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