R. Agnese, A. J. Anderson, D. Balakishiyeva, R. Basu Thakur, D. A. Bauer, J. Billard, A. Borgland, M. A. Bowles, D. Brandt, P. L. Brink, R. Bunker, B. Cabrera, D. O. Caldwell, D. G. Cerdeno, H. Chagani, Y. Chen, J. Cooley, B. Cornell, C. H. Crewdson, P. Cushman, M. Daal, P. C. F. Di Stefano, T. Doughty, L. Esteban, S. Fallows, E. Figueroa-Feliciano, G. L. Godfrey, S. R. Golwala, J. Hall, H. R. Harris, S. A. Hertel, T. Hofer, D. Holmgren, L. Hsu, M. E. Huber, A. Jastram, O. Kamaev, B. Kara, M. H. Kelsey, A. Kennedy, M. Kiveni, K. Koch, A. Leder, B. Loer, E. Lopez Asamar, R. Mahapatra, V. Mandic, C. Martinez, K. A. McCarthy, N. Mirabolfathi, R. A. Moffatt, D. C. Moore, H. Nelson, R. H. Nelson, R. W. Ogburn, K. Page, W. A. Page, R. Partridge, M. Pepin, A. Phipps, K. Prasad, M. Pyle, H. Qiu, W. Rau, P. Redl, A. Reisetter, Y. Ricci, H. E. Rogers, T. Saab, B. Sadoulet, J. Sander, K. Schneck, R. W. Schnee, S. Scorza, B. Serfass, B. Shank, D. Speller, S. Upadhyayula, A. N. Villano, B. Welliver, D. H. Wright, S. Yellin, J. J. Yen, B. A. Young, J. Zhang
While the Standard Model of particle physics does not include free particles with fractional charge, experimental searches have not ruled out their existence. We report results from the Cryogenic Dark Matter Search (CDMS II) experiment that give the first direct-detection limits for cosmogenically-produced relativistic particles with electric charge lower than $e$/6. A search for tracks in the six stacked detectors of each of two of the CDMS II towers found no candidates, thereby excluding new parameter space for particles with electric charges between $e$/6 and $e$/200.
SuperCDMS Collaboration, R. Agnese, T. Aralis, T. Aramaki, I. J. Arnquist, E. Azadbakht, W. Baker, S. Banik, D. Barker, D. A. Bauer, T. Binder, M. A. Bowles, P. L. Brink, R. Bunker, B. Cabrera, R. Calkins, R. A. Cameron, C. Cartaro, D. G. Cerdeño, Y. -Y. Chang, J. Cooley, B. Cornell, P. Cushman, F. De Brienne, T. Doughty, E. Fascione, E. Figueroa-Feliciano, C. W. Fink, M. Fritts, G. Gerbier, R. Germond, M. Ghaith, S. R. Golwala, H. R. Harris, N. Herbert, Z. Hong, E. W. Hoppe, L. Hsu, M. E. Huber, V. Iyer, D. Jardin, A. Jastram, C. Jena, M. H. Kelsey, A. Kennedy, A. Kubik, N. A. Kurinsky, R. E. Lawrence, B. Loer, E. Lopez Asamar, P. Lukens, D. MacDonell, R. Mahapatra, V. Mandic, N. Mast, E. Miller, N. Mirabolfathi, B. Mohanty, J. D. Morales Mendoza, J. Nelson, H. Neog, J. L. Orrell, S. M. Oser, W. A. Page, R. Partridge, M. Pepin, F. Ponce, S. Poudel, M. Pyle, H. Qiu, W. Rau, A. Reisetter, R. Ren, T. Reynolds, A. Roberts, A. E. Robinson, H. E. Rogers, T. Saab, B. Sadoulet, J. Sander, A. Scarff, R. W. Schnee, S. Scorza, K. Senapati, B. Serfass, D. Speller, C. Stanford, M. Stein, J. Street, H. A. Tanaka, D. Toback, R. Underwood, A. N. Villano, B. von Krosigk, S. L. Watkins, J. S. Wilson, M. J. Wilson, J. Winchell, D. H. Wright, S. Yellin, B. A. Young, X. Zhang, X. Zhao
Aug 28, 2018·astro-ph.CO·PDF The Cryogenic Dark Matter Search low ionization threshold experiment (CDMSlite) searches for interactions between dark matter particles and germanium nuclei in cryogenic detectors. The experiment has achieved a low energy threshold with improved sensitivity to low-mass (<10 GeV/c$^2$) dark matter particles. We present an analysis of the final CDMSlite data set, taken with a different detector than was used for the two previous CDMSlite data sets. This analysis includes a data "salting" method to protect against bias, improved noise discrimination, background modeling, and the use of profile likelihood methods to search for a dark matter signal in the presence of backgrounds. We achieve an energy threshold of 70 eV and significantly improve the sensitivity for dark matter particles with masses between 2.5 and 10 GeV/c$^2$ compared to previous analyses. We set an upper limit on the dark matter-nucleon scattering cross section in germanium of 5.4$\times$10$^{-42}$ cm$^2$ at 5 GeV/c$^2$, a factor of $\sim$2.5 improvement over the previous CDMSlite result.
SuperCDMS Collaboration, R. Agnese, T. Aralis, T. Aramaki, I. J. Arnquist, E. Azadbakht, W. Baker, D. Barker, D. A. Bauer, T. Binder, M. A. Bowles, P. L. Brink, R. Bunker, B. Cabrera, R. Calkins, C. Cartaro, D. G. Cerdeño, Y. -Y. Chang, J. Cooley, B. Cornell, P. Cushman, T. Doughty, E. Fascione, E. Figueroa-Feliciano, C. W. Fink, M. Fritts, G. Gerbier, R. Germond, M. Ghaith, S. R. Golwal, H. R. Harris, Z. Hong, E. W. Hoppe, L. Hsu, M. E. Huber, V. Iyer, D. Jardin, A. Jastram, C. Jena, M. H. Kelsey, A. Kennedy, A. Kubik, N. A. Kurinsky, R. E. Lawrence, B. Loer, E. Lopez Asamar, P. Lukens, D. MacDonell, R. Mahapatra, V. Mandic, N. Mast, E. Miller, N. Mirabolfathi, B. Mohanty, J. D. Morales Mendoza, J. Nelson, J. L. Orrell, S. M. Oser, W. A. Page, R. Partridge, M. Pepin, F. Ponce, S. Poudel, M. Pyle, H. Qiu, W. Rau, A. Reisetter, R. Ren, T. Reynolds, A. Roberts, A. E. Robinson, H. E. Rogers, T. Saab, B. Sadoulet, S. Banik, J. Sander, A. Scarff, R. W. Schnee, S. Scorza, K. Senapati, B. Serfass, D. Speller, M. Stein, J. Street, H. A. Tanaka, D. Toback, R. Underwood, A. N. Villano, B. von Krosigk, S. L. Watkins, J. S. Wilson, M. J. Wilson, J. Winchell, D. H. Wright, S. Yellin, B. A. Young, X. Zhang, X. Zhao
Future direct searches for low-mass dark matter particles with germanium detectors, such as SuperCDMS SNOLAB, are expected to be limited by backgrounds from radioactive isotopes activated by cosmogenic radiation inside the germanium. There are limited experimental data available to constrain production rates and a large spread of theoretical predictions. We examine the calculation of expected production rates, and analyze data from the second run of the CDMS low ionization threshold experiment (CDMSlite) to estimate the rates for several isotopes. We model the measured CDMSlite spectrum and fit for contributions from tritium and other isotopes. Using the knowledge of the detector history, these results are converted to cosmogenic production rates at sea level. The production rates in atoms/(kg$\cdot$day) are 74$\pm$9 for $^3$H, 1.5$\pm$0.7 for $^{55}$Fe, 17$\pm$5 for $^{65}$Zn, and 30$\pm$18 for $^{68}$Ge.
SuperCDMS Collaboration, R. Agnese, T. Aramaki, I. J. Arnquist, W. Baker, D. Balakishiyeva, S. Banik, D. Barker, R. Basu Thakur, D. A. Bauer, T. Binder, M. A. Bowles, P. L. Brink, R. Bunker, B. Cabrera, D. O. Caldwell, R. Calkins, C. Cartaro, D. G. Cerdeño, Y. Chang, Y. Chen, J. Cooley, B. Cornell, P. Cushman, M. Daal, P. C. F. Di Stefano, T. Doughty, E. Fascione, E. Figueroa-Feliciano, M. Fritts, G. Gerbier, R. Germond, M. Ghaith, G. L. Godfrey, S. R. Golwala, J. Hall, H. R. Harris, Z. Hong, E. W. Hoppe, L. Hsu, M. E. Huber, V. Iyer, D. Jardin, A. Jastram, C. Jena, M. H. Kelsey, A. Kennedy, A. Kubik, N. A. Kurinsky, B. Loer, E. Lopez Asamar, P. Lukens, D. MacDonell, R. Mahapatra, V. Mandic, N. Mast, E. H. Miller, N. Mirabolfathi, B. Mohanty, J. D. Morales Mendoza, J. Nelson, J. L. Orrell, S. M. Oser, K. Page, W. A. Page, R. Partridge, M. Penalver Martinez, M. Pepin, A. Phipps, S. Poudel, M. Pyle, H. Qiu, W. Rau, P. Redl, A. Reisetter, T. Reynolds, A. Roberts, A. E. Robinson, H. E. Rogers, T. Saab, B. Sadoulet, J. Sander, K. Schneck, R. W. Schnee, S. Scorza, K. Senapati, B. Serfass, D. Speller, M. Stein, J. Street, H. A. Tanaka, D. Toback, R. Underwood, A. N. Villano, B. von Krosigk, B. Welliver, J. S. Wilson, M. J. Wilson, D. H. Wright, S. Yellin, J. J. Yen, B. A. Young, X. Zhang, X. Zhao
We report the result of a blinded search for Weakly Interacting Massive Particles (WIMPs) using the majority of the SuperCDMS Soudan dataset. With an exposure of 1690 kg days, a single candidate event is observed, consistent with expected backgrounds. This analysis (combined with previous Ge results) sets an upper limit on the spin-independent WIMP--nucleon cross section of $1.4 \times 10^{-44}$ ($1.0 \times 10^{-44}$) cm$^2$ at 46 GeV/$c^2$. These results set the strongest limits for WIMP--germanium-nucleus interactions for masses $>$12 GeV/$c^2$.
SuperCDMS Collaboration, R. Agnese, A. J. Anderson, T. Aralis, T. Aramaki, I. J. Arnquist, W. Baker, D. Balakishiyeva, D. Barker, R. Basu Thakur, D. A. Bauer, T. Binder, M. A. Bowles, P. L. Brink, R. Bunker, B. Cabrera, D. O. Caldwell, R. Calkins, C. Cartaro, D. G. Cerdeno, Y. Chang, H. Chagani, Y. Chen, J. Cooley, B. Cornell, P. Cushman, M. Daal, P. C. F. Di Stefano, T. Doughty, L. Esteban, E. Fascione, E. Figueroa-Feliciano, M. Fritts, G. Gerbier, M. Ghaith, G. L. Godfrey, S. R. Golwala, J. Hall, H. R. Harris, Z. Hong, E. W. Hoppe, L. Hsu, M. E. Huber, V. Iyer, D. Jardin, A. Jastram, C. Jena, M. H. Kelsey, A. Kennedy, A. Kubik, N. A. Kurinsky, A. Leder, B. Loer, E. Lopez Asamar, P. Lukens, D. MacDonell, R. Mahapatra, V. Mandic, N. Mast, E. H. Miller, N. Mirabolfathi, R. A. Moffatt, B. Mohanty, J. D. Morales Mendoza, J. Nelson, J. L. Orrell, S. M. Oser, K. Page, W. A. Page, R. Partridge, M. Pepin, M. Penalver Martinez, A. Phipps, S. Poudel, M. Pyle, H. Qiu, W. Rau, P. Redl, A. Reisetter, T. Reynolds, A. Roberts, A. E. Robinson, H. E. Rogers, T. Saab, B. Sadoulet, J. Sander, K. Schneck, R. W. Schnee, S. Scorza, K. Senapati, B. Serfass, D. Speller, M. Stein, J. Street, H. A. Tanaka, D. Toback, R. Underwood, A. N. Villano, B. von Krosigk, B. Welliver, J. S. Wilson, M. J Wilson, D. H. Wright, S. Yellin, J. J. Yen, B. A. Young, X. Zhang, X. Zhao
The SuperCDMS experiment is designed to directly detect weakly interacting massive particles (WIMPs) that may constitute the dark matter in our Galaxy. During its operation at the Soudan Underground Laboratory, germanium detectors were run in the CDMSlite mode to gather data sets with sensitivity specifically for WIMPs with masses ${<}$10 GeV/$c^2$. In this mode, a higher detector-bias voltage is applied to amplify the phonon signals produced by drifting charges. This paper presents studies of the experimental noise and its effect on the achievable energy threshold, which is demonstrated to be as low as 56 eV$_{\text{ee}}$ (electron equivalent energy). The detector-biasing configuration is described in detail, with analysis corrections for voltage variations to the level of a few percent. Detailed studies of the electric-field geometry, and the resulting successful development of a fiducial parameter, eliminate poorly measured events, yielding an energy resolution ranging from ${\sim}$9 eV$_{\text{ee}}$ at 0 keV to 101 eV$_{\text{ee}}$ at ${\sim}$10 eV$_{\text{ee}}$. New results are derived for astrophysical uncertainties relevant to the WIMP-search limits, specifically examining how they are affected by variations in the most probable WIMP velocity and the Galactic escape velocity. These variations become more important for WIMP masses below 10 GeV/$c^2$. Finally, new limits on spin-dependent low-mass WIMP-nucleon interactions are derived, with new parameter space excluded for WIMP masses $\lesssim$3 GeV/$c^2$
I. Alkhatib, D. W. P. Amaral, T. Aralis, T. Aramaki, I. J. Arnquist, I. Ataee Langroudy, E. Azadbakht, S. Banik, D. Barker, C. Bathurst, D. A. Bauer, L. V. S. Bezerra, R. Bhattacharyya, T. Binder, M. A. Bowles, P. L. Brink, R. Bunker, B. Cabrera, R. Calkins, R. A. Cameron, C. Cartaro, D. G. Cerdeño, Y. -Y. Chang, M. Chaudhuri, R. Chen, N. Chott, J. Cooley, H. Coombes, J. Corbett, P. Cushman, F. De Brienne, M. L. di Vacri, M. D. Diamond, E. Fascione, E. Figueroa-Feliciano, C. W. Fink, K. Fouts, M. Fritts, G. Gerbier, R. Germond, M. Ghaith, S. R. Golwala, H. R. Harris, N. Herbert, B. A. Hines, M. I. Hollister, Z. Hong, E. W. Hoppe, L. Hsu, M. E. Huber, V. Iyer, D. Jardin, A. Jastram, V. K. S. Kashyap, M. H. Kelsey, A. Kubik, N. A. Kurinsky, R. E. Lawrence, A. Li, B. Loer, E. Lopez Asamar, P. Lukens, D. MacDonell, D. B. MacFarlane, R. Mahapatra, V. Mandic, N. Mast, A. J. Mayer, H. Meyer zu Theenhausen, É. M. Michaud, E. Michielin, N. Mirabolfathi, B. Mohanty, J. D. Morales Mendoza, S. Nagorny, J. Nelson, H. Neog, V. Novati, J. L. Orrell, S. M. Oser, W. A. Page, P. Pakarha, R. Partridge, R. Podviianiuk, F. Ponce, S. Poudel, M. Pyle, W. Rau, E. Reid, R. Ren, T. Reynolds, A. Roberts, A. E. Robinson, T. Saab, B. Sadoulet, J. Sander, A. Sattari, R. W. Schnee, S. Scorza, B. Serfass, D. J. Sincavage, C. Stanford, J. Street, D. Toback, R. Underwood, S. Verma, A. N. Villano, B. von Krosigk, S. L. Watkins, L. Wills, J. S. Wilson, M. J. Wilson, J. Winchell, D. H. Wright, S. Yellin, B. A. Young, T. C. Yu, E. Zhang, H. G. Zhang, X. Zhao, L. Zheng, J. Camilleri, Yu. G. Kolomensky, S. Zuber
We present limits on spin-independent dark matter-nucleon interactions using a $10.6$ $\mathrm{g}$ Si athermal phonon detector with a baseline energy resolution of $σ_E=3.86 \pm 0.04$ $(\mathrm{stat.})^{+0.19}_{-0.00}$ $(\mathrm{syst.})$ $\mathrm{eV}$. This exclusion analysis sets the most stringent dark matter-nucleon scattering cross-section limits achieved by a cryogenic detector for dark matter particle masses from $93$ to $140$ $\mathrm{MeV}/c^2$, with a raw exposure of $9.9$ $\mathrm{g}\cdot\mathrm{d}$ acquired at an above-ground facility. This work illustrates the scientific potential of detectors with athermal phonon sensors with eV-scale energy resolution for future dark matter searches.
A. N. Villano, P. Stoler, P. E. Bosted, S. H. Connell, M. M. Dalton, M. K. Jones, V. Kubarovsky, G. S Adams, A. Ahmidouch, J. Arrington, R. Asaturyan, O. K. Baker, H. Breuer, M. E. Christy, S. Danagoulian, D. Day, J. A. Dunne, D. Dutta, R. Ent, H. C. Fenker, V. V. Frolov, L. Gan, D. Gaskell, W. Hinton, R. J. Holt, T. Horn, G. M. Huber, K. Joo, N. Kalantarians, C. E. Keppel, Y. Li, A. Lung, D. Mack, S. Malace, P. Markowitz, D. G. Meekins, H. Mkrtchyan, J. Napolitano, G. Niculescu, I. Niculescu, D. H. Potterveld, Paul E. Reimer, J. Reinhold, J. Roche, S. E. Rock, G. R. Smith, S. Stepanyan, V. Tadevosyan, V. Tvaskis, M. Ungaro, A. Uzzle, S. Vidakovic, F. R. Wesselmann, B. Wojtsekhowski, S. A. Wood, L. Yuan, X. Zheng, H. Zhu
The process $ep \to e^{\prime}p^{\prime}π^0$ has been measured at $Q^2$ = 6.4 and 7.7 GeV/c$^2$)$^2$ in Jefferson Lab's Hall C. Unpolarized differential cross sections are reported in the virtual photon-proton center of mass frame considering the process $γ^{\ast}p \to p^{\prime}π^0$. Various details relating to the background subtractions, radiative corrections and systematic errors are discussed. The usefulness of the data with regard to the measurement of the electromagnetic properties of the well known $Δ(1232)$ resonance is covered in detail. Specifically considered are the electromagnetic and scalar-magnetic ratios $R_{EM}$ and $R_{SM}$ along with the magnetic transition form factor $G_M^{\ast}$. It is found that the rapid fall off of the $Δ(1232)$ contribution continues into this region of momentum transfer and that other resonances
A. J. Biffl, A. Gevorgian, K. Harris, A. N. Villano
Nuclear reactors represent a promising neutrino source for CE$ν$NS (coherent-elastic neutrino-nucleus scattering) searches. However, reactor sites also come with high ambient neutron flux. Neutron capture-induced nuclear recoils can create a spectrum that strongly overlaps the CE$ν$NS signal for recoils $\lesssim$\,100\,eV for nuclear reactor measurements in silicon or germanium detectors. This background can be particularly critical for low-power research reactors providing a moderate neutrino flux. In this work we quantify the impact of this background and show that, for a measurement 10\,m from a 1\,MW reactor, the effective thermal neutron flux should be kept below $\sim$~7$\times$~10$^{-4}$\,n/cm$^2$s so that the CE$ν$NS events can be measured at least at a 5$σ$ level with germanium detectors in 100~kg\,yr exposure time. This flux corresponds to 60\% of the sea-level flux but needs to be achieved in a nominally high-flux (reactor) environment. Improved detector resolution can help the measurements, but the thermal flux is the key parameter for the sensitivity of the experiment. For silicon detectors, the constraint is even stronger and thermal neutron fluxes must be near an order of magnitude lower. This constraint highlights the need of an effective thermal neutron mitigation strategy for future low threshold CE$ν$NS searches. In particular, the neutron capture-induced background can be efficiently reduced by active veto systems tagging the deexcitation gamma following the capture.
R. Agnese, A. J. Anderson, M. Asai, D. Balakishiyeva, D. Barker, R. Basu Thakur, D. A. Bauer, J. Billard, A. Borgland, M. A. Bowles, D. Brandt, P. L. Brink, R. Bunker, B. Cabrera, D. O. Caldwell, R. Calkins, D. G. Cerdeño, H. Chagani, Y. Chen, J. Cooley, B. Cornell, C. H. Crewdson, P. Cushman, M. Daal, P. C. F. Di Stefano, T. Doughty, L. Esteban, S. Fallows, E. Figueroa-Feliciano, G. L. Godfrey, S. R. Golwala, J. Hall, H. R. Harris, S. A. Hertel, T. Hofer, D. Holmgren, L. Hsu, M. E. Huber, D. Jardin, A. Jastram, O. Kamaev, B. Kara, M. H. Kelsey, A. Kennedy, M. Kiveni, K. Koch, A. Leder, B. Loer, E. Lopez Asamar, P. Lukens, R. Mahapatra, V. Mandic, K. A. McCarthy, N. Mirabolfathi, R. A. Moffatt, S. M. Oser, K. Page, W. A. Page, R. Partridge, M. Pepin, A. Phipps, K. Prasad, M. Pyle, H. Qiu, W. Rau, P. Redl, A. Reisetter, Y. Ricci, H. E. Rogers, T. Saab, B. Sadoulet, J. Sander, K. Schneck, R. W. Schnee, S. Scorza, B. Serfass, B. Shank, D. Speller, D. Toback, S. Upadhyayula, A. N. Villano, B. Welliver, J. S. Wilson, D. H. Wright, X. Yang, S. Yellin, J. J. Yen, B. A. Young, J. Zhang
CDMS II data from the 5-tower runs at the Soudan Underground Laboratory were reprocessed with an improved charge-pulse fitting algorithm. Two new analysis techniques to reject surface-event backgrounds were applied to the 612 kg days germanium-detector WIMP-search exposure. An extended analysis was also completed by decreasing the 10 keV analysis threshold to $\sim$5 keV, to increase sensitivity near a WIMP mass of 8 GeV/$c^2$. After unblinding, there were zero candidate events above a deposited energy of 10 keV and 6 events in the lower-threshold analysis. This yielded minimum WIMP-nucleon spin-independent scattering cross-section limits of $1.8 \times 10^{-44}$ and $1.18 \times 10 ^{-41}$ cm$^2$ at 90\% confidence for 60 and 8.6 GeV/$c^2$ WIMPs, respectively. This improves the previous CDMS II result by a factor of 2.4 (2.7) for 60 (8.6) GeV/$c^2$ WIMPs.
K. Schneck, B. Cabrera, D. G. Cerdeno, V. Mandic, H. E. Rogers, R. Agnese, A. J. Anderson, M. Asai, D. Balakishiyeva, D. Barker, R. Basu Thakur, D. A. Bauer, J. Billard, A. Borgland, D. Brandt, P. L. Brink, R. Bunker, D. O. Caldwell, R. Calkins, H. Chagani, Y. Chen, J. Cooley, B. Cornell, C. H. Crewdson, P. Cushman, M. Daal, P. C. F. Di Stefano, T. Doughty, L. Esteban, S. Fallows, E. Figueroa-Feliciano, G. L. Godfrey, S. R. Golwala, J. Hall, H. R. Harris, T. Hofer, D. Holmgren, L. Hsu, M. E. Huber, D. M. Jardin, A. Jastram, O. Kamaev, B. Kara, M. H. Kelsey, A. Kennedy, A. Leder, B. Loer, E. Lopez Asamar, P. Lukens, R. Mahapatra, K. A. McCarthy, N. Mirabolfathi, R. A. Moffatt, J. D. Morales Mendoza, S. M. Oser, K. Page, W. A. Page, R. Partridge, M. Pepin, A. Phipps, K. Prasad, M. Pyle, H. Qiu, W. Rau, P. Redl, A. Reisetter, Y. Ricci, A. Roberts, T. Saab, B. Sadoulet, J. Sander, R. W. Schnee, S. Scorza, B. Serfass, B. Shank, D. Speller, D. Toback, S. Upadhyayula, A. N. Villano, B. Welliver, J. S. Wilson, D. H. Wright, X. Yang, S. Yellin, J. J. Yen, B. A. Young, J. Zhang
Mar 11, 2015·astro-ph.CO·PDF We examine the consequences of the effective field theory (EFT) of dark matter-nucleon scattering for current and proposed direct detection experiments. Exclusion limits on EFT coupling constants computed using the optimum interval method are presented for SuperCDMS Soudan, CDMS II, and LUX, and the necessity of combining results from multiple experiments in order to determine dark matter parameters is discussed. We demonstrate that spectral differences between the standard dark matter model and a general EFT interaction can produce a bias when calculating exclusion limits and when developing signal models for likelihood and machine learning techniques. We also discuss the implications of the EFT for the next-generation (G2) direct detection experiments and point out regions of complementarity in the EFT parameter space.
SuperCDMS Collaboration, M. F. Albakry, I. Alkhatib, D. Alonso-González, D. W. P. Amaral, J. Anczarski, T. Aralis, T. Aramaki, I. J. Arnquist, I. Ataee Langroudy, E. Azadbakht, C. Bathurst, R. Bhattacharyya, A. J. Biffl, P. L. Brink, M. Buchanan, R. Bunker, B. Cabrera, R. Calkins, R. A. Cameron, C. Cartaro, D. G. Cerdeño, Y. -Y. Chang, M. Chaudhuri, J. -H. Chen, R. Chen, N. Chott, J. Cooley, H. Coombes, P. Cushman, R. Cyna, S. Das, F. De Brienne, S. Dharani, M. L. di Vacri, M. D. Diamond, M. Elwan, E. Fascione, E. Figueroa-Feliciano, K. Fouts, M. Fritts, R. Germond, M. Ghaith, S. R. Golwala, J. Hall, S. A. S. Harms, K. Harris, N. Hassan, Z. Hong, E. W. Hoppe, L. Hsu, M. E. Huber, V. Iyer, D. Jardin, V. K. S. Kashyap, S. T. D. Keller, M. H. Kelsey, K. T. Kennard, A. Kubik, N. A. Kurinsky, M. Lee, J. Leyva, J. Liu, Y. Liu, B. Loer, E. Lopez Asamar, P. Lukens, D. B. MacFarlane, R. Mahapatra, J. S. Mammo, N. Mast, A. J. Mayer, H. Meyer zu Theenhausen, É. Michaud, E. Michielin, N. Mirabolfathi, M. Mirzakhani, B. Mohanty, D. Monteiro, J. Nelson, H. Neog, V. Novati, J. L. Orrell, M. D. Osborne, S. M. Oser, L. Pandey, S. Pandey, R. Partridge, D. S. Pedreros, W. Peng, L. Perna, W. L. Perry, R. Podviianiuk, S. S. Poudel, A. Pradeep, M. Pyle, W. Rau, E. Reid, R. Ren, T. Reynolds, M. Rios, A. Roberts, A. E. Robinson, J. L. Ryan, T. Saab, D. Sadek, B. Sadoulet, S. P. Sahoo, I. Saikia, J. Sander, A. Sattari, B. Schmidt, R. W. Schnee, S. Scorza, B. Serfass, A. Simchony, D. J. Sincavage, P. Sinervo, J. Street, H. Sun, E. Tanner, G. D. Terry, D. Toback, S. Verma, A. N. Villano, B. von Krosigk, S. L. Watkins, O. Wen, Z. Williams, M. J. Wilson, J. Winchell, K. Wykoff, S. Yellin, B. A. Young, T. C. Yu, B. Zatschler, S. Zatschler, A. Zaytsev, E. Zhang, L. Zheng, A. Zuniga, M. J. Zurowski
This article presents constraints on dark-matter-electron interactions obtained from the first underground data-taking campaign with multiple SuperCDMS HVeV detectors operated in the same housing. An exposure of 7.63 g-days is used to set upper limits on the dark-matter-electron scattering cross section for dark matter masses between 0.5 and 1000 MeV/$c^2$, as well as upper limits on dark photon kinetic mixing and axion-like particle axioelectric coupling for masses between 1.2 and 23.3 eV/$c^2$. Compared to an earlier HVeV search, sensitivity was improved as a result of an increased overburden of 225 meters of water equivalent, an anticoincidence event selection, and better pile-up rejection. In the case of dark-matter-electron scattering via a heavy mediator, an improvement by up to a factor of 25 in cross-section sensitivity was achieved.
SuperCDMS Collaboration, R. Agnese, T. Aralis, T. Aramaki, I. J. Arnquist, E. Azadbakht, W. Baker, S. Banik, D. Barker, D. A. Bauer, T. Binder, M. A. Bowles, P. L. Brink, R. Bunker, B. Cabrera, R. Calkins, C. Cartaro, D. G. Cerdeno, Y. -Y. Chang, J. Cooley, B. Cornell, P. Cushman, P. C. F. Di Stefano, T. Doughty, E. Fascione, E. Figueroa-Feliciano, C. Fink, M. Fritts, G. Gerbier, R. Germond, M. Ghaith, S. R. Golwala, H. R. Harris, Z. Hong, E. W. Hoppe, L. Hsu, M. E. Huber, V. Iyer, D. Jardin, C. Jena, M. H. Kelsey, A. Kennedy, A. Kubik, N. A. Kurinsky, R. E. Lawrence, J. V. Leyva, B. Loer, E. Lopez Asamar, P. Lukens, D. MacDonell, R. Mahapatra, V. Mandic, N. Mast, E. H. Miller, N. Mirabolfathi, B. Mohanty, J. D. Morales Mendoza, J. Nelson, J. L. Orrell, S. M. Oser, W. A. Page, R. Partridge, M. Pepin, A. Phipps, F. Ponce, S. Poudel, M. Pyle, H. Qiu, W. Rau, A. Reisetter, T. Reynolds, A. Roberts, A. E. Robinson, H. E. Rogers, R. K. Romani, T. Saab, B. Sadoulet, J. Sander, A. Scarff, R. W. Schnee, S. Scorza, K. Senapati, B. Serfass, J. So, D. Speller, C. Stanford, M. Stein, J. Street, H. A. Tanaka, D. Toback, R. Underwood, A. N. Villano, B. von Krosigk, S. L. Watkins, J. S. Wilson, M. J. Wilson, J. Winchell, D. H. Wright, S. Yellin, B. A. Young, X. Zhang, X. Zhao
We present the first limits on inelastic electron-scattering dark matter and dark photon absorption using a prototype SuperCDMS detector having a charge resolution of 0.1 electron-hole pairs (CDMS HVeV, a 0.93 gram CDMS HV device). These electron-recoil limits significantly improve experimental constraints on dark matter particles with masses as low as 1 MeV/$\mathrm{c^2}$. We demonstrate a sensitivity to dark photons competitive with other leading approaches but using substantially less exposure (0.49 gram days). These results demonstrate the scientific potential of phonon-mediated semiconductor detectors that are sensitive to single electronic excitations.
SuperCDMS Collaboration, M. F. Albakry, I. Alkhatib, D. W. P. Amaral, T. Aralis, T. Aramaki, I. J. Arnquist, I. Ataee Langroudy, E. Azadbakht, S. Banik, C. Bathurst, D. A. Bauer, L. V. S. Bezerra, R. Bhattacharyya, P. L. Brink, R. Bunker, B. Cabrera, R. Calkins, R. A. Cameron, C. Cartaro, D. G. Cerdeño, Y. -Y. Chang, M. Chaudhuri, R. Chen, N. Chott, J. Cooley, H. Coombes, J. Corbett, P. Cushman, F. De Brienne, S. Dharani, M. L. di Vacri, M. D. Diamond, E. Fascione, E. Figueroa-Feliciano, C. W. Fink, K. Fouts, M. Fritts, G. Gerbier, R. Germond, M. Ghaith, S. R. Golwala, J. Hall, N. Hassan, B. A. Hines, M. I. Hollister, Z. Hong, E. W. Hoppe, L. Hsu, M. E. Huber, V. Iyer, A. Jastram, V. K. S. Kashyap, M. H. Kelsey, A. Kubik, N. A. Kurinsky, R. E. Lawrence, M. Lee, A. Li, J. Liu, Y. Liu, B. Loer, P. Lukens, D. B. MacFarlane, R. Mahapatra, V. Mandic, N. Mast, A. J. Mayer, H. Meyer zu Theenhausen, É. Michaud, E. Michielin, N. Mirabolfathi, B. Mohanty, S. Nagorny, J. Nelson, H. Neog, V. Novati, J. L. Orrell, M. D. Osborne, S. M. Oser, W. A. Page, R. Partridge, D. S. Pedreros, R. Podviianiuk, F. Ponce, S. Poudel, A. Pradeep, M. Pyle, W. Rau, E. Reid, R. Ren, T. Reynolds, A. Roberts, A. E. Robinson, H. E. Rogers, T. Saab, B. Sadoulet, I. Saikia, J. Sander, A. Sattari, B. Schmidt, R. W. Schnee, S. Scorza, B. Serfass, S. S. Poudel, D. J. Sincavage, C. Stanford, J. Street, H. Sun, F. K. Thasrawala, D. Toback, R. Underwood, S. Verma, A. N. Villano, B. von Krosigk, S. L. Watkins, O. Wen, Z. Williams, M. J. Wilson, J. Winchell, K. Wykoff, S. Yellin, B. A. Young, T. C. Yu, B. Zatschler, S. Zatschler, A. Zaytsev, E. Zhang, L. Zheng, S. Zuber
May 24, 2022·astro-ph.CO·PDF CDMSlite Run 2 was a search for weakly interacting massive particles (WIMPs) with a cryogenic 600 g Ge detector operated in a high-voltage mode to optimize sensitivity to WIMPs of relatively low mass from 2 - 20 GeV/$c^2$. In this article, we present an effective field theory (EFT) analysis of the CDMSlite Run 2 data using an extended energy range and a comprehensive treatment of the expected background. A binned likelihood Bayesian analysis was performed on the recoil energy data, taking into account the parameters of the EFT interactions and optimizing the data selection with respect to the dominant background components. Energy regions within 5$σ$ of known activation peaks were removed from the analysis. The Bayesian evidences resulting from the different operator hypotheses show that the CDMSlite Run 2 data are consistent with the background-only models and do not allow for a signal interpretation assuming any additional EFT interaction. Consequently, upper limits on the WIMP mass and coupling-coefficient amplitudes and phases are presented for each EFT operator. These limits improve previous CDMSlite Run 2 bounds for WIMP masses above 5 GeV/$c^2$.
SuperCDMS Collaboration, D. W. Amaral, T. Aralis, T. Aramaki, I. J. Arnquist, E. Azadbakht, S. Banik, D. Barker, C. Bathurst, D. A. Bauer, L. V. S. Bezerra, R. Bhattacharyya, T. Binder, M. A. Bowles, P. L. Brink, R. Bunker, B. Cabrera, R. Calkins, R. A. Cameron, C. Cartaro, D. G. Cerdeño, Y. -Y. Chang, R. Chen, N. Chott, J. Cooley, H. Coombes, J. Corbett, P. Cushman, F. De Brienne, M. L. di Vacri, M. D. Diamond, E. Fascione, E. Figueroa-Feliciano, C. W. Fink, K. Fouts, M. Fritts, G. Gerbier, R. Germond, M. Ghaith, S. R. Golwala, H. R. Harris, N. Herbert, B. A. Hines, M. I. Hollister, Z. Hong, E. W. Hoppe, L. Hsu, M. E. Huber, V. Iyer, D. Jardin, A. Jastram, M. H. Kelsey, A. Kubik, N. A. Kurinsky, R. E. Lawrence, A. Li, B. Loer, E. Lopez Asamar, P. Lukens, D. MacDonell, D. B. MacFarlane, R. Mahapatra, V. Mandic, N. Mast, A. J. Mayer, É. M. Michaud, E. Michielin, N. Mirabolfathi, B. Mohanty, J. D. Morales Mendoza, S. Nagorny, J. Nelson, H. Neog, V. Novati, J. L. Orrell, S. M. Oser, W. A. Page, P. Pakarha, R. Partridge, R. Podviianiuk, F. Ponce, S. Poudel, M. Pyle, W. Rau, E. Reid, R. Ren, T. Reynolds, A. Roberts, A. E. Robinson, H. E. Rogers, T. Saab, B. Sadoulet, J. Sander, A. Sattari, R. W. Schnee, S. Scorza, B. Serfass, D. J. Sincavage, C. Stanford, M. Stein, J. Street, D. Toback, R. Underwood, S. Verma, A. N. Villano, B. von Krosigk, S. L. Watkins, L. Wills, J. S. Wilson, M. J. Wilson, J. Winchell, D. H. Wright, S. Yellin, B. A. Young, T. C. Yu, E. Zhang, H. G. Zhang, X. Zhao, L. Zheng
This article presents an analysis and the resulting limits on light dark matter inelastically scattering off of electrons, and on dark photon and axion-like particle absorption, using a second-generation SuperCDMS high-voltage eV-resolution detector. The 0.93 gram Si detector achieved a 3 eV phonon energy resolution; for a detector bias of 100 V, this corresponds to a charge resolution of 3% of a single electron-hole pair. The energy spectrum is reported from a blind analysis with 1.2 gram-days of exposure acquired in an above-ground laboratory. With charge carrier trapping and impact ionization effects incorporated into the dark matter signal models, the dark matter-electron cross section $\barσ_{e}$ is constrained for dark matter masses from 0.5--$10^{4} $MeV$/c^{2}$; in the mass range from 1.2--50 eV$/c^{2}$ the dark photon kinetic mixing parameter $\varepsilon$ and the axioelectric coupling constant $g_{ae}$ are constrained. The minimum 90% confidence-level upper limits within the above mentioned mass ranges are $\barσ_{e}\,=\,8.7\times10^{-34}$ cm$^{2}$, $\varepsilon\,=\,3.3\times10^{-14}$, and $g_{ae}\,=\,1.0\times10^{-9}$.
SuperCDMS Collaboration, T. Aralis, T. Aramaki, I. J. Arnquist, E. Azadbakht, W. Baker, S. Banik, D. Barker, C. Bathurst, D. A. Bauer, L. V. S Bezerra, R. Bhattacharyya, T. Binder, M. A. Bowles, P. L. Brink, R. Bunker, B. Cabrera, R. Calkins, R. A. Cameron, C. Cartaro, D. G. Cerdeño, Y. -Y. Chang, J. Cooley, H. Coombes, J. Corbett, B. Cornell, P. Cushman, F. De Brienne, M. L. di Vacri, M. D. Diamond, E. Fascione, E. Figueroa-Feliciano, C. W. Fink, K. Fouts, M. Fritts, G. Gerbier, R. Germond, M. Ghaith, S. R. Golwala, H. R. Harris, N. Herbert, B. A. Hines, M. I. Hollister, Z. Hong, E. W. Hoppe, L. Hsu, M. E. Huber, V. Iyer, D. Jardin, A. Jastram, M. H. Kelsey, A. Kennedy, A. Kubik, N. A. Kurinsky, R. E. Lawrence, A. Li, B. Loer, E. Lopez Asamar, P. Lukens, D. MacDonell, D. B. MacFarlane, R. Mahapatra, V. Mandic, N. Mast, É. M. Michaud, E. Michielin, N. Mirabolfathi, B. Mohanty, J. D. Morales Mendoza, S. Nagorny, J. Nelson, H. Neog, J. L. Orrell, S. M. Oser, W. A. Page, P. Pakarha, R. Partridge, R. Podviianiuk, F. Ponce, S. Poudel, M. Pyle, W. Rau, R. Ren, T. Reynolds, A. Roberts, A. E. Robinson, H. E. Rogers, T. Saab, B. Sadoulet, J. Sander, D. Toback, R. Underwood, S. Verma, A. N. Villano, B. von Krosigk, S. L. Watkins, L. Wills, J. S. Wilson, M. J. Wilson, J. Winchell, D. H. Wright, S. Yellin, B. A. Young, T. C. Yu, E. Zhang, X. Zhao, L. Zheng
We present an analysis of electron recoils in cryogenic germanium detectors operated during the SuperCDMS Soudan experiment. The data are used to set new constraints on the axioelectric coupling of axion-like particles and the kinetic mixing parameter of dark photons, assuming the respective species constitutes all of the galactic dark matter. This study covers the mass range from 40 eV/$c^2$ to 500 eV/$c^2$ for both candidates, excluding previously untested parameter space for masses below ~1 keV/$c^2$. For the kinetic mixing of dark photons, values below $10^{-15}$ are reached for particle masses around 100 eV/$c^2$; for the axioelectric coupling of axion-like particles, values below $10^{-12}$ are reached for particles with masses in the range of a few-hundred eV/$c^2$.
R. Agnese, A. J. Anderson, M. Asai, D. Balakishiyeva, R. Basu Thakur, D. A. Bauer, J. Billard, A. Borgland, M. A. Bowles, D. Brandt, P. L. Brink, R. Bunker, B. Cabrera, D. O. Caldwell, D. G. Cerdeno, H. Chagani, J. Cooley, B. Cornell, C. H. Crewdson, P. Cushman, M. Daal, P. C. F. Di Stefano, T. Doughty, L. Esteban, S. Fallows, E. Figueroa-Feliciano, G. L. Godfrey, S. R. Golwala, J. Hall, H. R. Harris, S. A. Hertel, T. Hofer, D. Holmgren, L. Hsu, M. E. Huber, A. Jastram, O. Kamaev, B. Kara, M. H. Kelsey, A. Kennedy, M. Kiveni, K. Koch, B. Loer, E. Lopez Asamar, R. Mahapatra, V. Mandic, C. Martinez, K. A. McCarthy, N. Mirabolfathi, R. A. Moffatt, D. C. Moore, P. Nadeau, R. H. Nelson, K. Page, R. Partridge, M. Pepin, A. Phipps, K. Prasad, M. Pyle, H. Qiu, W. Rau, P. Redl, A. Reisetter, Y. Ricci, T. Saab, B. Sadoulet, J. Sander, K. Schneck, R. W. Schnee, S. Scorza, B. Serfass, B. Shank, D. Speller, A. N. Villano, B. Welliver, D. H. Wright, S. Yellin, J. J. Yen, B. A. Young, J. Zhang
SuperCDMS is an experiment designed to directly detect Weakly Interacting Massive Particles (WIMPs), a favored candidate for dark matter ubiquitous in the Universe. In this paper, we present WIMP-search results using a calorimetric technique we call CDMSlite, which relies on voltage- assisted Luke-Neganov amplification of the ionization energy deposited by particle interactions. The data were collected with a single 0.6 kg germanium detector running for 10 live days at the Soudan Underground Laboratory. A low energy threshold of 170 eVee (electron equivalent) was obtained, which allows us to constrain new WIMP-nucleon spin-independent parameter space for WIMP masses below 6 GeV/c2.
M. F. Albakry, I. Alkhatib, D. Alonso-Gonzalez, J. Anczarski, T. Aralis, T. Aramaki, I. Ataee Langroudy, C. Bathurst, R. Bhattacharyya, A. J. Biff, P. L. Brink, M. Buchanan, R. Bunker, B. Cabrera, R. Calkins, R. A. Cameron, C. Cartaro, D. G. Cerdeno, Y. -Y. Chang, M. Chaudhuri, J. H. Chen, R. Chen, N. Chott, J. Cooley, H. Coombes, P. Cushman, R. Cyna, S. Das, S. Dharani, M. L. di Vacri, M. D. Diamond, M. Elwan, S. Fallows, E. Fascione, E. Figueroa-Feliciano, S. L. Franzen, A. Gevorgian, M. Ghaith, G. Godden, J. Golatkara, S. R. Golwala, R. Gualtieri, J. Hall, S. A. S. Harms, C. Hays, B. A. Hines, Z. Hong, L. Hsu, M. E. Huber, V. Iyer, V. K. S. Kashyap, S. T. D. Keller, M. H. Kelsey, K. T. Kennard, Z. Kromer, A. Kubik, N. A. Kurinsky, M. Lee, J. Leyva, B. Lichtenberga, J. Liu, Y. Liu, E. Lopez Asamard, P. Lukens, R. Lopez Noe, D. B. MacFarlane, R. Mahapatra, J. S. Mammo, A. J. Mayer, P. C. McNamara, E. Michaud, E. Michielin, K. Mickelson, N. Mirabolfathi, M. Mirzakhani, B. Mohanty, D. Mondal, D. Monteiro, J. Nelson, H. Neog, J. L. Orrell, M. D. Osborne, S. M. Oser, L. Pandey, S. Pandey, R. Partridge, P. K. Patel, D. S. Pedrerosa, W. Peng, W. L. Perry, R. Podviianiuk, M. Potts, S. S. Poudel, A. Pradeep, M. Pyle, W. Rau, T. Reynold, M. Rios, A. Roberts, A. E. Robinson, L. Rosado, J. L. Ryan, T. Saab, D. Sadek, B. Sadoulet, S. P. Sahoo, I. Saikia, S. Salehi, J. Sander, B. Sandoval, A. Sattari, R. W. Schnee, B. Serfass, A. E. Sharbaugh, R. S. Shenoy, A. Simchony, P. Sinervo, Z. J. Smith, R. Soni, K. Stifter, J. Street, M. Stukel, H. Sun, E. Tanner, N. Tenpas, D. Toback, A. N. Villano, J. Viola, B. von Krosigk, O. Wen, Z. William, M. J. Wilson, J. Winchell, S. Yellin, B. A. Young, B. Zatschler, S. Zatschler, A. Zaytsev, E. Zhang, L. Zheng, A. Zuniga, M. J. Zurowski
SuperCDMS SNOLAB uses kilogram-scale germanium and silicon detectors to search for dark matter. Each detector has Transition Edge Sensors (TESs) patterned on the top and bottom faces of a large crystal substrate, with the TESs electrically grouped into six phonon readout channels per face. Noise correlations are expected among a detector's readout channels, in part because the channels and their readout electronics are located in close proximity to one another. Moreover, owing to the large size of the detectors, energy deposits can produce vastly different phonon propagation patterns depending on their location in the substrate, resulting in a strong position dependence in the readout-channel pulse shapes. Both of these effects can degrade the energy resolution and consequently diminish the dark matter search sensitivity of the experiment if not accounted for properly. We present a new algorithm for pulse reconstruction, mathematically formulated to take into account correlated noise and pulse shape variations. This new algorithm fits N readout channels with a superposition of M pulse templates simultaneously - hence termed the N$\times$M filter. We describe a method to derive the pulse templates using principal component analysis (PCA) and to extract energy and position information using a gradient boosted decision tree (GBDT). We show that these new N$\times$M and GBDT analysis tools can reduce the impact from correlated noise sources while improving the reconstructed energy resolution for simulated mono-energetic events by more than a factor of three and for the 71Ge K-shell electron-capture peak recoils measured in a previous version of SuperCDMS called CDMSlite to $<$ 50 eV from the previously published value of $\sim$100 eV. These results lay the groundwork for position reconstruction in SuperCDMS with the N$\times$M outputs.
M. Matheny, A. Roberts, A. Srinivasan, A. N. Villano
Nuclear recoils in germanium and silicon are shown to have much larger variance in electron-hole production than their electron-recoil counterparts for recoil energies between 10 and 200\,keV. This effect--owing primarily to deviations in the amount of energy given to the crystal lattice in response to a nuclear recoil of a given energy--has been predicted by the Lindhard model. We parameterize the variance in terms of an intrinsic nuclear recoil Fano factor which is 24.3$\pm$0.2 and 26$\pm$8 at around 25\,keV for silicon and germanium respectively. The variance has important effects on the expected signal shapes for experiments utilizing low-energy nuclear recoils such as direct dark matter searches and coherent neutrino-nucleus scattering measurements.
K. Harris, A. Gevorgian, A. J. Biffl, A. N. Villano
Following neutron capture in a material there will be prompt nuclear recoils in addition to the gamma cascade. The nuclear recoils that are left behind in materials are generally below 1\,keV and therefore in the range of interest for dark matter experiments and CE$ν$NS studies--both as backgrounds and calibration opportunities. Here we obtain the spectrum of prompt nuclear recoils following neutron capture for silicon.
SuperCDMS Collaboration, M. F. Albakry, I. Alkhatib, D. W. P. Amaral, T. Aralis, T. Aramaki, I. J. Arnquist, I. Ataee Langroudy, E. Azadbakht, S. Banik, C. Bathurst, D. A. Bauer, L. V. S. Bezerra, R. Bhattacharyya, M. A. Bowles, P. L. Brink, R. Bunker, B. Cabrera, R. Calkins, R. A. Cameron, C. Cartaro, D. G. Cerdeño, Y. -Y. Chang, M. Chaudhuri, R. Chen, N. Chott, J. Cooley, H. Coombes, J. Corbett, P. Cushman, F. De Brienne, M. L. di Vacri, M. D. Diamond, E. Fascione, E. Figueroa-Feliciano, C. W. Fink, K. Fouts, M. Fritts, G. Gerbier, R. Germond, M. Ghaith, S. R. Golwala, J. Hall, B. A. Hines, M. I. Hollister, Z. Hong, E. W. Hoppe, L. Hsu, M. E. Huber, V. Iyer, A. Jastram, V. K. S. Kashyap, M. H. Kelsey, A. Kubik, N. A. Kurinsky, R. E. Lawrence, M. Lee, A. Li, J. Liu, Y. Liu, B. Loer, P. Lukens, D. MacDonell, D. B. MacFarlane, R. Mahapatra, V. Mandic, N. Mast, A. J. Mayer, H. Meyer zu Theenhausen, É. Michaud, E. Michielin, N. Mirabolfathi, B. Mohanty, J. D. Morales Mendoza, S. Nagorny, J. Nelson, H. Neog, V. Novati, J. L. Orrell, M. D. Osborne, S. M. Oser, W. A. Page, R. Partridge, D. S. Pedreros, R. Podviianiuk, F. Ponce, S. Poudel, A. Pradeep, M. Pyle, W. Rau, E. Reid, R. Ren, T. Reynolds, A. Roberts, A. E. Robinson, T. Saab, B. Sadoulet, I. Saikia, J. Sander, A. Sattari, A. Scarff, B. Schmidt, R. W. Schnee, S. Scorza, B. Serfass, D. J. Sincavage, C. Stanford, J. Street, F. K. Thasrawala, D. Toback, R. Underwood, S. Verma, A. N. Villano, B. von Krosigk, S. L. Watkins, O. Wen, Z. Williams, M. J. Wilson, J. Winchell, K. Wykoff, S. Yellin, B. A. Young, T. C. Yu, B. Zatschler, S. Zatschler, A. Zaytsev, E. Zhang, L. Zheng, S. Zuber
Two photo-neutron sources, $^{88}$Y$^{9}$Be and $^{124}$Sb$^{9}$Be, have been used to investigate the ionization yield of nuclear recoils in the CDMSlite germanium detectors by the SuperCDMS collaboration. This work evaluates the yield for nuclear recoil energies between 1 keV and 7 keV at a temperature of $\sim$ 50 mK. We use a Geant4 simulation to model the neutron spectrum assuming a charge yield model that is a generalization of the standard Lindhard model and consists of two energy dependent parameters. We perform a likelihood analysis using the simulated neutron spectrum, modeled background, and experimental data to obtain the best fit values of the yield model. The ionization yield between recoil energies of 1 keV and 7 keV is shown to be significantly lower than predicted by the standard Lindhard model for germanium. There is a general lack of agreement among different experiments using a variety of techniques studying the low-energy range of the nuclear recoil yield, which is most critical for interpretation of direct dark matter searches. This suggests complexity in the physical process that many direct detection experiments use to model their primary signal detection mechanism and highlights the need for further studies to clarify underlying systematic effects that have not been well understood up to this point.