Search for Solar Axions:the CAST experiment at CERN

Aisha Hunte

for the CAST CollaborationJune 2004,

CERN

CERN, 29th June 2004Aisha Hunte Search for Solar Axions: The CAST experiment

AxionsααThe STRONG CP PROBLEM

Possible CP-violating term in QCD lagrangian:

( )

Experimental consecuence: prediction of electric dipole moment for the neutron:

(A = 0.04 – 2.0)

BUT experiment says...

So,

Peccei-Quinn (1977) propose an elegant solution to this problem. not anymore a constant, but a field the axion a(x).

CERN, 29th June 2004Aisha Hunte Search for Solar Axions: The CAST experiment

The STRONG CP PROBLEM: Peccei-Quinn solution•New U(1) symmetry introduced in the SM: Peccei Quinn symmetry of scale fa

•The AXION appears as the Nambu-Goldstone boson of the spontaneous breaking of the PQ symmetry

absorbed in the definition of a

axion – gluon vertex

•a qq transitions•a – 0 mixing•axion mass > 0

Dark matter candidate!

PQ Symmetry:

Peccei & Quinn: CP invariance of the strong interactions expected in QCD, for a non vanishing scalar field that gives mass to a fermion through a Yukawa coupling.

Axionsαα

CERN, 29th June 2004Aisha Hunte Search for Solar Axions: The CAST experiment

Axionsαα

pseudoscalar

neutral

practically stable

phenomenology driven by the breaking scale fa and the specific axion model

Couples to photonL = g (E•B) a

Primakoff (1951) []

PRIMAKOFF EFFECT

axion-like particles

Any scalar or pseudoscalar particles:

CERN, 29th June 2004Aisha Hunte Search for Solar Axions: The CAST experiment

Axionsαα

Stellar interior the Sun!! Solar AxionsFlux at the

Earth

PRIMAKOFF EFFECT

[K.van Bibber et al.,1989]

CERN, 29th June 2004Aisha Hunte Search for Solar Axions: The CAST experiment

L

X-ray

detector

Transverse magnetic field (B)

X-ray

Axionsαα

Sensitive for m < 10-2 eV

Signal: X-rays while tracking

(magnet pointing to the Sun) over

background

Lazarus et al., Brookhaven

Tokyo Helioscope:B~4T, L~2m

CERN, 29th June 2004Aisha Hunte Search for Solar Axions: The CAST experiment

Axions

Phase II and up (?)

CAST Sensitivity plot

Filling the magnet bores with 3He the photon acquires an effective mass: mγ > 0 and by changing the gas pressure we are sensitive to different masses up to ~ 1 eV

To Start in 2005

CERN, 29th June 2004Aisha Hunte Search for Solar Axions: The CAST experiment

Sunset

Photon detectors Sunrise

Photon detectors

Sunset axions

Sunrise axions

CERN Axion Solar Telescope

Decomissioned LHC test magnet

Rotating platform

3 X-ray detectors

X-ray Focusing Device

Decomissioned LHC test magnet

Rotating platform

3 X-ray detectors

X-ray Focusing Device

CERN, 29th June 2004Aisha Hunte Search for Solar Axions: The CAST experiment

LEP Point 8 (former DELPHI

point)Building 2875

CAST is here:

CERN, 29th June 2004Aisha Hunte Search for Solar Axions: The CAST experiment

Magnet,platform,cryogenics

Magnet Feed Box

4He flexible line

CAST Experimental area

SR8

L= 10 m

B=9 T

100 times better conversion efficiency than any other !!

CERN, 29th June 2004Aisha Hunte Search for Solar Axions: The CAST experiment

Magnet,platform,cryogenics

Twice a year (September&March) we can

film the Sun through the window

Twice a year (September&March) we can

film the Sun through the window

Looking at the

sunrise…

SEPTEMBER’03

MARCH’03

CERN, 29th June 2004Aisha Hunte Search for Solar Axions: The CAST experiment

On the coming sesion:

The X-Ray Telescope & X-Ray Detectors

X-Ray Telescope (Focusing Device)

Detectors

CCD

TPC

Micromegas Big value of B • L

Low background rate detectorsX-Ray Telescope!!!