Int. Conference on Low Energy Antiproton Physics, Yokohama, Japan, March 3-7, 2003
Positron Storage Ring for Positronium and Antihydrogen
Generation in-flight. LEPTA Project.
G. Trubnikov, JINR, Dubna
Introduction: Why Ps is so interesting?
1. Ps is a simple quantum system - “Bohr atom in QED”
2. One can use Ps as a test particle for
several experiments of fundamental
character
3. There are some puzzles in Ps physics
from previous experiments (o-Ps life
time, for instance)
Introduction: Why Ps is so interesting?1. Electron cooling of positrons and Positronium generation2.Test of CPT theorem, CP and P conservation
2.1. e+ / e- charge difference => the first and foremost experiment
2.2. Rare and forbidden decay channels of o-Ps and p-Ps2.3. p-Ps => , search for circularly polarized photons
2.4. p-Ps => ~
3. QED test , P-violation (?)3.1. Positronium spectroscopy3.2. p-Ps life time3.3. o-Ps life time
4. Search for a light, neutral, short-lived boson5. Hypothesis of "Mirror Universe"6.Antihydrogen generation in-flight =>
=> CPT theorem test (future development)
e+ trap
Septum
Cooling section
Quadrupole
Collectore-gun
BDetector
e+ source
LEPTA scheme
General parameters of the LEPTACircumference, m 18.12Positron energy, keV 10.0Solenoid magnetic field, G 400Quad field gradient, G/cm 10.0Positron beam radius, cm 0.5Number of positrons 110
Residual gas pressure, Тоrr 110
Electron cooling systemCooling section length, m 4.53Beam current, A 0.5Beam radius, cm 1.0Electron density, cm-3 1.66108
Orthopositronium beam parametersIntensity, atom/sec 110
Angular spread, mrad 1Velocity spread 1104
Flux diameter at the ring exit, cm 1.1Decay length, m 8.52
2.Test of CPT theorem, CP and P conservation
The experiment scheme:
o-Ps
L
B
Bendingmagnet
Coordinatedetector
decay = 8.5 m at vo-Ps=6 m/s
Direct comparison of the e- and e+ electric charges.
The experiment concept : Detection of a displacement x of "neutral" atoms, when they travel in a transverse magnetic field B:
eee,pc2LB
ex2
The method resolution:
2o
L
x
eB
pc2
e
e
.If x~0.1 mm, BLm,
one can obtain e/e < 410-10
o-Ps
o-Ps
CsI
CsI
CsI
MCP AmplifierWedge and strip anode
Scheme of the detector based on MCP amplifier
Silicon & strips 75 mmScintillators
The scheme of the position sensitive silicon strip detector
o-Ps
Strip dimensions: 40 mm length, 25 or 40 mcm width, space between strips 69 or 54 mcm
2.2. The search for forbidden and rare decay channels of o-Ps and p-Ps
a) The forbidden and rare o-Ps annihilation channelso-Ps => 2n , n > 2, where n is an integer
annihilation probability Theory Experimento-Ps 2 0 < 1.4x10-3
o-Ps 4 < 10-27 < 0.8 x10-5
b) The forbidden and rare p-Ps annihilation channels
p-Ps => n , n > 2 ;
n = 3 - «forbidden» , n = 4 - «allowed»
annihilation probability Theory Experimentp-Ps 3 < 10-27 < 2.8x10-6
p-Ps 4 1.48x10-6 (1.50.07stat 0.09syst.)x10-6
The search for “forbidden” and rare o-Ps annihilation channels
o-Ps => 2n , n > 2, where n is an integer
o-PsCo-ordinate detector
???
The view in transverse plane
tgphoton = 1/
p-Ps
Magnet coilsMagnet yoke
p-Ps generation and decay in magnetic field The search for “forbidden” and rare p-Ps annihilation
channels p-Ps => n , n > 2
Co-ordinate -detector
??
??
The view in transverse plane
tgphoton = 1/
Co-ordinate -detector
p-Ps
Magnet coilsMagnet yoke
p-Ps generation and decay in magnetic fieldCPT violation search: p-Ps => , search for circularly polarized
photons with analysis by scattering in magnetized iron (iron = 14 mm for photons of 0.51 MeV energy)
??
??
B
BThe view in
transverse planetgphoton = 1/
e- e+
E1
M 1
PPs = (-1) x (+1) = -1
Pphotons = (-1)E1 x (+1)M1 = -1 if linear polarisation
Pphotons = (-1)(E1+M1) x (-1)(M1+E1) = +1
if circular polarisation Parity violation CPT violation !
3. QED test 3.1. Positronium spectroscopy =>
=> structure of Ps spectrum
a) Fine structure of the ground
state; o-Ps - p-Ps transitions in
magnetic field
b) Transition energy of different
statesc) Fine structure of excited states
d) e+e- charges and masses from
Ps spectrum
3.2. QED test: p-Ps life time
Theory Experimentp-Ps life time, ps 125.16(08) 125.142(27) [2x10-4]
A peculiarity: p-Ps decay length 3 cm
a) generation of p-Ps by the mixing of o-Ps and p-Ps states in magnetic field B 2 T and direct measurement of p-Ps =>
=> N(x) in a vacuum drift channel => / 310-5 if x 1 mkm (“the absorption
targets”);
b) indirect method: - mixing of o-Ps - p-Ps states in B 0.4 T and detection of decays in 2 (p-Ps) and 3 (o-Ps), analysis of No-Ps(x) in magnetic field
3.2. QED test: o-Ps life time
Theory Experimento-Ps life time, ns 142.038 141.880(32) [2x10-4]
142.150(80) [5x10-4]
The Experiment Resolution: N(x) = N(0)exp{-x / v }, ln N(x)/N(0) = - kx
Fitting with l.s.m gives us:L23
)0(N1
k k 0
Correspondingly, the value is measured with a precision of :
)0(N
1
v
v
)0(N
1
L2
v3
x
x
v
v
Thus, for / 110 –5 we need v / v ~ x / x 110 –5
N(0) ~ 1010 , Ntotal ~ nN(0)/ k0L ~ 0.6 nN(0) ~ 31010
It means the experiment duration ~ 3106 sec ~ 1.5 months
The measurement of the o-Ps life time with o-Ps in-flight
Reference and movableco-ordinate detectors
o-Ps
x
Semitransparent wheel Impermeable (re)movable plate
(Re)movable calibration Na22 source
Annihilation in a target
via para-state
If such a discrepancy does exist what can be a reason?
A) Hypothesis of the light, neutral, short-lived boson
B) Hypothesis of “The Mirror Universe”
4. Search for a probable channel of o-Ps annihilation via a light, neutral, short-lived boson:
o-Ps => + A0 , A0 => 2 .
The resultant upper-limits at 90% confidence level on the branching ratio of + A0 decay in comparison with the existing limits
1.00E-07
1.00E-06
1.00E-05
1.00E-04
1.00E-03
1.00E-02
0 200 400 600 800 1000 1200
m (keV)
Bra
nch
ing
ra
tio
O-Ps decay time discrepancy
1
2
3
4
5
Branching ratio
10-3
10-5
10-7 0 200 400 600 800 1000mA0 (keV)
2
3
54
1
1. U. Amaldi et al., Phys. Lett. B 153, 444 (1985)2. S. Orito et al., Phys. Rev. Lett. v63, 597 (1989)3. M. Tsuchiaki et al., Phys. Lett. B 236 (1990)4. Akopyan et al., Phys. Lett. B 272, 443 (1991)5. S. Asai et al., Phys. Lett. B 323, 90 (1994)
If mA0 =<1 MeV/sec2 => Probability (12.8)x10-5 for mA0 < 30 keV/sec2 life < 10-13 (mA0c2)keV sec
5. Hypothesis of "Mirror Universe»The Basic Idea:I Kobzarev, L.Okun, I.Pomeranchuk, Yad. Fiz., 3 (1966)
CP-violation L- particles (“usual”) R-particles (“mirror”)( introduced by T.D.Lee and C.N.Yang in 1960)L- and R- particles can interact only by exchange with
photons or gravitons .
The idea of a test:S.Glashow, Phys. Letters 167B(1986)35 -Positronium as a test system .
Antihydrogen generation in-flight =>=> CPT theorem test (future development)
AD (CERN)
LEPTA
e+
p~
H~
e
e
We plan to obtain H0 flux of intensity of 104-105 atoms/sec
Perimeter, m 80
Antiproton energy, MeV 50 0.5
Number of stored antiprotons 11011 1109
Antiproton flux
Intensity, sec-1 3104 30
Angular spread, rad 1.1 8.5
Velosity spread, 10-6 1.1 8.5
Antiproton ring parameters :
Experiments with H0 in flight:- Direct comparison of particle electrical charges- Microwave spectroscopy of the 2S-2P states of H0
- The atomic interferometer and Stern-Gerlah method. Spectroscopy of the 1S state- Laser spectroscopy of fast antihydrogen atoms
Parameter Accuracy
Attained Expected
Difference of antiproton and positron electric charges, e/e
2 10-5 2 10-9
The same for the e-, e+, proton and antiproton, e/e 2 10-5 2 10-8
Antiproton magnetic moment, a/a 3 10-3 2 10-5
Difference of the proton and antiproton magnetic moments, /
3 10-3 1 10-7
HFS of the ground state of antihydrogen, / . . . 2 10-5 - 1 10-6
HFS of the ground state of the 2S1/2 level and Lamb
shift of the 2P1/2 level of antihydrogen, /. . . 2 10-5 - 1 10-6
Energy of 1S-2S transition in antihydrogen, / . . . 3 10-7 - 1 10-11
Accuracies of the experimental values of the fundamental particles parameters
November 2002
Work in progress
The end.
http://lepta.jinr.ru
o-Ps o-Pse
e
e+ e+
What can be observed?One can detect o-Ps (“L-system”),
however one can NOT detect o-Ps (“R-system”)
The probability of “attendance” of o-Ps is equal to
= the o-Ps decay rate in Lab. Ref. Frame.
S.Glashow: f, f 87 GHz, ?
tcose 2t2
PsoPso
.
An interaction of Left o-Ps and Right o-Ps :
Estimations of :S. Glashow (1986)
E.Carlson and S.Glashow (1987)
S.Gninenko (1994)
The Task for experiment: to measure the distribution
The experiment resolution follows from here:
2t2t t1e0Ntcose0NtN
.vx
t,tt0NtNn 2 Correspondingly, one has to provide
62max
2 103.6vL
t
at L = 10 m and = . Thus, parameters of the experiment #3.3 do fit the requirements!
The data acquisition duration necessary for providing
of the desirable resolution
hoursDetector type o-Ps direct o-Ps and/or annihilation
detection -quanta detection
Detector with MCP 50 500Silicon strip detector 16 160
Co-ordinate -detectors
The view in transverse plane
tg = 1/
p-Ps
Magnet coilsMagnet yoke
p-Ps generation and decay in magnetic field
2.4. p-Ps => ~ (???)
??
~??
B
B