Talks & Events
KICP Colloquia: 2016
Searching for Dark Matter With Bubble Chambers
Andrew Sonnenschein, Fermilab
PDF | Video
Development of bubble chamber detectors for WIMP dark matter was pioneered at KICP in the early 2000’s. In the intervening years, we scaled the technology from the initial test-tube sized detectors operated in the basement of the LASR building to a 60 kg chamber now installed 2-km underground at SNOLAB. I will review the history of these developments and the most recent results from the PICO-2L and PICO-60 experiments.
Quantum Twists of Space: Exotic Rotational Correlations from Quantum Geometry, Their Effects on Interferometer Signals, and Their Connection with Cosmic Acceleration
Craig Hogan, University of Chicago
PDF | Video
The talk will review theoretical arguments that if space and time emerge from a quantum system at the Planck scale, there should be nonlocal exotic quantum correlations of positions of massive bodies, even on scales much larger than the Planck length. In relational theories with no fixed background space, these could take the form of rotational quantum fluctuations in the inertial frame. Basic quantum principles are used to derive their effect on correlations in the signals of interferometers. An experimental test is proposed, based on a reconfiguration of the Fermilab Holometer. It is conjectured that entanglement of these rotational correlations with the Standard Model vacuum could explain the value of the cosmological constant in terms of known scales of physics.
Improved Limits from the Large Underground Xenon Dark Matter Experiment
Nicole Larsen, KICP
PDF | Video
A wealth of astrophysical research supports the existence of dark matter in the universe, yet the exact identity and nature of this unknown particle remain elusive. The Large Underground Xenon (LUX) dark matter search is a 370-kg xenon-based time projection chamber (TPC) that operates by detecting light and ionization signals from particles incident upon a xenon target. With the 2013 report of the world’s first sub-zeptobarn spin-independent WIMP-nucleon cross section limit, the LUX (Large Underground Xenon) experiment emerged as a frontrunner in the field of dark matter direct detection. In December 2015, LUX released an updated analysis of its 2013 dataset with increased detector exposure, updates to the background model, upgraded event reconstruction algorithms, and novel calibrations leading to an overall 23% increase in sensitivity for high-mass WIMPs and even more significant improvements for low-mass WIMPs. This talk details the design of the LUX experiment and reviews the analysis and reanalysis of the 2013 dataset leading to the world’s most stringent constraints on spin-independent WIMP-nucleon scattering for WIMPs above mass 4 GeV.
New Approaches to Dark Matter
Justin Khoury, University of Pennsylvania
PDF | Video
In this talk I will discuss a novel theory of superfluid dark matter. The scenario matches the predictions of the LambdaCDM model on cosmological scales while simultaneously reproducing the MOdified Newtonian Dynamics (MOND) empirical success on galactic scales. The dark matter and MOND components have a common origin, as different phases of a single underlying substance. This is achieved through the rich and well-studied physics of superfluidity. The framework naturally distinguishes between galaxies (where MOND is successful) and galaxy clusters (where MOND is not): due to the higher velocity dispersion in clusters, and correspondingly higher temperature, the DM in clusters is either in a mixture of superfluid and normal phases, or fully in the normal phase. The model makes various observational predictions that distinguishes it from both LambdaCDM and standard MOND. In the last part of the talk, I will discuss an on-going attempt at explaining cosmic acceleration as yet another manifestation of dark matter superfluidity.
Probing the Cosmic Dawn and the Epoch of Reionization with the 21cm Hydrogen Line
Jacqueline Hewitt, MIT
Measurements of the cosmic microwave background at redshift z ~ 1100 give us information about the initial density fluctuations that seeded subsequent gravitational collapse and structure formation. Observations of galaxies and clusters at z <~ 7 give us information about the outcome of this structure formation. Between those redshifts lies a modern frontier of cosmology - the cosmic dawn that marked the formation of the first stars and galaxies and the deionization of the intergalactic medium. Direct observations of this phase of the universe's history are just beginning. A particularly promising technique is that of mapping hydrogen structures using the redshifted 21cm radio line. Several recently completed low frequency radio arrays are now operating and providing us with an early glimpse into the Epoch of Rionization. Building upon these results a next generation instrument, the Hydrogen Epoch of Reionization Array (HERA) is beginning construction. HERA will be significantly more capable, and presents interesting opportunities and challenges.
WIMPs taking selfies: the DAMIC experiment at SNOLAB
Paolo Privitera, KICP/The University of Chicago
PDF | Video
The DAMIC (Dark MAtter In CCDs) experiment employs the bulk silicon of ~mm-thick charge-coupled devices (CCDs) to detect coherent elastic scattering of Weakly-Interacting Massive Particles (WIMPs) - putative yet-to-be-discovered particles which may explain the dark matter in the universe. This novel technique features an unprecedentedly low energy threshold (few tens of eVee) for the detection of nuclear recoils, providing optimal sensitivity for low mass WIMPs (< 10 GeV). In addition, the spatial resolution of the CCDs, unique amongst dark matter detectors, provides powerful methods to identify and mitigate environmental and cosmogenic backgrounds. I will show recent results from DAMIC R&D data which demonstrate the potential of the CCD technology for WIMP detectors and first images from DAMIC100, a 100 g detector with 18 CCDs under installation at SNOLAB.
Results from the first year of the HAWC Gamma Ray Observatory
Jordan Goodman, Maryland
PDF | Video
The High Altitude Water Cherenkov (HAWC) Gamma-ray Observatory in the high mountains of Mexico was completed in March of 2015 and is now giving us a new view of the TeV sky. HAWC is 15 times more sensitive than the previous generation of widefield EAS gamma-ray instruments and is able to detect the Crab nebula at >6σ with each daily transit. In our first year of operation, HAWC has a 5σ detection sensitivity for a source of ~50mCrab. Unlike Imaging Atmospheric Cherenkov Telescopes (IACTs), HAWC operates 24hrs/day with over a 95% on-time and observes the entire overhead sky (~2sr). HAWC’s peak energy sensitivity is 2-10 TeV which is ~10x higher than IACTs such as VERITAS and HESS, which makes their observations quite complementary. This talk will present results from the first year of HAWC data including our study of the galactic plane including new sources not yet detected by IACTs as well as spectra and morphology of bright sources. In addition, results of our monitoring of transient AGN will be presented.
The Dark Energy Survey and Gravitational Waves
Marcelle Soares-Santos, Fermilab
PDF | Video
In this talk I present recent results of the Dark Energy Survey (DES) searches for optical counterparts to Gravitational Wave (GW) events detected by the LIGO/Virgo Collaboration. Our program achieved greater sensitivity than any other optical facility last year. For the second observing campaign (Fall/2016-Spring/2017) our goals are to either make a detection or establish significant constraints on optical emission from such events. DES is the greatest optical imaging survey yet, aiming at percent-level precision measurements of cosmological parameters from a combination of probes such as type Ia supernovae, galaxy clusters, and weak gravitational lensing. These probes are limited by astrophysical systematics and new independent methods are required in order to beat systematic effects down to sub-percent levels. Standard sirens, events for which distances are determined from their gravitational wave signal, are one possible new method to meet that challenge. Our program will potentially have a great impact in our field by exploring this possibility from the observational perspective. In this talk I will also briefly discuss this exciting prospect for future observing campaigns.
The First Four Months of Gravitational Wave Astronomy
Ben Farr, Enrico Fermi Institute and KICP
PDF | Video
On September 14, 2015 LIGO made the first direct detection of gravitational waves, marking the beginning of gravitational wave astronomy. The LIGO instruments continued to take data over the next four months, completing their first observing run on January 19, 2016 with 51.5 days of coincident data. I will present results from advanced LIGO's first four months of operation, and what they have taught us thus far.
New Directions in Searching for the Dark Universe
Surjeet Rajendran, UC Berkeley
PDF | Video
Observational bounds currently permit the existence of a large number of dark matter candidates, ranging from ultra-light axions with masses ~ 10^(-22) eV to MACHOs with mass as large as 10^(24) gm. It is important to develop experimental methods to constrain this vast range of parameters. In this talk, I will describe new experimental methods to probe a wide variety of dark matter candidates, ranging from ultra-light axions with masses ~ 10^(-22) eV to light WIMPs with mass in the keV - GeV range. A variety of precision measurement technologies such as optical/atomic interferometry and SQUID magnetometry can be applied to search for these particles. I will also discuss methods to search for the direction of the nuclear recoil induced by conventional WIMP scattering in detectors with solid state densities. These directional detectors may enable probes of conventional WIMP dark matter beyond the solar neutrino floor.
Increasing Accuracy and Increasing Tension in H0
Wendy Freedman, KICP
PDF | Video
The accuracy in direct measurement of distances to galaxies has continued to improve dramatically over the past decade. Local measurements of the Hubble constant based on Hubble Space Telescope observations of astrophysical standard candles -- Cepheids and Type Ia supernovae -- have converged on a value of about 73 km/sec/Mpc with an uncertainty of 2-3%. At the same time, estimates assuming a Lambda-CDM standard model and fitting highly precise measurements of cosmic microwave background fluctuations have yielded a value of Ho = 67 km/sec/Mpc. The two methods disagree at approximately the 3-sigma level. The reason for this discrepancy is not understood at present, and new data have only increased the tension. If real, the disagreement could be signaling missing physics in the standard model; for example, additional dark radiation. Major efforts are ongoing to improve further the accuracy in the local measurements, including developing other techniques to test the Cepheid distance scale. In the near future JWST and Gaia will provide a path to measuring Ho to 1%, comparable to the precision in CMB measurements.