC)
12年12月6日木曜日

28

highlights on experiments…

•RENO (1204.0626)•first multi-detector running➞ rate only analysis (229days)•remarkable effort/success by small (rather local) collaboration (Korea)•Double Chooz (1112.6353,1207.6632,1210.3748, today)•the (slow) pioneer: first detector design (influenced the field)•first result (Nov.11) after CHOOZ➞ θ13 large (rate+shape)•small detectors (8t target) & less overburden (still excellent BGs)
•FD+Bugey4 (“ND” via MC)➞ high precision absolute knowledge•best 1 detector results ever (wrt CHOOZ)➞ analysis quality•ND by spring 2014 but 5 publication (+3 prepation)•Daya Bay (1203.1669,1210.6327)•huge multi-detector complex➞ FD running since 25th Dec. 2011
•largest θ13-detection complex➞ full configuration (Sept. 2012)•large detectors (20t) & deepest overburden (low cosmogenic BG)•most precise result today➞ rate-only analysis (139days, 6 detectors)•fantastic first results within 55days of data-taking

Anatael Cabrera (CNRS-IN2P3 & APC)
12年12月6日木曜日

29

reactor-ν detection technology…
Anatael Cabrera (CNRS-IN2P3 & APC)
12年12月6日木曜日

inverse-β decay (a cartoon)…

30

NOTE: n can also capture on H
( à la Reynnes, KamLAND)

Bemporad, Gratta, Vogle. RMP. 2002

•Energy(ν) = Energy(e+) - 0.8MeV•high & well known σIBD [τneutron=(881.5±1.5)s]•1ν manifests via two triggers:
1st event (prompt): e+
2nd event (delay): n-Gd capture (8MeV)•both events are time/space correlatedtime/space coincidence→reduce BG!
Anatael Cabrera (CNRS-IN2P3 & APC)
12年12月6日木曜日

31

a generic θ13-LAND…
Outer μ-Veto
DC: Plastic Scintillator
DB: RPCs

ν-Target
Liquid-Scintillator + 0.1% of Gd

γ-Catcher
Liquid-Scintillator

Light Buffer

Oil (negligible Scintillation)

Inner μ-Veto

DC: Liquid-Scintillator
DB/RENO: Water Cherenkov
Anatael Cabrera (CNRS-IN2P3 & APC)
12年12月6日木曜日

Inner μ-Veto

32

Bufferγ-Catcherν-TargetDouble Choose FD
12年12月6日木曜日

Anatael Cabrera (CNRS-IN2P3 & APC)

4x
33 Inner-Detectors = ν-Target + γ-Catcher +Buffer(common) μ-veto: water Cherenkov pool

Daya Bay FD (now 4 detectors)
12年12月6日木曜日

Anatael Cabrera (CNRS-IN2P3 & APC)

34

θ13 results…
Anatael Cabrera (CNRS-IN2P3 & APC)
12年12月6日木曜日

35

latest Daya Bay (@ Nu2012)…

Anatael Cabrera (CNRS-IN2P3 & APC)
12年12月6日木曜日

36

latest RENO (@ Nu2012)…

Anatael Cabrera (CNRS-IN2P3 & APC)
12年12月6日木曜日

37

latest DCGd-II (@ Nu2012)…

Anatael Cabrera (CNRS-IN2P3 & APC)
12年12月6日木曜日

12/12/3 @ APC(Paris)
official data release38

new results by DC (now)…
Anatael Cabrera (CNRS-IN2P3 & APC)
12年12月6日木曜日

in black data points. Error bars are weighted by number of windows.

select IBD by capturing on H…

1400
1200

EventsEvents39

600

Double Chooz
Preliminary

400
300
200

1000

Double Chooz
Preliminary

3
.
1

500

100
1.6

~
G
B
/
S
1.8

2

2.2

2.4

2.6

2.8

3

Energy (MeV)

800 DATA

MC/data (energy)
difference: <0.5%

Figure 14: Delayed energy distribution of accidental backgrounds from Oﬀ-Time selection (125 windows) shownin black data points. Error bars are weighted by number of windows.

MC

600
400
200
0

1.6

9

1.8

Gd-analysis: S/BG~40
12年12月6日木曜日

2

2.2

2.4

2.6

2.8

3

Energy (MeV)

Anatael Cabrera (CNRS-IN2P3 & APC)

40

killing accidentals: cut on Δd(prompt-delay)…
Eventsexcellent precision on vertex-reco→narrow Δd (correlated events)

6000

Double Chooz
Preliminary

small Δd→ νs 5000
(spatially correlated)
4000

large Δd(spatially uncorrelated)

3000
2000

On-Time1000
00Off-Time

500

1000 1500 2000 2500 3000 3500

ΔR (mm)Anatael Cabrera (CNRS-IN2P3 & APC)
12年12月6日木曜日

t41

DC-II(H) rate+shape θ13 measurement…

cross-check analysis using High QIV event sample yields “2.86 ± 0.25” events/da

BG subtracted…

• Correlated light noise background rate yield is “0.32±0.07” events/day. The total ssystematics budget…

• Relative uncertainties for n-H final fit input (see table below, copied from n-H te36284 IBDs (with BG)~240days

Source of uncertainty
Total statistical error
Accidentals
Li-9
Fast neutrons
Correlated light noise
Energy scale
Detection eﬃciency
Reactorn-H variance
1.05%
0.21%
1.50%
0.61%
0.09%
0.34%
1.57%
1.75%

n-Gd variance
1.12%
0.01%
1.46%
0.54%
N/A
0.32%
1.01%
1.76%

p on target: 6.75x1029±0.3%(T)+1.58x1030±1.0%(GC)Table
1: A comparison of uncertainties in the n-H and n-Gd (DC2ndPub) analyses. H
qP2
as:i,j Mij /Nsignal , where Mij is the relevant covariance matrix, evaluated at sin

with BGs (huge accidentals)…

the total number of signal events predicted at sin2 2θ13 = 0.

• In the output of a rate+shape fit, we find “2.57 ± 0.35” events/day for the fast neu
events/day for the 9 Li rate, “0.993±0.007” for the energy scale, and “∆m2 = 2.31×
at “sin2 2θ13 = 0.097 ± 0.048.”• The 1σ error on the best fit sin2 2θ13 includes “0.034” which may be reduced by iin the n-H analysis (“stat” error), along with “0.034” which is not reducible by s

• A frequentist study yields (result pending) exclusion probability for sin2 2θ13 = 0• The result of this fit is compatible with the DC2ndPub result at a probabilit(assuming the systematics are completely correlated) and 84% (assuming the sys
uncorrelated).”• A rate-only analysis yields “sin2 2θ13 = 0.044 ± 0.022 (“stat”) ± 0.056 (“syst”)”.

DC-II(Gd) and DC-II(H) compatible to (68-84)% (depending
on correlation)
Anatael Cabrera (CNRS-IN2P3 & APC)

30: Hydrogen best
fit sin2θ13 (red line) superimposed with data (black points with st
12年12月6日木曜日
Hydrogenbest fit sin2 2θ13 (red line), after subtraction of all BGs,Figure
superimposed
with
data
2

results summary…

42•amazing progress end-2011/2012…
•all results are consistent…
•coherent picture: θ13 is LARGE•coherence test not tight (more precision)•accuracy→most important with higher precision•Daya Bay leads the way (for now)
•redundancy is a must (& on the way)sin2(2θ13)
DCGdI(rate+shape)

0.086±0.051(0.041stat±0.030sys)

DB-I(rate)

0.092±0.017(0.016stat±0.005sys)

RENO-I(rate)

0.113±0.023(0.013stat±0.019sys)

DCGdII(rate)

0.170±0.053(0.035stat±0.040sys)

DCGdII(rate+shape)

0.109±0.039(0.030stat±0.025sys)

DB II(rate)

0.089±0.011(0.010stat±0.005sys)

mparison plot for all sin2 2θ13 measurements, made for the DC2ndPub, with n-H result included.

20

DCHII(rate+shape)
12年12月6日木曜日

0.097±0.048(0.034stat± 0.034sys)

exposurearXiv(days)
1112.6353
96.8
1203.1669
55
1204.0626
229
1207.6632
251
1207.6632
251
1210.6327
139
lastmonday240
Anatael Cabrera(CNRS-IN2P3& APC)

43

N(obs)/N(exp) vs Energy...

E/L disappearance effects…
DC-II (Gd) (June’12)<L>= 1050m•short L→ hard to see rise (low constrain in Δm2)
•rate+shape analysis (+ θ13 below <6MeV)•DC-II(H)→ no structure @ 6MeV

DB (June’12)<L>= 1648m•L/E shape→ more sensitive to Δm2•“healthy” shape but rate only (no p-value)

RENO (April’12)<L>= 1383m•shape: consistent with only θ13?
•rate-only analysis→ all assumed to be θ13

strage behaviour (@ ~6MeV)?➞ rate+shape analysis a MUST!
Anatael Cabrera (CNRS-IN2P3 & APC)
12年12月6日木曜日

44

the θ13 challenge (systematics)…
Anatael Cabrera (CNRS-IN2P3 & APC)
12年12月6日木曜日

θ13 reactor challenges

45•statistical uncertainty•generally all experiments enough (DC a little too small)•δ(flux): flux uncertainty (➞impacts mainly rate)•ND critical➞ eliminates primary reactor flux and spectral shape uncertainties•issue: uncorrelated reactor systematics•δ(detection): detection uncertainty (➞impacts mainly rate)•ND critical➞ eliminates many inter-detector detection systematics•excellent detector understanding (energy-reco and MC)•issue: uncorrelated inter-detector systematics•δ(BG): backgrounds uncertainties (➞impact both rate & shape)•each site a different BG" rate and shape (specially correlated BG)•ND more signal but also more BG➞ shapes can also be different•issue: normalisation and shape of each BG (with reactor ON➞hard!)•warning: high-precision physics (i.e. systematics @ “per-mil” level)•first word (fast)➞ impressive θ (large) measurement “overnight”•final legacy (slow)➞ cross-checks for best θ world knowledge
13

13Anatael Cabrera (CNRS-IN2P3 & APC)
12年12月6日木曜日

it’s all about systematics...

46

my goal: explain to you how systematics are controlled...
(please note per-mil systematics➞ very careful)
FD+Bugey4 (as ND*): dominated δ(reactor flux)=1.7%
DC-II(Gd) rate+shape [2012 June & Dec. via DC-II(H)]multi-detector systematics: dominated by what?
RENO rate-only [April 2012]

Daya Bay rate-only [June 2012]

Total Uncertainty
Systematic Uncertainty

Anatael Cabrera (CNRS-IN2P3 & APC)
12年12月6日木曜日

47

reactor systematics…
Anatael Cabrera (CNRS-IN2P3 & APC)
12年12月6日木曜日

reactors vs detectors interplay…

48

multi-detector: “kill” δ(flux) totally? yes…? (proposals)

Daya BayRENO

DC

δ(flux): 0.8% (DB), 0.9% (RENO), ?(0.1~0.3)% (DC)(“uncorrelated reactor flux uncertainty”)•RENO/DB: ~0.5% (thermal power) & ~0.6% (fission fractions)•extremely hard to improve this (impossible?)•geometry is critical…
•”Rate(FD)/Rate(ND) per reactor and per ND?”
•DB→ δ(flux)=0.8%/√6 (fit)•RENO→ δ(flux)=0.9% (impossible to improve?)•DC: almost isoflux→ δ(flux)≤0.3% (under study)•δ(flux) dominant uncertainty for DB & RENO [→ not DC!]

Anatael Cabrera (CNRS-IN2P3 & APC)

12年12月6日木曜日

49

reactor flux uncertainty…
DC-II (FD+Bugey4) [1.67%] (one detector)
DC(FD+ND) [my prospect: 0.1%]
RENO [0.9%]
Daya Bay [0.8%] (table)
Daya Bay [0.8%/√6 = 0.33%] (fit)Anatael Cabrera (CNRS-IN2P3 & APC)
12年12月6日木曜日

50

BG systematics…
Anatael Cabrera (CNRS-IN2P3 & APC)
12年12月6日木曜日

BG model (CHOOZ+KamLAND)…

51

Neutrinos
Fast-Neutrons/μ-Capture
Cosmogenic (Li) [He dashed]
Accidentals

Below Readout Threshold

Log Number of Entries

is this the full story?
(so far, entirely assumed by all experiments)

0.X
12年12月6日木曜日

”
n
o
o
t
“car
)
e
l
a
c
s
(not to

1.0

<50
3.0
8.0
14.0
Prompt Visible Energy (MeV) Anatael Cabrera (CNRS-IN2P3 & APC)

52

individual measurement…
(all experiments)
Anatael Cabrera (CNRS-IN2P3 & APC)
12年12月6日木曜日

cosmic-μ53

K 206Tl40

Gd+nγ or β-best known BG…
•δBG/Signal→0 (i.e. no rate systematics)•(if large) distort shape @ oscillation region
Gd

n

Α

accidental BG…
Anatael Cabrera (CNRS-IN2P3 & APC)
12年12月6日木曜日

decay β-n [τ~100ms]

9Li

cosmic-μ54
178 msß- < 2.3 MeV
4%n+ß- < 11.9 MeV
49.5 %

11.3 MeVß- < 10.8 MeV
5%ß- < 11.1 MeV
17 %ß- < 13.6 MeV
26%

2.8 MeV

8Be+n

2.4 MeVn

9BestableHe24! : 0.09 MeV

less know BG…
•δBG/Signal→largest (rate systematics)•poorly known shape (MC→KamLAND)

9Li

8He

cosmogenic BG…
98( Li and He)
Anatael Cabrera (CNRS-IN2P3 & APC)
12年12月6日木曜日

cosmic-μ55
IBD Candidates (with BG)
IV-tagged events
BG Spectrum (fit to tagged)

most difficult BG…
•shape varies per detector (acceptance &overburden)→ shapes could mimics θ13•poorly known shape (not easy to MC)

correlated BG…
(fast-n & stopping-μ)Michel epr

Gd

n

Α

Anatael Cabrera (CNRS-IN2P3 & APC)
12年12月6日木曜日

Correlated BG measurement
Events

56

Co

250
200

d
e
t
a
rrel

-n)
H
(
BG

Double Chooz)ndPreliminary
G
(

G

C

-B
d
e
t
a
l
orre

150
100
50
0
0

5

10

15

20

25

30

Energy (MeV)•proton-recoil spectrum @ low energies (very challenging)on nominal
shapeenergy
datadependence→points (Low
Energyfitted spectrum an•neutronsizeof bufferIV-tag),and γ-catchers a constant+ exponential.
•protonquenching effects→ difficult to MC (data-driven)•must measure with data→(DC) IV & OV tagging mechanisms•DB/RENO: extrapolate from high-energy (>14MeV): too naive?
•DC: up to ~25% bias in normalisation (rising shape @ low energies)•BG-spectrum resembles θ13 signature (slope-like)→bias θ13?
Anatael Cabrera (CNRS-IN2P3 & APC)
12年12月6日木曜日

measuring & validating BG model…

57•BG measurement: rate (much easier) & shape (statistics limited knowledge)•CHOOZ BG (reactor OFF: no need for a model)➞ Li (by KamLAND)•BG improves with time: ≤1BG per day•1(all): measure each BG (sample) with reactor ON•cons: sub-sample (different selection) & approximations/extrapolations•corrected/scaled (accuracy?) & complete (new BG?)
•2(DC): fit θ13+BGs (shape analysis) with reactor ON•pro: use knowledge a priori (method-1)→propagate to θ13 (correlations)•cons: interpretation of pull-info (degeneracies) & and lack of knowledge still•3(DC): reactor OFF direct measurement (total rate validation)•pro: direct measurement (no assumptions)→complete (à la CHOOZ)•cons: stats very limited (DC: 1 week only)➞ no info on BG shape•4(DC): observed vs expected correlation•pro: combined use of both reactor ON/OFF→BG rate estimation•5(DC): 2 Integration Periods fit (a la “2-1 reactor” analysis)•validation: θ13 outcome is the same for 2IP~1IP (DC-II)→BG robust!

Anatael Cabrera (CNRS-IN2P3 & APC)

12年12月6日木曜日

58(DC) BG validation and direct
measurement…(examples)
Anatael Cabrera (CNRS-IN2P3 & APC)
12年12月6日木曜日

reactor OFF data (~1 week)…

59

Expected: 28.5±4.5
Observed: 21

DC-I(Gd) Selection(2x more BG)

Expected: 14.8±4.0
Observed: 8

DC-II(Gd) Selection(less BG→μshower-veto)validation with two BG-selections DC-I and DC-II (BG varies by ~2x)
BG(observed) < BG(expected)→fluctuation? σstats <1.5σ, but same trend seen shape-fit!
Anatael Cabrera (CNRS-IN2P3 & APC)
12年12月6日木曜日

rate+shape fit→θ13+BGs measure…

60•fit input: full data + BGs rate&shape measurements (each)•fit output: θ13 & (constraint) re-measurement of BGs (using shape)

signal rich BG rich

•BG(fit) <85% BG (rate-only)→ less subtraction (smaller θ13?)•BG(fit) in excellent agreement with direct reactor-OFF measurements•all other experiment rely on rate BG measurement→ BG bias impact?
•θ13 is approx. the same with 1 or 2 Integration Periods→ result is BG robust

Anatael Cabrera (CNRS-IN2P3 & APC)

12年12月6日木曜日

(only validation) observed vs expected rate…
Double Chooz Preliminary

Z (m)Double Chooz Preliminary

Z (m)

61

2

1.5

2

1.5

1

1

0.5

0.5

0

0

-0.5

-0.5

-1

-1

-1.5

-1.5

-2
0

0.5

1

1.5

2

2.5

3

-2
0

3.5

0.5

1

1.5

2

ρ2 (m2)

2.5

3

3.5

ρ2 (m2)

Candidate Rate (events/day)Figure 6: ν̄e candidates’ prompt reconstructed vertex ρ2 v.s. Z distribution. The right plot include an ap
imate volume boundary of Target and GC vessels.

200
Double Chooz
Preliminary

150

100

50

0
0

50

100

150

200

250

300

Number of Days Since April 13 2011

Figure 7: ν̄e candidates’ daily rate stability after accidentals’ rate subtraction. X-axis shows a calendar day
ing the data taking period since the beginning. Blue data points show a number of candidates after subtra
accidental backgrounds per calendar day. Red points are from MC prediction.

•disappearance (i.e. θ13≠0)→ shallower slope•total BG measurement is intercept (when expected rate→0)•Rate(BG) with and without reactor OFF data point→consistent•reactor-OFF data to constraint θ13→future (stay tuned)5

Anatael Cabrera (CNRS-IN2P3 & APC)
12年12月6日木曜日

summary BGs (@ FD)...

62

δBG/BG BG/S δBG/S max.
(%)(%)(%) signal@FD

accidental correlated[day-1][day-1]cosmo[day-1]“Am-C”[day-1]

BG

δBG

DC-II

0.261±0.002

0.67±0.20

1.25±0.54

X

2.2

0.58

26.4

4.8

1.28

45

DC-II (fit)0.261±0.002

0.64±0.13

1.00±0.29

X

1.9

0.32

16.7

4.2

0.71

45

DC-II (OFF)*

X

X

X

X

1.0

0.40

40.0

2.2

0.89

45

DC (H-n)*73.45±0.16

2.50±0.47

3.00±1.00

X

79.0

1.12

1.4

79.0

1.12

100

RENO

0.68±0.03

0.97±0.06

2.59±0.75

X

4.2

0.75

17.8

5.3

0.94

80

DB (1xFD)~3.30±0.03 ~0.04±0.04 ~0.16±0.11

0.2±0.2

3.7

0.23

6.3

5.3

0.33

70

DB (3xFD)

3x more3x more3x more3x more

11.1

0.40

3.6

5.3

0.19

210

DB (4xFD)

4x more4x more4x more4x more

14.8

0.47

3.2

5.3

0.17

280

•cosmo & correlated BG knowledge is statistics dominated•DB lowest cosmo BGs (largest overburden and reduce Acc-BG)•DC surprisingly (less overburden) best BG/S (excellent δS/BG)➞ highquality analysis (precise BG estimation & 4x validation/cross-checks)
Anatael Cabrera (CNRS-IN2P3 & APC)
12年12月6日木曜日

BG world summary…

63•the worst BGs…
•Acc-BG: DB, but will improve some (cut on Δd)•Cor-BG: RENO, but will improve little (no OV or scint-IV)•claimed measurement is suspicious (6% precision + extrapolation)•Cosmo-BG: RENO, but will improve with showering-μ vetoing•Surprising success DC→shallowest overburden (“deeper” via analysis)•the best BGs…
•DC lowest Acc BG ever (~10x better with cut on Δr)•DB lowest μ-BGs (expected→ deeper+vetoing+huge water pool)•the best understood BGs (i.e. lowest δBG and δBG/BG)…
•DB & DC➞ the best understood BG (lowest δBG and δBG/BG)•the best BG systematics…
•DB best rate BG knowledge (δBG/S)→huge signal and deep overburden)•DC best shape BG knowledge (BG/S)→ exploited in rate+shape analysis•DC powerful redundant BG→ 4x methods (stat limited) to handle BG bias
Anatael Cabrera (CNRS-IN2P3 & APC)
12年12月6日木曜日

64

BG systematics (rate-only analysis)…
DC-II rate-only [1.59%]
DC-II rate+shape [0.88%]

DC-X [my prospect ≥0.3%]
RENO [1.03%]

Daya Bay (3x FD) [0.19%]

Anatael Cabrera (CNRS-IN2P3 & APC)
12年12月6日木曜日

65

final precision on θ13…
Anatael Cabrera (CNRS-IN2P3 & APC)
12年12月6日木曜日

rate-driven uncertainties…

66

uncertainty(%)
flux
reactordetection
efficiency
response

DC-I(rate)

DC-II(rate)

DC-II
(r+s)

DC-II
(OFF*)

RENO(abs & relative)DB(abs & relative)

1.67

1.67

1.67

1.67

2.00

0.90

3.00

0.80

1.14
1.7

0.95
0.3

0.95
0.3

0.95
0.3

1.50
X

0.20
X

1.90
X

0.20
X

1.03

1.03

0.09

0.09

0.08

0.08

0.03

0.03

0.04

0.04

0.02

0.02

background for rate analysis (δBG/S)
2.82
1.49
0.80
X
cosmogenic
0.89
0.55
0.36
X
correlated
0.07
0.01
0.01
X
accidental
X
X
X
X“Am-C”
2.96
1.59
0.88
1.10
BG (Σ)

X

X

0.16

0.16

1.03

1.03

0.19

0.19

syst total
stat total

2.70
0.76

1.38
0.76

3.56
0.99

0.85
0.99

3.58
1.56

2.49
1.10

2.11
1.10

2.22
1.10

DB best multi-detector & DC best single detector*(debatable numbers)
12年12月6日木曜日

Anatael Cabrera (CNRS-IN2P3 & APC)

reactor θ13 rate (ultimate?) knowledge…

67

DC-II rate+shape [June 2012]

Total Uncertainty (with stats)
Systematic Uncertainty

one detector experimentδ(flux): 0.1% (→0.3%)
δ(detection): 0.2%
δ(BG): 0.3% (→0.5%)δ(syst.): 0.36% (0.6%)

DC-X (ND+FD 3years)[my guesstimate @ sin2(2θ13)=0.1]

how about DC(with ND)?

δ(flux): 0.9%
δ(detection): 0.2%
δ(BG): 1.0% (→0.5%)δ(syst.): 1.38% (1.05%)

δ: 0.6%RENO rate-only [April 2012]
δ: 1.4%

Daya Bay rate-only [June 2012]
δ: 1.1%δ(flux): (0.8/√6)% = 0.35%
δ(detection): 0.2%
δ(BG): 0.2% (→0.1%)
δ(syst.): 0.43% (0.40%)

Anatael Cabrera (CNRS-IN2P3 & APC)
12年12月6日木曜日

1.75
sin2(2θ13) systematics breakdown

68

δ(detection)

δ(ΣBG)

1.25
1.00
0.75
0.50

Systematic Uncertainty (%)δ(flux)1.50

0.25
DC-II(r+s)

RENO

DB(0.8%)DB(0.8%/√6)

0
DC-X

only 2 experiments <10% precision→ test accuracy(validate systematics)
Anatael Cabrera (CNRS-IN2P3 & APC)
12年12月6日木曜日

69

what to remember?
Anatael Cabrera (CNRS-IN2P3 & APC)
12年12月6日木曜日

what to remember?

70•θ13 measured by reactor experiments (➞ dominate for long!)•sure!→ precise rate-only (DB) & clean rate+shape (DC)•high precision (uncertainty) & high accuracy (what’s the true value?)•to measure/constrain 3ν oscillation model•high precision on θ13→ final ~5% uncertainty expected•multi-detector→ cancellation of all correlated uncertainties•high accuracy on θ13→ unbiassed measurements?
•rate+shape analysis (E/L & BGs) to measure θ13→a must!
•cross-check among all experiments→ on-going effort (transparent)•different sites/BGs/systematics/baselines,etc→ the ONLY way!
•regardless θ13 is LARGE•…if you were waiting for this, please go ahead! :-)•combined θ13 (a few years time)→best θ for very long!
13

Anatael Cabrera (CNRS-IN2P3 & APC)
12年12月6日木曜日

71

Anatael Cabrera
CNRS/IN2P3
APC (Paris)
anatael@in2p3.fr

	 thank you…
Anatael Cabrera (CNRS-IN2P3 & APC)
12年12月6日木曜日