search for solar axions: the cast experiment at cern cast.web.cern.ch/cast
DESCRIPTION
Search for Solar Axions: the CAST experiment at CERN http://cast.web.cern.ch/CAST/. Berta Beltrán (University of Zaragoza, Spain) XXXXth Rencontres de Moriond La Thuile, March 2005. Outline. The physics behind CAST : Axions. Principle of detection The CAST experiment : Description : - PowerPoint PPT PresentationTRANSCRIPT
Search for Solar Axions:the CAST experiment at
CERNhttp://cast.web.cern.ch/CAST/
Berta Beltrán (University of Zaragoza, Spain)
XXXXth Rencontres de Moriond La Thuile, March 2005
La Thuile, March 2005 Berta Beltrán 2
Outline The physics behind CAST: Axions. Principle of detection
The CAST experiment:Description:
• Magnet, tracking, …• X-ray detectors.
Data Analysis and 2003 results.
La Thuile, March 2005 Berta Beltrán 3
Axions : Motivation
The Axion is a light pseudoscalar resulting from the Peccei-Quinn mechanism to enforce strong-CP conservation
[Peccei-Quinn(1977),Wilczek (1978), Weinberg(1978)]
Axions may exist as primordial cosmic relics copiously produced in the very early universe, and these axions are one of the most interesting non-baryonic cold dark matter candidates.
[See the PDG for an interesting review on axions]
La Thuile, March 2005 Berta Beltrán 4
The Sun as an axion source
γ a
-eZe
[K. van Bibber et al. PRD 39,(1989)]
Thermal photons Fluctuating electric fields of the
charged particles in the hot plasma
Axions
Differential solar axion flux at
Earth. 2
GeV10
g110
aγγ
Solar physics+
Primakoff effect
La Thuile, March 2005 Berta Beltrán 5
CAST: Principle of detection
Expected number of photons in the x-ray detector:
L
Transverse magnetic field (B)
X-ray detector
X-ray (same energy and momentum)Axion
[Sikivie PRL 51 (1983)]
aγaa
aγ dEtSP
dE
dΦN a
a
dE
dΦ
γaP
S
t
Differential axion flux at the Earth(cm-2 s -1 keV -1 )
Conversion probability of an axion into photon ( (B×L)2)Magnet bore area (cm2)
Measurement time (s)
For gaγγ =1×1O-10 GeV-
1
t=100 h , S=15 cm2
N γ ≈ 30 events
La Thuile, March 2005 Berta Beltrán 6
But this γaP is a coherent process only when the axion and photonfields remain in phase over L
witha
2a
2γ
E2
mmq
Coherence condition states that qL < 1 (axion-
photon momentum transfer)
Vacuum inside the magnet: mγ =0 We are sensitive to axion masses ≤ 2.3×10 -2 eV (CAST phase I)
T(K)
P(mbar) 0.02(eV)mγ
Buffer gas (He) inside the magnet: mγ,eff > 0
Different gas pressures P will make us sensitive to different axion masses up to 1 eV (CAST phase II)
La Thuile, March 2005 Berta Beltrán 7
University of British Columbia, Department of Physics, Vancouver, CanadaMichael HASINOFF
Ruder Boskovic Institute, Zagreb, CroatiaMilica KRCMAR, Biljana LAKIC, Ante LJUBICIC
Centre d''Etudes de Saclay (CEA-Saclay), DAPNIA, Gif-Sur-Yvette, FranceSamuel ANDRIAMONJE, Stephan AUNE, Esther FERRER, Ioanis GIOMATARIS, Igor G. IRASTORZA
Technische Universitat Darmstadt, Institut für Kernphysik, Darmstadt, GermanyTheopisti DAFNI, Dieter HOFFMANN, Manfred MUTTERER, Yannis SEMERTZIDI, Hans RIEGE
Johann-Wolfgang-Goethe Universität Frankfurt, Institut für Kernphysik, Frankfurt Am Main, GermanyVladimir ARSOV, Joachim JACOBY
Albert-Ludwigs-Universität Freiburg, Freiburg, Germany Horst FISCHER, Jurgen FRANZ, Donghwa KANG, Kay KONIGSMANN, Fritz-Herber HEINSIUS
Max-Planck-Gesellschaft (MPG) Max-Planck-Institut für Extraterrestrische Physik, Garching, GermanyHeinrich BRAEUNINGER, Jakob ENGLHAEUSER, Peter FRIEDRICH, Markus KUSTER
Max-Planck-Institut fur Physik Muenchen, GermanyRainer KOTTHAUS, Gerhard LUTZ, Georg RAFFELT, William SERBER,Pasquale SERPICO.
Aristotle University of Thessaloníki, Thessaloniki, GreeceChristos ELEFTHERIADIS, Anastasios LIOLIOS, Argyrios NIKOLAIDIS, Konstantin ZIOUTAS, Ilias SAVVIDIS.
Scuola Normale Superiore (SNS), Pisa, ItalyLuigi DI LELLA
Russian Academy of Sciences, Institute for Nuclear Research (INR), Moskva, RussiaAlexandre BELOV, Sergei GNINENKO, Nikolai GOLUBEV
Instituto de Física Nuclear y Altas Energías, Universidad de Zaragoza, Zaragoza, SpainBerta BELTRAN, Jose Manuel CARMONA, Susana CEBRIAN, Gloria LUZON, Angel MORALES, Julio MORALES, Alfonso ORTIZ DE SOLORZANO, Jaime RUZ, Jose VILLAR, Maria Luisa SARSA.
European Organization for Nuclear Research (CERN), Geneve, SwitzerlandKlaus BARTH, Enrico CHESI, Martyn DAVENPORT, Christian LASSEUR, Thomas PAPAEVANGELOU, Alfredo PLACCI, Louis WALCKIERS,Laura STEWART, Dario AUTIERO.
Enrico Fermi Institute, University of Chicago, Chicago, Il, United States of AmericaDavid MIlLER, Juan COLLAR, Joaquin VIEIRA
University of South Carolina, Department of Physics and Astronomy, Columbia, Sc, United States of AmericaFrank AVIGNONE, Richard CRESWICK, Horacio FARACH
National Center for Scientific Research "Demokritos" (NRCPS), Athens, Greece George FANOURAKIS, Theodoros GERALIS, Konstantin KOUSOURIS, Katerina ZACHARIADOU.
CAST Collaboration
68 participants from 15 institutions
La Thuile, March 2005 Berta Beltrán 8
CAST: Point 8
CERN(Meyrin site)
Genève
CAST at CERN:
La Thuile, March 2005 Berta Beltrán 9
Sunset detector:
TPC
Magnet feed box
Sunrise detectors: CCD, Calorimeter,
µMegas80º
14º
10 m long LHC dipole prototype
CAST: Axion helioscope experimental setting
La Thuile, March 2005 Berta Beltrán 10
Description of the experiment: LHC MagnetSuperconducting LHC test dipole.
Use of superfluid 4He to cool the system down to 1.8 KL= 9.26 m long and magnetic field up to 9 Tesla.The magnetic filed is confined in twin pipes of ~14.5 cm2 area each.The aperture of each of the bores fully covers the potentially axion-emitting solar core (~1/10th of the solar radius)Mount on a moving platform allowing ± 8º V; ± 40º H
La Thuile, March 2005 Berta Beltrán 11
Tracking systemSnapshot of the tracking
programSoftware with astronomical calculations.Communicates with
the motors→ interface to move the magnet.
The overall CAST pointing precision in better than 0.01º Both the hardware and the software of the tracking system have been precisely calibrated by means of geometric survey measurements.
La Thuile, March 2005 Berta Beltrán 12
X-ray detectors: TPC (CERN)Position sensitive
Conventional technology: robustness and stability guaranteed Use of a passive shielding to reduce the level of the background.
4.13×10-5
counts/KeV/sec/cm2
1.85×10
counts/KeV/sec/cm2 Reduction by a factor ~4.5
200 mm POLYETHYLENE
25 mm LEAD
5 mm COPPER
2 mm CADMIUM
N2 FLUX 200 l/h
La Thuile, March 2005 Berta Beltrán 13
X-ray detectors: μMegas (Saclay/Athens/CERN)
20032003
20042004
Very good spatial resolution (350 μm X-Y strip pitch)
Low threshold (0.8 keV)
CAST prototype: two dimensional strip read out
La Thuile, March 2005 Berta Beltrán 14
X-ray focusing device + CCD (MPI/HLL)Focusing device;
Space technology (prototype for the ABRIXAS satellite)
From 48 mm Ø (LHC magnet aperture) →~3 mm Ø
Big signal to noise ratio improvement
About 35% efficiency due to reflections
The CCD camera: Very good energy resolution
(<0.5 keV) Low threshold Windowless operation in
vacuum: efficiency close to 100% in the full energy range.
43 43 mm mm
1.6 m1.6 m
3 3 mm mm
La Thuile, March 2005 Berta Beltrán 15
X-ray detectors: Calorimeter (Chicago)In the experiment only
during the 2004 data taking.The goal is to extend sensitivity to axion induced γ’s from few keV to ~150 Mev First time that this kind of search is performed.
La Thuile, March 2005 Berta Beltrán 16
CAST experiment: status2003 data taking Running for about six months. Data already analyzed → First CAST results (K.Zioutas et. al.
2005 PRL, in press).
2004 data taking Improved conditions in the three detectors (shiledings,
….). Add of a fourth detector (calorimeter) for High Energy
axions. Improvements in the tracking system and in the
magnet: more reliability and longer periods of data tacking.
Running from May to November without problems.
2005 Updating the experiment setup for the second phase of
CAST Analyzing 2004 data…
La Thuile, March 2005 Berta Beltrán 17
c/k
eV
/cm
2/ s
Solar-axion-photons spectrum for g ~ 6 x
10-10 GeV-1
(Tokyo Helioscope sensitivity)
CAST TPC Subtracted spectrum
Comparison of sensitivities of CAST and Tokyo Helioscope
Energy [keV]
TPC subtracted spectrum and “expected” axion-photons spectrum
La Thuile, March 2005 Berta Beltrán 18
CAST 2003 result
Subtracted spectrum TPC , μMegasTracking (dots) and background (dashed line) spectra of the CCD.
No signal over background in any of the three detectors.
La Thuile, March 2005 Berta Beltrán 19
CAST 2003 resultAxion exclusion plot
Combined upper limit obtained (95% C.L.):
gaγγ<1.16×10-10
GeV-1
La Thuile, March 2005 Berta Beltrán 20
Backup slides
La Thuile, March 2005 Berta Beltrán 21
Peccei-Quinn solution: is a dynamical variable with classical potential that is
minimized by =0. The prize for this is the introduction of an
additional spontaneously broken global symmetry and its associated pseudo-Goldstone
boson, the axion.
Axions: Motivation Strong CP problem: QCD lagragian has a non-perturbative term:
where
aa GG
~, field strength
tensor and its dual
g gauge coupling
and Θ→ QCD vacuum; M = quark mass matrix
This is an arbitrary parameter that violates CP if ≠ 0 ; but it is constrained by t he neutron dipole moment to be ≤ 10-10 .Why so
small?
La Thuile, March 2005 Berta Beltrán 22
Axions : Phenomenology
The AXION is: pseudoscalar neutralpractically stablephenomenology
driven by the breaking scale fa and the specific axion model
Axion mass:
Axion-photon coupling present
in almost every axion model
This gives rise to the Primakoff effect: axion-
photon conversion (and vice versa) in
the presence of electromagnetic
fields.That is the only axion phenomenology on which CAST relies…