future neutrino oscillation experiments « physics »: status and priorities

NUFACT05 -- physics Alain Blondel

Future Neutrino Oscillation Experiments« physics »: status and priorities


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 phasethis 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 phaseare there physics arguments?

2. verification of global picture -- oscillation pattern-- unitarity (what would it mean to observe violation of it?)


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 hierarchyImportant objectives: unambiguous precision measurements of mixing angles and mass differences,lepton flavour violation with muonsby-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?


Avenues identified as promisinga) Superbeam alone + large detector(s) (e.g. T2HK, NOvA) a) SuperBeam + Beta-Beam + Megaton detector (SB+BB+MD) Fréjusb) 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

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)

‘scoping study’


The neutrino mixing matrix: 3 angles and a phase

Unknown or poorly known even after approved program:13 , phase , sign of m13

OR?

m223= 2 10-3eV2

m212= 8 10-5 eV2

23(atmospheric) = 450 , 12(solar) = 320 , 13(Chooz) < 130

2

m212= 8 10-5 eV2

m223= 2 10-3eV2


P(e) = ¦A¦2+¦S¦2 + 2 A S sin

P(e) = ¦A¦2+¦S¦2 - 2 A S sin

= ACP sinsolar term…

sinsin (m212 L/4E) sin

… need large values of sin m212 (LMA) but *not* large sin2

… need APPEARANCE … P(ee) is time reversal symmetric (reactor s do not work)

… can be large (30%) for suppressed channel (one small angle vs two large)

at wavelength at which ‘solar’ = ‘atmospheric’ and for e , … asymmetry is opposite for e and e

P(e) - P(e)

P(e) + P(e)

CP violation


T asymmetry for sin = 1

0.10 0.30 10 30 90

JHFI-SK

!asymmetry is

a few % and requires

excellent flux normalization

(neutrino fact., beta beam or

off axis beam withnot-too-near

near detector)

JHFII-HK

neutrino factory

NOTEs:1. sensitivity is more or lessindependent of 13 down to

max. asymmetry point

2. This is at first maximum!Sensitivity at low valuesof 13 is better for shortbaselines, sensitivity atlarge values of 13 isbetter for longer baselines(2d max or 3d max.)

3.sign of asymmetry changes with max. number.


Mezzetto


JPARC-JPARC- ~0.6GeV ~0.6GeV beam beam 0.75 MW 50 GeV PS 0.75 MW 50 GeV PS

(2008 (2008 ))KamiokaKamioka J-PARCJ-PARC

SK: 22.5 ktSK: 22.5 kt

Phase II:Phase II:4 MW upgrade4 MW upgradePhase IIPhase II

HK: 1000 ktHK: 1000 kt

K2K ~1.2 GeV K2K ~1.2 GeV beam beam 0.01 MW 12 GeV PS 0.01 MW 12 GeV PS

(1999 (1999 2005)2005)

T2K


300 MeV Neutrinos

small contamination from e (no K at 2 GeV!)

A large underground water Cherenkov (400 kton) UNO/HyperKor/and a large L.Arg detector. also : proton decay search, supernovae events solar and atmospheric neutrinos. Performance similar to J-PARC IIThere is a window of opportunity for digging the cavern stating in 2009 (safety tunnel in Frejus)

CERN-SPL-based Neutrino SUPERBEAM

Fréjus underground lab.

target!


CERN: -beam baseline scenario

PS

Decay

RingISOL target & Ion source

SPL

Cyclotrons, linac or FFAG

Decay ring

B = 5 T

Lss = 2500 m

SPSECR

Rapid cycling synchrotron

Nuclear Physics

,

Same detectors as Superbeam !

target!

Stacking!

neutrinos of Emax=~600MeV

eFNe e189

1810

eLiHe e63

62


Beta-beam at FNALWinter (IAS Princeton)

CERN FNAL

max = maxproton/3

for 6He

fault of this one has to buy a new TeV acccelerator.


Combination of beta beam with low energy super beam

combines CP and T violation tests

e (+) (T) e (+)

(CP)

e (-) (T) e (-)


EC: A monochromatic neutrino beam

Decay T1/2 BR EC/ ECI B(GT) EGR GR QEC E E

148Dy 148Tb* 3.1 m 1 0.96 0.96 0.46 620 2682 2062

150Dy 150Tb* 7.2 m 0.64 1 1 0.32 397 1794 1397

152Tm2- 152ET* 8.0 s 1 0.45 0.50 0.48 4300 520 8700 4400 520

150Ho2- 150Dy* 72 s 1 0.77 0.56 0.25 4400 400 7400 3000 400

Electron Capture: N+e- N’+e Burget et al


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/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!


-- Neutrino Factory -- CERN layout --

e+ e

_

interacts

giving

oscillates einteracts givingWRONG SIGN MUON

Golden Channel

1016p/s

1.2 1014 s =1.2 1021 yr

3 1020 eyr

3 1020 yr

0.9 1021 yr

target!cooling!

acceleration!

also (unique!) eSilver channel


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.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)

5. optimal muon ENERGY? Cost of study II was 1500M$ + 400M$*E/20

SPSC 2004 Villars Alain Blondel, 24/09/04

Where do you prefer to take shifts?

SPSC 2004 Villars Alain Blondel, 24/09/04

-- Neutrino Factory --CERN layout

e+ e _

interacts

giving oscillates e interacts giving WRONG SIGN MUON

1016p/s

1.2 1014 s =1.2 1021 yr

3 1020 eyr3 1020 yr

0.9 1021 yr


NB: This works just as well

INO ~7000 km (Magic distance)


Towards a comparison of performances on equal footing

CP violation example

= ACP sinsolar term…

sinsin (m212 L/4E) sin P(e) - P(e)

P(e) + P(e)

Near detector should give e diff. cross-section*flux

BUT:need to know and diff. cross-section and detection efficiency

with small (relative) systematic errors.

interchange role of e and for superbeam

in case of beta-beam one will need a superbeam at the same energy. Will it bepossible 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?


d/de,e’EeEe’Enegy transfer (GeV)Ee=700-1200 MeV

Blue: Fermi-gasGreen: SPRed: SP+FSI

QE

Zeller

These are for electronbeam. errors are ~5-10% but what happenswhen a muon mass is involved?


Neutrino fluxes + -> e+ e

/ e ratio reversed by switching

e spectra are different No high energy tail.

Very well known flux (10-3)

-- E& calibration from muon spin precession

-- angular divergence: small effect if < 0.2/

-- absolute flux measured from muon current or by e -> e 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…)

polarization controls e flux:

+ -X> e in forward direction


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 m )and gradually become easier at high Energies. Neutrino factory provides all channels in the same beam line/detector


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.


range at 1.5 GeV is 1.5 meterswhat is the sign confusion at that momentum?

typical energy resolution ïs 0.4 GeV at 1.5 GeV


Lindner et al

newer plot should come out of NUFACT05 and scoping study

……………………………………degeneraciescorrelationssystematics

.

beam + SPL3.5 SB+Mton

approval date:

~NOvA +PD


What happens to this at high 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?


Thoughts for muon targets in neutrino factory complex

1. Use SPL pulsed beam (3ms at 50 Hz) and thin transmission target2. Use beam stored in

accumulator and inner target

2. Use cooled muon beam ?

1. Use bunched proton beam (train of 2.3 s , 12 bunches of 10 ns each at 40 MHz)


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 programmerequired to arrive at a baseline design, is identified;The baseline designs for the neutrino detection systems are identified; andThe research-and-development programme required to deliver the baseline design isdescribed.

objectives Evaluate the physics case for a second-generation super-beam, a beta-beam facility andthe 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 baselineset of parameters for the sub-systems that can be taken forward in a subsequentconceptual-design phase; and toEvaluate the options for the neutrino detection systems with a view to defining a baselineset of detection systems to be taken forward in a subsequent conceptual-design phase.


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)

Physics

compare performance of various options on equal footing of parameters and conventionsand agreed standards of resolutions, simulation etc.

identify tools needed to do so (e.g. Globes upgraded?)

propose « best values » of baselines, beam energies etc..

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 risksinclude a measure of costing and safety assessment


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 measurementsand may have an impact on the accelerator design.

3. one should be careful however to remain on the real axis. Power on target < 4 MWWater Cherenkov < 1Mtongamma for betabeam < 150 (CERN) < 300 (Fermilab) for antineutrnosgamma 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!


Clear message …

Beam power of the p-driver must be as large as possible !

The goal for the number of useful decays in the storage ring for a given experiment has to be 1E21/year.

experiments will mobilize the p driver for ~ 10 years (1E7 s/y).

clear answer: YES … please


Requests for clarification

Wide diversity of needs for experiments. Design is different if attached to a super-beam or a factory.

energy in factory

Time structure of beamBoth polarities simultaneously

Multiple base-linesLocation of multiple experiments

Justification of 50 GeV…Interest of later upgrade ?

???

???

Detailed characteristics !


ll-

l+

ex: race track geometry:constraint:

¦l- - l+¦ > l +

where is the precision

of the experiments time tagplus 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 ortwo rings with one or more common straights


ll-

l+

Lthis requires more arcs and possibly more tunnel

I am sure part of this can be solved(rings could be on top of each other)

's

's

's


Analysis (responses…)

- Super-beam experiments ask for very different proton beam energies for different base-lines

- Optimump energy for a 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

experiments cannot share beam with experiments. If this is correct, should the powers requested from the p driver be added ?

Need for a choice !

Need for HARP results !

Need for a choice !

Compatibility ?


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 polarizationis kicked by

in the high energy storage ring polarization precesses. Interestingly for a beam energy of 45.3112 GeV: at that energy spin flips at each turn. (NB This is roughly half the Z mass…!)


Muon Polarizationmuon 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.


muon polarization here is the ratio of

# positons with E in [0.6-0.8] Eto number of muons in the ring. There is no RF in the ring.

spin precession and depolarization are clearly visibleThis is the Fourier Transform of the muon energy spectrum(AB)amplitude=> polarizationfrequency => energydecay => energy spread.

E/E and E/E to 10-6

polarization to a few percent.

future neutrino oscillation experiments « physics »: status and priorities

Documents