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SUMMARY:Trobada: QUaerere AXion\, a proposal in a search for Galactic axio
 ns
DTSTART;VALUE=DATE-TIME:20150217T103000Z
DTEND;VALUE=DATE-TIME:20150217T113000Z
DTSTAMP;VALUE=DATE-TIME:20261012T132347Z
UID:indico-event-2431@indico.ific.uv.es
DESCRIPTION:\n    An outstanding result of the modern cosmology shows us t
 hat a significant fraction of the universe is made of dark matter. However
 \, the nature of such component is still unknown\, apart its gravitational
  interaction with ordinary barionic matter. A favored candidate for dark m
 atter is the axion: a new particle introduced by Peccei and Quinn to solve
  the strong CP problem\, i.e. the absence of CP violation in the strong in
 teraction sector of the Standard Model. Axions have properties similar to 
 a π0 particle and have mass ma inversely proportional to the Peccei-Quinn
  symmetry breaking scale fa. For certain ranges of fa and ma (typically wi
 th masses ranging from μeV to meV)\, large quantities of axions may had b
 een produced in the early universe that could be able to account for a lar
 ge portion of the cold dark matter forming today galactic halos. Axions ha
 ve extremely small coupling to normal matter and radiation\, but they can 
 be converted into detectable photons by means of the inverse Primakoff eff
 ect as shown by Sikivie. The idea of Sikivie has been exploited by the ame
 rican experiment ADMX. This experiment is still running\, and for the mome
 nt it has been capable of searching for cosmological axions in the few μe
 V mass range. The QUAX (QUaerere AXion) proposal explores in details the i
 deas of Krauss\, Barbieri et al and Kolokolov and Vorobyev. These authors 
 proposed to study the interaction of the cosmological axion with the spin 
 of fermions (electrons or nucleons). In fact\, due to the motion of the So
 lar System through the galactic halo\, the Earth is effectively moving thr
 ough the cold dark matter cloud surrounding the Galaxy and an observer on 
 Earth will see such axions as a wind. In particular\, the effect of the ax
 ion wind on a magnetized material can be described as an effective oscilla
 ting magnetic field with frequency determined by ma\, and strength related
  to fa. Thus\, a possible detector for the axion wind can be a magnetized 
 sample with Larmor resonance frequency tuned to the axion mass by means of
  an external polarizing static field (e.g. 0.6 T for 17 GHz\, correspondin
 g to a 70 μeV axion mass). The interaction with the axion effective field
  will drive the total magnetization of the sample\, and so producing oscil
 lations in the magnetization that\, in principle\, can be detected. In ord
 er to optimize the detection\, the sample is placed inside a microwave cav
 ity and a pump rf field is applied in a direction orthogonal to the polari
 zing field in order to amplify the equivalent rf field generated by the ax
 ion wind. The induced change in the magnetic flux along the polarizing fie
 ld is then fed to a SQUID magnetometer through a superconducting transform
 er. It is worth noticing that the magnetized sample must be cooled to ultr
 a-cryogenic temperature to avoid fluctuations of the magnetization due to 
 the thermal bath. The QUAX project will try to exploit this detection sche
 me\, starting at a precise value of the axion mass (around 70 μeV). Other
  possible detection schemes will be shortly presented covering also other 
 possible type of interactions.\n\nhttps://indico.ific.uv.es/event/2431/
LOCATION:IFIC Seminar Room\, 1.1.1
URL:https://indico.ific.uv.es/event/2431/
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