Transcript nEDM - IN2P3

Journée de la division Champs et Particules de la SFP
« Le Futur de la Physique des Saveurs »
Jussieu, janvier 2007
Mesure du moment
électrique dipolaire du neutron
Oscar Naviliat-Cuncic
LPC-Caen et Université de Caen Basse-Normandie
Plan
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role of low energy precision measurements
measurement principle
experimental sensitivity
role of UCNs and their sources
present limit on the neutron EDM
the world competition
toward a new nEDM measurement
the new UCN source at PSI
R&D activities (materials, detectors, magnetometry)
plans and schedule
SFP-LPNHE, 27 janvier 2007
O.Naviliat-Cuncic:
[email protected]
2
Potential of low precision measurements
• 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-(31-33) ecm; correlations in beta decay <10-10)
• Huge window to search for new physics!
(without being affected by SM backgrounds)
• EDMs of quantum systems are very sensitive probes
SFP-LPNHE, 27 janvier 2007
O.Naviliat-Cuncic:
[email protected]
3
Permanent EDMs
• observables
- spin S, unit vector ŝ
- magnetic dipole moment:
m=mŝ
- for an elementary QM system:
d=dŝ
• classical dipole interaction
H = - (d ·E + m ·B) = - (d E + m B) · ŝ
• transformations under T and P
B and ŝ behave identically but not E and ŝ
if d ≠ 0 : T and P are violated
SFP-LPNHE, 27 janvier 2007
O.Naviliat-Cuncic:
[email protected]
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EDM measurements
• upper limits have been obtained for:
e, m,t, p, n, L, atoms, molecules
• new projects and approaches are being considered for:
e, m, n, d, radioactive nuclei, atoms
• very active field !
• complementary constraints (ex. SUSY phases)
Any new mechanism for CP violation in the quark sector has
in particular to pass the neutron EDM test
[ see e.g. R. Barbieri et al. NP B449 (1995) 437; hep-ph/9504373]
SFP-LPNHE, 27 janvier 2007
O.Naviliat-Cuncic:
[email protected]
5
Neutron EDM evolution
• Experimental advantages
 no electric charge
 long lifetime
 storage of UCNs possible
• Requirements for higher
sensitivity
 larger densities
 further control of systematics
SFP-LPNHE, 27 janvier 2007
O.Naviliat-Cuncic:
[email protected]
6
Measurement principle
Ramsey method of
Separated Oscillating Fields
• prepare a sample of polarized neutrons
• make a p/2 spin flip (“start clock”)
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“Spin up”
neutron...
2
Apply p/2
spin flip
pulse...
• allow free spin precession in parallel B
and E static fields
E
• make a p/2 spin flip (“stop clock”)
B
3
Free
precessio
n...
4
Second p/2
spin flip
pulse.
• analyze direction of neutron spin
• look at energy (frequency) shift
under field inversion:
De = h |Dn| = 4Edn
SFP-LPNHE, 27 janvier 2007
O.Naviliat-Cuncic:
[email protected]
7
Sensitivity figure

 (d n ) 
2ET N
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 : slope on resonance curve (“visibility”)
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T : free precession time
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E : electric field strength
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N : total number of detected neutrons (N ~ r V tmes)
• high sensitivity requires
SFP-LPNHE, 27 janvier 2007
O.Naviliat-Cuncic:
- long precession times
- large neutron densities
[email protected]
8
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)
ln ≈ 800 Å ;
vn ≈ 5 m/s
Tn ≈ 2 mK ; En ≈ 130 neV
SFP-LPNHE, 27 janvier 2007
O.Naviliat-Cuncic:
[email protected]
9
The UCN source at ILL
• the only multi-user UCN source in operation
• 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 at experiment: r = 20 /cm3
SFP-LPNHE, 27 janvier 2007
O.Naviliat-Cuncic:
[email protected]
10
Sussex-RAL-ILL experiment
(P.G. Harris et al. PRL 82(1999) 904)
• V = 20 l
• B = 10 mG, nL = 30 Hz
• E = 4.5 - 11.0 kV/cm
• T = 120 - 140 s
best achieved sensitivity with 50% duty cycle
 (dn) = 5×10-26 ecm / 50 days cycle
SFP-LPNHE, 27 janvier 2007
O.Naviliat-Cuncic:
[email protected]
11
Final Sussex-RAL-ILL result
use of 199Hg co-magnetometer
d(199Hg) < 8.7 × 10-28 ecm
(C.A. Baker et al. PRL 97(2006) 131801)
50 pT
SFP-LPNHE, 27 janvier 2007
O.Naviliat-Cuncic:
| dn | < 2.9 x 10-26 ecm (90% CL)
[email protected]
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World competition (cryo exps)
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cryo UCN sources in super-fluid He
superconducting Pb shields
SQUID magnetometry
full in LHe experiments
(Sussex-RAL-ILL-Kure)
• also project in preparation in Japan
SFP-LPNHE, 27 janvier 2007
O.Naviliat-Cuncic:
[email protected]
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Toward a new EDM measurement
G. Ban, Th. Lefort, 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
N. Khomutov, B.M. Sabirov
Joint Institute of Nuclear Reasearch, Dubna, Russia
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, S. Roccia, M. Tur
Laboratoire de Physique Subatomique et de Cosmologie, Grenoble, France
M. Daum, R. Henneck, S. Heule, M. Kasprzak, K. Kirch, A. Knecht, A. Pichlmaier
Paul Scherrer Institute, Villigen, Switzerland
SFP-LPNHE, 27 janvier 2007
O.Naviliat-Cuncic:
[email protected]
14
Specific features and steps
Push the room-temperature, in-vacuum technique to a new limit
At ILL (since 2004):
• Work with the RT spectrometer of Sussex-RAL-ILL
(learn, repair, measure, test, recuperate, ….)
• Improve magnetic field measurement
• Improve magnetic field stability and homogeneity
• Improve overall stability and control
At PSI (at new UCN source):
• Increase statistics
• Implement new tools for control of systematics
• Build new spectrometer
Final goal: improve by two orders of magnitude the
present level of sensitivity
SFP-LPNHE, 27 janvier 2007
O.Naviliat-Cuncic:
[email protected]
15
Operation at ILL
RAB95, amp x t = 16.5, t_prec = 50 s, visibility = 0.43, correct Ramsey
with two pi/2 spinflips
6000
5500
cts/cycle
5000
4500
spinup
4000
spindown
3500
3000
2500
2000
29,66
29,67
29,68
29,69
29,7
29,71
29,72
n-frequency [Hz]
• General operation under control
• Many failures, reparations, replacements
• New full test measurement for end 2007
(not for a new EDM value)
SFP-LPNHE, 27 janvier 2007
O.Naviliat-Cuncic:
[email protected]
16
Spallation UCN source at PSI
• moderators: D2O (20-80 K)
• UCN source: SD2 (30 l, 8K)
• storage volume: 2-3 m3
• 590 MeV, 2 mA, proton beam
• pulsed (1% duty cycle)
• spallation target: Pb
• expected density: r = 2-3000 /cm3
• starting operation end 2008
SFP-LPNHE, 27 janvier 2007
O.Naviliat-Cuncic:
[email protected]
17
MC simulations and materials
(required the inclusion of UCN physics into GEANT4 – P. Fierlinger and others, NIMA 552(2005)513 )
Storage time with chamber at 1m above beam line
Chamber/Electrode
Quartz/DLC:
Si3N4/DLC:
Diam./DLC:
Diam./Diam.:
present system:
SFP-LPNHE, 27 janvier 2007
O.Naviliat-Cuncic:
[email protected]
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1
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Detector tests and spin analysis
Doped glass scintillator
GEM
UCN
Spin flipper
Spin flipper
GS10
n6Li    t
SFP-LPNHE, 27 janvier 2007
n10B    7Li
n B    Li   (0.48MeV )
10
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O.Naviliat-Cuncic:
[email protected]
GS10
analyzers
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Magnetometry
• Cs Laser Optically Pumped magnetometer
magnetic resonance
+
optical preparation & detection
1 magnetometer (OPM) needs 25 mW
1 laser delivers >10 mW
1 laser = many sensors
Intrinsic sensitivity demonstrated:
residual field fluctuations at 40fT for stabilized OPM
SFP-LPNHE, 27 janvier 2007
O.Naviliat-Cuncic:
[email protected]
20
Discovering a magnetic anomaly…
Set of 8 Cs OPM
Field variations correlated with movement of the UCN shutter seen at
different locations: …hunt the magnetic impurity!
SFP-LPNHE, 27 janvier 2007
O.Naviliat-Cuncic:
[email protected]
21
Phases and schedule
2007
2008
2009
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2010
2011
2012
Operation of UCN source at PSI
Improvements Sussex-RAL spectro
Phase 1
Mesure with Sussex-RAL spectro
Design new spectrometer
Construction new spectrometer
Phase 2
Mesure with new spectro
• phase 0: R&D at ILL (…now)
• phase 1: measurement at PSI with old improved spectro
 (d n )  5 1027 ecm
• phase 2: measurement at PSI with new spectro
 (dn )  3 1028 ecm
SFP-LPNHE, 27 janvier 2007
O.Naviliat-Cuncic:
[email protected]
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