Precision experiments with cold and ultracold neutrons

Transcription

1 Precision experiments with cold and ultracold neutrons Bochum, March 19th, 2009 Neutrons, cold & ultracold Precision experiments, fundamental physics Examples The polarization of neutron decay electrons: ntrv at PSI The neutron electric dipole moment: nedm at ILL and PSI The β-decay correlation: UCNA at LANL

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3 The Neutron +2/3-1/3 +2/3 +2/3-1/3 massive composite no net electric charge unstable spin ½, polarizable electric dipole: no, well electrically polarizable takes part in all interactions.. -1/3 3

4 Ultracold neutrons ideal gas with temperature of milli-kelvin move with velocities of few m/s strong magnetic gravitation Fermi potential V F V m = -µb V g = m n gh 200 nev 60 nev T nev m -1 E n < 200 nev V 3.3 T field 200 nev 2 m 200 nev 4

5 2 m 3 volume storage trap ρ ~ 2000 cm -3 UCN guide ρ exp > 1000 cm -3 vacuum compare with typical 10 cm -3 at ILL The PSI UCN source commissioning starts fall liters solid D 2 ρ UCN ~6000 cm -3 p-beam 1.2 MW Other UCN sources/projects ILL Grenoble LANL TRIGA Mainz RCNP Osaka TUM/FRM-II NCSU PNPI TRIUMF 3.6 m 3 D 2 O high power (1.2 MW) low duty cycle (1%) multi-user capability

6 Neutron experiment schematics Beam CN v CN ~ 1000 m/s t obs ~ 10-3 s ρ ~ cm -3 Storage UCN v UCN ~ 5 m/s t obs ~ s ρ ~ 10 cm -3 improved density at new UCN sources ρ ~ 1000 cm -3 6

7 `Fundamental physics Time reversal violation, CP-violation neutron electric dipole moment, EDM (topcite 336)* Quantum mechanics, spin physics single crystal interferometry (topcite 208)* topological phases (topcite 177)* Weak interaction, V ud, exotic couplings, TRV neutron decay (topcite 144)* Big-Bang-Nucleosynthesis, Weak interaction neutron lifetime (topcite 134)* Gravitation, equivalence principle, extra dimensions Exotic interactions, quantum interference, quantum states (topcite 96)* Baryon number violation n-n oscillations (topcite 50)* Charge conservation neutron charge (topcite 39)* Mirror Matter, spin-dependent new forces, Lorentz violation, n-n oscillations (1st time measurements in 2007@ILL) Solid state, surface science, macro-molecules, UCN microscopy and spectroscopy (Steyerl, Franck, Golub and others) (several citations) * modulo mistakes of the author, based on ISI Web of Knowledge, KK, 11/2008 Colour code: UCN CN 7

8 What caused the Baryon asymmetry? Observed*: _ (n B -n B ) / n γ = 6 x SM expectation: _ (n B -n B ) / n γ ~ Sakharov 1967: B-violation C & CP-violation non-equilibrium [JETP Lett. 5 (1967) 24] * WMAP + COBE, 2003 n B / n γ = (6.1 ± ) x 10-10

9 Need CP-violation search with low energy precision experiments 9

10 Search for TRV in neutron decay Method: Polarized CN beam Mott polarimeter G. Ban et al., NIMA565(2006)711 10

11 First physics result A. Kozela et al., arxiv: , Feb

12 EDM and symmetries + _ P _ + T + _ A nonzero particle EDM violates P, T and, assuming CPT conservation, also CP Purcell and Ramsey, PR78(1950)807; Lee and Yang; Landau 12

13 [e cm] The EDM limits to date EDM upper limit [e cm] Smith, Purcell, Ramsey PR108(1957)120 RAL-Sussex-ILL d n < 2.9 x e cm C.A.Baker et al., PRL 97 (2006) Electro-weak standard model expectation: ~10-32 e cm

14 The strong CP problem [e cm] QCD θ L QCD L QCD =0 QCD + g 2 /(32π 2 ~ ) θ QCD GG d n e cm θ QCD θ QCD < ~ Why is θ QCD so small? EDM upper limit [e cm]

15 The SUSY CP problem [e cm] d n e cm ( 300 GeV/c M SUSY 2 2 )sinφ SUSY Why is φ SUSY so small? EDM upper limit [e cm] SUSY Pospelov, Ritz, Ann. Phys. 318(2005)119 for M SUSY = 500GeV, tan β =

16 EDM projects aiming at e cm Sussex et 2009 LANL et 2013 PNPI et (2009@ILL) EDM@PSI ( 2008@ILL): 2009 Room temperature, vacuum, B-field stabilization, multiple magnetometry } Superfluid 4He, SC-shields, SQUIDS, ( 3 He, multi-chamber) 16

17 How to measure the neutron electric dipole moment? B E hν = 2 (µb+d n E) hν = 2 (µb- d n E) hδν = 4 d n E 17

18 EDM experiments at ILL Grenoble Courtesy: P. Geltenbort / O. Zimmer 18

19 Apparatus is moved to PSI in March 2009 C.A.Baker et al., PRL 97 (2006)

20 Cryo-EDM at ILL (Rutherford, Sussex, Kure, Oxford, ILL) n2edm at PSI (Berlin, Caen, Cracow, Dubna, Fribourg, Garching, Grenoble, Jena, Leuven, Mainz, München, Villigen) See HK 61.3, K. Lenz, W. Heil et al. Neutron EDM at SNS (~20 US institutes: Arizona, Berkeley, Boston,, LANL,, Yale)

21 The Neutron EDM Collaboration M. Burghoff, S. Knappe-Grüneberg, T. Sander-Thoemmes, A. Schnabel, L. Trahms G. Ban, Th. Lefort, O. Naviliat-Cuncic, E. Pierre 1, G. Rogel 2 K. Bodek, St. Kistryn, M. Kuzniak 1, J. Zejma A. Kozela N. Khomutov M. Cvijovic, P. Knowles, A.S. Pazgalev, A. Weis P. Fierlinger, M. Horras 1, F. Kuchler N.N. G. Quéméner, D. Rebreyend, S. Roccia G. Bison N. Severijns, N.N. N. du Fresne von Hohenesche, G. Hampel, J.V. Kratz, T. Lauer, C. Plonka-Spehr, N. Wiehl W. Heil, Yu. Sobolev 3 I. Altarev, E. Gutsmiedl, S. Paul, R. Stoepler M. Daum, R. Henneck, K. Kirch, A. Knecht 4, B. Lauss, A. Mtchedlishvili, G. Petzoldt, G. Zsigmond Physikalisch Technische Bundesanstalt, Berlin Laboratoire de Physique Corpusculaire, Caen Institute of Physics, Jagiellonian University, Cracow Henryk Niedwodniczanski Inst. for Nucl. Physics, Cracow Joint Institute of Nuclear Reasearch, Dubna Département de physique, Université de Fribourg, Fribourg Excellence Cluster Universe, Garching Institut Laue-Langevin, Grenoble Laboratoire de Physique Subatomique et de Cosmologie, Grenoble Biomagnetisches Zentrum, Jena Katholieke Universiteit, Leuven Inst. für Kernchemie, Johannes-Gutenberg-Universität, Mainz Inst. für Physik, Johannes-Gutenberg-Universität, Mainz Technische Universität, München Paul Scherrer Institut, Villigen also at: 1 Paul Scherrer Institut, 2 ILL Grenoble, 3 PNPI Gatchina, 4 University of Zürich

22 Next generation of experiments will in any case, severely constrain non-sm physics perhaps establish a finite value!! Courtesy: A. Knecht 22

23 EDMs of neutron and others constrains models of CP-violation one of the most promising searches for beyond-sm physics can be combined with other EDM searches to learn about the source of CP-violation Pospelov, Ritz, Ann. Phys. 318 (2005) 119 See also HK 61.7, P. Fierlinger, F. Kuchler et al., 129Xe EDM 23

24 Weak interaction n-decay puzzle Decay asymmetry determines λ: Courtesy: R. Picker / S. Materne 24

25 Weak interaction n-decay puzzle Closer look at τ and A Decay asymmetry determines λ: Courtesy: R. Picker / S. Materne 25

26 neutron lifetime / s Neutron lifetime puzzle Courtesy: R. Picker New improved neutron lifetime experiments must be of high priority: Aim at 0.1s precision! Various projects in preparation, emphasis on magnetic trapping permanent magnetic traps Ezhov et al. at ILL LANL superconducting traps NIST SNS PENeLOPE/TUM see HK 10.1, 10.4 PDG: 26

27 Decay asymmetry with UCN R.W. Pattie, Jr. et al. (UCNA) PDG average UCN State of the art (cold neutrons): H. Abele et al.(perkeo II), PRL 88 (2002) Improvements for new data: thinner windows, better calibration, higher statistics; analysis for more data (20x) under way λ accessible via decay asymmetry A or other correlations, e.g., a see HK 74.1 M. Simson et al.

28 The next 10 years will bring new high intensity UCN sources (x100), next generation nedm results (x100), new neutron lifetime results (x10), improved decay correlation SM-tests ( x10), more tests of weak couplings, QM, gravity, Lorentz-invariance (some first ever exps.), all together, a bright time for fundamental physics with low energy neutrons! 28

29 Very exciting and promising outlook! Thank you! 29

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31 EDM Experiment Sussex-RAL-ILL experiment d n < 2.9 x e cm C. A. Baker et al., PRL 97 (2006) P. G. Harris et al., PRL 82 (1999) 904

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33 ntrv at Funspin 33

34 Anticipated accuracy of the experiment: ΔN = ΔR Only neutron decay: N-correlation R-correlation 34

35 Anticipated accuracy of the experiment: ΔN = ΔR Neutron + nuclear β-decays: N-correlation R-correlation 35

36 UCNA Improvements for New Data Thinner endcap/detector windows 2.5 µm/25 µm 0.7 µm/6 µm Reduces systematic corrections/uncertainties Improved energy calibrations Additional radioactive sources ( 113 Sn, 85 Sr, 207 Bi, 109 Cd, 139 Ce) and variable pulsed LED system Reduces systematic uncertainties Higher beam current, more hermetic UCN guides & longer physics running period Neutron decay rate at 15-18Hz compared to 7 Hz Recently accumulated ~ 20 X more data Analysis of new data underway 36

37 UCN source at PSI Deliver 600 MeV, 2mA at 1% duty cycle to UCN target station UCN experiments 37

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