Neutrino Factory scenarios

1. Neutrino Factory scenarios I will endeavour to address some principle design issues related to the physics use of high intensity muon beams. Some ideas will be given. 1. intense muon beams in neutrino factory complex. (CERN model) 2. neutrino factory parameters.

2. High Intensity Low Energy muon beams PSI already has 1 MW DC beam of 590 MeV protons with 5%lI target for muons. How can one do 1000 times better? DC beams (meg , meee) 1. Thin inner target in proton accumulator advantages: very efficient use of proton beam, point source difficulties: - can target take the heat? - creates high-radiation area inside ring 20 - 120 2. Or Use full DC SPL 24 MW with thin muon target 20 + solenoid collection (1/.16)2 =40 + better experiments ? Pulsed beam (m-N e-N) 1. Use proton beam from buncher 2. Use muons at the end of cooling channel! --> need now conceptual design of target station and muon beams

3. 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 ?

5. From neutrino factory to Higgs collider More cooling + sE/E reduction Separate m+ & m- , add transfer lines Upgrade to 57.5 GeV m+m-h (115) Muon collider: a small…. but dfficult ring

6. Neutrino Factory parameters Energy Intensity ring geometry running mu+ and mu- at the same time

7. Energy The sensitivity to q13 is a steep function of energy: -- signal event rate increases like En -- background in wrong sign muons decreases fast with E The sensitivity to CP violation is not, energies >30 GeV do not contribute significantly to the sensitivity *-> The nent channel is essential threshold at 3.5 GeV and full efficiency at 15 GeV The matter resonance is essential (12 GeV) => <En> = 3/4 Em >= 15 GeV ==> Em >~ 20 GeV…

8. Iron calorimeter Magnetized Charge discrimination B = 1 T R = 10 m, L = 20 m Fiducial mass = 40 kT Detector Also: L Arg detector: magnetized ICARUS Wrong sign muons, electrons, taus and NC evts *-> Events for 1 year nmsignal (sin2q13=0.01) nm CC ne CC Baseline 732 Km 1.1 x 105 CF ne signal at J-PARC =40 3.5 x 107 5.9 x 107 1.0 x 105 3500 Km 2.4 x 106 1.2 x 106

9. 5-10 GeV 10-20 GeV 20-30 GeV 30-40 GeV 40-50 GeV CP violation Matter effect must be subtracted. spectrum of matter effect and CP violation is different • It is important to subtract in bins of measured energy. • knowledge of spectrum is essential here! 40 kton L M D 50 GeV nufact 5 yrs 2.1020m /yr In fact, 20-30 GeV is enough! Best distance is 2500-3500 km

10. Intensity of muons in Neutrino factory storage ring As high as possible i.e. >1014 per second

11. muon polarization: triangle or bow-tie? For a race track or triangle decay ring, in which polarization precesses it is possible to calibrate beam energy and energy spread with g-2 precession measurement A bow-tie has been suggested to avoid this spin precession and depolarization (net bend is zero, so muon polarization does not precess either) This has several inconvenients: -- P is different for the three straights in triangle (who shall be pleased?) -- P cannot be reversed -- E and s(E) can no longer be measured -- in order to know the flux to 0.1% on must know P to 0.1% and this is hard! end of the bow tie.

12. CERN baseline scenario

13. -- Neutrino Factory --CERN layout 1016p/s 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 givingm- WRONG SIGN MUON interacts giving m+

14. Angular divergence If the muons have transverse momentum comparable to that of muon decay (50 MeV) the neutrino beam will be seriously degraded this corresponds to s(q) = 0.5 mm/Em

16. Divergence of 0.1/g keeps 95% of the original flux. Straight section with this property were designed for the US Study II and by Keil Divergence MUST be measured. A gas Cerenkov device to measure the beam emittance was devised by Piteira. Various efects were considered (optical aberrations, heating of gas, multiple scattering, etc…and concluded that the divergence is easier to measure the bigger it is so that this should not be a problem)

17. Conclusions I Main parameters to MONITOR 1. Total number of muons circulating in the ring, BCT, near detector for purely leptonic processes 2. muon beam polarisation, polarimeter 3. muon beam energy and energy spread, race-track or triangle. NO BOW-TIE! +polarimeter 4. muon beam angle and angular divergence. straight section design +beam divergence monitors e.g. Cerenkov 5. Theory of m decay, including radiative effects OK Yes, we believe that the neutrino flux can be monitored to 10-3 IF + design of accelerator foresees sufficient diagnostics. + quite a lot of work to do to design and simulate these diagnostics.

18. Injecting two polarities RF phase rotation and linear cooling channel work for both signs of muons (and rings also with adequate separate injection/ejection lines) this opens the possibility to double the flux by running mu+ and mu- at the same time, but the detector must be able to identify them by timing. The detectors can presumably identify by timing the source of events at the level of 100ns (number to be refined) i.e. 30 m. mu+ and mu- microbunches from 200 MHz RF (2.5 ns) cannot be separated. This requires some design gymnastics for the injection in the storage ring and its geometry.

19. 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

20. n's n's 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