page_title: Axion Dark Matter Experiment
section_title: Strong CP problem
hierarchical_section_title: Axion Dark Matter Experiment / Background / Strong CP problem
caption_attribution_description: English: Composite image showing the galaxy cluster 1E 0657-56, better known as bullet cluster. The image in background showing the visible spectrum of light stems from Magellan and Hubble Space Telescope images. The pink overlay shows the x-ray emission (recorded by Chandra Telescope) of the colliding clusters, the blue one represents the mass distribution of the clusters calculated from gravitational lens effects. Scale: Full image is 7.5 arcmin wide, 5.4 arcmin high Deutsch: Montage aus verschiedenen Bildern des Galaxieclusters 1E 0657-56, besser bekannt als Bullet-Cluster. Das Hintergrundbild zeigt eine Aufnahme des sichtbaren Spektrums, das vom Magellan-Teleskop und dem Hubble-Weltraumteleskop aufgenommen wurde. Darüber liegt in pink die vom Chandra-Teleskop aufgenommene Röntgenstrahlung, die vom Cluster ausgeht und in blau die Massenverteilung im Cluster, die aus Gravitationslinseneffekten berechnet wurde. Français&#160;: Image composite montrant l'amas de galaxies 1E 0657-56, aussi connu sous le nom d'amas du Boulet. Cette image montre en arrière-plan des images de galaxies qui proviennent des télescopes Hubble et Magellan. Le revêtement en rose montre les émissions de rayons-x (enregistrées par le télescope Chandra) de la collision des deux amas, alors que les émissions en bleu représentent la distribution de la masse de ces amas, calculée à partir de l'effet de lentille gravitationnelle.
context_page_description: The Axion Dark Matter Experiment uses a resonant microwave cavity within a large superconducting magnet to search for cold dark matter axions in the local galactic dark matter halo. Unusual for a dark matter detector, it is not located deep underground. Sited at the Center for Experimental Nuclear Physics and Astrophysics at the University of Washington, ADMX is a large collaborative effort with researchers from universities and laboratories around the world.
context_section_description: The axion was originally postulated to exist as part of the solution to the "strong CP problem". This problem arose from the observation that the strong force holding nuclei together and the weak force making nuclei decay differ in the amount of CP violation in their interactions. Weak interaction was expected to feed into the strong interactions (QCD), yielding appreciable QCD CP violation, but no such violation has been observed to very high accuracy. One solution to this Strong CP Problem ends up introducing a new particle called the axion. If the axion is very light, it interacts so weakly that it would be nearly impossible to detect but would be an ideal dark matter candidate. The ADMX experiment aims to detect this extraordinarily weakly coupled particle.
caption: The Bullet Cluster: HST image with overlays. The total projected mass distribution reconstructed from strong and weak gravitational lensing is shown in blue, while the X-ray emitting hot gas observed with Chandra is shown in red.
exif: {"Image ImageDescription": "This composite image shows the galaxy cluster 1E 0657-56, also known as the\n\"bullet cluster\", formed after the collision of two large clusters of\ngalaxies.  Hot gas detected by Chandra is seen as two pink clumps in the\nimage and contains most of the \"normal\" matter in the two clusters.  An\noptical image from Magellan and the Hubble Space Telescope shows galaxies\nin orange and white. The blue clumps show where most of the mass in the\nclusters is found, using a technique known as gravitational lensing.  Most\nof the matter in the clusters (blue) is clearly separate from the normal\nmatter (pink), giving direct evidence that nearly all of the matter in the\nclusters is dark.  This result cannot be explained by modifying the laws of\ngravity.", "Image XResolution": "240", "Image YResolution": "240", "Image ResolutionUnit": "Pixels/Inch", "Image Software": "Adobe Photoshop Lightroom 3.6 (Windows)", "Image DateTime": "2013:05:24 15:17:12", "Image Artist": "Chandra X-ray Observatory Center", "Image ExifOffset": "966", "Thumbnail Compression": "JPEG (old-style)", "Thumbnail XResolution": "72", "Thumbnail YResolution": "72", "Thumbnail ResolutionUnit": "Pixels/Inch", "Thumbnail JPEGInterchangeFormat": "1110", "Thumbnail JPEGInterchangeFormatLength": "23752", "EXIF ExifVersion": "0230", "EXIF DateTimeDigitized": "2006:09:20 11:53:10"}