Superbeam long baseline experiments

Takashi KobayashiKEK

100830Neutrino Summer School@Tokai

2

3

2

1

MNSU

e

10000

0010

0

00

001U 1212

1212

1313

1313

2323

2323MNS cssc

ces

esc

cssc

i

i

e

Flavor eigenstates m1

m2

m3

Mass eigenstates

6 parametersq12, q23, q13, Dm12

2, Dm232, Dm13

2)sin(s ),cos(c ijijijij qq

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)?• ???

1

2

3

Mass hierarchy

e??

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

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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

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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∝ /MW)2

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

standard model

11

W

e,,VMNS

VMNSe

gExample: eg

Oscillation

12

l l’

1

2

3

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 D

222jiij mmm D 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

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Disappearance ? Appearance?

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i

liimtiE

lmiet

ili

tiE

iliil

tiEll

Ue

et

i

i

2

Oscillation probability

Disappearance case

There is no place for complex phase in UMNS 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

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Next talks

e vs appearance

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Oscillation probability (w/ CPV)

sin2 AAP

Relative effect of CPV

AAACPCCPV sinsin/ 2

CP conserved part

CPV part

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

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e

Z

e

X X

e

W

e-

e- e

Z

X X

Z

X XNC

Interactions through propagation in matter

CC

Matter effect

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e

tot

e

Hdtdi

00000000

1

3

2

1 W

MNSMNStot

VU

EE

EUH

Relative size of effect E∝ Change sign when Dm2 sign

change: Can probe sign Change sign when ⇔bar:

Fake CPV effect

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Oscillation probabilities

qq ELmP e /27.1sin2sinsin 213

213

223

2 D

qq ELmP x /27.1sin2sincos1 223

223

213

4 D

q ELmP xe /27.1sin2sin1 213

213

2 D

contribution from Dm12 is small

e appearance (LBL/Atm)

disappearance (LBL/Atm)

e disappearance (Reactor)

D

DDD

223

213

223

212

mL

Emmm

when

12

3

Dm232

(No CPV & matter eff. approx.)

~1

~0.5

≪1

Pure q13 and Dm132

q13 and Dm132

q23 and Dm232

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e appearance & CPV

, a-a for e

]GeV[]cmg[][eV1056.7 3

25 Ea Matter eff.:

CP-odd

qq sin

sin2sin

13

12212

D

ELm

PPPPACP

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

, a-a for e

]GeV[]cmg[][eV1056.7 3

25 Ea 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

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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.

e 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

ccsccssesscscescssseccsscecssesccc

ii

ii

ie

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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 physicsSo, now, let’s consider more on experimentation!

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Super Beam

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

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

device

ProtonBeam

Target FocusingDevices

Decay Pipe

Beam Dump

p,K

Strongly motivated by high precision LBL osc. exp.

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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)

E(GeV)

E(G

eV)

5

12

]mrad[30]GeV[max

q E

flux

/ flux for CPV meas.

-15%@peak

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

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ep0

Back ground for e appearance search• Intrinsic e component in initial beam

• Merged p0 ring from interactions

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 E reconstruction in Water Cherenkov

CC quasi elastic reaction

q

cospEm2mEm

EN

2N

+ n → + p

-

p

(E, p)q

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

sec

tions

(10

cm)

-38

2

In e la s t ic

C C q e

+ n → + p + p

-

p

(E, p)ql

p

2 approaches for CPV (and sign(Dm2) ) 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 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∝ Not rely on the standard scenario

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Angle and Baseline

OA3°

OA0°OA2°

OA2.5°

fl

ux• 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)

CP=90CP=270

CP=0

Dm312 = 2.5x10-3 eV2

sin22q13 = 0.1No matter effects

νμ νe oscillation probability

Osc

illat

ion

prob

abili

ty

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“Available” beams

36

37

FNAL possible future Plan

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CERN future possibilities

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Present accelerator complex Various POSSIBLE scenarios

Under discussion

CERN possibilities

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Okinoshima

658km0.8deg. Off-axis

KamiokaKorea

1000km1deg. Off-axis

295km2.5deg. Off-axis

Possible scenarios in Japan

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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

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295km2.5deg. Off-axis<E>~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

=0 =p/2

Er

ec

Er

ecEr

ec

Er

ec

+ BG+ee BG

signal+BG

sin22θ13=0.03,Normal Hierarchy

sin2 2q 1

3Fr

actio

n of

3s

3s

CP sensitivity

sin22θ13

deg.

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Site studies in Europe

44

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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!

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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!

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