Mesure du moment électrique dipolaire du neutron Oscar Naviliat-Cuncic LPC-Caen et Université de...
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Transcript of Mesure du moment électrique dipolaire du neutron Oscar Naviliat-Cuncic LPC-Caen et Université de...
Mesure du momentélectrique dipolaire du neutron
Oscar Naviliat-CuncicLPC-Caen et Université de Caen Basse-Normandie
Institut de Physique Nucléaire d'Orsay
Mars 2005
2 IPN - Orsay, 7 février 2005 O.Naviliat-Cuncic: [email protected]
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
3 IPN - Orsay, 7 février 2005 O.Naviliat-Cuncic: [email protected]
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 !
4 IPN - Orsay, 7 février 2005 O.Naviliat-Cuncic: [email protected]
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 < 10-31 ecm; beta decay correlations <10-10)
• 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
5 IPN - Orsay, 7 février 2005 O.Naviliat-Cuncic: [email protected]
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
6 IPN - Orsay, 7 février 2005 O.Naviliat-Cuncic: [email protected]
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
7 IPN - Orsay, 7 février 2005 O.Naviliat-Cuncic: [email protected]
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
8 IPN - Orsay, 7 février 2005 O.Naviliat-Cuncic: [email protected]
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
4
3
2
1
Free precession...
Apply /2 spin flip pulse...
“Spin up” neutron...
Second /2 spin flip pulse.
B
E
energy (frequency) shift under field inversion: = h || = 4Edn
9 IPN - Orsay, 7 février 2005 O.Naviliat-Cuncic: [email protected]
beam technique with cold neutrons
(W.B. Dress et al. Phys. Rev. 170(1968)1200)
• vn ≈ 100 m/s
• Pn ≈ 70%
• B ≈ 10 G
10 IPN - Orsay, 7 février 2005 O.Naviliat-Cuncic: [email protected]
beam technique result
(W.B. Dress et al. Phys. Rev. 170(1968)1200)
• final:
dn = (0.4 ± 1.5) × 10-24 ecm
(W.B. Dress et al. Phys. Rep. 43(1978)410)
new techniques required for further improvements!
11 IPN - Orsay, 7 février 2005 O.Naviliat-Cuncic: [email protected]
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 ; vn ≈ 5 m/s
Tn ≈ 2 mK ; En ≈ 130 neV
12 IPN - Orsay, 7 février 2005 O.Naviliat-Cuncic: [email protected]
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 × 1015 n/s/cm2
• cold neutron source: 20 l of LD2 at 25K
• vertical neutron guide 13m, 7×7 cm2, (58Ni coated)
• UCN source: rotating turbine
• UCN density: = 20 /cm3
13 IPN - Orsay, 7 février 2005 O.Naviliat-Cuncic: [email protected]
…in real life
14 IPN - Orsay, 7 février 2005 O.Naviliat-Cuncic: [email protected]
Sussex-RAL-ILL experiment(P.G. Harris et al. PRL 82(1999) 904)
• V = 20 l
• B = 10 mG, L = 30 Hz
• E = 4.5 - 11.0 kV/cm
• T = 120 - 140 s
use of 199Hg co-magnetometer
d(199Hg) < 8.7 × 10-28 ecm
15 IPN - Orsay, 7 février 2005 O.Naviliat-Cuncic: [email protected]
Sussex-RAL-ILL result
(P.G. Harris et al. PRL 82(1999) 904)
dn = (-3.4 ± 3.9 ± 3.1)×10-26 ecm
16 IPN - Orsay, 7 février 2005 O.Naviliat-Cuncic: [email protected]
statistical sensitivity
(dn) = 5×10-26 ecm / 50 days cycle
optimal sensitivity (with 50% running efficiency)
(dn) = 15×10-26 ecm / 50 days cycle
current sensitivity (UCN losses and depolarization)
NETdn
2
)(
●: slope on resonance curve
• T : free precession time
• E : electric field strength
• N : total number of detected neutrons (N ~ V tmes)
17 IPN - Orsay, 7 février 2005 O.Naviliat-Cuncic: [email protected]
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 10-27 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
19 IPN - Orsay, 7 février 2005 O.Naviliat-Cuncic: [email protected]
UCN source at PSI
• 590 MeV, 2 mA, proton beam
• pulsed: 4 s ON/ 600 s OFF (low duty cycle)
• spallation target: Pb
• moderators: D2O (20-80 K)
• UCN source: SD2 (30 l, 8K)
• volume: 2 m3 (Be coated: vL = 6.9 m/s)
• expected density: = 3000 /cm3
20 IPN - Orsay, 7 février 2005 O.Naviliat-Cuncic: [email protected]
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
21 IPN - Orsay, 7 février 2005 O.Naviliat-Cuncic: [email protected]
UCN polarization
(measurements by PNPI; compare with PSI annual report)
objectives:
• improve Pn : (0.9 to 1)
• increase available UCN density
implementation:
• separate polarization from analysis
• magnetized foils → SC solenoid
22 IPN - Orsay, 7 février 2005 O.Naviliat-Cuncic: [email protected]
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 3He
• develop spin analyzers
23 IPN - Orsay, 7 février 2005 O.Naviliat-Cuncic: [email protected]
UCN counters
)48.0()83.0()47.1(
)01.1()78.1(710
710
MeVMeVLiMeVBn
LiMeVBn
)74.2()05.2(6 MeVtMeVLin Si/LiF/Si sandwich: 380m/ 600 g/cm2/ 380m
(Gatchina)
(Heidelberg)
hybrid solid/gas detector: CASCADE
6Li doped glass scintillator
)74.2()05.2(6 MeVtMeVLin
(Caen)
24 IPN - Orsay, 7 février 2005 O.Naviliat-Cuncic: [email protected]
GS10 test and spin analysis
pulse height spectrum transmission asymmetry
Detectorturbinespin flipper
polarizer analyzer
chopper
GS10
25 IPN - Orsay, 7 février 2005 O.Naviliat-Cuncic: [email protected]
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
26 IPN - Orsay, 7 février 2005 O.Naviliat-Cuncic: [email protected]
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 199Hg vapor magnetometers
• develop OPMs sensitive to field components
27 IPN - Orsay, 7 février 2005 O.Naviliat-Cuncic: [email protected]
self-oscillating laser pumped cesium magnetometer
magnetic resonance +
optical preparation & detection
1 magnetometer (OPM) needs 25 W
1 laser delivers >10 mW1 laser = many sensors
28 IPN - Orsay, 7 février 2005 O.Naviliat-Cuncic: [email protected]
magnetic field fluctuations in a multi-layer shield
field not stabilized
field stabilized
residual gradient fluctuations >40 fT
coil current
12
1 2OPM 1
OPM 22 OPMs
- Co-Netic
- Mu-Metal
29 IPN - Orsay, 7 février 2005 O.Naviliat-Cuncic: [email protected]
multiple field measurement inside the ILL-EDM setup
HV electrodevector
magnetometers
neutron chamber
30 IPN - Orsay, 7 février 2005 O.Naviliat-Cuncic: [email protected]
status and plans
• 2004-2006: R&D at ILL and design of new setup
• 2007: start operation of PSI source, commissioning
• 2007-2008: measurement (1st phase)
• 2009-2012: 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, Université 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