Presentation on theme: "Sensitivity of the DANSS detector to short range neutrino oscillations"— Presentation transcript:
1 Sensitivity of the DANSS detector to short range neutrino oscillations Inaugural Conference of ICISE“Windows on the Universe”Quy Nhon 13/08/2013Sensitivity of the DANSS detectorto short range neutrino oscillationsM.DanilovRepresenting the DANSS Collaboration(ITEP (Moscow) & JINR(Dubna))Detector of the reactor AntiNeutrino based on Solid-state plastic Scintillator (DANSS)
2 There are several ~3σ indications of 4th neutrino LSND, MiniBoone: νe appearanceSAGE and GALEX νe deficitReactor νe deficitIndication of a sterile neutrinoΔm2 ~ 1 eV2Sin22θ14 ~ 0.17=> Short range neutrino oscillations
3 Cosmic muon veto (PS plates) DANSS GoalsReactor monitoring using neutrinos:1. to measure the thermal reactor power with accuracy of 1.5% per day;2. to define the fuel composition and amount of the produced 239Pu with accuracyof 6% in 10 days of measurements;Search for short range neutrino oscillationsDANSS Parameters:IBD detection efficiency ~70%ν counting rateup to 10000/dayBackground rate ~1%Distance to reactor core(center to center)m (change in 5min)Energy resolution~20% at 1MeVCosmic muon veto (PS plates)Sensitive volume ~ 1m3(2500 PS strips)Cu frames (inner partof passive -shielding)Pb (external part of passive -shielding)CH2 + B (n-shielding)Total weight – 13t + lifting gear
4 View of a Module (under construction). DANSS DesignglueWLS--fiber○1.2 mmEach scintillator strip is read out individually by a Silicon Photo Multiplier (SiPM) via a WLS fiber.Sensitivity is ~15 p.e./MeVLight attenuation ~20%/m50 strips are combined into a Module which is also read out by a small PMT(via 2 additional WLS fibers per strip).Sensitivity is ~10 p.e./MeVThe frame of a Module is made of radio-pure electrolytic copper and thus shields the sensitive part against insufficiently pure components of front-end electronics placed outside the frame.Gd-containinglight-reflectingcoating~6mg/cm2PSSiPMs (CPTA, Moscow)X-planeCopperframesY-planeView of a Module (under construction).
5 DANSS advantages DANSS disadvantages Handling is much safer (non-flammable, non-caustic)no restrictions to move the detector very close to the reactor corehigher neutrino flux => better sensitivity.High segmentation (2500 strips) => space informationbetter IBD signature => stronger BG suppression.possibility of continuose calibration with cosmics for every stripPS is not doped with Gd, but interleaved with itbetter stability of the scintillator.Dual readout with SiPM and usual PMT => better control of systematicDetector on movable platform under reactor => better control of systematiclow cosmic backgroundDANSS disadvantagesWorse energy resolution in comparison with liquid scintillatorRelatively large number of readout channels
6 DANSS position under WWER-1000 reactor at Kalinin NPP Typical reactor buildingwith WWER-10003 GW thermal power238U + (3.5-5)% 235U5*1013Reservoirs withTechnological liquids~ 60 mweCore:h =3.5m = 3.12mDANSS on a movableplatform with a lifting gearDetector distance fromreactor core m(center to center)
7 A small prototype - “DANSSino” Purpose:Study of background conditionsTests of shielding efficiencyMeasurements of trigger ratesProperties:ν p e+ n (Inverse Beta Decay)Efficiency e+ (Prompt) - 47% (E>1MeV)Efficiency n (Delayed) – 28% (E>1 MeV)Calibrationr/a source:60Co22Na137Cs248Cm ~3 n50+50=100 strips20 cm 20 cm 100 cm1/25 of the DANSS40 kg (movable)2 PMT (X odd, Y even)No SiPM readout
8 Background under reactor is order of magnitude lower than on surface Heavy material shielding increases muon induced IBD background(and IBD detection efficiency)
9 Clear correlation between reactor power and DANSSino counting rate Rate of neutrino-like events detected per dayReactor powerRate of neutrino-like events detected per dayReactor power
10 Raw counting rates during reactor ON and OFF periods No change inside shielding!(Hz)Thermal neutrons inside shielding
11 Spectrum simulated for 235U fission Background subtracted rate of neutrino-like events / 0.5 MeV / dayNeutrino rate~ MC expectationsSpectrum simulated for 235U fissionEnergyMeV
12 248Cm Random -n -induced True IBD Delayed signal time distribution for different types of eventsTrue IBDRandom -n-induced248CmT μsec
13 Comparison of counting rates for reactor On and OFF periods for different selection criteriaEvidence for neutrino detection (~70/day) with S/B~ 1DANSSino confirmed DANSS design parametersReliable estimates of DANSS sensitivity
14 The role of the source dimensions Δm2 = 2 eV2Sin22θ14 = 0.17Large size of reactor core smears oscillationsbut not too much!
15 Distortions are perfectly seen Ratio of positron spectra at 11m and 9.7m for Δm2 =2eV2, Sin22θ14=0.2(errors correspond to 8 months of running)RE [MeV]Distortions are perfectly seen
16 Sensitivity estimates (shape only) for 1 year (without systematics) Most interesting parameter space is well coveredВВЭР-1000СМ-3 Small core100MW Reactor
17 Summary High granularity, good stability, very low background, high neutrino flux and changeable distance to reactor coreshould allow DANSS to study the most interesting parameter region ofpossible oscillations to the 4th neutrino.DANSS design parameters have been confirmed by the DANSSino resultsIn spite of a small size (4% of DANSS),non perfect shielding and μ vetoDANSSino detected about 70 events/day with S/B ~ 1.DANSS data taking will start in 2014Details can be found in arXiv: [physics.ins-det]
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