Transcript Future Neutrino Oscillation Experiments « physics »: status and priorities NUFACT05 -- physics

Future
Neutrino Oscillation Experiments
« physics »: status and priorities
NUFACT05 -- physics
Alain Blondel
The BIG picture
1. We have observed neutrino transmutation
this means neutrinos have mass.
The most likely process for transmutation is quantum oscillations.
2. 3 families lead to three masses, three mixing angles and one phase
this limits the number of parameters and predicts leptonic CP violation !!!.
AIMS
1.
precise determination of parameters
(NB: nobody really knows how to predict them, especially the phase
are there physics arguments?
2. verification of global picture
-- oscillation pattern
-- unitarity (what would it mean to observe violation of it?)
NUFACT05 -- physics
Alain Blondel
The tree
I believe it is important to have
a « main objective » (tree)
« Important objectives » (branches)
and « by-products » (leaves)
I have to confess the following pattern of mind:
Main objective: Observe and study CP and T violation, determine mass hierarchy
Important objectives: unambiguous precision measurements of mixing angles
and mass differences,lepton flavour violation with muons
by-products: precision short baseline neutrino physics, unitarity tests,
nuclear physics, muon collider preparation, muon EDM
can we make one facility that will do all of this?
or do we prefer an approach where these pieces will be produced one at a time by
individual dedicated experiments?
NUFACT05 -- physics
Alain Blondel
An ambitious neutrino programme is a distinct possibility,
but it must be well prepared to have a good proposal in time
for the big decision period in 2010 (Funding window: 2011-2020)
Avenues identified as promising
a) Superbeam alone + large detector(s) (e.g. T2HK, NOvA)
a) SuperBeam + Beta-Beam + Megaton detector (SB+BB+MD) Fréjus
b) Neutrino Factory (NuFact) + magnetic detector (40kton)+…
The physics abilities of the neutrino factory are superior
but….. « what is the realistic time scale? »
(Hardware) cost estimate of a neutrino factory ~1B€ + detectors.
This needs to be verifed and ascertained on a localized scenario (CERN,
RAL…) and accounting.
The cost of a (BB+SB+MD) is not very different
Cost/physics performance/feasibility comparison needed
 ‘scoping study’
NUFACT05 -- physics
Alain Blondel
The neutrino mixing matrix:
3 angles and a phase d
n3
Dm223= 2 10-3eV2
n2
n1
Dm212= 8 10-5 eV2
OR?
n2
n1
23 (atmospheric) =
450 ,
12 (solar) =
320 ,
13 (Chooz) <
130
n3
Dm212= 8 10-5 eV2
Dm223= 2 10-3eV2
Unknown or poorly known
even after approved program:
2
13 , phase d , sign of Dm13
NUFACT05 -- physics
Alain Blondel
CP violation
P(nenm) - P(nenm)
P(nenm) + P(nenm)
= ACP a
sind sin (Dm212 L/4E) sin 12
sin13 + solar term…
… need large values of sin 12, Dm212 (LMA) but *not* large sin213
… need APPEARANCE … P(nene) is time reversal symmetric (reactor ns do not work)
… can be large (30%) for suppressed channel (one small angle vs two large)
at wavelength at which ‘solar’ = ‘atmospheric’ and for nenm , nt
… asymmetry is opposite for nenm and nent
P(nenm) = ¦A¦2+¦S¦2 + 2 A S sin d
P(nenm) = ¦A¦2+¦S¦2 - 2 A S sin d
NUFACT05 -- physics
Alain Blondel
T asymmetry for sin d = 1
!
asymmetry is
a few %
and requires
excellent
flux normalization
(neutrino fact., beta beam
or
off axis beam with
neutrino factory
JHFII-HK
JHFI-SK
not-too-near
near detector)
NOTEs:
1. sensitivity is more or less
independent of 13 down to
max. asymmetry point
2. This is at first maximum!
Sensitivity at low values
of 13 is better for short
baselines, sensitivity at
large values of 13 is
better for longer baselines
(2d max or 3d max.)
0.10
0.30
10
30
3.sign of asymmetry changes
with max. number.
NUFACT05 -- physics
Alain Blondel
90
Mezzetto
NUFACT05 -- physics
Alain Blondel
T2K
Phase II:
4 MW upgrade
Phase II
HK: 1000 kt
SK: 22.5 kt
Kamioka
J-PARC
JPARC-n ~0.6GeV n
beam 0.75 MW 50 GeV PS
(2008 )
K2K ~1.2 GeV n beam
0.01 MW 12 GeV PS
(1999 2005)
NUFACT05 -- physics
Alain Blondel
NUFACT05 -- physics
Alain Blondel
CERN-SPL-based Neutrino SUPERBEAM
300 MeV n m Neutrinos
small contamination
from ne (no K at 2 GeV!)
target!
Fréjus underground lab.
A large underground water Cherenkov (400 kton) UNO/HyperK
or/and a large L.Arg detector.
also : proton decay search, supernovae events solar and
atmospheric neutrinos. Performance similar to J-PARC II
There is a window of opportunity for digging the cavern
stating in 2009 (safety tunnel in Frejus)
NUFACT05 -- physics
Alain Blondel
CERN: b-beam baseline scenario
neutrinos of Emax=~600MeV
n ,n
Nuclear
Physics
SPL
target!
Decay ring
B=5T
Decay
ISOL target
& Ion source
Lss = 2500 m
Ring
SPS
ECR
Cyclotrons,
linac or FFAG
Rapid
cycling
synchrotron
Stacking!
PS
Same detectors as Superbeam !
6
2
He + +  36Li + + + n e e 
18
10
Ne 
18
+
Alain Blondel
9
e
NUFACT05 -- physics
Fn e
Beta-beam at FNAL
Winter (IAS Princeton)
CERN
FNAL
gmax = gmaxproton/3
for 6He
fault of this one has to
buy a new TeV
acccelerator.
NUFACT05 -- physics
Alain Blondel
Combination of beta beam with low energy super beam
combines CP and T violation tests
ne  nm (b+) (T)
nm  ne (p+)
(CP)
ne  nm (b-) (T)
nm  ne (p-)
NUFACT05 -- physics
Alain Blondel
EC: A monochromatic neutrino beam
Electron Capture:
T1/2
BRn
EC/n
b
I EC
Tb
*
3.1 m
1
0.96
Dy 150Tb*
7.2 m
0.64
Tm2- 152ET*
8.0 s
Ho2- 150Dy*
72 s
Decay
148
Dy
148
150
152
150
N+e-  N’+ne
B(GT)
EGR
0.96
0.46
1
1
1
0.45
1
0.77
GR
Burget et al
DEn
QEC
En
620
2682
2062
0.32
397
1794
1397
0.50
0.48
4300
520
8700
4400
520
0.56
0.25
4400
400
7400
3000
400
NUFACT05 -- physics
Alain Blondel
Superbeam+Betabeam+Megaton option
1.
What is the importance of the superbeam in this scheme?
T violation?
increased sensitivity?
have a (known) source of muon neutrinos for reference?
2. At which neutrino energy can one begin to use the event energy distribution?
Fermi motion and resolution issues.
What is the impact of muon Cherenkov threshold?
3. What is the best distance from the source? What is the effect of changing the
beta-beam and superbeam energy? (event rates, backgrounds, ability to use dN/dEn )
Baseline site (Fréjus lab) is clearly not the optimal distance. Alternatives?
Should energy remain adjustable after the distance choice?
4, what is the relationship between beta-beam energy vs intensity?
5. What is really the cost of the detector?
what PM coverage is needed as function of energy and distance?
NB superbeam requires 4 MW proton driver,
beta-beam claim to be able to live with 200 kW!
NUFACT05 -- physics
Alain Blondel
-- Neutrino Factory -- CERN layout --
cooling!
1016p/
target!
s
acceleration!
1.2 1014 m/s =1.2 1021 m/yr
0.9 1021 m/yr
3 1020 ne/yr
3 1020 nm/yr
m+  e+ ne
oscillates
ne  nm
interacts giving m
WRONG SIGN MUON
_
nm
interacts
giving m+
Golden Channel
also (unique!) ne NUFACT05
 nt Silver
channel
-- physics
Alain Blondel
Questions for Neutrino Factory experiments(  very few studies in the last 2 years)
1.
Do we REALLY NEED TWO far locations at two different distances?
2.
3000 km  1st osc. max at 6 GeV and 2d max at 2 GeV.
Muon momentum cut at 4 GeV cuts 2d max info. Can this be improved?
3.
Can we eliminate all degenracies by combination of energy distribution and analysis
of different channels (tau, muon, electron, both signs, NC…)
4.
what are the systematics on flux control? (CERN YR claims 10-3)
NUFACT05
physics
Alain Blondel
5. optimal muon ENERGY? Cost of study II was 1500M$
+ --400M$*E/20
NB: This works just as well
INO ~7000 km (Magic distance)
NUFACT05 -- physics
Alain Blondel
Towards a comparison of performances on equal footing
CP violation example
P(nenm) - P(nenm)
P(nenm) + P(nenm)
= ACP a
sind sin (Dm212 L/4E) sin 12
sin13 + solar term…
ne diff. cross-section*flux
to know nm and nm diff. cross-section and detection
Near detector should give
BUT:need
efficiency
with small (relative) systematic errors.
interchange role of
ne
and
nm for superbeam
in case of beta-beam one will need a superbeam at the same energy. Will it be
possible to measure the required cross sections with the required accuracy
at low energies with a WBB?
What is the role of the difference in mass between electron and muons?
how well can we predict it?
In case of sub-GeV superbeam alone how canNUFACT05
one deal--with
this?Alain Blondel
physics
Zeller
ds/dn O(e,e, nEeEe’Enegy transfer (GeV)
Ee=700-1200 MeV
These are
for electron
beam.
errors are ~5-10%
but what happens
when a muon mass
is involved?
Blue: Fermi-gas
Green: SP
Red: SP+FSI
QE
D
NUFACT05 -- physics
Alain Blondel
Neutrino fluxes m+ -> e+ ne nm
nm/n e ratio reversed by switching m+/ m
ne nm spectra are different
No high energy tail.
Very well known flux (10-3)
-- E&sE calibration from muon spin precession
-- angular divergence: small effect if  < 0.2/g,
-- absolute flux measured from muon current
or by nm e -> m ne in near expt.
-- in triangle ring,
muon polarization precesses and averages out
(preferred, -> calib of energy, energy spread)
Similar comments apply to beta beam, except spin 0
 Energy and energy spread have to be obtained
from the properties of the storage ring
(Trajectories, RF volts and frequency, etc…)
m polarization controls ne flux:
m+ -X> ne
NUFACT05 -- physics
in forward direction
Alain Blondel
A discussion is necessary to establish reasonable systematic errors
in measuring the CP or T asymmetry
this discussion should include the following questions:
1.
what kind of near detector will be needed?
2. how does one measure the cross-section*efficiency of the appearance
channel in a beam with only one flavor? (superbeam or beta-beam alone)
my guess: these issues will be quite serious at low energies (E ~ few mm )
and gradually become easier at high Energies.
Neutrino factory provides all channels in the same beam line/detector
NUFACT05 -- physics
Alain Blondel
Degeneracies
Stephano Rigolin:
P. Huber’s beautiful plots assume: 4 GeV threshold, only golden channel.
 Experimenters need to provide characteristics of tau detectors and think about
efficiency for wrong sign muons at low energies.
NUFACT05 -- physics
Alain Blondel
range at 1.5 GeV is 1.5 meters
what is the sign confusion at that
momentum?
typical energy resolution
ïs 0.4 GeV at 1.5 GeV
NUFACT05 -- physics
Alain Blondel
NUFACT05 -- physics
Alain Blondel
systematics……………………………………degeneracies
. correlations
approval date:
~NOvA +PD
bbeam + SPL3.5 SB+Mton
Lindner et al
newer plot should come out of NUFACT05 and scoping study
NUFACT05 -- physics
Alain Blondel
What happens to this at high 13 if
-- two baselines are considered and
-- a threshold of 1.5 GeV for wrong sign muons is imposed on the 3000 km det
-- and there is a 4kton tau detector at the 3000 km station?
NUFACT05 -- physics
Alain Blondel
m+
Thoughts for muon targets in neutrino factory complex
m+ 1. Use SPL pulsed beam (3ms at 50 Hz)
2. Use beam stored in
accumulator and inner target
and thin transmission target
m 1. Use bunched proton beam
(train of 2.3 ms ,
12 bunches of 10 ns each at 40 MHz)
m 2. Use cooled muon beam ?
NUFACT05 -- physics
Alain Blondel
Collaborators of the scoping study:
-----
ECFA/BENE working groups (incl. CERN)
Japanese Neutrino Factory Collaboration
US Muon Collaboration
UK Neutrino Factory Collaboration
The output of the scoping study will be a report in which:
 The physics case for the facility is defined;
 A baseline design for the accelerator complex, or, for some subsystems, the programme
required to arrive at a baseline design, is identified;
 The baseline designs for the neutrino detection systems are identified; and
 The research-and-development programme required to deliver the baseline design is
described.
objectives
 Evaluate the physics case for a second-generation super-beam, a beta-beam facility and
the Neutrino Factory and to present a critical comparison of their performance;
 Evaluate the various options for the accelerator complex with a view to defining a baseline
set of parameters for the sub-systems that can be taken forward in a subsequent
conceptual-design phase; and to
 Evaluate the options for the neutrino detection systems with a view to defining a baseline
set of detection systems to be taken forward in a subsequent conceptual-design phase.
NUFACT05 -- physics
Alain Blondel
Physics
compare performance of various options
on equal footing of
parameters and conventions
and agreed standards of
resolutions, simulation etc.
identify tools needed to do so
(e.g. Globes upgraded?)
propose « best values » of
baselines, beam energies etc..
Detectors (NEW!)
Water Cherenkov (1000kton)
Magnetized Iron Calorimeter (50kton)
Low Z scintillator (100 kton)
Liquid Argon TPC (100 kton)
Hybrid Emulsion (4 kton)
Near detectors (and instrumentation)
Accelerator:
-----
proton driver (energy, time structure and consequences)
target and capture (chose target and capture system)
phase rotation and cooling
acceleration and storage
evaluate economic interplays and risks
include a measure of costing and
safety assessmentAlain Blondel
NUFACT05 -- physics
Conclusions
1. This brief discussion will have shown that many questions are left wide open.
The list of questions will need to be written up, circulated and criticized. Communication
between experimenters and phenomenologists will be essential.
2. A number of issues concern the concept of the experiments
muon or beta emitter energy, (polarization), rep rate, …
 near detector stations which will play a crucial role in CP violation measurements
and may have an impact on the accelerator design.
3. one should be careful however to remain on the real axis.
Power on target < 4 MW
Water Cherenkov < 1Mton
gamma for betabeam < 150 (CERN) < 300 (Fermilab) for antineutrnos
gamma for betabeam < 250 (CERN) < 500 (Fermilab) for antineutrnos
or else add cost of a new accelerator!
tau efficiency O(<10%) etc…
4. The neutrino factory physics calculations are quite old and need to be revisited
5. (to do lists for 2006) the conveners and members of WG1, WG2 and WG3
desserve congratulations for focus and followed-up discussions!
NUFACT05 -- physics
Alain Blondel
Clear message …
Beam power of the p-driver must be as large as possible !
The goal for the number of useful decays in the m storage ring for a given experiment
has to be 1E21/year.
n experiments will mobilize the p driver for ~ 10 years (1E7 s/y).
clear answer: YES
… please
NUFACT05 -- physics
Alain Blondel
Requests for clarification
Wide diversity of needs for m experiments.
Design is different if attached to a superbeam or a n factory.
m energy in n factory
Time structure of m beam
Both polarities simultaneously
Multiple base-lines
Location of multiple experiments
Detailed characteristics !
Justification of 50 GeV…
Interest of later upgrade ?
???
???
NUFACT05 -- physics
Alain Blondel
l
l-
m+ m
l+
d
ex: race track geometry:
constraint:
¦l- - l+¦ > l + d
where d is the precision
of the experiments time tag
plus margin
Muons of both signs circulate in
opposite directions in the same
ring. The two straight sections
point to the same far detector(s).
OK
There is one inconvenient with this:
the fact that there are two decay
lines implies two near detectors.
In addition this does not work for
the triangle.
this can be solved by
dog bone or
two rings with one or more common
straights
NUFACT05 -- physics
Alain Blondel
l
m+ m
n's
l-
n's
l+
this requires more arcs
and possibly more tunnel
L
I am sure part of this can be solved
(rings could be on top of each other)
n's
NUFACT05 -- physics
Alain Blondel
NUFACT05 -- physics
Alain Blondel
Analysis (responses…)
- Super-beam experiments ask for very different proton
beam energies for different base-lines
-
Optimum p energy for a n factory is still in debate,
but seems to be in the intermediate range (~ 5-10
GeV)
Need for a choice !
Need for a choice !
-
Proper analysis/optimization of low energy proton
driver depends upon production cross-sections
Need for HARP
results !

m experiments cannot share beam with n experiments.
If this is correct, should the powers requested from
the p driver be added ?
Compatibility ?
NUFACT05 -- physics
Alain Blondel
Muon Polarization
muons are born longitudinally polarized in pion decay (~18%)
depolarization is small (Fernow &Gallardo)
effects in electric and magnetic fields is (mostly) described by
spin tune:
which is small: at each kick  of a 200 MeV/c muon the polarization
is kicked by n.  0.002 
in the high energy storage ring polarization precesses. Interestingly
n 0.5 for a beam energy of 45.3112 GeV: at that energy spin flips at
each turn. (NB This is roughly half the Z mass…!)
NUFACT05 -- physics
Alain Blondel
Muon Polarization
muon polarization is too small to be very useful for physics
(AB, Campanelli) but it must be monitored.
In addition it is precious for energy calibration (Raja&Tollestrup, AB)
a muon polarimeter would perform the momentum analysis of the
decay electrons at the end of a straight section.
Because of parity violation in muon decay the ratio of high energy
to low energy electrons is a good polarization monitor.
NUFACT05 -- physics
Alain Blondel
muon polarization
here is the ratio of
# positons with E in [0.6-0.8] Em
to number of muons in the ring.
 There is no RF in the ring.
spin precession and
depolarization are clearly visible
This is the Fourier Transform
of the muon energy spectrum
(AB)
amplitude=> polarization
frequency => energy
decay => energy spread.
DE/E and sE/E to 10-6
polarization to a few percent.
NUFACT05 -- physics
Alain Blondel