intro parity, time atom traps decay atomic xtra Atom Traps, parity, … · 2) A big ‘Standard...

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intro parity, time atom traps β decay P, T atomic P, T xtra Atom Traps, parity, and time-reversal violation By flipping spin, we can simulate applying: parity P time reversal T And test whether a system obeys P or T The standard model violates P Some new physics violates T How atom traps work, and what can be trapped How to spin-polarize a nucleus by shining light on it Tests in nuclear β decay Tests in francium, the heaviest alkali atom atom trap P, T J.A. Behr

Transcript of intro parity, time atom traps decay atomic xtra Atom Traps, parity, … · 2) A big ‘Standard...

Page 1: intro parity, time atom traps decay atomic xtra Atom Traps, parity, … · 2) A big ‘Standard Model’ success was predicting the Z0 3) Amount of atomic parity violation is sensitive

intro parity, time atom traps β decay P, T atomic P, T xtra

Atom Traps, parity, and time-reversal violation

• By flipping spin, we can simulate applying:

parity P

time reversal TAnd test whether a system obeys P or T

The standard model violates PSome new physics violates T

• How atom traps work, and what can be trapped

How to spin-polarize a nucleus by shininglight on it

• Tests in nuclear β decay• Tests in francium, the heaviest alkali atom

atom trap P, T J.A. Behr

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intro parity, time atom traps β decay P, T atomic P, T xtra

We once thought all interactions respected parity

=

As of 1956: all interactions parity symmetric

P

Parity operator: P : r r −

atom trap P, T J.A. Behr

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intro parity, time atom traps β decay P, T atomic P, T xtra

Then parity violation was discoveredA. Zee, Fearful Symmetry The weak interaction has a lot of P

P

θτ − Puzzle + 60Co decay imply1957:

=

atom trap P, T J.A. Behr

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intro parity, time atom traps β decay P, T atomic P, T xtra

Parity Operation can be simulated by Spin Flip

Under Parity operation P:

~r → -~r ~p ∼ d~rdt → -~p ~J=~r ×~p → +~J

ν

βAr

ν

β Ar

ν

βAr

P 180rotation37K 37K 37K

atom trap P, T J.A. Behr

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intro parity, time atom traps β decay P, T atomic P, T xtra

β decay: experimental discovery of parity violation

Wu et al. Phys Rev 105(1957) 1413Dilution Refrigeratorto spin-polarize60Co → β− + ν + 60Ni

W [θ] = 1 + AI ·~pβ

= 1 + Avc cos[θ]

A > 0.7

atom trap P, T J.A. Behr

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intro parity, time atom traps β decay P, T atomic P, T xtra

Sensitivity to wrong-handed leptons

K37 37Ar

e+

ν

forbidden independent of isospin mixing and Vud

atom trap P, T J.A. Behr

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intro parity, time atom traps β decay P, T atomic P, T xtra

Electroweak Interactions: what we “know”

• E&M unified with Weak interactionsγ ⇐⇒ Z0,W+,W−

1) Only spin-1 “vector” exchange bosons2) Only left-handed ν ’s: “parity is maximally violated”

• Things we can test:

1) Right-handed ν ’s ?

2) A big ‘Standard Model’ success was predicting theZ0

3) Amount of atomic parity violation is sensitive toextra Z bosons

atom trap P, T J.A. Behr

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intro parity, time atom traps β decay P, T atomic P, T xtra

Time Reversal• Physics motivation:Sakharov 1967 identified a way to generate theuniverse’s excess of matter over antimatter:but known CP (i.e. T) is short by 10 10

• Two types of experiment at TRIUMF:1) β Decay: • construct an observable from 3 vectorsthat change sign when t → -t. (e.g. ~p, or spin)• flip a vector, see if rate changes →mimics T reversal(Must correct theoretically for ‘final state’ effects)2) A permanent electric dipole moment in the groundstate of a system violates time reversal symmetry– notheory corrections

Other searches for CP: SuperB; ν T2K; K decayTREK; EDM’s in many systems

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intro parity, time atom traps β decay P, T atomic P, T xtra

Time reversal tests in decays

You can exactly simulate P application in decays thatway.Under Time reversal operation T :

~r →~r ~p ∼ d~rdt → -~p ~J=~r ×~p → -~J

Can also construct observables odd in time ~I · pβXpν

BUT flipping t is not the same thing as running thedecay backwards.Particles interact on the way out, and you don’treverse that part.

atom trap P, T J.A. Behr

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intro parity, time atom traps β decay P, T atomic P, T xtra

permanent EDM’s violate time reversal

Landau, Nucl. Phys. 3 (1957) p. 127

because the angular momentum is the only vector inthe problem.~d = constant~J~J

t→−t→ −~J

~d =∑

qi~ri ⇒ ~dt→−t→ +~d

If the physics is invariant under T , this is acontradiction, ⇒ constant= 0.This has no theory corrections

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intro parity, time atom traps β decay P, T atomic P, T xtra

Magneto-optical trap: damping

‘Optical molasses’

For a trap, we want a damped harmonic oscillator’Red-detuned’ beams provide the “damping”

We still need a position-dependent force

atom trap P, T J.A. Behr

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intro parity, time atom traps β decay P, T atomic P, T xtra

‘Light sabers’Atom traps would be easier if ‘light sabers’ worked

atom trap P, T J.A. Behr

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intro parity, time atom traps β decay P, T atomic P, T xtra

“Why Optical Traps Can’t Work”Earnshaw Theorem:

~∇ · ~E = 0⇒ no electrostatic potential minimum for charge-free region

“Optical Earnshaw Theorem” (Ashkin + Gordon 1983):

Using Poynting’s theorem:~∇ · ~S = c

4π~∇ · (~E x ~B) = −~J · ~E − ∂u

∂t = 0

⇒ no 3-D traps from spontaneous light forces with static lightfields

Dodges ! • Time-dependent forces (pulsed lasers)• Dipole Force traps (“optical tweezers”)• Modify internal structure of atom with externalfieldsatom trap P, T J.A. Behr

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intro parity, time atom traps β decay P, T atomic P, T xtra

‘Light sabers’~∇ · ~S 6= 0

Light sabers violate Poynting’s theorematom trap P, T J.A. Behr

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intro parity, time atom traps β decay P, T atomic P, T xtra

Magneto-optical trap

ε

ε

ε

ε

ε−

+

+

I

Bx

σσ + −J=0

J=1m=−10 1 −1

01

Raab et al. PRL 59 2631 (1987)

oscillator

Damped harmonic −

Zeeman Optical Trap (MOT)

ε =

I

s k.^ ^

ε−σ− +σ

σ − +σ

atom trap P, T J.A. Behr

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intro parity, time atom traps β decay P, T atomic P, T xtra

What elements can be laser cooled?

. .Here Be

H

MgDragons

Al

He

Na

SrCrCa

Ne

LANL,TRIUMF

Berkeley

TRIUMF

CsFr

RbK Kr

Xe

ArLi

Trapped in MOT Radioactives trappedLong−livedRad. Plans

LANL

ANL

ANL

Ba

ANL

KVI

Ra HgStonyBrook,

LegnaroJILA,

Raizen

Ag

Er YbDy

slain

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intro parity, time atom traps β decay P, T atomic P, T xtra

How to spin-polarize a nucleus with a laserPolarization of nuclei by Optical Pumping

Biased random walkSimple example:

J’ = 1/2

J = 1/2

m = −1/2 m =+1/2J J

σ +

P(m=1/2) = 1 - (2/3)N after Nsteps

Need 12 photons absorbed toget to 99% of maximum.

z

σ+(∆m = +1)

atom trap P, T J.A. Behr

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intro parity, time atom traps β decay P, T atomic P, T xtra

Why does this polarize the nucleus?

. .

4P1/2Γ= 6 ΜΗz

4S1/2

F=2F=1

F=1F=2

σ+m=+1∆

m=−2 −1 0 1 2~F = ~J +~IHhyperfine = - ~µN · ~Be = A~I · ~J

P=97.7±0.6% 37K (2007)

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intro parity, time atom traps β decay P, T atomic P, T xtra

TRINAT’s secret location at ISAC

atom trap P, T J.A. Behr

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intro parity, time atom traps β decay P, T atomic P, T xtra

TRIUMF’s Neutral Atom Trap• Isotope/Isomer selective• Evade 1000x untrapped atom background by → 2nd MOT• 75% transfer (must avoid backgrounds!); 10 −3 capture• 0.7 mm cloud for β-Ar+ → ν momentum →

β-ν correlation• 99% polarized, known atomically (in progress)

atom trap P, T J.A. Behr

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intro parity, time atom traps β decay P, T atomic P, T xtra

TRINAT lab: “tabletop experiment”

atom trap P, T J.A. Behr

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intro parity, time atom traps β decay P, T atomic P, T xtra

ion MCP assembly

electrostatic field, delay-line anodeatom trap P, T J.A. Behr

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intro parity, time atom traps β decay P, T atomic P, T xtra

New Apparatus, beamtime Dec 201237K 1-2% β and recoil asymmetries w.r.t. Nuclear SpinGoals: ∼0.2% to test standard model

e+

37Ar

e−

νI

Re

coil

asy

m

5−5

Ion MCP Y [cm]

0.601 +− 0.023 Ar+1,2,3

0

atom trap P, T J.A. Behr

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intro parity, time atom traps β decay P, T atomic P, T xtra

Mott scattering Time reversal ViolationRikkyo U., J. Murata R ~σβ ·~Ix ~pβ

t→−t→ −R ~σβ ·~Ix ~pβ T P

Y. Totsuka ISAC Sci For Dec 2011CDC, fast Triggering & TDC in single FPGAfrom TRIUMF: 80% ~8Li 107/s (Levy, Pearson)

2011: tested more symmetric cylindrical chamber2012: finalize result 2010 MWDC 0.001 stat ( ∼ PSI)2013: complete CDC setup for physics productionFuture depends on R: study FS effects ( ∝ AβZ/p),other decays, F/GT (possibly 19Ne, 21Na, 37K)

atom trap P, T J.A. Behr

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intro parity, time atom traps β decay P, T atomic P, T xtra

Time Reversal: DecaysTRINAT pre-proposal for D ~I · ~pβX ~pν T odd, P evenDo observables evade EDM constraints?

Ng,Tulin PRD 2012 ‘no’emiT (neutron) 2011: D= -0.96 ± 1.89 ± 1.01 × 10−4

Dedicated geometry: statistics 2x10 −4 in 2 weeks

atom trap P, T J.A. Behr

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intro parity, time atom traps β decay P, T atomic P, T xtra

atom trap P, T J.A. Behr

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intro parity, time atom traps β decay P, T atomic P, T xtra

EDM’s in an atomic fountain (LOI from LBL)Amini PRA 2007 (L.B.L.)H = −~d · ~ELook for a change in orientationlinear in ~E• Interrogate atoms in free space,no trapping fields• toss atoms up+down, interrogate2x, systematics cancel• ~v near 0 (minimizes vXB)

|ψm=+4|2

+|ψm=−4|

2

‘Ramsey fringes’:Only interrogate atstart and finishConcentrate countingduring the Nth period,win by 1/N in error

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intro parity, time atom traps β decay P, T atomic P, T xtra

TRIumf Neutral Atom Trap collaboration

**S. Behling**B. Fenker**M. Mehlman* P. ShidlingD. Melconian

*A. GorelovJ.A. BehrM.R. PearsonK.P. Jackson

**M. Anholm

G. Gwinner

D. Ashery

UndergradC. Farfan, McGill

** Grad student * PDF

Supported by NSERC, NRC through TRIUMF, WestGrid, IsraelScience Foundation

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intro parity, time atom traps β decay P, T atomic P, T xtra

Atom Traps, parity, and time-reversal violation

• By flipping spin, we can simulate P and T flips

• Atom traps provide:ν momentum

well-defined source withknown polarization

Bright source of scarce atoms

And test standard model physics in:• Nuclear β decay• Francium, the heaviest alkali atom

atom trap P, T J.A. Behr

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intro parity, time atom traps β decay P, T atomic P, T xtra

Why the weak interaction is ’weak’ at low energy

‘more massive virtual particles are created for shortertimes’

Propagator+vertices:

T ∝GX (−gµν+pµpν/M2

X )GX

p2−M2X

p<<MX−→

T ∝G2

XM2

X⇒

gX

νβ

p

nG G’

Xx x

Decay rates ∝G4

XM4

X

Decay rate ∝ G2

M2W

G2X

M2X

if process interferes with W (couples

to left-handed ν)• IF GX ∼ electroweak coupling, then absence of0.1% changes in angular correlations ⇒ MX > 6 or 30 MW

• But if GX small, then MX can still be small. Popular inneutral boson models, motivated by particle astrophysics

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intro parity, time atom traps β decay P, T atomic P, T xtra

Parity violation in francium atoms

e e

N N

γ

e e

Z 0

NN

8p

7p

7s

8s

• Z0 mixes states of opposite parity 7s → 7(s+ǫ p) .Parity-violating E1 PV is 10−18 of one-electron strength

• Atomic PNC ∼ Z2 N, in Fr ≈ 18x larger than in CsThe atomic theory has been done to 1% accuracy andCs-like accuracy of 0.3% should be possible.

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intro parity, time atom traps β decay P, T atomic P, T xtra

‘Charge-neutral’ Weak Interactions

• 1st seen in ν scattering(close race with nuclear andatomic PNC)• Present goal: need ∼0.001accuracy to test s.m.Diener et al. arXiv1111.4566 inLittle Higgs models m′

Z≥ 1.6TeV from Cs APNC

0.0001 0.001 0.01 0.1 1 10 100 1000 10000

0.225

0.230

0.235

0.240

0.245

0.250

current

future

standard model

APV

Qweak(arbitrarily placed on ordinate)

E158NuTeV

Z-pole

AFB

Q [GeV]sin2θw

Atomic PNC is tiny, ∼ 10−9 of E&M ⇒ Apossible new interaction hypothesized forlow-mass dark matter must have parityconserving couplings. C. Bouchiat and Fayet,PLB 608 (2005) 87

WeidenspointnerNature 2008

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Stark - Weak interference: flip E field

Wieman’s Cs scheme is what we want toemulate in Fr...|A7s→8s|

2 = |E1Stark + E1PNC|2

8p

7p

7s

8s

|A7s→8s|2 ≈ |E1stark|

2 + 2E1StarkE1PNC

The interference term is ∼ 10−9 of an allowed E1 transitionamplitude (rather than 10 −18).

so flipping ~E changes the rate, with an asymmetry linear inE1PNC. You are free to choose |~E|.

• Then you have to calculate (or, preferably, measure)AStark to extract E1PNC

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EDM’s very small in standard modelFortson, Sandars,Barr, Physics Today2003Experiments have onlyseen upper limitsde− < 10−19e-Adn < 10−12e-fm

The Standard Model only has 1 source oftime-reversal violation. This cancels itself out atlowest order (“1 loop”) in making an EDM.Most new physics has more sources of time-reversalviolation, so they don’t cancel at lowest order, so yougenerate EDM’s

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Why atom traps are shallow

|e>

|g>

γ=1/τspontaneousemission

stimulatedemission

absorption

"Einstein B" "Einstein A"

Ω Ω

dNg

dt = −ΩNg + ΩNe + γNe = −dNedt

Steady-state ⇒ =0 ⇒ Ne =ΩNg

Ω+γ

Limits: NeΩ<<γ→ Ω

γNg (sure); Ne

Ω>>γ→ Ng !!

• At high intensity, same # in ground, excited stateAtomic transition “saturates”Maximum scattering rate = γNe/N → γ/2so radiation pressure traps are shallow IF they rely onspontaneous emission

atom trap P, T J.A. Behr