Searching for low mass dark matter via phonon creation in superfluid 4He. (arXiv:2005.08824v3 [hep-ph] UPDATED)
<a href="http://arxiv.org/find/hep-ph/1/au:+Baym_G/0/1/0/all/0/1">Gordon Baym</a>, <a href="http://arxiv.org/find/hep-ph/1/au:+Beck_D/0/1/0/all/0/1">D. H. Beck</a>, <a href="http://arxiv.org/find/hep-ph/1/au:+Filippini_J/0/1/0/all/0/1">Jeffrey P. Filippini</a>, <a href="http://arxiv.org/find/hep-ph/1/au:+Pethick_C/0/1/0/all/0/1">C. J. Pethick</a>, <a href="http://arxiv.org/find/hep-ph/1/au:+Shelton_J/0/1/0/all/0/1">Jessie Shelton</a>
We consider the scattering of dark matter particles from superfluid liquid
$^4$He, which has been proposed as a target for their direct detection.
Focusing on dark matter masses below ~1 MeV, we demonstrate from sum-rule
arguments the importance of the production of single phonons with energies
$omega lesssim 1$ meV. We show further that the anomalous dispersion of
phonons in liquid $^4$He at low pressures [i.e., $d^2omega(q)/dq^2>0$, where
$q$ and $omega(q)$ are the phonon momentum and energy] has the important
consequence that a single phonon will decay over a relatively short distance
into a shower of lower energy phonons centered on the direction of the original
phonon. Thus the experimental challenge in this regime is to detect a shower of
low energy phonons, not just a single phonon. Additional information from the
distribution of phonons in such a shower could enhance the determination of the
dark matter mass.
We consider the scattering of dark matter particles from superfluid liquid
$^4$He, which has been proposed as a target for their direct detection.
Focusing on dark matter masses below ~1 MeV, we demonstrate from sum-rule
arguments the importance of the production of single phonons with energies
$omega lesssim 1$ meV. We show further that the anomalous dispersion of
phonons in liquid $^4$He at low pressures [i.e., $d^2omega(q)/dq^2>0$, where
$q$ and $omega(q)$ are the phonon momentum and energy] has the important
consequence that a single phonon will decay over a relatively short distance
into a shower of lower energy phonons centered on the direction of the original
phonon. Thus the experimental challenge in this regime is to detect a shower of
low energy phonons, not just a single phonon. Additional information from the
distribution of phonons in such a shower could enhance the determination of the
dark matter mass.
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