Transcript Physics potential of very long neutrino factory baselines

Neutrino Factory and Beta Beam
Experiment
NO-VE 2006
Venice, Italy
February 8, 2006
Walter Winter
Institute for Advanced Study, Princeton
Contents


Introduction
Neutrino factory
–
–
–
–
–

Basics
Correlation and degeneracy resolution
ISS study: Current status
Optimization
“New physics” tests and other oscillation physics
Beta beams
– Basics
– Optimization
– Comparison to neutrino factory

Summary
Feb. 8, 2006
NOVE 2006 - Walter Winter
2
Three-flavor oscillations: Requirements
Atmospheric
oscillation:
Amplitude: q23
Frequency: Dm312
Solar
oscillation:
Amplitude: q12
Frequency: Dm212
Subleading
effect: dCP
Coupling strength: q13

Neutrino oscillation parameters (1s):
Dm212 ~ 8.2 10-5 eV2
+- 5%
sin22q12 ~ 0.83 +- 5%
|Dm312| ~ (2 – 2.5) 10-3 eV2
sin22q23 ~ 1
+- 7%
sin22q13 < 0.14
Neutrino factory/
dCP = ?
Beta Beam if q13 small!
Mass hierarchy?
Feb. 8, 2006
NOVE 2006 - Walter Winter
Key to subleading
effects (CP violation,
mass hierarchy)
(see e.g. Bahcall et al, hep-ph/0406294;
Super-K, hep-ex/0501064;
CHOOZ+solar papers)
3
Timescales
This talk: beyond next ten years!
 Neutrino factory
 Medium to high g beta beam
But: Note that Beta Beams possible
on different g scales!

(from: FNAL Proton Driver Study)
Beta Beam? Depends on g!
Timescale: 2025?
Feb. 8, 2006
NOVE 2006 - Walter Winter
4
Neutrino factory



Ultimate “high precision” instrument!?
Muon decays in straight sections of storage ring
Technical challenges: Target power, muon
cooling, charge identification, maybe steep
decay tunnels
Decays
Target
p
p, K
Cooling
m-Accelerator
m
m
n
“Wrong sign”
“Right sign”
“Wrong sign”
“Right sign”
(from: CERN Yellow Report )
Feb. 8, 2006
(Geer, 1997; de Rujula, Gavela, Hernandez, 1998; Cervera et al, 2000)
NOVE 2006 - Walter Winter
5
Storage ring and “typical” params?

Goal: ~ 1021 useful muon decays/year. Two models:
“triangular”
“racetrack”
m+
or
(not to scale)
mm+

Operate two baselines in two
polarities successively:
4 years x 1021 m+ decays +
4 years x 1021 m- decays

m-
Operate one baseline in two
polarities simultaneously:
8 years x 5 1020 m+ decays +
8 years x 5 1020 m- decays
Other “typical” parameters (high-E neutrino factory):
Em = 50 GeV, L = 3,000 km (CP violation)
Detector: 50 kt magnetized iron calorimeter
(more ambitious: 100 kt, 10 years running time – ISS values)
Feb. 8, 2006
NOVE 2006 - Walter Winter
6
Appearance channels: nm ne
(Cervera et al. 2000; Freund, Huber, Lindner, 2000; Freund, 2001)

Complicated, but all interesting information there:
q13, dCP, mass hierarchy (via A)
Feb. 8, 2006
NOVE 2006 - Walter Winter
7
Correlations and degeneracies



Connected (green) or
disconnected (yellow)
degenerate solutions (at a
chosen CL) in parameter
space
Affect performance of
appearance measurements.
For example, q13 sensitivity
Discrete degeneracies: (also: Barger, Marfatia, Whisnant, 2001)
Intrinsic (d,q13)-degeneracy (Burguet-Castell et al, 2001)
sgn-degeneracy (Minakata, Nunokawa, 2001)
(q23,p/2-q23)-degeneracy (Fogli, Lisi, 1996)
Feb. 8, 2006
NOVE 2006 - Walter Winter
(Huber, Lindner, Winter, 2002)
8
More correlations: Matter density

For instance: Measure
dCP with high
precision for large q13
at L ~ 3 000 km
Matter density uncertainties in 3D models ~ 5%
(http://cfauvcs5.harvard.edu/lana/rem/mapview.htm)
5% matter density uncertainty in mantle
not acceptable for these measurements!
Has to be of the order of 1%
(Figure from Ohlsson, Winter, 2003;
see also: Koike, Sato, 1999; Jacobsson et al, 2001; Burguet-Castell
et al, 2001; Geller, Hara, 2001; Shan, Young, Zhang, 2001; Fogli,
Lettera, Lisi, 2001; Shan, Zhang, 2002; Huber, Lindner, Winter,
2002; Ota, Sato, 2002; Shan et al, 2003; Kozlovskaya , Peltoniemi,
Sarkamo, 2003; others)
Feb. 8, 2006
NOVE 2006 - Walter Winter
9
Feb. 8, 2006
NOVE 2006 - Walter Winter
10
Purpose:
Looks like result
Purpose:
Risk minimization
– Allowed region in d-q13-plane
Identify how much parameter space remains for specific
hypotheses of simulated values
– Sensitivity to max. CP violation p/2 or 3p/2
Can CP violation be detected for the hypothesis of max.
CP violation?
– Sensitivity to “any” CP violation
For what fraction of CP violating values can CP violation
be detected? (CP fraction plots!)
– Precision of d ?
How precisely can one measure d? (only defined in the
high precision limit, since d cyclic; also: not Gaussian!)
– CP coverage
How precisely can one measure d or what fraction of the
parameter space can be excluded?
True values:
Few examples

Matter of definition and hypothesis
What indicator to use depends on purpose!
Examples (dCP only!)
True values:
Complete relevant space

Level of condensation, computation time
NF measurements: Performance indicators
NF measurements: Example dCP coverage
Define: CP coverage = Fraction of all fit values of d
which fit a chosen true d: 0 < CP coverage <= 360o
CP scaling
CP pattern
Degeneracy problem
even bigger than
for max. CP violation!


(Dc2 = 9, 4, 1; dashed: no degs)
(Fig. from Huber, Lindner, Winter, hep-ph/0412199)

True values of d and q13 affect topology! Degeneracies!
But: Degeneracies not everywhere in param. space important
Feb. 8, 2006
NOVE 2006 - Walter Winter
11
NF-Strategies to resolve degeneracies
… depend on sin22q13!

Combine with superbeam upgrade
(sin22q13 > 10-3) (Burguet-Castell et al, 2002)
Intrinsic degeneracy
disappears for better
energy threshold!
sin22q13=0.001

Combine with “silver channels” ne -> nt
(sin22q13 > 10-3 ?)
(Donini, Meloni, Migliozzi, 2002; Autiero et al, 2004)

Better detectors: Higher energy
resolution, higher efficiencies at
low energies (CID!) (sin22q13 > ?)
(Will be important aspect in ISS study!)

(Fig. from Huber, Lindner, Winter, 2002)
Second NF baseline: “Magic baseline” (sin22q13 > 10-4)
(Lipari, 2000; Burguet-Castell et al, 2001; Barger, Mafatia, Whisnant, 2002; Huber, Winter, 2003;
others)

Other possibilities?
Feb. 8, 2006
NOVE 2006 - Walter Winter
12
Example: “Magic baseline”



Idea:
Yellow term = 0 independent
of E, oscillation parameters
Purpose:
“Clean” measurement of q13 and mass hierarchy
Drawback: No dCP measurement at magic baseline
 combine with shorter baseline, such as L=3 000 km

q13-range: 10-4 < sin22q13 < 10-2,
where most problems with degeneracies are present
Feb. 8, 2006
NOVE 2006 - Walter Winter
13
Magic baseline: q13 sensitivity
Use two-baseline space (L1,L2) with (25kt, 25kt) and compute q13
sensitivity including correlations and degeneracies:
No CP violation
measurement there!
dCP
Optimal
performance for
all quantities:
Animation in
q13-dCP-space:
Unstable: Disappears
for different parameter
values
Feb. 8, 2006
(Huber, Winter, 2003)
NOVE 2006 - Walter Winter
sin22q13
14
CP coverage and “real synergies”
Any “extra” gain beyond a simple addition of statistics



3 000 km + 7 500 km
versus all detector mass at
3 000 km (2L)
Magic baseline allows a
risk-minimized
measurement (unknown d)
“Staged neutrino factory”:
Option to add magic
baseline later if in “bad”
quadrants?
(Huber, Lindner, Winter, 2004)
Feb. 8, 2006
One baseline enough Two baselines necessary
NOVE 2006 - Walter Winter
15
ISS study
International scoping study of a future neutrino factory and super-beam facility



Establish physics case for a facility (accelerator
complex and detection systems) for a future longbaseline neutrino oscillation program
“Define” requirements: Muon energy, baselines,
channels, …
Three working groups: Physics, accelerator, detector
(Dornan; Blondel, Nagashima, Zisman; King, Long, Roberts, Yasuda; many others)



Next plenary meeting: April 24-29, 2006 at RAL (UK)
Final written report: September 2006?
More information:
http://www.hep.ph.ic.ac.uk/iss/
Feb. 8, 2006
NOVE 2006 - Walter Winter
16
ISS issues: Physics cases?
(Huber/POFPA report)

Examples (q13 only):
1)
Large q13: sin22q13 > 0.01
(Physics case for NuFact at all?
vs. Superbeams?)
2)
Small q13: 10-4 < sin22q13 < 10-2
3)
“Zero” q13: sin22q13 << 10-4
3
(NuFact’s “golden age”?)
2
1
(What physics can be done?
What does that mean?)

Maybe: Only build NF if T2K,
Double Chooz etc. do not see a
signal?
Feb. 8, 2006
Neutrino factory!
(or higher gamma beta beam)
NOVE 2006 - Walter Winter
Beta beam?
SuperbeamUpgrade?
n-factory?
17
ISS issues: Better detector?
Better threshold (low-E efficiencies) helps
for all measurements!
 Better energy resolution helps somewhat

(Huber,
Lindner,
Rolinec,
Winter,
to appear)



Better threshold (low-E efficiencies) helps for all measurements
Better energy resolution helps somewhat
Better detector may be key component in large q13 discussion
Feb. 8, 2006
NOVE 2006 - Walter Winter
18
Physics case for q13=0?
Establish MSW effect for q13=0
by solar oscillation (appearance prob.)
Determine mass hierarchy for q13=0
(disappearance probability)
L > 5,500 km
L ~ 6,000 km
(Winter, 2004)
(de Gouvea, Jenkins, Kayser, 2005;
de Gouvea, Winter, 2005)
Very long (>> 3,000 km) baseline important component of any such program!
Theoretical: q13=0 would be an important indicator for some symmetry!
Feb. 8, 2006
NOVE 2006 - Walter Winter
19
Optimization of a neutrino factory



Example: q13 sensitivity
relative to minimum in
each plot (3s)
Important result:
Since muon energy ~ $
40 GeV enough?!
Threshold effects:
(Huber, Lindner, Rolinec, Winter, to appear;
also: Freund, Huber, Lindner, 2001)
Feb. 8, 2006
NOVE 2006 - Walter Winter
20
Disappearance channels

Disappearance information
important to reduce errors on
leading parameters
sin22q13 precision
(see e.g. Donini, Fernandez-Martinez, Rigolin, 2005;
Donini, Fernandez-Martinez, Meloni, Rigolin, 2005)
(Fig. from Huber, Lindner, Winter, 2002)

sin22q13 = 0

Idea: Use data sample
without charge
identification for
disappearance, i.e.,
add right and wrong
sign muon events
Better efficiencies!
(de Gouvea, Winter, 2005; Huber, Lindner, Rolinec, Winter, to appear)
Feb. 8, 2006
NOVE 2006 - Walter Winter
21
Beyond three-flavor oscillations?
Test unitarity and small ad-mixtures of “new physics” by:
1. nt detection Pee+Pem+Pet = 1? (Donini, Meloni, Migliozzi, 2002; Autiero et al, 2004)
2. Neutral currents (hard, but harder than 1.?) (Barger, Geer, Whisnant, 2004)
3. Construction of unitarity triangles? (Xing, Zhang, 2004/2005)
4. Spectral signature for probability-level effects
Example:
Damping
effects
Characteristic
enhancement/
depletion in certain
regions of spectrum
while oscillation
nodes remain
unchanged
(Blennow,
Ohlsson,
Winter,
hep-ph/0502147)
5.
More complicated: Hamiltonian-level effects:
Spectrum shifts
(e.g., Blennow, Ohlsson, Winter, hep-ph/0508175)
Example: Oscillation-NSI confusion theorem
(Huber, Schwetz, Valle, 2002)
Feb. 8, 2006
NOVE 2006 - Walter Winter
Search for “new physics”
motivated by many
theoretical effects, such
as neutrino decay, decoherence,
search for steriles, LFV,
extra dimenstions, …
22
Other physics: Geophysics?
Example: Measure inner core density rIC
sin22q13=0.01
JHF
BNL
CERN
(Winter, 2005)



Inner
Per cent level precision not unrealistic
core
Survives unknown oscillation parameters
shadow
More recent discussions: Discriminate seismically degenerate
geophysics models in mantle, test plum hypothesis etc.?
Feb. 8, 2006
NOVE 2006 - Walter Winter
23
Beta beam



Compared to superbeam: no intrinsic beam BG limiting the
sin22q13 sensitivity to > 10-3
Compared to neutrino factory: no charge identification required
In principle, very interesting alternative concept!
Key figure (any beta beam):
Useful ion decays/year?
 “Standard values”:
3 1018 6He decays/year
1 1018 18Ne decays/year
 Can these be achieved?
 Typical gamma ~ 100 – 150
(for CERN SPS)
6
6

2 He3 Li e n

18
10
Ne189Fe en
(Zucchelli, 2002)
(CERN layout; Bouchez, Lindroos, Mezzetto, 2003; Lindroos, 2003; Mezzetto, 2003; Autin et al, 2003)
Feb. 8, 2006
NOVE 2006 - Walter Winter
24
From very low to high gamma

“Very low” gamma (g<150?)
- Alternative to superbeam?
- Originally designed for CERN (SPS)
- Water Cherenkov detector
Gamma determines neutrino energy
and therefore detector technology!
(see before; also: Volpe, 2003)

“Low” gamma (150<g<300-350?)
(Fig. from Huber, Lindner,
Rolinec, Winter, 2005)
- Alternative to superbeam!
- Possible at upgraded SPS?
- Water Cherenkov detector
(Burguet-Castell et al, 2004+2005; Huber et al, 2005)

“Medium” gamma (300-350<g<800?)
- Physics potential compared to effort?
- Requires large accelerator (Tevatron-size)
- Water Cherenkov detector or TASD or?
(Burguet-Castell et al, 2004; Huber et al, 2005)

“High” gamma (g>800?)
- Alternative to neutrino factory?
- Requires very large accelerator (LHC-size)
- Detector technology other than water (TASD?)
(Burguet-Castell et al, 2004; Huber et al, 2005; Agarwalla et al, 2005)
(for NOvA-like detector!)
25
Optimization of a beta beam

Baseline optimization depends on goals and gamma:
(Fig. from Huber, Lindner, Rolinec, Winter, 2005)


For lower gamma: Second osc. max. useful to resolve degs
Neutrino/antineutrino running: Have at least 10-20% of
(for other degeneracy studies: see, e.g. Donini,
originally proposed flux!
Fernandez-Martinez, Rigolin, 2004; Donini,
Fernandez-Martinez, Migliozzi, Rigolin, 2004)
Feb. 8, 2006
NOVE 2006 - Walter Winter
26
Beta beam vs. Superbeam vs. NuFact?



Lower g:
Can easily compete
with superbeam
upgrades if properly
optimized
Higher g:
At least theoretically
competitive to a
neutrino factory
Challenges:
- Can fluxes be reached?
- Compare completely
optimized accelerator
strategies?
(Fig. from Huber, Lindner, Rolinec, Winter, 2005)
Feb. 8, 2006
NOVE 2006 - Walter Winter
27
Beta beam in ISS study
(from talk given by Elena Couce on Jan. 24 at KEK)



Use of Water Cherenkov detector
New efficiency and
BG matrices for migration
High gamma beta beam
best alternative (even “low flux”)
Two
different
options!
Feb. 8, 2006
NOVE 2006 - Walter Winter
28
Summary: Key questions


What if q13 is large?
Do we need a NuFact/
Beta beam program
in this case?
NuFact:
– Feasibility of muon cooling,
target power etc. (MICE, …)
– Flexible storage ring concept for different physics scenarios?
– Detector: Is there space for improvement?

Beta beam:
– Feasibility? Competitiveness? Price tag?
 Probably depends on gamma!
– Stored ions?
 Answers from EURISOL design study? http://www.eurisol.org/
Feb. 8, 2006
NOVE 2006 - Walter Winter
29