List of past INPA Seminars — 2017

Jan 13, 2017

Initial results from the Majorana Demonstrator – By Alan Poon – LBNL

Neutrinoless double-beta decay experiments play a major role in the search for lepton number violation and the Majorana nature of the neutrino mass. The MAJORANA Collaboration has assembled two modules of high-purity Ge detectors to search for neutrinoless double-beta decay in 76-Ge at the Sanford Underground Research Facility in Lead, South Dakota. One of the primary goals of the MAJORANA DEMONSTRATOR (MJD) is to establish the required background and scalability of a Ge-based, next-generation, tonne-scale experiment. Commissioning of MJD started in 2015 and its two detector modules are taking data. I will discuss the initial results on the search for neutrinoless double-beta decays and dark matter from the commissioning run and the first physics run of Module 1.

Jan 20, 2017

Marcelo Alvarez -Simulating Large Scale Structure Observables from Reionization to the Present

The next generation of large scale structure surveys will map out the universe in unprecedented detail. Transformative techniques in computational astrophysics are emerging as the optimal ways to extract information from these surveys, with realistic and routine full sky simulations finally within reach. I will describe a new pipeline for efficiently simulating high resolution maps of the sky from the radio to x-ray and from reionization to the present. I will conclude with what questions are likely to be answered in the next decade.

Feb 03, 2017

Benjamin Schmidt (LBNL) – CUORE Commissioning

Feb 17, 2017

Scott Daniel (University of Washington) – Deterministic \chi^2 Exploration to Find Credible Limits Faster than by Bayesian Sampling

Once data has been collected, it is desirable to be able to quickly transform that data into statements about the values and corresponding uncertainties — the “confidence limits” or “credible limits” — of the physical parameters underlying the data. Traditionally, this problem is treated probabilistically. This process can be time consuming, as enough samples need to be drawn that the distribution of samples converges to the Bayesian posterior distribution of the likelihood in parameter space. We propose an alternative scheme based on the likelihood ratio test, minimizing a cost function that incentivizes exploration of parameter space points within the credible limit but far from previously explored points. Testing on toy likelihood functions with realistic non-Gaussian properties, we find that this scheme converges to the same credible limit as the usual Bayesian methods but requires an order of magnitude fewer evaluations of the likelihood function. Our code is publically available over GitHub.

Feb 24, 2017

Raul Hennings Yeomans (UCB)

Recent progress on the next generation double beta decay experiment with low-temperature macro-calorimeters (CUPID)

The Cuore Upgrade with Particle IDentification, or CUPID, is a proposed next generation double-beta decay experiment that requires a low-threshold optical photon light detector. The use of a secondary bolometer as a light detector is being investigated since, $\alpha$-particles (the main background of CUORE-0) could be tagged by comparing the heat and light signals for each event, given that the two betas from a neutrinoless double beta event would produce both heat and light (Cherenkov light in the case of TeO$_2$) while $\alpha$ events would produce only heat in the absorber. A baseline resolution of at least 20~eV is required in order to achieve a rejection factor of 99.9\% of the $\alpha$ background. I will review latest progress on CUPID, particularly the development of low-Tc superconducting Transition Edge Sensor technology.

Feb 27, 2017

Lauren Ice (ASU) – Measurement of the Two-Photon Exchange Contribution to Elastic Lepton-Proton Scattering with the OLYMPUS Experiment

The OLYMPUS experiment measured the two-photon exchange contribution to elastic electron-proton scattering, which is thought to be the most likely candidate to resolve the discrepancy observed between polarized and unpolarized measurements of the proton electric-to-magnetic form factor ratio. To deterimine the two-photon exchange contribtuion, OLYMPUS measured the positron-proton to electron-proton elastic scattering cross section ratio over a wide range of four-momentum transfer from 0.6 < Q2 < 2.2 (GeV/c)2 and virtual photon polarizaton from 0.456 < ? < 0.978. The two-photon exchange contribution is correlated to the deviation of the cross section ratio from unity.

In 2012, the OLYMPUS experiment collected over 4 fb?1 of e+p and e?p scatter-ing data using electron and positron beams incident on a hydrogen gas target. The scattered leptons and protons were measured exclusively with a large acceptance spec-
trometer. OLYMPUS observed a slight rise in ?e+p/?e?p of at most 1-2% over the Q2 range. This talk will discuss the motivations, experiment, analysis method, and the preliminary results for the cross section ratio as measured by OLYMPUS.

Mar 03, 2017

Martina Gerbino (NORDITA) – Three Neutrinos in Cosmology (to Say Nothing of Laboratory)

Neutrinos are the only standard model particles of unknown mass. Thus, measuring their mass is one of the leading goals in fundamental physics. Cosmology currently provides the tightest bounds on the sum of the neutrino masses and the possibility that next generation experiments can provide a detection looks promising. Then, further questions would have to be addressed, such as the neutrino hierarchy and the neutrino nature. In this talk, I will discuss the treasure trove of information about massive neutrinos that we can collect from different cosmological probes. I will stress the importance of extending our interest to laboratory searches, such as kinematic measurements and neutrino less double-beta decay experiments, for going beyond measuring the neutrino mass. Finally, I will choose a different angle and show how massive neutrino unknowns can affect the constraints on inflationary models.

Mar 10, 2017

Sandra Miarecki – Earth vs. Neutrinos: first measurements of neutrino absorption in the Earth and the muon neutrino-to-nucleon cross section above 1 TeV with the IceCube Detector


Sandy Miarecki is a retired Air Force test pilot, PhD graduate of the University of California-Berkeley, and an affiliate member of LBL after completing her dissertation research at LBL. She is currently an assistant professor of physics at the US Air Force Academy in Colorado Springs.

The IceCube Detector at the South Pole was constructed to measure the flux of high-energy neutrinos and to try to identify their cosmic sources. In addition to these astrophysical neutrinos, IceCube also detects the neutrinos that result from cosmic ray interactions with the atmosphere. These atmospheric neutrinos can be used to measure the total muon neutrino-to-nucleon cross section by measuring neutrino absorption in the Earth for the first time. The measurement involves isolating a sample of 10,784 Earth-transiting muons detected by IceCube in its 79-string configuration. The cross-section is determined using a two-dimensional fit in measured muon energy and zenith angle and is presented as a multiple of the Standard Model expectation as calculated by Cooper-Sarkar, Mertsch, and Sarkar in 2011. A multiple of 1.0 would indicate agreement with the Standard Model. The results of this analysis find the multiple to be 1.30 (+0.21 -0.19 statistical) (+0.40 -0.44 systematic) for the neutrino energy range of 6.3 to 980 TeV, which is in agreement with the Standard Model expectation.

Mar 13, 2017

Quentin Riffard – Direct detection of dark matter with the DarkSide program

A large number of astrophysical and cosmological observations at different scales supports the existence of a cold dark matter component in the Universe. At the Universe scale, this component is uniformly distributed and represents roughly 26% of the total mass-energy density of the Universe. The Weakly Interacting Massive Particle (WIMP), a generic particle, is one of the leading dark matter particle candidates: a massive particle interacting only through weak and gravitational interactions. This candidate is supported by the so-called “WIMP miracle” and could also be supported in particle physics by supersymmetric models. At the Milky Way scale, dark matter forms a static halo surrounding our galaxy. The relative motion of the solar system through the dark halo produces a flux of WIMP on Earth. Through the weak interaction, WIMP could interact with ordinary matter producing nuclear recoils (NR) by elastic scattering. In the last two decades, a large experimental effort has been deployed by international collaborations in order to probe a direct detection of NR from WIMP-nucleus interactions. In this experimental context, multi-tone noble liquid TPC are good candidate for the dark matter searches. The DarkSide program is a step approach program aiming to build a large TPC filled with liquid argon (LAr). The first part of this presentation focuses on the potential of LAr as a target for dark matter searches, on the latest results from the DS-50 detector and the perspectives of the DarkSide program: the DS-20k detector. For a complete understanding of LAr data, the characterisation of several parameters is fundamental such as the scintillation efficiency for NR and the pulse-shape parameter for the NR/ER discrimination is fundamental. In order to improve the knowledge on these parameters, the ARIS collaboration built a small LAr double-phase TPC. A first data taking with mono chromatic neutrons was performed in Orsay (France) in last October. The second part of this presentation presents a status of the ARIS data analysis and a discussion of the strategy to extract the parameters.

Mar 17, 2017

Jessie Muir (Michigan) – Unbiasing cosmology on the largest scales

One of the most exciting areas of research in cosmology is the effort to extract information about fundamental physics from observations of the universe on large scales. With the advent of increasingly large cosmological datasets (and correspondingly small statistical uncertainties), future progress in the field will fundamentally be determined by our ability to understand and account for systematic errors. In this talk, I’ll discuss two projects which further that ability: a study of how reliably we can separate primordial and late-time contributions to large-angle features of the the Cosmic Microwave Background (CMB) and the development of a blinding strategy to prevent experimenters’ bias from influencing the Dark Energy Survey’s cosmological analysis.

Mar 24, 2017

Bradford Welliver (LBNL) – Results and Current Status of the SuperCDMS Soudan Experiment

The SuperCDMS experiment is a dark matter search that utilizes an array of 15 patterned Ge crystals, called iZIPs with a total mass of 9kg. SuperCDMS has completed operations at the Soudan Underground Laboratory and reported results on low-mass (M 10 GeV/c^2) WIMP search analysis with 1700 kg-days of exposure using 10 of the iZIP detectors is nearing completion. This talk will present an overview of the SuperCDMS detector technology, recap the low-mass search results and discuss the analysis strategy and status of the high mass WIMP search.

Apr 07, 2017

Pierre Sokolsky (Utah) – Ultra-High Energy Cosmic Rays: Complex Spectral Structure and Evidence for Anisotropy in the Northern Sky

We present recent results from the Telescope Array (TA) collaboration on the spectrum and anisotropy of cosmic rays from 1015 to 1020 eV. The simple power law spectrum thought to be exhibited by cosmic rays is now known to be considerably more complex, with at least four features present in this energy region in addition to the spectral cut-off at 5×1019 eV. The evidence for these structures and their possible origin will be discussed. At the highest energies, a clustering of events ( a “hot spot”) is observed in the neighborhood of Ursa Major with a 3.4 to 4.0 sigma significance ( depending on methodology). If confirmed, this would be the first significant observation of a ultra-high energy cosmic ray source. The “hot spot” is consistent with originating from M82, a nearby starburst galaxy.

Apr 14, 2017

Samuel Flender (ANL) – Cosmology and the Sunyaev-Zel’dovich sky: Observations and simulations

The Sunyaev-Zel’dovich (SZ) effect is an important observational signature of galaxy clusters, the largest objects in the Universe today. In particular, the pairwise kinematic SZ signal probes the matter-velocity correlation function, scaled by the average optical depth of galaxy clusters, and is thus an interesting probe both from a cosmological and astrophysical point of view. In this talk, I will give an overview about our current cosmological understanding, highlighting the role of the SZ effect. I will present the current landscape of kinematic SZ measurements, including a recent measurement by the South Pole Telescope collaboration and the Dark Energy Survey collaboration, as well as insights from new, state-of-the-art simulations, and recent progress in the modeling of gas profiles of galaxy clusters.

Apr 21, 2017

Ken Chen (NAOJ) – Lighting up the Universe with Extreme Supernovae

Recent all-sky transient searches have discovered new and unexpected explosion types that fall outside traditional SN classification schemes. These exotic outliers in many cases are due to the deaths of massive stars and therefore may have been prevalent in the primordial universe because the Pop III IMF is thought to be top-heavy. Depending on the mass of the progenitor, these outliers may be faint, magnetar-powered, pair-instability, or general relativistic instability SNe, all of which have unique observational signatures. Some of these events are superluminous, 10-100 times brighter than normal supernovae, and may produce energetic UV, X-ray, or gamma-ray bursts. Their extreme luminosities enable their detection at z > 10 and they are ideal probes of the primordial universe at cosmic dawn, prior to the advent of the first galaxies. Here, we examine these exotic explosions with state of the art 3D radiation-hydro simulations that bridge all spatial scales from the central engine to breakout into the IGM, where observational signatures can be computed. We discuss the coevolution of radiation and turbulent mixing in SN ejecta and present realistic light curves for these explosions for JWST and the coming generation of extremely large telescopes (ELTs). Detection rates for Pop III SNe can place useful constraints on the primordial IMF, and their nucleosynthetic yields can be used to study the chemical compositions of extreme metal poor stars.

Apr 28, 2017

Javier Caravaca Rodriguez (UCB) – Cherenkov and Scintillation light separation with the CHESS experiment

The first step toward construction of a hybrid optical detector like THEIA is the demonstration of separation of scintillation and Cherenkov light in liquid scintillators (LS). This would allow reconstruction of particle directionality in a low energy threshold detector, and provide improved particle identification. The CHESS experiment successfully images Cherenkov rings on LS such as LAB and LAB with PPO, demonstrating this separation. Despite the relatively high light yield of the scintillation light with respect to the Cherenkov light, the latter is successfully identified thanks to the characteristic prompt emission time of a few picoseconds, as oppose to the typical nanoseconds delays of the scintillation emission. Low time jitter PMTs ($\sim300ps$) and fast digitization ($5GHz$) provides a precision well below the nanosecond level, making the time separation possible. Recent results obtained with pure LS and preliminary studies for newly developed water-based LS materials will be presented.

May 05, 2017

Daniel Dwyer (LBNL) – Evidence against sterile neutrinos from the Daya Bay Experiment

Prevailing models of antineutrino emission by nuclear reactors do not
agree with observations. This discrepancy has been considered
possible evidence for neutrino oscillation to non-interacting, or
sterile, neutrino states. Although the existence of sterile neutrinos
would have profound implications, a variety of measurements by the
Daya Bay Experiment disfavor sterile models. I will summarize these
observations with a particular focus on the latest result: a precise
measurement of the antineutrino flux versus reactor fuel burn-up.
I’ll wrap up with a provocative question: does any compelling evidence
for sterile neutrinos remain?

May 12, 2017

Jessica Lu (UCB) – New Developments in Adaptive Optics: Wide Fields and Precise PSFs

Adaptive optics correct for the blurring effects of the Earth’s atmosphere. However, most AO systems today suffer from limited fields of view and point spread functions that vary over time and position. I will present results from several experiments to overcome these limitations. We have deployed a ground-layer adaptive optics experiment on the UH 2.2 m telescope on Maunakea to test the AO image quality over fields of view as large as 20 arcminutes. This experiment is a key first step in understanding whether a GLAO system would be feasible for other 8-10 m telescopes equipped with wide-field multi-object spectrographs. We are currently investigating the science feasibility of such a system for Keck. I will also present our efforts to reconstruct the AO point spread function and deliver more precise scientific measurements from Keck’s narrow-field AO system. Initial science applications include close binaries, quasar host galaxies, and the Galactic Center. Future cases include strongly lensed galaxies and supernovae, black hole hunting with astrometric microlensing, and direct imaging of exoplanets.

May 19, 2017

Jon Ouellet (MIT) – ABRACADABRA: A New Approach to the Search for Axion Dark Matter

The evidence for the existence of Dark Matter is well supported by
many cosmological observations. But we have not yet been able to
determine how this new type of matter fits into our understanding of
the Universe on the smallest scales. Separately, long standing
problems within the Standard Model point to new weakly interacting
particles to help explain away unnatural fine-tunings. The axion was
originally proposed to explain the Strong-CP problem, but was
subsequently shown to be a strong candidate for explaining the Dark
Matter abundance of the Universe. ABRACADABRA is a proposed
experiment to search for ultralight axion Dark Matter, with a focus on
the mass range $10^{-14} \lesssim m_a \lesssim 10^{-6}$\,eV. We search
for these axions and other axion like particles (ALPs) through a
modification to Maxwell’s equations, which cause strong magnetic
fields to source weak oscillating electrical currents parallel to the
field. These weak currents can be detected through the magnetic fields
that they generate. To see these, ABRACADABRA will use highly
sensitive SQUID magnetometers in a very low noise environment. At
MIT, we are building a 10\,cm scale prototype that will quickly be
sensitive to untested regions of parameter space. In the long term, we
hope to scale ABRACADABRA to a 1\,m$^3$ scale detector, which could be
sensitive enough to probe the QCD axion scale.

May 26, 2017

Titouan Lazeyras (MPA) – Dark matter halo bias from separate universe sim-ulations

The large-scale local bias parameters of dark matter halos are essential to
describe the statistics of halos and galaxies on large scales, as well as for
the halo model of the matter distribution. Using so-called separate universe
simulations, we recently obtained precise measurements of the three leading
bias parameters. For b2 and b3, these are the most precise measurements
to date. We compare our results with bias parameters obtained from two
and three points cross-correlation functions and with theoretical predictions
from the excursion set peaks (ESP) model.
Using the same set of simulations, we further investigate halo assembly bias,
i.e. the dependence of the halo bias on properties other than the halo mass.
We focus on four halo properties : halo concentration, spin, ellipticity and
mass accretion rate. We measure assembly bias for b1 and nd good agree-
ment with previous studies. Furthermore, we present results for assembly
bias in b2 which are among the rst ones and most precise to date. To try
and better understand the physical mechanisms behind assembly bias, we
also look at the joint dependence of bias on two halo properties in addition
to the mass.

Jun 02, 2017

Jose Ezquiaga (UAM) – Testing dark energy and gravity with the speed of gravitational waves

LIGO’s gravitational waves (GWs) detection has inaugurated an era to test the foundations of gravity. This includes also probing the nature of Dark Energy. Theories explaining the present acceleration of the Universe beyond the cosmological constant typically require adding extra gravitational degrees of freedom. This can lead to distinct signatures in the propagation of GWs. I will review current tests of gravity over different scales and regimes, and examine different frameworks describing dynamical dark energy. Then, focusing on the case of only one additional degree of freedom, I will present how the speed of GWs could be used to place severe constraints on generic scalar-tensor theories of gravity. I will describe under which circumstances an anomalous propagation speed can arise, and how it could be measured in the near future. If there is a small deviation from the speed of light, the delay between the GW and any electromagnetic counterpart will run beyond human time scales. Still, this measurement could be achieved with LISA using eclipsing white dwarf binaries. This test will either eliminate many contender models for cosmic acceleration or wreck a fundamental pillar of general relativity.

Jun 09, 2017

Giovanni Benato (LBNL) – Discovery probability of next-generation neutrinoless double-? decay experiments

Neutrinoless double beta (0???) decay is the only process which can feasibly investigate the
Majorana nature of neutrinos and total lepton number conservation.
A broad international experimental program requiring considerable resources is being mounted to search for 0??? decay in the region of parameter space allowed for Inverted Ordering.
The Bayesian discovery probability of future experiments searching for 0??? decay is evaluated.
A Bayesian global fit is performed to construct a probability distribution for the effective Majorana mass, the observable of interest for these experiments. This probability distribution is then combined with the sensitivity of each experiment derived from a heuristic counting analysis. The discovery probability strongly depends on whether the neutrino mass ordering is normal or inverted, and is found to be higher than previously considered for both mass orderings. In the absence of neutrino mass mechanisms that drive the lightest state or the effective Majorana mass to zero, for the inverted ordering next-generation experiments are likely to observe a signal already during their first operational stages. Even for the normal ordering, the probability of discovering neutrinoless double-? decay reaches ?50% or more in the most promising experiments.

Jun 23, 2017

Samuel Hinton – Bayesian Hierarchical Methods for Supernova Cosmology

In the era of precision cosmology, systematic uncertainty is quickly becoming the limiting factor in modern cosmological analyses. In my work, I discuss a method for performing supernova analyses by combining a hierarchical Bayesian framework with Monte-Carlo simulation realisations. This gains both the flexibility and speed of an analytic analysis along with the nuance and complexity of an algorithmic analysis, allowing for a deeper and more complex analysis.

Jun 30, 2017

Eddie Schlafly (LBNL) – Mapping the Galaxy’s Dust in 3D

The Milky Way’s dust is of basic importance in astronomy. It
is both crucial to the formation of stars and is a pervasive
observational nuisance. Despite the dust’s importance, existing dust
maps are largely limited to two dimensions, with the distance to the
dust unknown. The advent of large surveys like Pan-STARRS1 has
allowed us to map dust in three dimensions in unprecedented detail. In
this talk, I will describe how we use observations of stars in the
Milky Way to map dust, and I will discuss three major results: a
catalog of distances to major molecular clouds, the discovery of a 100
pc ring of dust in Orion, and the 3D dust map itself. Upcoming
surveys promise continued scientific returns: Gaia, DECam, and LSST
will provide more precise and deeper data than ever before, enabling
unique maps of the Galaxy’s spiral structure and the study of the
dust’s properties in 3D.

Aug 04, 2017

Yi-Kuan Chiang (Johns Hopkins) – Which Galactic dust map should I use? Insights from extragalactic tomography

Over the past few years, clustering-based redshift estimation has emerged as a new way to estimate redshifts and perform extragalactic tomography of arbitrary datasets. On a similar timescale, observations by Planck, WISE, Pan-STARRS and 21cm radio surveys have been used to create a multitude of SFD-type Galactic dust maps. I will explain how clustering-based redshift estimation can be used to test the quality of the seven different dust maps currently available and I will show that extragalactic signatures can be revealed in many of them. When such maps are used for correcting optical magnitudes, we therefore expect biases which are likely to affect the precision of cosmological experiments using supernovae, BAOs, or the growth of structures. I will present possible solutions to alleviate this issue and discuss which map should be used depending on which measurement one wishes to make.

Sep 15, 2017

Oliver Just (RIKEN)? – Modeling remnants of neutron-star mergers and core-collapse supernovae

Neutron-star mergers and core-collapse supernovae are promising events to herald a new era of multi-messenger astronomy, as they release substantial amounts of energy in gravitational waves, neutrinos, and electromagnetic emission. Moreover, these events are connected to long-standing physics questions related to, e.g., heavy-element nucleosynthesis, gamma-ray bursts, and the nuclear equation of state. However, while offering a unique laboratory to investigate matter and spacetime under extreme conditions, these events are particularly difficult to model theoretically, one of the most challenging, but equally important ingredients being the neutrino transport. The latter is not only responsible for cooling the compact remnant and heating its surroundings, but it may also have a major leverage on the nucleosynthesis conditions in the ejecta and the eventual launch of a polar jet. In this talk I will review the current state-of-the-art in modeling mergers and core-collapse supernovae and present some recent results that we obtained from numerical simulations.

Sep 22, 2017

Yury Kolomensky (LBNL) – New results from the CUORE experiment

Sep 29, 2017

Stephen Portillo (Harvard) – Improved Source Detection in Crowded Fields using Probabilistic Cataloging

Cataloging is challenging in crowded fields because sources are extremely covariant with their neighbors and blending makes even the number of sources ambiguous. We present the first optical probabilistic stellar catalog, cataloging a crowded (~0.1 sources per pixel) Sloan Digital Sky Survey r band image from M2. Probabilistic cataloging returns an ensemble of catalogs inferred from the image and thus can capture source-source covariance and deblending ambiguities. By comparing to a traditional catalog of the same image and a Hubble Space Telescope catalog of the same region, we show that our catalog ensemble better recovers sources from the image. It goes more than a magnitude deeper than the traditional catalog while having a lower false discovery rate brighter than 20th magnitude. Future telescopes will be more sensitive, and thus more of their images will be crowded. We detail our efforts to extend probabilistic cataloging to galaxies, making the method applicable to the data that will be collected in the Large Synoptic Survey Telescope era.

Oct 06, 2017

Marie Lau (UC Santa Cruz) – Quasars Probing Quasars: the Circumgalactic Medium Surrounding z ~ 2 Quasars

Understanding the circumgalactic medium–the gaseous halo surrounding a galaxy, is an integral part to understanding galaxy evolution. The z ~ 2-3 universe is interesting as this is when the star formation rate and AGN activity peak. My work concludes the decade-long Quasars Probing Quasars survey designed for studying massive galaxy formation and quasar feedback. I use background quasar sightlines that pass close to foreground quasars to study the circumgalactic medium of quasar-host galaxies in absorption. My sample of 149 quasar pairs involve spectra taken with 17 different optical and near IR instruments. I present results on the statistical and physical properties of the quasar circumgalactic medium. My results pose challenges for cosmological hydrodynamic simulations to produce a substantial cool gas reservoir surrounding quasars, that is also enriched and exhibits extreme kinematics.
I will discuss other science goals that can be facilitated using the spectral databases and absorption-line analysis tools built. If there is interest, I will show preliminary results on a peculiar tidal disruption event and evidence for deep internal mixing in red giants.

Oct 13, 2017

Michael Walther (UCSB) – New Constraints on Thermal Evolution in the IGM from the Small Scale Ly? Forest Power Spectrum

The line-of-sight power spectrum (P_F(k)) of the Ly-? forest has proven to be a valuable tool for doing cosmological observations. It also not only allows to constrain cosmological parameters, but enables us to measure the thermal state of the IGM at redshifts z>1.8. While at large scales (k<0.02 s/km) P_F(k) has been accurately measured using the large number (10^3-10^5) of quasar sightlines from SDSS and BOSS, there are much less spectra available at smaller scales (larger k). Prior power spectrum measurements from high-resolution data only used several times less (QSO) spectra in our redshift range about 15 years ago whereas a few hundred became available in the meantime. We therefore performed a new measurement using 74 quasar sightlines with 1.8<z<3.4 significantly improving the precision of the small-scale P_F(k). Using this additional precision on small scales combined with the BOSS measurements on large scales enables us to accurately constrain the thermal cutoff scale of the IGM set by a combination of temperature broadening of Ly-? forest lines, and ‘Jeans’ smoothing due to baryonic pressure support. We perform an MCMC analysis based on Gaussian process based techniques for interpolation between a grid of high-resolution hydrodynamical simulations and using our new high-resolution dataset, the BOSS data, a recent X-SHOOTER analysis, and a previous HIRES/MIKE analysis at higher redshifts. This allows us to measure thermal evolution in the IGM from z=5.4 to z=1.8 showing a suggestive peak at z~3.3 that might be attributed to He reionization. These constraints will help solving the existing discrepancies in the IGM thermal evolution between different works using different techniques as existing degeneracies between different thermal parameters in the existing measurements can be broken in our analysis.and can be used to place limits on possible exotic sources of heating. Additionally a better knowledge of thermal evolution will also lead to better constraints of e.g. the nature of dark matter or neutrino masses by breaking degeneracies in those measurements and thereby improve our knowledge of the underlying cosmology.

Oct 20, 2017

Prabhat (NERSC at LBL) – Deep Learning for Science

Deep Learning has revolutionized the fields of computer vision, speech recognition and control systems. Can Deep Learning (DL) work for scientific problems? This talk will explore a variety of DOE/LBL applications that are currently benefiting from Deep Learning. We will review classification and regression problems in astronomy, cosmology, neuroscience, genomics and high-energy physics. We will outline several short and long-term challenges at the frontier of DL research, and speculate about the future of DL for data-intensive science.

Oct 27, 2017

Xavier Prochaska (UCSD) – Deep Learning of Quasar Spectra

I will describe our development of a convolutional neural network (CNN) to learn to search for and characterize absorption lines in quasar spectra. Specifically, the algorithm discovers and measures the redshift and Hydrogen column density of damped Lya systems (DLAs). These systems dominate the neutral hydrogen gas of the universe, trace the interstellar medium of distant galaxies, and offer cosmological constraints on the build up of gas and heavy elements across cosmic time. I will discuss the lessons learned employing CNN techniques on large spectral datasets and the prospects for future analysis.

Nov 03, 2017

Noah Kurinsky (Stanford) – Pushing to Low Mass with SuperCDMS SNOLAB: New Developments in Ultra-Low Threshold Dark Matter Detectors

In the last few years, the dark matter field has bifurcated into experiments focused on wimp-scale dark matter with massive liquid noble detectors and experiments focused on so-called ‘hidden sectors’ dark matter, pushing small detectors to much lower energy resolutions. Low-mass dark matter searches, focusing on single eV-scale energy deposits, are sensitive to different backgrounds than their higher-threshold counterparts, including but not limited to infrared emissions from the experimental environment and low-rate cosmogenic contamination in the target materials. The traditional paradigm of 2-phase detectors used to discriminate between electronic and nuclear recoils is no longer effective, both because of experimental limitations and kinematic constraints. The low-mass reach of SuperCDMS SNOLAB is based on the idea of moving from a phonon+charge readout to a charge-mediated phonon readout; introducing degeneracy between our separate detection channels to achieve lower thresholds. In this talk I will discuss the theory behind the CDMS-HV detector technology and present exciting results from prototype detectors run at test facilities in the CDMS collaboration. I will then discuss the science reach given these results, and explore future directions with this technology.I will describe our development of a convolutional neural network (CNN) to learn to search for and characterize absorption lines in quasar spectra. Specifically, the algorithm discovers and measures the redshift and Hydrogen column density of damped Lya systems (DLAs). These systems dominate the neutral hydrogen gas of the universe, trace the interstellar medium of distant galaxies, and offer cosmological constraints on the build up of gas and heavy elements across cosmic time. I will discuss the lessons learned employing CNN techniques on large spectral datasets and the prospects for future analysis.

Nov 10, 2017

Katelin Schutz (UCB) – Excluding a thin dark matter disk in the Milky Way with Gaia DR1: Resurrecting the Dinosaurs

If a component of the dark matter has dissipative interactions, it could collapse to form a thin dark disk in our Galaxy coincident with the baryonic disk. It has been suggested that dark disks could explain a variety of observed phenomena, including mass extinction events due to periodic comet impacts. Using the first data release from the Gaia space observatory, I will present the results of a search for a dark disk via its effect on stellar kinematics in the Milky Way. I will discuss our strong new limits that disfavor the presence of a thin dark matter disk and present updated measurements on the total matter density in the solar neighborhood.

Nov 24, 2017


Dec 01, 2017

Yuan Mei (LBL) – TPC without charge multiplication: a CMOS direct readout towards neutrinoless double-beta decay and other applications

High-pressure gaseous TPCs provide a unique combination of excellent energy resolution, event tracking for background discrimination, and scalability, which are ideal for neutrinoless double-beta decay searches. We are developing a pixelated charge readout plane filled with an array of CMOS sensors to harness the power of such a TPC. Each CMOS sensor has an exposed metal patch for direct charge collection and integrates charge sensitive amplifiers as well as signal processing and digitization/data transmission circuitry. The electronic noise is suppressed to a level that the required signal-to-noise ratio is achieved without the need of charge multiplication. It provides competitive energy resolution while improves on tracking capability, stability, and scalability compared to alternative readout schemes. Moreover, ions drifting in the gas can be read directly since the otherwise prohibitive ion avalanche is unnecessary. It enables the use of alternative gases and double-beta decay candidate isotopes such as $^{82}$SeF$_6$ gas, in which only ion drifting is possible. With modest modifications, the readout plane could be used in liquid noble gas and organic liquid TPCs for a broad range of applications. The design and the progress of the first prototype will be presented.

Dec 08, 2017

Anna Zsigmond – GERDA neutrinoless double beta decay experiment

Dec 15, 2017

Marco Salathe (LBL) – GRETA R&D