axions presentation
TRANSCRIPT
-
8/14/2019 Axions Presentation
1/20
-
8/14/2019 Axions Presentation
2/20
WHAT IS AN AXION?
1.Axion and The Strong CP problem2.Limits for the mass of axions
3.Axion and Dark Matter4.Identity Card of Axions
5.How does one look for Axions?
6.The CAST experiment7.The PVLAS experiment
8.Results
9. Conclusion
-
8/14/2019 Axions Presentation
3/20
Reminder of P,C and CP Oprations
Parity Operator (P)
Charge Conjugaison Operator (C)
(CP) Operation
-
8/14/2019 Axions Presentation
4/20
The Strong CP problem
The rules followed by theStrong interaction obeydiscrete symmetries P
and CP.
These symmetries havebeen known for a longtime. The discovery that
weak interaction violates
P and CP = big surprise
Indeed, physicists usedto see strong and EMinteractions obeying Pand CP.
Kaons Violate CP
symmetry by weak
interaction
-
8/14/2019 Axions Presentation
5/20
Strong Cp problem and Axions
how can the strong interaction, which is part of the Standard Model,
conserve P and CP?
Here is the guy:
there are some natural terms whichappear in the QCD Lagrangian expressionto be potentially able to describe abreaking of the CP theory.
Problem is:
-
8/14/2019 Axions Presentation
6/20
Strong CP problem and Axions
the most sensitive test of P
and CP violation by the
strong int. : requires the teta
of QCD be less than 10^(-9).
Peccei-Quinn
solution:modifiy the Model by
adding a new sym.(PQ) andmaking the teta angle of
QCD a dynamical variable
rather than a simple arbitrary
constant
in quantum field: each field
produces a particle
the hypothetical particle
corresponding to this field
was called axion.
The potential which this fieldnaturally obtains causes it to
have a value which makes
the effective parameter
vanish.no problem anymore
-
8/14/2019 Axions Presentation
7/20
Mass Limits on Axions THEORICAL ARGUMENT
As for the Pecceni-Quinn theory: ~1.8MeV
REACTION OBSERVATION ARGUMENT
an axion heavier than 1keV would lead to new particles physics
reactions (decay into K+ and +), but these never occured
< 1keV
ASTROPHYSICAL OBSERVATION ARGUMENT
axion mass must be no more than 103 electronvolts < 103 eV
COSMOLOGICAL ARGUMENT
If axion is lihgter than 1microeV, its relique density in primitive
universe would be higher than the actual observed density of total
energy in the Universe > 106 eV
-
8/14/2019 Axions Presentation
8/20
Mass Limits and Dark Matters To sum up the most likely mass limits on axion are:
106
< m(axion) < 103
eV Now: what is dark matter?
mass of matter in the universe that cannot be observed by direct observations of its
emitted or absorbed electromagnetic radiation.
number of astrophysical observations that suggest that the actual mass of universe is
greater than estimated by observation using optical telescopes, radiotelescopes..etc.
It is thought to be a considerable amount of dark matter (hidden matter) causing thisdiscrepancy
-
8/14/2019 Axions Presentation
9/20
Mass limits and Dark Matter
Various explanations have been put
forward for this missing mass, including
black holes, brown dwarfes, cosmic
strings, neutrinos, monopoles, WIMPS
and...
As we can see, the axion seem
to be a good candidate to be a
part of the dark matter!
-
8/14/2019 Axions Presentation
10/20
Properties of Axions
Hypothetical pseudo-Goldstone boson particles, stable
particles, almost do not interact with matter
Axion mass is given by :
Axions coupling with photon is given by:
with :
Primakoff effect: conversion of photons into axions
-
8/14/2019 Axions Presentation
11/20
How does one look for axions?It depends where do they come from
Galactical Axions- Haloscopes (ADMX, CARRACK)
microwave cavity + magnetic field
Laboratory Axions- Regeneration Light Shinning through wall
- Polarisation (PVLAS)
laser + magnetic field
Axions produced in the sun- Helioscopes (CAST, TOKYO)
- Cristal detectors (SOLAX, COSME,
DAMA)
sun + magnetic/electrical field
-
8/14/2019 Axions Presentation
12/20
How does one look like for Axions?
Axions in laboratory
Light shinning through a
wall
Axions in the Sun
Helioscopes
Polarisation:
polarised laser through a
vacuum with a tranverse
magn.field.
Cristalline detectors:
Primakoff + Braggs
condition
-
8/14/2019 Axions Presentation
13/20
CAST:Cern Axion Solar Telescope
Moving LHC dipole: L= 9.3m B= 9 Tesla
Sun tracking 3hours/day
3 X-Rays detectors
Measured signal: excess of X-rays when
pointing to the sun
-
8/14/2019 Axions Presentation
14/20
CAST: Production and detection Production in the Sun
Inside the
sun:interaction photon-
nucleons by primakoff
Detection Principle
Conversion probability:
Expected # photons:
~ 7events/day
A
-
8/14/2019 Axions Presentation
15/20
CAST:X-Ray detector
-
8/14/2019 Axions Presentation
16/20
PVLAS:Polarizzazione del Vuoto con Laser Polarized laser through B=5T
Goal: measure modification of polarization of light QED forecast interaction btw photons-B:ellipticity Ellipticity due to birefringence of vacuum (changes in refractive
indices for different polarization vectors) depending on B
Linear polarization(45)
Elliptical polarization
-
8/14/2019 Axions Presentation
17/20
PVLAS: experimental Setup
Photo elsastic Modulator
6.5T
Fabry-Perrot resonator
-
8/14/2019 Axions Presentation
18/20
PVLAS:measured effects
Production and destruction
of virtual particle:change of
ellipticity
Real production of
particle:rotation of the plane
of polarization(dichroisme)
-
8/14/2019 Axions Presentation
19/20
Results
-
8/14/2019 Axions Presentation
20/20
Conclusion
Axions remain to be a promising
solution to the CP problem
They additionally provide a well-motivated candidate for dark matter
Experiments are being pursued and
improved for dicover certainly in acouple of years axions.