Rebecca Canning (Stanford) - Understanding Active Galactic Nuclei (AGN) in the most massive cosmic laboratories
2018-04-20 12:00 - 13:00 (America/Los_Angeles) | 50A-5132- Sessler, 50A-5132 Sessler Conference Room, CA
Supermassive Black Holes (SMBHs) lurk in the centers of all massive galaxies, a fraction of these SMBHs are actively accreting and this can result in powerful outbursts which have important consequences for galaxy formation and evolution. However, the conditions under which a SMBH becomes active and the manner in which it interacts with its environment are not well understood. Clusters of galaxies offer us wonderful cosmic laboratories in which we can observe these processes. I will discuss what observations of these massive galaxy clusters can tell us about the role of AGN feedback in both maintaining a delicate balance between heating and cooling and in searching for a casual link between SMBHs and galaxy co-evolution and detail the Cluster AGN Topography Survey which is undertaking a census of SMBH activity in massive galaxy clusters.

Dan Dwyer (LBNL) - Demonstration of a true 3D micro-power sensor for liquid argon time projection chambers
2018-04-27 12:00 - 13:00
Time projection chambers (TPCs) based on the ionization of cryogenic liquids are a prominent tool for neutrino oscillation, neutrinoless double beta decay, and dark matter experiments. Over the past two years I have pursued the development of a novel charge readout sensor providing true 3D imaging of particle interactions in large-scale liquid argon TPCs. The sensor must meet stringent requirements on noise (<600 electron), power (<100 microwatts per channel), and scalability (digital multiplexing of 100,000 channels per square meter), all at cryogenic temperatures. Such a scalable 3D micro-power sensor would enable operation of liquid argon TPCs in high-occupancy environments, such as the near detector site of the Deep Underground Neutrino Experiment (DUNE). I will present my recent mad dash to a successful demonstration of 3D micro-power imaging of particle tracks in liquid argon, and discuss what worked and what didn’t work along the way. I will also discuss the potential impact on upcoming neutrino measurements.

Shirley Li (SLAC) - DUNE as the next-generation solar neutrino experiment
2018-05-11 12:00 - 13:00 | 50A-5132- Sessler, 50A-5132 Sessler Conference Room, CA

Alexey Drobizhev (UCB/LBNL)
2018-05-18 12:00 - 13:00

No INPA Seminar This Week
2018-05-25 08:00 - 17:00

Ke-Jung (Ken) Chen (ASIAA) - The First Billion Years of the Universe - Rising Galaxies
2018-06-21 12:00 - 13:00 | 50A-5132- Sessler, 50A-5132 Sessler Conference Room, CA
One of the paramount problems in modern astrophysics is to understand the end of the cosmic dark ages when the first stars, supernovae, black holes, and galaxies transformed the simple early universe into a state of ever-increasing complexity. Modern cosmological simulations suggest that the hierarchical assembly of dark matter halos provided the gravitational wells that allowed the primordial gases to form stars and galaxies inside them. The first galaxies comprised of the first systems of stars gravitationally bound in dark matter halos are naturally recognized as the building blocks of early Universe. In this talk, I will discuss the physical mechanics behind the first galaxy formation and present the predictions of their observational signatures which will be examined by the future observatories such as JWST and TMT.

Jyoti Joshi (BNL) - Recent Results from MicroBooNE Liquid Argon TPC
2018-07-20 12:00 - 13:00, 2018-08-24 12:00 - 13:00 | 50A-5132- Sessler, 50A-5132 Sessler Conference Room, CA
MicroBooNE is a large (85-ton active mass) liquid argon time projection chamber (LArTPC) experiment operating near the surface at Fermilab in Batavia, Illinois. The detector observes neutrino interactions from the on-axis Booster Neutrino Beam (BNB) at short distance (470 m), enabling an investigation of the MiniBooNE low-energy excess as well as neutrino-argon cross section measurements. Another key purpose of the experiment is to gain experience with the operation and calibration of large LArTPC detectors in preparation for the SBN (Short Baseline Neutrino) program at Fermilab and DUNE (the Deep Underground Neutrino Experiment). We discuss the principal physics goals of MicroBooNE and highlight aspects related to operating a large LArTPC near the surface. The MicroBooNE LArTPC calibration program and different neutrino event reconstruction techniques are discussed, and recent results from the experiment are presented.

Chris Benson (UCB) - Using MiniCLEAN and measurements of microphysical material properties in the vacuum ultraviolet regime to inform next-generation dark matter and neutrino detectors
2018-08-17 12:00 - 13:00 | 50A-5132- Sessler, 50A-5132 Sessler Conference Room, CA
Single phase, zero-field, liquid noble gas scintillator detectors are a simple, scalable and cost-effective approach for dark matter and neutrino detection. MiniCLEAN is a liquid argon dark matter detector located 6,800 feet underground at SNOLAB in Canada. In addition to its role as a detector for dark matter searches, MiniCLEAN also serves as a technology demonstrator for a scalable, single-phase detector and is aimed at informing the design and sensitivity of monolithic, large-scale, next-generation dark matter and neutrino detectors. This presentation will provide an overview of the MiniCLEAN experiment and a summary of the author’s contributions to construction, commissioning, and analysis efforts. The results of a supporting wavelength shifting thin film R&D effort, a technology important to several current and future dark matter and neutrino experiments, will also be presented.

Arka Banerjee (Stanford) - Signatures of massive neutrinos on Large Scale Structure
2018-10-05 12:00 - 13:00 | 50A-5132- Sessler, 50A-5132 Sessler Conference Room, CA
Neutrino oscillation experiments have shown that there are at least two massive neutrino eigenstates, in a mass range that can produce observable signatures in current and future cosmological surveys. I will talk about the challenges and progress in correctly including the effects of massive neutrinos in N-body simulations of structure formation. Finally, I will talk about how these simulations can be used to study novel effects in massive neutrino cosmology – in particular, scale-dependent bias of nonlinear objects such as halos and voids on large scales.

Marco Raveri (UChicago)
2018-11-02 12:00 - 13:00 | 50A-5132- Sessler, 50A-5132 Sessler Conference Room, CA
TBA

Douglas Finkbeiner (Harvard) - Making neural net classifiers more robust and explainable: Lessons from Adversarial AI
2018-11-09 12:00 - 13:00 | 50A-5132- Sessler, 50A-5132 Sessler Conference Room, CA
As deep neural nets achieve ever greater successes, efforts to break them and learn about their failure modes are also ramping up. Security experts and malicious actors are interested in weaknesses per se, and we scientists are more interested in what we can learn about robustness to inputs somewhat different from training data. I will give examples of attacks and defenses, and talk about a measure of credibility at inference time.

Andrej Dvornik (UNLV) - KiDS and biases
2018-11-16 12:00 - 13:00 | 50A-5132- Sessler, 50A-5132 Sessler Conference Room, CA
The current ongoing large imaging surveys are an excellent tool for studying the origin and evolution of the Universe and the galaxy – dark matter connection, using the weak gravitational lensing as the main probe. Using the predicting power of the halo model formalism, the weak gravitational lensing (together with other large scale probes) can be used to constrain the origin of the scale dependence of the galaxy bias – the relation between the galaxies and the dark matter distribution, as well as studying the dependence of the formation time of galaxies on their halo masses – so called assembly bias. In this talk I will present the KiDS survey and way it can be used to shine a light on the different aspects of galaxy-halo connection.

Holiday
2018-11-23 12:00 - 13:00, 2019-01-04 12:00 - 13:00

Simon Foreman (CITA, Toronto) - Gravitational lensing of line intensity maps
2018-11-30 12:00 - 13:00 | 50A-5132- Sessler, 50A-5132 Sessler Conference Room, CA
Gravitational lensing of the cosmic microwave background (CMB) has emerged as a powerful cosmological probe, made possible by the development and characterization of nearly-optimal estimators for extracting the lensing signal from temperature and polarization maps. One can ask whether similar tools can be applied to upcoming “intensity maps” of emission lines at various wavelengths (e.g. 21cm). In this talk, I will present recent work in this direction, focusing in particular on the impact of nonlinear gravitational clustering on standard CMB lensing estimators when applied to intensity maps. I will show how these nonlinearities can provide a significant contaminant to lensing reconstruction, but will also describe how this contamination can largely be mitigated by modifying the lensing estimator. Finally, I will present estimates for the detectability of lensing in ongoing and future intensity mapping surveys, and highlight related work on reconstructing large-angle information in galaxy surveys and CMB maps.

Carlos García García (IFF, Madrid) - Theoretical priors for quintessence
2018-12-07 12:00 - 13:00 | 50A-5132- Sessler, 50A-5132 Sessler Conference Room, CA
Dark energy is a key unsolved problem. An enormous number of theories try to explain the accelerated expansion of the universe, ranging from the simplicity of a cosmological constant to the inclusion of new gravitational fields that affect space-time dynamics. We need clever methods to test the landscape of theories to make the most of next-generation experiments. I will present a novel framework to study dark energy and apply it to general quintessence models, reducing their functional freedom. Expanding the dark energy density as a truncated polynomial series, we are able to reproduce the observables with less than 1% error, with just 2 parameters. This economic yet precise description will allow dark energy to be constrained with next generation instruments in a general and efficient way.

Kimmy Wu (KICP Chicago) - Delensing, Neural Networks, the H_0 problem — a perspective from the CMB
2018-12-14 12:00 - 13:00 | 50A-5132- Sessler, 50A-5132 Sessler Conference Room, CA
The cosmic microwave background (CMB) contains a wealth of information about the early and the late universe. In this talk, I will focus on the search of primordial gravitational waves. Specifically, I will talk about “delensing” — constraining the lensing component in the CMB B-mode maps that we might reduce the soon-to-be major uncertainty of the r measurement in the BICEP/Keck experiments. For next-generation CMB experiments, we will need higher signal-to-noise estimates of the lensing potential beyond the commonly-used quadratic estimator approach today for delensing. I will discuss a method to extract the lensing field using a convolutional neural network (1810.01483), that approaches maximum-likelihood lensing estimates in a broad range of angular scales. If I have time, I will discuss the “H_0 problem”, where the inferred expansion rate of the universe from the CMB (and a couple other probes) are significantly lower than direct measurements. I will look at it from the sound horizon perspective (1811.00537) and show how data from the South Pole telescope can probe potential new physics.

Holiday - Shutdown
2018-12-21 12:00 - 13:00, 2018-12-28 12:00 - 13:00

Matt Shaw (JPL) - Silicon nanowire single photon detectors
2019-01-04 12:00 - 13:00 | INPA Common Room, 50-5026

Aleksandar Cikota (LBNL)
2019-01-11 12:00 - 13:00 | 50A-5132- Sessler, 50A-5132 Sessler Conference Room, CA

Silvia Scorza (Snolab, Sudbury) - Updates from SNOLAB
2019-01-18 12:00 - 13:00 | 50A-5132- Sessler, 50A-5132 Sessler Conference Room, CA
Astroparticle physics experiments searching for rare events, such as neutrinoless double beta decay and dark matter particles interactions, have to be shielded from background radiation that would interact and hide the physics of interest, and have to exhibit a radioactive background as low as possible. Therefore, underground site are preferred. Being protected from cosmic rays, the underground environment provides the conditions necessary for experiments dealing with such rare or exotic interactions.
SNOLAB is one such facility, based at a depth of 2km in the Vale Creighton mine near Sudbury, Ontario. The lab hosts a number of neutrino and dark matter experiments as well as new biology and genomic experiments making use of the unique facility.

NO INPA SEMINAR MTG
2019-01-25 12:00 - 13:00 | 50A-5132- Sessler, 50A-5132 Sessler Conference Room, CA

SPECIAL - Brittany Kamai (CalTech) - Looking further back with LIGO
2019-01-30 12:00 - 13:00 | INPA Common Room, 50-5026
Gravitational wave detectors require constant innovation in detector technology to meet the growing needs of the astrophysics community. With improved sensitivity, we can move beyond the measurements in the local universe and perform precision tests of cosmology. I will discuss our efforts to reduce the amount of low frequency noise within the LIGO detectors, which has a direct impact on our ability to measure heavier mass black hole mergers further out into the universe. I will focus on a proposed major upgrade to the LIGO detectors that will use silicon optics cooled to cryogenic temperatures. Additionally, I will discuss ideas for a passive seismic isolation system that uses advances in seismic cloaking technology. These improvements will extend distance measurements on gravitational wave mergers from the local universe out to much higher redshifts.

Hillary Child - Nonlinear Structure Formation at Two Scales: from Bispectrum Baryon Acoustic Oscillations to Evolution of Halo Profiles
2019-02-01 12:00 - 13:00 | 50A-5132- Sessler, 50A-5132 Sessler Conference Room, CA
The “cosmic web” of dark matter halos forms via the collapse of post-inflation density fluctuations. While linear perturbation theory describes this process well at large scales and low densities, it fails at small scales and high densities. I explore two facets of nonlinear structure formation that constrain cosmology: at mildly nonlinear scales, measuring the baryon acoustic oscillation (BAO) distance scale in the bispectrum, and at deeply nonlinear scales, tracking the evolution of simulated dark matter halo profiles.

At mildly nonlinear scales, the BAO distance scale constrains the expansion history of the universe and dark energy. The BAO feature has been detected in both the three-point correlation function and the bispectrum, but challenges remain in fully exploiting three-point data. I present a strategy to select triangle configurations that maximize the amplitude of the BAO signal in the bispectrum. A relatively small set of bispectrum measurements can improve constraints on the BAO length scale over power spectrum measurements alone.

I next turn to the internal structure of dark matter halos, whose formation is highly nonlinear. The spherically-averaged density of a halo is well described by the Navarro-Frenk-White (NFW) profile, a function of two parameters: concentration, which describes the density of the central region of the halo, and halo mass. These two parameters are correlated, and the resulting concentration-mass (c-M) relation is sensitive to cosmological parameters. I present a robust measurement of the c-M relation from the largest ever sample of simulated halos (~30 million) and track the evolution of individual halos to connect halo formation time and concentration.

Sinead Griffin (LBL) - Materials considerations for New Dark Matter Detectors
2019-02-08 12:00 - 13:00 | 50A-5132- Sessler, 50A-5132 Sessler Conference Room, CA
New discoveries in quantum information science and in dark matter detection rely on finding more sensitive detectors than those in state-of-the-art experiments. Traditional detector technologies, based on nuclear and electron scattering, have a lower bound on their sensitivity depending on the target’s mass and bandgap. We investigate two classes of new low-threshold detector target materials — Dirac electrons and optical phonons — using first-principles calculations. We discuss how the dark matter/target interaction can be optimized using chemical and physical engineering, and present the target reach for these new dark matter detection proposals.

Alexander Fieguth (Stanford) - Recent results of the Xenon-1t dark matter experiment
2019-02-15 12:00 - 13:00 | 50A-5132- Sessler, 50A-5132 Sessler Conference Room, CA
Beyond the Standard Model of particle physics there exists a form of matter, which seems to be dark in all interaction channels but in its gravitational influence. The nature of this major constituent of the universe is still not understood. The assumption that it is made up of particles which can possibly leave a trace in any detection channel is an established concept since decades.
Weakly Interacting Massive Particles (WIMPs) are one of the promising candidates for dark matter constituents. The hunt for a direct detection of a WIMP scattering off a target nucleus on earth is ongoing and pursued with larger efforts than ever before. Among different experiments, the dual-phase xenon time projection chambers are the most sensitive detectors for scatterings between WIMPs above a few GeV/c^2 and normal matter. The XENON1T experiment located at LNGS is such a detector. Using an exposure of one (tonne x yr) a null-result was obtained and this way the parameter space was probed down to a minimum of 4.1 x 10^(-47) cm^2 for a 30 GeV/c^2 WIMP at 90% C.L. A crucial aspect behind its sensitivity is the mitigation and understanding of background sources mimicking a WIMP signal. Notably, the rate of electronic recoils in the detector (82^(+5)_(−3) (sys.) ± 3 (stat)) events/(tonne×yr×keV) is the lowest achieved in any dark matter detector.
An introduction to the general direct detection principle will be given in this talk. Furthermore, the experimental picture of direct dark matter search will be introduced with a focus on the results from the XENON1T experiment. In addition, an outlook on recent efforts to open up for scenarios beyond the vanilla dark matter search, e.g. the interaction of WIMPS purely with pions within the nucleus, will be included. Finally, an insight into the possibilities a large liquid xenon low background detector offers for physics channels beyond the dark matter search will be given.

Jia Liu (Princeton) - Nonlinear cosmology with massive neutrinos
2019-02-22 12:00 - 13:00 | 50A-5132- Sessler, 50A-5132 Sessler Conference Room, CA
The non-zero mass of neutrinos suppresses the growth of cosmic structure on small scales. Since the level of suppression depends on the masses of the three active neutrino species, the evolution of large-scale structure is a promising tool to constrain the total mass of neutrinos and possibly shed light on the mass hierarchy. I will discuss recent progress and future prospects to constrain the neutrino mass sum with cosmology, with a focus on the nonlinear regime.

Dr. Quentin Riffard (LBL) - Direct detection of Dark Matter: from LUX to LZ
2019-03-01 12:00 - 13:00 | 50A-5132- Sessler, 50A-5132 Sessler Conference Room, CA
Liquid xenon two-phase time projection chamber (TPC) is one of the most promising technologies for WIMP dark matter direct detection. By using this technology, the LUX, XENON1T, and PANDAX-II collaborations established the most stringent limits on WIMP-nucleus cross section above 10 GeV. For WIMP searches, the expected signal is composed of nuclear recoils (NR), while our background is composed by both electron recoils (ER) and NR. The limits on the WIMP-nucleus cross section are extracted using a Profile Likelihood Ratio (PLR). The usage of the PLR requires a precise knowledge of signal and background models. In the first section, I will focus on the improvement of the detector response modeling and the re-analysis of the background model for LUX Run4 analyses. The LUX Run4 represents a challenge for the modeling of the detector response as several experimental parameters vary as a function of time. Then I will present a new detector response model based on the NEST yield model to consider those variations. This new model has been tuned on Run4 calibration data across many electric fields. After the decommissioning of the LUX experiment, some parts of the detector have been re-assayed to reevaluate the activity of the contaminants. I’m developing a new background model based on a Monte-Carlo simulation of the detector and those new measurements. Once achieved, this background model will be used in future analyses. I used the new detector response model to test the impact of the electric field and the light collection efficiency on detector sensitivity for several dark matter models.
Among few collaborations, the LUX-ZEPLIN (LZ) is currently building one of the next generation of dark matter detector. The NR response detector calibration is a fundamental aspect of dark matter searches. I am involved in development of a photo-neutron source for the low energy NR calibration of the detector. By using a Monte-Carlo simulation, we determined the expected event rate. Moreover, by using photo neutron simulations, I also identify a plausible low energy calibration source. After Xe neutron capture, we have the emission of very high energy gammas ~ 9 MeV and a ~300 eV NR. In some case only the NR is visible as the gamma can escape the LXe without depositing any energy. By using the veto to tag this neutron capture reaction, I show that we have a new possible low energy NR internal calibration source.
