A.Bueno, M.Campanelli, A.Rubbia ETH Zurichneutrino.ethz.ch/Talks_pdfs/Monterey_nufact.pdf · Antonio Bueno & Mario Campanelli & Andr” Rubbia, ETH/Zurich May 2000 Neutrino Oscillations

Antonio Bueno & Mario Campanelli & Andr� Rubbia, ETH/Zurich May 2000

A.Bueno, M.Campanelli, A.Rubbia ETH Zurich

hep-ph/0005007


Neutrino Oscillations at the NuFactory

µ− →e− νe νµ

νe→e− appearance

νµ→µ− disappearance

ντ→τ− appearance

νe→e+ appearance

νµ→µ+ disappearance

ντ→τ+ appearance

Plus their charge conjugates with µ+ beamP

P

P

P

P

e e

e

e

( ) sin

( ) sin sin

( ) sin cos

( ) cos sin ( cos sin )

( ) cos sin

ν ν θ

ν ν θ θ

ν ν θ θ

ν ν θ θ θ θ

ν ν θ θ

µ

τ

µ µ

µ τ

→ = −

→ =

→ =

→ = − −

→ =

1 2

2

2

1 4 1

2

213 32

2

213

223

232

213

223

232

213

223

213

223

232

413

223

∆

∆

∆

∆

∆2232

213

223

213

223

223

322 2

322

1 4 1

1 27

P

m L E

( ) cos cos ( cos cos )

sin ( . / )

ν ν θ θ θ θτ τ→ = − −

=

∆

∆ ∆

In a Neutrino Factory wecan study in principle 12independent processes:

Oscillation probabilities:


How to get most of the potential?

Experimentally, it is not possible to disentangleexactly all 12 oscillation processes.

However, we believe that once such apowerful machine is built, one should try toextract most of the information, with adetector as versatile as possible


LAr TPC at the Neutrino Factory

O

O

→

ICANOE is one of the two large detectorsproposed for the CERN-Gran Sasso beam.

O

O

Good technology for a Neutrino Factory→


Event classes in ICANOE-like detector

Detector able to identify

Event classes in ICANOE-like detector

, e, γ and hadrons,µ

Events can be classified into four classes, accordingto the leading particle:

O

O

O

O


With the high fluxes foreseen at the NeutrinoFactory we can think of very long baselines:

Possible baselines

Ringlocation

Distanceto GS

Meandensity


Event rates for a 10 kton detector

Eµ=30 GeV

No polarization

No beam divergence

No oscillations


Detector simulation

.

σ σ σ µ

µ

( ) %( )

( ) %( )

( )%. .E

E E GeV

E

E E GeV

P

Pe m had= = =3 20

20

σ θθ( )

/ ( )=130mrad p GeV

Charged π±,K± decay into µ± for BG treatment

Proper neutrino cross section used


Background treatment

10-7

10-6

10-5

10-4

10-3

0 2 4 6 8 10 12Pµ (GeV)

Fra

ctio

nal

Bac

kgro

un

d

10-7

10-6

10-5

10-4

10-3

0 2 4 6 8 10 12Pµ (GeV)

Fra

ctio

nal

Bac

kgro

un

d

10-7

10-6

10-5

10-4

0 2 4 6 8 10 12Pµ (GeV)

Fra

ctio

nal

Bac

kgro

un

d

10-7

10-6

10-5

10-4

10-3

0 2 4 6 8 10 12Pµ (GeV)

Fra

ctio

nal

Bac

kgro

un

d

We are not aimingat large backgroundrejection factors.

Simple momentumcut Pµ>2 GeVapplied


For this study, we consider as our default:

Parameters used

O decays of ( ++µ -)µO mixing with:Ü ∆m2

23=(3.5, 5, 7) * 10-3 eV2

Üsin2θ23=0.5

Üsin22θ13=0.05

O ICANOE-like detector


Observed Spectra

µ+ µ-

L=7400 km, 1021 µ- decays

0

200

400

600

800

1000

1200

1400

0 10 20 30 40Evis (GeV)

0

500

1000

1500

2000

2500

0 10 20 30 40Evis (GeV)

0

5

10

15

20

25

30

0 10 20 30 40Evis (GeV)

0

200

400

600

800

1000

0 10 20 30 40Evis (GeV)

L=7400 km, 1021 µ+ decays

0250500750

100012501500175020002250

0 10 20 30 40Evis (GeV)

0

200

400

600

800

1000

0 10 20 30 40Evis (GeV)

0

50

100

150

200

250

300

350

400

450

0 10 20 30 40Evis (GeV)

0

200

400

600

800

1000

0 10 20 30 40Evis (GeV)

No oscillation

∆m2=3.5 10-3 eV2

∆m2=7 10-3 eV2

θ23=π/4

sin2θ13=0.05ICANOE fast simulation


A closer look to different event classes

Eµ = 30 GeV, L = 7400 km, 10 20 µ- decays

0

20

40

60

80

100

120

0 5 10 15 20 25 30 35 40Evisible (GeV)

dN/d

E ν (νe C

C ev

ents

/1.6

GeV

per

10

kton

)

Anti-νe+νe+ντ CCAnti-νe CCνe CCντ CC


0

10

20

30

40

50

60

0 5 10 15 20 25 30 35 40Evisible (GeV)

dN/d

E ν (νµ C

C ev

ents

/1.6

GeV

per

10

kton

)

νµ + ντ CC + backgroundνµ CCντ CCBackground


0

20

40

60

80

100

0 5 10 15 20 25 30 35 40Evisible (GeV)

dN/d

E ν (ν ev

ents

/1.6G

eV p

er 10

kton

)

ν NC + ντ CCν NCντ CC

Eµ = 30 GeV, L = 7400 km, 10 21 µ+ decays

0

20

40

60

80

100

120

140

160

180

0 5 10 15 20 25 30 35 40Evisible (GeV)

dN/d

E ν (νµ C

C ev

ents

/1.6G

eV p

er 10

kton

)

νµ + ντ CC + background

νµ CC

ντ CC

Background


ντ appearance

ντ

A similar detector at the Neutrino factory would benefit from thebetter signal/BG ratio given by the longest baselines:

1 event

background


τ-enhanced sample

0

10

20

30

40

50

60

0 10 20 30 400

5

10

15

20

25

30

35

40

0 10 20 30 40

0

0.02

0.04

0.06

0.08

0.1

0.12

0 10 20 30 40

Eµ=30 GeV, L=7400 km, 10 21 µ- decays τ enhanced sample

Evis(GeV)

dN

/dE

ν (E

ven

ts/1

.6 G

eV p

er 1

0 kt

on

)

Evis(GeV)

ντ CC events

Other events

Evis(GeV) Evis(GeV)

0

20

40

60

80

100

120

140

0 10 20 30 40

Electrons Right sign µ

Wrong sign µ No lepton

νe→ντoscillations!!

Tau contributionenhanced for all eventclasses


Quasi-elastic events

Provide -ν separation for

all flavors:

ν

Üνl + n → l- + p

Üνl + p → l++ n

Real ν eventin the 50 liter LAr TPC in

CERN WANF beam

νµ + n → µ − + pCERN ν-beam

Only way to determine helicity ofelectron neutrino without explicitelectron charge measurement


Goals of Experiments at

For second generation long baseline experiments,the main goals will be:

NUFACT

O ∆ ΘO ΘO

O


Parameters are determined by fit of visibleenergy from the different classes.

O χO L for

Beam systematics: uncorrelated (25 bins)

Background added in fit

Earth density and oscillation parameters can in the fit or be to reference value

Fitting procedure


Precise determination of ∆m223,

Assume

Θ23

13= 0 Θ 2-family ➩ νµ→ν oscillations

Measurement dominated

by disappearance dip

at large distances

for right-sign

τ

:µ

O ∆O Θ

Eµ = 30 GeV, 2 x 10 20 µ decays

0

5000

10000

15000

20000

25000

0 10 20 30 40Evisible (GeV)

d

N/d

Eν

(νµ

CC

eve

nts

/1.6

GeV

per

10

kto

n)

0

200

400

600

800

1000

1200

1400

1600


0

50

100

150

200

250


No oscillations

∆m2=3.5 10-3 eV2

∆m2=5 10-3 eV2

∆m2=7 10-3 eV2


Right-sign muon disappearance

O

Oνµ→ντ→τ→µO

Contributions to events in the dip:

O

Oνµ→ντ→τ→µO

Eµ = 30 GeV, L = 7400 km, 2 x 10 20 µ decays

0

10

20

30

40

50

60

0 5 10 15 20 25 30 35 40Evisible (GeV)

dN

/dE

ν (ν

µ C

C e

ven

ts/1

.6G

eV p

er 1

0 kt

on

)

20% resolution µmomentum measurementPerfect µmomentum measurement

Eµ = 30 GeV, L = 7400 km, 2 x 10 20 µ decays

0

10

20

30

40

50

60

0 5 10 15 20 25 30 35 40Evisible (GeV)

dN

/dE

ν (ν

µ C

C e

ven

ts/1

.6G

eV p

er 1

0 kt

on

)

νµ + ντ CC + backgroundνµ CCντ CCBackground


Sensitivity for ∆m223,θ23 measurements

L = 732 km

0.002

0.003

0.004

0.005

0.006

0.007

0.008

0.009

0 0.2 0.4 0.6 0.8 1sin2 Θ23

∆m2 23

(eV

2 ) Eµ = 30 GeV, L = 2900 km, 2 x 10 20 µ decays

0.002

0.003

0.004

0.005

0.006

0.007

0.008

0.009

0 0.2 0.4 0.6 0.8 1sin2 Θ23

∆m2 23

(eV

2 ) Eµ = 30 GeV, L = 7400 km, 2 x 10 20 µ decays

0.002

0.003

0.004

0.005

0.006

0.007

0.008

0.009

0 0.2 0.4 0.6 0.8 1sin2 Θ23

∆m2 23

(eV

2 )

Consistent with Barger et al. hep-ph/9911524

Event simulation includes:¥Background¥Exclusive τ decays¥Resolution2% Beam systematics

Error on ∆m223=1%


Statistical improvements

A factor 10 morestatistics can stillimprove themeasurement at verylong distances

Eµ = 30 GeV, 2 x 10 20 µ decays

0.3

0.32

0.34

0.36

0.38

0.4

x 10-2

0.3 0.35 0.4 0.45 0.5 0.55 0.6 0.65 0.7sin2 Θ23

∆m2 23

(eV

2 )

0.3

0.32

0.34

0.36

0.38

0.4

x 10-2

0.3 0.35 0.4 0.45 0.5 0.55 0.6 0.65 0.7sin2 Θ23

∆m2 23

(eV

2 )


With

3-family mixing

13Θ 0, all flavors

mix.

Assuming

≠

m223>0,

oscillations involving ∆

νν are

by MSWinteractions withmatter

0

0.2

0.4

0.6

0.8

1

1.2

1.4

0 0.5 1 1.5 2 2.5 3D/∆m2 32D/∆m2 32D/∆m2 32

0

0.2

0.4

0.6

0.8

1

1.2

1.4

0 5 10 15 20 25 30 35

Eν (GeV) for ρ=3.7 g/cm3


Sensitivity to θ13

Sensitivity to 13

strongly depends onbackground levelassumed for wrong-sign muons

Negligible contributionfrom other classes

Θ

2 orders of magnitude better than ICANOE at CNGS

Eµ = 30 GeV, L = 7400 km

10-4

10-3

10-2

10-6 10-5 10-4 10-3 10-2 10-1 1sin2 2Θ13

∆m2 23

(eV

2 )90% ALLOWED

SUPER-K ALLOWED

2 x 1020 µ(background)

2 x 1020 µ(no background)

2 x 1021 µ(no background)

2 x 1021 µ(background)


Quasi-elastic events can confirm discovery of

Quasi-elastics

e oscillations. For sin22νµ→ν 13=0.05:θ


Measurement of Θ13

13 mainly determined

by wrong-signmuons.

Including electrons,NC and kinematicsfor

Θ

can improve

precision by morethan 30%

τ


Earth density

The resonance position,

visible in wrong-signmuons, gives ameasurement of themean density

→

Em eV

g cmres

νθ

ρ≈ ×1 32 10 24

13 232 2

3

. cos ( )( / )

∆

Resonance position dependson Θ13∆m2

13,ρ

¥For small θ13, cos2θ13Å1

¥Æm223 measured independently

by right-sign muon disappearance

Eµ = 30 GeV, L = 7400 km, 10 21 µ+ decays, ∆m2 = 3.5 x 10-3 eV2

0

20

40

60

80

100

120

140

160

180

0 5 10 15 20 25 30 35 40Evisible (GeV)

dN

/dE

ν (ν

µ C

C e

ven

ts/1

.6G

eV p

er 1

0 kt

on

)


Influence of density

Density fixed totrue value:

(sin22σ 13)=0.0071θ(sin2σ 23)=0.044θ

Density left freein the fit:

(sin22σ 13)=0.0074θ(sin2σ 23)=0.050θ

0.03

0.04

0.05

0.06

0.07

0.4 0.425 0.45 0.475 0.5 0.525 0.55 0.575 0.6sin2 Θ23

sin

2 2Θ

13

sin2 Θ23

sin

2 2Θ

13

0.03

0.04

0.05

0.06

0.07

0.4 0.425 0.45 0.475 0.5 0.525 0.55 0.575 0.6


Over-constraining the oscillation

For 3 active neutrinos: Σx=e, µ, τ P(νx → νy)= 1

Assuming new phenomena in oscillations to τ neutrinos, probabilities would change:

P(νµ → ντ) → α P(νµ → ντ) P(νe→ ντ) → βP(νe → ντ)

Precision on α: O(1%)

Precision on β: O(20%)


Over-constraining the oscillation

As expected, allevent classescontribute toover-constrain theoscillation to ντ

Eµ = 30 GeV, L=2900 km, 2 x 10 20 µ decays

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

0.8 0.85 0.9 0.95 1 1.05 1.1 1.15 1.2α P(νµ→ ντ)

χ2

All eventsRight sign µ +electronsRight sign µ


Effects of CP Violation

0

1000

2000

3000

4000

5000

6000

0 10 20 30 40

0

5

10

15

20

25

30

35

0 10 20 30 40

020406080

100120140160180

0 10 20 30 40

Evis (GeV)

Eve

nts

/1.6

GeV

Electrons

Evis (GeV)

Eve

nts

(δ=π

/2-δ

=0)/

1.6

GeV

Evis (GeV)

Eve

nts

/1.6

GeV δ=π/2

δ=0

Wrong-sign muons

Evis (GeV)

Eve

nts

(δ=π

/2-δ

=0)/

1.6

GeV

-20

-15

-10

-5

0

5

0 10 20 30 40

Increase number of electrons

(large, but drawn in the BG)

Change shape in wrong-sign muons

(smaller but much cleaner)

L=2900 km, ∆m212=10-4eV2, ∆m2

23=3.5*10-3eV2, sin2θ23=sin2 θ 12=0.5, sin22θ13=0.05


Sensitivity to CP violation

Sensitivity to CP forwrong-sign muons ismaximal at L=2900km, for neutrinoenergies around 10GeV

-0.5-0.4-0.3-0.2-0.1

00.10.20.30.40.5

0 10 20 30 40-0.5-0.4-0.3-0.2-0.1

00.10.20.30.40.5

0 10 20 30 40

ν–

e→ν–

µ

L=732 kmL=732 kmL=732 kmL=732 kmEν (GeV)

N(δ

=π/2

)-N

(δ=0

)/√N

(δ=0

)

∆m2 23 =3.5 x 10-3 eV2

∆m2 23 =5.0 x 10-3 eV2

∆m2 23 =7.0 x 10-3 eV2


N(δ

=π/2

)-N

(δ=0

)/√N

(δ=0

)

∆m2 23 =3.5 x 10-3 eV2

∆m2 23 =5.0 x 10-3 eV2

∆m2 23 =7.0 x 10-3 eV2


N(δ

=π/2

)-N

(δ=0

)/√N

(δ=0

)

∆m2 23 =3.5 x 10-3 eV2

∆m2 23 =5.0 x 10-3 eV2

∆m2 23 =7.0 x 10-3 eV2

-0.5-0.4-0.3-0.2-0.1

00.10.20.30.40.5

0 10 20 30 40

Maximalsensitivity


δ vs θ13

When CP violation onlyleads to anormalization factor,the effect is verycorrelated to avariation in 13θ

0.04

0.0425

0.045

0.0475

0.05

0.0525

0.055

0.0575

0.06

0 0.5 1 1.5 2 2.5 3

Eµ=30 GeV, 2 x 10 21 µ decays

δ (rad)

sin

2 2Θ

13

(68% C.L.)

(90% C.L.)

(99% C.L.)

δ (rad)

sin

2 2Θ

13

(68% C.L.)

(90% C.L.)

(99% C.L.)0.04

0.0425

0.045

0.0475

0.05

0.0525

0.055

0.0575

0.06

0 0.5 1 1.5 2 2.5 3

Correlation is much smallerwhen also a shape changeoccurs


δ vs ρ

0.5

0.75

1

1.25

1.5

1.75

2

2.25

2.5

2.25 2.5 2.75 3 3.25 3.5 3.75 4 4.25 4.5

L=2900 km, 2 x 1021 µ decays

ρ (g/cm3)

δ (r

ad)

(68% C.L.)(90% C.L.)(99% C.L.)

ρ (g/cm3)

δ (r

ad)

(68% C.L.)(90%

C.L.)(99% C.L.)

0.5

0.75

1

1.25

1.5

1.75

2

2.25

2.5

2.25 2.5 2.75 3 3.25 3.5 3.75 4 4.25 4.5

Density free

Density known at 3%

No need for more baselines!


Use of quasi-elastic events

The CP violation effect is large for the electrons,but is hard to see due to background from

the beam. Clean signal in quasi-elastic events

νe


Sensitivity to δ

Amplitude of CP-violating effectsstrongly depends on alloscillation parameters,in particular m2

12.∆

Eµ= 30 GeV, L=2900 km

δ (rad)

∆m2 12

(eV

2 )

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

0.09

0.1

x 10-3

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6

90% Excluded

CP phase sensitivity

2 x 10 muon decays

2 x 10 muon decays20

21

Solar LMA Allowed

High fluxes needed, apart froma little corner of the parameterspace


Measurement of CP violation

In the most favorable case,the phase can be

measured with a 20%accuracy at L=2900 km.

δ

1Dscan DELTA, all other free

Eµ=30 GeV, L=2900 km, 2 x 10 21 µ decays

δm223=3.5 × 10-3 eV2 δm212= 1 × 10-4 eV2

sin2 Θ23=0.5 sin2 Θ12=0.5 sin2 2 Θ13=0.05 δ=π/2

All events

Only µElectrons and no leptons

δ (rad)

χ2

0

1

2

3

4

5

6

7

1 1.2 1.4 1.6 1.8 2

Electron and NC-like events alsocontribute, albeit marginally, tothe fit


Conclusions

Neutrino factory allows simultaneous study of manyoscillation phenomena

O

ÜA general-purpose detector is needed for:Ð Electrons

Ð Tau identification

Ð Quasi-elastic events

Ð Neutral current-like events.

These events contribute to the main measurements:O

Üθ13,

and provide essential cross-checks

νe→ντ, CP violation

To look for new phenomena, we need to over-constrain the oscillation pattern

O

Documents

A.Bueno, M.Campanelli, A.Rubbia ETH Zurichneutrino.ethz.ch/Talks_pdfs/Monterey_nufact.pdf · Antonio Bueno & Mario Campanelli & Andr” Rubbia, ETH/Zurich May 2000 Neutrino Oscillations