guy savard argonne national laboratory and university of chicago

4th Workshop on Physics with a high-intensity proton sourceNovember 09-10 2009

Fermilab

Standard Model via Nuclear Physics

Guy Savard

Argonne National Laboratory

and

University of Chicago

2G. Savard Standard Model via Nuclear Physics November 9 2009

Outline

Fundamental interactions at low energy: basic approach

– Choose from the wide variety of available systems the one that selectively enhances or isolates the effect

• High Z simple atoms (Fr, Ra, Rn)• Clean decays (N=Z nuclei, n)

Opportunities offered by radioactive atoms/ions/neutrons

– Electric dipole moments (atoms, electron, neutron)

– Parity violation in atoms

– Determination of Vud and test of CKM unitarity

– Searches for interactions outside V-A

– …

Status


Search for an electric dipole moment and physics beyond the Search for an electric dipole moment and physics beyond the standard modelstandard model

+

-

+

-

-

+

T P

EDM Spin EDM Spin EDM Spin

A permanent EDM violates both time-reversal symmetry and parity

Neutron

Diamagnetic Atoms (Hg, Xe, Ra, Rn)

Paramagnetic Atoms (Tl, Fr)Molecules (PbO)

Quark EDM

Quark Chromo-EDM

Electron EDM

Physics beyond the Standard

Model:SUSY, Strings

…

To understand the origin of the symmetry violations, you need many experiments!


EDM measurements: the SM extension slayersE

xper

imen

tal L

imit

on

d (

e cm

)

1960 1970 1980 1990

Left-Right

10-32

10-20

10-22

10-24

10-30

MultiHiggs SUSY

Standard Model

Electro-magnetic

neutron:electron:

10-34

10-36

10-38

2000

10-20

10-30

Updated from Barr: Int. J. Mod Phys. A8 208 (1993)

any positive signal is new physics …

not SM


Schiff moment of 199Hg, de Jesus & Engel, PRC (2005)Schiff moment of 225Ra, Dobaczewski & Engel, PRL (2005)

Skyrme Model Isoscalar Isovector Isotensor

SkM* 1500 900 1500

SkO’ 450 240 600

Enhancement Factor: EDM (225Ra) / EDM (199Hg)

Enhancement mechanisms:• Large intrinsic Schiff moment due to octupole deformation;• Closely spaced parity doublet;• Relativistic atomic structure.

Haxton & Henley (1983)Auerbach, Flambaum & Spevak (1996)

Engel, Friar & Hayes (2000)

Enhanced EDM of 225Ra

55 keV

| |

Parity doublet


-1, 0, +1

Position-dependent force: Zeeman shifts from magnetic field

Need an arsenal of tools to accumulate radioactive atoms … e.g. Magneto-Optical Trap

xB

mJ

0

0 0

0

laser

+

Ground State J=0

Excited State J=1

Energy

In one dimension with J=0→J=1 transitionCreate damped harmonic oscillator: F = k∙v+Bx

-1

-1 +1

+1vk

Velocity-dependent force: Doppler shift alters laser frequency seen by atoms

x

xmagnetic field

Bx

-1, 0, +1


A proposed path for higher sensitivity: EDM of 225Ra at Argonne (Z.T. Lu et al.)

Oven:225Ra (+Ba)

Zeeman Slower

Opticaldipole trap

EDMprobe

Why trap 225Ra atoms• Large enhancement:

EDM (Ra) / EDM (Hg) ~ 200 – 2,000

• Efficient use of the rare 225Ra atoms

• High electric field (> 100 kV/cm)

• Long coherence times (~ 100 s)

• Negligible “v x E” systematic effect

Status and Outlook• First atom trap of radium realized

Guest et al. Phys Rev Lett (2007)

• Search for EDM of 225Ra in 2009

• Improvements will follow225RaNuclear Spin = ½

Electronic Spin = 0

t1/2 = 15 days

Magneto-opticaltrap


225Ra Source – Present and Future at a Rare Isotope Facility

• 1 mCi 229Th source 4 x 107 s-1 225Ra

• Projected EDM sensitivity: 10-26 – 10-27 e-cm

• Equivalent to 10-28 – 10-30 e-cm for 199Hg

• Current limit on 199Hg: 3 x 10-29 e-cm

229Th7300 yr

225Ra15 d

Present scheme

• Yield: 1 x 1012 s-1 225Ra

• Projected EDM sensitivity: 10-28 e-cm

• Equivalent to 10-30 – 10-31 e-cm for 199Hg

• Study systematics at 10-29 e-cm for 225Ra

Search for 225Ra EDM at a rare isotope facility

A similar improvement path is possible with Rn isotope EDM searches (see T. Chupp talk in Oct 09 workshop).


A proposed path to improve the e-EDM measurement

Best limit on the e-EDM comes from measurements with an atomic beam of Tl• 7 orders of magnitude improvements in 50 years• No improvements in the last 7 years

New technology needed atomic fountains – Demonstrate feasibility with Cs– Obtain best limit with Fr ( 9 times more sensitive to e-EDM)

• Fr production with 500 kW of 2 GeV protons would give a factor 100-1000 gain in Fr production over any existing facility

Experimental upper limits to the e-EDM 1962-2009

Proof-of-principle atomic fountain EDM experiment Photo courtesy of H. Gould


n-EDM searches … intense UCN sources needed

Source Type Ec (neV) UCN (UCN/cm3) Status Purpose

LANL Spallation/D2 180 35 Operating UCNA/ Users

ILL Reactor/ turbine 250 40 Operating n-EDM/ Users

Pulstar Reactor/D2 335 120 Construction Users

PSI Spallation/D2 250 1,000 Construction n-EDM

TRIUMF Spallation/ HE-II 210 10,000 Planning n-EDM/ Users

Munich Reactor/D2 250 10,000 R&D Gravity

SNS n beam/HE-II 130 400 R&D n-EDM

Large n-EDM experiment in preparation in the US at the SNS

UCN offer unique advantages for these studies and there is intense activity worldwide to create stronger sources

A few % of the 500 kW proton beam could provide a cutting edge facility for such studies in the US


Weak interaction between the outer electron and the nucleus

HG

Q rWF

W nuc8 5 ( )

QW(Experiment)*=-72.06±0.28exp±0.34th

QW(Standard Model)= -73.20First observation of anapole moment*PRL 82 (1999) 2484

for Cesium:

|nS>´=|nS>+|nP>valenceelectron

nucleus

weak interaction

alkali atom

valenceelectron

nucleus

weak interaction

alkali atom


The Boulder Cs PNC Experiment 1982-19991982-1999

• P-odd, T-even correlation: S• [E B]

• 5 reversals to distinguish PNC from systematics


A natural path to an improved APV experiment

Want a larger signal in a “simple” atom

– APV signal in Fr is 18X larger than in Cs

Remove theoretical uncertainties

– Dominating uncertainty comes from atomic physics corrections• Measurement on n-rich and n-deficient Fr isotopes

– Difference signal still larger than in Cs but dominating theoretical uncertainty is removed

– Next leading uncertainty from neutron distribution• 208Pb work at JLAB and hyperfine anomaly measurements

Get the counting rate

– Boulder Cs experiment used an atomic beam of 1013 /cm2/s

– Equivalent to about 108 Fr atoms in an optical trap … requires a beam of 1010-1012/s

Proposed Fr APV setup at TRIUMF


• Precision tests of CVC• Determination of weak vector coupling constant• Unitary tests of the CKM matrix

For superallowed transitions between 0+ T=1 states

Ft = ft ( 1 + R ) ( 1 – C ) =

from experiment; from calculations of radiative and charge-dependent effects

Test need for physics beyond the standard model Gv together with G yield the Vud quark mixing element of the CKM matrix

If matrix is not unitary then we need new physics Additional Z bosons, Right-handed currents, SUSY…

Superallowed Beta Decay

K2 GV

2 ( 1 + R )

Vud Vus Vub

Vcd Vcs Vcb

Vtd Vts Vtb

d’s’b’

dsb

=

weak eigenstates

mass eigenstates

rotation matrix

Big effect if R-parity violating … can be more than 0.0020

At loop level if R-parity conserving …. ~ 0.0007


Low energy experimental direction validate corrections

This capability is a direct consequence of having many candidates.


Sources of uncertainty in Vud determinations

2

4

6

8

10

12

14

16

18

2

4

6

8

10

12

14

16

18

2

4

6

8

10

12

14

16

18

Nuclear 0+ to 0+

Vud = 0.9738 0.0004

Neutron decay

Vud = 0.9740 0.0013 … or lower

Pion beta decay

Vud = 0.9760 0.0161

Uncertainty (10-4)

Exp

Exp

Exp

C

RRR

R

R

R

161

(latest n lower by 6.5


Status of CKM unitarity tests

•New Penning trap Q-value measurements have uncovered an omission in the isospin-symmetry breaking corrections which has been resolved

|Vud| = 0.97425 ± 0.00022

•taking that latest value for Vud together with

|Vus| = 0.22534 ± 0.00093 (from E865, KTeV, NA48, KLOE and FlaviaNet)

|Vub| = 0.00393 ± 0.00035

yields |Vud|2 + |Vus|2 + |Vub|2 = 0.99995 ± 0.00061

•The largest contribution to the error is from f+(0), followed closely by the uncertainty in the nucleus independent radiative correction to Vud

...2lnln4

2

Born

A

p

p

ZR Cm

mm

m

Reduced by a factor of 2 by W. Marciano


Further improvements possible

Neutron should eventually provide a complementary value for Vud, will be limited by the same radiative corrections, but susceptible to different new physics

• Intense UCN source is critical for these improvements

On the superallowed front, further improvement in experimental inputs will allow to better test the nuclei dependent corrections and further improve the value of Vud

• Weak branching ratios are critical and require RIB intensities in excess of what is currently available

Soon can obtain a higher precision test of unitarity independent of Vus and its associated uncertainties 2

1

))((

))(()4(2387.0

K

fV

fV

ud

Kus

A large improvement in the top row unitarity test is within reach … already sensitive to SUSY.


Nuclear Beta-Decay

d

u

W

Compare experimental values to SM predictions

Put limits on terms “forbidden” by SM

...1 D

EE

ppB

E

pA

E

pJb

E

ma

EE

ppdWdW

e

e

e

e

e

e

e

eo

Coupling constants: CS, CV, CA, CT

ePeP

eAeA

eTeT

eVeV

eSeS

CC

CC

CC

CC

CCH

5152

5152

512

512

512int

2

1

Differential Decay Rate:


Weak Interactions in Nuclei

Historically the VA structure of the weak interaction was determined by measurements of the beta-neutrino correlation in noble gas nuclei in the 1960’s

21Na

32Ar,38mK,14O

Today precise measurements of the beta-neutrino correlation are conducted to search for scalar or tensor contributions from exotic weak bosons.

New approaches using atom and ion traps provide ideal sources to improve the accuracy of these measurements.


Detector

Beryllium Window

MCP Detector

Mirror

Proton Beam from 88" Cyclotron

Transverse Cooling

Oven

MgO Disk Targets

Trapping Laser Beams

Radiation Shield Wall

Zeeman Slower

Slowdown Beam with "Dark Spot"

Trapping Laser Beams

Ne21

Na atom trap

+

Collimator Tubes

Radiation Shield Wall

+

MCP Field RingCollimator

Berkeley measurement of the Angular Correlation in Magneto-Optically Trapped 21Na

ddEeded

F Z, pe peEe E0 Ee 21 a

vc

cos e

2500

2000

1500

1000

500

0

coun

ts

25002000150010005000time of flight (ns)

21Ne

+

21Ne

+2

21Ne

+3 21Ne

0

2500

2000

1500

1000

500

0

Net

Counts

900800700600500400300

Time of Flight (ns)

-404

Resid

uals

Trap Data Monte Carlo Fit

Ideal Source: negligible source scattering sample is isotopically pure localized in small volume atoms decay at rest potential for polarized sample

500,000 trapped atoms

a deduced from TOF

Recoil-ion TOF

num

ber

of c

ount

s (a

rb. u

nits

)

900800700600

time of flight (ns)

a = 1

a = 0

21Na 3/2+3/2+ a = 0.5243±0.0091N.D. Scielzo et al., Phys. Rev. Lett. 93, 102501 (2004)


Measurement of A with UCN at LANSCE

Neutron AbsorberField Expansion Region

Detector 1 Detector 2

cos)()(

)()()(

21

21exp AP

ENEN

ENENEA

n

e

dW=[1+PAcos]d(E)


Requirements

The full modern low-energy arsenal– Penning traps– RFQ traps– magneto-optical traps– dipole traps– lots of laser power and build up cavities– radiation detectors (DSSD, MCP, HPGe, CCD)– lots of preparation, systematic checks– beamtime

Intense and pure low energy radioactive beams– lots of Fr … both n-rich and p-rich – highest achievable intensities of Rn, Ra – N=Z nuclei – UCN source

A facility based at the proton driver can provide the required beams.


Status

Physics Opportunity The availability of high-intensity sources of radioactive ions and ultra-cold neutrons opens up important opportunities to test the Standard Model at low energy. The candidates presenting the best characteristics (large enhancement or specific decay) can be selected to enhance the sensitivity to new physics. Technical Developments The technological developments in atom trapping, ion trapping, atomic clock, detector technology and related techniques further enhance these new capabilities. Competitiveness These combined advances will maintain the competitiveness and complementarity of these low energy tests of the Standard Model to work performed at the high-energy frontier.

guy savard argonne national laboratory and university of chicago

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