Low Energy Fundamental Precision Experiments at PSI

1. Low Energy Fundamental Precision Experiments at PSI Andreas Knecht Paul Scherrer Institut & University of Zürich

2. Proton Accelerator Facility @ PSI MuLan/MuCap/MuSun FAST Lamb Shift n nEDM Not covered: MEG, PEN, →eee, EDM (see last year)

3. The Fermi Constant and  Fundamental parameters of electroweak Standard Model GFαMZ Precision (2008) 9 ppm 0.0004 ppm 23 ppm GFcontributes to all electroweak processes q QED corrections

4. The MuLan Experiment at PSI PSI DC proton beam with 1.7 mA → 10 MHz m+ Final analysis under way(several 1012 decays) electrostatic kicker -12.5 kV 12.5 kV

5. The FAST Experiment at PSI Plastic wedge beam degrader to achieve a uniform beam distribution inside the target → Final data taking under way (2009) Goal: a few 1011 full decay events

6. The Fermi Constant and  • tm(MuLan) = 2.197 013(21)(11) ms (11ppm) Phys. Rev. Lett. 99, 032001 (2007) • tm(World) = 2.197 019(21) ms (9.6 ppm) • →GF = 1.166 371(6) x 10-5 GeV-2 (5 ppm) • tm(FAST) = 2.197 083(32)(15) ms (15ppm) Phys.Lett. B 663, 172 (2008) Precision goals: MuLan tm= 1 ppm ~ 0.5 ppm GF FAST tm= 2 ppm ~ 1 ppm GF MuLAN MuLAN

7. Muon Capture on the Proton and the Pseudoscalar Formfactor gP charged current ‘historically’ V-A structure JN = <n|Va- Aa |p> Lorentz invariance allows 6 terms and couplings in the nucleon charged current Va= gV(q2) + igM(q2)/2M sab qb + gS(q2)/m qa Aa= gA(q2) g5 + gP(q2) qa/m g5+ igT(q2)/2M sab qbg5 Nucleon weak form factors gV, gM, gAare determined by SM symmetries and data. They contribute < 0.5% uncertainty to capture rate but gP = 8.3 ± 50% (before 2007)

8. Lifetime method 10-3 effect e – e+ log counts time MuCAP Experiment Main contributions from PSI, University of Illinois Urbana-Champaign, PNPI, et al.

9. SMuCap = 725.0  13.7 (stat)  10.7 (sys) s-1 MuCap, PRL 99, 032001 (2007) Stheory = 710.6 s-1Czarnecki, Marciano, Sirlin, PRL 99,032003(2007) - + p  m + n + g gP after MuCAP 07 result gP = 7.3 ± 1.1

10. MuCAP Goal for Final Analysis Ongoing analysis of 1010 mu-e events to reduce the error on ΛS to < 1% and on gP to < 7%

11. gas liquid { Muon Capture on the Deuteron m- + d  n + n + n (doublet capture rate Λd) World knowledge on Λd is not satisfying Goal of the MuSUN experiment at PSI is to measure muon capture rate Λdto < 1.5 % MuSUN footed on experience within MuCAP and MuLAN, but needs to develop new cryo-TPC for 30 K measurement. First engineering runs completed

12. Connection to Neutrino/Astrophysics EFT connection to +d capture via a single LowEnergy Constant L1A Basic solar fusion reaction:p + p  d + e+ +  Key reactions for SNO: e + d  p + p + e- (CC) x + d  p + n + x (NC)

13. Present Knowledge on L1A Goal of the MuSUN experiment at PSI is to measure muon capture rate Λdto < 1.5 % Allows to extract L1A to ~1.5 fm3 Ld(L1a) L1A(fm3)

14. Laser-spectroscopic experiment @ PSI proton accelerator facility Lamb Shift in Muonic Hydrogen • highly sensitive to rms proton charge radius rp • rp is not well known (+/- 2% uncertainty) • rp is a fundamental CODATA-constant • test bound-state QED. • improve Rydberg constant 6-fold

15. Experiment: APDs as X-ray detectors: • mup(2P-1S) @ 1.9 keV • time resolution 30 ns • energy resolution 25% • work in B = 5 Tesla Multi-stage laser-system: • 6 µm wavelength well • determined • tunable and fast • stochastically triggerable Unique muon beam: ~ 1000 µ- @ 10 keV Beam time 2009 finished successfully. Brand new result currently under refined analysis. Goal for precision on rP: 0.1% Future: → µHe and µD @ PSI → further refinement of QED-tests with new experiments with exotic atoms

16. PSI UCN Source Beam dump • Commissioning starts fall 2009 • Expect 1000 UCN/cm3 in typical experiments (compare to currently 10 UCN/cm3 at ILL) n nEDM

17. nEDM @ PSI • Phase I: • Operate and improve Sussex-RAL-ILL apparatus at ILL • R&D for n2EDM • Move to PSI March 2009 • Phase II: • Operate Sussex-RAL-ILL apparatus at PSI (2009-2012) • Sensitivity goal: 5x10-27ecm • Construction and setup of n2EDM • Phase III: • Operate n2EDM (2012-2015) • Sensitivity goal: 5x10-28ecm

18. nEDM @ PSI

19. EDM ready for UCN

20. Neutron Lifetime Puzzle New proposal to PSI: PENeLOPE neutron lifetime measurement New improved neutron lifetime experiments of high priority: Aim at 0.1s precision

21. Conclusions • Several experiments being performed at PSI in fundamental particle physics. • Precision experiments at low energies complement the high energy experiments in the searches for physics beyond the SM. • Several new and exciting results to be expected in the coming years. Special thanks to C. Casella, K. Deiters, K. Kirch, F. Kottman, B. Lauss,T. Nebel and R. Picker for their contributions.

22. Backup

23. 1 % LH2 100% LH2 pm ppμ ppmO ppμ pm ppmO ppmP ppmP time (ms) p-m-p kinetics in hydrogen LT= 12 s-1 triplet (F=1) pμ↑↑ Lortho=506s-1 Lpara=200s-1 λop μ ppμ ppμ f λppm ortho (J=1) para (J=0) • Interpretation requires knowledge of ppm population • Strong dependence on hydrogen density f pμ↑↓ singlet (F=0) populations of states LS= 710s-1 n+n MuCap

24. Muon-catalyzed Fusion lq lqd ld Muon Kinetics in deuterium Collisional processes density f dependent, e.g. hfs transition rate from q to d state = flqd densityf normalized to LH2 density md() md md() m3He MuSun