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Gabrielse
Most Precise Tests of the Standard Model,
Its Extensions and its Symmetries
Gerald Gabrielse, Leverett Professor of Physics, Harvard University
Spokesperson of the CERN ATRAP Collaboration
Testing the Most Precise Prediction of the Standard Model
 Electron magnetic moment
Testing standard model extensions
 Electron electric dipole moment
Testing the Symmetries of the Standard Model
 Q/M for the antiproton and proton
 Antiproton and proton magnetic moments
 Positron and electron magnetic moments (underway)
 Antihydrogen and hydrogen structure (still in far future)
Comparing Antimatter and Mater Gravity
 Gravitational Redshift of the Antiproton and Proton
Supported by US NSF and AFOSR
Gabrielse
Low Energy Particle Physics
AMO Physics, Particle Physics, Plasma Physics
methods and funding
can’t avoid
goals and facility
2M p c 2
LEAR and AD
1010
TRAP
4.2 K
0.3 meV
70 mK, lowest storage energy
for any charged particles
Gabrielse
Gabrielse
Electron Magnetic Dipole Moment
• Most precise prediction of the standard model
• Most precisely measured property of an elementary
particle
• Most precise confrontation of theory and experiment
• Greatest triumph of the standard model
Gabrielse
The Amazing Electron
Electron orbits give atoms their size, but the electron itself
may actually have no size
R  2 10
20
m
m*  10.3 TeV / c
2
20000 electron masses
of binding energy for
“ingredients”
Electron has angular momentum (spin) even though it has no
size and nothing is rotating: S  m R 2 
  IA ~  R 2
Magnetic dipole
 moment:
S


/2
What about electric dipole?


S
d d
/2
Gabrielse
Standard Model of Prediction

 
 
 
 
 
 1  C2    C4    C6    C8    C10    ...
B
 
 
 
 
 
 a hadronic  aweak  anew physics
2
e
2m

3
4
5
1
Dirac
QED
essentially
exact
Hadronic
Weak
aweak
smaller
Gabrielse
The Standard Model Predicts
the Electron Magnetic Moment
in terms of the
fine structure
constant
1 e2
1


4 0 c 137
Gabrielse
Probing 10th Order and Hadronic Terms
Dirac
QED
Gabrielse
David Hanneke G.G.
Shannon Fogwell
Gabrielse
Need Good Students and Stable Funding
20 years
8 theses
Elise Novitski
Joshua Dorr
Shannon Fogwell Hogerheide
David Hanneke
Brian Odom,
Brian D’Urso,
Steve Peil,
Dafna Enzer,
Kamal Abdullah
Ching-hua Tseng
Joseph Tan
N$F
Gabrielse
Cylindrical Penning Trap
V ~ 2z
2
 x2  y
2
• Electrostatic quadrupole potential  good near trap center
• Control the radiation field  inhibit spontaneous emission by 200x
(Invented for this purpose: G.G. and F. C. MacKintosh; Int. J. Mass Spec. Ion Proc. 57, 1 (1984)
Trap with
charges
Gabrielse
One Electron Quantum Cyclotron
-------
f c  150 GHz
n=4
n=3
n=2
n=1
n=0

2
hc  7.2 kelvin
y
-------
B  6 Tesla
Need low
temperature
cyclotron motion
T << 7.2 K
0.1
µm
2
0.1
µm
Gabrielse
Quantum Measurement of the Electron Magnetic Moment
E  ms s  (n  1/ 2)c
 
Spin flip energy: s     B  2  B
eB
Cyclotron energy: c  
 2 B B
m
(the magnetometer)

S


/2
s


c
B
Bohr magneton e
2m
Need to resolve the quantum states of the cyclotron motion
 Relativistic shift is 1 part in 109 per quantum level
Gabrielse
Quantum Jump Spectroscopy
• one electron in a Penning trap
• lowest cyclotron and spin states
“In the dark” excitation
 turn off all detection
and cooling drives
during excitation
Gabrielse
Inhibited Spontaneous Emission
excite,
measure time in excited state
t= 16 s
20
10
0
0
10
20
30
40
50
60
15
12
9
Y Axis 2
30
axial frequency shift (Hz)
number of n=1 to n=0 decays
Application of Cavity QED
6
3
0
-3
0
100
200
tim e (s)
decay time (s)
many other new methods
300
Most precisely measured property of an elementary particle
Electron Magnetic Moment Measured
to 3 x 10-13
2.8 1013
(improved measurement is underway)
Gabrielse
Gabrielse
from measured
fine structure constant
From Freeman Dyson – One Inventor of QED
Gabrielse
Dear Jerry,
... I love your way of doing experiments, and I am happy to congratulate you for
this latest triumph. Thank you for sending the two papers.
Your statement, that QED is tested far more stringently than its inventors could
ever have envisioned, is correct. As one of the inventors, I remember that we
thought of QED in 1949 as a temporary and jerry-built structure, with
mathematical inconsistencies and renormalized infinities swept under the rug. We
did not expect it to last more than ten years before some more solidly built theory
would replace it. We expected and hoped that some new experiments would
reveal discrepancies that would point the way to a better theory. And now, 57 years
have gone by and that ramshackle structure still stands. The theorists … have kept
pace with your experiments, pushing their calculations to higher accuracy than we
ever imagined. And you still did not find the discrepancy that we hoped for. To
me it remains perpetually amazing that Nature dances to the tune that we scribbled
so carelessly 57 years ago. And it is amazing that you can measure her dance to
one part per trillion and find her still following our beat.
With congratulations and good wishes for more such beautiful experiments, yours
ever, Freeman.
Gabrielse
Test for Physics Beyond the Standard Model

g

  1  aQED ( )   aSM :Hadronic Weak   aNew Physics
B 2
Does the electron have internal structure?
m*  total mass of particles bound together to form electron
R  5 10
19
m
R  2 1019 m
m
 360 GeV / c 2
a
m
m* 
 1 TeV / c 2
a
m* 
limited by the uncertainty in
independent α value
if our uncertainty
was the only limit
Not bad for an experiment done at 100 mK, but LEP does better
R  2 1020 m
m*  10.3 TeV / c 2
LEP contact interaction limit
> 20000 electron masses of binding energy
Gabrielse
Gabrielse
Electron Electric Dipole Moment
• Most precise test of extensions to the standard model
• 12 times more precise than previous measurements
Magnetic moment:

S


/2
Well measured
Electric dipole moment:


S
d d
/2
Does this also exist?
Gabrielse
Particle EDM Requires Both P and T Violation
Magnetic moment:

S


/2
P
T
Electric dipole Moment:


S
d d
/2
If reality is invariant under parity
transformations P
 d=0
If reality is invariant under time reversal
transformations T
 d=0
Gabrielse
Standard Model of Particle Physics
 Currently Predicts a Non-zero Electron EDM
Standard model: d ~
10-38
e-cm
Too small to measure by orders of magnitude
best measurement: d ~ 2 x 10-27 e-cm
Weak interaction couples quark pairs (generations)
CKM matrix relates to d, s, b quarks
(Cabibbo-Kabayashi-Maskawa matrix)
almost the unit matrix
four-loop
level in
perturbation
theory
Gabrielse
Extensions to the Standard Model
 Much Bigger, Measureable Electron EDM
An example
Low order contribution
 larger moment
Low order contribution
 vanishes
From Fortson, Sandars and Barr, Physics Today, 33 (June 2003)
Gabrielse
New Electron EDM Measurement is Almost Done
Gabrielse
Advanced Cold-Molecule Electron EDM
Harvard University
Yale University
John Doyle Group
David DeMille Group
Gerald Gabrielse Group
Jacob Baron, Wes Campbell,
David DeMille, John Doyle,
Gerald Gabrielse, Paul Hess,
Nick Hutzler, Emil Kirilov,
Brendon O’Leary, Cris Panda,
Elizabeth Petrik, Ben Spaun,
Amar Vutha, Adam West
Funding from NSF
Gabrielse
How to Measure an Electron EDM
Put the EDM in an Electric Field
 
H  d  E
bigger is better
Measure the energy shift for the system
Cannot Use Electric Field Directly
on an Electron or Proton
Gabrielse
Simple E and B can be used for neutron EDM measurement
(neutron has magnetic moment but no net charge)
Electric field would accelerate an electron out of the apparatus
Electron EDM are done within atoms and molecules
(first molecular ion measurement is now being attempted)
Gabrielse
Schiff Theorem – for Electron in an Atom or Molecule
Schiff (1963) – no atomic or molecular EDM (i.e. linear Stark effect)
• from electron edm
• nonrelativistic quantum mechanics limit
Sandars (1965) – can get atomic or molecular EDM (i.e. linear Stark
effect)
• from electron edm
• relativistic quantum mechanics
• get significant enhancement (D >> d) for large Z
Commins, Jackson, DeMille (2007) – intuitive explanation Schiff
 Lorentz contraction of the electron EDM in lab frame
Schiff, Phys. Rev. Lett. 132, 2194 (1963);
Sandars, Phys. Rev. Lett. 14, 194 (1965); ibid 22, 290 (1966).
Commins, Jackson, DeMille, Am. J. Phys. 75, 532 (2007).
Gabrielse
Why Use a Molecule?
 To Make Largest Possible Electric Field on Electron
Tl atom (best EDM limit till YbF)
Elab  123 kV/cm

E eff  72 MV/cm
ThO molecule
Elab  100 V/cm

E eff  100 GV/cm
Molecule can be more easily polarized using nearby energy levels with
opposite parity (not generally available in atoms)
Gabrielse
 Detect the Energy Difference
S

two states evolve differently in time
  g
/ 2
 i  E t / hbar 


S
de  de
/ 2
e
Gabrielse
Still, the EDM Gives Tiny Shift of Energy Levels
E  7  1018 eV
2 mHz
 7 1027 GeV
Not so easy to resolve
 7 1030 TeV
To detect  let a prepared wave function evolve for time T
|  (0)  |1  | 2

|  (T)  |1  e
 i
| 2
large as
possible
E

T

T  1.1 ms    11 106  0.6  103 degrees
Example is for an electron edm equal the ACME upper limit.
Gabrielse
Experiment in Two Labs – 100 Meters Separated
Harvard Jefferson Building
Harvard LISE Building
100 m optical fibers
Lasers, Iodine Clock, Comb
ThO Source
and Interaction
Chamber
(2 floors down)
Gabrielse
ThO Molecular Beam
Pulse Tube Cooler
Molecular
Beam
Source
“Interaction
Region”: Efield plates
inside, Bfield shields
and coils
outside
Pulsed
YAG
Prep
Lasers
Probe Lasers
Lasers
100m away
34
Gabrielse
Magnetic Field Coils and Shielding
mu metal
endplates
ThO beam
Cos(theta)
coils to
provide
transverse
B field
5 shields
(no shown)
~ 10-5
shielding
Interaction
chamber
inside
200 mG with uniformity of 10-3 over 26 cm
Gabrielse
Detect the Tiny Phase Shift  Interference
set by choice
of dark state
m 1  eio m 1
2
set by choice of direction of
the first of the two orthogonal
detection laser polarizations
m 1  ei ( o 1 ) m 1
2
  (  B  d E)
 maximize sensitivity to   d E   11 106
Gabrielse
Detecting an EDM
ground state superposition evolve: E +
edm
cold
ThO
source
combine
emit
E B
electric field plates
magnetic field
light
detector
apparatus control
and data acquisition
Gabrielse
Total Phase Equation:
, ,
=
+Δ
+
++-
B0 g m t
Bnr ∆g m t
-+-
B0 ∆g m t
---
de Eeff t
B0 η Enr m t
phase (rad)
0
3±5
x 10-5 rad
block (~1 min)
Bleak g m t
-++
--+
phase (rad)
Bnr g m +tθnr
+--
single block
10 blocks averaged
Derived quantities
+++
+-+
+
392 ± 5
x 10-5 rad
block (~1 min)
phase (rad)
Parity sum (NEB)
+
??? ± 5
x 10-5 rad
block (~1 min)
phase (rad)
single block
10 blocks averaged
+-+
Bleak g m t
0
-++
Bnr ∆g m t
-+-
B0 ∆g m t
--+
---
de Eeff t
phase (rad)
B0 g m t
phase (rad)
++-
-3590 ± 5
x 10-5 rad
-2 ± 5
x 10-5 rad
block (~1 min)
phase (rad)
Bnr g m +tθnr
+--
block (~1 min)
Derived quantities
+++
-1530 ± 5
x 10-5 rad
B0 η Enr m t
4±5
x 10-5 rad
block (~1 min)
phase (rad)
Parity sum (NEB)
Gabrielse
-1 ± 5
x 10-5 rad
block (~1 min)
Gabrielse
Gabrielse
Constraining New Physics on the 1 to 3 TeV Scale
for weak interactions
~4/137
prefactor
conservative
difficult to suppress
new CP violating phase
mass scale of
new particles
couples to weak interaction via
n=1 or n=2 loop diagrams
3 TeV 1 TeV
Probing same mass scale as the LHC
Gabrielse
We need molecular theory
to get the effective electric field
We actually constrain the EDM and CS
Assuming d=0
Gabrielse
New ACME Electron EDM Measurement
New ACME Result
Gabrielse
How Big is 8 x 10-29 e cm?
How sensitive was our princess
to the hidden pea?
Scale size of the polarization cloud
around the electron  earth
Shift in earth center by 2 nm
earth-sized
polarization cloud
around electron
(scale classical
electron radius)
Gabrielse
Relationship to LHC Physics
The LHC is exciting and important but EDMs also play a role
• should get an improved electron EDM on the LHC time scale
• If the LHC sees new particles, is CP violation involved?
• If the LHC sees nothing, EDM game is the only one in town
• Would be great to use LHC results and ours together to see what
we have learned together about Standard Model extensions
Gabrielse
https://twiki.cern.ch/twiki/pub/AtlasPublic/CombinedSummaryPlots/AtlasSearchesSUSY_SUSY2013.pdf
Gabrielse
Gabrielse
Testing the Standard Model’s
Fundamental Symmetry
and
Comparing Antimatter-Matter Gravity
Gabrielse
Single Particle Measurements
Have Three Big Advantages
Can be done with antiparticles
Can reach a much higher precision
Direct measurement  same measurement and apparatus
is used with a particle and antiparticle
Gabrielse
Most Stringent Tests of the Standard Model
(and Gravity) with Antiprotons
Q/M of Antiproton and Proton – most stringent test of the
Standard Model’s CPT theorem
with baryons
Comparison of Antiproton and Proton Gravity
680 Times Improved Comparision of the Antiproton and Proton
Magnetic Moments
Gabrielse
Embarrassing, Unsolved Mystery:
How did our Matter Universe
Survive Cooling After the Big Bang?
Big bang  equal amounts of matter and antimatter
created during hot time
As universe cools  antimatter and matter annihilate
Big Questions:
• How did any matter survive?
• How is it that we exist?
Our experiments are looking for evidence of any way that
antiparticles and particles may differ
Gabrielse
Our “Explanations” are
Not so Satisfactory
Baryon-Antibaryon Asymmetry in Universe is Not Understood
Standard “Explanation”
• CP violation
• Violation of baryon number
• Thermodynamic non-equilibrium
Alternate
• CPT violation
• Violation of baryon number
• Thermo. equilib.
Bertolami, Colladay, Kostelecky, Potting
Phys. Lett. B 395, 178 (1997)
Why did a universe made of matter survive the big bang?
Makes sense look for answers to such fundamental questions
in the few places that we can hope to do so very precisely.
Bigger problem: don’t understand dark energy
within 120 orders of magnitude
_
_
Gabrielse
Why Compare H and H (or P and P)?
Reality is Invariant – symmetry transformations
P
parity
CP
charge conjugation, parity
CPT charge conjugation, parity, and time reversal
CPT Symmetry
 Particles and antiparticles have
• same mass
• same magnetic moment
• opposite charge
• same mean life
 Atom and anti-atom have
 same structure
Looking for Surprises
• simple systems
• extremely high accuracy
• comparisons will be convincing
• reasonable effort
• FUN
Gabrielse
Comparing the CPT Tests
3 fundamentally different types of particles
Warning – without CPT violation models it is hard to compare
CPT Test Measurement
Accuracy
Accuracy
Free
Gift
_
K0 K0 2 x 10-18
Mesons
2 x 10-3
1015
e+ e2 x 10-12
Leptons
2 x 10-9
103
improve with
antihydrogen
_
PP
9 x 10-11
baryons
9 x 10-11
1
Gabrielse
I Came to CERN First in 1986
to Compare the Antiproton and the Proton
 Started cold antiproton and antihydrogen physics
 Now a dedicated storage ring and 6 international collaboration
(still amazes me)
Gabrielse
Accumulating Low Energy Antiprotons:
Basic Ideas and Demonstrations (1986 – 2000)
TRAP Collaboration
at CERN’s LEAR
1 cm
magnetic
field
21 MeV
antiprotons
_
• Slow antiprotons in matter
• Capture antiprotons in flight
• Electron cooling  4.2 K
• 5 x 10-17 Torr
+
_
10-10
energy
reduction
Now used by 5 collaborations
at the CERN AD
ATRAP, ALPHA, ASACUSA,
AEGIS, BASE
Gabrielse
Highest Precision Test of Baryon CPT Invariance
 by TRAP at CERN
q / m (antiproton)
 0.99999999991(9)
q / m (proton)
91011  90ppt
(most precise result of CERN’s antiproton program)
Goal at the AD: Make CPT test that approach
exceed this precision
Gabrielse
We Improved the Comparison of Antiproton and
q / m (antiproton)
6
 0.99999999991(9)
Proton by ~10
q / m (proton)
9 1011  90 ppt
most stringent CPT test with baryons
6  105
100
antiprotons
and protons
G. Gabrielse, A. Khabbaz, D.S. Hall, C. Heimann, H. Kalinowsky, W. Jhe;
Phys. Rev. Lett. 82, 3198 (1999).
Gabrielse
Seek to Improve Lepton and Baryon CPT Tests
antiproton
moment
ATRAP members

R [H] m[e ]

R [H] m[e  ]
2
2
 q[e ]   q[ p ]  1  m[e  ] / M [ p ]
 q[e  ]   q[ p ]  1  m[e  ] / M [ p ]


 

Gabrielse
Gabrielse
Direct Comparison of
Antimatter and Matter Gravity
Does antimatter and matter accelerate at the same rate
in a gravitational field?
g antimatter   g matter
acceleration due to gravity
for antimatter
acceleration due to gravity
for matter
Gabrielse
The Most Precise Experimental Answer is “Yes”
 to at lease a precision of 1 part per million
 /   g h / c 2
Gravitational red shift for a clock:
 Antimatter and matter clocks run at different rates
if g is different for antimatter and matter
c
U
 3(  1) 2
c
c
for tensor gravity
(would be 1 for scalar gravity)
Hughes and Holzscheiter,
Phys. Rev. Lett. 66, 854 (1991).
grav. pot. rnergy difference
between empty flat space time
and inside of hypercluster of galaxies
Experiment: TRAP Collaboration, Phys. Rev. Lett. 82, 3198 (1999).
c
c
 10
10
 
6
  1  ( 10 )
Gabrielse
Gravity and Antihydrogen
Gabrielse
May be Hard to Get the Part per Million Precision
of the Redshift Limit
with Antihydrogen and Hydrogen
g antimatter   g matter
Gravitational redshift:
c
c
 10
10
 
6
  1  ( 10 )
Worthy goal for AEGIS and GBAR  can they get a part per million
ALPHA trapped antihydrogen released (2013):
  110
(108 times less precise)
Gabrielse
Sometimes It is Said
that this Redshift Measurement is not so Valid
Because it “Assumes CPT Invariance”
• Does not assume CPT invariances in the gravity sector of course
• Only assumes that CPT violations in the Standard Model (if they exist)
do not cancel the CPT violations in gravity (if they exist)
• Does not seem likely to me that CPT violations in the Standard Model
would be just the right size to cancel differences in gravitational
redshifts of the antiproton and proton (at our location in space-time).
Gabrielse
Antiproton Magnetic Moment
Gabrielse
Proton and Antiproton Magnetic Moments
are Much Smaller than the Electron Moment
Harder: nuclear magneton rather than Bohr magneton
Gabrielse
Phys. Rev. Lett. 180, 153001 (2012)
Earlier contributions
Later measurement with similar methods
Gabrielse
Gabrielse
Resonance Lines
to Determine the “Two” Frequencies
square
of extra
width
Brown-Gabrielse
Invariance Theorem
Gabrielse
First One-Particle Measurement of the
Antiproton Magnetic moment
680
times
lower
than
previous
Gabrielse
680 – Fold Improved Precision
ASACUSA
680
2013
plausible
aspiration
ATRAP, Phys. Rev. Lett. (2013).
Gabrielse
Proton Spin Flip Report
Similar proton result from Mainz group in same issue
Gabrielse
Gabrielse
Antihydrogen Hope for the Future
Note: no scientifically interesting tests of fundamental symmetries
have yet taken place with antihydrogen – beware the hype
Gabrielse
Proposal to Trap Cold Antihydrogen – 1986
• Produce cold antihydrogen from cold antiprotons
“When antihydrogen is formed in an ion trap, the neutral atoms will no longer be
confined and will thus quickly strike the trap electrodes. Resulting annihilations of
the positron and antiproton could be monitored. ..."
• Trap cold antihydrogen
• Use accurate laser spectroscopy to compare
antihydrogen and hydrogen
“For me, the most attractive way ... would be to capture the antihydrogen in a
neutral particle trap ... The objective would be to then study the properties of a small
number of [antihydrogen] atoms confined in the neutral trap for a long time.”
Gerald Gabrielse, 1986 Erice Lecture (shortly after first pbar trapping)
In Fundamental Symmetries, (P.Bloch, P. Paulopoulos, and
R. Klapisch, Eds.) p. 59, Plenum, New York (1987).
Use trapped antihydrogen
to measure antimatter gravity
Gabrielse
Most Trapped Antihydrogen in Its Ground State
5 +/- 1 ground state atoms
simultaneously trapped
ATRAP, “Trapped Antihydrogen in
Its Ground State”, Phys. Rev. Lett.
108, 113002 (2012)
Gabrielse
ATRAP Collaboration
Gabrielse
Ultimate Goal: Hydrogen 1s – 2s Spectroscopy
(or similar tests of ground state hyperfine structure)
(Haensch, et al., Max Planck Soc., Garching)
http://www.mpq.mpg.de/~haensch/hydrogen/h.html
Many fewer antihydrogen atoms will be available
Gabrielse
Two Methods Produce Slow Antihydrogen
1. In a nested Penning trap, during positron cooling of antiprotons
Device and technique – ATRAP
Used to produce slow antihydrogen – ATHENA and ATRAP
Variations: Basic (ATRAP initially, ATHENA-ALPHA)
Driven (ATRAP before 2007)
Adiabatic well depth change (ATRAP 2007)
2. Laser-controlled resonant charge exchange
ATRAP
Anti-H Method 1: Nested Penning Trap Gabrielse
3-Body “Recombination”
Nested Penning Trap
3-Body “Recombination”
Positron Cooling of Antiprotons
in a Nested Penning Trap
Gabrielse
p
e+
TRAP/ATRAP Develops the Nested Penning Trap
Proposed nested trap as a way to make antihydrogen
"Antihydrogen Production Using Trapped Plasmas"
G. Gabrielse, L. Haarsma, S. Rolston and W. Kells
Physics Letters A 129, 38 (1988)
"Electron-Cooling of Protons in a Nested Penning Trap"
D.S. Hall, G. Gabrielse
Phys. Rev. Lett. 77, 1962 (1996)
"First Positron Cooling of Antiprotons"
ATRAP
Phys. Lett. B 507, 1 (2001)
Gabrielse
Anti-H Method II: Antihydrogen Via Laser-Controlled
Resonant Charge Exchange
852 nm
510.6 nm
ATRAP, Phys. Rev. Lett. 93, 263401 (2004)
1986
Gabrielse
2012
1 Collaboration  4 Collaborations
Following the 1986 plan:
Variations
cold antiprotons
cold antihydrogen
trap antihydrogen
colder antihydrogen
extract from trap
precise laser spectroscopy
laser spectroscopy
interferometry
ATRAP and ALPHA
ASACUSA
AEGIS
Gabrielse
Gabrielse
First Generation Penning-Ioffe Apparatus
Gabrielse
ATRAP – observed the production of antihydrogen atoms
in the fields of a Ioffe trap (PRL 2008)
Less than 20 atoms were being trapped per trial
ALPHA – did similar production the following year
two directions
ATRAP
Try to make more atoms
5 +/- 1 per trial
ALPHA
Try to detect fewer atoms
0.7 +/- 0.3 per trial
Gabrielse
1.2 K Electrodes and Millions of Antiprotons
1.2 K Using
Pumped Helium
Gabrielse
ATRAP  More Antiprotons, Much Colder,
More Simultaneously Trapped Atoms
• Lowered electrode temperature to 1.2 K
• Started measuring antiproton temperatures
• Developed new pbar cooling methods
First antiprotons cold enough to centrifugally separate from the
electrons that cool them
Phys. Rev. Lett. 105, 213002 (2010).
Two new cooling methods for antiprotons
-- embedded electron cooling
-- adiabatic cooling
Phys. Rev. Lett. 106, 073002 (2011).
 3 million antiprotons at 3.5 K
Gabrielse
Gabrielse
Particle Physics at Low Energy
Gerald Gabrielse
Leverett Professor of Physics, Harvard University
Spokesperson of the CERN ATRAP Collaboration
Testing the Most Precise Prediction of the Standard Model
 Electron magnetic moment
Testing standard model extensions
 Electron electric dipole moment
Testing the Symmetries of the Standard Model
 Q/M for the antiproton and proton
 Antiproton and proton magnetic moments
 Positron and electron magnetic moments (underway)
 Antihydrogen and hydrogen structure (still in far future)
Comparing Antimatter and Mater Gravity
 Gravitational Redshift of the Antiproton and Proton
Supported by US NSF and AFOSR
Gabrielse
Summary
Low energy particle physics produces the most stringent tests
of the standard model, its extensions and its fundamental symmetries
- electron magnetic dipole moment
- electron electric dipole moment
- comparison of antiproton and proton charge-to-mass ratios
- comparison of antiproton and proton gravity
- comparison of antiproton and proton magnetic moments
Antihydrogen – now have cold trapped antihydrogen atoms in their
ground states, but not enough atoms yet
– no interesting tests of fundamental symmetries yet,
but big hopes for the future