ICEPP Symposium @Hakuba Feb 1 st 005 Current status of TK experiment 1.Introduction.TK experiment 3.Near neutrino detector 4.Summary Jun Kubota (Kyoto University) Feb 1 005 ICEPP@Hakuba005 1
Introduction Next goal of neutrino experiments To explore the neutrino oscillation phenomena beyond the discovery phase Mixing parameters 3 mass state(mass difference) Δm 1 : Solar ν & Reactor experiments 7~8 x 10-5 ev Δm 3 : Atm. ν & Long BaseLine experiments ~3 x 10-3 ev 3 mixing angles & 1 CPV phase Maki-Nakagawa-Sakata Matrix (U ij ) Long baseline experiments ν α > = ΣU αi ν i > Weak Mass eigenstates (Solar + Reactor) (Atm. ν) (Reactor) sin θ=0.-0.3 sin θ~1(>0.9) sin θ<0.1~0. Feb 1 005 ICEPP@Hakuba005
Remaining questions How close θ 3 to π/4? Atmospheric neutrino measurements sin θ > 0.9 (Best fit sin θ ~ 1, Δm = ~3 x 10-3 ev ) Precise measurement of θ 3 and Δm 3 How large is 1 st 3 rd generation mixing? Reactor experiment θ 13 > 0 or θ 13 = 0? sin θ < 0.1~0. @ Δm ~.5 x 10-3 ev ) Measurement of θ 13 How large is the phase δ? Mass Hierarchy? Does sterile neutrino exist? Search for the CP violation Feb 1 005 ICEPP@Hakuba005 3
TK(Tokai to Kamioka) long baseline neutrino oscillation experiment Approved in Dec.003 Conventional ν μ beam 0.75MW beam (1 st phase) Baseline ~ 95km Beam energy ~ 1GeV Will be adjusted to the oscillation maximum SK J-PARC Beam power Far detector Physics 1 st phase 0.75MW Super Kamiokande(50kt) nd phase ~4MW Hyper CP violation Kamiokande(1Mt) ν μ disappearance ν e appearance NC measurements Proton decay Feb 1 005 ICEPP@Hakuba005 4
TK collaboration Japan KEK, ICRR, U. Tokyo, Tohoku U., Hiroshima U., Kyoto U., Kobe U., Osaka City U., Miyagi U. of Education USA UCI, SUNY-SB, U. Rochester, U. Pennsylvania, Boston U., CSU, Duke U., Dominguez Hills, BNL, UCB/LBL, U. Hawaii, ANL, MIT, LSU, LANL, U. Washington Korea Seoul National U., Chonnam National U., Dongshin U., kangwon U., Kyungpook National U., KyuSang National U., SungKyunKwan U., Yonsei U. Poland Warsaw U. Spain U. Barcelona, U. Valencia Switzerland U. Geneva Russia INR Italy U. Roma, U. Bari, U. Napoli, U.Padova France CEA Saclay Canada TRIUMF, U. Alberta, York U., U. Toronto, U. Victoria, U. Regina China IHEP (Inst. of High Energy Phys.) UK RAL, Imperial College London, Queen Mary Westfield College London, U. Liverpool Feb 1 005 ICEPP@Hakuba005 5 Formed in May 003 1 countries, 53 institutions ~150 collaborators (not incl. students)
J-PARC overview J-PARC=Japan Proton Accelerator Research Complex Nuclear Transmutation Material and Life Science Experimental Facility Nuclear and Particle Experimental Facility Linac(350m) 3GeV Synchrotron (5Hz,1MW) Neutrino Experimental Facility 50GeV Synchrotron (0.75MW) Feb 1 005 ICEPP@Hakuba005 6
Construction status Apr. 001: J-PARC Phase 1 construction was started Dec.003: Neutrino experiment was approved! 50GeV Synchrotron (Jan 05) 3GeV Synchrotron (Jan 05) LINAC (Nov 04) In 008, accelerator will be in operation. Start ν experiment physics run in 009! Feb 1 005 February, ICEPP@Hakuba005 004 7 11
Neutrino beam line Proton beam kinetic energy 50GeV (40GeV@T=0) # of protons / pulse 3.3x10 14 Beam power 750kW Bunch structure 8 bunches Bunch length (full width) 58ns Bunch spacing 598ns Spill width ~5μs Cycle 3.53sec Primary Primary Proton proton beam line line 50GeV ring Feb 1 005 ICEPP@Hakuba005 8 80m 130m Decay volume ( Decay volume Cryogenics target Target Target target station station Beam dump ( ) beam dump Muon monitor ( ) Near detector Extraction point muon monitor Near neutrino detector Extraction point ( )
(Ref.;BNL-E889 proposal: Off-axis beam(-3deg) http://minos.phy.bnl.gov/nwg/papers/e889) Quasi-monochromatic beam Beam energy is tunable to maximize the sensitibity! Target & Horn Decay volume θ = ~3deg SK Eν(GeV) 0.8 OA deg 0.4 0 OA 3deg 0 4 6 8 10 Pπ(GeV/c) Expected # of interactions @ SK (OA deg) ν μ total : ~4500/.5kt/yr CC : ~3000/.5kt/yr Feb 1 005 ICEPP@Hakuba005 ν e ~0.% at ν μ peak 9
Schematic view of the detectors p π ν 0m 140m 80m ~ km 95 km Muon monitor @ ~140m - First (spill-by-spill) monitoring of beam direction & intensity First Front Detector @ 80m - Neutrino energy spectrum, intensity and direction - Study neutrino interaction (Second Front Detector @ ~km) -Almost same Eν spectrum as for SK Far Detector @ 95km - Super-Kamiokande(50kt) Neutrino spectra at different distance Feb 1 005 ICEPP@Hakuba005 10 x 10 3 1800 1600 1400 100 1000 800 600 400 00 0 1.5km 95km 0.8km 0 0.5 1 1.5.5 3 3.5 4 4.5 5 Eν (GeV) Difference of spectra Dominant systematic error in KK
41.4m Far detector Super-Kamiokande 50,000 ton water Cherenkov detector (.5.kt fiducial volume) Full water 10 th Dec 00 w/ half coverage(0%) 40m Back to full coverage(40%) Scheduled in winter 005 Feb 1 005 ICEPP@Hakuba005 11
Physics Goal at the 1 st phase(5yrs) Precise measurement of neutrino mixing matrix ν μ disappearance (ν μ ν x ) Accuracy: sin θ 3...1% Δm 3 a few %(< 1 x 10-4 ev ) Discovery and measurement of non-zero θ 13 ν e appearance (ν μ ν e ) sin θ 13...> 0.006 1 st evidence of 3-flavor mixing! 1 st step of a CP measurement Feb 1 005 ICEPP@Hakuba005 1
3-flavor Oscillation ν μ ν e ν τ ν 3 Δm atm Oscillation Probabilities when Δm ν ν 1 Δm sun 1 << Δm3 Δm13 θ 3 : ν μ disappearance P μ x 1 cos 4 ~1 θ 13 θ 13 : ν e appearance sin θ 3 sin ( 1.7 Δ m L / E ) 3 common ν P μ e sin ~0.5 θ 3 sin θ 13 sin ( 1.7 Δ m L / E ) 3 ν Feb 1 005 ICEPP@Hakuba005 13
How to reconstruct neutrino energy CC quasi elastic scattering ν μ + n μ + p ν θμ p μ It is possible to reconstruct Eν from Pμ and θμ E ν = m N m N Inelastic scatterings ν μ + n μ + p + π ν E E π μ μ m + p μ μ θμ p cosθ μ μ Inelastic CC quasi elastic Feb 1 005 ICEPP@Hakuba005 14
Measurement of θ 3, Δm 3 Use 1 ring μ-like events @ SK ν μ + n μ + p (= quasi-elastic enriched sample) to reconstruct neutrino energy ν Clear deficit is expected to be observed in the reconstructed ν energy p μ (E μ, p μ ) ~OA.5deg ~ No oscillation Δm 3 =.7 x 10-3 ev (assuming sin θ 3 =1.0) non-qe sin θ Δm Feb 1 005 ICEPP@Hakuba005 15
Measurement of θ 3, Δm 3 Sensitivities in the 1 st phase δ(δm 3 ) < 1 x 10-4 ev δ(sin θ 3 ) ~ 0.01 Feb 1 005 ICEPP@Hakuba005 16
ν e appearance search θ 13 measurement P e sin θ sin θ sin 1.7Δm L / μ 3 13 ( E ) Upper limit: sin θ 13 < 0.03 ~ 0.05 (@Δm = ~3 x 10-3 ev ) 3 ν Signal events @ SK single ring e-like event (ν e CC quasi-elastic scattering) Possible background sources 1) Beam ν e ν e /ν μ flux ~ 0.%(@peak) ) π 0 production -ring merged to 1-ring ν e + n e + p ν p e (P e, θ e ) Eν π 0 γ γ Feb 1 005 ICEPP@Hakuba005 17
ν e appearance search Expected # of background Event selection Select 1ring e-like events Apply π 0 rejection cut Energy cut (around the oscillation maximum) OA.5deg 5yrs Assuming sin θ 3 =1.0, Δm 3 =.7x10-3 ev ν μ CC (oscillated) 1π 0 ν μ NC coherent DIS Beam ν e 1) Generated in FV,897 43 71,410 5 ) 1ring e-like 5.9 74 41 64 3) e/π 0 separate 0.8 14.6 4.3 6 4) 0.4GeV<E ν rec <1.GeV 0.4 6.3 0.8 1.9 16 Feb 1 005 ICEPP@Hakuba005 18
Sensitivities in the 1 st phase(5yrs) Search for ν e appearance w/ beam MC and full SK detector simulation 35 30 5 0 OA deg., 5yrs Expected Signal+BG sin θ 13 =0.10 sin θ 3 =1.0 Δm =0.003eV Total BG BG from ν μ +antiν μ Δm (ev ) 10-1 10-90% C.L. sensitivities Excluded by CHOOZ 15 10 5 10-3 JHF 5year WBB OAB deg. NBB GeVπ CHOOZ excluded ~ x0 0 0 0.5 1 1.5.5 3 3.5 4 4.5 5 Reconstructed Eν(GeV) Feb 1 005 ICEPP@Hakuba005 19 10-4 10-3 10-10 -1 1 sin θ μe Sensitivity region sin θ 13 >0.006(90%) sin θ 13 >0.018(3σ)
Near neutrino detector Off-axis detector (w/ magnet) 36m 17m SK direction SK 8.5m ν μ and ν e fluxes and energy spectra ν interaction study On-axis detector ν beam center (OA.5deg) Monitor ν beam 0m Φ Feb 1 005 ICEPP@Hakuba005 0
Off-axis detectors Muon Range Detector Measure momentum of μ Tracking detector -Fine Grained Detector consisting of scintillator Target of ν -TPC Measure momentum of μ, p and π UA1 magnet @NOMAD experiment Electron calorimeter Measure energy of EM shower by beam ν e & NC-1π 0 Feb 1 005 ICEPP@Hakuba005 1
On-axis detector OA 0deg OAdeg OA.5deg OA3deg Uncertainly of energy scale δ<eν>/<eν>~4mev/mrad δ(δm )=10-4 ev /mrad Oscillation probability It s necessary to measure ν beam direction w/ high accuracy and control precisely At least 0.5mrad is needed as a measurement accuracy Feb 1 005 ICEPP@Hakuba005
On-axis detector (N-Grid detector) Φν profile 8m beam center -4 0 +4 (m) Monitor neutrino beam direction, profile and stability 8m Iron block ν Tracker Counter μ Veto Counter ~1.5m 0.1m 1m 1m Feb 1 005 ICEPP@Hakuba005 3
On-axis detector (N-Grid detector) 5 modules at one axis 6500 5500 Reconstructed beam center 40 0 0-0 -40 4500-30 -0-10 0 10 0 30 True Beam center -4-0 4 (m) Reconstructed ν beam profile Good linear relation. The accuracy of the center is ~5cm. corresponding to 0.18mard (fulfill the request) Feb 1 005 ICEPP@Hakuba005 4
Summary The first Super-beam Long baseline ν experiment TK (Tokai to Kamioka) experiment was approved Construction was started 5 years to complete (JFY 004~008) Start physics run in 009 Try to discover non-zero θ 13 (sin θ 13 >0.006 @90%C.L.) Precision measurement of θ 3 & Δm 3 (precision x 10) 1 st step to the CP violation in the lepton sector Feb 1 005 ICEPP@Hakuba005 5
Supplement Feb 1 005 ICEPP@Hakuba005 6
Tight e/π 0 separation Shower direction from the beam axis cosθ νe : γ from coherent π 0 tends to have a forward peak Force to find nd ring and E(γ)/E(γ1+γ): The second ring energy is larger for BG Likelihood diff. between 1-ring and -rings Invariant mass: Small for ν e ν μ BG ν e 3.5.5 3 1.5 0.5 1 0 0 0.5 1 1. 1 0.8 0.6 0.4 0. 0 ν μ ν e cosθ νe cosθ νe 0 0.5 1 cosθ νe.5 1.5 1 0.5 0 0 0.5 0.5 1.6 1.4 1. 0.8 1 0.6 0.4 0. 0 ν μ E(γ)/(E(γ1)+E(γ)) E(γ)/E(γ1+γ) ν e 0 0.5 0.5 8 7 6 5 4 3 1 0-500 0 500 0.5 1 0 0 100 00 Feb 1 005 cosθ νe E(γ)/(E(γ1)+E(γ)) ICEPP@Hakuba005 likelihood difference inv. mass (MeV) 7 E(γ)/E(γ1+γ).5 1.75 1.5 1.5 0.75 1 0.5 0.5 0 ν μ likelihood difference Likelihood ν e -500 0 500 Likelihood 3.5.5 3 1.5 3.5.5 3 1.5 ν μ ν e inv. mass (MeV) Mγγ 0.5 1 0 0 100 00 Mγγ
N-Grid detector Event Selection [1] hits in the scintillator. [] No Veto Hits [1] & [] Eν spectrum 0 1 3 4 5 Eν(GeV) Feb 1 005 ICEPP@Hakuba005 8