Review and prospects of the Review and prospects of the CAST - - PowerPoint PPT Presentation

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Review and prospects of the Review and prospects of the CAST - - PowerPoint PPT Presentation

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Review and prospects of the Review and prospects of the CAST experiment CAST experiment Konstantinos Kousouris Outline Outline Axion physics Strong CP problem Peccei-Quinn solution Axion properties The CAST experiment

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SLIDE 1

Review and prospects of the CAST experiment Review and prospects of the CAST experiment

Konstantinos Kousouris

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SLIDE 2

Outline Outline

Axion physics

Strong CP problem Peccei-Quinn solution Axion properties

The CAST experiment

Solar axions Concept & Design Detectors

Results from Phase I Prospects of Phase II

HEP2006, Ioannina 2 Konstantinos Kousouris

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SLIDE 3

The Strong CP problem The Strong CP problem

HEP2006, Ioannina 3 Konstantinos Kousouris

2 s 2

g L G G 32

μν μν θ

θ = ⋅ π

  • Non trivial QCD vacuum

Electroweak sector

q

Arg(det(M )) θ θ = + 1 G G 2

αβ μν μναβ

= ε

  • theory

15 10 n exp 25 n

Neutron electric dipole moment: d 10 e cm 10 d 0.63 10 e cm

− − −

⎫ ≈ θ× ⋅ ⇒ θ ⎬ < × ⋅ ⎭ ∼ Why do the contributions to cancel so perfectly?? θ

( )

s

G G K g K 2 A A A A 3

μν μ μν μ α β γ β γ μ μναβ

⋅ = ∂ ⎧ ⎫ = ε ⋅ ∂ + × ⎨ ⎬ ⎩ ⎭

  • Extra term in the QCD Lagrangian:

CP violating, total derivative, not affecting the perturbative behaviour of the theory.

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SLIDE 4

The Peccei-Quinn mechanism

HEP2006, Ioannina 4 Konstantinos Kousouris

PQ symmetry: global, axial, beyond the standard model. PQ symmetry: global, axial, beyond the standard model.

Axion

Goldsone boson, pseudoscalar, neutral, with gluon interaction through the triangle anomaly

Axion

Goldsone boson, pseudoscalar, neutral, with gluon interaction through the triangle anomaly

Spontaneously broken at some scale fa Spontaneously broken at some scale fa

The axionic field develops a non zero vacuum expectation value which eliminates the CP violating term. The axionic field develops a non zero vacuum expectation value which eliminates the CP violating term. Model dependent constant

( )

2 s a 2 a

g L C a x G G 32 f

μν μν

= ⋅ π

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SLIDE 5

Axion properties

HEP2006, Ioannina 5 Konstantinos Kousouris

a

Electromagnetic interaction 1 L g aF F 4

μν αγγ μν

=

  • 2

em PQ fermions

C Q Q = ∑

7 a a

Axion mass 10 GeV m 0.6eV f ≈

2 2 a

e g C 2 f

αγγ =

π

Original axion: fa = few (ruled out) Invisible Invisible axion: fa >> few , ΛQCD

DFSZ model (the PQ charge is carried by

  • rdinary quarks and leptons)

KSVZ model (Hadronic axion: the PQ charge

is carried by an exotic quark)

( ) ( )

23 5 a

Axion lifetime 10 τ α γγ sec m eV → ⎡ ⎤ ⎣ ⎦ ∼

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SLIDE 6

Solar axions

HEP2006, Ioannina 6 Konstantinos Kousouris

2 2 2 2 4 2

Primakoff effect p p d g Z e d 32 p p

α γ α→γ αγγ α γ

× σ = Ω π −

  • Photon – axion conversion in

the Coulomb field of a nucleus.

  • Hadronic axions (KSVZ)
  • Primakoff effect
  • Charge screening effects
  • Standard Solar Model

2 11 2 1 10 1

E 4.2 keV g 3.67 10 cm s 10 GeV

α αγγ − − α − −

= ⎛ ⎞ Φ = × ⎜ ⎟ ⎝ ⎠

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SLIDE 7

Axion parametric space

HEP2006, Ioannina 7 Konstantinos Kousouris

Sources Sources

  • Helioscopes.
  • Laser (rotation of elipticity).
  • Dark Matter search.
  • Astrophysics (evolution of the

Sun and HB stars).

  • Cosmology

(axionic relic density should not overclose the universe).

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SLIDE 8

The CAST principle

HEP2006, Ioannina 8 Konstantinos Kousouris

Inverse Primakoff effect

( )

2 2 L L/ 2 2 2

Axion - Photon conversion in a transverse magnetic field B g P 1 e 2e cos qL 4q

αγγ −Γ −Γ α→γ

⎡ ⎤ = + − ⎣ ⎦ + Γ

2 2

Momentum transfer m m q 2

α γ

− = Ε

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SLIDE 9

The CAST experiment

HEP2006, Ioannina 9 Konstantinos Kousouris

  • Decommissioned LHC, test

dipole magnet. Superconducting, I = 13kA, T = 1.8K. B = 9T, L=9.26m.

  • ±8o vertical, 80o horizontal

movement.

  • 1.5h Sun tracking during both

sunrise and sunset.

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SLIDE 10

The detectors

HEP2006, Ioannina 10 Konstantinos Kousouris

Telescope and CCD CCD

  • Wolter I optics, prototype for the ABRIXAS space
  • mission. 27 nested gold coated nickel shells.

Axionic image of the Sun.

  • Charged Coupled Device (solid state photon

detector from Si). Pixel size: 150x150 μm2.

  • Spot: 3mm diameter, improving significantly the

CAST sensitivity.

  • Covers one magnet bore and tracks sunrise axions.

TPC TPC

  • Time Projection Chamber: conventional

gas chamber with 48 anode wires and 96 cathode wires, 3mm apart.

  • Shielded. Constructed by Zaragoza Univ.
  • Covers both magnet bores and tracks the

sunset axions. MICROMEGAS MICROMEGAS

  • Novel micropattern parallel plate gas

detector with spatial sensitivity.

  • Constructed by Saclay and Demokritos.
  • Covers one magnet bore and tracks the

sunrise axions.

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SLIDE 11

PHASE I (2003 run)

HEP2006, Ioannina 11 Konstantinos Kousouris

Magnet bores in vacuum vacuum: axion-photon oscillation coherent for axion masses m ma

a<0.02 eV

<0.02 eV

Analysis completed (Phys. Rev. Lett. 94 (2005) 121301

  • Phys. Rev. Lett. 94 (2005) 121301)

NO axion signal NO axion signal

10 1

95% C.L. (Bayes) upper limit g 1.16 10 Ge Combined re V sult

− − αγγ <

×

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SLIDE 12

PHASE I (2004 run)

HEP2006, Ioannina 12 Konstantinos Kousouris

All detectors significantly improved

CCD

10 1

95% C.L. (Bayes) upper limit g 0.9 10 GeV Combined result

− − αγγ <

× preliminary

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SLIDE 13

PHASE II (2005-2007)

HEP2006, Ioannina 13 Konstantinos Kousouris

Magnet bores filled with buffer buffer gas gas: effective photon mass

( ) ( )

em e e

P mbar 4 N m 0.02 eV m T K

γ

πα = =

  • 4He: 74 pressure steps, 0 < P < 6mbar, ma < 0.26eV.
  • 3He: 590 pressure steps, 6 < P < 60mbar, ma < 0.8eV.
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SLIDE 14

PHASE II (challenges)

HEP2006, Ioannina 14 Konstantinos Kousouris

Cold windows Cold windows

  • High transmisivity in the 1-7 keV region.
  • Minimizing He leak rate.
  • Withstand pressure differences during a “Quench”.
  • Robust under normal operating conditions at 1.8K.

Gas system Gas system

  • Control of pressure steps.
  • Restore of previous pressure settings.
  • Recovery of gas in case of a “Quench”.
  • Safe storage of the gas.
  • Control of gas dynamics (thermoacoustic
  • scillations).

Additional optics device Additional optics device Extra X-ray focusing device installed in a new Micromegas line. Increase

  • f the overall CAST sesnitivity.
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SLIDE 15

Conclusions

HEP2006, Ioannina 15 Konstantinos Kousouris

  • The strong CP problem remains unsolved for 30 years and the PQ solution is still the

most elegant and economic. Axions searches are worthwile!!!

  • The CAST experiment completed PHASE I with sensitivity to axion masses ma<0.02 eV

and no signal was discovered. However, it improved the axion - photon coupling limit significantly and reached the Astrophysical limit.

  • The 2003 run analysis results are already published while the 2004 results will be

published soon.

  • The CAST Phase II was approved by CERN and will last until fall of 2007 (Already

started).

  • During Phase II the CAST magnet bores are filled with gas (He) to make the experiment

sensitive to higher axion masses, enetering the theoretically most favoured region of the axion parametric space.

  • The technical challenges and demands of Phase II are being met succesfully and the

experience gained from Phase I allow the collaboration to be optimistic about the

  • utcome of the experiment.