New method of galactic axion
detection
M. Yoshimura
RIIS, Okayama University

m.yoshimura @axion workshop
20/12/2017

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Introduction: QCD-axion and its cosmology• PQ-symmetry solution to strong CP problem:the most compelling, leading to the axion• Cold dark matter, perhaps the most attractivein view of absence of SUSY signals in LHC• Galactic number density
comparable to BB photons of T= 10^4 K
m.yoshimura @axion workshop
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Ongoing and proposed experiments
Sikivie’s original idea
From CAST group paper• Axion haloscope has the highest sensitivity,
but time consuming experimentm.yoshimura @axion workshop
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Microscopic process of detection using atoms and molecules
MY and N. Sasao, arXiv:1710.11262
TRACA (Triggered Radiative Absorption of Cosmic Axion)
triggersignalm.yoshimura @axion workshop
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Interesting feature of probability amplitude

m.yoshimura @axion workshop
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3 enhancement factors• Ambient axions, giving enhanced coupling• Triggered photon number density• Macro-coherence amplification• Last two issues: verified by Okayama PSR
experiments of p-H_2
m.yoshimura @axion workshop
20/12/20176Induced two-photon coupling by galactic axion

m.yoshimura @axion workshop
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Rate amplification bymacroscopic coherence: an oversimplifed view
• Super-radiance coherent volume (Dicke)– In case of SR, coherent volume is proportional to λ2L.
– Phase decoherence time (T2) must be longer than TSR
NRate ∝ ∑ e


i k ⋅r j

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M atm ∝ N 2( for |r − r |≤ λ )jlj• For a process with plural outgoing particles (PSR, RENP etc)
Phase matching condition (momentum conservation) is satisfied.
Coherent volume is not limited by λ., can be macroscopic.
NRate ∝ ∑ ej

   i ( k 1 + k 2 + k 3 )⋅ r j

2M atm ∝ N

2(  for k 1 + k 2 + k 3 = 0

m.yoshimura @axion workshop
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Superradiance: 2 level and E1 photon case

Rate enhanced by N

Delayed enhanced signal
accompanied by ringing
m.yoshimura @axion workshop
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PSR ｅｘｐｅｒｉｍｅｎｔｓ at Okayama

m.yoshimura @axion workshop
20/12/2017

Courtesy of H. Hara10

HHm.yoshimura @axion workshop
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Our target choice for axion detection• p-H_2, since our group at Okayama has
experiences with this molecule, such as coherence
determination, PSR measurements both for gas
and solid.

m.yoshimura @axion workshop
20/12/201712For p-H_2

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Detection rates: work with N.Sasao
Revised from arXiv paperm.yoshimura @axion workshop
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Finite target size effectFormulais a useful guide,
but cannot be used for rate calculation

Cylinder of radius R, length L

m.yoshimura @axion workshop
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Excitation and trigger configuration
Energy and momentum
conservation uses as a guide

From the same direction

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Other possibilities: works in progress• Targets of smaller level spacing: Fine-structurelevels, HFS, molecular vibration (I_2 etc)
• Use of microwave or rf to get larger angularseparation from PSR background• T-odd, P-odd asymmetries for backgroundrejection
m.yoshimura @axion workshop20/12/201717

Summary• Proposed atomic/molecular experiments for galactic axion search• Detailed calculation for para-H_2 . Detectable rate withoutbackgrounds• Tunable for 10 umeV axion mass
• A wide parameter range search possible• Many interesting alternatives to be studied
m.yoshimura @axion workshop
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