Transcript Long baseline neutrino oscillations: Theoretical aspects

Long baseline neutrino oscillations:
Theoretical aspects
NOW 2008
Conca Specchiulla, Italy
September 9, 2008
Walter Winter
Universität Würzburg
Contents
 Theoretical motivation:
Quantities of interest
 How to measure these? - Phenomenology
 Experiment choice and optimization
 Neutrino factory: what can we expect?
 The potentially unexpected
 Summary
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Quantities of interest
Theoretical motivation
 Mass models describe masses and mixings (mass
matrices) by symmetries, GUTs, anarchy
arguments, etc.
 From that:
predictions for
observables
 Example:
Literature
research for q13
 q13 as performance
indicator for models
(Albright, Chen, 2006)
Talk: Mu-Chun Chen, Friday
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Some other examples
 Large mixings
from CL and n sectors?
Example: q23l = q12n = p/4, perturbations from CL sector
q12l dominates
q12 ~ p/4 + q13 cos dCP
 q13 > 0.1, dCP ~ p
q23 ~ p/4 – (q13)2/2
q13l dominates
dCP and
octant
discriminate
these
examples!
q12 ~ p/4 – q13 cos dCP
 q13 > 0.1, dCP ~ 0
q23 ~ p/4 + (q13)2/2
(can be connected with textures)
(Niehage, Winter, 2008)
 Another example: QLC+Flavor symmetries
lead e.g. to
k
k as performance indicator
for QLC models
Modern QLC scenarios do not have an exact factor k=1 there (depends on model)
(e.g. Plentinger, Seidl, Winter, 2008; see also: Frampton, Matsuzaki, 2008)
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Perform. indicators for theory
What observables test the theory space most efficiently?
 Magnitude of q13 (see before!)
 Mass hierarchy
(strongly affects textures)
 Deviations from max. mixing
(nm-nt symmetry?)
 q23 octant
 |sin2q12-1/3|
(tribimaximal mixings?)
 |sindCP-1| (CP violation)
(leptogenesis?)
 Value of dCP
 k qC+ q12 ~ p/4 ~ q23
(k as indicator for quark-lepton
unification models?)
 Dev. from std. osc. framework
(Antusch et al, hep-ph/0404268)
Most important for LBL experiments
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Long baseline phenomenology
Why GeV energies?
Unoscillated flux
 Cross sections ~ E (DIS regime)
 Flux ~ E2 (beam collimation)
 For fixed L: unoscillated event rate ~ E3
Oscillated flux
 Adjust baseline to stay on osc. maximum
Flux ~ 1/L2, L ~ E on oscillation maximum
 Event rate ~ E on oscillation maximum
 In addition:
Matter effects (resonance energy ~ 10 GeV in
Earth‘s mantle)
 Measure mass hierarchy, Flux(L) ~ const. at resonance
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GeV Long baseline experiments
Source
Production
… and Detection
Limitations
L
Beam,
Superbeam
Intrinsic
beam BGs,
systematics
100~ 0.5 –
2,500 km 5 GeV
Neutrino
factory
Charge
7002-25
identification, 7,500 km GeV
NC BG
b-beam
Source
luminosity
For leading atm. params
Signal prop. sin22q13
<E>
1000.3 –
7,500 km 10 GeV
Contamination
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Channels of interest
 Disappearance for Dm312, q23: nm  nm
D31 = Dm312 L/(4E)
NB: We expand in
 Appearance for q13, CPV, MH:
 Golden: ne  nm (NF/BB) or nm  ne (SB)
(e.g., De Rujula, Gavela, Hernandez, 1999; Cervera et al, 2000)
 Silver: ne  nt (NF – low statistics!?)
(Donini, Meloni, Migliozzi, 2002; Autiero et al, 2004)
 Platinum: nm  ne (NF: difficult!)
(see e.g. ISS physics working group report)
 Other appearance: nm  nt (OPERA, NF?)
 Neutral currents for new physics
(e.g., Barger, Geer, Whisnant, 2004; MINOS, 2008)
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Appearance channels




Antineutrinos:
Magic baseline:
Silver:
Superbeams, Plat.:
(Cervera et al. 2000; Freund, Huber, Lindner, 2000; Huber, Winter, 2003; Akhmedov et al, 2004)
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Degeneracies
 CP asymmetry
Iso-probability curves
b-beam, n
(vacuum) suggests
the use of neutrinos
and antineutrinos
 One discrete deg.
remains in (q13,d)-plane
b-beam, anti-n
Best-fit
(Burguet-Castell et al, 2001)
 Additional degeneracies:
(Barger, Marfatia, Whisnant, 2001)
 Sign-degeneracy
(Minakata, Nunokawa, 2001)
 Octant degeneracy
(Fogli, Lisi, 1996)
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Degeneracy resolution
 Matter effects (signdegeneracy) – long
baseline, high E
 Different beam energies
or better energy
resolution in detector
 Second baseline
 Good enough statistics
 Other channels
 Other experiment
classes
WBB FNAL-DUSEL,
T2KK, NF@long L, …
Monochromatic beam,
Beta beam with
different isotopes,
WBB, …
T2KK, magic baseline ~
7500 km, SuperNOvA
Neutrino factory, beta
beam, Mton WC
SB+BB CERN-Frejus,
silver/platinum @ NF
Atmospheric, …
Talk: Thomas Schwetz
(Minakata, Nunokawa, 2001; Parke)
(many many authors, see e.g. ISS physics WG report)
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On-axis WBB versus off-axis NBB
Example: NuMI-like beam  100kt liquid argon
On axis
sin22q13
CP violation
Mass hierarchy
FNALDUSEL
WBB
dCP=-p/2
dCP=+p/2
Constraint
from
NuMI
beam
Ash
River
OA,
NOvA*
C
(Barger et al, hep-ph/0703029)
Off-axis technology may not be necessary if the detector is good enough, i.e.,
has good BG rejection and good energy resolution! WC good enough???
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Quantification of performance
Commonly used performance indicators:
Indicator
Description
+
q13 sensitivity
(limit)
New q13 limit if no
signal
q13, CPV, MH
discovery reach
Range of (true) q13 Comprehensive
and dCP for which
picture of
q13, CPV, or MH
parameter space
can be discovered
Difficult to
visualize: Depends
on two true
parameters
Sensitivity to
octant
Range of (true)
q13, q23 (and dCP)
for which the q23
octant can be
established
Many true
parameter
dependencies
Does not depend
on (true) dCP, MH
Comprehensive
picture of
parameter space
Strongly affected
by degs
(corresponds to
worst case
discovery reach)
…
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Example: Discovery reaches
… and the “Fraction of dCP”
Sometimes:
choose specifc dCP,
e.g. 3p/2
C
(worst/best case)
dCP values
now stacked
for each q13
Sensitive
region as
function of
true q13 and
dCP
A
Simplifications:
Read: If
sin22q13=0.04,
we expect a
discovery for
20% of all
values of dCP
Sometimes:
Band for
risk wrt dCP D
Worst case q13 reach
“Typical” dCP:
CP fraction 50%
B
Best case q13 reach
E
F
G
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Experiment choice and
optimization (some thoughts)
Optimization of exps
 Small q13:
Optimize q13, MH,
and CPV discovery
reaches in q13 direction
 Large q13:
Optimize q13, MH,
and CPV discovery
reaches in (true) dCP
direction
Beta beam
B
Optimization
for large q13
T2KK
Optimization
for small q13
(3s, Dm312=0.0022 eV2)
 What defines “large q13”?
A Double Chooz, Day Bay, T2K, … discovery?
When?
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Timescale for q13 discovery?
 Assume:
Decision on future
experiments made
after some LHC
running and nextgeneration
experiments
 Two examples:
 ~ 2011: sin22q13 > 0.04?
 ~ 2015: sin22q13 > 0.01?
D
(Huber, Kopp, Lindner,
Rolinec, Winter, 2006)
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Large q13 strategy
 Assume that
Double Chooz
finds q13
 Minimum wish list
easy to define:
(arXiv:0804.4000; Sim. from hep-ph/0601266;
1.5 yr far det. + 1.5 yr both det.)
 5s independent confirmation of q13 > 0
 3s mass hierarchy determination for any (true) dCP
 3s CP violation determination for 80% (true) dCP
For any (true) q13 in 90% CL D-Chooz allowed range!
 What is the minimal effort (minimal cost) for that?
 NB: Such a minimum wish list is non-trivial for small q13
 NB: CP fraction 80% comes from comparison with IDS-NF baseline etc.
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Example: Minimal beta beam
(arXiv:0804.4000)
 Minimal effort =




One baseline only
Minimal g
Minimal luminosity
Any L (green-field!)
 Example: Optimize
L-g for fixed Lumi:
 g as large as 350 may
not even be
necessary!
More on beta beams: Mezzetto‘s talk!
Sensitivity for entire Double Chooz allowed range!
5yr x 1.1 1018 Ne and 5yr x 2.9 1018 He useful decays
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Small q13 strategy
 Assume that Double Chooz … do not find q13
 Minimum wish list:
 3s-5s discovery of q13 > 0
 3s mass hierarchy determination
 3s CP violation determination
For as small as possible (true) q13
 Two unknowns here:
 For what fraction of (true) dCP?
One has to make a choice (e.g. max. CP
violation, for 80% of all dCP, for 50%, …)
 How small q13 is actually good enough?
 Minimal effort is a matter of cost!
 Maybe the physics case will be defined
otherwise?
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Connection to high-E frontier?
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Optimal strategy vs. regional interests?
So far: purely conceptual …
… however, the optimal strategy depends on regional boundary conditions!
Talks:
Goodman (US)
Evans (MINOS)
Kurimoto (SciBooNE)
Talks:
Ronga (Gran Sasso)
Scott-Lavina (OPERA)
Sala (CNGS)
CERN-INO?
JHF-INO?
Talk: Goswami
Talks:
Kakuno (T2K)
Dufour (T2KK)
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Physics potential of the neutrino
factory: what can we expect?
International design study
(Geer, 1997; de Rujula, Gavela, Hernandez, 1998;
Cervera et al, 2000)
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Signal prop. sin 2q13
Contamination
Muons decay in straight sections of a storage ring
IDS-NF:
 Initiative from ~ 2007-2012
to present a design report,
schedule, cost estimate,
risk assessment for a
neutrino factory
 In Europe: Close
connection to „Euronus“
proposal
within the FP 07
 In the US: „Muon collider
task force“
ISS
Talks:
Long (IDS-NF)
Bonesini (R&D)
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IDS-NF baseline setup 1.0
 Two decay rings
 Em=25 GeV
 5x1020 useful
muon decays per
baseline
(both polarities!)
 Two baselines:
~4000 + 7500 km
 Two MIND,
50kt each
 Currently: MECC
at shorter baseline
(https://www.ids-nf.org/)
More by Ken Long
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Physics potential
 Excellent
q13, MH,
CPV
discovery
reaches
3s
B
B
B
(IDS-NF, 2007)
 About 10% full width error (3s) on log10 (sin22q13) for sin22q13 = 0.001
(Gandhi, Winter, hep-ph/0612158, Fig. 6)
 About 20-60 degree full width error (3s) on dCP for sin22q13 = 0.001
(Huber, Lindner, Winter, hep-ph/0412199, Fig. 7)
But what does that mean? Cabibbo angle-precision (qC ~ 13 deg.)!
Why is that relevant? Can be another feature of nontrivial QLC models:
E.g. from specific texture+QLC-type assumptions:
(F: model parameter)
(Niehage, Winter, 2008)
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Two-baseline optim. revisited
 Robust optimum
for
~ 4000 + 7500 km
C
 Optimization even
robust under nonstandard physics
(dashed curves)
C
(Kopp, Ota, Winter, 2008)
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Matter density measurement
 Assume that only one parameter
measured:
Constant reference
density rRef
or lower
mantle density rLM
True
d=0
(Minakata, Uchinami, 2007; Gandhi, Winter, 2007)
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MSW effect in Earth matter
 Solar term:
5s
C
Note that
i.e., effect (initially) increases
with baseline (D ~ L)!
MSW effect sensitivity even
for q13=0!
(hep-ph/0411309)
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Octant degeneracy
(Gandhi, Winter, 2007)
Similar performance
to Gold+Silver* @ 4000km
Meloni, arXiv:0802.0086
 4000 km alone: Problems
with degs for intermediate q13
 7200 km alone:
No sensitivity for small q13
 4000 km + 7200 km:
Good for all q13
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The unexpected!?
Neutrino osc. framework incomplete?
See also talk by D. Meloni
 Example: non-standard interactions (NSI) from effective
four-fermion interactions:
~ current bound
 Discovery potential for
NSI-CP violation in neutrino
propagation at the NF
Even if there is no CPV in
standard oscillations, we may
find CPV!
But what are the requirements
for a model to predict such
large NSI?
 Talk by T. Ota
(arXiv:0808.3583)
3s
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Help from other experiments?
 Physics scenario:
Double Chooz finds q13
and ~ a total of 100
muon tracks from
astrophysical sources
observed (ratio of muon tracks
to showers),
only m1 stable
on extragalatic distances
 Double Chooz
alone and this
information
could establish CPV
 Other sources of
information: Supernovae,
atmospheric, LHC, 0nbb,
...
Talks: Petcov, Schwetz, Sigl, …
(Maltoni, Winter, 2008)
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Outlook:
How to design the optimal experiment
Physics
Correlations+
Degeneracies
 Resolution strategies
Theory
 Performance indicators:
q13, CP violation, MH, …
New physics?
 Inclusive strategies
(more channels, etc.)
Future LBL experiment
Potitical
boundary
conditions
(e.g., Obama vs.
McCain)
Politics
Regional
interests
(e.g., DUSEL,
T2KK, …)
LHC
(e.g.,connection
to high-E frontier)
Same
measurement
by other
experiment
(e.g., MH from
supernova)
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