Muon Beams for Particle Physics Ajit Kurup Winter Seminar March 2010

Page 2 Muon Beams for Particle Physics Winter Seminar March 2010Ajit Kurup Introduction “Muon Beams for Particle Physics” means –Accelerator challenges for muon to electron conversion experiments. Brief introduction to particle physics. Talk about proposed muon to electron conversion experiments. –Concentrate on COMET and PRISM. Design and technology issues. Some results from 6-cell PRISM test ring. Summary and future plans.

Page 3 Muon Beams for Particle Physics Winter Seminar March 2010Ajit Kurup The Big Picture Standard Model of particle physics

Page 4 Muon Beams for Particle Physics Winter Seminar March 2010Ajit Kurup The Bigger Picture We know the SM is at best incomplete. –Does not include gravity. –Certain predictions diverge with increasing energy. Neutrinos in the SM are massless but observation of neutrino oscillations is direct evidence that neutrinos have mass. –First observation from Super Kamiokande Possibility of Charged Lepton Flavour Violation (Lepton flavour number is not conserved).  -  e -   -  e - e + e -  - (A,Z)  e - (A,Z) ? ?

Page 5 Muon Beams for Particle Physics Winter Seminar March 2010Ajit Kurup Muon to Electron Conversion Neutrino-less conversion of a muon into an electron in the presence of a nucleus Look at muonic atoms –muon decay  -  e - e  –nuclear capture  - (A,Z)   (A,Z-1) –muon to electron conversion  - (A,Z)  e - (A,Z) If we include neutrino mixing in the SM, the probability for muon to electron conversion is about –Sensitive to physics beyond the SM. SM processes

Page 6 Muon Beams for Particle Physics Winter Seminar March 2010Ajit Kurup SUSY and GUTs

Page 7 Muon Beams for Particle Physics Winter Seminar March 2010Ajit Kurup Measuring Muon to Electron Conversion SUSY and other models give predictions > Design an experiment that has a sensitivity of –This means being able to identify one electron of interest from muons not of interest! Signal is a monoenergetic electron –E = ~ 105 MeV = m  - BE Need to eliminate sources of backgrounds. –Muon decay in orbit –Muon decay in flight –Radiative muon capture  - (A,Z)   (A,Z-1) *, (A,Z-1) *  (A,Z-1) ,   e + e - –Radiative pion capture  - (A,Z)  (A,Z-1) *, (A,Z-1) *  (A,Z-1) ,   e + e - –Cosmic rays

Page 8 Muon Beams for Particle Physics Winter Seminar March 2010Ajit Kurup Future Muon to Electron Conversion Experiments The COherent Muon to Electron Transition (COMET) experiment will be based at J-PARC and aims to have a sensitivity < The Phase Rotated Intense Slow Muon (PRISM) experiment will improve this measurement by a factor of 100 and can be the second phase of COMET. Mu2e aims to have a sensitivity of < and will be based at FERMILAB. COMET PRISM Mu2e

Page 9 Muon Beams for Particle Physics Winter Seminar March 2010Ajit Kurup Why You Might Be Interested Need for high intensity muon beam  Many challenges from an accelerator physics perspective. Intense proton beams. Very cleanly pulsed proton beam (extinction <10 9 ). –AC Dipole. Pion production. –Superconducting solenoid in high radiation environment. Muon beams. –Transportation and momentum selection of large emittance beams. Fixed-Field Alternating-Gradient (FFAG) accelerators. –Large momentum acceptance. –High gradient at low frequency cavities. –Kickers.

Page 10 Muon Beams for Particle Physics Winter Seminar March 2010Ajit Kurup COMET at J-PARC Beam Power56 kW Beam Energy8 GeV Average Current 7A7A Protons per Bunch<10 11 Proton beam parameters Slow-extracted proton beam. 8 GeV to suppress anti- proton production. COMET requires lower power but PRISM will need 1-2MW. Hadron Experimental Facility Materials and Life Science Facility 3 GeV Synchrotron Linac 50 GeV Synchrotron Neutrino Facility Accelerator-Driven Transmutation Experimental Facility COMET

Page 11 Muon Beams for Particle Physics Winter Seminar March 2010Ajit Kurup COMET Overview Curved solenoid channel to allow pions to decay and momentum selection of muons. Stopping target made of 0.2mm thick Aluminium disks. Electron spectrometer is another curved solenoid channel for momentum selection of electrons. Tracker utilises straw tubes arranged in planes for precise momentum measurement. Calorimeter is made of scintillator crystals for energy and time measurements. Magnetic Field (T) z (mm)

Page 12 Muon Beams for Particle Physics Winter Seminar March 2010Ajit Kurup Proton Beam for COMET Background rate needs to be low in order to achieve sensitivity of < Need proton extinction device. Bunch Separation 1-2  s Bunch Length100ns Extinction10 -9 Pulse Structure

Page 13 Muon Beams for Particle Physics Winter Seminar March 2010Ajit Kurup Proton Extinction Extinction requirement is Intrinsic extinction from the J-PARC main ring is expected to be around –Need additional extinction device to give additional factor One possible solution is to use an AC dipole –Collaboration between COMET and Mu2e B=0G - G4Beamline TRANSPORT B=600G - G4Beamline TRANSPORT B=600G B=0G 1300ns 100ns f=385kHz Transmission [-100:100ns] = 100% R extinction [ 300ns] < 1/1000 R extinction [ 200ns] < 1/100

Page 14 Muon Beams for Particle Physics Winter Seminar March 2010Ajit Kurup Pion Production Keep only backward going pions. Gold target simulations using MARS

Page 15 Muon Beams for Particle Physics Winter Seminar March 2010Ajit Kurup Solenoid Design 8x10 21 n/m 2 /10 21 p 2x10 -5 DPA/10 21 p Neutron Flux Neutron Flux: –~10 22 n/m 2 for p Same criteria as for ITER –~2x10 -5 DPA for p Conductor degradation Inner bore of solenoid increased to 1300mm. Copper stabilised conductors are thick. –Refrigeration load over 1kW. Aluminium stabilised superconducting coil R&D. –Better radiation damage performance. Prototype being wound at Fermilab.

Page 16 Muon Beams for Particle Physics Winter Seminar March 2010Ajit Kurup Muon Transport Channel Needs to be long enough so pion survival rate is low, <10 -3 High transport efficiency for muons with momentum around 40 MeV/c Eliminate muons with momentum > 75 MeV/c Select muons with negative charge. Use toroid magnetic field. –Particles drift in direction perpendicular to curvature Need compensating dipole field to correct for this. At the end of the muon transport channel

Page 17 Muon Beams for Particle Physics Winter Seminar March 2010Ajit Kurup Muon Transport Magnet Designs Tilted solenoid coils. Actual tilt angle is 1.43deg. tilt angle Double Helix from Advanced Magnet Labs. Additional dipole field windings on top of solenoid winding. Windings can be formed on a bent substrate. Additional cosine theta coils to give dipole field.

Page 18 Muon Beams for Particle Physics Winter Seminar March 2010Ajit Kurup PRISM Factor 100 improvement in sensitivity on COMET. Longitudinal phase-rotation from  p/p = ± 20% to ± 2% Scaling FFAG. Small momentum spread means stopping target can become thinner (less degradation of electron momentum). Many turns  less pion contamination. rf : 2MV/turn

Page 19 Muon Beams for Particle Physics Winter Seminar March 2010Ajit Kurup Scaling FFAG has B z (r)= B 0 (r/r 0 ) k –Constant tune over momentum range. Recent revival because of need for fast acceleration of muon beams. What are FFAGs? Synchrotrons ramp up magnetic field to keep orbit fixed Y slow acceleration Low energy High energy D D F F F Orbit for all energies Magnetic fields are fixed Yrapid acceleration but orbits are more complicated Y complicated beam dynamics and larger magnets. Fixed Field Alternating Gradient Accelerator Synchrotron

Page 20 Muon Beams for Particle Physics Winter Seminar March 2010Ajit Kurup The PRISM Magnet Measured B z – TOSCA B z

Page 21 Muon Beams for Particle Physics Winter Seminar March 2010Ajit Kurup Magnetic Alloy RF Cavity High fields at low frequencies Wide band operation (low Q) Core made of magnetic alloy ribbon Cores per cavity4 Shunt Impedance 400  RF frequency2.1 MHz Field Gradient100 kV/m Duty Factor0.3% PRISM Prototype Cavity Sawtooth Approximation kV nsec 1.7m 1.0m 0.35m 1.0m 1.8m 0.33m

Page 22 Muon Beams for Particle Physics Winter Seminar March 2010Ajit Kurup PRISM Test Ring Use 241 Am alpha source (200 MeV/c degraded to 100 MeV/c with Al foil). Can locate position and angle of source. Study closed orbits, dynamic aperture and tune. 10-cell Ring6-cell Ring Particlemuonalpha Momentum (MeV/c)68100 Radius (m) Number of cavities81 Number of field clamps202

Page 23 Muon Beams for Particle Physics Winter Seminar March 2010Ajit Kurup 6-Cell PRISM Results

Page 24 Muon Beams for Particle Physics Winter Seminar March 2010Ajit Kurup PRISM Task Force So why not build PRISM instead of COMET? Number of issues need to be solved –Injection/extraction –RF gradient Technology being developed –Matching needs to be studied. –Can we use the same technology as the COMET muon beamline? A PRISM task force was set up in mid-2009 to address the issues for realising a feasible design. Utilise synergies with neutrino factory and other FFAG Projects.

Page 25 Muon Beams for Particle Physics Winter Seminar March 2010Ajit Kurup Summary and Future Plans COMET and PRISM are really exciting projects to work on! Fundamental science, the really “big” questions, can be addressed but requires the development of accelerator technology. –Intense, cleanly pulsed, proton beams. –Superconducting solenoid technology. –Transport channels for large emittance beams. –Radial-sector scaling FFAG magnet design. –Low frequency, high-gradient magnetic alloy rf cavities. –Kicker systems for FFAG Experiments –COMET has Stage-1 approval from J-PARC. Technical Design Report will be submitted by end of –PRISM task force will report by the end of 2010 / early –Mu2e has CD-0 from US Department Of Energy. Expects to get CD-1 approval in 2010.

Page 26 Muon Beams for Particle Physics Winter Seminar March 2010Ajit Kurup References COMET –“Conceptual design report for experimental search for lepton flavor violating mu- - e- conversion at sensitivity of 10**(-16) with a slow-extracted bunched proton beam (COMET).” By COMET Collaboration (Y.G. Cui et al.). KEK , Jun pp. –“J-PARC Accelerator Scheme for Muon to Electron Conversion Search”, EPAC08 PRISM –“FFAG as Phase Rotator for the PRISM Project”, EPAC04 –“Six-sector FFAG Ring to Demonstrate Bunch Rotation for PRISM”, EPAC08 Mu2e –Proposal –