NOW2008
Physics Potential of
Future Atmospheric Neutrino Searches
Thomas Schwetz-Mangold
CERN
T. Schwetz, NOW2008 – p.1
We have learned a lot from atm. neutrinos
3000+ citations
T. Schwetz, NOW2008 – p.2
We have learned a lot from atm. neutrinos...
20
∆χ
2
15
10
atmospheric
MINOS
atmospheric + MINOS
3σ
5
90% CL
0
5
2
∆m31
[ 10 eV ]
2
-3
3
3σ
4
90% CL
global
Schwetz, Tortola,
Valle, 0808.2016
MINOS
★
2
1
0
0
atmospheric
0.25
0.5
2
sin θ23
0.75
1 0
5
10
∆χ
15
20
2
... but LBL experiments are taking over (MINOS, T2K, NOvA)
T. Schwetz, NOW2008 – p.3
Can we learn something more from
atmospheric neutrinos in the era of
precision neutrino oscillation experiments?
T. Schwetz, NOW2008 – p.4
Can we learn something more from
atmospheric neutrinos in the era of
precision neutrino oscillation experiments?
LBL experiments suffer from degeneracies
• octant degeneracy:
cannot distinguish between θ23 and (π/2 − θ23 )
• hierarchy degeneracy:
cannot determine the sign of ∆m231
T. Schwetz, NOW2008 – p.4
Hierarchy and octant degeneracies in T2HK
π/2
allowed regions at
2σ, 99%, 3σ CL
δCP
0
-π/2
true solution
★
-π
0
0.01
0.02
0.03
2
sin 2θ13
0.04
0.05
true values:
sin2 2θ13 = 0.03
δCP = −0.85π
sin2 θ23 = 0.4
∆m231 = 2.2 × 10−3 eV2
T. Schwetz, NOW2008 – p.5
Hierarchy and octant degeneracies in T2HK
π/2
wrong θ23 and hierarchy
allowed regions at
2σ, 99%, 3σ CL
wrong hierarchy
δCP
0
-π/2
wrong θ23
true solution
★
-π
0
0.01
0.02
0.03
2
sin 2θ13
0.04
0.05
true values:
sin2 2θ13 = 0.03
δCP = −0.85π
sin2 θ23 = 0.4
∆m231 = 2.2 × 10−3 eV2
ambiguities in θ13 and δCP
no information on θ23 octant and sgn(∆m231 )
T. Schwetz, NOW2008 – p.5
Resolving the degeneracies
several possibilities to resolve the degeneracies are known:
• combining information from detectors at different baselines
• using additional oscillation chanels (νe → ντ )
• spectral information (broadband beam)
• adding information on θ13 from a reactor experiment
• ...
T. Schwetz, NOW2008 – p.6
Resolving the degeneracies
several possibilities to resolve the degeneracies are known:
• combining information from detectors at different baselines
• using additional oscillation chanels (νe → ντ )
• spectral information (broadband beam)
• adding information on θ13 from a reactor experiment
• ...
or
use the atmospheric neutrinos in the same detector
Huber, Maltoni, Schwetz, PRD71, 053006 (2005) [hep-ph/0501037]
T. Schwetz, NOW2008 – p.6
3-flavour effects in atmospheric neutrinos
Incomplete list:
Petcov, Phys. Lett. B434, 321 (1998), hep-ph/9805262; Akhmedov, Nucl. Phys. B538, 25 (1999),
hep-ph/9805272; Akhmedov, Dighe, Lipari, Smirnov, Nucl. Phys. B542, 3 (1999),
hep-ph/9808270; Kim, Lee, Phys. Lett. B444, 204 (1998), hep-ph/9809491; Peres, Smirnov,
Phys. Lett. B456, 204 (1999), hep-ph/9902312; Bernabeu, Palomares-Ruiz, Perez, Petcov,
Phys. Lett. B531, 90 (2002), hep-ph/0110071; Gonzalez-Garcia, Maltoni, Eur. Phys. J. C26, 417
(2003), hep-ph/0202218; Bernabeu, Palomares-Ruiz, Petcov, Nucl. Phys. B669, 255 (2003),
hep-ph/0305152; Peres, Smirnov, Nucl. Phys. B680, 479 (2004), hep-ph/0309312;
Gonzalez-Garcia, Maltoni, Smirnov, Phys. Rev. D70, 093005 (2004), hep-ph/0408170; Fogli, Lisi,
Marrone, Palazzo, hep-ph/0506083; Huber, Maltoni, Schwetz, Phys. Rev. D71, 053006 (2005),
hep-ph/0501037; T. Kajita (Super-K), see e.g. talks at NuFact05, NuInt05; Petcov, Schwetz, Nucl.
Phys. B740, 1 (2006) 1, hep-ph/0511277; S. Choubey, hep-ph/0609182; E. K. Akhmedov,
M. Maltoni and A. Y. Smirnov, JHEP 0705 (2007) 077, hep-ph/0612285; R. Gandhi, P. Ghoshal,
S. Goswami, P. Mehta, S. U. Sankar and S. Shalgar, Phys. Rev. D 76 (2007) 073012, 0707.1723;
E. K. Akhmedov, M. Maltoni and A. Y. Smirnov, JHEP 0806 (2008) 072, 0804.1466.
T. Schwetz, NOW2008 – p.7
Oscillation signal in atm neutrino exps
atmosphere provides a multi-flavour neutrino flux
containing νµ and νe :
Nµ = (φµ Pνµ →νµ + φe Pνe →νµ )σµ
Ne = (φµ Pνµ →νe + φe Pνe →νe )σe
1
= φµ (Pνµ →νµ + Pνe →νµ )σµ
r
= φe (rPνµ →νe + Pνe →νe ) σe
|
{z
}
Peff
φµ (Eν )
r = r(Eν ) ≡
φe (Eν )
only a combination of probabilities can be measured
T. Schwetz, NOW2008 – p.8
3-flavour effects in atmospheric neutrinos
excess of electron-like events:
Ne
Ne0
− 1 ≃ (r s223 − 1) P2ν (∆m231 , θ13 )
θ13 -effects
+ (r c223 − 1) P2ν (∆m221 , θ12 )
∆m221 -effects
− 2s13 s23 c23 r Re(A∗ee Aµe )
interference: δCP
φµ (Eν )
r = r(Eν ) ≡
φe (Eν )
r ≈ 2 (sub-GeV)
r ≈ 2.6 − 4.5 (multi-GeV)
T. Schwetz, NOW2008 – p.9
θ13-effects
Ne
2
2
(r
s
P
(∆m
−
1)
−
1
≃
2ν
23
31 , θ13 )
0
Ne
resonant matter effect in P2ν (∆m231 , θ13 )
for multi-GeV events (r ≈ 2.6 − 4.5)
normal hierarchy: enhancement for neutrinos
inverted hierarchy: enhancement for anti-neutrinos
detection cross sections are different for neutrinos
and anti-neutrinos
sensitivity to the neutrino mass hierarchy
T. Schwetz, NOW2008 – p.10
θ13-effects
M. Maltoni, arXiv:0707.1218
T. Schwetz, NOW2008 – p.11
∆m221-effects
Ne
−1≃
0
Ne
(r c223 − 1) P2ν (∆m221 , θ12 )
relevant for sub-GeV events
sensitivity to the octant of θ23
due to “flux factor” (r c223 − 1)
note oposite θ23 dependence of multi-GeV
θ13 features: (r s223 − 1)
M. Maltoni, arXiv:0707.1218
T. Schwetz, NOW2008 – p.12
A megaton water Cerenkov detector
•
Many proposed long-baseline experiments rely
on a Mt-scale water Cerenkov detector
US-WBB → DUSEL, T2K → HK
CERN BB/SPL → MEMPHYS
•
high statistics atmospheric neutrino data
come “for free”
•
combine LBL and atmospheric data
Huber, Maltoni, Schwetz, hep-ph/0501037
T. Schwetz, NOW2008 – p.13
A megaton water Cerenkov detector
Consider ∼ 5 Mt yr atmospheric neutrino data in a
water Cerenkov detector:
e-like sub-GeV
e-like multi-GeV
µ-like sub-GeV
µ-like multi-GeV
upward going µ
ν
ν̄
∼ 105
∼ 3 × 104
∼ 105
∼ 5 × 104
∼ 6 × 104
∼ 3 × 104
∼ 104
∼ 3 × 104
∼ 2 × 104
∼ 3 × 104
sin2 2θ13 = 0.05, sin2 θ23 = 0.5, sin2 θ12 = 0.3, δCP = 0,
∆m221 = 8.1 × 10−5 eV2 , ∆m231 = 2.2 × 10−3 eV2
T. Schwetz, NOW2008 – p.14
Resolving the degeneracies - ex.: T2HK
2
True sin θ23 = 0.4
π/2
wrong θ23 and hierarchy
wrong hierarchy
δCP
0
-π/2
wrong θ23
true solution
★
-π
0
0.01
0.02
0.03
2
sin 2θ13
0.04
0.05
solid curves: LBL only
allowed regions at 2σ, 99% and 3σ CL (2 dof)
true values: sin2 2θ13 = 0.03, δCP = −0.85π, ∆m231 = 2.2 · 10−3 eV2
T. Schwetz, NOW2008 – p.15
Resolving the degeneracies - ex.: T2HK
2
True sin θ23 = 0.4
π/2
2
wrong θ23 and hierarchy (∆χ = 21.1)
2
wrong hierarchy (∆χ = 5.0)
δCP
0
-π/2
2
wrong θ23 (∆χ = 18.7)
true solution
★
-π
0
0.01
0.02
0.03
2
sin 2θ13
0.04
0.05
solid curves: LBL only, colored regions: LBL+ATM
allowed regions at 2σ, 99% and 3σ CL (2 dof)
true values: sin2 2θ13 = 0.03, δCP = −0.85π, ∆m231 = 2.2 · 10−3 eV2
T. Schwetz, NOW2008 – p.15
Resolving the degeneracies - ex.: T2HK
2
True sin θ23 = 0.6
2
True sin θ23 = 0.4
π/2
2
wrong θ23 and hierarchy (∆χ = 21.1)
2
wrong θ23 and hierarchy (∆χ = 35.9)
2
wrong hierarchy (∆χ = 5.0)
0
2
δCP
wrong hierarchy (∆χ = 18.6)
-π/2
2
wrong θ23 (∆χ = 18.7)
2
wrong θ23 (∆χ = 25.2)
true solution
true solution
★
-π
0
0.01
0.02
0.03
2
sin 2θ13
0.04
0.05 0
0.01
★
0.02
0.03
2
sin 2θ13
0.04
0.05
solid curves: LBL only, colored regions: LBL+ATM
allowed regions at 2σ, 99% and 3σ CL (2 dof)
true values: sin2 2θ13 = 0.03, δCP = −0.85π, ∆m231 = 2.2 · 10−3 eV2
T. Schwetz, NOW2008 – p.15
Identifying the octant of θ23
Sensitivity of LBL+ATM data to the octant of θ23
30
10
0
ATM data from a 500 kt
WC detector
0.4
ATM-
only
20
cur. excl. @ 2σ
2
o
K
T2H
SPL
∆χ of the wrong octant
sens. to θ23 = 45
3σ
2σ
0.5
2
true value of sin θ23
quite powerful to resolve
the octant degeneracy,
even for θ13 = 0
robust signature in
sub-GeV e-like events
0.6
Campagne, Maltoni, Mezzetto, Schwetz, hep-ph/0603172
T. Schwetz, NOW2008 – p.16
The hierarchy problem
T. Schwetz, NOW2008 – p.17
Identifying the mass hierarchy
LBL + ATM data from a 500 kt WC detector:
2σ sensitivity to normal hierarchy from LBL + ATM data
0.05
O
νA
+
(p.dr.)
A
ν
O
N
4 MW
T2K@
N
βB
0.03
2
true sin 2θ13
0.04
βB
L
P
S
0.02
T2HK
T2HK
0.01
0
SPL
0
π/2
π
true δCP
3π/2
2π 0
0.25
0.5
0.75
fraction of true δCP values
1
Campagne, Maltoni, Mezzetto, Schwetz, hep-ph/0603172
T. Schwetz, NOW2008 – p.18
Identifying the mass hierarchy
LBL + ATM data from a 500 kt WC detector:
2σ sensitivity to normal hierarchy from LBL + ATM data
0.05
O
νA
+
(p.dr.)
A
ν
O
N
4 MW
T2K@
N
βB
0.03
2
true sin 2θ13
0.04
βB
L
P
S
0.02
T2HK
T2HK
0.01
0
SPL
0
π/2
π
true δCP
3π/2
2π 0
0.25
0.5
0.75
fraction of true δCP values
1
Campagne, Maltoni, Mezzetto, Schwetz, hep-ph/0603172
sensitivity improves for θ23 > 45◦ because of (r s223 − 1) factor
T. Schwetz, NOW2008 – p.18
Magnetized iron detectors
•
Water Cerenkov:
- sees only sum ν + ν̄ → dilution of the effect
+ can be made very big (Mt scale)
•
Magnetized iron:
+ can distinguish ν from ν̄ events
- electron detection difficult → µ-like events
T. Schwetz, NOW2008 – p.19
Magnetized iron detectors
•
Water Cerenkov:
- sees only sum ν + ν̄ → dilution of the effect
+ can be made very big (Mt scale)
•
Magnetized iron:
+ can distinguish ν from ν̄ events
- electron detection difficult → µ-like events
Indian Neutrino Observatory:
∼ 50 kt magnetized Iron calorimeter
see also talk by S. Goswami
T. Schwetz, NOW2008 – p.19
The mass hierarchy signal in µ-like events
0
term A
total
term B
NH
IH
Φµ σ (Posc − Posc )
σ(Eν) = 5%
[arbitrary units]
difference of the µ-like event spectra for NH and IH
term B
σ(Eν) = 15%
total
0
term A
2
2
2
2
sin 2θ13 = 0.1, ∆m = 0.0025 eV , sin θ23 = 0.5 (thin), 0.7 (thick), cosθnadir = 0.9
2
3
∆Sµ ∝ Φµ σ sin2 θ23
|
4
5
Eν [GeV]
„
1
− sin2 θ23
r
{z
term A
72
6
«
3
4
5
Eν [GeV]
6
7
1
∆P2ν + Φµ σ sin2 2θ23 ∆Re (A′33 )
2
|
{z
}
}
term B
T. Schwetz, NOW2008 – p.20
The mass hierarchy signal in µ-like events
the ability to reconstruct the neutrino energy and
neutrino direction is crucial
o
solid:
5% energy resolution
dashed: 15% energy resolution
6
solid:
5 angular resolution
o
dashed: 15 angular resolution
5
4
e-like ev
3
ents
2
µ-
2
∆χ (NH vs IH) per 100 events
7
1
0
1
lik
ee
e-like events
ven
µ-like events
ts
10
5
15
angular resolution [degree]
20 1
5
10
15
energy resolution [%]
20
Petcov, Schwetz, NPB 740 (2006) 1 [hep-ph/0511277]
T. Schwetz, NOW2008 – p.21
The mass hierarchy and magnetized detectors
15%
energy res.
o
15 angular res.
8
5%
energy res.
o
5 angular res.
30
6
20
2σ
4
3σ
10
2
2σ
2
∆χwr hier for 4000 events
consider 500 kty data (e.g., INO with 50 kt for 10 yrs)
0
0
0.05
0.1
2
0.15
0
0
0.05
0.1
2
true value of sin 2θ13
true value of sin 2θ13
osc. params. fixed, external prior information
solid: true hierarchy normal, dashed: true hierarchy inverted
T. Schwetz, NOW2008 – p.22
Which type of detector?
The ideal detector should be able to
•
see e-like events with charge ID
(at least statistically),
•
see µ-like events with charge ID,
•
reconstruct neutrino energy (direction) at the level
of few % (degree) for µ like events,
•
and it should be VERY BIG.
T. Schwetz, NOW2008 – p.23
Which type of detector?
The ideal detector should be able to
•
see e-like events with charge ID
(at least statistically),
•
see µ-like events with charge ID,
•
reconstruct neutrino energy (direction) at the level
of few % (degree) for µ like events,
•
and it should be VERY BIG.
Water Cerenkov vs mag. Iron Cal. vs liquid Argon ?
T. Schwetz, NOW2008 – p.23
Which type of detector?
Number of events needed for a 2σ identification of the hierarchy
5
10
number of events with
0.1 < cosθnadir < 1, E > 2 GeV
e-like, no CID
4
10
µ-li
ke
, 10
0%
1 Mt yr
CID
500 kt yr
for ~ 80% efficiency
5 Mt yr
e-like, 50% CID
3
10
µ-lik
e, hi
solid: true NH
dashed: true IH
gh re
sol.
2
100.02
0.05
0.1
2
true value of sin 2θ13
23-params @ 5%
(5%
o
,5 )
2
δ(sin 2θ13) = 0.02
0.15
T. Schwetz, NOW2008 – p.24
Comment - 1
Separation of neutrino and anti-neutrino events
(statistical or event-by-event) in 100 kt scale WC or
LAr detectors would be very useful for atmospheric
neutrino studies
and also in the context of a Neutrino Factory
see Huber, Schwetz, 0805.2019
n/p tagging, muon life time, single/multi-ring...??
T. Schwetz, NOW2008 – p.25
Comment - 1
Example: single/multi-ring samples in a WC:
Nsingle−ring = ANν + BNν̄
Nmulti−ring = CNν + DNν̄
the ν and ν̄ content of single and multi-ring events are
different
can solve for Nν and Nν̄ from a measurement of
Nsingle−ring and Nmulti−ring
T. Schwetz, NOW2008 – p.26
Comment - 1
Example: single/multi-ring samples in a WC
T. Schwetz, NOW2008 – p.27
Comment - 2
Atmospheric ν can solve the hierarchy problem for large θ13 , but
cannot compete with (very-)LBL experiments for small θ13
Mass hierarchy at 3Σ CL
1
SPL (130 km) and
T2HK (295 km)
include 5 Mt yr WC
atm neutrino data
NOΝA* b
WBB-WCb
0.8
T2KKb
CP fraction
T2HKa - 2% sys
0.6
NOνA∗ :
100 kt LAr @ 820 km
3 yr ν, 3 yr ν̄ @ 1.1 MW
SPLa - 2% sys
@aD arXiv:0710.4947
@bD hep-ph0703029
0.4
T2KK:
270 kt WC @ 295 & 1050 km
4 yr ν, 4 yr ν̄ @ 4 MW
0.2
plot by P. Huber
0
10-3
GLoBES 2008
10-2
sin2 2Θ13
10-1
WBB:
300 kt WC @ 1290 km
5yr ν @ 1 MW, 5yr ν̄ @ 2 MW
T. Schwetz, NOW2008 – p.28
Beyond oscillations
T. Schwetz, NOW2008 – p.29
Earth tomography using oscillations?
PA : effective
2ν appearance
probability
E. K. Akhmedov, M. Maltoni and A. Y. Smirnov, JHEP 0705, 077 (2007)
T. Schwetz, NOW2008 – p.30
Earth tomography using oscillations?
need very good energy and angular resolution
... and many many many many events!
PA : effective
2ν appearance
probability
E. K. Akhmedov, M. Maltoni and A. Y. Smirnov, JHEP 0705, 077 (2007)
T. Schwetz, NOW2008 – p.30
Beyond oscillations
Sensitivity of atmospheric neutrino data to new physics:
incomplete list of references:
non-standard interactions
N. Fornengo, M. Maltoni, R. T. Bayo and J. W. F. Valle, Phys. Rev. D 65, 013010 (2002)
A. Friedland, C. Lunardini and M. Maltoni, Phys. Rev. D 70, 111301 (2004)
A. Friedland and C. Lunardini, Phys. Rev. D 72, 053009 (2005)
Lorentz violation, equivalence principle
G. L. Fogli, E. Lisi, A. Marrone and G. Scioscia, Phys. Rev. D 60 (1999) 053006
M. C. Gonzalez-Garcia and M. Maltoni, Phys. Rev. D 70 (2004) 033010
Quantum decoherence
G. L. Fogli, E. Lisi, A. Marrone and D. Montanino, Phys. Rev. D 67, 093006 (2003)
Neutrino decay
G. L. Fogli, E. Lisi, A. Marrone and G. Scioscia, Phys. Rev. D 59, 117303 (1999)
S. Choubey and S. Goswami, Astropart. Phys. 14, 67 (2000)
V. D. Barger et al., Phys. Lett. B 462, 109 (1999)
M. C. Gonzalez-Garcia and M. Maltoni, Phys. Lett. B 663, 405 (2008)
T. Schwetz, NOW2008 – p.31
TeV atmospheric neutrinos in Ice Cube
There are many atmospheric neutrino events in Ice
Cube with energy ∼ TeV
M. C. Gonzalez-Garcia, F. Halzen and M. Maltoni, Phys. Rev. D 71, 093010 (2005)
T. Schwetz, NOW2008 – p.32
TeV atmospheric neutrinos in Ice Cube
Non-standard neutrino properties
M. C. Gonzalez-Garcia, F. Halzen and M. Maltoni, Phys. Rev. D 71, 093010 (2005)
eV-scale sterile neutrinos
S. Choubey, JHEP 0712, 014 (2007) [arXiv:0709.1937 [hep-ph]]
Earth tomography by neutrino absorption
M.C.Gonzalez-Garcia, F.Halzen, M.Maltoni, H.K.M.Tanaka, Phys.Rev.Lett. 100, 061802 (2008)
T. Schwetz, NOW2008 – p.33
Summary
T. Schwetz, NOW2008 – p.34
Summary
atmospheric neutrinos will continue to be very
interesting for neutrino oscillations
T. Schwetz, NOW2008 – p.35
Summary
atmospheric neutrinos will continue to be very
interesting for neutrino oscillations
Three-flavour effects in ATM data provide sensitivity
to mass ordering and octant of θ23
•
octant: good sensitivity of atm data
•
hierarchy: sensitivity for sin2 2θ13 & 0.02
T. Schwetz, NOW2008 – p.35
Summary
But: One needs really large detectors
•
500 kt water Cerenkov
100 kt liquid Argon
•
50 kt magnetized Iron calorimeter
•
T. Schwetz, NOW2008 – p.36
Summary
But: One needs really large detectors
•
500 kt water Cerenkov
100 kt liquid Argon
•
50 kt magnetized Iron calorimeter
•
Apart from being big, the requirements are (ideally):
•
good (neutrino) energy reconstruction
•
good (neutrino) direction reconstruction
•
ν/ν̄ separation for νµ and νe
(ev-by-ev or statistically)
T. Schwetz, NOW2008 – p.36