Jeremy Lopez

Bio: Jeremy Lopez is an academic researcher from Massachusetts Institute of Technology. The author has contributed to research in topics: Dark matter & Dark Matter Time Projection Chamber. The author has an hindex of 6, co-authored 11 publications receiving 390 citations. Previous affiliations of Jeremy Lopez include University of Colorado Boulder.

The case for a directional dark matter detector and the status of current experimental efforts

Abstract: We present the case for a dark matter detector with directional sensitivity. This document was developed at the 2009 CYGNUS workshop on directional dark matter detection, and contains contributions from theorists and experimental groups in the field. We describe the need for a dark matter detector with directional sensitivity; each directional dark matter experiment presents their project's status; and we close with a feasibility study for scaling up to a one ton directional detector, which would cost around $150M.

Measurement of the directional sensitivity of Dark Matter Time Projection Chamber detectors

Abstract: The dark matter time projection chamber (DMTPC) is a direction-sensitive detector designed to measure the direction of recoiling $^{19}\mathrm{F}$ and $^{12}\mathrm{C}$ nuclei in low-pressure ${\mathrm{CF}}_{4}$ gas using optical and charge readout systems In this paper, we employ measurements from two DMTPC detectors, with operating pressures of 30--60 torr, to develop and validate a model of the directional response and performance of such detectors as a function of recoil energy Using our model as a benchmark, we formulate the necessary specifications for a scalable directional detector with sensitivity comparable to that of current-generation counting (nondirectional) experiments, which measure only recoil energy Assuming the performance of existing DMTPC detectors, as well as current limits on the spin-dependent WIMP-nucleus cross section, we find that a 10--20 kg scale direction-sensitive detector is capable of correlating the measured direction of nuclear recoils with the predicted direction of incident dark matter particles and providing decisive ($3\ensuremath{\sigma}$) confirmation that a candidate signal from a nondirectional experiment was indeed induced by elastic scattering of dark matter particles off of target nuclei

Background rejection in the DMTPC dark matter search using charge signals

Abstract: The Dark Matter Time Projection Chamber (DMTPC) collaboration is developing a low pressure gas TPC for detecting Weakly Interacting Massive Particle (WIMP)-nucleon interactions. Optical readout with CCD cameras allows for the detection of the daily modulation of the direction of the dark matter wind. In order to reach sensitivities required for WIMP detection, the detector needs to minimize backgrounds from electron recoils. This paper demonstrates that a simplified CCD analysis achieves 7.3 × 10 − 5 rejection of electron recoils while a charge analysis yields an electron rejection factor of 3.3 × 10 − 4 for events with 241 Am-equivalent ionization energy loss between 40 keV and 200 keV. A combined charge and CCD analysis yields a background-limited upper limit of 1.1 × 10 − 5 (90% confidence level) for the rejection of γ and electron events. Backgrounds from alpha decays from the field cage are eliminated by introducing a veto electrode that surrounds the sensitive region in the TPC. CCD-specific backgrounds are reduced more than two orders of magnitude when requiring a coincidence with the charge readout.

The Dark Matter Time Projection Chamber 4Shooter directional dark matter detector: Calibration in a surface laboratory

Abstract: The 4Shooter is a prototype dark matter detector built by the Dark Matter Time Projection Chamber (DMTPC) collaboration. The aim of the collaboration is to observe dark matter with directional sensitivity by measuring the recoil directions of nuclei struck by dark matter particles. The 4Shooter is a single time projection chamber containing CF4 gas, with both optical (CCD and photomultiplier tube) and charge readout. This paper describes the 4Shooter and presents results from the commissioning of the detector in a surface laboratory.

Dark matter direct-detection experiments

Abstract: In recent decades, several detector technologies have been developed with the quest to directly detect dark matter interactions and to test one of the most important unsolved questions in modern physics. The sensitivity of these experiments has improved with a tremendous speed due to a constant development of the detectors and analysis methods, proving uniquely suited devices to solve the dark matter puzzle, as all other discovery strategies can only indirectly infer its existence. Despite the overwhelming evidence for dark matter from cosmological indications at small and large scales, clear evidence for a particle explaining these observations remains absent. This review summarises the status of direct dark matter searches, focusing on the detector technologies used to directly detect a dark matter particle producing recoil energies in the keV energy scale. The phenomenological signal expectations, main background sources, statistical treatment of data and calibration strategies are discussed.

Colloquium: Annual modulation of dark matter

Abstract: Direct detection experiments, which are designed to detect the scattering of dark matter off nuclei in detectors, are a critical component in the search for the Universe’s missing matter. This Colloquium begins with a review of the physics of direct detection of dark matter, discussing the roles of both the particle physics and astrophysics in the expected signals. The count rate in these experiments should experience an annual modulation due to the relative motion of the Earth around the Sun. This modulation, not present for most known background sources, is critical for solidifying the origin of a potential signal as dark matter. The focus is on the physics of annual modulation, discussing the practical formulas needed to interpret a modulating signal. The dependence of the modulation spectrum on the particle and astrophysics models for the dark matter is illustrated. For standard assumptions, the count rate has a cosine dependence with time, with a maximum in June and a minimum in December. Well-motivated generalizations of these models, however, can affect both the phase and amplitude of the modulation. Shown is how a measurement of an annually modulating signal could teach us about the presence of substructure in the galactic halo or about the interactions between dark and baryonic matter. Although primarily a theoretical review, the current experimental situation for annual modulation and future experimental directions is briefly discussed.

The Theory of the Photographic Process

Abstract: DR. C. E. K. MEES, with the help of the Kodak Research Laboratories, has written a book that will be for many years the standard authority on the photographic process. His title describes the book as an account of the theory; but theory is not conceived in a narrow sense as the counterpart of experiment, but rather as including almost everything about photography except its practice. The first chapters deal with the emulsions, what they are made of and how they are prepared; the action of light is then described, the processes that take place in photographic materials under its influence and the large number of theories which has been advanced to account for them. Development and fixation are then discussed, again with the emphasis on the details of changes that take place in emulsions and on attempts to explain them in terms of physics and chemistry. There are further chapters on sensitometry, on the nature of the developed image and on the photographic aspects of sound recording. Finally an, account is given of the use of dyestuffs for the production of colour-sensitive film, and for desensitization. The Theory of the Photographic Process By Dr. C. E. Kenneth Mees. Pp. xi + 1124. (New York: The Macmillan Company, 1942.) 60s. net.

Dark matter direct-detection experiments

Abstract: In the past decades, several detector technologies have been developed with the quest to directly detect dark matter interactions and to test one of the most important unsolved questions in modern physics. The sensitivity of these experiments has improved with a tremendous speed due to a constant development of the detectors and analysis methods, proving uniquely suited devices to solve the dark matter puzzle, as all other discovery strategies can only indirectly infer its existence. Despite the overwhelming evidence for dark matter from cosmological indications at small and large scales, a clear evidence for a particle explaining these observations remains absent. This review summarises the status of direct dark matter searches, focussing on the detector technologies used to directly detect a dark matter particle producing recoil energies in the keV energy scale. The phenomenological signal expectations, main background sources, statistical treatment of data and calibration strategies are discussed.