LBNL Physics Division Research Progress Meetings

Ulascan Sarica (John Hopkins U.) "Measurements of Mass, Width, Lifetime, and Anomalous Couplings of the H(125) Boson"
2017-11-16 16:00 - 17:00 (America/Los_Angeles) | HYBRID 50A-5132 (Sessler Conference Room), https://lbnl.zoom.us/j/91782268585, 50A-5132
Abstract:
The discovery of the Higgs boson has completed the set of particles predicted by the Standard Model (SM). It has been established by the CMS and ATLAS Collaborations at the Large Hadron Collider that the discovered boson is consistent with J^PC=0^++. The width of this boson is also consistent with the predicted value from the SM, but the constraints using events at the resonance peak are orders of magnitude looser than the prediction. In this talk, we will be exploring techniques developed to probe small anomalous couplings of the Higgs boson. Emphasis will be given to the recent studies of Higgs-diboson (HVV) couplings from the CMS Collaboration, where information from associated production becomes even more important than the kinematics of Higgs decay products. We will also look at joint mass-width measurements using either events at the resonance peak or at the offshell tail of Higgs boson production. We will see that even small anomalous couplings show enhancement at the offshell tail and discuss briefly how joint constraints can be studied.

Bin Yu (University of California, Berkeley) "Three Principles of Data Science: Predictability, Stability, and Computability"
2017-11-09 16:00 - 17:00
ABSTRACT:
In this talk, I’d like to discuss the intertwining importance and connections of three principles of data science in the title in data-driven decisions.
Making prediction as its central task and embracing computation as its core, machine learning has enabled wide-ranging data-driven successes. Prediction is a useful way to check with reality. Good prediction implicitly assumes stability between past and future. Stability (relative to data and model perturbations) is also a minimum requirement for interpretability and reproducibility of data driven results (cf. Yu, 2013). It is closely related to uncertainty assessment. Obviously, both prediction and stability principles can not be employed without feasible computational algorithms, hence the importance of computability.
The three principles will be demonstrated in the context of two neuroscience projects and through analytical connections. In particular, the first project adds stability to predictive modeling used for reconstruction of movies from fMRI brain signlas to gain interpretability of the predictive model. The second project uses predictive transfer learning that combines
AlexNet, GoogleNet and VGG with single V4 neuron data for state-of-the-art prediction performance. It provides stable function characterization of neurons via (manifold) deep dream images from the predictive models in the difficult primate visual cortex V4. Our V4 results lend support, to a certain extent, to the resemblance of these CNNs to a primate brain.

Reserved
2017-11-07 16:00 - 17:00, 2017-11-02 16:00 - 17:00, 2017-10-31 08:00 - 17:00, 2017-10-26 08:00 - 17:00, 2017-10-24 08:00 - 17:00, 2017-10-17 08:00 - 17:00 | HYBRID 50A-5132 (Sessler Conference Room), https://lbnl.zoom.us/j/91782268585, 50A-5132

Anthony Pullen (NYU) Title: Revealing CII Emission with LSS Cross-correlations
2017-10-19 16:00 - 17:00 | HYBRID 50A-5132 (Sessler Conference Room), https://lbnl.zoom.us/j/91782268585, 50A-5132
Abstract:

In this talk, I will present our joint measurement of cosmic infrared background (CIB) and CII line emission from large scales at redshift z=2.5 using an MCMC analysis of cross-correlations of the 3 high-frequency Planck bands with both SDSS-III quasars at z=2-3.2 and SDSS-III CMASS galaxies at z=0.43-0.7. The CII emission is expected to correlate with the quasars and appear in the Planck 545 GHz band, while the other cross-correlations are assumed to mostly be attributable to CIB-LSS correlations. We report an excess emission inconsistent with the null result at 95% confidence, with an intensity value favoring the higher range of CII models. I will also forecast potential CII intensity constraints from Planck cross-correlated with DESI quasars.

Barnabas Poczos (CMU) Title: Distribution Regression and its Applications
2017-10-12 16:00 - 17:00 | HYBRID 50A-5132 (Sessler Conference Room), https://lbnl.zoom.us/j/91782268585, 50A-5132
Abstract:
The most common machine learning algorithms operate on
finite-dimensional vectorial feature representations. In
many applications, however, the natural representation of the data
consists of more complex objects,
for example functions, distributions, and sets, rather than
ﬁnite-dimensional vectors. In this talk
we will discuss machine learning algorithms that can operate directly
on these complex
objects. For this purpose, we use nonparametric statistical methods
that can consistently estimate the inner product, distance, and
certain kernel functions between distributions, sets, and other
objects. We will discuss applications in various scientific areas
including cosmology (e.g. estimating the mass of galaxy clusters,
finding anomalous galaxy clusters, estimating the cosmological
parameters of our Universe, accelerating cosmological simulations),
fluid dynamics (finding anomalous events in turbulence data),
neuroimaging, and agriculture

Simeon Bird (JHU) "Strong Absorbers in the Lyman-alpha Forest and Primordial Black Holes"
2017-10-05 16:00 - 17:00 | HYBRID 50A-5132 (Sessler Conference Room), https://lbnl.zoom.us/j/91782268585, 50A-5132
Abstract:
Strong HI absorbers are essentially the largest foreground contamination for Lyman alpha forest surveys, and so a better understanding of them is necessary for achieving the goals of future Lyman alpha cosmology surveys. I will talk about a new automated technique for generating a probabilistic catalogue of strong absorbers for the entire survey, allowing more robust cleaning of the foreground. Since no technique can entirely remove strong absorbers, I will discuss new templates for characterising their effect on the flux power spectrum. A secondary systematic is induced by interpolation error between theoretical models, and I will discuss techniques to mitigate this error with refining Gaussian Process emulators. Lastly I will discuss the interesting possibility that the surprisingly common mergers of ~30 solar mass black holes observed by LIGO could be primordial black hole dark matter, which is intriguingly (still) not convincingly ruled out.

Bertrand Echenard (Caltech) "Probing light dark matter with the LDMX experiment"
2017-09-28 16:00 - 17:00 | HYBRID 50A-5132 (Sessler Conference Room), https://lbnl.zoom.us/j/91782268585, 50A-5132
ABSTRACT:
Elucidating the nature of dark matter is one of the central challenges
in fundamental physics. Dark matter originating as a thermal relic
from the early Universe is arguably one of the most compelling
paradigm, and WIMP searches have been the main focus of past
experimental efforts. Not as extensively explored, the possibility of
light (sub-GeV) thermal dark matter could arise naturally if it is
part of a dark sector neutral under all Standard Model forces. The
“Light Dark Matter eXperiment” (LDMX) proposes to explore light
thermal dark matter using an electron fixed-target missing momentum
approach with a low current, high-repetition beam. The expected
sensitivity would surpassing by orders of magnitude the reach of any
previous or currently envisioned experiment, and decisively test many
sub-GeV thermal dark matter scenarios.

Kev Abazajian (UC, Irvine) "Candidate Signals and Stringent Constraints from Dark Matter in the Sky"
2017-09-21 16:00 - 17:00 | HYBRID 50A-5132 (Sessler Conference Room), https://lbnl.zoom.us/j/91782268585, 50A-5132
Abstract:
I will discuss analyses leading to two recent candidate detections of photons from dark matter. Specifically, these are: first, gamma rays in a continuum “bump” at a few GeV which can be due to WIMP-like dark matter annihilation in the Galactic Center; and, second, X-rays from clusters of galaxies and Andromeda consistent with monoenergetic 3.55 keV photons from dark matter decay such as that predicted from sterile neutrino dark matter. Commensurately, there are also stringent constraints on these signals. I will discuss the particle and cosmological model implications of both.

Cora Dvorkin (Harvard) "Discovering New Physics Beyond the Standard Model with Cosmological Data Sets"
2017-09-14 16:00 - 17:00 | 70A-3377, 70A-3377
Abstract:
Cosmological observations have provided us with answers to age-old questions, involving the age, geometry, and composition of the universe. However, there are profound questions that still remain unanswered. I will describe ongoing efforts to shed light on some of these questions.
In the first part of this talk, I will explain how we can use measurements of the CMB and the large-scale structure of the universe to reconstruct the detailed physics of much earlier epochs, when the universe was only a tiny fraction of a second old. In particular, I will show how we can probe the shape of the inflationary potential, extra degrees of freedom during inflation, and the signature of possible particles with mass and spin during this period.
In the last part of the talk, I will discuss how we can use observations at large scales and sub-galactic scales (through strong gravitational lensing) to improve our understanding of another open question in fundamental physics: the particle nature of dark matter.

Ben Nachman (LBNL) and Mateus Ploskon (LBNL) "Jet Substructure"
2017-08-31 16:00 - 17:00 | HYBRID 50A-5132 (Sessler Conference Room), https://lbnl.zoom.us/j/91782268585, 50A-5132
ABSTRACT:
The LBNL xTalk (“cross-talk”) series provides a forum for the exchange of ideas between groups and across lab divisions. Each seminar is focused on a theme which is confronted from two perspectives. In particular, the talks are given by two presenters from different domains. The format is informal (chalk talk!) and is designed to be entertaining and engaging. Come prepared to learn and ask about details with the experts in order to stimulate collaborations between groups. We hope that this will strengthen the program at the lab and spread new ideas.
For the first xTalk, we will have Mateusz Ploskon from Nuclear Science and Benjamin Nachman from the Physics Division to discuss how jet substructure is used in ALICE/STAR and in ATLAS. Jets are collimated sprays of particles resulting from quarks and gluons produced at high energy. The radiation pattern within jets encodes a wealth of information about the parton that initiated it. Jet substructure is a hot topic in pp for tagging boosted W/Z/H bosons and also recently for precision probes of Quantum Chromodynamics (QCD); in heavy ion collisions, jet substructure is an exciting new probe of medium modifications. Please join us for this comparative discussion of how jet substructure is used in two very different environments!

Larry Lee (Harvard) "Searches for Sneaky SUSY at the ATLAS Experiment"
2017-08-17 16:00 - 17:00 | HYBRID 50A-5132 (Sessler Conference Room), https://lbnl.zoom.us/j/91782268585, 50A-5132
ABSTRACT:
Despite the lack of a sparticle discovery at the Large Hadron Collider, and despite the fact that most of the discovery potential has shriveled to an upsetting size, supersymmetry (SUSY) remains the most motivated solution to the Standard Model’s inadequacies. Because of this (and a large dose of stubbornness), we are forced to consider ways the nominal search strategy may have missed a discovery. Must SUSY present itself with lots of high-momentum objects and large missing transverse energy just because it’d be easy to find? This talk will discuss recent SUSY searches at ATLAS targeting signatures without large missing transverse energy as well as those sensitive to long-lived sparticles.

Tova Holmes (ATLAS) "The FTK: Global Tracking for the ATLAS Trigger"
2017-08-15 16:00 - 17:00 | HYBRID 50A-5132 (Sessler Conference Room), https://lbnl.zoom.us/j/91782268585, 50A-5132
Abstract:
The ATLAS Detector is in the process of upgrading its Trigger and Data Acquisition system to include global processing of tracks using the FastTracKer (FTK). The FTK uses a parallelized structure to identify and reconstruct the properties of tracks from the 98 million channels of the the ATLAS silicon detectors. With the use of hardware-level pattern matching and a two-tiered track-fitting system, this reconstruction can be performed on all events passing the first-stage ATLAS trigger, with a rate up to 100 kHz and requiring less than 100 µs per event. These capability opens new doors for b-jet and tau triggering, allows for the suppression of pile-up effects on missing energy triggers, and can even be used to isolate BSM signatures involving long-lived particles. This talk will discuss the physics case for the FTK, an overview of its design, and its integration status.

Zachary Marshall (LBNL) "Title: Searching for SUSY in Big Data at the LHC"
2017-07-13 08:00 - 16:00 | HYBRID 50A-5132 (Sessler Conference Room), https://lbnl.zoom.us/j/91782268585, 50A-5132
ABSTRACT:
One of the most enticing and popular additions to the Standard Model of particle physics, Supersymmetry, is the target of a wide range of searches at the Large Hadron Collider at CERN. The ATLAS and CMS experiments have produced an incredible variety of searches, but Supersymmetry remains elusive. We will discuss the results of some of the recent searches that demonstrate the dexterity of both experiments, and point out which assumptions might be playing an important role in the interpretation of those results. There are still many ways Supersymmetry could have escaped detection up to now, and we will also point towards some of the next directions for searches for Supersymmetry at the LHC. Along the way, we will discuss some of the software and computing challenges that come with world-wide analysis of tens of billions of events, and how the

Marcel Vos (CERN) "Prospects for Top Physics at the LHC and Beyond"
2017-06-22 16:00 - 17:00 | HYBRID 50A-5132 (Sessler Conference Room), https://lbnl.zoom.us/j/91782268585, 50A-5132
ABSTRACT:
Experiments at the Large Hadron Collider are characterizing the top quark and its interactions to unexpected precision. The combination of direct searches for new particles and indirect constraints from precision measurements provides powerful limits on extensions of the Standard Model. I start the seminar with a brief overview of top physics today and of the prospects for precision top physics of future LHC runs. This sets a high bar for future colliders that are to continue the programme initiated by Tevatron and LHC. In the second half of the seminar I discuss the potential of the future facilities envisaged in Asia and Europe. Powerful electron-positron machines have exquisite potential for key measurements such as the top quark mass and electro-weak couplings. Hadron colliders with a center-of-mass energy that significantly exceeds that of the LHC can probe the QCD interactions of the top quark an order of magnitude deeper and can provide a precise measurement of the top Yukawa coupling.

Florian Beutler (Portsmouth) "On the reliability of Baryon Acoustic Oscillation (BAO) measurements"
2017-06-01 08:00 - 17:00 | HYBRID 50A-5132 (Sessler Conference Room), https://lbnl.zoom.us/j/91782268585, 50A-5132
Abstract:

In this talk I will discuss the reliability of the Baryon Acoustic Oscillation (BAO) signal in the distribution of galaxies. The solid theoretical understanding of this observable means that it represents one of only a few cosmological observables that are not yet dominated by systematic errors. This is one reason why BAO are one of the main science drivers for future galaxy surveys like DESI and Euclid.

I will discuss my recent work on the relative velocity effect as one potential systematic for BAO. The relative velocity effect originates from the same physical effects which imprinted the BAO signal and therefore acts on the same scale. I will introduce this effect in detail, discuss how we can include it in our modeling and present current constraints from the Baryon Oscillation Spectroscopic Survey (BOSS).

Physical Sciences Institution Review
2017-05-23 08:00 - 2017-05-25 17:00

Prof. Rouven Essig (TBA) " Direct Detection of sub-GeV Dark Matter"
2017-05-11 16:00 - 17:00 | Zoom Talk, 50A-5132, Berkeley, ca, 94720
Abstract:
Dark matter makes up 85% of the matter in our Universe, but we have yet to learn its identity. A broad array of search strategies are needed to probe for non-gravitational interactions between dark matter and ordinary matter. While most searches focus on Weakly Interacting Massive Particles (WIMPs) with masses between 1 GeV and 1 TeV, it is imperative to also consider other motivated dark matter candidates. In this talk, I will discuss dark matter with MeV-to-GeV masses, which is a theoretically and phenomenologically appealing possibility and presents a new frontier in the search for dark matter. I will highlight novel dark matter direct-detection strategies that can probe this under-explored mass range. I will review how XENON10 data already probes dark matter with masses as low as a few MeV, and present recent constraints using XENON100 data. I will then discuss improvements expected from near-future experiments, focusing on xenon, semiconductor, and scintillator targets. This includes, for example, SENSEI, which is a new ultra-low-threshold silicon CCD detector that is poised to probe vast new regions of parameter space in the next few years. I will also present a few simple benchmark models of MeV-to-GeV dark matter, and contrast direct-detection probes with searches at colliders and fixed-target experiments.

Manoj Kaplighat (UC, Irvine) "The self-interacting dark matter paradigm: motivations and tests"
2017-05-04 16:00 - 17:00 | HYBRID 50A-5132 (Sessler Conference Room), https://lbnl.zoom.us/j/91782268585, 50A-5132
Abstract:

I will describe how a simple model where dark matter has large elastic self-interactions (cross section over mass of order barns per GeV) can fully explain the observed diversity of all galactic rotation curves. I will summarize the constraints imposed on model building by observations of clusters of galaxies and end with an outline of tests of this paradigm.

Heather Gray (LBNL) Title: The Art of the Impossible: Probing challenging Higgs channels at the LHC
2017-04-27 16:00 - 17:00
Abstract:

In the technical design report of the LHC experiments, measurements of the Higgs coupling to top and bottom quarks and the width of the Higgs were either predicted to be extremely challenging, if not impossible at the LHC. Yet, ATLAS and CMS have both produced interesting results for all these channels. I will highlight selected aspects of these measurements to discuss what allowed ATLAS and CMS to probe the “impossible“.

Director's Physics Division Review
2017-04-12 08:00 - 2017-04-13 17:00

Professor Sunil Golwala (Caltech) "The SuperCDMS SNOLAB Search for Low-Mass Dark Matter"
2017-03-30 16:00 - 17:00 | Zoom Talk, 50A-5132, Berkeley, ca, 94720
Abstract
The dark matter problem, known since the 1930s, has only grown in importance during the current era of precision cosmology. We remain unable to answer the question: what is the matter that makes of 5/6 of the universe’s matter density? Yet we are also in an era of unparalleled theoretical creativity and experimental opportunity. Theorists have vastly expanded the parameter space for weakly interacting massive particle dark matter in the last decade. New experimental constraints and candidates have emerged from the LHC, other accelerator experiments, and direct and indirect detection dark matter searches. I will summarize the current state of experimental searches for particle dark matter and focus on the upcoming search at low mass with the SuperCDMS SNOLAB experiment.

Haichen Wang (LBNL) Title: Search for physics beyond the Standard Model using multijet events with the ATLAS detector at the LHC
2017-03-28 16:00 - 17:00 | HYBRID 50A-5132 (Sessler Conference Room), https://lbnl.zoom.us/j/91782268585, 50A-5132
Abstract:
Search for physics beyond the Standard Model (SM) has been one of the most important goals of the physics program at CERN’s Large Hadron Collider (LHC). Among all the final states, the multijet final state has long been considered as a challenging one for the search of physics beyond the SM due to its large background. Though, exciting new physics phenomena, such as the production of black hole as well as massive supersymmetric (SUSY) particles, may well result in signals in the multijet final state. I present searches for physics beyond the SM using multijet events from 13 TeV collision data taken in 2015 and the first half of 2016 by the ATLAS experiment at the LHC. I focus on a search for the production of black hole and a search for massive supersymmetric particles decaying to many jets via R-Parity Violating (RPV) couplings. The two examples represent searches targeting physics beyond the SM at different mass scales, and therefore different analysis strategies are employed. These searches have greatly improved the sensitivity of the LHC to the black hole production and RPV SUSY scenarios, and they are complementary to searches using events of leptons, photons and missing transverse energy.

Megan Eckart (NASA) "X-ray Astrophysics Enabled by Microcalorimeters: from Recent Observations to Next-Generation Technologies"
2017-03-23 16:00 - 17:00 | Zoom Talk, 50A-5132, Berkeley, ca, 94720
Abstract:
High-resolution imaging spectroscopy in the soft x-ray waveband (0.1-10 keV) is an essential tool for probing the physics of the x-ray universe. Unique line diagnostics available in this waveband allow transformative scientific observations of a wide array of sources. For example, measurements of turbulence in the intra-cluster medium of galaxy clusters can be used to calibrate hydrodynamic simulations used in cosmology; and measurements of outflow processes from supermassive black holes may identify the key mechanism that regulates the co-evolution of host galaxies and their central black holes. I will introduce the microcalorimeter, a low-temperature detector capable of x-ray photon counting with high spectral resolution, and discuss observations of the Perseus Cluster made using our microcalorimeter instrument that launched aboard the Japanese-led Hitomi (Astro-H) mission in 2016. I will discuss our recent advances using transition-edge-sensor (TES) microcalorimeters and identify areas in detector, readout, and instrument development that are needed for next-generation instrumentation for space- and laboratory-based experiments. Techniques and challenges will be compared to those of envisaged cryogenic CMB and direct dark matter detection experiments.

Roger O’Brient (JPL) “The Search for Inflationary Gravitational Waves: Current Status of the BICEP Program and Next Generation Instrumentation.”
2017-03-21 16:00 - 17:00 | Zoom Talk, 50A-5132, Berkeley, ca, 94720
Abstract:
For over a decade, the BICEP collaboration has been deploying small aperture telescopes to the South Pole Station to map B-mode polarization in the Cosmic Microwave Background and
search for evidence of primordial gravitational waves. If detected, they would allow physicists
to constrain physics at energy scales of ~10 16 GeV levels. To date, this program places the
tightest constrains on the tensor-scalar ratio of r<0.07 (95% confidence). We are at an
important point in our program as we transition into “Stage-3” instruments with the BICEP-
array, which will search to a level of r>0.01. This rapid progress is fueled by the antenna-
coupled superconducting bolometers that we have developed at NASA’s Jet Propulsion
Laboratory. In my talk, I’ll summarize the science case for these experiments, describe the
instruments themselves with a focus on the detectors, discuss the recently collected data, and
comment on the future of our program. In particular, Thermal KIDs, an emerging bolometer
technology, will be critical for this next phase. Finally, I’ll comment on how LBL and DOE can
and will play a future role in this exciting frontier of fundamental physics.

Prof. Stacy McGaugh (Case Western) "The Radial Acceleration Relation in Rotationally Supported Galaxies"
2017-03-16 16:00 - 17:00 | Zoom Talk, 50A-5132, Berkeley, ca, 94720
ABSTRACT:
We report a correlation between the radial acceleration traced by rotation curves and that predicted by the observed distribution of baryons. The same relation is followed by 2693 points in 153 galaxies with very different morphologies, masses, sizes, and gas fractions. The correlation persists even when dark matter dominates. Consequently, the dark matter contribution is fully specified by that of the baryons. The observed scatter is small and largely dominated by observational uncertainties. This radial acceleration relation is tantamount to a natural law for rotating galaxies.
