Scintillation yield from electronic and nuclear recoils in superfluid $^4$He. (arXiv:2108.02176v2 [physics.ins-det] UPDATED)

Scintillation yield from electronic and nuclear recoils in superfluid $^4$He. (arXiv:2108.02176v2 [physics.ins-det] UPDATED)
<a href="http://arxiv.org/find/physics/1/au:+Collaboration_SPICE/HeRALD/0/1/0/all/0/1">SPICE/HeRALD Collaboration</a>: <a href="http://arxiv.org/find/physics/1/au:+Biekert_A/0/1/0/all/0/1">A. Biekert</a>, <a href="http://arxiv.org/find/physics/1/au:+Chang_C/0/1/0/all/0/1">C. Chang</a>, <a href="http://arxiv.org/find/physics/1/au:+Fink_C/0/1/0/all/0/1">C. W. Fink</a>, <a href="http://arxiv.org/find/physics/1/au:+Garcia_Sciveres_M/0/1/0/all/0/1">M. Garcia-Sciveres</a>, <a href="http://arxiv.org/find/physics/1/au:+Glazer_E/0/1/0/all/0/1">E. C. Glazer</a>, <a href="http://arxiv.org/find/physics/1/au:+Guo_W/0/1/0/all/0/1">W. Guo</a>, <a href="http://arxiv.org/find/physics/1/au:+Hertel_S/0/1/0/all/0/1">S. A. Hertel</a>, <a href="http://arxiv.org/find/physics/1/au:+Kravitz_S/0/1/0/all/0/1">S. Kravitz</a>, <a href="http://arxiv.org/find/physics/1/au:+Lin_J/0/1/0/all/0/1">J. Lin</a>, <a href="http://arxiv.org/find/physics/1/au:+Lisovenko_M/0/1/0/all/0/1">M. Lisovenko</a>, <a href="http://arxiv.org/find/physics/1/au:+Mahapatra_R/0/1/0/all/0/1">R. Mahapatra</a>, <a href="http://arxiv.org/find/physics/1/au:+McKinsey_D/0/1/0/all/0/1">D. N. McKinsey</a>, <a href="http://arxiv.org/find/physics/1/au:+Nguyen_J/0/1/0/all/0/1">J. S. Nguyen</a>, <a href="http://arxiv.org/find/physics/1/au:+Novosad_V/0/1/0/all/0/1">V. Novosad</a>, <a href="http://arxiv.org/find/physics/1/au:+Page_W/0/1/0/all/0/1">W. Page</a>, <a href="http://arxiv.org/find/physics/1/au:+Patel_P/0/1/0/all/0/1">P. K. Patel</a>, <a href="http://arxiv.org/find/physics/1/au:+Penning_B/0/1/0/all/0/1">B. Penning</a>, <a href="http://arxiv.org/find/physics/1/au:+Pinckney_H/0/1/0/all/0/1">H. D. Pinckney</a>, <a href="http://arxiv.org/find/physics/1/au:+Pyle_M/0/1/0/all/0/1">M. Pyle</a>, <a href="http://arxiv.org/find/physics/1/au:+Romani_R/0/1/0/all/0/1">R. K. Romani</a>, <a href="http://arxiv.org/find/physics/1/au:+Seilnacht_A/0/1/0/all/0/1">A. S. Seilnacht</a>, <a href="http://arxiv.org/find/physics/1/au:+Serafin_A/0/1/0/all/0/1">A. Serafin</a>, <a href="http://arxiv.org/find/physics/1/au:+Smith_R/0/1/0/all/0/1">R. J. Smith</a>, <a href="http://arxiv.org/find/physics/1/au:+Sorensen_P/0/1/0/all/0/1">P. Sorensen</a>, <a href="http://arxiv.org/find/physics/1/au:+Suerfu_B/0/1/0/all/0/1">B. Suerfu</a>, <a href="http://arxiv.org/find/physics/1/au:+Suzuki_A/0/1/0/all/0/1">A. Suzuki</a>, <a href="http://arxiv.org/find/physics/1/au:+Velan_V/0/1/0/all/0/1">V. Velan</a>, <a href="http://arxiv.org/find/physics/1/au:+Wang_G/0/1/0/all/0/1">G. Wang</a>, <a href="http://arxiv.org/find/physics/1/au:+Watkins_S/0/1/0/all/0/1">S. L. Watkins</a>, <a href="http://arxiv.org/find/physics/1/au:+Yefremenko_V/0/1/0/all/0/1">V. G. Yefremenko</a>, <a href="http://arxiv.org/find/physics/1/au:+Yuan_L/0/1/0/all/0/1">L. Yuan</a>, <a href="http://arxiv.org/find/physics/1/au:+Zhang_J/0/1/0/all/0/1">J. Zhang</a>

Superfluid $^4$He is a promising target material for direct detection of
light ($<$ 1 GeV) dark matter. Possible signal channels available for readout
in this medium include prompt photons, triplet excimers, and roton and phonon
quasiparticles. The relative yield of these signals has implications for the
sensitivity and discrimination power of a superfluid $^4$He dark matter
detector. Using a 16~cm$^3$ volume of 1.75~K superfluid $^4$He read out by six
immersed photomultiplier tubes, we measured the scintillation from electronic
recoils ranging between 36.3 and 185 keV$_mathrm{ee}$, yielding a mean signal
size of $1.25^{+0.03}_{-0.03}$~phe/keV$_mathrm{ee}$, and nuclear recoils from
53.2 to 1090 keV$_mathrm{nr}$. We compare the results of our relative
scintillation yield measurements to an existing semiempirical model based on
helium-helium and electron-helium interaction cross sections. We also study the
behavior of delayed scintillation components as a function of recoil type and
energy, a further avenue for signal discrimination in superfluid $^4$He.

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