pseudoscalars

Nuclear Physics B (Proc. Suppl.) 22A (1991) 1-7 North-Holland

SEARCH FOR COSMIC AXIONS AND EXPERIMENTAL LIMITS ON LIGHT SCALARS/PSEUDOSCALARS Yannis SEMERTZIDIS Dept . of Physics and Astronomy, University of Rochester, Rochester, NY 14627, USA We present here experimental limits on the coupling constant of axions to two photons describing two different experiments . For the first one (the search for cosmic axions) we assume that 100% of the dark matter is due to axions and we find gays < 10 -13 GeV-1 in the mass range of (4 .5-16 .3)X10 -6 eV . The second experiment does not assume the existence of dark matter but it is a production of light scalars and/or pseudoscalars with a polarized laser light inside a magnetic field . The observed peaks set a limit Of gays < 2 .5X10-6 GeV-i for a particle mass of m < 10 -3 eV .

PART I .

Search for Cosmic Axionsl

A major problem in Astrophysics is It first

the so called dark matter .

started with the observation that the orbital velocity distribution of the stars around the center of their own galaxy versus their distance from the same center flattens out for large r (fig . 1) . 2 The velocity distribution

FIGURE 1 should follow the 1/r form after some

FIGURE 2

distance R that defines the radius of the galaxy according to Newtonian

clusters .

which forms a much larger sphere that surrounds the galaxy (fig . 2) . Other

to 0 .1 of the required critical density

matter come from the measurement of the

missing part of the picture is the

physics, unless there is invisible mass

indications for the presence of dark

motion of the galaxies themselves within

Also the prejudiced idea that

our universe is flat whereas the

observed density accounts only for 0 .01 of 10 4 eV/cm3 .

A leading candidate to fill in the

axion3 ani assuming that axions

0920--5632/91/$03 .50 ® 1991 - Elsevier Science Publishers 13 .V . (North-Holland)

Y. Semertzidis/Search for cosmic axions

2

constitute 100% of the dark matter then it turns out that the local density must be 10 -25 g/cm3 = 300 MeV/cm 3 or 10 13 axioms/cm3 . 4

masses that are excluded from the

observation of the evolution of various types of stars7 (fig . 3) .

The axion is a consequence

of the Peccei-Quinn (P .Q .) symmetry5

Fa (GeV)

invented to solve the strong CP-problem .

Although alternative to the P.Q . symmetry solutions have been proposed,

16 10-

the axion is required in many

10' 5 -

theoretical models .

The axions couple to two photons through the triangle anomaly with a

10-5 -

coupling

10'°4

aN

9arr-2nF aC

C arr

_ 2 4+ x

(1)

31+x~'

where N is the number of quark families, Fa the scale at which the P .Q . symmetry

10

brakes down, a = 1/137 is the fine

DFS mode16 the term inside the

For the

parenthesis in (1) equals to 0 .7 .

The existence of such a particle that

couples to two photons has immediate

This comes from the fact that a

produced photon inside the core of the sun for example takes about 10 7 years

before it reaches the surface, with a mean free path of 1 cm . The sun

struggles to loose its energy, but if an axion exists the sun could loose its

energy much faster since it could travel from the core to the surface much faster carrying energy . If the coupling to two photons is too week they cannot be produced in large numbers and if it is too strong they would be captured inside

the star much like a photon . With these arguments in mind there is a range of coupling constants and correspondingly

Stellar evolution

5-

Accelerator experiments

ma(eV)

FIGURE 3 The lifetime of the axion to two

photons is

ti(a -) YY)

consequences for the evolution of the stars .

Supernova 1987 A

5j

10

structure constant, Cary is the ratio of the charge to color anomaly of the P .Q . symmetry, and z = mu/md = 1/2 .

Axions overdominote the universe

1049E

Fa 10'Z GeV

YY)

R Ma

S

N4

x3 1 +x 4

5

(2)

where ma is the axion mass and m,t the pion mass . Therefore they did not-decay since their creation at the early universe .

Sikivie8 proposed the inverse

Primakoff effect to stimulate their

decay and make their detection possible . In one of his ideas he is suggesting the use of a microwave cavity tuned to the axion mass, inside a solenoid magnetic

field and emerged into liquid helium in order to achieve high quality factors for the cavity (fig . 4) . The interaction Lagrangian is

` - 9a vv E  ' B.,,4) . wh r

~ayv

I .3x I® -m GadV' I m ® / I ®®~~V is

the the ext axion DFS exact the electric the indicates 1field resonance 5) produced Next(X) volume model, 10-24W) solenoid the 104CI113 magnetic microwave coupling frequency from 1 Only is external 12field The the and Ky d3x the 0photon, TM frequency X105 magnetic is and field expected 10-25 G 1cavity local to f degree of modes of the Bext' 4in the magnetic two 09/em the the Bext iand electric practice axion Éid3x Egive form photons is field, of cavity power axion (Patuned the alignment 1field factor Gi the density, is 12GHz Semertzidis/Search mass out Vmode field cavity, only the for lto the and for cosmic®Tmixing can stage axions cavity range from comm/ rod by be amThis the alow W/f1r used with of (fig is post eaWbr~aloc~ mechanism about noise cavity tuned with high amplifier 6) 5preamplifier 15% with high dielectric 6is aaO Thedirected enables aThe efficiency tuning 7~w YM7and lossless power aaEEE to two rod ~a

Y.

3

FIGURE the the of external axion when the

is . is

P=(2 .2x X

G2=

V [

with

l

IS

2

B 6T

FIGURE

G .7

Q

I

Wcr .. .n f/wrMf~7N 1] ;d3x

.

.

.

..... .. Yn.r

.

... .. ... .. S,-N r0/0 G11MriLA .rr" r

Arft ~ .s .r. 019

Éi .

f

where f Bext cavity that between the . (fig . different

TM010 The sapphire constant . tuning output three followed stage

WEE ;

nmwn~ imT tang

~~..r w02 sre" .fcr Yu.gre .r.~rnr FIGURE

ff.

.

im-

Y. Semertzidis/Search for cosmic axions

and the high frequency synthesizer of the first stage mixing are synchronized so that the input power to the second mixing stage is always at the same frequency . The online software keeps track of the synthesizer sweep and combines the output power at the right frequency bins. A sample of the spectrum is shown in figure 7 . The experiment was completed at the end of summer 1989 and the results were published in Physical Review D40, 3153 (1989) by W . Wuensch et al . In figure 8 is shown the obtained limits of the 45XID 23

N 3

35

r

40

av

35 23.4

I

23.5

I

23.6 f -1.5 GHz

I

23.7 (MHz)

axion coupling constant to two photons versus its mass . The straight lines show the axion coupling constants for two different models . Our limits are greater by a factor of 10 to 100 from the theoretical models . Other groups are continuing this effort here in the USA and in Japan.

PART II . Limits on the Production of Light Scalar and Pseudoscalar Particles 9 The previous experiment assumes that the axions are constituting the so called dark matter . Since the axions couple to two photons it is possible to produce them by shining a laser beam inside a magnetic field . 10 The interaction Lagrangian is the same as in eq . 3 . A polarized laser beam entering the dipole magnetic field region with the polarization plane at 45° with respect to the external magnetic field will rotate . This because only the parallel to the external magnetic field component will produce axions and thus will attenuate whereas the orthogonal component will not (fig . 9) . The

Bext 2'epsilon

811-

FIGURE 8 FIGURE 9

Y. Semertzidis/Search for cosmic axions

h

produced axions could recombine with a virtual photon provided by the magnetic field and yield the original photon . Due to the finite axion mass the parallel to the magnetic field

polarization will retard . This will cause some small ellipticity to the original linearly polarized laser beam .

The rotation and ellipticity angles are given byii 2

2

E = Nge yy Bext - sin2 a

sin 20

region, w is the photon energy, l the magnetic field length, and 0 the angle

between the light polarization and the external magnetic field. The rotation for small axion masses becomes

1

E=N gayyBext 6sin20 .

(6)

2[ M 21 W= gayyBextm4 -sin 2 a Zuu

2

W = Nga yy Bext

2uu )]

sin 20

polarization is heterodyned by the

Faraday cell (FC) and then it passes

through the analyzer (A) which is set for best extinction .

The quarter wave

plate (QWP) is used only when the sought after effect is ellipticity.

The (QWP)

transforms the ellipticity into a rotation of the same amplitude .

with a period of 25 .6 s.

The

m2 1 3 c)

6w sin20 .

(8)

acquires an ellipticity due to QED vacuum polarization 12 2

2 B extWl

15m e

sin20

with me the electron mass and oc_ 1/137 the fine structure constant .

The photon beam is produced by a 5W

argon ion laser and is polarized by the (fig . 10) .

The light

collected by the photodiode is

A polarized laser beam in vacuum also

polarizer (P)

FIGURE 10

dipoles13 modulated from 1 .71 to 2 .48 T

which for small axion masses becomes

= Na

ownsim

1258 mop kd caft

magnets used are two CEA superconducting

The ellipticity is

'V~QED

WPM

(5)

where N is the number of times the laser beam travels inside the magnetic field

2

Lai

After is

polarized it enters the magnetic field region where it bounces on the cavity

mirrors for a couple of thousand times . Exiting the magnetic field the rotated

1=1 0 [0

2

2

+ 2 +2aT j o cos(2n f Ft + W

+Tj o E o cos[2n(f F -

I

M)t+(`PF-~01

+rl .E,cos[2n(IF+Im)t+(~F+em))

(10)

2

+ 2°cos(4njFt+2~F)1 where Io is the light intensity before (I _ 10_' the analyzer, is the extinction, a= 10 -6 rad is the misalignment between

the polarizer and the analyzer, fF=260 Hz is the (FC) frequency, fM=39 .0625 mHz 10-4 is the magnet frequency, and Tl,, = 7 x rad . The rotation induced by the magnetic field is Eo

0 1 1Eà1 àf = TI 2 121f

,

Y. Semertzidis/Search for cosmic axions where I j,,j . is the power at the

heterodyned signal frequency, and the power at the twice the (FC)

Rotating the light polarization to 0° 121E

with respect to the external magnetic

field the peaks appeared at about half

frequency .

the level whereas there should be no

in fig. 11 ; there is more than two

light beam due to axion production . The nature of these peaks is puzzling and we

A typical rotation spectrum is shown

1E-5

0

c 2 'ô ô

rotation/ellipticity induced to the

hope to resolve it during the next run on Fall of 1990 .

t E-6 1E-7 1E-8

References

t E-9 -3M625 -234.375 -78125

78 .125

234.375

390,625 (mHz)

Frequency - 260 Hz

1)

The other members of this

collaboration were :

FIGURE 11 sidebands, because of the nature of the

magnetic field modulation . The observed rotation is E o = 4 .3 x 10 -8 rad, which implies a limit of

gavv<2 .5x 10 -6 GeV -1

(12)

A for the axion coupling constant . similar run for ellipticity showed peaks

W.U . Wuensch, S . De

Panfilis, J.T . Rogers, A .C . Melissinos, H .J . Halama, B .E . Moskowitz, A .G . Prodell, W .B . Fowler, and F.A . Nezrick . 2)

F . Zwicky, Helv . Phys . Acta 6,

(1933) . 3)

110

S . Weinberg, Phys . Rev . Lett . 40,

at the 2 .9 x 10 -$ rad level, and the

223 (1978) ; F . Wilczek, Phys . Rev. Lett . 40, 279 (1978) .

ellipticity are shown in fig . 12 .

4)

obtained limits for both rotation and

M.S . Turner, Phys . Rev . D33, 889 (1986) .

5)

R. Peccei and H . Quinn, Phys . Rev . Lett . 38, 1440 (1577) ; Phys . Rev. D16, 1791 (1977) . 6)

M. Dine, W . Fischel, and M . Srednicki, Phys . Lett . 104B, 199 (1981) . i) frudoscnlar/Sonlor

FIGURE 12

moss

(eVJ

G. Raffelt ahd D . Seckel, Phys . Rev . Lett . 60, 1793 (1988) ; J . Preskill, M .B . Wise, and F . Wilczek, Phys . Lett . 120B, 127 (1983) .

Y. Semertzidis/Search for cosmic axions

8)

P. Sikivie, Phys . Rev . Lett . 51,

9)

The other members of this

10) L. Maiani, R. Petronzio, and E .

7

1415 (1983) .

Zavattini, Phys . Lett . 8175, 359 (1986) .

collaboration are :R . Cameron, G.

Phys . Rev. D37, 1237 (1988) .

H . Halama, A. Prodell, F . Nezrick, C.

599 (1971) .

Cantatore, A .C . Melissinos, J . Rogers, Rizzo, and E . Zavattini .

The results of

this part were published in Phys . Rev. Lett . 64, 2988 (1990) by Y . Semertzidis et . al .

11) G.G . Raffelt, and L. Stodolsky,

12) S .L . Adler, Ann. Phys . (N .Y .) 87,

13) E.J . Bleser et al ., Nucl . Instr.

Methods Phys . Res . Sect . 1235, 435 (1985-1 .