Post on 04-Jul-2020
Antonio Bueno & Mario Campanelli & Andr� Rubbia, ETH/Zurich May 2000
A.Bueno, M.Campanelli, A.Rubbia ETH Zurich
hep-ph/0005007
Antonio Bueno & Mario Campanelli & Andr� Rubbia, ETH/Zurich May 2000
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:
Antonio Bueno & Mario Campanelli & Andr� Rubbia, ETH/Zurich May 2000
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
Antonio Bueno & Mario Campanelli & Andr� Rubbia, ETH/Zurich May 2000
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→
Antonio Bueno & Mario Campanelli & Andr� Rubbia, ETH/Zurich May 2000
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
Antonio Bueno & Mario Campanelli & Andr� Rubbia, ETH/Zurich May 2000
With the high fluxes foreseen at the NeutrinoFactory we can think of very long baselines:
Possible baselines
Ringlocation
Distanceto GS
Meandensity
Antonio Bueno & Mario Campanelli & Andr� Rubbia, ETH/Zurich May 2000
Event rates for a 10 kton detector
Eµ=30 GeV
No polarization
No beam divergence
No oscillations
Antonio Bueno & Mario Campanelli & Andr� Rubbia, ETH/Zurich May 2000
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
Antonio Bueno & Mario Campanelli & Andr� Rubbia, ETH/Zurich May 2000
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
Antonio Bueno & Mario Campanelli & Andr� Rubbia, ETH/Zurich May 2000
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
Antonio Bueno & Mario Campanelli & Andr� Rubbia, ETH/Zurich May 2000
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
Antonio Bueno & Mario Campanelli & Andr� Rubbia, ETH/Zurich May 2000
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
Eµ = 30 GeV, L = 7400 km, 10 20 µ- decays
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
Eµ = 30 GeV, L = 7400 km, 10 20 µ- decays
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
Antonio Bueno & Mario Campanelli & Andr� Rubbia, ETH/Zurich May 2000
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
Antonio Bueno & Mario Campanelli & Andr� Rubbia, ETH/Zurich May 2000
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
Antonio Bueno & Mario Campanelli & Andr� Rubbia, ETH/Zurich May 2000
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
Antonio Bueno & Mario Campanelli & Andr� Rubbia, ETH/Zurich May 2000
Goals of Experiments at
For second generation long baseline experiments,the main goals will be:
NUFACT
O ∆ ΘO ΘO
O
Antonio Bueno & Mario Campanelli & Andr� Rubbia, ETH/Zurich May 2000
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
Antonio Bueno & Mario Campanelli & Andr� Rubbia, ETH/Zurich May 2000
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 10 20 30 40Evisible (GeV)
0
50
100
150
200
250
0 10 20 30 40Evisible (GeV)
No oscillations
∆m2=3.5 10-3 eV2
∆m2=5 10-3 eV2
∆m2=7 10-3 eV2
Antonio Bueno & Mario Campanelli & Andr� Rubbia, ETH/Zurich May 2000
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
Antonio Bueno & Mario Campanelli & Andr� Rubbia, ETH/Zurich May 2000
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%
Antonio Bueno & Mario Campanelli & Andr� Rubbia, ETH/Zurich May 2000
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 )
Antonio Bueno & Mario Campanelli & Andr� Rubbia, ETH/Zurich May 2000
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
Antonio Bueno & Mario Campanelli & Andr� Rubbia, ETH/Zurich May 2000
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)
Antonio Bueno & Mario Campanelli & Andr� Rubbia, ETH/Zurich May 2000
Quasi-elastic events can confirm discovery of
Quasi-elastics
e oscillations. For sin22νµ→ν 13=0.05:θ
Antonio Bueno & Mario Campanelli & Andr� Rubbia, ETH/Zurich May 2000
Measurement of Θ13
13 mainly determined
by wrong-signmuons.
Including electrons,NC and kinematicsfor
Θ
can improve
precision by morethan 30%
τ
Antonio Bueno & Mario Campanelli & Andr� Rubbia, ETH/Zurich May 2000
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
)
Antonio Bueno & Mario Campanelli & Andr� Rubbia, ETH/Zurich May 2000
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
Antonio Bueno & Mario Campanelli & Andr� Rubbia, ETH/Zurich May 2000
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%)
Antonio Bueno & Mario Campanelli & Andr� Rubbia, ETH/Zurich May 2000
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
Antonio Bueno & Mario Campanelli & Andr� Rubbia, ETH/Zurich May 2000
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
Antonio Bueno & Mario Campanelli & Andr� Rubbia, ETH/Zurich May 2000
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
L=2900 kmL=2900 kmL=2900 kmL=2900 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
L=7400 kmL=7400 kmL=7400 kmL=7400 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
-0.5-0.4-0.3-0.2-0.1
00.10.20.30.40.5
0 10 20 30 40
Maximalsensitivity
Antonio Bueno & Mario Campanelli & Andr� Rubbia, ETH/Zurich May 2000
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
Antonio Bueno & Mario Campanelli & Andr� Rubbia, ETH/Zurich May 2000
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!
Antonio Bueno & Mario Campanelli & Andr� Rubbia, ETH/Zurich May 2000
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
Antonio Bueno & Mario Campanelli & Andr� Rubbia, ETH/Zurich May 2000
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
Antonio Bueno & Mario Campanelli & Andr� Rubbia, ETH/Zurich May 2000
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
Antonio Bueno & Mario Campanelli & Andr� Rubbia, ETH/Zurich May 2000
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