Mesure du moment électrique dipolaire du neutron Oscar Naviliat-Cuncic LPC-Caen et Université de Caen Basse-Normandie Institut de Physique Nucléaire d'Orsay Mars 2005

2IPN - Orsay, 7 février 2005 O.Naviliat-Cuncic: plan context and motivation measurement principle the neutron beam technique UCNs and their sources present limit on the nEDM the new UCN source at PSI towards and improved nEDM measurement

3IPN - Orsay, 7 février 2005 O.Naviliat-Cuncic: context and motivation CP is known to be violated (K and B decays) The experimental results can (so far) be accommodated within the SM: quark flavor mixing (complex phase e -i in CKM-matrix) The CKM mechanism is too weak to account for the cosmological CP-violation (matter/anti-matter asymmetry of the Universe) At least one other mechanism EXISTS Our job (and duty) is to find it !

4IPN - Orsay, 7 février 2005 O.Naviliat-Cuncic: general principle Assuming CPT: CP-violation = T-violation In systems or processes without strangeness, the effects due to the CKM CP-violation are strongly suppressed (nEDM < ecm; beta decay correlations < ) New (e.g. SUSY) CP-violating mechanisms are generally enhanced Huge window to search for new physics! EDMs of quantum systems are very sensitive probes

5IPN - Orsay, 7 février 2005 O.Naviliat-Cuncic: permanent EDMs classical dipole interaction H = - (d ·E + ·B) observables - spin S, unit vector ŝ - magnetic dipole moment: = ŝ - electric dipole moment (d = qr) - for an elementary QM system: d = d ŝ transformations under T and P T: (d, ) (-d, - ) P: (d, ) (d, ) T: (E, B) (E, -B) P: (E, B) (-E, B) if d 0 then T and P are violated

6IPN - Orsay, 7 février 2005 O.Naviliat-Cuncic: EDM measurements upper limits have been obtained for: e,,, p, n,, atoms, molecules new projects and approaches are being considered for: e,, n, d, radioactive nuclei, atoms very active field ! complementary systems

7IPN - Orsay, 7 février 2005 O.Naviliat-Cuncic: neutron EDM (A.P. Serebrov, NIM A440 (2000) 653) Systematic effects have continuously been fought experimental advantages: no electric charge long lifetime storage of UCNs

8IPN - Orsay, 7 février 2005 O.Naviliat-Cuncic: measurement principle Ramsey method of Separated Oscillating Fields prepare a sample of polarized neutrons make a /2 spin flip (start clock) allow free spin precession in parallel B and E static fields make a /2 spin flip (stop clock) analyze direction of neutron spin Free precessio n... Apply /2 spin flip pulse... Spin up neutron... Second /2 spin flip pulse. B E energy (frequency) shift under field inversion: = h | | = 4Ed n

9IPN - Orsay, 7 février 2005 O.Naviliat-Cuncic: beam technique with cold neutrons (W.B. Dress et al. Phys. Rev. 170(1968)1200) v n 100 m/s P n 70% B 10 G

10IPN - Orsay, 7 février 2005 O.Naviliat-Cuncic: beam technique result (W.B. Dress et al. Phys. Rev. 170(1968)1200) final: d n = (0.4 ± 1.5) × ecm (W.B. Dress et al. Phys. Rep. 43(1978)410) new techniques required for further improvements!

11IPN - Orsay, 7 février 2005 O.Naviliat-Cuncic: what are Ultra-Cold Neutrons ? definition: neutrons which are reflected at any angle of incidence (the neutron kinetic energy is smaller than the Fermi potential of the surface) n 800 Å ; v n 5 m/s T n 2 mK ; E n 130 neV

12IPN - Orsay, 7 février 2005 O.Naviliat-Cuncic: the UCN source at ILL the only operating source in the world high flux reactor (thermal power: 58.3 MW) thermal n-flux: 1.5 × n/s/cm 2 cold neutron source: 20 l of LD 2 at 25K vertical neutron guide 13m, 7×7 cm 2, ( 58 Ni coated) UCN source: rotating turbine UCN density: = 20 /cm 3

13IPN - Orsay, 7 février 2005 O.Naviliat-Cuncic: …in real life

14IPN - Orsay, 7 février 2005 O.Naviliat-Cuncic: Sussex-RAL-ILL experiment (P.G. Harris et al. PRL 82(1999) 904) V = 20 l B = 10 mG, L = 30 Hz E = kV/cm T = s use of 199 Hg co-magnetometer d( 199 Hg) < 8.7 × ecm

15IPN - Orsay, 7 février 2005 O.Naviliat-Cuncic: Sussex-RAL-ILL result (P.G. Harris et al. PRL 82(1999) 904) d n = (-3.4 ± 3.9 ± 3.1)× ecm

16IPN - Orsay, 7 février 2005 O.Naviliat-Cuncic: statistical sensitivity (d n ) = 5× ecm / 50 days cycle optimal sensitivity (with 50% running efficiency) (d n ) = 15× ecm / 50 days cycle current sensitivity (UCN losses and depolarization) : slope on resonance curve T : free precession time E : electric field strength N : total number of detected neutrons (N ~ V t mes )

17IPN - Orsay, 7 février 2005 O.Naviliat-Cuncic: towards a new experiment larger UCN densities will be available at the PSI UCN source (more than two orders of magnitude) a sensitivity improvement of the nEDM at the level of ecm is realistic systematic effects must be suppressed below the sensitivity level improved magnetometry for control of fields and gradients resonance frequency derived from active magnetometry build a multiple chamber system develop a UCN velocity dependent detection system

under construction the Spallation UCN source at PSI

19IPN - Orsay, 7 février 2005 O.Naviliat-Cuncic: UCN source at PSI 590 MeV, 2 mA, proton beam pulsed: 4 s ON/ 600 s OFF (low duty cycle) spallation target: Pb moderators: D 2 O (20-80 K) UCN source: SD 2 (30 l, 8K) volume: 2 m 3 (Be coated: v L = 6.9 m/s) expected density: = 3000 /cm 3

20IPN - Orsay, 7 février 2005 O.Naviliat-Cuncic: approach UCN polarisation UCN detection / polarimetry coatings double chamber magnetometry study performance and operate the Sussex-RAL-ILL apparatus implement improvements including magnetometry upgrade apparatus to accommodate a multiple chamber design a new spectrometer best adapted to the PSI UCN source

21IPN - Orsay, 7 février 2005 O.Naviliat-Cuncic: UCN polarization (measurements by PNPI; compare with PSI annual report) objectives: improve P n : (0.9 to 1) increase available UCN density implementation: separate polarization from analysis magnetized foils SC solenoid

22IPN - Orsay, 7 février 2005 O.Naviliat-Cuncic: UCN detectors and spin analysis objectives: improve detection efficiency / measurement duty cycle improve analyzing powers implement velocity selectivity tests and implementation: compare performance of alternative detectors with 3 He develop spin analyzers

23IPN - Orsay, 7 février 2005 O.Naviliat-Cuncic: UCN counters Si/LiF/Si sandwich: 380 m/ 600 g/cm 2 / 380 m (Gatchina) (Heidelberg) hybrid solid/gas detector: CASCADE 6 Li doped glass scintillator (Caen)

24IPN - Orsay, 7 février 2005 O.Naviliat-Cuncic: GS10 test and spin analysis pulse height spectrumtransmission asymmetry Detector turbine spin flipper polarizeranalyzer chopper GS10

25IPN - Orsay, 7 février 2005 O.Naviliat-Cuncic: coatings (DLC) developed reliable DLC characterization large area coatings with high critical velocity, low losses and depolarization Pulsed Laser Deposition (PLD) of DLC presently being optimized PLD for UCN guide tubes under construction UCN transmission through coated Al foil

26IPN - Orsay, 7 février 2005 O.Naviliat-Cuncic: magnetometry objectives: measure magnetic field and magnetic field gradients active internal/external field stabilization generation of resonance frequency tests and implementation: compare Cs LOPMs with 199 Hg vapor magnetometers develop OPMs sensitive to field components

27IPN - Orsay, 7 février 2005 O.Naviliat-Cuncic: self-oscillating laser pumped cesium magnetometer magnetic resonance + optical preparation & detection 1 magnetometer (OPM) needs 25 W 1 laser delivers >10 mW 1 laser = many sensors

28IPN - Orsay, 7 février 2005 O.Naviliat-Cuncic: magnetic field fluctuations in a multi-layer shield field not stabilized field stabilized residual gradient fluctuations >40 fT coil current OPM 1 OPM 2 2 OPMs - Co-Netic - Mu-Metal

29IPN - Orsay, 7 février 2005 O.Naviliat-Cuncic: multiple field measurement inside the ILL-EDM setup HV electrode vector magnetometers neutron chamber

30IPN - Orsay, 7 février 2005 O.Naviliat-Cuncic: status and plans : R&D at ILL and design of new setup 2007: start operation of PSI source, commissioning : measurement (1st phase) : measurement (2nd phase)

G. Ban, X. Fléchard, M. Labame, Th. Lefort, E. Liénard, O. Naviliat-Cuncic, G. Rogel Laboratoire de Physique Corpusculaire, Caen, France K. Bodek, St. Kistryn, M. Kuzniak, J. Zejma Institute of Physics, Jegellonian University, Cracow, Poland D. Mzhavia, B.M. Sabirov Joint Institute of Nuclear Reasearch, Dubna, Russia S. Gröger, P. Knowles, M. Rebetez, A. Weis Departement de Physique, Universit é de Fribourg, Fribourg, Switzerland C. Plonka Institut Laue-Langevin, Grenoble, France G. Quéméner, D. Rebreyend, Ch. Sage, U.C. Tsan Laboratoire de Physique Subatomique et de Cosmologie, Grenoble, France T. Brys, M. Daum, P. Fierlinger, R. Henneck, S. Heule, M. Kasprzak, K. Kirch, A. Pichlmaier Paul Scherrer Institute, Villigen, Switzerland