INPA

Kimmy Wu (KICP Chicago) - Delensing, Neural Networks, the H_0 problem — a perspective from the CMB
2018-12-14 12:00 - 13:00 (America/Los_Angeles) | 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.

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.

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.

Holiday
2018-11-23 12:00 - 13:00

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.

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.

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

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.

Jyoti Joshi (BNL) - Recent Results from MicroBooNE Liquid Argon TPC
2018-08-24 12:00 - 13:00, 2018-07-20 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.

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.

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

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

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

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.

Rebecca Canning (Stanford) - Understanding Active Galactic Nuclei (AGN) in the most massive cosmic laboratories
2018-04-20 12:00 - 13:00 | 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.

Heidi Newberg (RPI) - Dwarf galaxies and dark matter in the Milky Way
2018-04-17 17:00 - 18:00 | 50A-5132- Sessler, 50A-5132 Sessler Conference Room, CA
In the past fifteen years, dozens of tidal streams of stars pulled from dwarf galaxies and globular clusters have been discovered in the Milky Way’s stellar halo. Recently, it has been discovered that as the dwarf galaxies fall into our galaxy they perturb the stars in the disk, causing wavelike disturbances that are seen in the densities and velocities of disk stars. These disturbances could be driving force behind spiral structure in galaxies. MilkyWay@home is a petaFLOPS scale volunteer computing platform that is mapping the densities of stars in the larger tidal streams in the stellar halo and using that information to measure the mass and density profile of both the stars and the dark matter in the progenitor dwarf galaxies, using only information from the stars in the tidal streams. Eventually, MilkyWay@home will fit the shape of the Galactic potential using tidal streams.

Helion Mas du Bourboux ( University of Utah) - Baryonic Acoustic Oscillations in SDSS and DESI using the intergalactic medium absorption
2018-04-13 12:00 - 13:00 | 50A-5132- Sessler, 50A-5132 Sessler Conference Room, CA
We present the measurement of the Baryonic Acoustic Oscillation (BAO) scale from the correlation between absorption in the intergalactic medium and the positions of galaxies and quasars in the SDSS data and in the desi simulations.
We use the absorption by neutral Hydrogen and by Magnesium-II observed in quasar spectra to trace the underlying matter density fluctuations. Combined with galaxies and quasars, these two tracers allow to measure the 3d cross-correlation of matter from a redshift of z = 0.5 up to a redshift of z = 2.4.

Vincent Fischer (UC Davis) - Accelerator Neutrino Neutron Interaction Experiment (ANNIE)
2018-04-06 12:00 - 13:00
The next generation of large scale neutrino detectors, such as DUNE or Hyper-Kamiokande, will heavily rely on a precise understanding of neutrino-nucleus interactions to reach their goal of measuring leptonic CP violation. Accounting for and reconstructing all final state particles, especially neutrons, created upon such interactions is thus crucial. This is the goal of the ANNIE experiment: Measuring the neutron abundance in the final state of neutrino-nucleus interactions in the energy domain relevant for oscillation experiments. With a volume of about 30 tons of pure water doped with gadolinium to enhance neutron tagging efficiency, ANNIE will provide a measurement of the neutron yield of neutrino interactions as a function of the neutrino energy in the well-characterized Booster Neutrino Beam at Fermilab. The modularity of ANNIE will allow it to perform the very first live test of a novel kind of photodetectors called LAPPDs (Large Area Picosecond Photodetectors) in a neutrino detector to reconstruct neutrino interaction vertices through precision timing measurement. This seminar will describe the design and construction of the experiment, along with the background measurement results from Phase~I and the plans for Phase~II.

Dr. Leila Haegel (University of the Balearic Islands, Spain) - Testing general relativity with gravitational waves
2018-03-26 12:00 - 13:00 | 50A-5132- Sessler, 50A-5132 Sessler Conference Room, CA
Gravitational waves have been directly detected by the LIGO experiment in 2015. Since then, five black holes and one neutron star binaries merging have been observed during the two observational runs. The measured signals already provided a large amount of physical results, from the mass distribution of stellar-masses black holes to the short gamma-ray burst mechanisms through measurement of the expansion rate of the Universe and tests of general relativity. Both detection and analysis of gravitational waves rely on the simulation of the expected signal to be extracted from the noise. As the exact computation of gravitational waveforms is a computationally expensive resource, physicists are building phenomenological models. I will review the process of designing such models as well as their impact on the physics extracted from the signals.

Krista Lynne Smith (Stanford) - A New Regime of Optical Variability in AGN: Light Curves from Exoplanet Satellites
2018-03-23 12:00 - 13:00
The optical light curves of AGN provide a unique window into the conditions and behavior within the accretion disk. The development of a specialized pipeline for AGN science with the unparalleled photometry of exoplanet-hunting satellites allows us to explore new optical variability phenomena. Such data provide an opportunity for direct comparison with X-ray light curves, and promise to inform models of both accretion physics and the relationship between X-ray and optical emitting regions in the central engine. These data will be critical in learning how to interpret AGN light curves from upcoming large variability surveys like LSST. Finally, exoplanet mission data have enormous future promise for a multifaceted understanding of accretion processes, including blazar jets and quasi-periodic oscillations.

Ana Bonaca (Harvard-CfA) - What are the tidal streams constraining?
2018-03-16 12:00 - 13:00 | 50A-5132- Sessler, 50A-5132 Sessler Conference Room, CA
Cold stellar streams, remnants of tidally disrupted globular clusters, have been employed as exquisite tracers of dark matter in the Milky Way. Because of their different positions in phase space, different ages, and different levels of observational scrutiny, different streams tell us different things about the Galaxy. We employ a Cramer–Rao or Fisher-matrix approach to understand the quantitative information content in the known streams. In simple, static, analytic models of the Milky Way, streams on eccentric orbits contain the most information about the dark-matter shape. For any individual stream, there are near-degeneracies between dark-matter halo properties and parameters describing the Galactic bulge, disk and the stream progenitor itself, but we find that simultaneous fitting of multiple streams ought to constrain all parameters to a precision of a few percent. At this level, simulated dark matter halos deviate from analytic parametrizations, so we chart the way forward by discussing constraints streams place on more flexible models of the Galactic gravitational potential.

Giorgia Pollina - Unveiling cosmic voids in large-scale structure surveys: the impact of tracer bias
2018-03-09 12:00 - 13:00 | 50A-5132- Sessler, 50A-5132 Sessler Conference Room, CA
The large-scale structure of the Universe can only be observed directly via luminous tracers of the underlying matter density field. However, luminous tracers, such as galaxies, do not precisely mirror the clustering statistic of the bulk of the cold dark matter distribution: their correlation function (or power spectrum) is biased and depends on various properties of the tracers themselves. Although on small scales this bias is an unestablished function of space and time, on very large scales it results in a constant offset in the clustering amplitude, known as linear bias. In this talk we focus on the bias of luminous objects within and around cosmic voids, enormous under-dense regions of the Universe that occupy the vast majority of its volume. As a remarkable result, we find that, within voids, the relation between matter and galaxy density is always linear and determined by a multiplicative constant. Furthermore, the value of this constant decreases with the increase of the size of voids and asymptotes to the linear bias. This result opens to the possibility of using such simple relation in other voids studies, allowing to extend our theoretical understanding of voids (typically defined as depressions in the matter density field) to voids that are identified using galaxies as tracers of the matter density. Ultimately we aim to test these findings with observations, using the Dark Energy Survey data currently available.

Andre Walker-Loud (LBNL) - Lattice QCD for Neutrinoless Double Beta Decay
2018-03-02 12:00 - 13:00 | 50A-5132- Sessler, 50A-5132 Sessler Conference Room, CA
In recent years, lattice QCD has matured to the stage where it is now routine for calculations to be performed at or near the physical pion mass, with fully controlled extrapolations to the continuum and infinite volume limits. These calculations are predominantly related to flavor physics and heavy quark physics. The application of lattice QCD to nuclear physics is beset by a number of additional challenges which make them exponentially more expensive, prohibiting the same success so far for low-energy nuclear processes. Algorithmic improvements and the computing power of the next generation supercomputers promises an era in which we will be able to make rigorous, fully controlled calculations of basic nuclear properties. I will briefly introduce lattice QCD and describe the challenges in applying it to basic nuclear physics. I will then highlight some recent results and outline a strategy for connecting complex, exotic phenomena such as neutrinoless double beta decay to the fundamental theory of nuclear strong interactions, Quantum Chromodynamics. aim to test these findings with observations, using the Dark Energy Survey data currently available.

Dan Wilkins (Stanford) - Seeing to the Event Horizons of Supermassive Black Holes
2018-02-23 12:00 - 13:00 | 50A-5132- Sessler, 50A-5132 Sessler Conference Room, CA
From the reflection and reverberation of X-rays off the innermost regions of AGN accretion discs, a three-dimensional picture is starting to emerge of the extreme environments around supermassive black holes in which intense X-ray emission is produced and jets are launched at close to the speed of light.

Recent advances in the analysis of the X-ray emission and its variability in AGN, observed by the great X-ray observatories, coupled with general relativistic ray tracing simulations, have revealed vast amounts of information about the extreme environments in the immediate vicinity of the black hole event horizon. The effects of general relativity on the reflected emission can be exploited to pinpoint the location of reflection in the strong gravitational field, while time delays in the X-ray echoes off the accretion disc enable the structure of the innermost regions to be mapped.

We discover how the X-ray emitting corona evolves on long and short timescales, giving rise to orders of magnitude variation in luminosity as well as the processes the corona can undergo during transient events, most notably the collimation and ejection of portions of the corona during X-ray flares, reminiscent of the aborted launching of a jet. The latest X-ray reverberation studies are revealing, for the first time, structure within the corona including a persistent collimated core akin to the base of a jet, even in radio-quiet sources, alongside a second component associated with the accretion disc itself.

This gives us important insight into the small-scale processes close to the event horizon that enable supermassive black holes to power some of the most luminous objects in the Universe, launch vast jets and play their important role in the formation of structure in the Universe.

Samuele Sangiorgio (Lawrence Livermore National Laboratory) - Neutrinoless Double Beta Decay with nEXO: Experiment Concept, R&D, and Sensitivity
2018-02-16 12:00 - 13:00 | 50A-5132- Sessler, 50A-5132 Sessler Conference Room, CA
The next-generation Enriched Xenon Observatory (nEXO) is a proposed experiment to search for neutrinoless double beta (0νββ) decay whose observation would imply lepton number violation and confirm the existence of elementary Majorana fermions. nEXO searches for 0νββ in 136 Xe with a target half-life sensitivity of approximately 10 28 years using 5×10 3 kg of isotopically enriched liquid-xenon in a time projection chamber. This improvement of two orders of magnitude in sensitivity over current limits is obtained by a significant increase of the 136Xe mass, the monolithic and homogeneous configuration of the active medium, and the multi-parameter measurements of the interactions enabled by the time projection chamber. This seminar will introduce nEXO’s detector concept, present the R&D activities, and discuss the anticipated performance based upon demonstrated realizable background rates.

Special - Danielle Leonard (CMU) - Measuring the scale-dependence of intrinsic alignments using multiple shear estimates
2018-02-12 12:00 - 13:00 | 50A-5132- Sessler, 50A-5132 Sessler Conference Room, CA
The next generation of cosmological surveys promises significant advancements in the field of weak gravitational lensing. As such, it is crucial that relevant systematic effects such as the intrinsic alignment of galaxies are well-understood. I will discuss a new method for measuring the scale-dependence of the intrinsic alignment contamination to the galaxy-galaxy lensing signal, which takes advantage of multiple shear estimates applied to the same data set. For a galaxy-galaxy lensing measurement which uses LSST sources and DESI lenses, the signal-to-noise on the intrinsic alignment signal measured by our method is forecast to improve on an existing method (Blazek et al. 2012) by a factor of >2, for optimally chosen pairs of shear estimates.

Wing Yan Ma (Imperial College London) - Recent Neutrino Oscillation Results from T2K
2018-02-09 12:00 - 13:00 | 50A-5132- Sessler, 50A-5132 Sessler Conference Room, CA
T2K is a long baseline neutrino experiment situated in Japan. A muon neutrinos and antineutrinos beam is produced and fired 295km across the country and observed using the 50 kTon Super Kamiokande detector. By studying how many of these neutrinos have oscillated into different flavours and whether the oscillations occur differently for antineutrinos we have sensitivity to CP violation in the neutrino sector. I will present the latest results of the neutrino oscillation measurements using data collected up to May 2017, including new limits on the CP violating parameter δCP.

Jason Bono (Fermilab) - Muon Anomalies and Their Future Investigations
2018-02-02 12:00 - 13:00 | 50A-5132- Sessler, 50A-5132 Sessler Conference Room, CA
The muon is 200 times heavier than the electron and still lighter than any hadron, which make it’s interactions, at once, potentially sensitive to undiscovered phenomena, and predictable to high precision within the Standard Model. The muon’s ease of production, natural polarization and self analyzing decay, and comparatively long lifetime also allow for extremely high precision measurements of fundamental constants and interactions. Muons thus offer a unique probe to search for physics beyond the Standard Model.
This discussion will first elaborate on some of the experimental and theoretical niceties of the muon, and briefly look at the particle from a historical perspective, emphasizing a few of the many important roles that it’s played in piecing together our current understanding of particle physics. We will then look at a variety of anomalies in experiments using muons, which, taken together may suggest the possibility of sensitivity to new physics within reach of future experiments, some of which will also be looked at. Topics include recent developments in the proton radius puzzle, the muon anomalous magnetic moment, hints of lepton flavor non-universality in B decays, and searches for charged lepton flavor violation. For fun, a recent discovery in the Great Pyramid of Giza using muon tomography will also be discussed.
