Phillip S Barbeau, Duke University
Recoils from Neutrinos: past, present, future

September 24, 2015 (3:20 PM - 3:50 PM)

PDF, 12.84 MB
Co-authors: G. Rich
I will discuss a decades worth of efforts to calibrate the response of low-threshold detectors to sub-keV recoils. The path taken focuses on the development of very low energy, controlled beams of neutrons. Efforts have include sub-keV calibrations for Ge semiconductor detectors; and more recently an effort to provide a comprehensive and precise calibration for NaI and CsI scintillators.
Ritoban Basu Thakur, KICP
For when we get there, detectors @ 5-50 eV

September 25, 2015 (12:00 PM - 12:20 PM)

PDF, 7.11 MB
Ionization production from nuclear recoils has been a central topic in direct detection of dark matter. This talk will overview our expectations when we probe ionization production from recoils (electron or nuclear) in the ~10 eV range. In particular I will outline rule-of-thumb principles, presently used ubiquitously, which may not apply at these energy scales. The talk will be intended for semiconductor devices.
Alvaro Chavarria, Kavli Institute for Cosmological Physics
Response of a CCD to low energy nuclear recoils from a 124Sb-9Be photo-neutron source

September 24, 2015 (1:55 PM - 2:25 PM)

PDF, 4.39 MB
Seonho Choi, Seoul National University
Measurement of the Quenching and Channeling Effects in a CsI Crystal

September 23, 2015 (1:25 PM - 1:55 PM)

Co-authors: Juhee Lee
We have studied channeling effects in a cesium iodide (CsI) crystal that is similar in composition to the ones being used in a search for Weakly Interacting Massive Particles (WIMPs) dark matter candidates, and measured its energy-dependent quenching factor, the relative scintillation yield for electron and nuclear recoils. The experimental results are reproduced with a GEANT4 simulation that includes a model of the scintillation efficiency as a function of electronic stopping power. We present the measured and simulated quenching factors and the estimated effects of channeling.
Juan Collar, Kavli Institute for Cosmological Physics
You are doing it wrong: the intricacies of low-energy nuclear recoil calibrations

September 25, 2015 (10:50 AM - 11:20 AM)

PDF, 1.46 MB
Taking NaI[Tl] as a case study, I will discuss several ways in which a nuclear recoil response calibration can go astray.
Eric Dahl, Northwesern University
Bubble Chamber Physics -- electron and nuclear recoil response in the PICO dark matter detectors

September 25, 2015 (10:00 AM - 10:35 AM)

PDF, 9.2 MB
Co-authors: PICO Collaboration
Calibration of the PICO bubble chamber dark matter detectors presents several unique challenges. For nuclear recoils, we must deal with both severe rate limitations and the fact that our bubble chambers are threshold detectors where we can measure only an integrated response. For electron recoils we face the challenge of measuring sensitivities of order 10^-10 and beyond, dealing with the surprises that await in the realm of ultra-high discrimination. Nevertheless we now have a solid understanding, both theoretically and supported by measurement, of bubble nucleation efficiencies on both of these fronts. I will describe the array of experiments that have led us to this understanding.
Luke Goetzke, Columbia University
Light and Charge Yield of Low-Energy Electronic Recoils in Liquid Xenon

September 23, 2015 (2:00 PM - 2:30 PM)

PDF, 16.63 MB
Co-authors: E. Aprile, M. Anthony, H. Contreras, A. J. Melgarejo Fernandez, Z. Greene, M. Messina, P. de Perio, G. Plante, A. Rizzo, M. Weber, Y. Zhang
The dependence of the light and charge yield of liquid xenon (LXe) on the applied electric field is important for dark matter detectors using LXe time projections chambers. Very few measurements have been made of this field dependence at low recoil energies, <10keV. In this talk I will present results of recent measurements of the light and charge yield of electronic recoils in LXe using the neriX detector at Columbia University. The energy and field dependence of the yields was measured using the Compton coincidence technique at four drift fields relevant for LXe dark matter detectors, down to very low recoil energies, and with relatively high precision.
Lauren Hsu, Fermilab
Calibration of SuperCDMS detectors with a photoneutron source

September 24, 2015 (2:30 PM - 3:00 PM)

PDF, 17.28 MB
Co-authors: on behalf of the SuperCDMS collaboration
SuperCDMS has pioneered the use of athermal phonon and ionization sensors to achieve world-leading sensitivity to a theoretically-favored dark matter candidate, the Weakly Interacting Massive Particle. However, such sensitivity must be accompanied by an accurate understanding of the nuclear recoil energy scale in order to properly interpret the data. I will describe the ongoing efforts to validate the nuclear recoil energy scale for SuperCDMS detectors. I will first briefly review the principle of operation of the two types of SuperCDMS detectors, the iZIP and HV detector. I will also review the basic calibration techniques applied to the detectors. Since July of this year, we have modified the Soudan installation to take data using two photoneutron sources (Y/Be and Sb/Be). The purpose of this calibration is to validate the low-energy nuclear recoil energy scale of the Ge detectors, while operated in both the default iZIP and HV modes. I will describe this effort and present the status and plans for this work.
Gaosong Li, Shanghai Jiao Tong University
Neutron Calibration Sources in the Daya Bay Experiment

September 23, 2015 (3:25 PM - 3:55 PM)

PDF, 1.72 MB
Co-authors: J. Liu, R. Carr, D.A. Dwyer, W.Q. Gu, R.D. McKeown, X. Qian, R.H.M. Tsang, F.F. Wu, C. Zhang
We describe the design and construction of the low rate neutron calibration sources used in the Daya Bay Reactor Anti-neutrino Experiment. Such sources are free of correlated gamma-neutron emission, which is essential in minimizing induced background in the anti-neutrino detector. The design characteristics have been validated in the Daya Bay anti-neutrino detector.
Qing Lin, Columbia University
Response and Discrimination of Low-Energy Electronic and Nuclear Recoils in Liquid Xenon

September 23, 2015 (10:30 AM - 11:00 AM)

PDF, 5.56 MB
In recent years, liquid xenon (LXe) detectors played a leading role in the field of direct dark matter search. The interpretation of the dark matter search result in LXe detector depends significantly on the understanding of the signal responses in LXe, especially in the low-energy region. In this talk, I will present the measurement of the low-energy recoils in LXe under a field of 236V/cm to 3.93kV/cm, using a prototype LXe time projection chamber with high position and energy resolution. In addition I’ll also talk about the study and modeling of the gamma discrimination in LXe which is the key for getting a lower electron recoil background to achieve a higher sensitivity for dark matter detection.
Darryl Masson, Purdue University
A Rn-220 source for internal calibration of low-background detectors

September 25, 2015 (9:35 AM - 9:55 AM)

PDF, 1.22 MB
Co-authors: Purdue group
The calibration of next generation of low-background particle detectors presents new challenges owing to their increased size. Here we present the characterization of a Rn-220 source and place limits on the release of long-lived contaminants from the source that would render it unusable by low-background detectors, most notably Th-228, Ra-224, and Rn-222.
Dongming Mei, The University of South Dakota
Detector Response to Low-Energy Recoils

September 23, 2015 (9:15 AM - 9:45 AM)

PDF, 1.43 MB
Co-authors: Lu Wang and Wenzhao Wei
We will review several our publications about ionization efficiency and scintillation efficiency for detectors including germanium, noble liquids, and inorganic scintillators. Using the recent progress on modeling detector response, we will present new results on discriminating nuclear recoils from electronic recoils in low-energy region for germanium and liquid detectors. New calibration methods will be discussed as well.
Kaixuan Ni, University of California, San Diego
Modelling Xenon Scintillation and Ionization Mechanisms in NEST

September 24, 2015 (9:00 AM - 9:30 AM)

PDF, 31.69 MB
Co-authors: NEST Collaboration
Alan E Robinson, Fermilab / University of Chicago
Photoneutron Source Carachterization and Neutron Simulations

September 24, 2015 (1:30 PM - 1:50 PM)

PDF, 1.62 MB
Radioisotope photoneutron sources, e.g. $^{88}$Y/Be, are a deployable monoenergetic neutron sources. When using these sources for nuclear recoil calibrations, the strength and shape of the nuclear recoil spectrum inside the detector must be known. Evaluations of the strengths of Y/Be and Sb/Be sources used at the University of Chicago will be presented, including a new evaluation of the $^9$Be$(gamma,n)$ cross-section. In contrast to AmBe or californium neutrons, the propagation of photoneutrons is highly sensitive to resonances in the scattering cross-sections of materials. The simulation of photoneutrons will be discussed including source energy-angle distributions, cross-section libraries (see PRC 89 032801 (2014)), and simulation validation.
Tarek Saab, University of Florida
Precision Measurement Of Nuclear Recoil Ionization Yields For Low Mass Wimp Searches

September 23, 2015 (11:05 AM - 11:35 AM)

PDF, 7.71 MB
Co-authors: Enectali Figueroa-Feliciano
Understanding the response of dark matter detectors at the lowest recoil energies is essential for correctly interpreting data from current experiments or predicting the sensitivity of future experiments to low mass WIMPs. In particular, the SuperCDMS experiment relies on ionization yield for determining the correct recoil energy of candidate nuclear recoil events, however, few measurements in cryogenic crystals exist below 1 keV. Using the voltage-assisted calorimetric ionization detection technique with a mono-energetic neutron source, we show that it is possible to determine the ionization yield in Si and Ge crystals down to an energy to 100 eV. Such a measurement will also be able to shed light determine the statistics of ionization production at these low energies.
Richard Saldanha, Kavli Institute for Cosmological Physics
Scintillation and Ionization Yield of Liquid Argon Nuclear Recoils

September 24, 2015 (9:35 AM - 10:05 AM)

PDF, 7.81 MB
Samuele Sangiorgio, Lawrence Livermore National Lab
Calibration and Modeling of Nuclear and Electron Recoils in Liquid Argon

September 24, 2015 (11:35 AM - 12:05 PM)

PDF, 4.06 MB
A fundamental knowledge of the low-energy response of liquid argon to electron and nuclear recoils is necessary to understand the reach of argon-based detectors in detecting WIMPs and Coherent Elastic Neutrino-Nucleus Scattering. Using mono-energetic neutrons from a collimated and filtered 7Li(p,n) source, we measured the absolute ionization yield of nuclear recoils in liquid argon at 6.7 keVr at drift fields from 200-2130 V/cm. Ar-37 was also used to calibrate the detector to electron recoils down to sub-keV energies. By comparing with existing models, we derive interesting conclusions on the recombination physics of nuclear and electromagnetic recoils in liquid argon in the few keV energy range. Alongside with the experimental efforts, we developed a new simulation tool to predict the ionization yield in argon. The presentation will discuss our experimental and modeling effort and their implications for liquid argon detectors.
Bjorn J Scholz, University of Chicago
Measuring the quenching factor of germanium at low energies using an 88Y/Be photoneutron source

September 25, 2015 (11:25 AM - 11:55 AM)

PDF, 1.85 MB
Co-authors: JUAN I COLLAR
Peter Sorensen, LBL
The limitations of Lindhard theory to predict the ionization produced by nuclear recoils at the lowest energies

September 25, 2015 (9:00 AM - 9:30 AM)

PDF, 5.72 MB
Javier Tiffenberg, Fermilab
Results from the Antonella experiment

September 24, 2015 (10:10 AM - 10:40 AM)

PDF, 7.75 MB
James R Verbus, Brown University
Measurement of Ultra-low Energy Nuclear Recoils in the LUX Detector Using a D-D Neutron Generator

September 23, 2015 (2:35 PM - 3:05 PM)

PDF, 36.32 MB
The LUX dark matter search experiment is a 350 kg two-phase liquid/gas xenon time projection chamber located at the 4850 ft level of the Sanford Underground Research Facility in Lead, SD. We will describe a novel calibration of nuclear recoils (NR) in liquid xenon (LXe) performed in situ in the LUX detector using mono-energetic 2.45 MeV neutrons produced by a D-D neutron generator. This technique was used to measure the NR charge yield in LXe (Qy) to <1 keV recoil energy with an absolute determination of the deposited energy. The LUX Qy result is a factor of ×5 lower in energy compared to any other previous measurement in the field, and provides a significant improvement in calibration uncertainties. We also present a measurement of the NR light yield in LXe (Leff) to recoil energies <2 keV using the LUX D-D data. The Leff result is also lower in energy with smaller uncertainties than has been previously achieved. These absolute, ultra-low energy calibrations of the NR signal yields in LXe are a clear confirmation of the detector response used for the first LUX WIMP search analysis. Strategies for extending this calibration technique to even lower energies and smaller uncertainties will be discussed.
Lu Wang, The University of South Dakota
Xenon detectors response to low energy recoils for dark matter searches

September 23, 2015 (9:50 AM - 10:10 AM)

PDF, 0.74 MB
Co-authors: Wenzhao Wei, Dongming Mei
Noble liquid xenon experiments, such as XENON100, LUX, XENON 1-Ton, and LZ are large dark matter experiments directly searches for weakly interacting massive particles (WIMPs). One of the most important features is to discriminate nuclear recoils from electronic recoils. Detector response is generally calibrated with different radioactive sources including 83mKr, tritiated methane, 241AmBe, 252Cf, and DD-neutrons. The electronic recoil and nuclear recoil bands have been determined by these calibrations. However, the width of nuclear recoil band needs to be fully understood. We derive a theoretical model to understand the correlation of the width of nuclear recoil band and intrinsic statistical variation. In addition, we conduct experiments to validate the theoretical model. In this paper, we present the study of intrinsic statistical variation contributing to the width of nuclear recoil band.
Wenzhao Wei, The University of South Dakota
Germanium Detector Response to Low Energy Recoils for Dark Matter Searches

September 23, 2015 (11:40 AM - 12:00 PM)

PDF, 0.84 MB
Co-authors: Lu Wang, Dongming Mei
The intrinsic statistical variation in nuclear recoils is a critical part that cannot be ignored when calculating energy resolution of germanium detector in detecting WIMPs. Have a good theoretical understanding about the intrinsic statistical variation in nuclear recoils and develop a model for calculating this variation based on experimental data is of great importance in determining the width of nuclear recoil band, which is used to identify nuclear recoils events. Hence, we designed an experiment to study the intrinsic statistical variation in nuclear recoils with various gamma sources and AmBe neutron source. In addition, we developed a theoretical model to calculate the intrinsic statistical variation in nuclear recoils based on data from AmBe neutron source. In this work, we will present our data and theoretical calculation for nuclear recoils
Jingke Xu, Lawrence Livermore National Laboratory
Scintillation efficiency measurement of Na recoils in NaI(Tl) below the DAMA/LIBRA energy threshold

September 24, 2015 (11:00 AM - 11:30 AM)

PDF, 3.63 MB