PSI Muon Experiment at the PSI, KEK RCNP, 23-24.Feb.2010, RCNP
2 Contents PSI? Muon Beam Line in PSI Muon Experiment in PSI past / present (MEG) Future Prospects in PSI
PSI?
4 PSI : Paul Scherrer Institut Largest Swiss Federal Institute for a lot of Scientific research activities. Mainly based on proton cyclotron and nuclear reactor because this institute was merged by two institutes in 1988: SIN : Swiss Institute for Nuclear Research EIR : Federal Institute for Reactor Research PSI something similar with combination of KEK and JAEA in Japan PSI is a member of ETH domain (ETHZ, EPFL); for not only Particle- Nuclear but also Structure of Matter, Energy & Environment, and Health. However, according to its prestigious history of powerful cyclotron, PSI is still referred as Mecca of Meson Factory like TRIUMF, LAMPF, RAL.
5 PSI and its Cyclotron Facility Hajime NISHIGUCHI (KEK) Muon Experiment at PSI RCNP研究会: ミューオン科学と加速器研究, 23-24.Feb.2010, RCNP
6 PSI Proton Cyclotron The cyclotron facility contains a cascade of three accelerators that deliver a proton beam of 590 MeV energy at a current up to 2 ma (1.2 MW). Pre-accelerated in a C-W column to an energy of 870 kev, secondaryaccelerated in the 4-sector Injector 2 cyclotron up to 72 MeV. Final acceleration of the main beam to 590 MeV occurs in the large 8- sector Ring Cyclotron, from which the beam is transported through the experimental hall in a shielded tunnel.
Experimental Facility with 2nd-beamlines 7 The main beam passes through two pion production targets whereby the proton energy is reduced to 570 MeV. Target-M (5mm C) πm1 isotope prod. μe4 Target-E (40mm C) πe1 After passing through the targets the beam can either be dumped in a beam stopper or can be recaptured and bent downwards through a sloping drift tube for onward transport to the SINQfacility. proton therapy πm3 πe5 πe3 μe1
Muon Beamline
9 As a Meson Factory PSI provides beam time for particle physics and other experiments. Its unique specialty is very high intensity pion and muon beams of momenta up to a few hundred MeV/c. Each beam line is designed for surface, subsurface, cloud, and low-e μsr muons, except for πm1. The world most intense DC muon beam (~10 8 muon/sec) is available. Two target station, M (thin, 5 mm C) and E (thick, 40/60 mm C), are equipped; Two beam lines are attached with Target-M and Five beam lines are attached with Target-E. One beam line is used for test beam purpose, Three beam lines are exclusively used for μsr, and Three beam lines are used for Particle/ Nuclear Physics experiments.
10 Target-M; πm1 and πm3 πm1 beam line πm3 beam line High resolution pion beam line with a momentum range between 100 and 500 MeV/c. The beam line contains an electrostatic separator built at CERN, which can reduce the proton contamination in a π + beam from 400% to about 5% at 300 MeV/c momentum. No "surface" muons available. Mainly used for the test-beam purposes. Currently the only beam line dedicated exclusively to μsr experiments with "surface" muons A 3 m long crossed-field separator can be used either as an electron/muon separator or as a muon spin rotator. After the separator the beam can be steered into one of two experimental areas; Low temperature facility LTF and a general purpose system GPS for μsr studies is installed.
11 Target-E; πe1, πe3, πe5, μe1 and μe4 Secondary Beam lines with Thick Target Station E πe1 πe3 πe5 μe1 μe4 High intensity pi/mu with momentum ranging 10-500 MeV/c. Surface muon is available. High intensity pi/mu with momentum ranging 10-250 MeV/c. Surface and Cloud muons. High intensity low momenta pi/mu ranging 10-120 MeV/c. The most intense surface muon. For an intense medium energy polarized muon beam, very low pion/electron contamination. Large acceptance beam line for low momenta muon (<40MeV/c), specially designed for Low-E μsr Was used by PiBeta. Is being used by PEN. Was used by Many muon programs. Is being used by MuSun, and being modified for high-b musr. Was used by SINDRUM. Is being used by MEG/LambShift Dedicated for μsr Dedicated for μsr
μ Experiments
13 Past Pion/Muon Experiments in PSI PSI has born the burden of fundamental physics for many decades; in particular precise measurement of pion and muon properties. Recently completed programs: Muonium-AntiMuonium conversion (MM) Search for Heavy Neutral Particle (KARMEN) Muon-Electron Conversion (SINDRUM-II) Improved Measurement of Charged Pion Mass T-violation in Muon decay Pion Beta-decay (PiBeta) Pionic Hydrogen (developments) Large Acceptance Detector System (LADS) (developments) F/B muon spectrometer at L3 (developments) Central Silicon Tracker at H1
Active Particle Physics Experiments in PSI 14 MEG and nedm : Flagship Projects in Particle Physics Division MuCap : Singlet Muon Capture on the Proton ntrv : Decay of Free Polarized Neutron LambShift in Muonic Hydrogen : to eliminate the contribution of the proton charge radius MuLan : τμ measurement (Improving the precision of G F ) FAST : τμ measurement (Improving the precision of G F ) PEN : Improving the accuracy of the π eν branching ratio. MuSun : Muon Capture on the Deuterium Detector Developments : Pixel barrel and ECAL for CMS
15 MEG Experiment Search Experiment for μ eγ μ eνν 100% (normal muon decay in SM) μ eγ violates Lepton Flavour Conservation Even assuming SM + Neutrino-Oscillation B(μ eγ) is assumed < 10-50 Many models of beyond SM, however, predicts large B(μ eγ) 10-15 -11 New experiment with a Sensitivity of B ~ 10-13 was proposed at PSI Two orders of magnitude better than current best limit (1.2 10-11 ) Cover the most of theoretically predicted region Physics data-taking started 2008 and is currently running.
16 Hunting for μ eγ Signal and Backgrounds Signal Prompt BG. Accidental BG. Clear 2-body kinematics (Ee =E γ =52.8MeV, θ eγ =180, Time Coincidence) Sensitivity is Limited by Accidental Overlap DC muon is the Best Solution How about in MUSIC??? Good Resolution (Energy, Spacial and Timing) under Very High Rate
17 Features of MEG The world most intense DC muon beam ~ 10 8 muon/sec at πe5 Liquid-Xenon photon detector Excellent Resolutions (E: 2%, T: ~70ps, X: ~5mm) Fast Response (Good for pile-ups) Uniform, Segment is not necessary Specially Degraded Magnetic Spectrometer Possible in 10 8 /sec intensity Very Light Tracker (0.002X0 in total) Very Fast Hodoscope array (~120ps) 1m -ray from muon decay
18 The 1st Physics Run, Run2008 Proposal was approved 1999, Construction was completed 2007. The 1st Physics Run 12/Sep. to 23/Dec. 2008. Right after the detector maintenance period, physics data taking started Several Sever Problems; Inefficient and Unstable operation of Spectrometer due to DC-HV discharge. Lower Light yield of Calorimeter due to Impurity in Liquid Xenon. Lower Trigger Rate due to lack of triggering counter (fibre counter). Integrated Stopped Muon on Target i.e. Lower Statistics than expected.
19 Run2008 : Analysis (Blinding) Eγ -ΔT eγ plane was used to determine Preselection, Analysis Box, and Blind Box. 16% of triggered events are pre-selected and 0.2% of events are blinded. Performances are estimated by Side-band. Reprocess was repeated several times with improved calibrations and algorithms. Final blinding box: ±1ns around Time-Zero
20 Run2008 : Analysis (Likelihood) 1189 events in Analysis Box Best Fit : 0 < Nsignal < 14.7
21 The 1st Results of MEG Single Event Sensitivity : 5 10-12 Expected NBG : 0.5 Evaluated by Sideband Average Sensitivity : 1.3 10-11 ToyMC with obtained PDF Best Fit : UL(Nsignal )=14.7 Obtained by Likelihood Upper Limit (90% C.L.) : B(μ + e + γ)<2.8 10-11 Preliminary Result of Run2008 was Published in hep-ex/0908.2594, and the final result of Run2008 will come soon in NPB.
22 Current Status of MEG 2009, the 2nd Physics Run was performed successfully Spectrometer Problem was solved!! Full Efficiency and Better Resolution. nb. All Digitizer replaced, Blighter Xenon, Still missing fibre counters Even Shorter Run period than 2008, the data amount is 2.2 times more than that we took 2008 because of recovered detector efficiency! Analysis & Detector Maintenance is Ongoing. The 2nd result will be published this summer. Aiming to finish Maintenance works by the end of April. Run-2010 will start ~May (after several commissioning and calibration runs), and will continue by Christmas shutdown. (First Long-term Run) MEG will continue to collect further more data (at least) 3 years in order to achieve 10-13 sensitivity.
Future Prospects
24 Next Flagship Projects in PSI (particle physics) Active muon experiments (only for particle physics!) are MEG, MuLAN/FAST, LambShift and MuCap/Sun Flagship project, MEG, will continue by 2012 at least. Recently the discussion has been arising for the future flagship project. Next flagship project should be discussed by following points: Should contribute for New Physics, not for just an Improvement Should be utilized for using the world most intense DC muon beam PSI cyclotron is still upgrading (2.2mA @ 2010, aiming 2.5-3mA) Currently there are three major discussions: New Muon EDM, MEG upgrades and μ eee
25 New Muon-EDM experiment Compact Storage Ring (<1m dia.) with adapting the frozen spin method Aiming dμ ~ 5 10-23 e cm, and confirm the tech. to achieve 10-25 in future cf. hep-ex/0606034 (experiment idea), PRL93.p052001 (frozen spin meth.)
26 MEG Upgrades ( Sensitive MEG & Polarized MEG ) It is possible to improve the current MEG sensitivity Xenon; High QE, Finer Granularity by using Smaller PMT (MPPC?) Spectrometer; Reduce Material more, Double Acceptance Expected Improvements; 10 times better sensitivity is possible Using Polarized Muon is very attractive Plastic target is currently used, thus ~100% depolarized Using Metal target can provide full polarization because πe5 is surfacemuon beam line. Measuring angular asymmetry of e + emission wrt. muon polarization will tell us the useful information to understand the New Physics. Asymmetry is distinguishable with 68% C.L. assuming B(μ eγ)>10-12.5 cf. Several Ideas for future improvement were presented in Workshop on Precision Measurements at Low Energy, 18-19.Jan.2007 at PSI
27 Search for μ 3e with a Sensitivity of 10-16 μ 3e has many more diagrams than μ eγ Present Upper limit; B(μ 3e) < 1.2 10-12 (SINDRUM-I, 22 years old!) Signature total energy, total momentum phase space distribution gives additional information if observed. in a constant B field the acceptance is defined by the pt Dominated threshold. by Background Accidental SINDRUM I µ 3e2ν accidentals DC muon is BEST How about in accidental background involves low invariant mass e+ e - MUSIC pairs produced??? by photons or by Bhabha scattering
28 PSI2010 Physics of fundamental Symmetries & Interactions Oct. 11-14, 2010 at PSI Continuation of the past Workshop; Precision Measurements at Low Energy, Jan. 18-19, 2007 at PSI as a contribution to an evaluation of the Future Particle Physics Research at PSI Future Particle Physics Research at PSI will be discussed in detail!!
29 Summary PSI has a powerful proton cyclotron and has been contributing to the fundamental particle physics as a Meson Factory The world most intense DC muon beam is available. Presently, 2.2mA (1.2MW) proton current and 10 8 muon/sec is provided. MEG experiment started 2008 and currently running in order to discover the first event of charged lepton flavour violation. In addition, several muon-experiment programs are running. Recently, the next particle physics program is being discussed. New muon EDM?, MEG upgrades (improved sensitivity and using polarized muon)?, μ 3e search experiment with a sensitivity of 10-16