Transcript Long baseline neutrino oscillations: Theoretical aspects

Phenomenology of future LBL
experiments … and the context with Euron WP6
IDS-NF + Euron plenary meeting
at CERN
March 25, 2009
Walter Winter
Universität Würzburg
Contents
 Introduction to LBL phenomenology
 Status of
 Neutrino factory
 Superbeams
 Beta beams
 Current Euron/IDS-NF issues
This talk:
Only standard
oscillation
physics
 Performance indicators
 Benchmark setups
 Optimization/decision: Large versus small q13
 Conclusions
2
Long baseline phenomenology
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: maybe in low-E NF)
(see e.g. ISS physics working group report)
 „Discovery“: nm  nt (OPERA, NF?)
(e.g. Fernandez-Martinez et al, 2007; Donini et al, 2008)
Neutral currents for new physics
(e.g., Barger, Geer, Whisnant, 2004; MINOS, 2008)
4
Appearance channels




Antineutrinos:
Magic baseline:
Silver:
Superbeams, Plat.:
(Cervera et al. 2000; Freund, Huber, Lindner, 2000; Huber, Winter, 2003; Akhmedov et al, 2004)
5
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)
6
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
Reactor, atmospheric,
astrophysical, …
(many many authors, see e.g. ISS physics WG report)
7
Status of the neutrino factory
Neutrino factory – IDS-NF
(Geer, 1997; de Rujula, Gavela, Hernandez, 1998;
Cervera et al, 2000)
2
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
9
Physics potential
 Excellent q13, MH, CPV discovery
reaches
(IDS-NF, 2008)
 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, arXiv:0804.1546)
10
Low energy neutrino factory
 „Low cost“ version of a neutrino factory
for moderately large q13: Em ~ 4.12 GeV
 Possible through magnetized
TASD with low threshold
(Geer, Mena, Pascoli, hep-ph/0701258; Bross et al, arXiv:0708.3889)
11
On near detectors@IDS-NF
 Define near detectors including source/detector geometry:
 Near detector limit:
Beam smaller than detector
 Far detector limit:
Spectrum similar to FD
 Systematics
 X-Section (shape) errors (30%)
 Flux normalization errors (2.5%)
 BG normalization errors (20%)
~ND limit
~FD limit
(Tang, Winter, arXiv:0903.3039)
12
ND: Main results
 Need two near detectors,
especially for leading
atmospheric parameters
 Flux monitoring
important for CPV (large
q13)
 Near detectors not
relevant for q13 discovery,
MH
 Systematical errors
cancel if two neutrino
factory baselines (even
without ND)
30% XSec-errors, uncorrelated
among all bins
Use near detectors
(Tang, Winter, arXiv:0903.3039)
13
Impact of ND+new systematics
CP violation, 3s
IDS-NF systematics
too conservative?
(Tang, Winter, arXiv:0903.3039)
14
Low-E versus high-E NuFact
 High-E reference: IDS-NF baseline 1.0
 Low-E reference: Bross et al, arXiv:0708.3889, 1023 decays*kt,
2% systematics errors (flux norm, BGs)
 High-E NuFact one to two orders of magnitude in q13 better
(Tang, Winter, arXiv:0903.3039)
15
NF: Status and outlook
 Characteristics:
 Truly international effort
 Green-field setup (no specific site)
 High-E NuFact: Benchmark setup defined
 Will evolve over time
 Examples: MECC, Detector masses of far detectors
 Open issues:
„Low cost“ alternative? Benchmark setup for that?
 Euron relationship: Results shared between IDSNF (physics) and Euron; Funding from Euron
16
Status of superbeams
Beam/Superbeam setups
Characteristics: Possible projects depend on regional
boundary conditions (e.g., geography, accelerator infrastructure)
Setups:
MINOS
NOnA (+ upgrades)
WBB FNAL-DUSEL
…
Setups:
CNGS
CERN SPL-Frejus
…
Setups:
T2K
T2HK
T2KK
…
18
Superbeam upgrades: Examples
120 GeV protons
discovery
Nominal exposure
 Exposure L:
Detector mass [Mt] x
Target power [MW] x
Running time [107s]
 Bands: variation of
systematical errors:
2%-5%-10%
 „Typical“ dCP, 3s
(Barger, Huber, Marfatia, Winter, hep-ph/0610301, hep-ph/0703029)
19
Luminosity scalings
 If q13 found by
next generation:
 WBB and T2KK
can measure CPV,
MH
 NuMI requires
Lumi-upgrade
(ProjectX?)
 Systematics
impact least for
WBB; best physics
concept?
MH for sin22q13 > 0.003
20
On-axis versus off-axis
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*
(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???
21
European plan: CERN-MEMPHYS
 L=130 km: CERN-Frejus
 Interesting in combination
with beta beam: Use T-inverted channels
(ne  nm and nm  ne) to measure CPV
 Problem: MH sensitivity, only
comparable to T2HK
2s
LBL+ATM
Concerns of WP6 communicated
to Euron CB in Feb 2008:
„[...] It is well known that this setup has good
possibilities to observe CP violation, however,
due to the short baseline there will be no chance
to determine the mass hierarchy. We believe that
this is a very important measurement for a future
neutrino facility, and will be one of the comparison
criteria to be defined within this study.
WBB FNAL-DUSEL (average)
(Campagne, Maltoni, Mezzetto,
Schwetz, hep-ph/0603172)
We want to point out very clearly that restricting the SB study only to the CERN-Frejus
setup excludes this measurement from the very beginning. […]”
22
SB: Status and outlook
 Characteristics:
 Projects driven by regional interests/boundary
conditions
 Projects attached to existing accelerator sites (mid
term perspective)
 Benchmark setups:
 Partly defined (such as baselines, detectors etc)
 Fuzzy assumptions on proton plans, running times, …
(benchmark comparison difficult!)
 Relationship to Euron: Only CERN-Frejus setup
studied within Euron WP2
 Concern raised by some WP6 members:
European setup maybe „dead end“?
23
Status of beta beams
Original „benchmark“ setup!?
(CERN layout; Bouchez, Lindroos, Mezzetto, 2003; Lindroos, 2003; Mezzetto, 2003; Autin et al, 2003)
(Zucchelli, 2002)
6
2
 Key figure (any beta
beam):
Useful ion decays/year?
 Often used “standard
values”:
3 1018 6He decays/year
1 1018 18Ne decays/year
 Typical g ~ 100 – 150
He Li e n
(for CERN SPS)
18
10
6
3


Ne18
9 Fe e n
More recent key modifications:
 Higher g (Burguet-Castell et al, hep-ph/0312068)
 Different isotope pairs leading to
higher neutrino energies (same g)
(C. Rubbia, et al, 2006)
(http://ie.lbl.gov/toi)
25
Current status: A variety of ideas
 “Classical” beta beams:
 “Medium” gamma options (150 < g < ~350)
- Alternative to superbeam! Possible at SPS (+ upgrades)
- Usually: Water Cherenkov detector (for Ne/He)
(Burguet-Castell et al, 2003+2005; Huber et al, 2005; Donini, Fernandez-Martinez, 2006;
Coloma et al, 2007; Winter, 2008)
 “High” gamma options (g >> 350)
- Require large accelerator (Tevatron or LHC-size)
- Water Cherenkov detector or TASD or MID? (dep. on g, isotopes)
(Burguet-Castell et al, 2003; Huber et al, 2005; Agarwalla et al, 2005, 2006, 2007, 2008, 2008;
Donini et al, 2006; Meloni et al, 2008)
 Hybrids:
 Beta beam + superbeam
(CERN-Frejus: see before; Fermilab: see Jansson et al, 2007)
 “Isotope cocktail” beta beams (alternating ions)
(Donini, Fernandez-Martinez, 2006)
 Classical beta beam + Electron capture beam
(Bernabeu et al, 2009)
 …
26
Stand-alone European version?





CERN-Gran Sasso or Boulby?
Example: CERN-Boulby, L=1050 km
g=450 (SPS upgrade), 18Ne only!
Red: 1021 usef. ions x kt x yr
Blue: 5x2021 usef. ions x kt x yr
Mass
hierarchy
99% CL
99% CL
Problem:
Antineutrino channel missing!
(degs only partially resolved by spectrum)
More later …
(Meloni, Mena, Orme, Palomares-Ruiz, Pascoli, arXiv:0802.0255)
27
BB: Status and outlook
 Characteristics:
 Mostly European effort (so far)
 Partly green-field, mostly CERN-based
 Benchmark setup:
 Often-used: SPS-based setup, sort of „benchmark“ in
the literature (e.g. for useful number of ion decays)
 Not up-to-date anymore wrt isotopes, g, useful ion
decays etc
 Define new benchmark with the necessary
requirements for WP4?
 Relationship to Euron:
Studied within WP4 (mostly source aspects)
28
Current Euron physics issues
(some thoughts)
Performance indicators
 Many performance indicators used in literature
 What is the best way to present?
 Fair comparison of whole parameter space or comparison at specific
benchmark points?
 WP6 will have to look into this (Pilar)
Example:
q13 discovery
vs q13 sensitivity
(Huber, Lindner,
Schwetz, Winter,
in prep.)
Warning: If particular
dCP chosen,
any answer can
be obtained!
30
Benchmark setups: Status
 Do we need these? At the end, for a physics comparison,
probably …
 Can be used to define requirements for reasonable physics
output (see, e.g., IDS-NF)
 Maybe: More aggressive
versus minimal version
Example: ISS Plot
 Neutrino factory:
 Exists for high-E version
 Not yet for low cost version
 Superbeam:
 Minimal version exists (apart
from specific numbers)
 More aggressive: Not defined
 Beta beam:
 Minimal version exists (apart
from specific numbers)
 More aggressive: Not defined
(ISS, arXiv:0710.4947)
31
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
~ Precision!
Beta beam
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!
32
Large q13 strategy
 Assume that we
know q13
(Ex: Double Chooz)
 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
~ Cabibbo-angle precision as a benchmark!
For any (true) q13 in 90% CL D-Chooz allowed range!
(use available knowledge on q13 and risk-minimize)
 What is the minimal effort (minimal cost) for that?
 Use resources wisely!
33
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!
Sensitivity for entire Double Chooz allowed range!
5yr x 1.1 1018 Ne and 5yr x 2.9 1018 He useful decays
34
Minimal beta beam at the CERNSPS? (g fixed to maximum at SPS)
(500 kt)
CERN-Boulby
CERN-Boulby
CERN-LNGS
CERN-LNGS
(arXiv:0809.3890)
Conclusions:
- CERN-Boulby or CERN-LNGS might be OK at current SPS if ~ 5 times
more isotope decays than original benchmark (production ring?)
- CERN-Frejus has too short baseline for stand-alone beta beam
35
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?
36
Connection to high-E frontier?
37
Conclusions
 Current status:
 Neutrino factory:
 Strong collaboration with IDS-NF
 High-E benchmark setup defined
 „Low cost“ version further studied
 Superbeams:
 CERN-Frejus anticipated as benchmark
 Has too little MH sensitivity, even if combined with atm. data
(Issues: low energy, short baseline)
 Beta beams:
 SPS-based benchmark often used in literature
 Probably not sufficient: Define more aggressive version with higher g
or more isotope decays (production ring)?
 Next steps?




Discuss performance indicators
Discuss if benchmarks needed for WP6
Connection to global perspective?
…
38
Backup
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
40
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/)
41
Two-baseline optim. revisited
 Robust optimum
for
~ 4000 + 7500 km
 Optimization even
robust under nonstandard physics
(dashed curves)
(Kopp, Ota, Winter, 2008)
42
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)
43
Example: CPV discovery
… in (true) sin22q13 and dCP
Best performance
close to max.
CPV (dCP = p/2 or
Sensitive
region as a
function of true
q13 and dCP
3p/2)
dCP values
now stacked
for each q13
No CPV discovery if
dCP too close to 0 or p
3s
Read: If
sin22q13=10-3,
we
expect a
discovery for 80%
of all values of dCP
No CPV discovery for
all values of dCP
Cabibbo-angle
precision for dCP
~ 85%!
Fraction 80% (3s)
corresponds to
Cabibbo-angle
precision at 2s
BENCHMARK!
44
Luminosity scaling for fixed L
 But: If LSF >= 5:
g can be lower for
(B,Li) than for
(Ne,He), because
MH measurement
dominates there
(requires energy!)
(500kt)
(100kt)
(Winter, arXiv:0804.4000)
 What is the
minimal LSF x g?
 (Ne,He):
LSF = 1 possible
(B,Li):
LSF = 1 not
sufficient
45
Minimal g beta beam
(Winter, arXiv:0804.4000)
46