Neutrino Directionality Measurement with Double Chooz

Neutrino directionality measurement with Double Chooz

-- Romain Roncin, on behalf of the Double Chooz Collaboration -- -- Applied Anti-neutrino Physics 2013 @ Seoul -- -- 02/11/2013 -- -- Outline --

-- Final aim of our work

-- Evaluate resolution on anti-νe point-like source reconstruction

-- Plan of this talk

-- Motivations of this work

-- Reminder on the Double Chooz experiment

-- Neutrino directionality with neutron capture on Gd

-- Only one reactor on (NEW!)

-- Neutrino directionality with neutron capture on H (NEW!)

Romain Roncin @ AAP 2013 2 -- Motivations of this work --

-- Improving neutrino directionality measurement can lead to a very powerful tool when looking at particular sources such as a core-collapse supernovae, when searching for geo-neutrinos or for nuclear reactor monitoring Core-collapse supernovae

Nuclear reactors Detector

Geo-neutrinos

Romain Roncin @ AAP 2013 3 -- Detecting anti-νe --

-- Anti-νe detection through the inverse beta decay interactions

Prompt signal (positron): + + ⌫¯e + p e + n - e scintillation + annihilation e E ≈ E – T – 0.8 MeV ! e+ prompt ν n

νe p

n n Gd/H

Delayed signal (neutron):

n capture on Gd OR n capture on H E ≈ 8 MeV E ≈ 2.2 MeV delayed delayed Δt ≈ 30 μs Δt ≈ 200 μs

-- Use of liquid scintillator doped with Gd to accelerate the neutron capture but neutron capture on H is alsoRomain possible Roncin @ AAP 2013 4 -- Angular distribution --

-- From P. Vogel and J.F. Beacom (Phys. Rev. D 60, 053003 (1999))

( ) e- Prompt signal positron : + We assume the positron interaction vertex to e be the neutrino interaction vertex

νe p initial n direction

n n θn Gd/H Delayed signal (neutron): ν direction « the neutron must always be emitted in the forward hemisphere »

2 2 2E⌫ ( me) cos(✓n)max = p E⌫ Romain Roncin @ AAP 2013 5 -- Motivations of this work --

-- Studies in literature focused on scintillators doped with high neutron capture cross-section elements (such as Gd), which should minimize neutron diffusion

HOWEVER

-- Directionality studies using neutron capture on H is possible and is potentially very interesting for future large-scale neutrino detectors, such as LENA, JUNO or RENO-50 which will use undoped scintillators

-- H analysis permits also to cross-check the method and the results from Gd analysis

Romain Roncin @ AAP 2013 6 -- The Double Chooz Collaboration --

Brazil France Germany Japan Russia Spain USA

CBPF APC EKU Tübingen Tohoku U. INR RAS CIEMAT-Madrid U. Alabama UNICAMP CEA/DSM/ MPIK Tokyo Inst. Tech. IPC RAS ANL UFABC IRFU : Heidelberg Tokyo Metro. U. RRC Kurchatov U. Chicago SPP RWTH Aachen Niigata U. Columbia U. SPhN TU München Kobe U. UC Davis SEDI U. Hamburg Tohoku Gakuin U. Drexel U. SIS Hiroshima Inst. IIT SENAC Tech. KSU CNRS/ LLNL IN2P3: MIT Subatech U. Notre Dame IPHC U. Tennessee

Spokesperson : H. de Kerret (IN2P3)

Project Manager : Ch. Veyssière (CEA-Saclay)

Web Site : www.doublechooz.org/

Romain Roncin @ AAP 2013 7 -- The Double Chooz far detector --

-- Outer Veto -- 82 m2 of 400 mm thick plastic scintillator strips

-- Inner Veto -- 90 m3 liquid scintillator in a 8 mm steel vessel, seen by 78 10’’ PMTs

-- Buffer Volume -- 110 m3 mineral oil in a 3 mm stain- less steel vessel, seen by 390 10’’ PMTs

-- Gamma-Catcher -- 22.3 m3 liquid scintillator in a 12 mm thick acrylic vessel

-- Neutrino Target -- 10.3 m3 Gd-doped liquid scintillator in a 8 mm thick acrylic vessel Romain Roncin @ AAP 2013 8 -- The Double Chooz experimental site --

Vincent Durand @ Blois 2012

Romain Roncin @ AAP 2013 9 -- The Double Chooz layout --

Nuclear reactors

B1 B2

x -- The Double Chooz far detector y is 1 km away from the two nuclear reactors of the Chooz power plant ϕtrue ≈ 84° -- From the x-axis of the detector frame, the reactors are located at around 84° Double Chooz far detector

Romain Roncin @ AAP 2013 10 -- Direction reconstruction method --

-- Each neutrino candidate is then composed of two signals: -- a prompt signal (Xprompt) prompt -- a delayed signal (Xdelayed)

-- From these two vectors we can build the signal vector: XSignal = Xprompt – Xdelayed

-- We also need to build the unit signal vector: y XSignal = XSignal / |XSignal| delayed

-- The average neutrino wind p is then prompt deﬁned as the average of vectors Xsignal: XSignal delayed x N 1 i p~ = Xˆ N Signal i=1 X

Romain Roncin @ AAP 2013 11 -- Direction reconstruction method --

-- From p we can ﬁnally deduce ϕ (azimuthal angle) and θ (zenithal angle):

py = Arctan p p ✓ x ◆ py p ϕ ✓ = Arctan z

0 p2 + p2 1 px x y @q A -- In this analysis, we used the way Chooz did to compute the uncertainty on the measured angles (Phys. Rev. D 61, 012001 (1999))

p~ B1 B2

« An uncertainty on the measurement of the neutrino direction can be given as the cone around p which contains 68 % of the integral of the p distribution. »

Romain Roncin @ AAP 2013 12 -- The Double Chooz data analysis --

-- This analysis uses data collected from April 13, 2011 to March 15, 2012 for a total live time of 227.9 days for the Gd analysis and 240.1 days for the H analysis

-- We have selected:

-- 8246 anti-νe interactions followed by neutron capture on Gd -- 7498 anti-νe interactions followed by neutron capture on H

-- We present the directionality measurement with these samples in comparison with the corresponding Monte Carlo simulations (MC)

Romain Roncin @ AAP 2013 13 -- Gd neutrino candidates selection --

-- Prompt signal: -- 0.7 < E < 12.2 MeV prompt 14 -- Light noise cuts 102

-- Delayed signal: 12 delayed E (MeV) -- 6.0 < Edelayed < 12.0 MeV

-- Light noise cuts 10 10 -- 2 < ΔT < 100 μs -- Muon cuts 8 -- Rejection of any signal detected in the OV 6 1 -- No additional triggers from 100 μs 4 preceding the prompt signal to 400 μs 2 4 6 8 10 12 14 after it prompt E (MeV)

Phys. Rev. D 86, 052008 (2012)

Romain Roncin @ AAP 2013 14 -- Directionality with Gd neutrino candidates --

-- Distributions of the XSignal components when taking N=8246 neutrino candidates 280 280 #Entries = 8246 #Entries = 8246 260 260

#Entries µ = 0.0055 ± 0.0064 #Entries µ = 0.0585 ± 0.0063 σ = 0.5828 σ = 0.5733 240 240

220 220 200 200 180 180

160 Double Chooz 160 Double Chooz Preliminary Preliminary 140 140 -1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1 -1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1 p (normalised) p (normalised) Nx y 1 ˆ i -- By deﬁning p~ = XSignal we can then calculate the average neutrino wind N i=1 -- p = (0.0055, 0.0585, X-0.0049)

= 84.6 ✓ = 4.7 =9.4 (azimuthal angle) Romain(zenithal Roncin angle @ AAP) 2013 (uncertainty) 15 -- Directionality with Gd neutrino candidates --

-- Azimuthal (ϕ) and zenithal (θ) distributions with both the 8246 neutrino candidates and the MC neutrinos

° 300 ° 900 Gd analysis Gd analysis Double Chooz 280 800 + Data + Data Preliminary 700 260 + MC + MC #Entries / 10 #Entries / 10 600 240 500 220 400 200 300 180 Double Chooz 200 160 Preliminary 100

140 0 -150 -100 -50 0 50 100 150 -80 -60 -40 -20 0 20 40 60 80 φ [°] (azimuthal) θ [°] (zenithal)

700 80 30 80

60 Double Chooz 60 Double Chooz 600 ] (zenithal) 25 ] (zenithal) ° Preliminary ° Preliminary [ 40 [ 40 θ θ 500 20 20 20 400 0 0 DATA 15 MC -20 -20 300 10 -40 -40 200

-60 5 -60 100 -80 -80 Romain Roncin0 @ AAP 2013 16 -150 -100 -50 0 50 100 150 -150 -100 -50 0 50 100 150 φ [°] (azimuthal) φ [°] (azimuthal) -- Directionality with Gd neutrino candidates --

-- cos(α) distribution where α is the angle between the Xsignal vectors and the detector-reactors vector

1000 Gd analysis

#Entries + Data 950 + MC 900

850

800

750

700 Double Chooz Preliminary 650 -1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1 cos α

Romain Roncin @ AAP 2013 17 -- Only one reactor on -- B1

-- The present resolution on direction is comparable to B2 the angular distance between B1 and B2

-- In principle, we should see a narrower distribution when only one reactor is on

-- However, the present statistics is not sufﬁcient ΔϕB1-B2 ≈ 6°

-- With much more statistics, the Double Chooz near detector will help us to deconvolute the two reactors (data in 2014)

Romain Roncin @ AAP 2013 18

-- H neutrino candidates selection --

-- Prompt signal: -- 3.5 < E < 12.2 MeV prompt -- Speciﬁc light noise cuts

-- Delayed signal: -- 1.5 < Edelayed < 3.0 MeV -- Speciﬁc light noise cuts

-- 10 < ΔT < 600 μs -- ΔR < 900 mm -- Muon cuts -- Rejection of any signal detected in the OV -- No additional triggers from 600 μs preceding the prompt signal to 1000 μs after it Phys. Lett. B 723, 66-70 (2013)

-- We decided to focus on directionality measurement by applying a tight selection on our H neutrino candidates to reject background from accidentals

Romain Roncin @ AAP 2013 19 -- Directionality with H neutrino candidates --

-- Azimuthal (ϕ) and zenithal (θ) distributions with both the 7498 neutrino candidates and the MC neutrinos

° 280 ° 800 H analysis H analysis Double Chooz 700 260 + Data + Data Preliminary + MC 600 + MC

#Entries / 10 240 #Entries / 10 500 220 400 200 300 180 200 Double Chooz 160 Preliminary 100

140 0 -150 -100 -50 0 50 100 150 -80 -60 -40 -20 0 20 40 60 80 φ [°] (azimuthal) θ [°] (zenithal)

500 80 25 80 60 Double Chooz 60 Double Chooz ] (zenithal) ] (zenithal) 400 ° Preliminary ° Preliminary [ 40 20 [ 40 θ θ

20 20 15 300 0 DATA 0 MC

-20 10 -20 200 -40 -40

-60 5 -60 100

-80 -80 Romain Roncin0 @ AAP 2013 20 -150 -100 -50 0 50 100 150 -150 -100 -50 0 50 100 150 φ [°] (azimuthal) φ [°] (azimuthal) -- Directionality with H neutrino candidates --

-- cos(α) distribution where α is the angle between the Xsignal vectors and the detector-reactors vector

850 H analysis

#Entries + Data 800 + MC

750

700

650 Double Chooz Preliminary 600

-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1 cos α

Romain Roncin @ AAP 2013 21 -- Consistency between Gd and H analysis --

-- Gd analysis (data and MC) and H analysis (MC) are normalized to the number of entries of H analysis (data)

900 Gd vs H analysis + Gd data and MC (normalized to H data) #Entries 850 + H data and MC

800

750

700

650 Double Chooz Preliminary 600

-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1 cos α

Romain Roncin @ AAP 2013 22 -- Summary and outlook --

-- Retrieving the initial anti-νe direction is possible, in inverse beta decay interactions followed by neutron capture on Gd or on H

-- The Double Chooz directionality analysis is well advanced and covers several different aspects. We have focused on:

-- Direction resolution as deﬁned with the Chooz method -- Neutron capture on Gd --> δ = 9.4° with 8246 events -- Neutron capture on H --> comparable performance, shown on data for the ﬁrst time

-- Possibility to deconvolute the two reactors -- Statistics is still too low

-- Work is on-going to study systematics and to further validate the method

Romain Roncin @ AAP 2013 23 Thank you for your attention

Romain Roncin @ AAP 2013 24 Backup slides

Romain Roncin @ AAP 2013 25 -- Measuring θ13 with nuclear reactors --

-- Due to β-decay of ﬁssion products, nuclear reactors are a free and rich 21 anti-νe source --> around 10 anti-νe per second are emitted in the case of the Double Chooz experiment

-- Studying the disappearance of these anti-νe via the survival probability with two or more identical detectors --> to eliminate systematics from both the anti-νe production uncertainties and the detection efﬁciency

2 2 2 2 m31[eV ]L[m] P (¯⌫e ⌫¯e) 1 sin 2✓13 sin 1.267 ! ⇠ E⌫¯e [MeV] ✓ ◆

Near detector Far detector --> normalization --> oscillation measurement

Romain Roncin @ AAP 2013 26 -- Uncertainty on the direction (δ) --

-- In this analysis, we used the way Chooz did to compute the uncertainty on the measured angles (Phys. Rev. D 61, 012001 (1999))

N i 1 ˆ p~ = XSignal N i=1 X

p~ = p2 + p2 + p2 | | x y z q

p~ B1 B2

-- Using a simple random gaussian generator, we looked for the half-angle cone δ which contains 68 % of the simulated events

Romain Roncin @ AAP 2013 27