PRISM and Neutrino Factory in Japan Y. Kuno KEK, IPNS January 19th, 2000 at CERN

PRISM

What is PRISM ? PRISM (Phase Rotation Intense Slow Muon source)  = a dedicated secondary muon beam channel with high intensity and  narrow energy spread  for stopped muon experiments.

PRISM Scheme pulsed proton beam pion capture by high solenoid field pion decay section phase rotation section

PRISM Beam Characteristics intensity :  ± /sec muon kinetic energy :  20 MeV (=68 MeV/c) – range = about 3 g kinetic energy spread : ± MeV – ±a few 100 mg range width beam repetition :  about 1 kHz – in terms of muon lifetime, a 100kHz -1 MHz is ideal. – increase in future, if technically possible.

Summary PRISM would be a unique and novel facility in the world, born in Japan. It is attracting much attensions in the worldwide. A search for muon LFV violation is one of main topics at PRISM, in particular  -e conversion. Applications like biology etc. might as well be incorporated. Most of technology is in hand, but need some prototyping. A design note by May, 2000 ? Cost estimation ? We are hoping to construct PRISM by the time when the 50-GeV PS will be on.

maximum transverse momentum –R : radius of magnet –ex: H =120kG(=12T), R =5cm » P T < 90 MeV/c capture yields Pion Capture Yield low energy pions for 50GeV protons 0.2 pions/proton

Guide Lines of SC Solenoid Magnet Configuration – A hybrid solenoid magnet of T at 4.2 K – Radiation shield with water cooling Coil cooling – conductive cooling with high heat- transfer path – heat load < a few 10 W (goal) Cryogenics – cryo-cooler in parallel operation or refrigerator with remote heat exchanger. – located at a few meter away from the coil.

Phase Rotation = decelerate particles with high energy and accelerate particle with low energy by high- field RF A narrow pulse structure (<1 nsec) of proton beam is needed to ensure that high-energy particles come early and low-energy one come late. Phase Rotation energy time important

Phase Rotation Simulation simulation with rf kicks after phase rotation before phase rotation

Why FFAG for Phase Rotation ? a ring instead of linear systems – reduction of # of rf cavities – reduction of rf power comsumption – compact (Fixed Field Alternating Synchrotron) synchrotron oscillation for phase rotation – not cyclotron (isochronous) large momentum acceptance – larger than synchrotron – ± several 10 % is aimed large transverse acceptance – strong focusing – large horizontal emittance – reasonable vertical emittance at low energy

PRISM layout not in scale

Phase Rotation Simulation at FFAG(1) non-linear relation on energy vs. time at low energy in case of sin-wave rf – after 5 turns dp/p(%) phase (degree)

Phase Rotation Simulation at FFAG (2) in case of saw-tooth wave rf phase (degree) dp/p(%)

PRISM at the 50-GeV PS why at the 50-GeV PS? – a narrow bunched proton beam is needed. in the 50-GeV PS experimental hall

Muon Yield Estimation at PRISM muon yield – P T <90 MeV/c (12T 5cm radius) at pion capture – 3000  mm ・ mrad vertical acceptance of FFAG in 20 MeV±( )MeV range proton intensity at the 50-GeV PS – proton/sec muon yield –  ± /sec  ± /proton OK!

How, Muon LFV?

Status of Muon LFV Experimental status 1) PSI experiment (2003) 2) PSI experiment (running) 3) BNL-E940 (MECO) experiment (2003) Muon LFV at PRISM – the best for  -e conversion » a pulsed beam needed. –  e  eee » continuous beam needed to reduce accidental background. – muonium to anti-muonium conversion » a pulsed beam is needed.

 e  conversion in a Muonic Atom muonic atom (1s state) neutrinoless muon nuclear capture (=   - e conversion) muon decay in orbit nucleus  nuclear muon capture lepton flavors changes by one unit. coherent process

 e  conversion:Signal and Background coherent conversion (  Z 5 ) Event Signature – single mono-energetic electron of (m  -B  ) MeV Backgrounds – no accidental background – muon decay in orbit (  E) 5 ) » highest endpoint comes to the signal – radiative muon capture with photon conversion – pion capture with photon conversion » to remove pions in beam, a pulsed beam is useful, where the measurement waits until pions decay. – cosmic ray

MECO at BNL/AGS E940 aim at B(    Al  e   Al   at BNL AGS MECO 5x10 11  - /pulse, 1.1MHz pulse – 8GeV proton beam at AGS – high field capture solenoid of 4T schedule : 2003 start ???

PRISM Beam Requirement for  - e conversion higher muon intensity –  - /sec pulsed beam – background rejection narrow energy spread – allow a thinner muon-stopping taret » better e - resolution and acceptance » point source – allow a beam blocker behind the target » isolate the target and detector » tracking close to a beam axis less beam contaminations – no pion contamination » long flight path at FFAG (150 m) – beam extinction between pulses » kicker magnet at FFAG

target blocker SC solenoid magnet trigger counter tracking chamber 106 MeV electron not in scale muon beam from PRISM a magnetic field is graded at the target region. (details are not determined)

Improvement of Signal Sensitivity 100 cm time energy

  e  conversion: Muon Decay in Orbit Muon decay in orbit (  (E  e -E e ) 5 ) – required e + momentum resolution is determined ( keV) at sensitivity present limit MECO goal JHF goal signal

What Else from PRISM ?

More Physics Lists with PRISM muon (g-2) – muon momenum = 3 GeV/c – small beam may improve the sensitivity further. – muon polarization muon EDM – muon momentum = 500 MeV/c – high intensity and small beam should improve the sensitivity. – muon polarization muonium to anti-muonium conversion muon lifetime muonium spectroscopy muonic atom spectroscopy

Application List with PRISM Brain scan studies – muonic X-ray measurement. –  - beam from PRISM with small stopping region. trace-element analysis – living cells biology materials science nsec response spectroscopy with muons. – phase rotation to make narrow time width (instead of narrow energy spread). time

Future studies on PRISM muon polarization – with cost of muon intensity, can improve muon polarization ? muon cooling – can muon be cooled at PRISM ? – precooling by H 2 – higher than 300 MeV/c – high rf gradient needed. Additional acceleration – to an muon EDM ring ? » MeV/c – to a muon g-2 ring ? » 3 GeV/c (magic momentum) – cooling or no-cooling ??

from PRISM to neutrino factory

Neutrino Factory

Oscillation Signature at Neutrino Factory Oscillation signature charge identification needed. –  + /   is easy. –e + /e  is difficult. oscillation

Advantages of Neutrino factory  …...compared with a neutrino source of pion decays, large neutrino intensity at high energy – 2x10 20 neutrinos/year ( ) – about 100 times intensity at a few 10 GeV energy range extremely low backgrounds – to level (charm background) » a few % level at the pion sources. precise knowledge on neutrino intensity and emittance

Event Rates CC event rate Oscillation rate higher energy, better…. a number of CC events/year – muons/year in the ring – for a 10 kton detector a la O.Yasuda

Oscillation Probabilities when measurement of – appearance measurement, for instance, – sensitivity is determined by backgound level ( ) » a la Juan Jose Gomez Cadenas – enhancement of matter effect

Wrong Sign Muons: P( e   

Wrong Sign Muons: P( e   

Wrong Sign Muons: P( e   

Opportunity of Neutrino Factory at 50-GeV PS A possible opportunity in Japan will be based on the case of the 50-GeV PS, as an existing proton driver. – 1st phase: 0.75 MW – 2nd phase: 4 MW?? If the 50-GeV PS is already available, construction of a neutrino factory is very cost- effective. The PRISM (= a low-energy muon source) experience will be directly and effectively extended towards a  neutrino factory.

a factor of only 20! Towards Neutrino Factory at the 50-GeV PS increase of muon yield –  ± /year for PRISM – 2x10 20  ± /year for a neutrino factory – possible improvements are » higher capture magnetic field » pions capture of higher momentum » forward extraction at the target » precooling and after-cooling, etc. increase of proton intensity at the 50-GeV PS – protons/sec for Phase-I – 5x10 14 protons/sec for Phase-II increase the detector size – cheeper than accelerator – an event yield is the product of beam intensity and detector size.

Long Baseline from 50-GeV PS long baseline Fukuoka(1000km) Shanghai(2000km) Kamioka(250km) Tokai

Summary PRISM would be a unique and novel facility in the world, born in Japan. It is attracting much attensions in the worldwide. A search for muon LFV violation is one of main topics at PRISM, in particular  -e conversion. Applications like biology etc. might as well be incorporated. Most of technology is in hand, but need some prototyping. A design note by May, 2000 ? Cost estimation ? We are hoping to construct PRISM by the time when the 50-GeV PS will be on.

Summary PRISM experience is important towards a neutrino factory at the 50- GeV PS. If the 50-GeV PS is given, a neutrino factory could be built cost-effectively in future. A factor of about 20 is needed from PRISM intensity to achieve 2x10 20 /year. – a factor of 5 from the 50-GeV PS upgrade in Phase-II – some modest efforts in improvement of muon yield – a larger detector (cheeper than acceleraor) Quick start should be aimed with reasonable performance. – optimize just or a neutrino factory, and do not aim too high for a muon collider.