# Presentation: 375949

## dEDM

- First of a new class:
- EDM searches on charged particles
- using the **E=**γ**v****×B** field of a storage ring

- deuteron electric dipole moment

- 2007 RHIC & AGS Annual Users’ Meeting, June 18-22

**+**

**–**

**+**

**–**

**+**

**–**

- Time reversal
- violation:
-    x → x
-    t → –t
-    s → –s

- Parity violation:
-    x → –x
-    t → t
-    s → s

**+**

**–**

- Baryon asymmetry of the universe
- requires new sources of CP-violation.
- One indicator would be the observation
- of an intrinsic EDM.

- Best theoretical candidate is SUSY.
- Next 103 crucial test: find it or die.

- _Other EDM limits:_

- neutron  < 2.9 × 10–26 e·cm,  PRL **97**, 131801 (’06)
- electron  < 1.6 × 10–26 e·cm on Tl,  PRL **88**, 071805 (’02)
- atom  <  2.1 × 10–28 e·cm on 199Hg,  PRL **86**, 2505 (’01)
- 	(but really  < 4 × 10–25 e·cm on neutron)

- (Statistical) goal for deuteron: 10-29 e·cm

- Ed Stephenson, IUCF

## Why start with the deuteron?

- _Technically_:

- Polarized ion sources make intense beams, polarization >90%.
- Forward angle deuteron scattering very sensitive to polarization.

- _Physically_:

- The deuteron has a special sensitivity to chromo-EDMs.

- Compared to the neutron:

- Information independent of neutron,
- _complementary_ within systematic study.
- Deuteron structure is well determined.

- At 10-29 e·cm:

- Sensitivity to equivalent mass:  103 TeV
- Sensitivity to CP-violating phase:  10-5

- (beyond reach of LHC)

## Status of Letter of Intent

- presented to fall 2006 PAC

- The PAC is in favor of
- the physics goals.

-       The PAC favors
-    an R&D program
- of ring simulations and
- polarimeter tests.

- (supported again in spring 2007)

- BNL plans to provide LDRD:
-    $ 230 K in FY 2007-08
- applied for $ 700 K in FY 2008-10

- Also from the Netherlands:
-      600 K€ already granted

- Goal:  demonstrate
- feasibility of technique

- (Included in nuclear
- physics long-range plan)

## What is the method?

- EDM Signal: observe precession
- of spin in large electric field.

- Technique: create large E
- field from γ**v****×B** on polarized
- beam circulating in a ring.

**E**

**v**

- Experiment: watch for spin
- that starts out along **v** to
- acquire a vertical component.

## What is the method?

- EDM Signal: observe precession
- of spin in large electric field.

- Technique: create large E
- field from γ**v****×B** on polarized
- beam circulating in a ring.

**E**

**v**

- Experiment: watch for spin
- that starts out along **v** to
- acquire a vertical component.

- Main technical challenge: rapid spin
- precession due to magnetic moment
- cancels EDM every rotation.
- Solution: create synchrotron-spin
- resonance to accumulate EDM signal.

- Requirements:
-   prepare/preserve horizontal polarization
-   monitor in-plane phase and frequency
-   monitor growth of vertical polarization

- with velocity oscillation synchronized to polarization:

- vertical polarization
- from EDM

- time

- observe
- average
- polarization

- But precession in magnetic
- field is much faster!

**B**

- At 10-29 e·cm,
- effect is py=10-7
- after 1000 s

## Characteristics of

**the EDM ring**

- an example:

- Superconducting RF cavities (D=0)
-    keep beam bunched (preserve p)
-    force synchrotron oscillations

- Chromaticity:

- suppresses
- harmonics

- Polarization cancellations:
-    flip polarization at source
-    opposite synchrotron phase on
-       different beam bunches

- Electro-magnetic quads to reduce
-    sensitivity to betatron oscillations.

- Issues:

- Oscillating **B****r  **(from skew quad)
- Polarization coherence time
- Collective effects (space charge, etc.)

- ... do simulations !

- Consider CW and CCW operation

## Storage Ring Development Plan

- Specify (set of) ring lattices for study.

- Determine non-linear fields need to preserve horizontal polarization.

- Include multiple errors, check for interactions.

- Add EM fields from collective effects (space charge, images).

- Vary β-functions around ring, find systematic signals.

- Study non-linear solution to cancel ωa oscillations.

- Examine tolerances on ring construction.
- Test concepts for error reduction or cancellation.
- Specify polarimeter requirements.

- Timetable: 2007-08

- angle

- nuclear

- Coulomb

- useful for
- spin (17 mb)

- lost to ring
- acceptance
- (2 kb)

- cross
- section

- 40 MeV: 10-5
- 1 GeV: 6x10-4

- IDEA:
-  make thick target defining aperture
-  scatter into it with thin target

- D

- L

- U

- R

- “extraction”
- target - gas

- “defining aperture”
- primary target

- detector
- system

- (Other thick target efficiencies
- typically several percent)

- (carbon best material)

- Increased efficiency comes from
- greater target thickness.

- If hole in target is ring defining
- aperture, then all particlea are
- lost there regardless of what
- perturbed their course.

- _Asymmetries_

- carries EDM signal
- small
- increases slowly with time

- carries in-plane precession signal
- large
- oscillates rapidly, slowly decreases

## Operating characteristics

- for d+C polarimeter

- fraction of
- deuterons that
- hit the target
- and scatter
- into a range
- useful for spin
- measurement

- split between:

- left-right

- down-up

- figure of
- merit

- (optimizations
- for better iT11)

- best
- operation

- lab angle (deg)

- 0

- 0.0

- 10

- 20

- 30

- Sample data
- d + C, 270 MeV

- Use peak
- for spin
- measure-
- ment

- Effect goes as:

## Polarimeter development

**at COSY (J****ülich)**

- broad range
- data from
- WASA

- polarimeter
- test data
- from EDDA

- Developments needed

- annular carbon targets (EDDA)
- needle carbon (CH2) (WASA)

## Results from COSY PAC

- Support for the
- physics goals.

- Beam time granted (but
- not scheduled) for first
- goal:  high efficiency
- polarimeter with annular
- carbon target.

-     Remaining goals:
- make horizontal polarization
- measure in-plane precession
- check sensitivity to
-    synchrotron oscillations
- measure cross section and
-    analyzing power for
-    deuteron-induced reactions

- Running to be scheduled
- in early 2008 through 2010

- May, 2007

## Systematic Error Studies (an example)

-    spin reversal (at source, in different bunches)
-          combined with cross-ratio calculations
-    correct time dependence
-          depolarization confirmed from in-plane values

- _An illustration:_

- angle error

- position error

- θ

- θ

- both represented by θ

- Fix problem with spin-flip and cross ratio:

- Systematic effects come at higher order
- and constrain allowed size of θ.

- ~0.1

- ~ –0.07

- asymmetry
- ~ 0.01
- (residual py)

- requires θ < 0.02°
- difference + to  –

- u = p+ + p–

- Challenge:
- Predict these terms
- from Monte Carlo,
- then check in lab.
- This demonstrates
- methodology.

- _Systematic Error Studies (an example)_
- _KVI, Groningen, the Netherlands_

## Summary of dEDM project status

- Resonant method appears feasible, statistical limit ~10-29 e·cm

- BNL PAC supports physics goals, R&D to determine feasibility

- Spin tracking to test ring lattice designs

- Polarimeter proof-of-principle tests

- Technical review

- Full proposal

- _Future_:

## Storage 

_**S**__**torage **_
_**R**__**ing **_
_**E**__**DM**_
_**C**__**ollaboration**_

- Presented to the BNL
- PAC, September 2006.

- Additional for COSY:

- NFM Brantjes, KVI
- R Gebel, COSY
- K Jungman, KVI
- A Lehrach, COSY
- B Lorentz, COSY
- R Messi, U. Rome
- D Prasuhn, COSY
- M da Silva, KVI
- L Willmann, KVI
- HW Wilshut, KVI