EDM Searches in storage rings - Physikzentrum der RWTH Aachen

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Mitglied der Helmholtz-Gemeinschaft
EDM Searches in storage rings
July 5, 2012
Frank Rathmann
Seminar on Precision Experiments in Storage Rings
Topics





Why EDMs?
Search for EDMs using storage rings
Two projects, at BNL and Jülich
Spin coherence time
First direct measurement
Resonance Method with RF E(B)-fields
 Polarimetry
 Timeline of projects, cooperations, workshops
 Summary
[email protected]
EDM Searches in storage rings
2
What caused the Baryon asymmetry?
Carina Nebula: Largest-seen star-birth regions in the galaxy
What happened to the antimatter?
(nB  nB ) / n
Observed
610-10
SM expectation
~10-18
WMAP+COBE (2003)
Sakharov (1967): Three conditions for baryogenesis
1. B number conservation violated sufficiently strongly
2. C and CP violated, B and anti-Bs with different rates
3. Evolution of universe outside thermal equilibrium
[email protected]
EDM Searches in storage rings
3
Electric Dipole Moments (EDMs)
Permanent EDMs violate parity P and
time reversal symmetry T
Assuming CPT to hold,
combined symmetry CP violated as well.
EDMs are candidates to solve mystery of matter-antimatter asymmetry
 may explain why we are here!
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EDM Searches in storage rings
4
History of neutron EDM limits
• Smith, Purcell, Ramsey
PR 108, 120 (1957)
• RAL-Sussex-ILL
(dn  2.9 10-26 ecm)
PRL 97,131801 (2006)
Adopted from K. Kirch
[email protected]
EDM Searches in storage rings
5
Limits for Electric Dipole Moments
EDM searches - only upper limits, in  (up to now):
  equivalent
Particle/Atom
Current EDM Limit
Future Goal
Neutron
  −
−
−

 .  × −
−
−

  × −
− – −
− – −
Proton
 .  × −
−
−
Deuteron
?
−
 − –  × −
Huge efforts underway to improve limits / find EDMs
Sensitivity to NEW PHYSICS beyond the Standard Model
485. WE-Heraeus-Seminar (July 0406, 2011)
Search for Electric Dipole Moments (EDMs) at Storage Rings
http://www2.fz-juelich.de/ikp/edm/en/
[email protected]
EDM Searches in storage rings
6
Why also EDMs of protons and deuterons?
Proton and deuteron EDM experiments may provide one order higher sensitivity.
In particular the deuteron may provide a much higher sensitivity than protons.
Consensus in the theoretical community:
Essential to perform EDM measurements on different targets (, , 3He) with
similar sensitivity:
• unfold the underlying physics,
• explain the baryogenesis.
[email protected]
EDM Searches in storage rings
7
Search for Electric Dipole Moments
NEW: EDM search in time development of spin in a storage ring:

G  0
  
ds
 d E
dt
[email protected]
“Freeze“ horizontal spin precession; watch
for development of a vertical component !
EDM Searches in storage rings
8
Search for Electric Dipole Moments
NEW: EDM search in time development of spin in a storage ring:

G  0
  
ds
 d E
dt
“Freeze“ horizontal spin precession; watch
for development of a vertical component !
A magic storage ring for protons (electrostatic), deuterons, …
particle
 (/)
 (/)
 ()
proton
. 
. 
. 
deuteron
. 
−. 
. 

. 
. 
−. 
[email protected]
EDM Searches in storage rings
One machine
with  ~  m
9
Two storage ring projects being pursued
BNL for protons all electric machine
Jülich, focus on deuterons,
or a combined machine
CW and CCW propagating beams
(from R. Talman)
[email protected]
EDM Searches in storage rings
(from A. Lehrach)
10
BNL Proposal
2 beams simultaneously rotating in an all electric ring (cw, ccw)
Approved BNL-Proposal
Submitted to DOE
Goal for protons
 d  2.5 1029 e  cm (oneyear)
p
Circumference
~ 200 m
Technological challenges !
•
•
•
•
Spin coherence time ( )
Beam positioning ( )
Continuous polarimetry (<  )
E - field gradients (~  /   )
Carry out proof of principle experiments
(demonstrators) at COSY
[email protected]
EDM Searches in storage rings
11
Most recent:
Richard Talmans concept for a Jülich all-in-one machine
Iron-free, current-only, magnetic bending, eliminates hysteresis
B
A
For more details, see Richard‘s lecture
B
A
[email protected]
EDM Searches in storage rings
12
The frozen spin Method
   
For transverse electric and magnetic fields in a ring (   B    E  0 ),
anomalous spin precession is described by
 
2



 m  E

q 
G   G  B  G    

m

 p   c 


x
g 2

G



2


Magic condition: Spin along momentum vector
1. For any sign of , in a combined electric and magnetic machine
GBc 2
2
E

GBc

1  G 2 2
 = radial
 = vertical
1. For  > 0 (protons) in an all electric ring
2
m
m
G     0  p 
G
 p
[email protected]
 700 .74
MeV
c
EDM Searches in storage rings
(magic)
13
Magic condition: Protons
Case 1:   field only

r2 2 80 m3 He 0 .0
r2 2 50 md  0 .48 G
Proton EDM
100
radius (m)
80
 = 17 MV/m
60
r1( E)
40
 = 24.665 m
20
0
5
10
15
20
25
30
35
E
E-field (MV/m)
[email protected]
EDM Searches in storage rings
14
Magic condition: Protons
Case 2:   and   fields
>0
<0
magic energy
[email protected]
>0
<0
magic energy
EDM Searches in storage rings
15
Magic condition: Deuterons
  and   fields
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EDM Searches in storage rings
16
Magic condition: Helions
  and   fields
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EDM Searches in storage rings
17
Parameters for Richard Talmans all-in-one machine
Talman/Gebel give maximum
achievable field of copper
magnets of ~ 0.15 T.
 =  
particle
 (/)
 ()
 (/)
 ()
proton
. 
. 
. 
−. 
deuteron
. 
. 
−. 
−. 

. 
. 
. 
−. 
• Fitting such a machine into the COSY building favors lower momenta.
• Could someone please check this!
[email protected]
EDM Searches in storage rings
18
EDM at COSY – COoler SYnchrotron
Cooler and storage ring for (polarized) protons and deuterons
 = 0.3 – 3.7 GeV/c
Phase space
cooled internal &
extracted beams
Injector cyclotron
[email protected]
COSY
… the spin-physics machine
for hadron physics
EDM Searches in storage rings
19
EDM at COSY – COoler SYnchrotron
Cooler and storage ring for (polarized) protons and deuterons
 = 0.3 – 3.7 GeV/c
Phase space
cooled internal &
extracted beams
Injector cyclotron
[email protected]
COSY
… an ideal starting point
for a srEDM search
EDM Searches in storage rings
20
Spin closed orbit
one particle with
magnetic moment
makes one turn
nˆCO “spin closed orbit vector”
“spin tune”

S A

SA
ring
A
[email protected]
2 s
stable
polarization

if S ║ nˆCO
EDM Searches in storage rings
21
Spin coherence
nˆCO
We usually don‘t worry about coherence of spins along
Polarization not affected!
At injection all
spin vectors aligned (coherent)
After some time, spin vectors get out of
phase and fully populate the cone

Situation very different, when you deal with S  nˆCO
nˆCO
Longitudinal polarization
vanishes!
At injection all spin vectors aligned
[email protected]
After some time, the spin
vectors are all out of phase
and in the horizontal plane
In an EDM machine with
frozen spin, observation
time is limited.
EDM Searches in storage rings
22
Estimate of spin coherence times (N.N. Nikolaev)
One source of spin coherence are random variations of the spin tune
due to the momentum spread in the beam
  G
and

is randomized by e.g., electron cooling
cos(t )  cos(t   )
 sc 
Estimate:
1
f rev G 2  2
1
f rev G 2 2v 4

 p 
 
 p
Tkin  100 MeV
f rev  0.5 MHz
 sc ( p)  3103 s
 sc (d )  5105 s
Tkin  100 MeV
2
1
f rev  0.5 MHz
Spin coherence time for deuterons may be ~ larger than for protons
[email protected]
EDM Searches in storage rings
23
First measurement of spin coherence time
2011 Test measurements at COSY
Polarimetry:
Spin coherence time:
5s
25 s
5s
decoherence oscillation
time
capture
[email protected]
EDM Searches in storage rings
from Ed Stephenson
and Greta Guidoboni
24
Topics





Why EDMs?
Search for EDMs using storage rings
Two projects, at BNL and Jülich
Spin coherence time
First direct measurement
Resonance Method with RF E(B) –fields
 Polarimetry
 Timeline of projects, cooperations, workshops
 Summary
[email protected]
EDM Searches in storage rings
25
Resonance Method with RF E-fields
spin precession governed by:
(* rest frame)
Two situations:
1. ∗ = 0   =  (= 70 G for  = 30 kV/cm)
2.  ∗ = 0   = −
RF E-field
EDM effect
no EDM effect
vertical
polarization
stored d
Polarimeter (dp elastic)
This way, the EDM signal is accumulated during the cycle.
• Statistical improvement over single turn effect is about: 1000s / 1s  105 .
• Brings us in the 10−24 ecm range for  .
• But: Flipping fields will lead to coherent betatron oscillations, with hard to
handle systematics.
[email protected]
EDM Searches in storage rings
26
Simulation of resonance Method with RF E-fields for
deuterons at COSY
Parameters:
beam energy
assumed EDM
E-field
Constant E-field
Number of turns
[email protected]
 = 50 MeV
 = 10−20 ecm
10 kV/cm
RF = 1 m
E-field reversed every
−/() ≈ 21 turns
Number of turns
EDM Searches in storage rings
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Simulation of resonance Method with RF E-fields for
deuterons at COSY
Parameters:
beam energy
assumed EDM
E-field
Linear extrapolation of P 
 = 50 MeV
 = 10−20 ecm
10 kV/cm
Px2  Pz2 for a time period of  = 1000 s (= 3.7108 turns)
EDM effect accumulates
Polarimeter determines
,  and 
Number of turns
[email protected]
EDM Searches in storage rings
28
Resonance Method with „magic“ RF Wien filter
Avoids coherent betatron oscillations of beam.
Radial RF-E and vertical RF-B fields to observe spin rotation due to EDM
Approach pursued for a first direct measurement at COSY.
 ∗ = 0   = −
„Magic RF Wien Filter“
no Lorentz force
„Indirect“ EDM effect
Tilt of precession plane
due to EDM
RF E(B)-field
stored d
Polarimeter (dp elastic)
Transverse
polarization
Observable:
Accumulation of vertical
polarization during spin
coherence time
Statistical sensitivity for  in the range − to −  range possible.
• Alignment and field stability of ring magnets
• Imperfection of RF-E(B) flipper
[email protected]
EDM Searches in storage rings
29
Operation of „magic“ RF Wien filter

Radial E and vertical B fields oscillate, e.g., with
=  +  ∙ rev = −54.151 × 103 Hz (here  = 0).
beam energy
 = 50 MeV
Spin coherence time may depend on excitation and on chosen harmonics 
(see Kolya Nikolaev‘s lecture).
[email protected]
EDM Searches in storage rings
30
Simulation of resonance Method
with „magic“ Wien filter for deuterons at COSY
Parameters:
beam energy
assumed EDM
E-field
 = 50 MeV
 = 10−24 ecm
30 kV/cm
RF = 1 m
Linear extrapolation of  for a time period of  = 1000 s = 3.7108 turns .
EDM effect accumulates in .

Preliminary, based on K. Nikolaevs derivation of the
combined rotation matrices of E/B flipper and ring


 = 2  = −3.402 × 105 Hz
turn number
[email protected]
EDM Searches in storage rings
31
Simulation of resonance Method
with „magic“ Wien filter for deuterons at COSY
Parameters:
beam energy
assumed EDM
E-field
 = 50 MeV
 = 10−24 ecm
30 kV/cm
RF = 1 m
Linear extrapolation of  for a time period of  = 1000 s (= 3.7108 turns).


EDM effect accumulates in 
turn number
[email protected]
EDM Searches in storage rings
32
Simulation of resonance Method
with Magic Wien filter for deuterons at COSY
Parameters:
beam energy
assumed EDM
E-field
 = 50 MeV
 = 10−24 ecm
30 kV/cm
 = 1 m
Linear extrapolation of  for a time period of  = 100000 s (= 3.71010 turns).

EDM effect accumulates in 
turn number
[email protected]
EDM Searches in storage rings
33
Some polarimetry issues
pC and dC polarimetry is the currently favored approach for
the pEDM experiment at BNL
srEDM experiments use frozen spin mode, i.e.,
beam mostly polarized along direction of motion,
most promising ring options use cw & ccw beams.
• scattering on C destructive on beam and phase-space,
• scattering on C determines polarization of mainly
particles with large betatron amplitudes, and

• is not capable to determine  =  .

• For elastic scattering longitudinal analyzing powers are tiny ( violates parity).
Ideally, use a method that would determine ().
[email protected]
EDM Searches in storage rings
34
Exploit observables that depend on
beam and target polarization

beam 1  = 

 (up)

target (or beam 2)  = 



Spin-dependent differential cross section for
1
2
+
1
2
1
1
→2+2
 (sideways)
 (along beam)

= 1 +   +  cos  −  +  sin 
0
+    cos2  +   sin2  +   +   sin  cos 
+    sin2  +   cos 2  −   +   sin  cos 
+    +   cos  +   +   sin 
+   
Analyzing power  =  
Spin correlations  =  ()
In  scattering, necessary observables are well-known
in the range 50 − 2000 MeV (not so for  or ).
[email protected]
EDM Searches in storage rings
35
How could one do that, determine  ?
Suggestion 1: Use a polarized H storage cell target
Detector
CW
CCW
cell
• Detector determines  of cw & ccw beams separately, based on kinematics.
• Alignment of target polarization  along , ,  axes by magnetic fields. Leads
to unwanted MDM rotations  absolute no-go in EDM experiments.
[email protected]
EDM Searches in storage rings
36
How could one do that, determine  ?
Suggestion 2: Use colliding beam from external source

cw beam  = 


0
0

probing beam  = Detector
0 ,  , or 0
 =


0
0

= 1 +   +  cos  −  +  sin 
0
+    cos2  +   sin2  +   +   sin  cos 
Polarized ion source
2  −   +   sin  cos 
+    sin2  +   cos(~10
MeV)
 
 
+    +   cos  +   +   sin 
+   
• Collide two external beams with cw and ccw stored beams.
• Energy could be tuned to match detector acceptance.
• Polarization components of probing low-energy beam can be made large, would
be selected by spin rotators in the transmission lines.
• Luminosity estimates necessary (Andro, David, Jörg)
[email protected]
EDM Searches in storage rings
37
How could one do that, determine  ?
Suggestion 3: Use directly reactions from colliding beams

cw beam  = 


ccw beam  = 

CW
Detector
CCW

= 1 +   +  cos  −  +  sin 
0
+    cos2  +   sin2  +   +   sin  cos 
+    sin2  +   cos2  −   +   sin  cos 
+    +   cos  +   +   sin 
+   
Requires luminosity, -functions at IP should be rather small.
• Advantage over suggestion 2. is that  supports luminosity.
• Disadvantage is that sensitivity comes mainly from terms with  and .
• Detailed estimates necessary (Andro, David, Jörg).
[email protected]
EDM Searches in storage rings
38
Luminosity estimate for the collider option
() =
Tmagic = 232.8 MeV
∙
1 2 rev ()
(, ) =
4()2
Luminosity
 = 0.1 m
Conditions:
 = 1 m
1 = 2 = 1011
 = 4
 ()
 ()
10
3.2
1
1
0.1
0.32
 =1m
 = 10 m
kinetic energy (MeV)
Even under these very optimistic assumptions, event rate will be rather low.
 =  × 
= 3.1 ∙ 1028 [cm−2 s−1 ] × 10−27 [cm2 mb−1 ] × 15[mb] ≈   −
[email protected]
EDM Searches in storage rings
39
Topics





Why EDMs?
Search for EDMs using storage rings
Two projects, at BNL and Jülich
Spin coherence time
First direct measurement
Resonance Method with RF E(B) –fields
 Polarimetry
 Timeline of projects, cooperations, workshops
 Summary
[email protected]
EDM Searches in storage rings
40
Technically driven timeline for pEDM at BNL
12
13
14
15
16
17
18
19
20
21
Two years R&D/preparation
One year final ring design
Two years ring/beam-line construction
Two years installation
One year “string test”
[email protected]
EDM Searches in storage rings
41
Stepwise approach in the JEDI project
Step Aim / Scientific goal
1
2
Device / Tool
Storage ring
Spin coherence time studies
Horizontal RF-B spin flipper
COSY
Systematic error studies
Vertical RF-B spin flipper
COSY
COSY upgrade
Orbit control, magnets, …
COSY
First direct EDM
measurement at − 
RF-E(B) spin flipper
Modified
COSY
3
Built dedicated all-in-one ring Common magneticfor p, d, 3He
electrostatic deflectors
Dedicated
ring
4
EDM measurement of p, d,
3He at − 
Dedicated
ring
Time scale:
[email protected]
Steps 1 and 2: < 5 years
Steps 3 and 4: > 5 years
EDM Searches in storage rings
42
srEDM cooperations
International srEDM Network
Institutional (MoU) and Personal (Spokespersons …) Cooperation, Coordination
srEDM Collaboration (BNL)
JEDI Collaboration (FZJ)
(spokesperson Yannis Semertzidis)
(spokespersons: A. Lehrach, J. Pretz, F.R.)
Common R&D
RHIC
Beam Position Monitors
(…)
EDM-at-COSY
Polarimetry
Spin Coherence Time
Cooling
Spin Tracking (…)
Study Group
DOE-Proposal (submitted)
CD0, 1, …
First direct measurement
Ring Design
HGF Application(s)
JEDI
pEDM Ring at BNL
[email protected]
EDM Searches in storage rings
43
EDM Workshop at ECT* (Trento)
October 1-5, 2012
http://www.ectstar.eu/
Organizing committee
 Jülich
Hans Ströher [email protected]
Frank Rathmann [email protected]
Andreas Wirzba [email protected]
 Brookhaven
Mei Bai [email protected]
William Marciano [email protected]
Yannis Semertzidis [email protected]
[email protected]
EDM Searches in storage rings
44
Summary
• Measurements of EDMs are extremely difficult,
but the physics is fantastic!
• Two storage ring projects, at BNL and Jülich
• All-in-one machine with copper-only magnets
• Pursue spin coherence time measurements at COSY
• First direct EDM measurement at COSY
Resonance Method with RF E(B) -fields
• Polarimeter concepts to be addressed by simulations
• JEDI collaboration established
[email protected]
EDM Searches in storage rings
45

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