IIT physics colloquium - Illinois Institute of Technology

Transcription

Antimatter Gravity
MICE-U.S. Plans
with Muons?
Daniel M. Kaplan
US Spokesperson, MICE Collaboration
Dan Kaplan
Physics Colloquium
IIT Review
MuTAC
Fermilab
29 August
2013
16–17 March, 2006
Outline
• Dramatis Personae
• A Bit of History
-
antimatter, the baryon asymmetry of the
universe, and all that...
• The Ideas, The Issues, The Opportunities
• Required R&D
• Conclusions
Our story’s a bit complicated, so please bear with me!
...and stop me if you have a question!
D.#M.#Kaplan,#IIT
IIT#Physics#Colloquium######8/29/13
2 /43
Matter & Energy
Dramatis Personae
• After many decades of experimentation with subatomic particles, we now
know what everything is made of...
Baryons & antibaryons :
p = uud & p = uud
Λ = uds & Λ = uds
...
Mesons :
K 0 = ds & K 0 = ds
B0 = db & B 0 = db
B+ = ub & B− = ub
...
Leptons : e∓, µ∓, τ∓, ν’s
D.#M.#Kaplan,#IIT
3 /43
Matter & Energy
Dramatis Personae
“Imperfect mirror”
• After many decades of experimentation with subatomic particles, we now
know what everything is made of...
Baryons & antibaryons :
Anti
Anti
p = uud & p = uud
Λ = uds & Λ = uds
...
Mesons :
Anti
K 0 = ds & K 0 = ds
B0 = db & B 0 = db
B+ = ub & B− = ub
...
∓, ν’s
Leptons : e∓, µ∓, τAntimatte
• And, don’t forget: antimatter and matter
annihilate on contact
D.#M.#Kaplan,#IIT
3 /43
Outline
-
• Muonium Gravity Experiment
• Required R&D
• Conclusions
D.#M.#Kaplan,#IIT
4 /43
Outline
➡ • A Bit of History
-
• Required R&D
• Conclusions
D.#M.#Kaplan,#IIT
4 /43
Our story begins with...
D.#M.#Kaplan,#IIT
5 /43
Antimatter!
[photo credits:
Nobelprize.org]
• Introduced by Dirac in 1928
-
Dirac equation (QM + relativity)
described positrons in addition to electrons
-
positron discovered by Anderson in 1932
-
now well established that
Paul A. M. Dirac
Carl Anderson
antiproton discovered by Chamberlain & Segrè
in 1955
o all charged particles (and many types of neutrals)
Owen Chamberlain
have antiparticles, of opposite electric charge
o Big Bang produced exactly equal amounts of matter
and antimatter
D.#M.#Kaplan,#IIT
Emilio Segrè
6 /43
Baryon Asymmetry
and antimatter – a puzzle!
• Already in 1956, M. Goldhaber noted the baryon
asymmetry of the universe (BAU)
[M. Goldhaber, “Speculations on Cosmogeny,”
Science 124 (1956) 218]
-
universe seems to contain lots of mass in the form of
baryons – protons and neutrons – but almost no
antimatter! How could this be consistent with the BB?
-
now generally believed BAU arose through CP violation
(discovered in 1964)
-
but, pre-1964, more plausible to postulate gravitational
repulsion between matter and antimatter – “antigravity”!
D.#M.#Kaplan,#IIT
7 /43
Am. J. Phys. 26 (1958) 358
.
.
.
[...]
[...]
[...]
• Note: Eqivalence Principle is fundamental to
General Relativity
‣
if it doesn’t apply to antimatter, at the very least, our
understanding of GR must be modified
D.#M.#Kaplan,#IIT
8 /43
Baryon Asymmetry
and antimatter – a puzzle!
• Already in 1956, M. Goldhaber noted the baryon
asymmetry of the universe (BAU)
[M. Goldhaber, “Speculations on Cosmogeny,”
Science 124 (1956) 218]
-
universe seems to contain lots of mass in the form of
baryons – protons and neutrons – but almost no
antimatter! How could this be consistent with the BB?
-
-
but, pre-1964, more plausible to postulate gravitational
repulsion between matter and antimatter – “antigravity”!
D.#M.#Kaplan,#IIT
9 /43
The Nobel P
Baryon Asymmetry
The Nobel Prize in Physics 1980
-
The Nobel Prize in Phy
James Cronin, Val Fitch
• But – where’s the needed CP violation?
-
CPV discovery [Cronin, Fitch, et al., PRL 13 (1964) 138]:
~10–3 asymmetry in decays of K0 vs K̄0 meson
‣
-
James Watson Cronin
allows distinguishing matter from antimatter
in an absolute sense (“annihilating an alien”)
James Watson Cronin
[photo credits:
Nobelprize.org]
the discovery of violations of
Photos: Copyright © The Nobel Fou
but too weak by orders of magnitude to
account for observed ~1-in-108 BAU
‣
Val Logsdon Fitch
To cite this page
MLA style: "The Nobel Prize in Phys
/nobel_prizes/physics/laureates/198
more CP violation to be discovered??
•
Val Logsdon Fitch
The Nobel Prize in Physics 1980 was awarded jointly to
hot particle-physics topic (LHCb/Belle/LBNE...)
– but, so far, no experimental evidence for it
D.#M.#Kaplan,#IIT
the discovery of 1violations
of fundamental symmetry pr
of 2
Photos: Copyright © The Nobel Foundation
To cite this page
10 /43
MLA style: "The Nobel Prize in Physics 1980". Nobelprize.org. Nobel
/nobel_prizes/physics/laureates/1980/>
CPV and Alien
Annihilation
• Imagine you’re an alien from another galaxy
approaching Earth in a spaceship.
• Is it safe to land or will you be annihilated on
contact???
• Just radio Earth and ask:
the decay of the long-lived neutral kaon, is
‣ “In
the more common lepton matter or antimatter?”
‣ If you agree with their answer, it’s safe to land!
D.#M.#Kaplan,#IIT
11 /43
The Nobel P
Baryon Asymmetry
-
The Nobel Prize in Phy
James Cronin, Val Fitch
• But – where’s the needed CP violation?
-
CPV discovery [Cronin, Fitch, et al., PRL 13 (1964) 138]:
~10–3 asymmetry in decays of K0 vs K̄0 meson
‣
-
James Watson Cronin
allows distinguishing matter from antimatter
in an absolute sense (“annihilating an alien”)
James Watson Cronin
[photo credits:
Nobelprize.org]
but too weak by orders of magnitude to
account for observed ~1-in-108 BAU!
‣
Val Logsdon Fitch
the discovery of violations of
Photos: Copyright © The Nobel Fou
To cite this page
MLA style: "The Nobel Prize in Phys
/nobel_prizes/physics/laureates/198
more CP violation to be discovered??
Val Logsdon Fitch
hot particle-physics topic (LHCb/Belle/LBNE...)
– but, so far, no experimental evidence for it
The Nobel Prize in Physics 1980 was awarded jointly to
the discovery of 1violations
of fundamental symmetry pr
of 2
Photos: Copyright © The Nobel Foundation
LHCb
D.#M.#Kaplan,#IIT
To cite this page
12 /43
MLA style: "The Nobel Prize in Physics 1980". Nobelprize.org. Nobel
/nobel_prizes/physics/laureates/1980/>
But there’s more...
D.#M.#Kaplan,#IIT
13 /43
Outline
-
➡•
The Ideas, The Issues, The Opportunities
• Required R&D
• Conclusions
D.#M.#Kaplan,#IIT
14 /43
Three Cosmological Puzzles
1. Baryon asymmetry
‣
as we’ve seen, believed to be due to CPV, but
insufficient CPV seen experimentally to support this
Dark
Matter?
2. Expansion of universe
appears
to be accelerating
‣
Evidence
for Dark
comes from
believed
to beMatter
due to “dark
energy,”http://www.astro.umd.edu/~ssm/mond/fit_compare.html
comprising 70%
motion
large
scales:
not enough
gravity
of at
total
– but
no direct
observational
as to its nature or existence
fromevidence
visible matter.
http://astroweb.case.edu/ssm/mond/
fit_compare.html
3. Galactic rotation curves
‣
suggest existence of large amounts of
“dark matter” (5
x normal matter)
NASA
– but dark matter particles have yet to be found
Alternative is to modify gravity:
Might there be a simpler explanation???
D.#M.#Kaplan,#IIT Newtonian
Modified
Dynamics (MOND).
15 /43
Antigravity?
• What if matter and antimatter repel gravitationally?
-
leads to universe with separated matter and antimatter
regions, and makes gravitational dipoles possible
BAU is local, not global
for new sources of CPV
-
no need
repulsion changes the expansion rate of the universe
possible explanation for apparent
acceleration – without dark energy
-
[A. Benoit-Lévy and G. Chardin, “Introducing the
Dirac-Milne universe,” Astron. & Astrophys. 537 (2012)
A78]
[D. Hajdukovic, “Quantum vacuum and virtual
gravitational dipoles: the solution to the dark energy
problem?,” Astrophys. Space Sci. 339 (2012) 1]
virtual gravitational dipoles can modify gravity at long
distances
possible explanation for rotation
curves – without dark matter
D.#M.#Kaplan,#IIT
[L. Blanchet, “Gravitational polarization and the
phenomenology of MOND,” Class. Quant. Grav. 24,
3529 (2007);
L. Blanchet & A.L. Tiec, “Model of dark matter and dark
energy based on gravitational polarization,” PRD 78,
024031 (2008)]
16 /43
Studying Antimatter Gravity
D.#M.#Kaplan,#IIT
17 /43
Whitteborn & Fairbanks Expt
to address the question!
• First attemptWhitteborn
& Fairbanks Expt
intended to
• Famous experiment,
Famous experiment attempted
[F. C. Witteborn & W. M. Fairbank,
“Experimental Comparison of the
Gravitational Force on Freely
Falling Electrons and Metallic
Electrons,” Phys. Rev. Lett.
19,1049 (1967)]
measure gravitational force on positrons
•
•
to measure gravitational force
Started with
in copper drift
onelectrons
positrons.
tube; measured
maximum
timedrift
of flight
➢electrons
in copper
tube
➢measured
Managed only
to set anmaximum
upper TOF
limit:
Only mg
managed
to setlevitation?
a limit on
F < 0.09
electrical
electrons: F < 0.09mg
difficulty of a (never published)
• Indicated Never
published (made?)
measurement with positrons
measurement with positrons
PRL 19,1049 (1967)
D.#M.#Kaplan,#IIT
Friday, October 26, 2012
17 /43
Thomas Phillips
25
Next Attempt
• Los Alamos-led team proposed (1986) to measure
gravitational force on antiprotons at the CERN Low
Energy Antiproton Ring (LEAR)
• Similar approach to Witteborn & Fairbank, but with
2000x greater m/q ratio
• Project ended inconclusively
‣ Generally taken as evidence that gravitational
measurements on charged antimatter are hopeless
➡ need to work with neutral antimatter
D.#M.#Kaplan,#IIT
18 /43
• Experimentally, still unknown even whether
g = 0 or ε
antimatter falls up or down! Or whether g – —
-
in principle a simple interferometric measurement
with slow antihydrogen beam [T. Phillips, Hyp. Int. 109 (1997) 357]:
Mask
grating
de Broglie
waves
interfere
H̅
!"=#
v ~ 103 m/s
e+
p
—
-
~1m
~1m
if —g = – g, antigravity as discussed above
Thomas Phillips
Duke University
Time-of-Flight Detector
raft
½ gt2 = 5 µm
e, ciple
s
a
c Prin
r
e
ith ence ified!
e
d
In ival
o
m
Equ st be
mu
5
if g = g ± ε, need to modify theory of gravity (scalar
+
vector + tensor), or add “5th force” to the known 4
—
D.#M.#Kaplan,#IIT
19 /43
• But that’s not how anybody’s doing it!
D.#M.#Kaplan,#IIT
20 /43
NATURE PHYSICS DOI: 10.1038/NPHYS2025
NATURE PHYSICS DOI: 10.1038/NPHYS2025
• World leader: ALPHA* at
a
e+
CERN Antiproton Decelerator
e+
_
p
They make antihydrogen from p and e+ in a
AntihydrogenPenning
and mirror-trapped
antiproton
3
trap
anddiscrimination
trap it with an octupole
winding,
zˆ
xˆ
b
60
e
0
¬60
¬200
¬200
¬100
¬100
0
z (mm)
•
"
#
B (T)
B (T)
0
z (mm) 100
100
200
200
2
1
¬
2
2
1
1
¬200
¬100
0
z (mm) 100
FT
!
*+&&'&,-'+")
3
[G. B. Andresen et al., “Confinement of antihydrogen
for 1,000 seconds,” Nature Phys. 7 (2011) 558]
c
c
¬
0
¬60
!"#$%&'(#)
e
60
y (mm)
122+3+"4%+'2
5#%#$%'&
¬40
3-layer Si detector
b
y (mm)
.$%/0'"#
_
p
3-layer Si detector
B (T)
•
yˆ
ˆ
z—
yˆ
xˆ
Aarhus Univ, Simon Fraser Univ, Berkeley, Swansea
Electrodes
d
Mirror coils
Univ, CERN,
Univ Federal do Rio de Janeiro, Univ of40
Vacuum wall
Calgary, TRIUMF, Electrodes
Univ of British Columbia, Univ of
Tokyo, Stockholm Univ, YorkVacuum
Univ, wall
UnivCryostat
of Liverpool,
wall
Univ of Victoria, Auburn Univ, NRCN-Nuclear
Research Center Negev, RIKENCryostat wall
0
y (mm)
a
* Antihydrogen Laser Physics Apparatus
d
Mirror coils
¬200
¬100
0
z (mm)
100
200
200
Figure 1 | The ALPHA antihydrogen trap and its magnetic-field configuration. a, A schematic view
Figureantihydrogen
1 | The ALPHA
antihydrogen
trap
its magnetic-field
configuration.
A schematic
view
of the A
atoms
is provided
by and
an octupole
magnet (not
shown) anda,mirror
magnets,
respective
Figure 1. Figure
A schematic,
cut-away
diagram ofof
theALPHA
antihydrogen
production
and
1: (left)
3D schematic
trap
[7];
(right)
on-axis
magnetic
field
vs
z
[5].
antihydrogen
atoms
is
provided
by
an
octupole
magnet
(not
shown)
and
mirror
magnets,
respectively.
inner diameter
of 44.5positions
mm. A three-layer
the c
trapping region of the ALPHA apparatus,anshowing
the relative
of the silicon vertex detector surrounds the magnets andPenni
an
inner
diameter
of
44.5
mm.
A
three-layer
silicon
vertex
detector
surrounds
the
magnets
and
the
cryostat
solenoid
(not
shown).
An
antiproton
beam
is
introduced
from
the
right,
whereas
positrons
from
an a
cryogenically cooled Penning-Malmberg trap electrodes, the minimum-B trap
solenoid
(not
shown).
An
beam
is introduced
from
the right,
whereas
positrons
from an
accumula
magnetic-field
in the
y–z
plane
(z
along
the trap
axis,
with
z =application
0
at the centre
magn
magnets and the annihilation detector.
The
trap
wallstrength
is antiproton
on the
inner
radius
[C.
Amole
et isal.,
“Description
and
first
of of the
magnetic-field
y–zinner
plane
(z isinof
along
the
trap axis,c,with
zaxial
= 0 field
at theprofile,
centrewith
of the
magnetic
trap
of the electrodes. Not shown is the solenoid,
which
makesinathe
field
ẑ.
depict
thestrength
locations
ofuniform
the
walls
the
electrodes.
The
an
effective
tra
a new technique to measure the gravitational mass
The components are not drawn to scale.
depictplane.
the locations
of the inner walls
of the
electrodes.
c, The axial field profile, with an effective trap length
e, The field-strength
profile
along
the x axis.
of antihydrogen,”
Nature Comm. 4 (2013) 1785]
plane. e, The field-strength profile along the x axis.
then shut off the magnet currents & see
whether more H̅ annihilate
on the top or on the bottom
D.#M.#Kaplan,#IIT
1. Introduction
efficient injection of antiprotons into the positrons with
very to our previous
21 /43
16
efficient
injection
of
antiprotons
into
the
positrons
with
very
to ouralso
previous
work
low kinetic energies.
provides
sens
low kinetic
energies.
also provides
sensitivity
About
6 ⇥ 103 antihydrogen atoms are produced by enabling
as we shall
show.
the equivalence principle. As can be seen in Fig. 2, there is a
tendency for the anti-atoms to annihilate in the bottom half
(yo0) of the trap. This tendency is pronounced for anti-atoms
annihilating at later times. This is because, as shown in Fig. 3 and
in Table 1, the confining potential well associated with the
magnetic and gravitational forces in equation 1 is most skewed by
inert.
-65 ≤ F ≤ 110 @ 90% C.L.
[ALPHA Collaboration, 2013]
• They propose improving
sensitivity to ∆F ~ 0.5
• May take 5 years...?
D.#M.#Kaplan,#IIT
– – data avg
10
0
−10
F=100
grav.
– sim avg
20
Annihilation y (mm)
• The first published limit:
• Let F = m /m of H̅
• Then
• simulation o data
Mo
Fig
qu
giv
yi
of
pse
−20
0
5
10
15
Time (ms)
20
25
30
Figure 2 | Annihilation locations. The times and vertical (y) annihilation
locations (green dots) of 10,000 simulated antihydrogen atoms in the
decaying magnetic fields, as found by simulations of equation 1 with
F ¼ 100. Because F ¼ 100 in this simulation, there is a tendency for the antiatoms to annihilate in the bottom half (yo0) of the trap, as shown by the
black solid line, which plots the average annihilation locations binned in
1 ms intervals. The average was taken by simulating approximately
900,000 anti-atoms; the green points are the annihilation locations of a
sub-sample of these simulated anti-atoms. The blue dotted line includes the
effects of detector azimuthal smearing on the average; the smearing
reduces the effect of gravity observed in the data. The red circles are the
annihilation times and locations for 434 real anti-atoms, as measured by
our particle detector. Also shown (black dashed line) is the average
annihilation location for B840,000 simulated anti-atoms for F ¼ 1.
Fig
tim
res
dep
NATURE COMMUNICATIONS | 4:1785 | DOI: 10.1038/ncomms2787 | www.nature.com/natureco
[C. Amole et al., “Description and first
application of
& 2013 Macmillan Publishers Lim
a new technique to measure the gravitational mass
of antihydrogen,” Nature Comm. 4 (2013) 1785]
22 /43
• How else might it be done?
H̅ efforts in progress at CERN AD
• Many
(ALPHA, ATRAP, ASACUSA, AEgIS, GBAR)
•
•
-
too various to describe here...
All require antiprotons, so possible only at AD
BUT – another approach may also be feasible...
D.#M.#Kaplan,#IIT
23 /43
• Besides antihydrogen, only one other antimatter
system conceivably amenable to gravitational
measurement:
• Muonium (M or Mu) –
hydrogenic atom with a positive (anti)muon
‣ areplacing
the proton
(an object of study for more than 50 years)
• Measuring muonium gravity – if feasible – would
be the first gravitational measurement of a lepton,
and of a 2nd-generation particle
D.#M.#Kaplan,#IIT
24 /43
Muonium
• Much is known about muonium...
-
a purely leptonic atom,
discovered in 1960
[V. W. Hughes et al., “Formation of Muonium and Observation
of its Larmor Precession,” Phys. Rev. Lett. 5, 63 (1960)]
τM = τµ = 2.2 µs
-
February 4, 2008
14:21
Proceedings Trim Size: 9in x 6in
hughes˙mem˙KJ˙mu
2
readily produced when µ+ stop in matter
2
2 P3/2
2
2 S1/2
chemically, almost identical to hydrogen
F=1
558 MHz
10922 MHz
1047 MHz
F=0
atomic spectroscopy well studied
F=1
187 MHz
22P1/2
λ= 244nm
F=2
F=1
74 MHz
F=0
2 455 THz
λ= 244nm
forms certain compounds (MuCl, NaMu,...)
F=1
2
1 S1/2
4463 MHz
F=0
“ideal testbed” for QED, the search for new forces,
precision measurement of muon properties, etc.
Figure 1. Energy levels of the hydrogen-like muonium atom for states with pr
quantum numbers n=1 and n=2. The indicated transitions could be induced to d
microwave or laser spectroscopy. High accuracy has been achieved for the tran
which involve the ground state. The atoms can be produced most efficiently for n
D.#M.#Kaplan,#IIT
charge and spin carrying constituents inside the proton are not know
sufficient accuracy.
High energy scattering
have shown for leptons no stru
25experiments
/43
down to dimensions of 10−18 m. They may therefore be considered ”p
like”. As a consequence, complications as those arising from the stru
of the nucleus in natural atoms and such artificial systems that co
Outline
-
➡ • Muonium Gravity Experiment
• Required R&D
• Conclusions
D.#M.#Kaplan,#IIT
26 /43
Studying Muonium Gravity
arXiv:physics/0702143v1 [physics.atom-ph]
Testing Gravity with Muonium
K. Kirch∗
Paul Scherrer Institut (PSI), CH-5232 Villigen PSI, Switzerland
(Dated: February 2, 2008)
Recently a new technique for the production of muon (µ+ ) and muonium (µ+ e− ) beams of unprecedented brightness has been proposed. As one consequence and using a highly stable MachZehnder type interferometer, a measurement of the gravitational acceleration ḡ of muonium atoms
at the few percent level of precision appears feasible within 100 days of running time. The inertial
mass of muonium is dominated by the mass of the positively charged - antimatter - muon. The
measurement of ḡ would be the first test of the gravitational interaction of antimatter, of a purely
2
leptonic system, and of particles of the second generation.
x
ment, then there would be no telling what exPACS numbers:
sics could follow.”
L ~ 1.4 cm
onium experiment appears feasible now bewo recent inventions: (i) a new technique to
~ 43 mrad
compress a high acceleration
intensity beam of posΘ
ect and
gravitational
of antimatter has not
M atoms comes from the fact that the inertial ma
s, to reaccelerate the muons to 10 keV and fow<100 µm
measured
soof far.
experiment
with
antiprotons
the muon is some 207 times larger than the one o
nto
a beam spot
100 µmAn
diameter
or even
d~100 nm
and
a new
technique totherein)
efficiently convert
[1] (ii)
and
references
did not succeed because
electron, thus, muonium is almost completey, to 9
to M atoms in superfluid helium at or below
e extreme
difficulty
sufficiently
shield theInterferometer
interantimatter.
An interesting feature is that M atom
hich
they thermalize
and fromto
which
they get
Source
Detection
yn270
K perpendicular
the surface when they fields. For a simiregion
from toelectromagnetic
almost exclusively produced at thermal energies by
vacuum [15].
+M beam comes
1: Scheme of[2]
the experimental
setup: µ
the
eason,
results
of muon
measurements
withFIG.
electrons
are
ping
in matter which they often leave again as
ng an existing
surface
beam of highest
+
from the cryogenic µ beam target on the left hand side,
as
input,very
see e.g.
[16], D.#M.#Kaplan,#IIT
it should be
possible
ssed
controversial
and
the plan
M atom.
However, up to un
27 /43
enters to
and eventually
partially
traverses the malized,
interferometerhydrogen-like,
and reaches
an almost monochromatic beam of M atoms
the detection
on the right hand
side. The
dimensions
pare
with positrons was never realized.
Notregion
affected
cently,
a gravitational
experiment with muonium w
0.5/270) with a velocity of about 6300 m/s
are not to scale and the diffraction angle θ is in reality smaller
• Adaptation of Phillips’ interferometry idea
to an antiatom with a 2.2 µs lifetime!
ment, then there would be no telling what exsics could follow.”
onium experiment appears feasible now bewo recent inventions: (i) a new technique to
ct and compress a high intensity beam of poss, to reaccelerate the muons to 10 keV and fonto a beam spot of 100 µm diameter or even
and (ii) a new technique to efficiently convert
to M atoms in superfluid helium at or below
hich they thermalize and from which they get
y 270 K perpendicular to the surface when they
vacuum [15].
ng an existing surface muon beam of highest
as input, see e.g. [16], it should be possible
an almost monochromatic beam of M atoms
0.5/270) with a velocity of about 6300 m/s
ding to 270 K or a wavelength
λ ≈ 5.6Å) and
!
sional divergence of ∆E/E ≈ 43 mrad at a
ut 105 s−1 M atoms [15]. This is a many orders
ude brighter beam than available up to now.
g the approach of [5, 6, 8, 9] a Mach-Zehnder
erometer should be used in the muonium exThe principle with the source, the three gratrometer and the detection region is sketched
We assume here three identical gratings and
st two for setting up the interference pattern
D.#M.#Kaplan,#IIT
anned by moving the third grating. The setup
hort, because the decay length of the M atoms
v ~ 6300 m/s
L ~ 1.4 cm
x
2
~ 43 mrad
½ gt2 = 25 pm!
Θ
w<100 µm
d~100 nm
Source
Interferometer
Smaller than
an atom!
Detection
• “Same experiment” as Phillips proposed –
FIG. 1: Scheme of the experimental setup: the M beam comes
from the cryogenic µ+ beam target on the left hand side,
enters and partially traverses the interferometer and reaches
the detection region on the right hand side. The dimensions
are not to scale and the diffraction angle θ is in reality smaller
than the divergence.
only harder!
• How might it be done?
ferometer. The gravitational phase shift to be observed
is (using the notation of [9])
Φg =
2π
g τ 2 ≈ 0.003.
d
(3)
This is rather small but still an order of magnitude larger
than the phase
shift due to the acceleration induced
by the rotation of the earth (Sagnac effect: 4πτ 2 v/d ×
ωearth ≈ 3 × 10−4 ). Other accelerations of the system
28 /43
• Part of the challenge is the M production
method:
-
need monoenergetic M so as to have uniform flight
time
otherwise the interference patterns of different
atoms will have differing relative phases, and the
signal will be washed out
D.#M.#Kaplan,#IIT
29 /43
Monoenergetic Muonium?
• Proposal by D. Taqqu of Paul
Scherrer Institute (Switzerland):
[D. Taqqu, “Ultraslow Muonium for a Muon
beam of ultra high quality,” Phys. Procedia
17 (2011) 216]
-
stop slow muons in µm-thick layer of
superfluid He (SFHe)
-
chemical potential of hydrogen in SFHe will
eject M atoms at 6,300 m/s, perpendicular to
SFHe surface
o
makes ~ “monochromatic” beam (in the beamphysics jargon):
∆E/E ≈ 0.2%
D.#M.#Kaplan,#IIT
30 /43
ing another length L each, for distances of the s
the detector to the nearest interferometer grati
in 4 decay
Decay
and transmission lo
Figure' 1:' ' Principle! of! Mach! Zehnder! three2grating! atom! interferometer.!
! The! de!lenghts.
Broglie! waves! due!
to! each!
incident!atom!all!contribute!to!the!same!interference!pattern!over!a!range!of!incident!beam!angles!and!positions.!!
three
ratio
gratings reduces the init
Each! diffraction! grating! is! a! 50%! open! structure! with! a! slit! pitch!
of! 100!50%
nm.! ! The!open
assumed! grating!
separation!
−3
−1
corresponds!to!one!muon!lifetime.!
by
a
factor
2
×
10
,
yielding
N
=
200
s
de
0
!
Because only the indicated first order diffracti
!
the desired
Cryostat information but essentially all trans
1.4
“ship in apattern
bottle!”
are detected, theAinterference
has a red
cm
trast of somewhat below 4/9. Assuming a c
M detector
C = 0.3 and
using
eqn. (3) estimate
of [9] yields the
Sensitivity
sensitivity of the experiment:
Muonium Gravity Experiment
• One can then imagine the following apparatus:
@ 100 kHz:
SFHe
(Not to scale)
Incoming
surface-muon
beam
1
d 1
√
C N0 2π τ 2
!
≈ 0.3 g per #days
S =
!
• Well known property of SFHe to coat surface
Figure' 2:' ' Concept!sketch!of!muonium!interferometer!setup!(many!details!omitted).!!A!≈micron2thick!layer!of!
SFHe!(possibly!with!a!small!3He!admixture)!stops!the!muon!beam!and!forms!muonium!(M)!which!exits!vertically!
and!is!reflected!into!the!horizontal!off!of!the!thin!SFHe!film!coating!the!cryostat!interior.'
of its container
•
which means that the sign of ḡ is fixed after on
3% accuracy can be achieved after 100 days of
With the quite satisfactory statistics, the ne
tant issues are the alignment and stability of
!
45°
section of cryostat thus serves as
reflector to turn vertical M beam emerging
from SFHe surface into the horizontal
3
D.#M.#Kaplan,#IIT
31 /43
ing another length L each, for distances of the s
the detector to the nearest interferometer grati
in 4 decay
Decay
and transmission lo
Figure' 1:' ' Principle! of! Mach! Zehnder! three2grating! atom! interferometer.!
! The! de!lenghts.
Broglie! waves! due!
to! each!
three
ratio
gratings reduces the init
Each! diffraction! grating! is! a! 50%! open! structure! with! a! slit! pitch!
of! 100!50%
nm.! ! The!open
assumed! grating!
separation!
−3
−1
by
a
factor
2
×
10
,
yielding
N
=
200
s
de
0
!
Because only the indicated first order diffracti
!
the desired
Cryostat information but essentially all trans
1.4
“ship in apattern
bottle!”
are detected, theAinterference
has a red
cm
trast of somewhat below 4/9. Assuming a c
M detector
C = 0.3 and
using
eqn. (3) estimate
of [9] yields the
Sensitivity
sensitivity of the experiment:
• One can then imagine the following apparatus:
@ 100 kHz:
SFHe
(Not to scale)
Incoming
surface-muon
beam
1
d 1
√
C N0 2π τ 2
!
≈ 0.3 g per #days
S =
!
Figure' 2:' ' Concept!sketch!of!muonium!interferometer!setup!(many!details!omitted).!!A!≈micron2thick!layer!of!
SFHe!(possibly!with!a!small!3He!admixture)!stops!the!muon!beam!and!forms!muonium!(M)!which!exits!vertically!
!
D.#M.#Kaplan,#IIT
3
where
which means that
the sign of ḡ is fixed after on
3% accuracy canCbe
100 days of
= achieved
0.3 (est. after
contrast)
With the quiteNsatisfactory
statistics, the ne
0 = # of events
tant issues are the
and stability
d =alignment
100 nm (grating
pitch)of
τ = M lifetime
31 /43
•
Figure' 1:' ' Principle! of! Mach! Zehnder! three2grating! atom! interferometer.! ! The! de! Broglie! waves! due! to! each!
Each! diffraction! grating! is! a! 50%! open! structure! with! a! slit! pitch! of! 100! nm.! ! The! assumed! grating! separation!
!
Some
important questions:
!
Cryostat
1.4
cm
A “ship in a bottle!”
M detector
SFHe
Incoming
surface-muon
beam
(Not to scale)
!
Concept!sketch!of!muonium!interferometer!setup!(many!details!omitted).!!A!≈micron2thick!layer!of!
1. Figure'
Can2:' 'sufficiently
precise diffraction gratings be fabricated?
SFHe!(possibly!with!a!small! He!admixture)!stops!the!muon!beam!and!forms!muonium!(M)!which!exits!vertically!
3
2. Can interferometer and detector be aligned to a few pm
and stabilized against vibration?
3. !Can interferometer and detector
be operated at cryogenic
3
temperature?
4. How determine zero-degree line?
5. Does Taqqu’s scheme work?
D.#M.#Kaplan,#IIT
32 /43
Outline
-
➡ • Required R&D
• Conclusions
D.#M.#Kaplan,#IIT
33 /43
Answering the Questions:
1. Can sufficiently precise diffraction gratings be fabricated?
-
our collaborator, Derrick Mancini of the ANL Center for
Nanoscale Materials (CNM) thinks so – proposal submitted
to CNM to try it
2. Can interferometer and detector be aligned to a few pm
and stabilized against vibration?
-
needs R&D, but LIGO does much better than we need
3. Can interferometer and detector be operated at cryogenic
temperature?
-
needs R&D; work at IPN Orsay implies at least piezos OK
4. How determine zero-degree line?
-
use cotemporal x-ray beam (can M detector detect x-rays?)
5. Does Taqqu’s scheme work?
-
needs R&D; PSI working on it
D.#M.#Kaplan,#IIT
34 /43
Interferometer Alignment
• Could use 2 Michelson
interferometers per grating
-
!
!
laser
detector
Cryost
send laser beams in through cryostat lid
o
-
mirror
Figure' 1:' ' Principle! of! Mach! Zehnder! three2grating! atom! interferometer.! ! The
beam
incident!atom!all!contribute!to!the!same!interference!pattern!over!a!range!of!incid
splitter
Each! diffraction! grating! is! a! 50%! open! structure! with! a! slit! pitch! of! 100! nm.! ! T
photocorresponds!to!one!muon!lifetime.!
M/x-ray
detector
keeps instrumentation & heat external
to cryostat & M detection path open
SFHe
“natural” sensitivity ~ λ/2 ~ 300 nm; need ~ 3 pm (Not to scale)
10–5 enhancement
Incoming
surface-muon
beam
Figure' 2:' ' Concept!sketch!of!muonium!interferometer!setup!(many!details!omi
SFHe!(possibly!with!a!small!3He!admixture)!stops!the!muon!beam!and!forms!muo
and!is!reflected!into!the!horizontal!off!of!the!thin!SFHe!film!coating!the!cryostat!in
o
enhance by sitting at a zero of the intensity, using SAW
modulation, etc.
o
still lots of details to work out!
!
D.#M.#Kaplan,#IIT
3
35 /43
Additional Considerations
• What’s the optimal muonium pathlength?
-
say muonium interferometer baseline doubled:
costs e–2 = 1/7.4 in event rate, but gains x 4 in deflection
-
‣
a net win by 4 e–1 ≈ 1.5
tripling → x 1.2 improvement – diminishing returns
‣
but 9 x bigger signal
& stabilization
easier calibration, alignment,
• Need simulation study to identify optimum,
taking all effects into account
D.#M.#Kaplan,#IIT
36 /43
Additional Considerations
• Alternate solutions:
-
different M production scheme?
o
-
“monochromate” the beam by chopping?
laser interferometry instead of gratings?
D.#M.#Kaplan,#IIT
37 /43
Alternate Solutions
• Different M production scheme?
-
muonium production often employs SiO2
powder or silica aerogel
-
thermal energy spectrum, not monochromatic
can monochromate using choppers
drawbacks:
M
o
flux reduction
o
rotating shaft & bearings in vacuum
D.#M.#Kaplan,#IIT
38 /43
ments of local gravity [2], the gravity gradient [3], the
calculated to be !!& ¼ 8n2 ð@k2
Sagnac effect [4], Newton’s gravitational constant [5],
the sum of a recoil-induced term
the fine structure constant [6], and tests of fundamental
gravity-induced one, nkgTðT þ T
laws of physics [7–9]. Recent progress in increased moeration of free fall and & correspo
mentum transfer led to larger areas enclosed between the
interferometer, respectively (Fig.
interferometer arms [10–12] and, combined with commonBecause of Earth’s rotation, ho
mode noise rejection between simultaneous interferomedoes not close precisely. We adop
ters [13,14], to strongly increased sensitivity. With these
an inertial frame, one that does n
for a Viewpoint
in Physics
advances, what used toSelected
be a minuscule
systematic
effect
take the x axis horizontal
pointing
week ending
P
H
Y
S
I
C
A
L
R
E
V
I
E
W
L
E
T
T
E
R
S
2 MARCH
2012the
PRL 108, 090402 (2012)
now impacts interferometer performance: The Coriolis
south, and the z axis
such that
force caused by Earth’s rotation has long been known to
upwards, coincides with it at t1 , s
cause systematic effects [2]. In this Letter, we not only
and t4 , the laser is rotated relati
Influence
of
the
Coriolis
Force
in
Atom
Interferometry
demonstrate that it causes severe loss of contrast in large
changing the direction of the m
space-time
interferometers,
but also
use Haslinger,
a tip-tilt2 andresult,
wave
1
1,3 packet’s relativ
Pei-Chen
Kuan,1 Brian Estey,
Shau-Yu
Lan,1,*atom
Philipp
Holgerthe
Müller
mirror
[15] to ofcompensate
for it,ofimproving
contrastCalifornia
(by
intervals
1
Department
Physics, University
California, Berkeley,
94720, USA[t1 , t2 ], [t2 , t3 ], [t3 , t4 ],
2up to 350%), pulse separation time, and sensitivity, and
inAustria
"' ,
VCQ, Faculty of Physics, University of Vienna, Boltzmanngasse 5, A-1090order
Vienna,
3
characterize
the
configuration
space
wave packets.
In ad- California 94720, USA
Lawrence
Berkeley
National
Laboratory,
One Cyclotron
Road, Berkeley,
(Received
October 2011;
published
27 from
February
dition, we remove
the31systematic
shift
arising
the2012) v12 ¼ 2nvr ð0; 0; 1Þ;
v23 ¼
[16]. This leads
the largest
In a Sagnac
light-pulseeffect
atom interferometer,
we use to
a tip-tilt
mirror to space-time
remove the influence of the Coriolis force
v34 ¼ 2nvr ð"
þ T 0 Þ cos#
from Earth’s
rotation and
to characterize
configurationyet
space
wave packets. For interferometers
with' ð2T
a
area enclosed
in any
atom interferometer
demonstrated,
large momentum
and largetransfer
pulse separation
time,
we improve
given by transfer
a momentum
of 10@k,
where
@k is the
thecontrast by up to 350% and
suppress
systematic effects.
also reach
is to our
knowledgetime
the largest
momentum
of oneWe
photon,
andwhat
a pulse
separation
of space-time area enclosed
in any 250
atomms.
interferometer to date. We discuss implications for future high-performance instruments.
Figure 1 shows the atom’s trajectories
in our
apparatus.
DOI: 10.1103/PhysRevLett.108.090402
PACS
numbers:
03.75.Dg, 06.30.Gv, 37.25.+k, 67.85.!d
–9
We first consider the upper two paths: At a time t0 , an atom
of mass m in free fall is illuminated by a laser pulse of
wave
number k.useAtom-photon
interactions
coherently
a particular
output of the interferometer is given by
Light-pulse atom
interferometers
atom-photon intransfer
theguide,
momentum
of a number
of2photons
the !! is the phase difference accumuteractions to coherently
split,
and recombine
freely 2ncos
ð!!=2Þ, to
where
falling matter-waves
[1].with
Theyabout
are important
in measurelated
the matter
atom
50% probability,
placing
thebyatom
into awave between the two paths. It can be
ments of local D.#M.#Kaplan,#IIT
gravity
[2], superposition
the gravity gradient
[3],
the
calculated
be !!& ¼ 8n2 ð@k2 =2mÞT
& nkgTðT þ T 0 Þ,
coherent
of two
quantum
states
that to
separate
39 /43
Sagnac effect [4],with
Newton’s
gravitational
sum
of a isrecoil-induced
term 8n2 ð@k2 =2mÞT, and a
a relative
velocity constant
of 2nvr , [5],
where the
vr ¼
@k=m
the
FIG. 1 (color
online). Simultaneou
0
Alternate Solutions
• Atomic-beam laser interferometry: gravimetry
“gold standard”
-
technique good to ∆g/g ~ 10
timed laser pulses make superposition
of atomic hyperfine states, which interfere
the fine structure constant [6], and tests of fundamental
gravity-induced one, nkgTðT þ T Þ, where g is the accel-
Alternate Solutions
• Atomic-beam laser interferometry: gravimetry
“gold standard”
• Evaluating feasibility for muonium will take some
effort
-
many variables to consider, e.g.:
use ground-state muonium?
o
requires difficult “Lyman-alpha” VUV laser
o
likely impractical to get laser beams into cryostat without
windows
or n = 2 muonium?
o
what fraction are produced in that state?
D.#M.#Kaplan,#IIT
40 /43
R&D Status
• Still early days...
• Seeking funding,
students, and
collaborators
-
IIT-CAPP-13-6
arXiv:1308.0878 [physics.ins-det]
Measuring Antimatter Gravity with Muonium
Daniel M. Kaplan,* Derrick C. Mancini,† Thomas J. Phillips, Thomas J. Roberts,‡ Jeffrey Terry
Illinois Institute of Technology, Chicago, IL 60616, USA
Richard Gustafson
University of Michigan, Ann Arbor, MI!48109 USA
collaboration so far:
• Seeking venue at
Fermilab
-
e.g., proposed new
low-energy muon
beam at AP0
A0 Target & C
Dipoles for 300 MeV/c π’s
Klaus Kirch
Paul Scherrer Institute and ETH Zürich, Switzerland
M. Popovic presentation at NuFact 2013
ABSTRACT
300MeV/c pions!
We consider a measurement of the gravitational acceleration of antimatter, g̅ , using
muonium. A monoenergetic, low-velocity, horizontal muonium beam will be formed
from a surface-muon beam using a novel technique and directed at an atom
interferometer. The measurement requires a precision three-grating interferometer: the
first grating pair creates an interference pattern which is analyzed by scanning the third
3100MeV/c
for
grating vertically using piezo actuators. State-of-the-art nanofabrication
can pions
produce the
needed membrane grating structure in silicon nitride or ultrananoscrystalline diamond.
With 100 nm grating pitch, a 10% measurement of g̅ can be made using some months of
surface-muon beam time. This will be the first gravitational measurement of leptonic
matter, of 2nd-generation matter and, possibly, the first measurement of the gravitational
acceleration of antimatter.
g-2!
INTRODUCTION
D.#M.#Kaplan,#IIT
The gravitational acceleration of antimatter has never been directly measured.1 A measurement
could IIT#Physics#Colloquium######8/29/13
bear importantly on the formulation of a quantum theory41 /43
of gravity and on our
understanding of the early history and current configuration of the universe. It may be viewed as
a test of General
Relativity, or as a search for new, as-yet-unseen, forces, and is of great interest
5
R&D Status
• Still early days...
• Seeking funding,
students, and
collaborators
-
IIT-CAPP-13-6
arXiv:1308.0878 [physics.ins-det]
Measuring Antimatter Gravity with Muonium
Daniel M. Kaplan,* Derrick C. Mancini,† Thomas J. Phillips, Thomas J. Roberts,‡ Jeffrey Terry
Illinois Institute of Technology, Chicago, IL 60616, USA
Richard Gustafson
University of Michigan, Ann Arbor, MI!48109 USA
collaboration so far:
• Seeking venue at
Fermilab
-
e.g., proposed new
low-energy muon
beam at AP0
Paul Scherrer Institute and ETH Zürich, Switzerland
M. Popovic presentation at NuFact 2013
300MeV/c pions!
ABSTRACT
The Project
X Accelerator:
Concept and Capabilities
measurement of the gravitational acceleration of antimatter, g̅ ,
We consider a
using
muonium. A monoenergetic, low-velocity, horizontal muonium beam will be formed
from a surface-muon beam using a novel technique and directed at an atom
interferometer. The measurement requires a precision three-grating interferometer: the
first grating pair creates an interference pattern which is analyzed by scanning the third
3100MeV/c
for
grating vertically using piezo actuators. State-of-the-art nanofabrication
can pions
produce the
needed membrane grating structure in silicon nitride or ultrananoscrystalline diamond.
With 100 nm grating pitch, a 10% measurement of g̅ can be made using some months of
surface-muon beam time. This will be the first gravitational measurement of leptonic
matter, of 2nd-generation matter and, possibly, the first measurement of the gravitational
acceleration of antimatter.
ultimately, Project X
D.#M.#Kaplan,#IIT
A0 Target & C
Dipoles for 300 MeV/c π’s
Klaus Kirch
g-2!
Steve Holmes
DPF Community Summer Study
July 30, 2013
INTRODUCTION
The gravitational acceleration of antimatter has never been directly measured.1 A measurement
could IIT#Physics#Colloquium######8/29/13
bear importantly on the formulation of a quantum theory41 /43
of gravity and on our
understanding of the early history and current configuration of the universe. It may be viewed as
a test of General
Relativity, or as a search for new, as-yet-unseen, forces, and is of great interest
5
Conclusions
•
Antigravity hypothesis might neatly solve several
vexing problems in physics and cosmology
•
In principle, testable with antihydrogen or
muonium
-
if possible, both should be measured
➡First measurement of muonium gravity would be
a milestone!
•
But first we must determine feasibility
D.#M.#Kaplan,#IIT
42 /43
Final Remarks
• These measurements are an obligatory
homework assignment from Mother Nature!
•
Whether —
g = – g or not, if they are successfully
carried out, the results will certainly appear in
future textbooks.
D.#M.#Kaplan,#IIT
43 /43

IIT physics colloquium - Illinois Institute of Technology

Transcription

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