Future Neutrino Oscillation Experiments physics

Future Neutrino Oscillation Experiments « physics » : status and priorities NUFACT 05 -- 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? ) NUFACT 05 -- 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? NUFACT 05 -- 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. T 2 HK, NOv. A) a) Super. Beam + Beta-Beam + Megaton detector (SB+BB+MD) Fréjus b) Neutrino Factory (Nu. Fact) + magnetic detector (40 kton)+… The physics abilities of the neutrino factory are superior but…. . « what is the realistic time scale? » (Hardware) cost estimate of a neutrino factory ~1 B€ + 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’ NUFACT 05 -- physics Alain Blondel

The neutrino mixing matrix: 3 angles and a phase 3 Dm 223= 2 10 -3 e. V 2 2 1 Dm 212= 8 10 -5 e. V 2 OR? 2 1 23 (atmospheric) = 450 , 12 (solar) = 320 , 13 (Chooz) < 130 3 Dm 212= 8 10 -5 e. V 2 Dm 223= 2 10 -3 e. V 2 Unknown or poorly known even after approved program: 2 13 , phase , sign of Dm 13 NUFACT 05 -- physics Alain Blondel

CP violation P( e ) - P( e ) + P( e ) = ACP a sin (Dm 212 L/4 E) sin 12 sin 13 + solar term… … need large values of sin 12, Dm 212 (LMA) but *not* large sin 2 13 … need APPEARANCE … P( e e) 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 , t … asymmetry is opposite for e and e t P( e ) = ¦A¦ 2+¦S¦ 2 + 2 A S sin P( e ) = ¦A¦ 2+¦S¦ 2 - 2 A S sin NUFACT 05 -- physics Alain Blondel

! T asymmetry for sin = 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 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 (2 d max or 3 d max. ) 0. 10 0. 30 10 30 3. sign of asymmetry changes with max. number. NUFACT 05 -- physics Alain Blondel 90

Mezzetto NUFACT 05 -- physics Alain Blondel

T 2 K Phase II: 4 MW upgrade Phase II HK: 1000 kt SK: 22. 5 kt Kamioka J-PARC JPARC- ~0. 6 Ge. V beam 0. 75 MW 50 Ge. V PS (2008 ) K 2 K ~1. 2 Ge. V beam 0. 01 MW 12 Ge. V PS (1999 2005) NUFACT 05 -- physics Alain Blondel

NUFACT 05 -- physics Alain Blondel

CERN-SPL-based Neutrino SUPERBEAM 300 Me. V Neutrinos small contamination from e (no K at 2 Ge. V!) target! Fréjus underground lab. A large underground water Cherenkov (400 kton) UNO/Hyper. K 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) NUFACT 05 -- physics Alain Blondel

CERN: -beam baseline scenario neutrinos of Emax=~600 Me. V Nuclear Physics SPL target! Decay ring B=5 T Decay ISOL target & Ion source SPS ECR Ring Cyclotrons, linac or FFAG Rapid cycling synchrotron Lss = 2500 m Stacking! PS Same detectors as Superbeam ! NUFACT 05 -- physics Alain Blondel

Beta-beam at FNAL Winter (IAS Princeton) CERN FNAL gmax = gmaxproton/3 for 6 He fault of this one has to buy a new Te. V acccelerator. NUFACT 05 -- physics Alain Blondel

Combination of beta beam with low energy super beam combines CP and T violation tests e ( +) (T) e (p+) (CP) e ( -) (T) e (p-) NUFACT 05 -- physics Alain Blondel

EC: A monochromatic neutrino beam Electron Capture: N+e- N’+ e NUFACT 05 -- physics Burget et al 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 d. N/d. E ) 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 k. W! NUFACT 05 -- physics Alain Blondel

-- Neutrino Factory -- CERN layout -- cooling! 1016 p/s target! acceleration! 1. 2 1014 /s =1. 2 1021 /yr 0. 9 1021 /yr 3 1020 e/yr 3 1020 /yr + e oscillates e interacts giving - WRONG SIGN MUON _ interacts giving + Golden Channel also (unique!) e NUFACT 05 -- physics channel t Silver 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 1 st osc. max at 6 Ge. V and 2 d max at 2 Ge. V. Muon momentum cut at 4 Ge. V cuts 2 d 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) NUFACT 05 400 M$*E/20 5. optimal muon ENERGY? Cost of study II was 1500 M$ + -- physics Alain Blondel

NB: This works just as well INO ~7000 km (Magic distance) NUFACT 05 -- physics Alain Blondel

Towards a comparison of performances on equal footing CP violation example P( e ) - P( e ) + P( e ) = ACP a sin (Dm 212 L/4 E) sin 12 sin 13 + solar term… e diff. cross-section*flux BUT: need to know and diff. cross-section and detection efficiency Near detector should give 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 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-Ge. V superbeam alone how can one deal -- physics Alain Blondel NUFACT 05 with this?

Zeller ds/d O(e, e’ ), =Ee-Ee’=Enegy transfer (Ge. V) Ee=700 -1200 Me. V 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 NUFACT 05 -- physics Alain Blondel

Neutrino fluxes + -> e+ e / e ratio reversed by switching +/ e spectra are different No high energy tail. Very well known flux ( 10 -3) -- E&s. E calibration from muon spin precession -- angular divergence: small effect if < 0. 2/g, -- 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 NUFACT 05 -- 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. 3. 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) 4. 5. 6. 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 NUFACT 05 -- physics Alain Blondel

Degeneracies Stephano Rigolin: P. Huber’s beautiful plots assume: 4 Ge. V threshold, only golden channel. Experimenters need to provide characteristics of tau detectors and think about efficiency for wrong sign muons at low energies. NUFACT 05 -- physics Alain Blondel

range at 1. 5 Ge. V is 1. 5 meters what is the sign confusion at that momentum? typical energy resolution ïs 0. 4 Ge. V at 1. 5 Ge. V NUFACT 05 -- physics Alain Blondel

NUFACT 05 -- physics Alain Blondel

…………………degeneracies systematics. correlations approval date: ~NOv. A +PD -beam + SPL 3. 5 SB+Mton Lindner et al newer plot should come out of NUFACT 05 and scoping study NUFACT 05 -- physics Alain Blondel

What happens to this at high 13 if -- two baselines are considered and -- a threshold of 1. 5 Ge. V for wrong sign muons is imposed on the 3000 km det -- and there is a 4 kton tau detector at the 3000 km station? NUFACT 05 -- physics Alain Blondel

+ Thoughts for muon targets in neutrino factory complex + 1. Use SPL pulsed beam (3 ms at 50 Hz) 2. Use beam stored in accumulator and inner target and thin transmission target - 1. Use bunched proton beam (train of 2. 3 s , 12 bunches of 10 ns each at 40 MHz) - 2. Use cooled muon beam ? NUFACT 05 -- 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. NUFACT 05 -- 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 (1000 kton) Magnetized Iron Calorimeter (50 kton) 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 NUFACT 05 -- physics Alain Blondel

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, … à 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 < 1 Mton 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 WG 1, WG 2 and WG 3 desserve congratulations for focus and followed-up discussions! NUFACT 05 -- 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 storage ring for a given experiment has to be 1 E 21/year. experiments will mobilize the p driver for ~ 10 years (1 E 7 s/y). clear answer: YES … please NUFACT 05 -- physics Alain Blondel

Requests for clarification Wide diversity of needs for experiments. Design is different if attached to a superbeam or a factory. Detailed characteristics ! energy in factory Justification of 50 Ge. V… Interest of later upgrade ? Time structure of beam Both polarities simultaneously ? ? ? Multiple base-lines Location of multiple experiments ? ? ? NUFACT 05 -- physics Alain Blondel

l l- + - l+ d ex: race track geometry: constraint: ¦l- - l+¦ > l + d where d is the precision 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 of the experiments time tag plus margin NUFACT 05 -- physics Alain Blondel

l + - '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) 's NUFACT 05 -- physics Alain Blondel

NUFACT 05 -- physics Alain Blondel

Analysis (responses…) - Super-beam experiments ask for very different proton beam energies for different base-lines - Optimum p energy for a factory is still in debate, but seems to be in the intermediate range (~ 5 -10 Ge. V) - Need for a choice ! Proper analysis/optimization of low energy proton driver depends upon production cross-sections - Need for a choice ! experiments cannot share beam with experiments. If this is correct, should the powers requested from the p driver be added ? NUFACT 05 -- physics Need for HARP results ! Compatibility ? 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 q of a 200 Me. V/c muon the polarization is kicked by n. q = 0. 002 q in the high energy storage ring polarization precesses. Interestingly n= 0. 5 for a beam energy of 45. 3112 Ge. V: at that energy spin flips at each turn. (NB This is roughly half the Z mass…!) NUFACT 05 -- 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. NUFACT 05 -- physics Alain Blondel

muon polarization here is the ratio of # positons with E in [0. 6 -0. 8] E 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 s. E/E to 10 -6 polarization to a few percent. NUFACT 05 -- physics Alain Blondel