The PRISM project Akira SATO Osaka University Project X Physics - PowerPoint PPT Presentation

The PRISM project Akira SATO Osaka University Project X Physics Workshop at FNAL 9-10 November 2009

Outline • Limits for the COMET and Mu2e experiment • signal sensitivity • high-Z stopping material • PRISM concept • R&Ds • PRISM Task Force • Summary

Muon - Electron Conversion 1s state in a muonic atom Neutrino-less muon nuclear capture (= μ -e conversion) nucleus  + ( A , Z )  e  + ( A , Z ) µ µ  signal : m µ − B µ ∼ 105 MeV muon decay in orbit   e   µ nuclear muon capture  N ) =  ( µ  N  e  N )  + ( A , Z )   µ + ( A , Z  1)  N  e B ( µ µ  N   N  ( µ ' )

COMET and Mu2e(MECO-type): B ( µ − + Al → e − + Al ) < 10 − 16 Solenoid channel Production Target Stop µ - at the stopping targets. ID single electron from the target and measure its energy precisely. Stopping Suppress backgrounds strongly. Target Muon Calorimeter Stopping Target Tracker Target Muon Beam Shielding Proton Collimators Target Pions Electrons Muons Detector Solenoid Transport Solenoid Production The MECO type experiments have some limitation on achievable Solenoid sensitivity and physics studies.

Decay-in-Orbit Background BR~10 -16 • To distinguish the signals from the DIO backgrounds, electron energy must be reconstructed with sufficient resolution. The present resolution is dominated by the energy struggling in the stopping target.

Decay-in-Orbit Background (cont.) BR~10 -18 • To achieve a signal sensitivity < 10 -18 , we need improve the energy resolution. • Thinner stopping targets with a sufficient muon stopping efficiency is necessary. --> Mono-energetic muon beam is useful!

Target dependence of µ-e conversion Al Ti Pb • Once a signal of the µ-e conversion is observed, one can obtain information on 4 models of the new physics, by Z-like vector changing the target material, even if µ → e γ is not observed. (Z) 3 V • Contribution of different type of e;Al LFV operators is different from B each nuclei. e;Z 2 • Maximal in the intermediate Photon-like vector B nuclei • Significantly Different Z V ( γ ) Photonic dipole dependence for heavy nuclei 1 D • BUT, higher Z target makes S shorter µ lifetime in a muonic Higgs-like scalar atom. 0 20 40 60 80 • Al : 880ns, Ti ： 329ns, Pb : 82ns Z V.Cirigliano et al, Phys. Rev. D 80 013002 (2009)

Time distribution of backgrounds and signal 100 ns • The muons stopped in the muon- Al Main Proton Pulse 8 10 p/pulse stopping target have the lifetime of a Prompt Background muonic atom. The time distribution Arbitrary Unit of muon decays with the distribution Stopped Muon Decay of muon arrival timing is shown in Timing Window Signal Figure. • Huge prompt BG exists just after the 0 1 ( µ s ) Time 1.1 µ s prompt timing. BUT Some beam- high-Z related backgrounds would come 100 ns Main Proton Pulse even after the prompt timing. 8 10 p/pulse Therefore, the measurement time Prompt Background Arbitrary Unit window is selected to start after the Stopped Muon Decay prompt timing. • The time window acceptance depends on the muon lifetime. 0 1 ( µ s ) Time 1.1 µ s 0 T 1 T p

Timing window selection efficiencies for COMET t 1 =700ns, T p =1314ns Al ( τ =864ns) Ti ( τ =330ns) Au ( τ =88ns) µ µ - - Decay Time: Aluminum, PPW=100ns h6 h6 Decay Time: Titanium, PPW=100ns h6 h6 µ - Entries Entries 532100 532100 Entries Entries 532100 532100 Decay Time: Gold, PPW=100ns h6 h6 500 Number of Events (a.u.) Number of Events (a.u.) 240 Mean Mean 1054 1054 Mean Mean 519.7 519.7 Entries Entries 532100 532100 Number of Events (a.u.) RMS RMS 866.7 866.7 RMS RMS 345.3 345.3 Mean Mean 277.3 277.3 1000 220 Underflow Underflow 0 0 Underflow Underflow 0 0 RMS RMS 132.9 132.9 Overflow Overflow 3.462 3.462 Overflow Overflow 0 0 Underflow Underflow 0 0 200 Integral Integral Integral Integral 2.554e+04 2.554e+04 2.554e+04 2.554e+04 Overflow Overflow 0 0 400 Integral Integral 2.554e+04 2.554e+04 180 800 160 300 140 600 120 100 200 400 80 60 100 40 200 20 0 0 0 1000 2000 3000 4000 5000 6000 7000 8000 0 1000 2000 3000 4000 5000 6000 7000 8000 0 0 1000 2000 3000 4000 5000 6000 7000 8000 Time (ns) Time (ns) Time (ns) Timing Window Cut Efficiency: Aluminum, t1=700ns, PPW=100ns Timing Window Cut Efficiency: Titanium, t1=700ns, PPW=100ns Timing Window Cut Efficiency: Gold, t1=700ns, PPW=100ns 0.7 0.7 0.7 Efficiency Efficiency Efficiency effi. = 0.37 effi. = 0.20 effi. = 0.01 0.6 0.6 0.6 0.5 0.5 0.5 0.4 0.4 0.4 0.3 0.3 0.3 0.2 0.2 0.2 0.1 0.1 0.1 0 0 0 0 500 1000 1500 2000 2500 3000 0 500 1000 1500 2000 2500 3000 0 500 1000 1500 2000 2500 3000 Proton Pulse Interval (ns) Proton Pulse Interval (ns) Proton Pulse Interval (ns) To measure BR with a high-Z target, the beam related backgrounds (pion radiative decay, beam flash etc) must be highly suppressed.

Summary of limits for the MECO type experiments • A signal sensitivity < 10 -17 would be impossible with the MECO-type experiments. • large flux of prompt backgrounds. ex. pion radiative decay etc • thick stopping target makes insufficient electron energy resolution. • Measurement efficiency with high-Z stopping target would be poor.

Summary of limits for the MECO type experiments • A signal sensitivity < 10 -17 would be impossible with the MECO-type experiments. • large flux of prompt backgrounds. ex. pion radiative decay etc • thick stopping target makes insufficient electron energy resolution. • Measurement efficiency with high-Z stopping target would be poor. A mono-energetic and pure muon beam can solve these issues. The next generation µ-e conversion experiment with PRISM!

Further Background Rejection to < 10 -18 mono-energetic muon beam narrow muon beam Muon DIO & 1/10 thickness muon stopping spread Beam flush target pure muon beam Pion muon storage long muon beam-line ring background Beam-related Extinction at muon fast kickers Background beam Cosmic-ray 100 Hz rather low-duty running than 1 MHz background

PRISM : Phase Rotated Intense Slow Muon source High intensity intensity : 10 11 -10 12 µ ± /sec beam repetition :100-1000Hz kinetic energy : 20MeV(=68MeV/c) Narrow energy spread kinetic energy spread : ±0.5-1.0MeV Less beam contamination contamination < 10 -18 PRIME : PRIsm Muon to Electron Conv. Experiment sensitivity of µ → e ∼ 10 -18

To Make Narrow Beam Energy Spread • A technique of phase rotation is • Proton beam pulse should be adopted. narrow (< 10 nsec). • The phase rotation is to • Phase rotation is a well- decelerate fast beam particles established technique, but how and accelerate slow beam to apply a tertiary beam like particles. muons (broad emittance) ? • To identify energy of beam particles, a time of flight (TOF) from the proton bunch is used. • Fast particle comes earlier and slow particle comes late.

Japanese staging plan of mu-e conversion 2nd Stage : PRISM/PRIME 1st Stage : COMET Production Target Stopping Target B ( µ − + Al → e − + Al ) < 10 − 16 B ( µ − + Ti → e − + Ti ) < 10 − 18 • without a muon storage ring. • with a muon storage ring. • with a slowly-extracted pulsed proton beam. • with a fast-extracted pulsed proton beam. • doable at the J-PARC NP Hall. • need a new beamline and experimental hall. • regarded as the first phase / MECO type • regarded as the second phase. • Early realization • Ultimate search

2003-2009 Developed Capture Solenoid PRISM : Super-muon source PRIME : µ-N → e-N Search with PRISM • Intensity : 10 11 -10 12 µ±/sec, 100-1000Hz Matching Section • Energy ： 20±0.5 MeV (=68 MeV/c) Solenoid • Purity ： π contamination < 10 -20 Ejection System Injection System C-shaped FFAG Magnet FFAG ring Detector RF Power Supply RF Cavity RF AMP 5 m

PRISM-FFAG • Functions • makes monoenergetic muons ： phase rotation • reduces π in the beam ： long flight length • Requirements & R&D items • Large acceptance FFAG-ring • Horizontal ： 38000 π mm mrad • Vertical ： 5700 π mm mrad • Momentum ： 68MeV/c +- 20% • High field grad. RF system (170kV/m = 2MV/turn) • Quick phase rotation • ~1.5µs

6-sector PRISM-FFAG at RCNP, Osaka Univ.

PRISM Task Force • The PRISM-FFAG Task Force was proposed and discussed during the last PRISM-FFAG workshop at IC (1-2 July’09). • The aim of the PRISM-FFAG Task Force is to address the technological challenges in realizing an FFAG based muon-to- electron conversion experiment, but also to strengthen the R&D for muon accelerators in the context of the Neutrino Factory and future muon physics experiments. • It was proposed to achieve a conceptual design of the PRISM machine at the end of 2010/beginning 2011. •

PRISM Task Force (cont.) • The following key areas of activity were identified and proposed to be covered within the Task Force: • - the physics of muon to electron conversion, - proton source, - pion capture, - muon beam transport, - injection and extraction for PRISM-FFAG ring, - FFAG ring design including the search for a new improved version, - FFAG hardware R&D for RF system and injection/extraction kicker and septum magnets. • Please join! j.pasternak@imperial.ac.uk