P and T violating correlation in muon and beta decays

2. P and T violating correlationin muon and beta decays Oscar Naviliat-Cuncic LPC-Caen (IN2P3/CNRS-ENSI) and Université de Caen Basse-Normandie

3. context and plan describe some searches for signatures of NP in weak decays, specifically sensitive to P and/or T violation • CP-even, P-odd correlation (muon decay) • CP-odd, P-odd correlation (neutron decay)

4. 1. The longitudinal e+ polarizationin polarized muon decay (initially motivated by the sensitivity of P -/P + measurements in nuclear beta decay)

5. nm ne GF m e • beyond SM: include all Lorentz invariants • decay amplitude parametrized by • in the SM (all others are zero) m-decay phenomenology 4-fermions point-like interaction: (W.Fetscher PLB 173(86)102) g = S,V,T interactions e,m = L,R helicity of charged fermions

6. parameterization of observables Observables commonly expressed in terms of Michel parameters: status the parameter x’’ enters the angular/energy dependence of PL by the combination: (present PDG value)

7. q PL Pm e+ m+ longitudinal e+ polarization sensitivity vs x and q for Pm = 0.95 x = Ee /E0 reduced positron energy → measure near q = p and x = 1 relation to exotic couplings

8. relative measurement compare e+ polarizations between polarized and unpolarized muons: avoids the precise determination of the polarimeter analyzing power sensitivity coefficient: r -, r 0: rates of positrons incident on the polarimeter for polarized and unpolarized muon decays (measured) implementation • produce polarized muons • maintain/destroy the muon polarization • select backward emitted positrons near the end point • measure the longitudinal polarization

9. realization pE3 area muons are naturally produced 100% polarized from pion decay at rest “surface muons” (contamineted by “cloud muons”)

10. 28.9 MeV/c m+ > 44 MeV/c e+ Spectrometer Polarimeter Wien filter (B < 0.0004 T) monitor telescopes Al or S target experimental setup e+/m+ velocity separation N(e+)/N(m+) < 0.12 m stop rate: 3x107 s-1 at 1.6 mA

11. muon polarization Hanle method (with two plastic telescopes) polarization vs muon momentum “surface muons” at 28.5 MeV/c: Pm = 0.94(1) use two muon stop targets: Al: Pm = 0.94 “polarized” S: Pm = 0.10 “unpolarized”

12. 1.9T 2.7T 0.8T energy and angular selection selector tracker refocus pe = 50 MeV/c 60% transmission for Ee > 44 MeV 12 < q < 13 dump of beam positons pe = 29 MeV/c

13. 1 2 3 2 e+ 1 z 3 d12 d23 silicon tracker determine momentum from helix geometry redundancy constraint! - 3 planes with 4 detectors each - 60x60 double SSD 1 mm pitch 300 mm thick resolution Dpe = 1.15(1) MeV/c

14. Hodoscope WC BGO WC scintillator Vacoflux foils with opposite magnetization positron polarimeter use two processes: - Bhabha scattering - Annihilation in flight (have analyzing powers with opposite signs) BHA: Aeff ~ 0.037 AIF: Aeff ~ -0.015 (incl. fraction of polarized electrons and foil orientation) but similar FOM (luminosity) CoNiFe foils: 75x15x0.1 cm3 with 0.75mm active region to reduce Brehmstralung events

15. hodoscope and calorimeter • 7x7 plastic scintillators (x and y) • 90x7 cm2 with single PM readout • 127 BGO crystals, 55mm diam, 20cm long • external magnetic shielding • temperture stabilized DT = ±2° • resolution DE/E = 10% at 42 MeV

16. measuring conditions • two magnetized foils with opposite magnetizations (simultaneous) • two directions of magnetization for each foil • two orientations of the polarimeter: +45°, -45° • two analyzing processes with opposite analyzing powers (BHA, AIF) • two stop targets for polarized and unpolarized muons • measure energy dependence of the longitudinal polarization typical trigger rates: • total 15 kHz • AIF 60/s • BHA 250/s (consistent with MC simulations)

17. cluster recognition, event reconstruction,cuts, ratios, asymmetries… • triggers defined from scintillators and BGO • SSD readout is slave • event type sorted from hits in MWPCs, Hodoscope and BGO

18. preliminary results (X. Morelle, PhD) asymmetries of ratios under inversion of foils magnetization PRELIMINARY! x” = 1.020 ± (0.062)stat ± (…)sys (factor of 6 improvement if sys remains negligible)

19. status • experiment did not acquired the planned statistics • no present plans to make a new run

20. people and institutions J.Egger, N.Danneberg, J.Deusch, W.Fetscher, F.Foroughi, J.Govaerts, M.Hadri, Ch.Hilbes, K.Kirch, P.Knowles, K.Koehler, A.Kozela, J.Lang, M.Markiewicz, R.Medve, X.Morelle, O.Naviliat-Cuncic, A.Ninane, R.Prieels, L.Simons, J.Sromicki and P.Van Hove • Institut de Physique Nucléaire, UCL, Louvain-la-Neuve, Belgium • Institut für Teilchenphysik, ETH, Zurich, Switzerland • Paul Scherrer Institut, PSI, Villigen, Switzerland • Département de Physique, Uni-Fribourg, Switzerland • Laboratoire de Physique Corpusculaire, Caen, France (thanks to R.Prieels)

21. related projects TRIUMF Weak Interaction Symmetry Test: “TWIST” http://twist.triumf.ca/~e614/experiment.html tracking of e+ from polarized muon decay goal: detemine r, d, Pmx with a relative precision at the 10-4 level prelim. results expected in 2004

22. 2. Measurement of the R parameterin neutron decay

23. Jn Pp e pe p the R coefficient decay rate function: • the coefficients A, R, N, … probe the dynamics • JTW parameterization: Ci , C’i(i = S, V, A, T )

24. R and D in neutron decay D: P-even T-odd R: P-odd T-odd DFSI = 1.310-5 (10-6) RFSI = 910-4 (510-6)

25. Jn Pp e pe p measuring principle highest sensitivity to R for mutually perpendicular vectors Mott scattering

26. experimental concept (J. Sromicki NIM A 440 (2000) 609) • produce polarized cold neutron beam • observe neutron decay in flight • track low energy decay electrons • use large angle Mott scattering • trigger with “opposite” scintillator

27. realization • Spallation neutron source SINQ • target: “zircalloy” (Zr-Pb) • D2O moderator • liquid D2 vessel cold source FUNSPIN area

28. polarized cold neutron beam • A. Schebetov et al. • NIM A 497 (2003) 479 • J. Zejma et al. • to be submitted to NIM A • flux: 2×108 /(cm2·s·mA) • ‹P› ≈ 97 % FUNSPIN area

29. scheme of the experimental setup

30. photo gallery MWPC HODOSCOPE DECAY REGION

31. results from commissioning run • Energy spectra of electrons from single track events S/B > 3:1

32. Mott scattering analysis cross section and Sherman function in Au … Pb is better (higher Z) and cheaper! - 1mm evaporated Pb layer on 2mm mylar - 2 or 3 bands for 50x50cm2 active surface

33. a “golden event”

34. vertex reconstruction (A. Kozela) positions of Pb scattering foils

35. vertex signals • after vertex reconstruction with VETO condition on • the hodoscope at the vertex side S/B > 10:1 • inclusion of hot spots of the setup geometry is in • progress to further improve S/B

36. comments 2. precision goal:R =510-3 1. polarimetry control • “up-down” asymmetry probes R • “left-right” asymmetry probes N the simultaneous measurement of N ≠ 0 provides a control of the polarimeter Exclusion plot on S and T frombeta decay experiments (±1s)

37. interpretation P. Herczeg 2004: constraints on |Im(aLS)| from Rp are hard to beat with Rn Rn at 10-2 would require fine-tuned cancellations → make life less exciting… … important considerations for new generation experiments

38. status and outlook • The Mott polarimeter for the measurement of R in neutron decay • is complete. • The commissioning run in autumn 2003 was successful. • The first data taking run starts next month. • The measurement of R with an accuracy of 10-2 is expected to be achieved within one year. • The sensitivity goal of 510-3 seems feasible; • will be checked after first complete data analysis.

39. people, institutions, support G.Ban, M.Beck, A.Bialek, K.Bodek, T.Brys, A.Czarnecki, W.Fetscher, P.Gorel, K.Kirch, St.Kistryn, A.Kozela, A.Lindroth, O.Naviliat-Cuncic, J.Pulut, A.Serebrov, N.Severijns, E.Stephan and J.Zejma • Laboratoire de Physique Corpusculaire, Caen • Institute of Physics, Jegellonian University, Cracow • Institute of Nuclear Physics, Cracow • University of Alberta, Edmonton • St Petersburg Nuclear Physics Institute, Gatchina • University of Silesia, Katowice • Catholic University Leuven, Leuven • Paul Scherrer Institute, Villigen • Institute of Particle Physics, ETH Zurich support for PhD students (thanks to K. Bodek and P. Gorel)