Lafont Fabien Roulier Damien Virot Romain

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1 Lafont Fabien Roulier Damien Virot Romain 03/03/2015 1

2 Standard Model (of particle physics) Theory : describes interactions between elementary particles Weak interaction Strong interaction Electromagnetism Pictures : 2

3 Fermions Standard Model (of particle physics) Theory : describes interactions between elementary particles Elementary particles Give other particles mass via the Higgs mechanism Mediate the weak, strong and electromagnetic interactions Matter 3

: Baryons Give other particles mass via the Higgs mechanism Bosonic :

4 Fermions Hadrons Standard Model (of particle physics) Theory : describes interactions between elementary particles Elementary particles Fermionic : Baryons Give other particles mass via the Higgs mechanism Bosonic : Mesons Mediate the weak, strong and electromagnetic interactions Matter 4

5 Standard Model (of particle physics) Theory : describes interactions between elementary particles Elementary particles Parameters and CKM matrix masses, coupling constants CKM matrix (quark-mixing matrix) : mixing angles, CP-violating phase 5

6 Standard Model (of particle physics) Theory : describes interactions between elementary particles Elementary particles Parameters and CKM matrix Limits : does not take into account/cannot explain Dark matter Gravitation (graviton?) and general relativity 6

7 Symmetries Symmetries naturally exist Naively, should work on any theory We consider 3 types (discrete symmetries) : charge (C) parity (P) time (T) 7

8 Symmetries Charge Particle/antiparticle Particle with charge +q ->particle with charge q, but same properties otherwise, should exist and behave the same 8

9 Symmetries Parity (x,y,z) -> (-x,-y,-z) The symmetrized particle should exist in the same proportion as the original. Ex : spin 9

10 Symmetries Time reversal t -> -t The theory should not be changed if time goes backward 10

11 Symmetries Symmetries can be conjugated CP symmetry, CPT symmetry Symmetries can be broken C, CP Theories are constructed from symmetries In standard model, CPT is always true 11

12 History of the neutrino In 1930, continuous electron spectrum from Beta decay is a big problem Two-body decays (A B + C) involves determined kinetic energies if A is at rest At this time, β decay is supposed to be a 2 body decay but the e spectrum is continuous! Mr Debye about continuous electron spectrum from β decay : "Oh, It's better not to think about this at all, like new taxes." 12

History of the neutrino In 1930, continuous electron spectrum from Beta decay is a big problem Two-body decays (A B + C) involves determined kinetic energies if A is at rest At this time, β decay is

13 History of the neutrino In 1930, continuous electron spectrum from Beta decay is a big problem Two-body decays (A B + C) involves determined kinetic energies if A is at rest At this time, β decay is supposed to be a 2 body decay but the e spectrum is continuous! Mr Debye about continuous electron spectrum from β decay : "Oh, It's better not to think about this at all, like new taxes." Pauli proposed that a light neutral particle (no tracks left) was also emitted, carrying the missing energy : he called it the neutron In 1932 Chadwick discover the actual neutron and the particle was renamed neutrino by Fermi («little neutral one») in 1933 Neutrinos were then hypothetical particles : they didn t decay or left any tracks, no one saw a neutrino do anything Neutrinos only interact through weak processes 13

14 History of the neutrino In 1956 neutrinos are detected for the first time via «inverse» beta decay : ν e + p n + e + Gamma ray from neutron capture by an appropriate nucleus Pair annhilation with surrounding electron : e + + e 2γ Coincidence : unique signature of antineutrino interaction In 1962 (1975), the muon (tau) neutrino was detected for the first time 3 neutrino flavors: Only 3 neutrinos that can interact through weak processes (with mass < 45 GeV) 14

to a third of the prediction Many experiments investigated this problem and

15 Neutrino oscillations In 1968, Ray Davis et al. reported the first solar (electron) neutrino flux measurement with a flux equals to a third of the prediction Many experiments investigated this problem and neutrino oscillations were confirmed only about 10 years ago Solar neutrinos anomaly Atmospheric neutrinos anomaly 15

16 Neutrino oscillations Oscillations are sensitive to differences in the square of the neutrino masses Neutrinos are NOT massless! Δm 2 sol =7x ev² Δm atm = 2x10-3 ev² Flavor Mass Maki Nakagawa Sakata matrix (MNS matrix) 16

17 Neutrino oscillations Oscillations are sensitive to differences in the square of the neutrino masses Neutrinos are NOT massless! Δm 2 sol =7x ev² Δm atm = 2x10-3 ev² Flavor Mass Maki Nakagawa Sakata matrix (MNS matrix) Interaction as flavor (electron, muon or tau neutrino) but propagate as mass eigenstate 17

18 Sterile Neutrino Strong indications for a 4 th, sterile, neutrino : Re-evaluation of the reactor antineutrino fluxes : Impacted by radiative correction and neutron lifetime 6% deficit of electron antineutrino in reactor fluxes Deficit in close range count of electron neutrinos from calibration sources ( 51 Cr and 37 Ar) LSND result : electron antineutrino found in a pure muon antineutrino beam The resulting oscillation is driven by a mass difference of about 1 ev This mass difference is to big to fit with ν 1, ν 2 and ν 3, thus a 4 th neutrino is required Such a sterile neutrino would not interact through weak interaction and would be only sensitive to gravitation They are possible dark matter candidates! 18

19 Sterile Neutrino Current experiments searching for a sterile neutrino : 19

The STEREO experiment STEREO @ ILL : Compact 58 MW reactor core of the ILL : high flux and small size of the source compared to expected

predicted antineutrino spectrum Close to the reactor core (~9-10 m) Detection using liquid scintillator doped with Gd Inverse beta decay

20 The STEREO experiment ILL : Compact 58 MW reactor core of the ILL : high flux and small size of the source compared to expected sterile neutrino oscillation length (and compared to power reactors) Highly enriched uranium nuclear fuel : reduced uncertainty of the predicted antineutrino spectrum Close to the reactor core (~9-10 m) Detection using liquid scintillator doped with Gd Inverse beta decay Prompt event from e + + e - annihilation Delayed event from neutron capture on Gd nucleus Neutrino experiments are very sensitive to background 20

antineutrinos ν Shielding against environmental fast

21 The STEREO experiment Measurement of neutrino flux at different positions Muon veto Photomultiplier Reactor antineutrinos ν Shielding against environmental fast neutrons and gamma rays Segmented liquid scintillator volume 21

term of the CKM (quark mixing) matrix Parameters V ud λ = g A gv Weak axial vector coupling

22 Free neutron β decay Free neutron β decay is a great probe for physics beyond the standard model E kin = up to 751 ev In the Standard Model: E kin = up to 781 kev E kin = up to 782 kev Upper left term of the CKM (quark mixing) matrix Parameters V ud λ = g A gv Weak axial vector coupling Observables τ n a A B C Functions of spins and/or momenta of the decay products Over-constrained system 22

23 Alphabet soup Decay rate of neutrons The «alphabet soup» 23

24 Alphabet soup Decay rate of neutrons The «alphabet soup» In the Standard Model framework : 24

25 Alphabet soup Decay rate of neutrons The «alphabet soup» In the Standard Model framework : More generally : 25

26 PERKEO III Measurement of A (electrons) Pulsed and polarized neutron beam 26

27 PERKEO III Measurement of A (electrons) Neutron + spin Electron Pulsed and polarized neutron beam Detector 1 Detector 2 27

28 PERKEO III Measurement of A (electrons) Neutron + spin Electron Pulsed and polarized neutron beam Detector 1 Detector 2 2 Measurements of A 28

29 PERKEO III Measurement of C (protons), actually PF1b, ILL7 Neutron + spin Electron Proton Electron from the conversion Conversion foils Retardation electrodes Pulsed and polarized neutron beam Conversion foil : p e - 29

PERKEO III Measurement of C (protons), actually installed @ PF1b, ILL7 Neutron + spin Electron Proton Electron from the conversion

30 PERKEO III Measurement of C (protons), actually PF1b, ILL7 Neutron + spin Electron Proton Electron from the conversion Conversion foils Retardation electrodes Pulsed and polarized neutron beam Conversion foil : Detector 1 Detector 2 p e - C C 2 Measurements of C 30

Easier to manipulate Reduced high-velocities induced systematics errors in

31 UCNs Extremely low energy : < 300 nev Velocity : < 10 m.s -1 Why are we interested in those neutrons? Easier to manipulate Reduced high-velocities induced systematics errors in experiments Specific characteristics UCN can be fully reflected by materials Thus, UCN can be bottled U C N To be consumed in moderation 31

32 UCN property : reflection on materials De Broglie wavelength : 1000 Å UCN «cannot see» matter as isolated atoms but as a set of atoms characherized by a potential Fermi potential : Examples : Element Density (g/cc) Σb coh (fm) Ni Be Ti U (nev) Al

33 UCN property : reflection on materials Schrödinger equation : ν lim = 2. U m 33

34 UCN losses Inelastic up-scattering Absorption : Impurities in material (clusters with lower Fermi potential) Adsorbed/Absorbed Hydrogen/Hydrogenated molecules Others Real material described by : U = V - i.w 34

35 How to produce those neutrons? Fraction of UCN in a maxwellian thermalized neutron spectrum : T=300 K { vlim = v lim Cu =5.67 m.s 1 β 35

36 How to produce those neutrons? Cooling of moderator T T/2 36

37 How to produce those neutrons? Mechanical solutions Turbine rotating in the same direction as neutrons (Doppler shifting device) : Velocity of neutron (v n ) with respect to the turbine blades (v b ) Before collision : v n -v b After collision : v b -v n Velocity of a neutron after collision in laboratory system : 2v b -v n 37

38 How to produce those neutrons? Superfluid He 4 : one phonon interaction at 8.9Å 38

39 Important points Kinetic energy : ~ 100 nev Fermi potential : ~ 100 nev Gravitational potential : 102 nev.m -1 Magnetic potential : ~ 60 nev.t -1 Can be trapped materially, gravitationally and magnetically! 39

40 Neutron EDM EDM : distribution of positive and negative charge inside the neutron Two major implications if EDM>0 : Proof of a theory beyond standard model SM provides a nedm of e.cm Evidence of CP violation in quark section One of the Sakharov conditions to explain asymmetry between matter and anti-matter 40

41 nedm : Symmetry violations P symmetry T symmetry 41

42 Ramsey measurement method Ĥ = μ n. B d n. E Energy difference between two spin states : ε = h. ν = 2. μ n. B ± 2. d n. E <S z > = + h/2 B 0 B 0 E B 0 E <S z > = - h/2 h (0) = -2μ.B h ( )= -2(μ.B-d n.e) h ( )= -2(μ.B+d n.e) 42

43 Ramsey measurement method Ĥ = μ n. B d n. E Energy difference between two spin states : ε = h. ν = 2. μ n. B ± 2. d n. E Neutron spin precesses at Larmor ν : Shifted due to the coupling d n.e (if d n 0) Measure the difference between the precession frequency when E field is inverted. Δν = υ υ = 4. d n h. E 43

44 Ramsey measurement method Polarized UCNs precess at Larmor frequency RF field pulse τ RF Neutron spin free precession (T>> τ RF ) Phase accumulated if dn 0 Second RF field pulse τ RF => Probability of spin-flip 44

45 Ramsey measurement method Several detuned radio-frequencies Adjust a Ramsey resonance curve Deduce shifted Larmor frequencies for each E configuration h. Δν d n = 4. E 45

46 Why are UCNs interesting? In beam experiments, neutron feels an additional radial magnetic field : B r = v x E c B t = v c E. sin (θ EB) + B v c E 2 Thus, when E is reversed, B t change This effect can be interpreted as a false EDM With UCNs, lower systematic effects v x E magnetic effect substantially reduced (lower v, <v> 0, lower σ(v)) 46

47 Free neutron lifetime Not predicted by any model Input parameter for Standard Model Experimental value used for Y p, V ud Precision needed to put constraints on other parameters and check validity of SM. 47

48 Free neutron lifetime 1% variation on tau -> 0.75% variation on Y p V ud formula Unitarity 48

49 Free neutron lifetime Two methods of measurement : Beam : Count the dead Bottle : Count the survivors wait 49

50 Free neutron lifetime Two methods of measurement : Beam : Bottle : Count the dead Count the survivors 50

51 Free neutron lifetime Two methods of measurement : Beam : Bottle : 51

52 Free neutron lifetime Beam method : Snell, Pleasonton, McCord 1950 Simultaneous detection of protons and electrons 52

53 Free neutron lifetime Beam method : Bondarenko et al., 1978 Proton detection 53

54 Free neutron lifetime Beam method : Nico et al., 2005 Proton detection 54

55 Free neutron lifetime Bottle method : count remaining UCNs at different waiting times ->expo curve Improvements : magnetic trap 55

56 Free neutron lifetime Bottle method : MAMBO Mampe et al., 1989 MAMBO II Pichlmaier et al

57 Free neutron lifetime Bottle method : GRAVITRAP Kharitonov et al., 1989 Alfimenkov et al

58 Free neutron lifetime Magnetic trap: Magnetic bottle Ezhov et al Field : 2 T/cm 58

Gravitational quantum states Discrete quantum properties of matter : Quantum states of e - in EM field structure of the atoms Quantum states of nucleons in strong nuclear field structure of atomic

59 Gravitational quantum states Discrete quantum properties of matter : Quantum states of e - in EM field structure of the atoms Quantum states of nucleons in strong nuclear field structure of atomic nuclei Gravitational force is very weak compared to EM and strong force observation of quantum states of matter in a gravitational field is extremely challenging Neutron are excellent candidates for such observations : Long lifetime Neutral Low mass Schrödinger equation Macroscopic scale of the first quantum level! 59

60 Gravitational quantum states Total count rate VS absorber height Full classical treatment Full quantum treatment 60

61 qbounce and : 2 experiments on this topic, qbounce and Granit Main differences between qbounce and Granit: qbounce Offline detection Granit Online detection Vibrating mirror EM fields 61

62 qbounce results Offline detection for qbounce N + 10 B α + 7 Li Track left by the alpha particle in the CR39 plastic Spatial resolution of ~1,5 μm 1 st quantum state 2 nd quantum state For a 30 μm slit Sum 62

63 Accelerated expansion of the universe In cosmological standard model : Dark energy = constant? Dark energy=scalar field? Scalar field varies in time because of the expansion could be observed 63

64 The quintessence hypothesis Dark Energy is due to a cosmological scalar field φ Ratra-Peebles potential Problem : should interact with normal matter as a fifth force Chameleon mechanism [Khoury & Weltman PRD 69 (2004)] 64

65 Understanding the chameleon mechanism Plate with charge density ρ Poisson equation for the electric potential φ Electric field dφ/dx proportional to ρ 65

66 Understanding the chameleon mechanism Nonlinear equation for the chameleon field Plate with mass density ρ φ 66

67 Chameleon field and neutrons Brax & Pignol Strongly Coupled Chameleons and the Neutronic Quantum Bouncer 2011 Consequences for the neutron bouncer Mirror and table Independent of the mirror s density, independent of β! 1) Squeezing of the wave functions 2) Dilatation of the energy spectrum Distance scale: µm 67

68 Limits on strongly coupled chameleons Jenke et al. Gravity Resonance Spectroscopy Constrains Dark Energy and Dark Matter Scenarios 2014 Lemmel et al. Neutron Interferometry constrains dark energy chameleon fields

69 Other applications Dark matter, dark energy: neutron/mirror neutron oscillations Search for axion-like particles Nuclear physics models exotic, neutron-rich nuclides (production, decays, magnetic moments, r-process) fission yields Lifetime of nuclear decay GAMMS, LOHENGRIN, EXILL, ILL 69

70 Conclusion Fundamental physics is broad : particle physics, cosmology, nuclear physics, condensed matter,... Neutron can be a tool as well as an object of study The ILL is a favorable place for fundamental physics 70

71 Conclusion Thank you! Special thanks to: Geltenbort Peter Soldner Torsten 71

High-precision studies in fundamental physics with slow neutrons. Oliver Zimmer Institut Laue Langevin

High-precision studies in fundamental physics with slow neutrons Oliver Zimmer Institut Laue Langevin ILL, 20 September 2016 Topics The impossible particle and its properties Search for an electric dipole