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 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
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
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
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
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
Eβ
= 1 + Avc cos[θ]
A > 0.7
atom trap P, T J.A. Behr
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
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
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
atom trap P, T J.A. Behr
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
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
atom trap P, T J.A. Behr
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
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
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
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
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
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
atom trap P, T J.A. Behr
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
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)
atom trap P, T J.A. Behr
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
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
intro parity, time atom traps β decay P, T atomic P, T xtra
TRINAT lab: “tabletop experiment”
atom trap P, T J.A. Behr
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
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
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
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
intro parity, time atom traps β decay P, T atomic P, T xtra
atom trap P, T J.A. Behr
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
atom trap P, T J.A. Behr
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
atom trap P, T J.A. Behr
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
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
atom trap P, T J.A. Behr
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.
atom trap P, T J.A. Behr
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
atom trap P, T J.A. Behr
intro parity, time atom traps β decay P, T atomic P, T xtra
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
atom trap P, T J.A. Behr
intro parity, time atom traps β decay P, T atomic P, T xtra
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
atom trap P, T J.A. Behr
intro parity, time atom traps β decay P, T atomic P, T xtra
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