LBNL Physics Division Research Progress Meetings

Chris Fassnacht (UC Davis) "Cosmological parameters from strong gravitational lenses"
2018-05-17 16:00 - 17:00 (America/Los_Angeles) | HYBRID 50A-5132 (Sessler Conference Room), https://lbnl.zoom.us/j/91782268585, 50A-5132
Abstract:
Recent measurements of the Hubble Constant (H_0) through distance
ladder techniques have revealed a noticeable tension with the
Planck H_0 value that was obtained under the assumption of the cosmological
“standard model”, i.e., a flat Lambda cold dark matter cosmology. Is this
tension an indication that modifications to the standard model are
necessary, or is it the sign of unknown systematic effects in one or
both of the techniques? To address this question requires additional
high-precision measurements with techniques that are independent of
the distance ladder. The time delay strong lensing technique, in
which gravitational lensing by a massive galaxy produces multiple
images of a time-variable quasar, fulfills these requirements. I will
present recent results from the H0licow program, in which the analysis
of just three time-delay strong lenses has produced a 3.8% measurement
of H_0, and discuss the implications for other cosmological parameters,
including those describing dark energy. I will also discuss the
future prospects of this technique in the era of large sky surveys and
extremely large telescopes.

Christian Bauer (LBNL) "GENEVA: Combining perturbative calculations with parton showers"
2018-05-10 16:00 - 17:00 | HYBRID 50A-5132 (Sessler Conference Room), https://lbnl.zoom.us/j/91782268585, 50A-5132
ABSTRACT:
I will discuss the event generator GENEVA, which for the first time combines fixed order and resummed perturbative calculations with parton showering and hadronization. I will explain the basic physics concepts underlying GENEVA, and show how they can be used to achieve in principle any accuracy desired. After presenting physics results on the production of vector boson + jets at the LHC, I will finish by giving an overview of how to use GENEVA.

Alan Schwartz (University of Cincinnati) "Challenging the Standard Model with the Belle(II) Experiment"
2018-05-03 16:00 - 17:00 | HYBRID 50A-5132 (Sessler Conference Room), https://lbnl.zoom.us/j/91782268585, 50A-5132
Abstract:
The Belle experiment in Japan began taking data in the late 1990’s and went on to record the world’s largest sample of B-anti-B meson pairs produced in a quantum correlated state. This initial state allowed Belle, and the BaBar experiment at SLAC, to measure CP violation in B decays with high accuracy. These measurements contributed to the awarding of the 2008 Nobel Prize in Physics to Kobayashi and Maskawa for their theory of CP violation. However, other measurements have exhibited discrepancies with the Standard Model, e.g., measurements of |Vub| and |Vcb| , R(D) and R(D*), etc. Over the past several years, the Belle detector and accelerator complex have been rebuilt and significantly upgraded to become the Belle II experiment. Belle II is designed to record 50 times the data set that Belle recorded, and with much improved detector performance. This forthcoming data should resolve several discrepancies observed by Belle and BaBar. Here we review some recent results from Belle and discuss the physics program and current status of Belle II.

Gustavo Branco (CFTP-IST, Univ. de Lisboa, Portugal) - "Multi-Higgs Models, The Flavor Problem and the Origin of CP Violation"
2018-04-26 16:00 - 17:00 | ca
We analyse two-Higgs-Doublet extensions of the Standard Model, paying special attention
to novel mechanisms for natural suppression of scalar Flavor-Changing-Neutral-Currents
and their imllementation in specific models. Some of the most salient implications of these models will be presented. The possibility of having realistic models of spontaneous CP violation will be studied.

Paolo Calafiura (LBNL) HL-LHC Computing Challenges
2018-04-19 16:00 - 17:00 | HYBRID 50A-5132 (Sessler Conference Room), https://lbnl.zoom.us/j/91782268585, 50A-5132
The current models for HL-LHC computing show order-of-magnitude resource shortages with large uncertainties. Business-as-usual is not an option unless we accept limiting HL-LHC physics reach, particularly for precision studies.
A grassroots initiative called the HEP Software Foundation has been collecting ideas and pooling efforts to perform the necessary R&D to meet these O($100M) resource shortages. HSF produced a Community White Paper that has been endorsed by the LHC experiments, the Worldwide LHC Computing Grid, and some funding agencies.
I will briefly review some of the technical and organizational challenges ahead of us as we turn the Community White Paper into a research program, and try to present some of the exciting new R&D ideas we are prototyping at Berkeley Lab and elsewhere.

George Smoot (UCB/LBNL) "Reinterpreting Low Frequency LIGO/Virgo Events as Gravitationally-Lensed Magnified Stellar-Mass Black Hole Mergers at Cosmological Distances"
2018-04-12 16:00 - 17:00 | ca
Abstract:
Though dismissed by most, we claim that strong gravitational lensing of the gravitational waves for merging black holes explains the high mass binary black hole mergers observed by LIGO/Virgo explains the apparent 30 M_Sun events better than any alternative models.
It turns out to be difficult to make large mass black hole binaries in sufficient number to explain LIGO’s results. However, strong gravitational lensing of cosmological distant mergers can naturally explain them while the redshift of the orbital frequencies amplifies the observed apparent masses.

Colin Hill (IAS) - "Fundamental Physics from the Foreground-Obscured Microwave Sky: Inflation, Neutrino Masses, and Beyond"
2018-04-05 16:00 - 17:00 | ca
The cosmic microwave background (CMB) remains a key source from which to extract information about fundamental physics, due to its clean, well-understood origin and immense constraining power on many types of new physics. The next decade of CMB observations will yield answers to at least two fundamental questions: (1) did large-field inflation source the initial density perturbations in our universe? (2) what is the absolute mass scale of the neutrinos? In this talk, I will explain the routes by which these answers will be obtained. Both rely on highly precise measurements of the polarization of the CMB, which can be used to search for the signature of primordial gravitational waves (answering the first question) and to measure the growth of cosmic structure via gravitational lensing (answering the second question). Moreover, I will describe new methods with which to overcome the most significant challenge to this program: emission from non-primordial foreground sources. I will highlight the major role that the Simons Observatory and CMB-Stage IV experiments will play in these exciting developments. Finally, I will describe additional unique information about the distribution and properties of baryons and dark matter that these measurements will yield, providing crucial feedback for cosmological analyses with DESI and other large-scale structure surveys.

Brice Menard (JHU) and Ting-Wen Lan (IPMU) - Twenty years of SDSS spectra: lessons for DESI
2018-04-03 16:00 - 17:00 | ca
We have played with SDSS spectra for almost two decades and enjoyed performing all sorts of statistical analyses with them. In this talk we will take a critical look at these explorations and discuss what has worked well and what has not, what mistakes were made and some of the fundamental limits arising from the calibration of the data — all of which are informative to prepare ourselves for the DESI era. Finally we will also discuss new data analysis ideas and emerging techniques that are likely to impact the way we think and manipulate spectra in the near future.

Sven Vahsen (University of Hawaii) - Directional Dark Matter Searches via Charge Cloud Tomography
2018-03-29 16:00 - 17:00 | ca
With WIMP-nucleon scattering limits approaching the neutrino floor, and coherent neutrino-nucleon scattering experimentally established, there is renewed interest in directional detectors as a means to penetrate the neutrino floor. The CYGNUS collaboration aims to deploy multiple gas Time Projection Chambers (TPCs) to accomplish this. I will review recent R&D work carried out within CYGNUS, with a focus on efforts at the University of Hawaii. I will discuss recently deployed directional neutron detectors capable of imaging the 3D surface shape of nuclear recoils with high resolution. These existing detectors represent a stepping stone towards larger detectors capable of providing fully tomographic 3D images of nuclear recoils. I will discuss how 3D recoil imaging is relevant to dark matter detection by enabling several new measurement techniques. Time permitting, I will also discuss a conceptual design study that compares the suitability of different technological approaches to a large-scale nuclear recoil observatory with sensitivity to both WIMP dark matter and neutrinos.

Lisa Barsotti (MIT) "Squeezing the most out of gravitational wave detectors"
2018-03-27 16:00 - 17:00 | HYBRID 50A-5132 (Sessler Conference Room), https://lbnl.zoom.us/j/91782268585, 50A-5132
ABSTRACT:
The recent observations of gravitational waves have been enabled by a new generation of LIGO detectors, Advanced LIGO, the most sensitive laser interferometers ever built. In my talk I will review the main scienctific results from the first two Observing Runs, O1 and O2, and discuss the status of the Advanced LIGO detectors and plans for O3. I will also describe prospects for further extending the astrophysical reach of ground-based observations with future generations of detectors.

Andreu Font (U. College London) - "Cosmology with the Lyman alpha forest: challenges and opportunities”"
2018-03-22 16:00 - 17:00 | HYBRID 50A-5132 (Sessler Conference Room), https://lbnl.zoom.us/j/91782268585, 50A-5132
From 2009 to 2014, the Baryon Oscillation Spectroscopic Survey (BOSS) used the SDSS telescope to obtain spectra of 1.5 million galaxies to get very accurate measurements of the Baryon Acoustic Oscillations (BAO) scale at redshift z ~0.5. At the same time, BOSS observed over 184 000 high redshift quasars (z>2.15) with the goal of detecting the BAO feature in the clustering of the intergalactic medium, using a technique known as the Lyman alpha forest (LyaF). In this talk I will overview the final results from the LyaF working group in BOSS, including the measurement of BAO at z=2.4 both from the auto-correlation of the LyaF (Bautista et al. 2017), and from its cross-correlation with quasars (du-Mas-des-Bourboux et al. 2017). From the combination of these studies we are able to measure the expansion rate of the Universe 11 billion years ago with a 2% uncertainty.
Starting in 2019, the Dark Energy Spectroscopic Instrument (DESI) will increase this dataset by an order of magnitude. In this talk I will review the challenges that we will face in order to provide an exquisite measurement of the expansion over cosmic history, and the opportunities that we will have to study other fundamental questions: the sum of the mass of the neutrino species, properties of dark matter particles, and the shape of the primordial power spectrum of density fluctuations.

Simone Ferraro (LBNL) "Lighting up the Dark Universe"
2018-03-20 16:00 - 17:00 | HYBRID 50A-5132 (Sessler Conference Room), https://lbnl.zoom.us/j/91782268585, 50A-5132
Recent progress in cosmological observations reveal a simple yet strange universe. Our preferred cosmological model relies on mysterious components such as Dark Matter, Dark Energy and an early period of accelerated expansion. The challenge in the next decade will be to understand the nature of these components and reveal new aspects of fundamental physics.
I will discuss the synergies between upcoming redshift and CMB experiments and show that thanks to sample variance cancellation techniques, a large improvement on constraining power is possible even at fixed volume. I will highlight the role of cross-correlations and velocity fields in increasing the statistical power of future surveys, while at the same time allowing for greater control of systematics. I will show how the combination of large-scale structure and CMB experiments hold great promise to reveal the secrets of our mysterious Universe.

Peter Mohr (NIST) "The New SI and Fundamental Constants"
2018-03-15 16:00 - 17:00 | 50-Auditorium
The International System of Units (SI) is expected to undergo a revolutionary change on
May 20, 2019. In October 2017, the International Committee on Weights and Measures met
at the International Bureau of Weights and Measures near Paris and recommended a new
definition of the SI such that a particular set of constants would have certain values when
expressed in the new SI units. In particular, the new SI would be defined by the statement:
The International System of Units, the SI, is the system of units in which

the unperturbed ground state hyperfine splitting frequency of the
caesium 133 atom Cs is 9 192 631 770 Hz,
the speed of light in vacuum c is 299 792 458 m/s,
the Planck constant h is 6.626 070 15× 10−34 J/Hz,
the elementary charge e is 1.602 176 634×10−19 C,
the Boltzmann constant k is 1.380 649×10−23 J/K,
the Avogadro constant NA is 6.022 140 76×1023 mol−1,
the luminous efficacy Kcd of monochromatic radiation of frequency 540×1012 hertz is 683 lm/W

The numerical values of the constants were determined by a special CODATA adjustment of
the values of the constants using data in papers that were accepted for publication by July
1, 2017.
The Convention of the Meter (Convention du M`etre), a treaty that specifies international
agreement on how units are defined, was established in 1875 with 17 nations initially signing
on, including the U.S. The SI, established within the treaty in 1960, is more recent and
continues to evolve. Currently, the treaty is agreed to by fifty-eight Member States, including
all the major industrialized countries. Even though a majority of people in the U.S. still
use units such as inches and pounds, the official standards for these units are based on the
SI units, so the U.S. national measurement standards will also be redefined, although the
change will be imperceptible in every-day use.
The redefinition will have a significant impact on the fundamental constants when ex-
pressed in SI units. Not only will the defining constants be exact, but many others will also
be exact, and still others will have considerably reduced uncertainties. This reflects a shift
from macroscopic measurement standards to quantum based standards.
This talk will describe the new SI, review reasons for the change, and show how units
can be based on assigned values of certain physical constants.

Julien Guy (LBNL) "The DESI Project, Construction Status and Prospects for Precise Cosmological Distance Measurements with Lyman-Alpha Forests"
2018-02-27 16:00 - 17:00 | HYBRID 50A-5132 (Sessler Conference Room), https://lbnl.zoom.us/j/91782268585, 50A-5132
Abstract:
The Dark Energy Spectroscopic Instrument is a multi-object spectrograph composed of a wide field corrector, a 5000 robotically positioned fiber system, and 10 3-arms spectrographs. The instrument is installed this year on the Mayall 4-m diameter telescope at Kitt Peak, Arizona. Operations will start next year. In 5 years, DESI will measure spectra and redshifts of more than 30 million galaxies and quasars. This catalog will be used to measure the expansion history of the Universe and the growth rate of structure in the past 10 billion years with sub-percent precision. I will present the construction status and give some insight on the Lyman-alpha BAO analysis.

Lauren Tompkins (Stanford U.) "The World’s most complicated game of Bingo: Pattern Recognition at the Energy-Intensity Frontier"
2018-02-20 16:00 - 17:00 | HYBRID 50A-5132 (Sessler Conference Room), https://lbnl.zoom.us/j/91782268585, 50A-5132
Abstract:
In 2012 the ATLAS and CMS experiments discovered the Higgs Boson, firmly establishing the Standard Model as the dominant paradigm for subatomic particle interactions. Many expected the Higgs discovery to be one of several discoveries at the energy frontier, yet five years later it remains the single addition to the subatomic particle pantheon. Meanwhile, the LHC has begun to push the boundaries of the hadron collision intensity frontier, yielding large datasets for further understanding the Standard Model as well as continuing the increasingly difficult search for new physics. I will discuss a path through the intensity frontier, focusing on a hardware based, real-time pattern recognition engine which will enable the ATLAS experiment to fully exploit the delivered data by playing the world’s most complicated game of bingo.

Haichen Wang (LBNL) Title: The Higgs boson and the top quark share the stage
2018-02-15 16:00 - 17:00 | HYBRID 50A-5132 (Sessler Conference Room), https://lbnl.zoom.us/j/91782268585, 50A-5132
Abstract:
The top quark plays an important role in the collider phenomenology of the Higgs boson, and the study of the interplay between the top quark and the Higgs boson may provide key insights to some critical questions in particle physics. A milestone in the experimental study of the top-Higgs sector of the Standard Model will be the observation of the Higgs boson production in association with top quarks (ttH), a direct evidence for the top-Higgs Yukawa coupling. With 36.1 fb-1 pp collisions at 13 TeV, the ATLAS experiment performed searches for the ttH production in several channels and found the evidence for this production. In this talk, I start with a brief overview on the experimental understanding of the Higgs boson properties and motivate the study of the top-Higgs Yukawa coupling. I then present the ATLAS ttH searches with a focus on the diphoton channel. In the end, I discuss the prospect of the ttH study and its impact on other aspects of the LHC physics program.

Zeynep Demiragli (CMS / MIT) "Search for Dark Matter: CMS Strikes Back!"
2018-02-13 16:00 - 17:00 | HYBRID 50A-5132 (Sessler Conference Room), https://lbnl.zoom.us/j/91782268585, 50A-5132
Abstract:
The experiments at the Large Hadron Collider (LHC) at CERN are at the energy frontier of particle physics, searching for answers to fundamental questions of nature. In particular, dark matter (DM) presents strong evidence for physics beyond the standard model (SM). However, there is no experimental evidence of its non-gravitational interaction with SM particles. If DM has non-gravitational interactions with the SM particles, we could be producing the DM particles in the proton-proton collisions at the LHC. While the DM particles would not produce an observable signal in the detector, they may recoil with large transverse momentum against visible particles resulting in an overall transverse momentum imbalance in the collision event. In this talk, I will review the searches for DM particles in these missing momentum final states at the Compact Muon Solenoid (CMS) experiment. I will also discuss the prospects for discovering dark matter at the High Luminosity-LHC and other future experiments.

Daniel Scolnic (U. Chicago) "Measuring Dark Energy with Supernovae and Kilonovae"
2018-02-08 16:00 - 17:00 | HYBRID 50A-5132 (Sessler Conference Room), https://lbnl.zoom.us/j/91782268585, 50A-5132
ABSTRACT:
The next decade will be the golden age of cosmology with transients. In this talk, I will present new analyses of Type Ia Supernovae that mark the most precise measurement of dark energy to date. I will go over how this analysis ties together with the analysis of the local value of the Hubble constant, for which tension persists with the inferred value from the CMB – an exciting hint at possible departures from the standard cosmological model. I will then discuss the first measurements of the Hubble constant with kilonovae and gravitational waves. I will review the large amount of overlap between the issues that must be tackled for future progress using supernovae and kilonovae to measure cosmological parameters. Finally, I will discuss the roles that surveys like LSST and WFIRST will play and how we can harness the millions of transients discovered to make generation-defining cosmological measurements.

Heather Gray (LBNL) Title: The Higgs and the Quarks; Probing the Yukawa couplings of the Higgs boson
2018-02-06 16:00 - 17:00 | HYBRID 50A-5132 (Sessler Conference Room), https://lbnl.zoom.us/j/91782268585, 50A-5132
Abstract:
The discovery of the Higgs boson at the LHC in 2012 relied predominantly on studies of the bosonic decay modes. However, there is a rich structure in the Yukawa sector of the Higgs boson. Studies of the direct coupling of the Higgs boson to fermions can be used to probe the proportionality of this coupling to the fermion mass and hence the test the fermionic mass generation mechanism. I will introduce current experimental studies in the quark sector and, in particular, the recent evidence obtained at the LHC for the coupling of the Higgs to heavy quarks. I will discuss some of the important experimental challenges and highlight new ideas for the future.

Jason Bono (FNAL) Physics and Mathematics in Music
2018-02-01 16:00 - 17:00 | HYBRID 50A-5132 (Sessler Conference Room), https://lbnl.zoom.us/j/91782268585, 50A-5132
ABSTRACT:
Music is nearly universal in human culture and yet it remains
mysterious. In order to help answer some of music’s fundamental
questions, we will briefly turn to archeology and early history before
examining some of music’s salient features from a physical and
mathematical perspective. Principles rooted in physics and pure
mathematics will provide a link to intercultural qualities of musical
tone and melody to the deep role that symmetry plays in human
perception, thus shedding light on the questions that we set out to
answer. To enhance clarity and familiarity, various concepts will be
illustrated with animations and sound bites.

Alex Drlica-Wagner (FNAL) "Using Cosmic Surveys to Understand the Fundamental Nature of Dark Matter"
2018-01-30 16:00 - 17:00 | HYBRID 50A-5132 (Sessler Conference Room), https://lbnl.zoom.us/j/91782268585, 50A-5132
ABSTRACT:
The existence of dark matter is strong evidence for new physics beyond the Standard Model. While laboratory and collider searches for dark matter have advanced rapidly over the past several decades, astrophysical observations currently provide the only robust, positive, empirical measurement of dark matter. Astrophysical observables can be directly linked to the fundamental properties of dark matter, such as particle mass, self-interaction cross section, and self-annihilation rate. In this talk, I will discuss how the Fermi Large Area Telescope (LAT) and the Dark Energy Survey (DES) have advanced our understanding of dark matter from observations of the smallest and most dark-matter-dominated galaxies. In addition, I will discuss opportunities to build a cohesive dark matter program with the Large Synoptic Survey Telescope (LSST).

John Alison (U. Chicago) "Di-Higgs Production at the LHC: Current Status and Future Prospects"
2018-01-25 16:00 - 17:00 | HYBRID 50A-5132 (Sessler Conference Room), https://lbnl.zoom.us/j/91782268585, 50A-5132
ABSTRACT:
I will discuss motivations for searching for di-Higgs production at the LHC. Recent results and projected sensitivities will be presented with emphasis on the dominant hh->4b channel.

Chihway Chang (KICP/U. Chicago) "Cosmic Surveys in the Next Decade: Mapping the Landscape of the Universe"
2018-01-23 16:00 - 17:00 | HYBRID 50A-5132 (Sessler Conference Room), https://lbnl.zoom.us/j/91782268585, 50A-5132
ABSTRACT:
Cosmology in the next decade will be driven by data. Exploiting the information one can extract from the ongoing and upcoming large surveys will give us the power to stress-test the LCDM model with unprecedented precision and open up windows for new physics. In this talk I will present some of our work in the Dark Energy Survey Collaboration and the Large Synoptics Survey Telescope Dark Energy Science Collaboration, to analyse state-of-the-art galaxy survey data as well as getting ready for the next generation of data. I will focus on topics surrounding weak lensing analyses, including cosmology from 2-point functions, generating weak lensing mass maps, and measuring the mass profiles at the outskirts of galaxy clusters.

Mengjiao Xiao (University of Maryland) "Probing the Nature of the Universe from the Chinese Underground Experiments"
2018-01-11 16:00 - 17:00 | HYBRID 50A-5132 (Sessler Conference Room), https://lbnl.zoom.us/j/91782268585, 50A-5132
Abstract:
Despite the tremendous success of the Standard Model (SM) of particle physics, it becomes more and more clear that the SM is far from complete. For example, the non-zero neutrino mass was the first solid evidence beyond the SM, but we still do not understand why neutrinos are so light, and if they are their own anti-particles. We know that the mass of the universe is dominated by dark matter, but we do not understand the nature of the dark matter. Exploring these unknowns may lead to fundamental science discoveries and deepen our understanding of the universe.
Due to their feeble interactions with normal matter, both neutrinos and dark matter are studied under low background environment in underground laboratories. This area of research is booming in China with a few underground facilities in operation or under construction. The first half of my talk will introduce the Jiangmen Underground Neutrino Observatory (JUNO), an experiment aiming to determine the neutrino mass ordering and to precisely measure oscillation parameters using a large liquid scintillator detector. I will then discuss the PandaX project, a series of experiments using dual-phase xenon for dark matter direct detection in the China Jin-Ping underground Laboratory.
Bio:
Mengjiao Xiao, Ph.D. of Shanghai Jiao Tong University in 2016, now is postdoc at University of Maryland, College Park. Working on PandaX and JUNO experiment.

Oindree Banerjee (Ohio State University) "Searching for ultra-high-energy neutrinos with the Antarctic Impulsive Transient Antenna "
2018-01-09 16:00 - 17:00 | HYBRID 50A-5132 (Sessler Conference Room), https://lbnl.zoom.us/j/91782268585, 50A-5132
Abstract:

Ultra-high-energy (> 10^18 eV) neutrinos remain undiscovered in this era of rapid growth in multi-messenger astronomy. These neutral and weakly-interacting particles can travel cosmic distances without attenuation and point straight back to their source, rendering them promising messengers. Detection of these elusive particles requires an enormous instrumented volume of a dielectric material such as water, ice, salt, etc. Use of radio Cherenkov method enables this at a relatively low cost. The Antarctic Impulsive Transient Antenna (ANITA) is a NASA-funded long-duration balloon experiment that is launched from near McMurdo Station, Antarctica, to fly over the continent in roughly circular orbits in the stratosphere for a month. ANITA looks for the radio signature from ultra-high-energy neutrino interaction in the ice below. There have been four flights of ANITA so far. I will review the principles underlying radio detection of neutrinos by ANITA, the ANITA instrument and recent developments in the hardware and electronics of ANITA. I will show results from the currently ongoing search for a diffuse flux of neutrinos in the data from the third flight of ANITA.

Bio:

I received my Bachelor’s degree in Physics from North Carolina State University. Currently, I am a 5th year graduate student in Physics at Ohio State University. For the ANITA-IV mission, I built, tested and deployed electronics which, for the first time, were able to dynamically filter anthropogenic noise at tunable frequencies. These filters helped to triple the “effective livetime” of ANITA-IV compared to ANITA-III. In analysis, I am working on new techniques for background rejection using data from the ANITA-II and ANITA-III flights.

Luise Poley (Humboldt U.) "Testbeam studies for the ATLAS ITk strip tracker"
2017-12-19 11:00 - 12:00 | HYBRID 50A-5132 (Sessler Conference Room), https://lbnl.zoom.us/j/91782268585, 50A-5132
Abstract
During Long Shutdown 3 (2024/2025) of the Large Hadron Collider, the ATLAS Inner Detector will be replaced with a new all-silicon tracker, composed of a pixel and a strip tracker. The strip tracker will consist of 18,000 detector modules, each comprised of a silicon strip sensor with readout electronics glued on to its surface.
Extensive quality assurance and quality control programmes have been established for module components as well as combined structures in order to ensure high reliability and efficiency. Among different methods to test components and modules, measurements in particle beams (testbeams) provide operating conditions similar to the LHC and thus are critical for understanding the detector performance.
This talk presents measurements performed using an electron beam at the DESY-II testbeam facility and X-ray photons at the Diamond Light Source. The results show the influence of different sensor architectures on the module performance, how testbeams can improve the understanding of material distribution in the detector and how these measurements can benefit the future ATLAS detector.
BIO:
I have studied at the Humboldt-Universität zu Berlin, where I worked on ATLAS analysis (b-tagging efficiencies) for my bachelor thesis. I joined the ITk strip tracker project in 2012, when I started to work at DESY for my master thesis and later for my PhD. Since 2015, I have participated in all ITk testbeam activities at DESY and organised nine testbeams myself.

Michaela Queitsch-Maitland (DESY) Title: "Precision measurements of Higgs boson production and the search for dark matter in ttbar events at the LHC"
2017-12-12 16:00 - 17:00 | HYBRID 50A-5132 (Sessler Conference Room), https://lbnl.zoom.us/j/91782268585, 50A-5132
Abstract:
“Despite the huge success of the Standard Model (SM), there is overwhelming evidence for physics beyond the SM and many remaining questions, such as the nature of dark matter (DM). The current leading candidate for DM are Weakly Interacting Massive Particles (WIMPs), which could be produced directly at colliders.
In this talk I will discuss complimentary methods for exploring new phenomena at the LHC with the ATLAS experiment. Firstly, through precision measurements of the Higgs boson properties, and secondly though the production of missing transverse energy in association with pairs of top quarks.
Finally, I will discuss the High Luminosity LHC (HL-LHC) project and the ATLAS inner tracker (ITk) upgrade, focusing on characterising the end-of-lifetime performance and validations of material budget estimates.”

Daniel Baxter (Northwestern University) Probing the Dark Sector: The Quest for a Background-Free Detector
2017-12-07 16:00 - 17:00 | HYBRID 50A-5132 (Sessler Conference Room), https://lbnl.zoom.us/j/91782268585, 50A-5132
Abstract:
Dark matter represents one of the most sought after discoveries in physics. Leading theories predict that extremely sensitive detectors could probe nuclear recoils from dark matter interactions. The PICO collaboration uses bubble chambers to look for the energy deposition from such an interaction. The biggest challenge in searching for dark matter is the mitigation and understanding of the numerous other sources of events that could look like dark matter, namely radioactive backgrounds. I will discuss how a long effort to understand backgrounds in the PICO bubble chambers led to the recent background-free result of PICO-60 and how discoveries made along the way might affect other rare event searches.
Bio:
Daniel Baxter is a graduating 5th year PhD student at Northwestern University and active member of the international PICO collaboration searching for dark matter using bubble chamber detectors. His research has largely focused on dark matter detector calibration, specifically understanding differences in detector response between nuclear and electron recoils. He has applied this expertise to the PICO-60 detector as run coordinator of its first physics run, which became the first background-free run of a bubble chamber at the 40L scale.

Syed haider Abidi (University of Toronto) "Measurement of Higgs Boson Properties & ITk Detector Development"
2017-11-30 16:00 - 17:00 | HYBRID 50A-5132 (Sessler Conference Room), https://lbnl.zoom.us/j/91782268585, 50A-5132
Abstract:
During Run 1 of LHC, the ATLAS and CMS collaboration firmly established the existence of a Higgs boson but detailed measurements were limited by statistical precision. With the larger Run 2 dataset, we have measured the couplings and production cross-section of the Higgs boson using the H->ZZ->4l decay channel. The results improve upon the previous ones by more than a factor of 2. For the first time, we also measure the differential cross-section within production modes and use it to place constraints on Beyond Standard Model scenarios.
ATLAS has an extensive detector upgrade plan to allow itself to collect and exploit the data delivered during HL-LHC. The upgrade of the current inner track with the all- silicon ITk is the largest project. At University of Toronto, we have lead the Canadian effort to establish ITk strip module assembly. Collaborating with Celestica, we have also established ASIC gluing and wire-bonding processes in industry. Additionally, we are probing the impact of radiation damage to estimate the end-of-life performance of the ITk.
Bio:
As I have done my undergraduate training in Engineering Science, I have been interested in bringing this prospective to physics research. As such I have been involved in many research projects, ranging from condensed matter to accelerator development.
Since 2013, I have focused on measurements of Higgs boson properties using the ATLAS detector and ITk detector development. I have lead and been involved in numerous analyses using the H->ZZ->4l channel and analyses combining results from various other decay channels. Additionally I have led the development and investigation of ITk modules at University of Toronto. In the future, I intend to continue pursuing both physics analyses and detector hardware.

Patrick Bryant (U. Chicago) "Measuring Higgs Pair Production at the LHC - Why and How?
2017-11-21 16:00 - 17:00 | HYBRID 50A-5132 (Sessler Conference Room), https://lbnl.zoom.us/j/91782268585, 50A-5132
Abstract:
As the universe cooled immediately following the Big Bang, the laws of physics underwent a dramatic phase transition. Underlying symmetries were broken and particles acquired mass as the Higgs field moved to a new ground state.
In this talk I will discuss why we should care about the precise nature of the electroweak phase transition (EWPT) and how the potential which generated the EWPT may be measured at the LHC.
Bio: Patrick received his B.S. in physics and mathematics at the University of Oregon in 2013 and has since been working towards his Ph.D. in experimental particle physics at the University of Chicago as a member of the ATLAS collaboration. He recently returned to Chicago after a year and a half at CERN in Geneva, Switzerland to write his thesis on hardware based track reconstruction and the search for Higgs pair production in the four b-jet final state.
