The MICE collaboration

1
Future Neutrino Oscillation Experiments  physics
  status and priorities
2
The BIG picture

• 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
• 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?)

3
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?
4
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
(SBBBMD) 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 (BBSBMD) is not
very different Cost/physics performance/feasibil
ity comparison needed
? scoping study
5
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
Dm212 8 10-5 eV2
Dm223 2 10-3eV2
n3
q23 (atmospheric) 450 , q12 (solar) 320 , q13
(Chooz) Unknown or poorly known even after approved
program ?13 , phase ? , sign of
Dm13
2
6
CP violation
P(ne?nm) - P(ne?nm)
sind sin (Dm212 L/4E) sin q12
ACP a
sinq13 solar term
P(ne?nm) P(ne?nm)
need large values of sin q12, Dm212 (LMA) but
not large sin2q13 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??? , ?t asymmetry is opposite for
ne??? and ne??t
P(ne?nm) A2S2 2 A S sin d
P(ne?nm) A2S2 - 2 A S sin d

7
! asymmetry is a few and requires excellent
flux normalization (neutrino fact., beta beam
or off axis beam with not-too-near near
detector)
T asymmetry for sin ? 1
neutrino factory
JHFII-HK
JHFI-SK
NOTEs 1. sensitivity is more or less independent
of q13 down to max. asymmetry point 2. This is
at first maximum! Sensitivity at low values of
q13 is better for short baselines, sensitivity
at large values of q13 is better for longer
baselines (2d max or 3d max.) 3.sign of
asymmetry changes with max. number.
10
30
0.10
0.30
90
8
Mezzetto
9
T2K
Phase II 4 MW upgrade
Phase II HK 1000 kt
JPARC-? 0.6GeV n beam 0.75 MW 50 GeV PS (2008
?)
SK 22.5 kt
Kamioka
J-PARC
K2K 1.2 GeV n beam 0.01 MW 12 GeV PS (1999
?2005)
10
(No Transcript)
11
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)
12
CERN b-beam baseline scenario
neutrinos of Emax600MeV
SPL
target!
Decay ring B 5 T Lss 2500 m
SPS
Decay Ring
ISOL target Ion source
ECR
Cyclotrons, linac or FFAG
Stacking!
Rapid cycling synchrotron
PS
Same detectors as Superbeam !
13
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.
14
Combination of beta beam with low energy super
beam
combines CP and T violation tests ?e ? ?m
(?) (T) ?m ? ?e (p) (CP) ?e ? ?m
(?-) (T) ?m ? ?e (p-)
15
EC A monochromatic neutrino beam
Electron Capture Ne- ? Nne
Burget et al
16
SuperbeamBetabeamMegaton option

• 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?
• 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/dE? )
• 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!
17
-- Neutrino Factory -- CERN layout --
cooling!
1016p/s
target!
acceleration!
1.2 1014 m/s 1.2 1021 m/yr
_
0.9 1021 m/yr
m ? e ne nm
3 1020 ne/yr 3 1020 nm/yr
oscillates ne ? nm interacts giving m- WRONG
SIGN MUON Golden Channel
interacts giving m
also (unique!) ne ? nt Silver channel
18

• Questions for Neutrino Factory experiments( ?
  very few studies in the last 2 years)
• Do we REALLY NEED TWO far locations at two
  different distances?
• 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?
• Can we eliminate all degenracies by combination
  of energy distribution and analysis of different
  channels (tau, muon, electron, both signs, NC)
  
• what are the systematics on flux control? (CERN
  YR claims 10-3)
• 5. optimal muon ENERGY? Cost of study II was
  1500M 400ME/20

19
NB This works just as well
INO 7000 km (Magic distance)
20
Towards a comparison of performances on equal
footing
CP violation example
P(ne?nm) - P(ne?nm)
sind sin (Dm212 L/4E) sin q12
ACP a
sinq13 solar term
P(ne?nm) P(ne?nm)
Near detector should give ne diff.
cross-sectionflux BUTneed to know nm and nm
diff. cross-section and detection 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 can one deal with this?
21
ds/dn O(e,e), nEe-EeEnegy transfer
(GeV)Ee700-1200 MeV
Zeller
Blue Fermi-gas Green SP Red SPFSI
These are for electron beam. errors are 5-10
but what happens when a muon mass is involved?
QE
D
22
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) -- EsE
calibration from muon spin precession -- angular
divergence small effect if q 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 in
forward direction
23

• A discussion is necessary to establish reasonable
  systematic errors
• in measuring the CP or T asymmetry
• this discussion should include the following
  questions
• what kind of near detector will be needed?
• 2. how does one measure the cross-sectioneffici
  ency 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

24
Degeneracies
Stephano Rigolin
P. Hubers 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.
25
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
26
(No Transcript)
27
systematics .
degeneracies
correlations
approval date
NOvA PD
Lindner et al
newer plot should come out of NUFACT05 and
scoping study
28
What happens to this at high q13 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?
29
Thoughts for muon targets in neutrino factory
complex
m 1. Use SPL pulsed beam (3ms at 50 Hz) and
thin transmission target
m 2. Use beam stored in accumulator and
inner target
m- 1. Use bunched proton beam (train of 2.3
?s ,
12 bunches of 10 ns each at 40 MHz)
m- 2. Use cooled muon beam ?
30
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 conceptu
al-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.
31
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
assessment
32
Conclusions

• 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
• Water Cherenkov
• gamma for betabeam for antineutrnos
• gamma for betabeam for antineutrnos
• or else add cost of a new
  accelerator!
• tau efficiency O(
• 4. The neutrino factory physics calculations are
  quite old and need to be revisited

33
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
34
Requests for clarification

• Wide diversity of needs for m experiments. Design
  is different if attached to a super-beam 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 ?
???
???
35
l
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
l-
l
m m-
d
ex race track geometry constraint l- - l
l d where d is the precision of the
experiments time tag plus margin
36
l
l-
l
m m-
L
this requires more arcs and possibly more
tunnel I am sure part of this can be
solved (rings could be on top of each other)
n's
37
(No Transcript)
38
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)
• Proper analysis/optimization of low energy proton
  driver depends upon production cross-sections
• m experiments cannot share beam with n
  experiments. If this is correct, should the
  powers requested from the p driver be added ?

Need for a choice !
Need for a choice !
Need for HARP results !
Compatibility ?
39
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 q of a 200 MeV/c
  muon the polarization
• is kicked by n.q 0.002 q
• in the high energy storage ring polarization
  precesses. Interestingly
• 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!)

40
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 (RajaTollestrup, 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.
41
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.