J-PARC neutrino experiment (T2K) and future Takasumi Maruyama (KEK) On behalf of T2K collaboration and LAr R&D group

Particles and interactions Strong interaction Particles which make material Intermediate particles u c t g Electro-magnetic interaction Quarks; make nucleon (nuclear) γ d s b νe νμ ντ W+ W- Z Lepton; company of electron e μ τ Weak interaction H ? ? Particles which gives mass Higgs particle(s)

Particles and interactions Strong interaction Particles which make material Intermediate particles u c t g Electro-magnetic interaction Quarks; make nucleon (nuclear) γ d s b νe νμ ντ W+ W- Z Lepton; company of electron e μ τ Weak interaction H ? ? Particles which gives mass Higgs particle(s)

Neutrino Oscillations νμ ντ Neutrino Oscillations Happens only if neutrinos have ”mass” (once no one believed there is mass. I.e. standard model had no mass.) Oscillate to other neutrino generations Oscillation probability is based on the ”energy” and ”distance” Accelerator neutrino is dominated by nm (except for a few %) nm – nt and nm – ne oscillations has been well studied during this 12 years, but not well studied nt – ne oscillation nt – ne oscillation could provide hints of asymmetry between matter and anti-matter in our universe.

J-PARC and T2K experiment T2K experiment (starts from April-2009) J-PARC accelerator and neutrino beam-line makes nm beam directed to super-Kamiokande which is apart from Tokai by 295km. Super-Kamiokande can study how to oscillate neutrinos, especially nm – ne oscillation. (nm – nt – ne oscillation gives the first and third generation oscillation probability) If there is large oscillation, it opens the way to search for matter dominant universe.

J-PARC Slow Extracted Beam Facility Materials and Life Science Experimental Facility Hadron Beam Facility Neutrino to Kamiokande Nuclear Transmutation Main Ring (30 GeV, 0.3 Hz, 0.75 MW→ 1.66 MW) Linac 180→400 MeV Rapid Cycling Synchrotron (3GeV, 25 Hz, 1MW) J-PARC = Japan Proton Accelerator Research Complex Joint Project between KEK and JAEA

Neutrino Oscillation Experimentalists determine; Disappearance measurement Flux w/o oscillation Experimentalists determine; Neutrino Energy En (GeV) , travel distance L(km) Measurement parameter; Oscillation amplitude q23, delta m squared Dm232 q Survival probability Dm232 Compare energy spectrum between w/ and w/o oscillation 0 1 2 Neutrino Energy En (GeV) Appearance of electron neutrinos provide unmeasured mixing angle q13 and hints for matter-antimatter asymmetry.

How to make neutrino beam　(Bend accelerated 30GeV protons and hit them to target. Pions are made around target are focused with magnetic horns) Building for neutrino monitor Magnetic horns (3horns) target p+p->X+π Stop all charged particles w/ absorber and soil. protons π-> μ＋ν UA1 magnet donated From CERN installed Bend protons from acc. to target Absorber for charged particles Target station 8 Pions decay volume

T2K Physics Run begins in 2010 (until June) ~100kW ~50kW  Beam Power Delivered POT: 3.35×1019 (3.28×1019 for physics) Continuous run @ ~50kW level Trial up to 100kW successful.

Off-axis detectors inside UA1 magnet T2K-ND280 detector system On-axis detector “INGRID” Off-axis detectors inside UA1 magnet We will visit here!! (this afternoon) some of you will see neutrino events here on 16-Feb.

Near detectors Near detectors are set inside Tokai in order to measure the neutrino properties (energy, rate,) before oscillation. For disappearance, nm rate and energy measurements are important. For appearance, ne rate and energy meas. are crucial. First on-axis detector (INGRID) event.

Near Detector Neutrino Measurements dE/dx by TPC (positive) Neutrino interaction proton electron MIP (m/p) ICHEP talk by Flor de Maria Blaszczyk Neutrino event rate ( INGRID) Neutrino event timing ( INGRID) June 26th Jan. 23rd ICHEP2010 -- T.Nakaya (Kyoto) --

40m diameter, 40m height 50kt water is contained. Super Kamiokande 50,000ton Water Cherenkov 40m diameter, 40m height 50kt water is contained. ~10000PMTs, 40% photo- coverage. Cherenkov Charged particle

Electron-like and muon-like events e-like m-like e m

First T2K event candidate in Super-Kamiokande First physics result (w/ 3.1x1019 POT) will come soon!! Continuous operation provided > 1x1020 POT (proton on target) recently. (achieved ~135kW)

Super-K(Far detector) neutrino events LE: Low energy triggered events OD: Outer detector events FC: Fully contained events FC OD LE FC Clean beam timing structure confirmed in FC events Twenty-two FC events observed by Mid. May in 2010 Non-beam BG estimated to be <10-3evts

Accelerator experiment Neutrinos can be measured more than once Relative change of rate and spectrum Effect of oscillation depend only on neutrino energy (fixed distance) Beam energy can be chosen Type of detector Neutrino energy determination method can be chosen

A next-generation experiment Build 100kt level liquid Argon detector . For example, one good site candidate is Okinoshima to build. It is apart from Tokai by 658km away. We need to (upgraded) intense neutrino beam as well. This kind of long base-line might provide good hints for neutrino CP violation term. (matter and anti-matter asymmetry term) Okinoshima From Tokai ~658km A.Bueno et al

u c d s t b νe νμ ντ e μ τ u c d s t b νe νμ ντ e μ τ Asymmetry between matter and antimatter ~ CP violation in lepton sector~ u c d s t b νe νμ ντ e μ τ matter Lepton; company of electrons Quark; company makes nucleons u c d s t b νe νμ ντ e μ τ Antimatter (anti-leptons) (anti-quarks) Particles (matter) and Anti-particles (anti-matter) Particles must have their anti-particles. (normally, they have opposite charges) If there are same physics between quarks and anti-quarks, there should same amount of the matter and anti-matter in our universe. (but anti-matter is quite small) 　If there is different property between neutrinos and anti-neutrinos, it could explain the matter dominant universe, which is made in earlier universe age. By the way, famous quark/anti-quark asymmetry (Kobayashi-Maskawa) cannot cover all.

ne  nm oscillation probability dcp provides diff between n and anti-n To see d 　meas. n and anti-n diff. or. 　meas. n energy spectrum Interference term plays important role!! A.Bueno et al NP08 (@Mito) on Mar-6-2008

nm  ne oscillation probability (on E/L) dCP=0 dCP=90 dCP=270 Oscillation probability Dm312 = 2.5x10-3 eV2 sin22q13 = 0.1 No matter effects 1st Oscillation Maximum E/L~1.27Dm2*2/p (E/L) 2nd Oscillation Maximum E/L~1.27Dm2*2/3p Oscillation Minimum E/L~1.27Dm2/p A.Bueno et al NP08 (@Mito) on Mar-6-2008

Why liquid Argon detector? Revival “bubble chamber” with latest technology Tracking detector: Measure precise event topology Can measure low momentum particles. Can measure local dE/dx PID with dE/dx and track length (range) Distinguish electron from pi-zero. (eff. 80-90%, while rejection factor is 1000) Full sampling, wide solid angle (4p), same material Good energy resolution 65 cm e- 50 cm p MC νe CC, Eν=0.730 GeV 240 cm p μ- 90 cm MC single π0, E=0.5 GeV MC νμ CC, Eν=1.73 GeV One of the best detectors which has good performance for neutrino phys.

Spectra for ne CC events 45 Shaded is beam ne background, while histogram shows the osc’d signal. dcp effects are seen in 1st and 2nd osc. Maxima. (perfect resolution case) 25 0 deg 90 deg 4 4 60 40 180 deg 270 deg A.Bueno et al 4 NP08 (@Mito) on Mar-6-2008 4

Allowed regions This is perfect energy spectrum case Cases at dcp=0,90,180,270 and sin22q13=0.1,0.05,0.03 are overlaid. Each point has 67,95,99.7% C.L contours Perfect resolution case A.Bueno et al NP08 (@Mito) on Mar-6-2008

Image of ~100kt LAr and important R&D components Liquid phase Single stage GEM Readout Gas phase Test for long drift distance of ionized electrons using cylindrical cryostat Double phase detector readout using both liquid and gas Argon phases (with GEM/LEM) Electronic racks Charge readout plane GasAr E ≈ 3 kV/cm Extraction grid E-field LAr 20m E≈ 1 kV/cm Field shaping electrodes 80m 　Very high purity of LAr is needed. (t(ms)=300/ppb, e.g: 1/e at ~5cm of 10ppb with 1kV/cm) Drift velocity is slower with lower voltage, and it affects more attenuation in LAr. 　To provide better S/N, GAr is used, too. Cathode (- HV) High Voltage up to ~MV

Concept of the LAr TPC Ionization selectron signal ~5x104e/cm MIP Liquid Ar 1 kV/cm Gas Argon 5kV/cm GEM readout Ionization selectron signal ~5x104e/cm MIP 3D track reconstruction as a TPC drift velocity is ~mm/μs with ~kV/cm electric field LAr purity affects the attenuation of the drift electrons. No amplification inside LAr Diffusion of the drift electrons is about 3mm after 20m drift Double phase Ionization electrons Scintillation light Cherenkov light Charged particle Electric Field nm charged current event ドリフト速度: P10 50 mm/micros 純Ar: 1-5 mm/micros ne charged current event A. Bueno, et.al.,, hep-ph/0701101

Strategy toward huge detector (Japan) 250L detector 100 cm 40 cm 　We prepare for several steps toward 100kt 10L (test of double phase readout) -> under testing 250L (test for charged particles’ (mainly K) response of LAr TPC at J-PARC) -> We achieved in 2010 fall 40-1000 ton detector -> under discussion 40~1000ton detector 　Until 250L, we achieved to operate the detector. 20 m 80 m 100ｋｔ detector

Purpose of 250L Test-beam with well-defined charged particles Test of the detector response. Using J-PARC K1.1BR beamline on October 2010 to understand the K+ response mainly (with proton decay momentum region). Test of double phase detector with the size of ~0.4m x 0.8m readout. to optimize the detector for neutrino/proton decay physics. (gain of LEM, ~10, is enough, i.e. easier than dark matter search.)

Slow Extraction Exp. Facility Materials and Life Experimental Facility J-PARC Accelerator and Experimental Facility 3 GeV Synchrotron Linac South to North MR (Main Ring Synchrotron) 30GeV 0.75MW Slow Extraction Exp. Facility Materials and Life Experimental Facility Neutrino Beams　(to Kamioka) 以上、加速器の現状を述べましたが、それでは，この施設を用いてどんな研究を展開するのかという話題に移りたいと思います。 この写真はさっきの写真とよく似ておりますが、実験室がよく見えるように、逆方向の南から北方向を眺めたものです。 本年度末には、物質生命科学実験施設とハドロン実験施設において実験が始まります。そして、来年度早々には、ニュートリノビームを神岡の方に送ることにしております。 実験室としては３つありますので、それぞれでどんな科学が展開されるのかをザッと眺めたいと思います。 Bird’s eye photo in January of 2008

Hadron Hall Brand-new K1.1BR beamline LAr 250L

Beam counter layout (PID) 0.8GeV/c K/p ratio (max.) ~ 1/4 a few K+/spill(=6s) (max.) beam profile (@degrader) s(x)~8cm, s(y)~6cm Degrader (Lead Glass) Beam Hodoscope MWPC2 MWPC1 TOF2 Gas Cherenkov TOF1 BDC Fitch Cherenkov K, p beam BDC = Beam defining counter

Event display (GEANT4) K+ from proton decay events has ~350MeV/c Range is ~15cm in LAr. -> we can measure properties well. Secondary particles from K+ was not fully contained, but can be used for the analysis. K -> μ + n TPC K+ -> e+ + n + p0 TPC K+ -> m + n (BR; 63.5%) K+ -> p+ + p0 (BR; 20.7%) K+ -> p0 + e+ + ne (BR: 5.1%)

PID performance using dE/dx info. Top: dE/dx in each pitch (K, p, m) as a function of the distance from the particle stopped point. Bottom; Likelihood distributions of K, p and m using probability density function of dE/dx in each pitch (top). Good separation, but tails have to be checked. Kaon Kaon Pion Pion Muon Muon Kaon Pion Muon Likelihood using dE/dX

Setup of Oct-2010 test-beam Fiducial mass 170kg Total LAr mass ~400kg Field cage dimension 42cm x 42cm x 78cm Fiducial volume 40cm x 40cm x 76cm Typical Drift Field ~225V / cm Maximum drift voltage 12kV (same feed-through as 10L) Readout method single phase (temporary) Number of readout channels 76 strips (1cm) drift PMT Double phase component is under production at CERN. (Unfortunately, not in time for test-beam.) 76 strips (1cm) anode

Charged particle test-beam @J-PARC (Oct/23-31) View from cathode side (see 1cm strip anode at far side)

The “text-book” event (=cm) pion positron proton ~40cm All are 0.8GeV/c PID by local dE/dx and range (even by eye) (=cm)

Event gallery ~600 MeV/c K+ (800+degrader) 200MeV/c pion 800MeV/c proton 800MeV/c positron Performance of PID is under analyzing

Summary T2K experiment, which aims to measure the final unknown oscillation amplitude (i.e. mixing angle) q13, starts from 2009-April. We are accumulating the candidate events at Super-Kamiokande. We will have good physics results soon. In next generation experiment, we’d like to quest the CP violation of lepton sector. (with huge liquid Argon TPC and intense beam)

Supplements

Three Flavor Mixing in Lepton Sector mass eigenstates Weak eigenstates m1 ne m2 nm nt m3 cij = cosqij, sij=sinqij q12, q23, q13 + d (+2 Majorana phase) Dm122, Dm232, Dm132