Superbeam long baseline experiments Takashi Kobayashi KEK Neutrino Summer

2 e   Flavor eigenstates m1m1 m2m2 m3m3 Mass eigenstates 6 parameters  12,  23,  13,   m 12 2,  m 23 2,  m flavor mixing of neutrino Unitary matrix 2  m ij =m i 2 -m j 2

T.Kobayashi (KEK) 3 Known and Unknowns OR Solar & Reactor  12 ~33 o  m 12 2 ~ eV 2 Atomspheric + Acc  23 ~45 o  m 23 2 ~0.0025eV 2Unknown!  13 <10 o  13 <10 o (  m 13 2 ~  m 23 2 )? (  m 13 2 ~  m 23 2 )?  ???  ??? Mass hierarchy e ??

4 Unknown properties of neutrino 4   13 ?  Last unknown mixing angle   T2K, NOvA, Double Chooz, RENO, DayaBay  CP invariance ?  Mass hierarchy ?  Absolute mass  Tritium beta decay, double-beta  Majorana or Dirac?  Double-beta Next generation accelerator based expriemtns

Toward unraveling the mystery of matter dominated universe 5

Sakharov’s 3 conditions To generate Baryon asymmetry in the unverse  There is a fundamental process that violates Baryon number  C and CP invariance is violated at the same time  There is a deviation from thermal equilibrium acting on B violating process 6

Toward origin of matter dominated universe  Quark sector CPV is found to be not sufficient for reproducing present baryon content  Scenario for baryogenesis through lepton CP violation: Leptogenesis  CPV in lepton sector is responsible for B genesis  CPV in neutrino oscillation could provide a key to unravel mystery of origin of matter 7

Let’s find CPV in lepton sector  I give you  1000 億円 or  1.2 Billion USD  755M GBP  55 Billion INR  1,401 Billion Won  2,130 Billion Peso  7.9 Billion 元  918 Million Euro  35 Billion Ruble  1.2 Billion CHF 8 Let’s design an experiment to search for CPV in lepton sector If you find any good idea, let’s write a paper! One condition: Within 10years

How? …. : Q1  Do we really need oscillation phenomena to probe CPV??  Can’t we attack CPV in an experiment which fit in an experimental hall like such as Kaon CPV or B CPV  Why?? 9

Measuring CPV in quark sector  Through loop diagram  Amplitude ∝ (m u,c,t /M W ) 2  Please calculate  Since quark is heavy (especially top), this process becomes measureable 10 W W s,b d u,c,t s,b W u,c,t V CKM

How about lepton sector?  Amplitude ∝ (m /M W ) 2  Standard model process STRONGLY suppressed  Thus, good field to search for physics beyond standard model 11  W e, ,  V MNS e  Example:   e 

Oscillation 12 l l ’ 1 2 3

Oscillation (cont) 13 If E i are same for all mass eigenstates E Ei’s are same, no oscillation, in other word, Ei’s are different, we can probe mixing matrix through oscillation Difference of Ei, ie, phase advance difference is essential For  m 2 ~10 -3 eV 2

14 B.Kyser, in this SS

Q2: What oscillation process is best?  OK, now, we somehow understand we need (long baseline) oscillation phenomena to probe matrix elements and attack CPV.  What type of oscillation is best?  Fundamental physics reason  Experimental feasibility 15

Disappearance ? Appearance? 16 Oscillation probability Disappearance case There is no place for complex phase  in U MNS to appear Disappearance has no sensitivity on (standard) CPV

Appearance  Conventional  beam (~GeV)    e  Not yet discovered      Dominant oscillation mode  Neutrino factory/Beta beam (~10GeV)  e    e   17 Next talks

e vs  appearance 18 Oscillation probability (w/ CPV) Relative effect of CPV CP conserved part CPV part     case,  probability A ∝ sin 2 2  23, is known to be large, relative effect of CPV becomes small  Also experimentally, identification of nt (out of lots of nm interactions ) is not easy  For nue appearance, A ∝ sin 2 2  13 is known to be small   Large CPV effect expected

Matter effect 19 e Z e X X e W e- e  Z  X X  Z  X X NC Interactions through propagation in matter CC

Matter effect 20  Relative size of effect ∝ E  Change sign when  m 2 sign change: Can probe sign  Change sign when ⇔ bar: Fake CPV effect

21 Oscillation probabilities contribution from  m 12 is small e appearance (LBL/Atm)  disappearance (LBL/Atm) e disappearance (Reactor) when  m 23 2 (No CPV & matter eff. approx.) ~1 ~0.5 ≪1≪1 Pure  13 and  m 13 2  13 and  m 13 2  23 and  m 23 2

22   e appearance & CPV   , a  -a for Matter eff.: CP-odd Solar Main Matter # of signal ∝ sin 2  13 (Stat err ∝ sin  13 ), CP-odd term ∝ sin  13 Sensitivity indep. from  13 (if no BG & no syst. err)

23 Takashi Kobayashi (KEK), PAC07 23 All mixing angle need to be non-zero   , a  -a for Matter eff.: CP-odd Leading CPV effect (where sin  12 ~0.5, sin  23 ~0.7, sin   <0.2) + other terms.. Same as Kobayashi-Maskawa model which require 3x3 to incorporate CPV

24 CPV vs matter effect 295km730km Smaller distance/lower energy  small matter effect Pure CPV & Less sensitivity on sign of  m 2 Combination of diff. E&L help to solve.   e osc. probability w/ 2 2  13 =0.01

Lepton Sector CP Violation Effect of CP Phase δ appear as – ν e Appearance Energy Spectrum Shape *Peak position and height for 1 st, 2 nd maximum and minimum *Sensitive to all the non-vanishing δ including 180° *Could investigate CP phase with ν run only – Difference between ν e and ν e Behavior 25

How to do experiment? OK, we now understand  Importance of CPV in lepton sector  Necessity of oscillation to probe CPV  What process is suited for CPV measurement  Behavior of oscillation probabilities and relevant physics So, now, let’s consider more on experimentation! 26

Super Beam Conventional neutrino beam with (Multi-)MW proton beam (  Fact)  Pure  beam ( ≳ 99%)  e ( ≲ 1%) from     e chain and K decay(Ke3)     can be switched by flipping polarity of focusing device 27 Proton Beam Target Focusing Devices Decay Pipe Beam Dump  ,K,K  Strongly motivated by high precision LBL osc. exp.

28 High intensity narrow band beam -- Off-axis (OA) beam -- (ref.: BNL-E889 Proposal)  Target Horns Decay Pipe Far Det. Decay Kinematics  Increase osc. max.  Decrease background from HE tail 1/~1/~ E  (GeV) E (GeV)  flux

   flux for CPV meas.   POT/yr Sign flip by just changing horn plarity Example 50GeV proton At 295km

Cross sections  Cross section ∝ E  Higher energy  higher statistics  Anti-neutrino cross section smaller than neutrino by ~1/3  Why?  Take ~3 times more time for anti-neutrino measurements to acquire same statistics as neutrino

31  e 00 Back ground for e appearance search Intrinsic e component in initial beam Merged  0 ring from  interactions e appearance search e appearance search

“Available” technologies for huge detector Liq Ar TPC  Aim O(100kton)  Electronic “bubble chamber”  Can track every charged particle  Down to very low energy  Neutrino energy reconstruction by eg. total energy  No need to assume process type  Capable upto high energy  Good PID w/ dE/dx, pi0 rejection  Realized O(1kton) Water Cherenkov  Aim O(1000kton)  Energy reconstruction assuming Ccqe  Effective < 1GeV  Good PID (  /e) at low energy  Cherenkov threshold  Realized 50kton 32 Good at Wideband beam Good at low E (<1GeV) narrow band beam

Neutrino Energy  reconstruction in Water Cherenkov CC quasi elastic reaction  + n →  + p -- p (E , p  )  QE inelastic  + n →  + p +  -- p (E , p  )   

2 approaches for CPV (and sign(  m 2 ) )  Energy spectrum measurement of appeared e  Only w/ numu beam (at least early part)  Measure term ∝ cos  (and sin  )  Assume standard source of CPV (  in MNS)  Cover 2 nd oscillation maximum (higher sensitivity on CPV)  Higher energy = longer baseline favorable  Wideband beam suited  Liq Ar TPC is better suited  Difference between P(numu  nue) and P(numubar  nuebar)  Measure term ∝ sin   Not rely on the standard scenario 34

Angle and Baseline OA3° OA0° OA2° OA2.5°  flux Off-axis angle – On-Axis: Wide Energy Coverage, ○ Energy Spectrum Measurement ×Control of π 0 Background – Off-Axis: Narrow Energy Coverage, ○ Control of π 0 Background ×Energy Spectrum Measurement → Counting Experiment Baseline – Long: ○ 2 nd Osc. Max. at Measurable Energy × Less Statistics ? Large Matter Effect – Short: ○ High Statistics × 2 nd Osc.Max.Too Low Energy to Measure ? Less Matter Effect (E/L)  CP =90  CP =270  CP =0  m 31 2 = 2.5x10 -3 eV 2 sin 2 2  13 = 0.1 No matter effects ν μ  ν e oscillation probability Oscillation probability 35

“Available” beams 36

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FNAL possible future Plan 38

CERN future possibilities 39 Present accelerator complex Various POSSIBLE scenarios  Under discussion

CERN possibilities 40

Okinoshima 658km 0.8deg. Off-axis Kamioka Korea 1000km 1deg. Off-axis 295km 2.5deg. Off-axis Possible scenarios in Japan 41

Okinoshima 658km 0.8deg. Off-axis Cover 1 st and 2 nd Maximum Neutrino Run Only 5Years×1.66MW 100kt Liq. Ar TPC -Good Energy Resolution -Good e/π ０ discrimination Keeping Reasonable Statistics Scenario 1 δ=0° ν e Spectrum Beam ν e Background CP Measurement Potential NP08, arXiv: δ=90° δ=180°δ=270° sin 2 2θ 13 =0.03,Normal Hierarchy  42

295km 2.5deg. Off-axis ~0.6GeV Tokai Kamioka Cover 1 st Maximum Only 2.2Years Neutrino+7.8Years anti-Neutrino Run 1.66MW 540kt Water Cherenkov Detector Scenario 2    =0  =  /2 E r ec  +  BG  +  e  e BG signal+BG sin 2 2θ 13 =0.03,Normal Hierarchy sin 2 2  13 Fraction of   CP sensitivity sin 2 2θ 13 deg. 43

Site studies in Europe 44

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US Superbeam Strategy: Young-Kee Kim, Oct. 1-3, 2009 NSF’s proposed Underground Lab. DUSEL 1300 km Project X: ~2 MW 700kW 15kt Liquid Scintillator Under construction NOvA ~50 kton Liquid Ar TPC ~300 kton Water Cerenkov MiniBooNE SciBooNE MINOS NOvA MINERvA MicroBooNE 735 km 2.5 msec 810 km Combination of WC and LAr FNAL possibilities

FNAL-DUSEL potential

To realize the experiments Need  Finite (reasonable)  13  T2K, NOvA, Reactors!  High power (>MW) neutrino beam  Huge high-sensitivity detector   YOUR CHALLENGE  OR YOUR NEW IDEA! 48

Summary  Properties of neutrino are gradually being revealed  However still yet far unknown than quarks  CPV, mass hierarchy, etc.  Especially, CP symmetry could be a critical key to answer the fundamental question: What is the origin of matter in the universe  Future superbeam long baseline oscillation experiments have chance to discover CPV effect (if  13 is large enough to be detected in present on-going experiments)  Already many studies and developments (beam, detectors) are being made around the world to realize the experiments  Lot’s of challenges and funs forseen  Let’s enjoy! 49