Lafont Fabien
Roulier Damien
Virot Romain
03/03/2015
1
Standard Model (of particle physics)
 Theory : describes interactions between
elementary particles
 Weak interaction
 Strong interaction
 Electromagnetism
Pictures :
http://hadron.physics.fsu.edu/~crede/forces.html
2
Standard Model (of particle physics)
 Theory : describes interactions between
elementary particles
 Elementary particles
Fermions
Give other
particles mass
via the Higgs
mechanism
Mediate the weak,
strong and
electromagnetic
interactions
“Matter”
3
Standard Model (of particle physics)
 Theory : describes interactions between
elementary particles
Give other
particles mass
via the Higgs
mechanism
Fermionic : Baryons
Bosonic : Mesons
Fermions
Hadrons
 Elementary particles
Mediate the weak,
strong and
electromagnetic
interactions
“Matter”
4
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
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
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Symmetries
 Symmetries naturally exist
 Naively, should work on any theory
 We consider 3 types (discrete symmetries) :
 charge (C)
 parity (P)
 time (T)
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Symmetries
 Charge
 Particle/antiparticle
 Particle with charge +q
->particle with charge –q, but
same properties otherwise,
should exist and behave the
same
8
Symmetries
 Parity
 (x,y,z) -> (-x,-y,-z)
The symmetrized particle
should exist in the same
proportion as the original.
Ex : spin
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Symmetries
 Time reversal
 t -> -t
The theory should not be changed if time
goes backward
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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
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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 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
History of the neutrino
•
In 1956 neutrinos are detected for the first time via « inverse » beta decay :
𝜈𝑒 + 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)
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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
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Neutrino oscillations
•
Oscillations are sensitive to differences in the square
of the neutrino masses
Neutrinos are NOT massless !
2
Δ𝑚𝑠𝑜𝑙
=7x10-5 eV²
Flavor
2
Δ𝑚𝑎𝑡𝑚
= 2x10-3 eV²
Mass
Maki–Nakagawa–Sakata
matrix (MNS matrix)
16
Neutrino oscillations
•
Oscillations are sensitive to differences in the square
of the neutrino masses
Neutrinos are NOT massless !
2
Δ𝑚𝑠𝑜𝑙
=7x10-5 eV²
Flavor
2
Δ𝑚𝑎𝑡𝑚
= 2x10-3 eV²
Mass
Maki–Nakagawa–Sakata
matrix (MNS matrix)
Interaction as flavor (electron,
muon or tau neutrino) but
propagate as mass eigenstate
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Sterile Neutrino
Strong indications for a 4th, 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 (51Cr and
37Ar)
•
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 𝜈1 , 𝜈2 and 𝜈3 , thus a 4th 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!
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Sterile Neutrino
Current experiments searching for a sterile neutrino :
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The STEREO experiment
STEREO @ 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
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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
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Free neutron 𝛽 decay
•
Free neutron 𝛽 decay is a great probe for physics beyond the standard model
𝐸𝑘𝑖𝑛 = up to 751 eV
•
𝐸𝑘𝑖𝑛 = up to 781 keV
In the Standard Model:
Parameters
𝐸𝑘𝑖𝑛 = up to 782 keV
Upper left term of the CKM
(quark mixing) matrix
𝑉𝑢𝑑
𝑔
𝜆 = 𝐴 𝑔𝑉
Weak axial vector coupling
Observables
𝜏𝑛
𝑎
A
B
C
…
Over-constrained
system
Functions of spins and/or
momenta of the decay
products
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Alphabet soup
Decay rate of neutrons
The « alphabet soup »
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Alphabet soup
Decay rate of neutrons
The « alphabet soup »
•
In the Standard Model framework :
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Alphabet soup
Decay rate of neutrons
The « alphabet soup »
•
•
More generally :
In the Standard Model framework :
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PERKEO III
•
Measurement of A (electrons)
Pulsed and polarized neutron beam
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PERKEO III
•
Neutron + spin
Electron
Measurement of A (electrons)
Pulsed and polarized neutron beam
•
Detector 1
•
Detector 2
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PERKEO III
•
Neutron + spin
Electron
Measurement of A (electrons)
Pulsed and polarized neutron beam
•
Detector 1
•
2 Measurements of A
Detector 2
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PERKEO III
Neutron + spin
Electron
Proton
Electron from the
conversion
• Measurement of C (protons),
actually installed @ PF1b, ILL7
Conversion foils
Retardation electrodes
Pulsed and polarized neutron beam
•
Conversion foil :
p
e-
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PERKEO III
Neutron + spin
Electron
Proton
Electron from the
conversion
• Measurement of C (protons),
actually installed @ PF1b, ILL7
Conversion foils
Retardation electrodes
Pulsed and polarized neutron beam
•
•
Conversion foil :
p
e-
C
Detector 1
•
Detector 2
C
2 Measurements of C
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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”
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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)
Σbcoh (fm)
U (neV)
Ni58
8.8
14.4
335
Be
1.83
7.75
252
Ti
4.54
-3.34
-48
Al
2.7
3.45
54
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UCN property : reflection on materials
 Schrödinger equation :
𝜈𝑙𝑖𝑚 =
2. 𝑈
𝑚
33
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
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How to produce those neutrons ?
 Fraction of UCN in a maxwellian thermalized
neutron spectrum :
𝑇=300 𝐾
{𝑣𝑙𝑖𝑚 = 𝑣𝑙𝑖𝑚 𝐶𝑢 =5.67 𝑚.𝑠 −1
β
35
How to produce those neutrons ?
 Cooling of moderator
T
T/2
36
How to produce those neutrons ?
 Mechanical solutions
 Turbine rotating in the same
direction as neutrons (Doppler
shifting device) :


Velocity of neutron (vn) with
respect to the turbine blades (vb)
 Before collision : vn-vb
 After collision : vb-vn
Velocity of a neutron after collision
in laboratory system : 2vb-vn
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How to produce those neutrons ?
 Superfluid He4 : one phonon interaction at
8.9Å
38
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
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 10-31 e.cm
 Evidence of CP violation in quark section

One of the Sakharov conditions to explain
asymmetry between matter and anti-matter
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nEDM : Symmetry violations
P symmetry
T symmetry
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Ramsey measurement method
Ĥ = −𝜇𝑛 . 𝐵 − 𝑑𝑛 . 𝐸
 Energy difference between two spin states :
𝜀 = ℎ. 𝜈 = −2. 𝜇𝑛 . 𝐵 ± 2. 𝑑𝑛 . 𝐸
B0
B0 E
B0 E
<Sz> = + h/2
h(0) = -2μ.B
h()=
-2(μ.B-dn.E)
h()=
-2(μ.B+dn.E)
<Sz> = - h/2
42
Ramsey measurement method
Ĥ = −𝜇𝑛 . 𝐵 − 𝑑𝑛 . 𝐸
 Energy difference between two spin states :
𝜀 = ℎ. 𝜈 = 2. 𝜇𝑛 . 𝐵 ± 2. 𝑑𝑛 . 𝐸
 Neutron spin precesses at Larmor ν :
 Shifted due to the coupling dn.E (if dn ≠ 0)
 Measure the difference between the
precession frequency when E field is inverted.
4. 𝑑𝑛
Δ𝜈 = 𝜐↑↑ − 𝜐↑↓ =
.𝐸
ℎ
43
Ramsey measurement method
 Polarized UCNs precess at Larmor frequency
 RF field pulse τRF
 Neutron spin free precession (T>> τRF)
 Phase accumulated if dn≠0
 Second RF field pulse τRF
=> Probability of spin-flip
44
Ramsey measurement method
 Several detuned
radio-frequencies
 Adjust a Ramsey
resonance curve
 Deduce shifted Larmor frequencies for each E
configuration
ℎ. Δ𝜈
𝑑𝑛 =
4. 𝐸
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Why are UCNs interesting ?
 In beam experiments, neutron “feels” an additional
radial magnetic field :
𝑣𝑥𝐸
𝐵𝑟 =
𝑐
𝑣
𝑣
2
𝐵𝑡 = 𝐸. sin⁡
(𝜃𝐸𝐵 ) + 𝐵0 + 𝐸
𝑐
𝑐
2
 Thus, when E is reversed, Bt change
 This effect can be interpreted as a false EDM
 With UCNs, lower systematic effects
 v
E magnetic effect substantially reduced
(lower v, <v>≈0, lower σ(v))
x
46
Free neutron lifetime
 Not predicted by any model
 Input parameter for Standard Model
 Experimental value used for Yp, Vud
 Precision needed to put constraints on other
parameters and check validity of SM.
47
Free neutron lifetime
 1% variation on tau -> 0.75% variation on Yp
 Vud formula
 Unitarity
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Free neutron lifetime
Two methods of measurement :
Count the dead
 Beam :
 Bottle :
Count the survivors
wait
49
Free neutron lifetime
Two methods of measurement :
 Beam :
 Bottle :
Count the dead
Count the survivors
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Free neutron lifetime
Two methods of measurement :
 Beam :
 Bottle :
51
Free neutron lifetime
Beam method :
Snell, Pleasonton,
McCord
1950
Simultaneous detection
of protons and electrons
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Free neutron lifetime
Beam method :
Bondarenko et al., 1978
Proton detection
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Free neutron lifetime
Beam method :
Nico et al., 2005
Proton detection
54
Free neutron lifetime
Bottle method : count remaining UCNs at
different waiting times ->expo curve
Improvements : magnetic trap
55
Free neutron lifetime
Bottle method :
MAMBO
Mampe et al., 1989
MAMBO II
Pichlmaier et al. 2010
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Free neutron lifetime
Bottle method :
GRAVITRAP
Kharitonov et al., 1989
Alfimenkov et al. 1992
57
Free neutron lifetime
Magnetic trap:
Magnetic bottle
Ezhov et al. 2009
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 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
Gravitational quantum states
Total count rate VS absorber height
Full classical
treatment
Full quantum
treatment
60
qBounce and Granit @ ILL
•
@ILL : 2 experiments on this topic, qBounce and Granit
•
Main differences between qBounce and Granit:
qBounce
Granit
Offline detection
Online detection
Vibrating mirror
EM fields
61
qBounce results
Offline detection for qBounce
•
𝑁 + 10𝐵 → 𝛼 + 7𝐿𝑖
•
Track left by the alpha
particle in the CR39 plastic
•
Spatial resolution of ~1,5 𝜇𝑚
1st quantum state
2nd quantum state
For a 30 𝜇𝑚 slit
Sum
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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
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)]
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Understanding the chameleon mechanism
Plate with charge density ρ
Poisson equation for the electric potential
φ
Electric field dφ/dx proportional to ρ
65
Understanding the chameleon mechanism
Nonlinear equation for the chameleon field
Plate with mass density ρ
φ
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Chameleon field and neutrons
Brax & Pignol
Strongly Coupled Chameleons
and the Neutronic Quantum
Bouncer
2011
Mirror and
table
Consequences for the neutron
bouncer
Independent of the
mirror’s density,
independent of β !
Distance scale:
1) Squeezing of the
wave functions
µm
2) Dilatation of the
energy spectrum
67
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
2015
68
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, FIPPS, … @ ILL
69
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
Conclusion
Thank you !
Special thanks to:
Geltenbort Peter
Soldner Torsten
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