Future Accelerator Based Neutrino Experiments

Takashi KobayashiInstitute of Particle and Nuclear Studies,

High Energy Accelerator Research Organization (KEK)

Aug.22,2011Lomonosov ConfMoscow

Standard picture of 3 flavor mixing

3

2

1

PMNSU

e

100

0

0

0

010

0

0

0

001

U 1212

1212

1313

1313

2323

2323MNS cs

sc

ces

esc

cs

sci

i

)sin(s ),cos(c ijijijij

2

ne

nm

nt

Flavor eigenstates m1

m2

m3

Mass eigenstates

6 independent parameters govern oscillationq12, q23, q13, dDm12

2, Dm232, Dm13

2

Atm/Acc Acc/Reactor Sol/Reactor

2

Dmij=mi2-mj

2

Pontecorvo-Maki-Nakagawa-Sakata Matrix (CKM matrix in lepton sector)

Present knowledge (before June, 2011)

3

OR

n1

n2

n3

Which??

ne??

Big diff from KM matrix

d unkown

Sol/Reactor

Atm/Acc

Indications of large q13

4

T2K6event obs.1.5 BG exp’ed2.5s(June 13,2011)

MINOS62event obs.49.5 BG exp’ed1.7s(June 24,2011)

New results on nm disappearance T2K released the first

disappearance result Consistent with MINOS &

SK results MINOS data indicates slight

tension between nm and anti-nm

5

What’s next? Immediate issues with on-going experiments

EXPERIMENTALLY establish non-zero q13 as soon as possible

Precise measurement of q23, Dm23 (both for nm and anti-nm), whether maximal mixing or not?

Next most important goal: CPV CP is violated/conserved in neutrino? What is the mechanism of violation? PMNS-type

“standard” scenario or anything exotic origin?

6

Toward one of big goals of particle physics: Origin of Matter-dominated Unvierse

Sakhalov’s 3 conditions

Baryon number violationProton decay

CP violationQuark CPV seems not sufficientLepton CPV may contribute

Non-equilibulium7

88

nmne appearance and CPV

132312sin sss CPV effect

(sinq12~0.5, sinq23~0.7, sinq13<0.2)

Unknown!

CPVSol term

The size of q13 decide future dir.!

ne appearance is golden mode for CPV IF ne appearance exist No CPV effect in disappearance Only nm beam is presently technically available Small leading CPC term Large CPV effect (⇔nt app.)

Expected CPV (&matter) effects (w/ “standard” PMNS framework)

~20% CPV effect at sin22q13=0.1 w/ sindCP=1 (max. vio.) at 1st peak To detect CPV >3s for sind>0.2 (Asym=4%) O(10k) events necessary Much higher statistics is necessary >MW proton & huge detector mandatory

CPV asymmetry get smaller for larger q13

Severer requirement on systematic error Matter effect becomes comparable (@295km) or dominant (2300km) at 1st peak ( potential to

determine mass hierarchy ) CPV asymmetry get much larger for 2nd peak

Matter effect become small correction9

T2K 90% region

T2K 90% region

T2K 90% region

1st peak @ 2300km (4.65GeV)1st peak @ 295km (0.6GeV) 2nd peak @ 2300km (1.6GeV)

Pure CPV effect

Pure matter effect

Essential requirements for CPV discovery

Order of magnitude higher statistics from present generation experiments

High intensity beam (Multi-MW)

Increase statistics High sensitivity huge detector

Increase statistics Increase signal efficiency Reduce background Reduce systematic errors Should also capable for proton decay detection

10

11

How to measure CPV & sign(Dm23)

νe appearance energy spectrum shape Peak position and height for 1st, 2nd maximum and minimum Measure both sind & cosd terms can discriminate 0deg vs 180deg

Difference between νe and νe behavior Sensitive to any mechanism to make asymmetry (No assumption) Basically measure sin d term

Distance: Larger L Matter effect large Sensitive to sign(Dm23) too Smaller L (lower E): Purer CPV measurement 11

665km 2300km

CPVMatter

Future MW proton facilities in the world

12

Staged approach

“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 (m/e) at low energy Cherenkov threshold Realized 50kton

13

Good at Wideband beam

Good at low E (<1GeV) narrow band beam

Possible experimental configuration Multi-MW beam + Longer distance O(1000km)+ Wide

band beam + LiqAr Energy spectrum measurement Cover both 1st and 2nd peaks Possible to determine “everything” in 1 shot

CPV Hierarchy q23 octant

Multi-MW beam + Shorter distance (a few 100km) + Low energy narrow band beam + Water Cherenkov Nue/nuebar asymtery of 1st peak Possible to determine

CPV Need external input to discriminate mass hierarchy (such as atm

nu)14

Planned future CPV experiments

Experimental configuration

Liq. Ar TPC WC Comment

• MW beam• O(1000km)

baseline• WBB• Spectrum

measurement

• J-PARC-Okinoshima (100kt@658km)

• CERN-Pyhasalmi (LAGUNA, 100kt@2300km)

• US-LBNE/LAr (34kt@1300km)

• US-LBNE/WC (200kt@1300km)

• Sensitive to matter effect = mass hierarchy

• Could possibly detect deviation from “standard” PMNS spectrum shape

• MW beam• a few 100km

baseline• Sub-GeV NBB• n/anti-n

asymmetry

• J-PARC-HyperK (540kt@295km)

• CERN-Frejus (LAGUNA, 440kt@130km)

• Less dependence on assumption

• Need other input for mass hierarchy

15

P32 proposal (Lar TPC R&D)Recommended by J-PARC PAC(Jan 2010), arXiv:0804.2111

Kamioka L=295km OA=2.5deg

Okinoshima L=658km OA=0.78deg Almost On-Axis

Scenarios in Japan

J-PARC

1.7MW??MW

J-PARC-HyperK @ Kamioka

3s

sin2q23=0.6 sin2q23=0.5 sin2q23=0.4

mass hierarchy

determination w/

atmospheric n

leptonic CPV w/ JPARC n

10 yrs exposure of atm. n data.Super-K syst. errors are assumed.5 yrs of 1.66 MW JPARC n data.

5% syst. errors are assumed.

• Very good chance to detect CPV & have potential on sign(Dm23) with atm n

Hyper-K Base-Design• 1Mton total volume, twin cavity• 0.54Mton fiducial volume• Inner (D43m x L250m) x 2• Outer Detector >2m• Photo coverage 20% (1/2 x SK)

20” PMT w/ cover

FEM analysis(Factor of safety)

• Base-design to be optimized

• Geological survey of the site is going on

• Qualitative studies on physics potential

J-PARC to Okinoshima

P32 proposal (Lar TPC R&D)Recommended by J-PARC PAC(Jan 2010), arXiv:0804.2111

Scenario 1

19

J-PARC to Okinoshima

P32 proposal (Lar TPC R&D)Recommended by J-PARC PAC(Jan 2010), arXiv:0804.2111

Scenario 1

20

Physics potential

Beam νe

Background

21

• Very good chance both to detect CPV & determine sign(Dm23)

CPV Hierarchy

European Activities: LAGUNA-LBNO

~500kt Water Cherenkov

100kt Liq Ar. TPC

GLACIER

LAGUNA-Pyhasalmi sensitivity

23

CPV

Mass hierarchy unknown assumption

A.Rubbia EPS-HEP 2011

R&D toward realizing 100kt LArTPC

24Site visit

Double phase readout test @ ETHZ (CERN RE18)

J-PARC T32 exp(ETHZ/KEK/Iwate/Waseda)

250L LAr TPC

180k trig (80k Kaon)

LBNE in US

25B.Svoboda, GLA2011

US-LBNE sensitivities

26

T2K regionT2K region

T2K region T2K region

L.Whitehead, B.Rebel @ NNN2010

Implication of large q13 on Future If sin22q13> ~0.01

Conventional Multi-MW super beam long baseline experiment will be really promising to explore CPV in lepton sector

We need to put even more effort to formulate the future project in this direction as soon as possible

IF not Need “ideal” beam such as Neutrino Factory or beta beam to probe CPV

27

T2K region

Summary Indication of large q13 makes conventional beam long baseline experiment be

promising to probe CPV and sign(Dm232)

To realize the next generation experiment, Multi-MW beam power & High sensitivity huge detector MUST BE REALIZED

Two detector options are under consideration: O(500kt) Water Cherenkov & 100kton LiqAr TPC

Two promising experimental configurations WBB w/ LiqAr TPC Spectrum measurement for 1st & 2nd peak NBB w/ WC n/anti-n asymmetry

Design study & R&D for future CPV search are intensively being done around the world J-PARC Kamioka (WC)/Okinoshima(LAr) CERN Frejus(WC)/Pihasalmi(LAr) (LAGUNA-LBNO) FNAL DUSEL (WC/LAr) (LBNE)

It is desirable to realize both configurations in the world, but it may not be so easy Need to be very careful on physics potential

Personally, I am interested in how to know origin of CPV, whether PMNS or something exotic International cooperation & coordination needed

EU/Russia/Japan(KEK) are working coherently under LAGUNA consortium

Need to be ready to “go” when finite q13 is concluded28