Superbeam long baseline experiments

Takashi KobayashiKEK

100830Neutrino Summer School@Tokai

2

3

2

1

MNSU

e

100

0

0

0

010

0

0

0

001

U 1212

1212

1313

1313

2323

2323MNS cs

sc

ces

esc

cs

sci

i

ne

nm

nt

Flavor eigenstates m1

m2

m3

Mass eigenstates

6 parametersq12, q23, q13, dDm12

2, Dm232, Dm13

2

)sin(s ),cos(c ijijijij

3 flavor mixing of neutrino

Unitary matrix

2

Dmij=mi2-mj

2

T.Kobayashi (KEK) 3

Known and Unknowns

OR

Solar & Reactor• q12~33o

• Dm122~0.00008eV2

Atomspheric + Acc• q23~45o 　 • Dm23

2~0.0025eV2

Unknown!• q13<10o

• (Dm132~Dm23

2)?• d ???

n1

n2

n3

Mass hierarchy

ne??

4

Unknown properties of neutrino

4

q13? 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/MW)2

Please calculate Since quark is heavy (especially top), this

process becomes measureable10

W W

s,b

d

u,c,t

u,c,ts,b

W

u,c,t

VCKM VCKM

VCKMVCKM VCKMVCKM

How about lepton sector?

Amplitude (m∝ n/MW)2

Standard model process STRONGLY suppressed Thus, good field to search for physics beyond

standard model

11

m

W

ne,nm,nt

VMNSVMNS

e

gExample: meg

Oscillation

12

nl nl’

n1

n2

n3

i

liitiE

liet

i

liimtiE

lmiet

MNSliU

Oscillation (cont)

13

i

liimtiE

lmiet

If Ei are same for all mass eigenstates E

mliEt

lmiEt

iliim

iEtlm

ee

et

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

jiljmjlimi

tEEilmml UUUUetP ji

,

**2

)100()1(~ 2/)( 2

kmOLOee ELmitEEi ijji

222jiij mmm For Dm2~10-3eV2

14B.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

i

liimtiE

lmiet

ili

tiE

iliil

tiEll

Ue

et

i

i

2

Oscillation probability

Disappearance case

There is no place for complex phase d in UMNS to appear

Disappearance has no sensitivity on (standard) CPV

Appearance

Conventional nm beam (~GeV) nm ne

Not yet discovered nm nt

Dominant oscillation mode

Neutrino factory/Beta beam (~10GeV) ne nm ne nt

17

Next talks

ne vs nt appearance

18

Oscillation probability (w/ CPV)

sin2 AAP

Relative effect of CPV

AAACPCCPV sinsin/ 2

CP conserved part

CPV part

nm nt case, probability A sin∝ 22q23, 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∝ 22q13 is known to be small

Large CPV effect expected

Matter effect

19

ne

Z

ne

X X

ne

W

e-

e- ne

nm

Z

nm

X X

nt

Z

nt

X XNC

Interactions through propagation in matter

CC

Matter effect

20

e

tot

e

Hdt

di

000

000

001

3

2

1 W

MNSMNStot

V

U

E

E

E

UH

Relative size of effect E∝ Change sign when Dm2 sign

change: Can probe sign Change sign when n

⇔nbar: Fake CPV effect

21

Oscillation probabilities

ELmP e /27.1sin2sinsin 213

213

223

2

ELmP x /27.1sin2sincos1 223

223

213

4

ELmP xe /27.1sin2sin1 213

213

2

contribution from Dm12 is small

ne appearance (LBL/Atm)

nm disappearance (LBL/Atm)

ne disappearance (Reactor)

223

213

223

212

mL

E

mmm

when

12

3

Dm232

(No CPV & matter eff. approx.)

~1

~0.5

≪1

Pure q13 and Dm132

q13 and Dm132

q23 and Dm232

22

nmne appearance & CPV

d-d, a-a for e

]GeV[]cmg[][eV1056.7

325 E

a

Matter eff.:

CP-odd

sinsin

2sin

13

12212

E

Lm

PP

PPACP

Solar

Main

Matter

# of signal sin∝ 2q13 (Stat err sin∝ q13),CP-odd term sin∝ q13

Sensitivity indep. from q13

(if no BG & no syst. err)

23Takashi Kobayashi (KEK), PAC07

23

All mixing angle need to be non-zero

d-d, a-a for e

]GeV[]cmg[][eV1056.7

325 E

a

Matter eff.:

CP-odd

Leading

132312sin sss CPV effect

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

+ other terms..

Same as Kobayashi-Maskawa model which require 3x3 to incorporate CPV

24

CPV vs matter effect

295km 730km

)( ePP )( ePP

Smaller distance/lower energy small matter effectPure CPV & Less sensitivity on sign of Dm2

Combination of diff. E&L help to solve.

nmne osc. probability w/ CPV/matter

@sin22q13=0.01

Lepton Sector CP Violation

Effect of CP Phase δ appear as– νe Appearance Energy Spectrum Shape

*Peak position and height for 1st, 2nd maximum and minimum

*Sensitive to all the non-vanishing δ including 180°

*Could investigate CP phase with ν run only

– Difference between νe and νe Behavior

3

2

1

231323122313122312231312

231323131223122313122312

1312131312

ccsccssesscsce

scssseccsscecs

sesccc

ii

ii

ie

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

27

Super Beam

Conventional neutrino beam with (Multi-)MW proton beam (nFact)

Pure nm beam ( 99%)≳ ne ( 1%) from ≲ pme chain and K decay(Ke3) nm/nm can be switched by flipping polarity of focusing

device

ProtonBeam

Target FocusingDevices

Decay Pipe

Beam Dump

nmp,K

m

Strongly motivated by high precision LBL n osc. exp.

28

High intensity narrow band beam-- Off-axis (OA) beam --

(ref.: BNL-E889 Proposal)

qTargetHornsDecay Pipe

Far Det.

Decay Kinematics

Increase statistics @ osc. max.Decrease background from HE tail

1/gp~q Ep(GeV)

En(GeV)

En(G

eV)

5

12

]mrad[

30]GeV[max

E

nm flux

nm/nm flux for CPV meas.

-15%@peak

nm

nm

1021POT/yr

Sign flip byjust changinghorn plarity

Example

50GeV protonAt 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

m ep0

Back ground for ne appearance search• Intrinsic ne component in initial beam• Merged p0 ring from nm interactions

ne 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 (m/e) at low energy

Cherenkov threshold Realized 50kton

32

Good at Wideband beam

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

Neutrino Energy En reconstruction in Water Cherenkov

CC quasi elastic reaction

cospEm

2mEmE

N

2N

nm + n → m + p

n

m-

p

(Em, pm)qm

QE

inelastic

0

0 .5

1

1 .5

2

2 .5

3

3 .5

4

4 .5

0 1 2 3 4 5E (G e V )

c

ross

se

ctio

ns

(10

cm

)-3

82

In e la s t ic

C C q e

nm + n → m + p + p

n

m-

p

(Em, pm)ql

p

2 approaches for CPV (and sign(Dm2) )

Energy spectrum measurement of appeared ne Only w/ numu beam (at least early part) Measure term cos∝ d (and sind)

Assume standard source of CPV (d in MNS) Cover 2nd oscillation maximum (higher sensitivity on

CPV) Higher energy = longer baseline favorable

Wideband beam suited Liq Ar TPC is better suited

Difference between P(numunue) and P(numubar nuebar) Measure term sin∝ d Not rely on the standard scenario

34

Angle and Baseline

OA3°

OA0°OA2°

OA2.5°

nm

flu

x

• Off-axis angle– On-Axis: Wide Energy Coverage,

○Energy Spectrum Measurement

×Control of π0 Background– Off-Axis: Narrow Energy Coverage,

○Control of π0 Background

×Energy Spectrum Measurement

　　　　　　　　　→ Counting Experiment• Baseline

– Long:

○ 2nd Osc. Max. at Measurable Energy

× Less Statistics

? Large Matter Effect– Short:

○ High Statistics

× 2nd Osc.Max.Too Low Energy to Measure

? Less Matter Effect (E/L)

dCP=90dCP=270

dCP=0

Dm312 = 2.5x10-3 eV2

sin22q13 = 0.1No matter effects

νμ νe oscillation probability

Osc

illa

tion

pro

babi

lity

35

“Available” beams

36

37

FNAL possible future Plan

38

CERN future possibilities

39

Present accelerator complex Various POSSIBLE scenarios

Under discussion

CERN possibilities

40

Okinoshima

658km0.8deg. Off-axis

KamiokaKorea

1000km1deg. Off-axis

295km2.5deg. Off-axis

Possible scenarios in Japan

41

Okinoshima

658km0.8deg. Off-axis

•Cover 1st and 2nd 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°

νeSpectrum

Beam νe

Background

CP Measurement Potential

NP08, arXiv:0804.2111

δ=90°

δ=180° δ=270°

sin22θ13=0.03,Normal Hierarchy

3s

42

295km2.5deg. Off-axis<En>~0.6GeV

TokaiKamioka

•Cover 1st Maximum Only•2.2Years Neutrino+7.8Years anti-Neutrino Run 1.66MW•540kt Water Cherenkov Detector

Scenario 2

K.Kaneyuki @NP08

nm

nm

d=0 d=p/2

Enr

ec

Enr

ec

Enr

ec

Enr

ec

nm+nm BG

nm+ +nm ne+ne BG

signal+BG

sin22θ13=0.03,Normal Hierarchy

sin

22q

13

Fract

ion o

f d

3s

3s

CP sensitivity

sin22θ13

deg.

43

Site studies in Europe

44

45

US Superbeam Strategy: Young-Kee Kim, Oct. 1-3, 2009

NSF’s proposedUnderground Lab.

DUSEL

1300 km

Project X: ~2 MW

700kW15kt Liquid Scintillator

Under construction

NOvA

~50 kton Liquid Ar TPC~300 kton

Water Cerenkov

MiniBooNESciBooNE

MINOSNOvA

MINERvAMicroBooNE

735 km2.5 msec810 km

Combination of WC and LAr

FNAL possibilities

FNAL-DUSEL potential

To realize the experiments

Need Finite (reasonable) q13 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 q13 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