Double Chooz Experiment Status Jelena Maricic Drexel University

Double Chooz Experiment Status Jelena Maricic, Drexel University (for the Double Chooz Collaboration) September, 27 th, SNAC 11

Double Chooz Collaboration

Outline • Neutrino detection and 13 measurement • Overview of the Double Chooz detector • DC far preliminary data • Antineutrino anomaly and consequences for Double Chooz • Summary and outlook

NEUTRINO DETECTION AND 13 MEASUREMENT

Reactor Neutrino Detection Signature • Reactors as neutrino sources: Chooz: P =2 x 4. 25 GWth N ~2 x 1021 s-1 Neutrino detection via inverse decay Target: Distinctive two-step signature: Gd doped -prompt event scintillator Photons from e+ annihilation Ee = E + 0. 8 Me. V + O(Ee/mn) -delayed event 1 g/l Gd Photons from n capture on in LS dedicated nuclei (Gd) t ~ 30 s E ~ 8 Me. V Gadolinium J. Maricic-Double Chooz 5

Site in French Ardennes 300 mwe Hill topology 1115 m Started 12/10 Physics data taking 04/11 998 m West Reactor East Reactor 351 m France 465 m 115 mwe Flat topology Jelena Maricic, Drexel U Start in early 2013 6

The - New – Concept – 2 detectors P( e e) = 1 - sin 2(2 13) sin 2( m 231 L/4 E) Background reduction and calibration are very important E = 1 -8 Me. V Pure e flux e, µ, τ e Nuclear Power Station 400 m Near detector e, , Far detector 1050 m Far to near detector signal ratio give information about θ 13 Jelena will Maricic, Drexel U 7

Expected Neutrino Oscillation Signal Two independent sets of information: Normalisation + Spectrum distortion Events/200 Ke. V/3 years sin 2(2 13)=0. 04 sin 2(2 13)=0. 1 sin 2(2 13)=0. 2 Far/Near ratio E (Me. V) Far Detector: ~ 40 000 events/3 y -Reactor efficiency: 80% -Detector efficiency: 80% sin 2(2 13)=0. 12 m 2 atm= 3. 0 10 -3 e. V 2 Near Detector: ~ 5 105 events/3 y -Reactor efficiency: 80% ar. Xiv: hep-ex/0606025 v 4 -Detector efficiency: 80% -Dead time: 50% J. Maricic-Double Chooz 8

Overview if the Double Chooz detector 4 concentric vessels 7 m http: //doublechooz. in 2 p 3. fr/ Neutrino target vessel in the center 7 m J. Maricic, Drexel U Courtesy of T. Lasserre 9

The detector design Near and far detectors are IDENTICAL. Muon Outer-VETO : 7 m -target : 80% dodecane + 20% PXE + 0. 1% Gd Volume for -interaction (d = 2. 3 m, h = 2. 8 m) -catcher : 80% dodecane + 20% PXE 7 m 511 ke. V e 511 ke. V p e+ n Gd ~ 8 Me. V Extra-volume for -interaction Acrylic vessels «hardware» definition of fiducial volume Non-scintillating buffer : same liquid Isolate PMTs from target Muon Inner-VETO : scintillating oil (78 8”PMTs) Shielding : steel 17 cm: >7 Improved background reduction PMT support structure : steel tank, Jelena Maricic, Drexel U optical insulation target/veto area (390 10” PMTs) 10

Inner Detector

Inner Detector Lid

Background in Double Chooz Accidental bkg : • e+-like signal: radioactivity from materials, PMTs, surrounding rock Rate=Re • n signal: n from cosmic spallation, thermalized in detector and captured on Gd (Rn) Accidental coincidence Rate = Re x Rn x Δt Correlated bkg : • fast n (by cosmic ) recoil on p (low energy) and captured on Gd • long-lived (9 Li, 8 He) -decaying isotopes induced by Jelena Maricic, Drexel U 14

Calibration CHOOZ had a 1. 6% absolute detector systematic uncertainty, the best to date. Total uncertainty 2. 7% Bugey is the only experiment that has tried to build identical detectors. Result was 2. 0% relative error. 5. 0% total. Double Chooz goal is 0. 6% relative uncertainty and less than 0. 6% total. Glovebox Fish-line Articulated Arm Deployed in NT and GC: 137 Cs, 60 Co, 68 Ge, 252 Cf Calibration sources: - Natural H n-capture peak - Radioactive sources - Laser and LED system Buffer guide tube Gamma-catcher guide tube LED system

Calibration - 68 Ge in the guide tube Blue – MC Red - data Example of calibration data: 68 Ge in the guide tube. Monte Carlo tuning is ongoing.

DC FAR PRELIMINARY PHYSICS DATA

Data Taking • Data taking with far detector started on April 13, 2011 • >100 days physics data • Trigger rate ~120 Hz • Trigger threshold < 0. 6 Me. V • 75% physics runs • 10% calibration runs

Muons: rate and coincidence • Inner veto 39 Hz • Inner detector 11 Hz t = time between 2 muons in ms • Michel electrons from stopped muons: • = 2. 25 0. 13 s TID – TOD = time in s

Muon correlated events • H ~ 2. 2 Me. V • C ~ 3 -5 Me. V • Gd ~ 8 Me. V • Energy calibration is ongoing

Muon correlated neutron capture on H Stable for 120 days Rate < 0. 1 Hz • Muon correlated neutron capture in hydrogen energy window • 1. 9 – 2. 5 Me. V

Neutrino candidates selection 1) Apply muon veto cut ~1 ms 2) Prompt energy window 0. 7 – 12 Me. V - singles rate ~10 Hz 3) Delayed energy window 6 – 12 Me. V - singles rate ~0. 1 Hz 4) Coincidence window ~ 100 s Result: neutrino candidates (neutrinos + bkg)

Time and Space Distribution • Timing distribution between prompt and delayed signal in Gd energy window (6 -12 Me. V) ~ 30 s. • Spatial distribution between prompt and delayed signal – between 20 -30 cm is expected.

Energy spectrum in delayed Gd window • Energy distribution of delayed signals in the Gd energy window (6 -12 Me. V) peak ~ 8. 3 Me. V

Position Reconstruction of neutrino candidates – delayed signal vertex Gd doped target Detector top view Detector side view Gamma catcher

Daily Neutrino Rate 1 reactor off data ~4000 neutrino candidates in 3 months already exceeds CHOOZ statistics

Summary and Outlook • Double Chooz is detecting neutrinos • Backgrounds are low • We will use Bugey-4 c -s for normalization • Data analysis in progress • T 2 K best fit will be addresses with this data set Near detector