LBNL Physics Division Research Progress Meetings

Brice Menard (JHU) and Ting-Wen Lan (IPMU) - Twenty years of SDSS spectra: lessons for DESI
2018-04-03 16:00 - 17:00 (America/Los_Angeles)
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.

Colin Hill (IAS) - "Fundamental Physics from the Foreground-Obscured Microwave Sky: Inflation, Neutrino Masses, and Beyond"
2018-04-05 16:00 - 17:00
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.

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
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.

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.

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
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.

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.

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.

Chris Fassnacht (UC Davis) "Cosmological parameters from strong gravitational lenses"
2018-05-17 16:00 - 17:00 | 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.

Nicholas Carlini (UCB) "Adversarial Machine Learning"
2018-05-29 16:00 - 17:00 | HYBRID 50A-5132 (Sessler Conference Room), https://lbnl.zoom.us/j/91782268585, 50A-5132
Abstract:
Many fundamental properties of neural networks are still not well
understood. This talk studies two of these from an adversarial perspective.
I begin with my main line of research and examine the apparently-fundamental
susceptibility of neural networks to adversarial examples. I develop effective
algorithms for generating adversarial examples and find that most most training
regimes are ineffective at increasing robustness. Then, I perform a brief
examination of neural network memorization, and demonstrate that training
data can be efficiently extracted from a trained model given only black-box
access to that model. I conclude with directions for future research.

Michael Hance (UCSC) "Searching for Compressed SUSY at the Energy Frontier"
2018-05-31 16:00 - 17:00
ABSTRACT:
Weak-scale Supersymmetry can help to resolve several puzzles presented by the Standard Model, including the nature of dark matter and the naturalness of the Higgs mass, and has motivated a robust search program at the Large Hadron Collider. Searches for direct production of Supersymmetric partners of weak bosons and leptons are particularly interesting as probes of dark matter and naturalness, but are challenged by small cross sections, low-momentum decay products, and multiple Standard Model backgrounds. I will review efforts by the ATLAS experiment to discover such new particles, with an emphasis on scenarios with “compressed” mass spectra containing nearly-mass-degenerate states. I will discuss recent LHC results, as well as prospects for discovery in Run 2 and beyond.

Masashi Hazumi (KEK) "LiteBIRD Satellite for Tests of Cosmic Inflation and Quantum Gravity"
2018-06-04 14:00 - 15:00 | HYBRID 50A-5132 (Sessler Conference Room), https://lbnl.zoom.us/j/91782268585, 50A-5132
Abstract:
Cosmological inflation is the leading hypothesis to resolve the problems in the Big Bang theory.
It predicts that primordial gravitational waves were created during the inflationary era, which
then imprinted large-scale curl patterns in the cosmic microwave background (CMB)
polarization map called the B-modes.
Measurements of the CMB B-mode signals are known as the best probe
to detect the primordial gravitational waves.
LiteBIRD is a candidate for JAXA’s strategic large mission to map the polarization of
the CMB radiation over the full sky at large angular scales with unprecedented precision,
which will offer us a crucial test of cosmic inflation. It will also serve as the first crucial test of
quantum gravity such as superstring theory. Precise polarization maps of LiteBIRD will also
provide us with valuable pieces of information on particle physics and astrophysics.
In this talk, I will give an overview of the science and design of LiteBIRD

Norbert Zacharias (USNO) "Impact of Gaia on Astrometry and Beyond"
2018-06-14 16:00 - 17:00 | INPA Common Room (50-5026), 50-5026
April 2018 marks the 2nd data release (DR2) of the ESA Gaia space mission.
A new era in astrometry begun. Accurate positions, proper motions
and parallaxes for over a billion stars are now available on the
sub-mas level. The properties of DR2 will be explained in context
to pre-Gaia data and the final Gaia results expected in a few years.
The impact of Gaia reaches far into almost all of astronomy, and a
few examples will be given.

Joshua Spitz (U. Michigan) " First Measurement of Monoenergetic Muon Neutrino Charged Current Interactions
2018-06-21 08:00 - 17:00 | HYBRID 50A-5132 (Sessler Conference Room), https://lbnl.zoom.us/j/91782268585, 50A-5132
ABSTRACT:
This talk will present the first measurement of monoenergetic muon
neutrino charged current interactions. The MiniBooNE experiment at
Fermilab has been used to isolate and study 236 MeV muon neutrino
events originating from charged kaon decay at rest. The muon
kinematics and total cross section have been extracted from this data.
Notably, this result is the first known-energy, weak-interaction-only
probe of the nucleus to yield a measurement of omega (energy
transferred to the nucleus) using neutrinos, a quantity thus far only
accessible through electron scattering. I will discuss the
significance of this measurement, and these monoenergetic neutrinos in
general, for elucidating both the neutrino-nucleus interaction and
oscillations.
Slides here

Adam Becker (UCB) "An Incomplete Survey of Proposed Solutions to the Quantum Measurement Problem"
2018-06-28 16:00 - 17:00 | HYBRID 50A-5132 (Sessler Conference Room), https://lbnl.zoom.us/j/91782268585, 50A-5132
ABSTRACT:
The central puzzle that drives the field of quantum foundations is the measurement problem: what gives rise to the appearance of wave function collapse? While there is no single answer to this question that has wide acceptance, this is not for lack of available options. A variety of solutions to the measurement problem have been proposed, in the form of various interpretations or modifications of quantum mechanics. Some solutions eliminate collapse entirely, as in the many-worlds and de Broglie-Bohm interpretations. Others propose altering the dynamics of the theory to make collapse objective, as in GRW (stochastic collapse) and gravitational collapse theories. “Psi-epistemic” interpretations attempt to dissolve the measurement problem by claiming that the wave function isn’t something real in itself, but merely a representation of our knowledge of an underlying reality. Finally, Copenhagen-style interpretations claim that that there is no “reality” to be talked about at all. Bounding this menagerie of interpretations are several important theorems that restrict the options available. Bell’s theorem is the most famous (and most misunderstood) of these, but it is not the only one. In this talk, I will briefly lay out the measurement problem and its history, go over several of the theorems that constrain the possible solutions, and discuss a few of the families of quantum interpretations and the open problems that remain for each of them.
Slides here

Yuri Gershtein (Rutgers U.) "CMS Tracker for HL-LHC: an Exciting New Tool for Discovery"
2018-07-10 16:00 - 17:00
Abstract
The radiation environment at the High Luminosity LHC requires CMS to
replace its silicon tracker with one that is more radiation hard and granular.
The new tracker is designed twenty years after the original one, and has new unique
capabilities. It spans 8 units in rapidity, is more then twice lighter, and is capable to
participate in the first level of trigger decisions. In this talk, after sketching the
HL-LHC physics case, I will describe the detector design, FPGA-based track reconstruction,
and focus on one of many possible new opportunities it provides for new physics searches.

Laura Newburgh (Yale U.) "New Probes of Old Structure: Cosmology with 21cm Intensity Mapping and the Cosmic Microwave Background"
2018-07-19 16:00 - 17:00 | HYBRID 50A-5132 (Sessler Conference Room), https://lbnl.zoom.us/j/91782268585, 50A-5132
ABSTRACT:
Current cosmological measurements have left us with deep questions about our Universe: What caused the expansion of the Universe at the earliest times? How did structure form? What is Dark Energy and does it evolve with time? New experiments like CHIME, HIRAX, and ACTPol are poised to address these questions through 3-dimensional maps of structure and measurements of the polarized Cosmic Microwave Background. In this talk, I will describe how we will use 21cm intensity measurements from CHIME and HIRAX to place sensitive constraints on Dark Energy between redshifts 0.8 — 2.5, a poorly probed era corresponding to when Dark Energy began to impact the expansion history of the Universe. I will also discuss how we will use data from new instruments on the ACT telescope to constrain cosmological parameters like the total neutrino mass and probe structure at late times.
Slides Here

Sinead Farrington (U. Warwick) "Physics with Taus"
2018-09-06 16:00 - 17:00 | HYBRID 50A-5132 (Sessler Conference Room), https://lbnl.zoom.us/j/91782268585, 50A-5132
Abstract:
The identification of hadronically decaying tau leptons at the LHC is challenging. I will review the methods for tau reconstruction at ATLAS and how the identification of tau leptons has enabled several interesting and novel measurements in exotics and Higgs physics at the LHC. I will also look to the future and give some thoughts on next implementations for tau leptons at the LHC.

Martin White (UCB) "The cosmological legacy of Planck "
2018-09-20 16:00 - 17:00 | HYBRID 50A-5132 (Sessler Conference Room), https://lbnl.zoom.us/j/91782268585, 50A-5132
ABSTRACT:
The anisotropies in the cosmic microwave background radiation have become our most important cosmological fossil. The study of these “echoes of gravity” has revolutionized cosmology, stringently tested our models and allowed precise measurement of a host of important cosmological parameters. I will discuss how far we’ve come since the early detections of CMB anisotropies and in particular the cosmological legacy of the Planck mission.

Matt Pyle (UCB) "Athermal Phonon Detectors: World Leading Light Mass Dark Matter Sensitivity From Athermal Phonon Detectors + Preliminary Performance from Large Area Photon Detector for Next Generation Neutrinoless Double Beta Decay Experiments"
2018-09-27 16:00 - 17:00 | HYBRID 50A-5132 (Sessler Conference Room), https://lbnl.zoom.us/j/91782268585, 50A-5132
Abstract:

In this talk, we present the new world leading results from the first search of the SuperCDMS collaboration for inelastic electronic recoils from low mass dark matter dark matter (500keV – 100MeV) using our new single ionization sensitive cryogenic calorimeters.

We’ll also present preliminary performance of a large area cryogenic photon detector with applications in light mass dark matter and neutrinoless double beta decay. With 3eV sensitivity and 20us pulse rise time, it well surpasses all technical requirements for next generation cryogenic neutrinoless double beta decay experiments.

Kyle Helson (NASA Goddard) "The Status and Outlook of Cosmic Microwave Background Polarization Measurements"
2018-10-04 16:00 - 17:00 | HYBRID 50A-5132 (Sessler Conference Room), https://lbnl.zoom.us/j/91782268585, 50A-5132
Abstract:
The detailed characterization of the intensity and polarization Cosmic Microwave Background (CMB) radiation provides a powerful tool to constrain the properties of early Universe. The polarization induced by a stochastic gravitational wave background in this epoch induces a distinctive and measurable signature of primordial inflationary processes. Presently the field has a healthy contingent of ground, balloon, and space based missions. In this talk I will discuss a brief history of CMB measurements, the current status of the field and outlook for the future. I will also discuss on-going work at NASA Goddard Space Flight Center on the development of polarization-sensitive detectors for a future satellite CMB polarization mission and their application in ground based instruments.

Qian Xin (BNL) "Development of LArTPC for Neutrino Physics"
2018-10-11 16:00 - 17:00 | HYBRID 50A-5132 (Sessler Conference Room), https://lbnl.zoom.us/j/91782268585, 50A-5132
Abstract:
Liquid Argon Time Projection Chamber (LArTPC), with its mm-scale position resolution and the full-active-volume imaging-aided calorimetry, is an excellent device to detect accelerator neutrinos at GeV energy range. This technology may hold the key to search for new CP violation in the lepton sector, to determine the neutrino mass hierarchy, to precisely measure neutrino mixing parameters, to search for baryon number violation, and to search for sterile neutrino(s). In this talk, I will review the current status of the detector development. In particular, the challenges in TPC signal processing and event reconstruction will be discussed among other subjects.

Ning Bao (UCB/LBNL) "Quantum Information and Quantum Gravity"
2018-10-18 16:00 - 17:00 | HYBRID 50A-5132 (Sessler Conference Room), https://lbnl.zoom.us/j/91782268585, 50A-5132
ABSTRACT:
There has been much recent interest at the intersection of the fields of Quantum Information and Quantum Gravity. In this talk, I will go over some of the motivating principles/important work that has been done in this area, and explain some current research promising research trends.

Matthias Neubert (U. Mainz) "Effective Field Theory after a New-Physics Discovery"
2018-10-23 16:00 - 17:00 | HYBRID 50A-5132 (Sessler Conference Room), https://lbnl.zoom.us/j/91782268585, 50A-5132
ABSTRACT:

When a new heavy particle is discovered at the LHC, it will be interesting to study its decays into Standard Model particles using an effective field-theory framework. We point out that the proper effective theory must be based on non-local operators defined in soft-collinear effective theory (SCET). For the interesting case where the new resonance is a gauge-singlet spin-0 boson, which is the first member of a new sector governed by a mass scale M, we show how a consistent scale separation between M and the electroweak scale v is achieved up to next-to-next-to-leading order in lambda~v/M. The Wilson coefficients in the effective Lagrangian depend in a non-trivial way on the mass of the new resonance and the masses of yet undiscovered heavy particles. Large logarithms of the ratio M/v can be systematically resummed using the renormalization group. We develop a SCET toolbox, with which it is straightforward to construct the relevant effective Lagrangians for new heavy particles with other charges and spin.

Laura Newburgh (Yale U.) " Forefronts of Cosmology: Beyond Standard Model Physics with Upcoming CMB Instruments"
2018-10-25 16:00 - 17:00 | HYBRID 50A-5132 (Sessler Conference Room), https://lbnl.zoom.us/j/91782268585, 50A-5132
Abstracts
Upcoming new instruments to measure the polarized CMB promise to provide discriminatory limits on inflation, the number of light relic particles, and the sum of the neutrino masses, ushering in a new era of using the CMB as a probe of particle physics. Achieving these science goals requires highly sensitive instruments that are composed of enormous arrays of low noise detectors. In addition, systematic errors and foreground removal must be improved to lower the systematics floor below the statistical errors, necessitating dramatic improvements in calibration precision. In this talk, I will describe Simons Observatory (coming online in ~2021) and CMB-S4 (coming online in ~2027), their science goals, and how the twin requirements for sensitivity and systematics require a new approach to software for readout, data acquisition, and control systems. I will also discuss future directions for cosmology, including work in 21cm instruments to improve our understanding of the nature of Dark Energy.

Caterina Vernieri (Stanford) "Higgs to Beauty Quarks: First Observation of the Big Missing Piece"
2018-10-30 16:00 - 17:00 | HYBRID 50A-5132 (Sessler Conference Room), https://lbnl.zoom.us/j/91782268585, 50A-5132
ABSTRACT:
The Higgs boson discovery at the LHC marked a historic milestone in the study of fundamental particles and their interactions. Over the last six years, we have begun measuring its properties, which are essential to build a deep understanding of the Higgs sector of the Standard Model and to potentially uncover new phenomena. The Higgs’ favored decay mode to beauty (b) quarks (~60%) had so far remained elusive because of the overwhelming background of b-quark production due to strong interactions. Observing the Higgs decay to b-quarks was one of the critical missing pieces of our knowledge of the Higgs sector. Measuring this decay is a fundamental step to confirm the mass generation for fermions and may also provide hints of physics beyond the Standard Model. The CMS observation of the decay of the SM Higgs boson into a pair of b-quarks exploiting an exclusive production mode (VH) is yet another major milestone. This experimental achievement at the LHC, considered nearly impossible in the past, makes use of several advanced machine learning techniques to identify the b-quark distinctive signature, improve the Higgs boson mass resolution, and discriminate the Higgs boson signal from background processes.

Vivian Poulin (JHU) "Shedding Light on Dark Matter with the CMB: Implications for EDGES 21cm Signal"
2018-11-01 16:00 - 17:00 | HYBRID 50A-5132 (Sessler Conference Room), https://lbnl.zoom.us/j/91782268585, 50A-5132
ABSTRACT:
In this talk, I would like to review how the Cosmic Microwave Background (in particular its temperature and polarization anisotropies) can be used to perform both direct and indirect detection of Dark Matter. In a first part, I will show how the CMB can be used to put stringent constraints on DM models leading to energy injection, such as DM annihilations and decay or Primordial Black Holes matter accretion. I will compare CMB bounds to those coming from galactic cosmic and gamma ray searches and illustrate how the 21cm signal, a major target of next generation surveys, can be used to significantly improve over current limits. In a second part, I will discuss a recent puzzling absorption feature in the global 21cm signal observed by the EDGES experiment. Such feature could be explained by efficient scattering between DM and baryons in the late universe. I will show how the CMB strongly challenges such explanation of that signal.

Guy Ron (Jerusalem) "The Proton Radius - Old Measurements and New Ideas"
2018-11-06 16:00 - 17:00 | HYBRID 50A-5132 (Sessler Conference Room), https://lbnl.zoom.us/j/91782268585, 50A-5132
ABSTRACT:
The radius of the proton, generally assumed to be a well measured and understood quantity has recently come under scrutiny due to highly precise, yet conﬂicting, experimental results. These new results have generated a host of interpretations, none of which are completely satisfactory.
I will discuss the existing results, focusing on the discrepancy between the various extractions. I will brieﬂy discuss some theoretical attempts at reso-lution and focus on new scattering measurements, both planned and already underway, that are attempting to resolve the puzzle

Lucie Tvrznikova (Yale) "Sub-GeV dark matter searches and electric field studies for the LUX and LZ experiments "
2018-11-08 16:00 - 17:00 | HYBRID 50A-5132 (Sessler Conference Room), https://lbnl.zoom.us/j/91782268585, 50A-5132
ABSTRACT:
The Large Underground Xenon (LUX) and the LUX-ZEPLIN (LZ) detectors were designed to directly observe the interaction of dark matter (DM) with xenon target nuclei and thus probe much of the unexplored DM parameter space. I will discuss two novel direct detection methods, Bremsstrahlung and the Migdal effect, that were used by LUX to place limits on DM with masses of 0.4-5 GeV. I will also describe the development of a fully 3D model of electric fields that varied during the detector’s final 332 live-days of data acquisition. Since direct measurement of electric fields was not possible, this work enabled a thorough understanding of the detector throughout its operation. Lastly, I will present new results from the Xenon Breakdown Apparatus (XeBrA) built at LBNL to characterize the dielectric breakdown under high voltage in liquid xenon and liquid argon. Results from XeBrA will inform LZ and the future of noble liquid detector engineering.

Christian Herwig (U. Pennsylvania) " Targeting natural supersymmetry with top quarks"
2018-11-13 16:00 - 17:00 | HYBRID 50A-5132 (Sessler Conference Room), https://lbnl.zoom.us/j/91782268585, 50A-5132
Abstract:
What is the roadmap for the discovery of new physics in the
post-Higgs-observation era? The concept of naturalness can provide a
useful guiding principle, considering the interplay between new, heavy
physics and the electroweak scale. I will describe a new search for
natural models of supersymmetry from the ATLAS experiment via the
production of light top squarks. I will also discuss the impact of
precision top-quark measurements on future searches, highlighting a
recent measurement of quantum interference in top-quark production.

Stephane Brunet Cooperstein (Princeton) "Observation of Higgs Boson Decay to Bottom Quarks by the CMS Experiment"
2018-11-15 16:00 - 17:00 | HYBRID 50A-5132 (Sessler Conference Room), https://lbnl.zoom.us/j/91782268585, 50A-5132
ABSTRACT:
Since the discovery of the Higgs boson six years ago, great progress has been made in measuring precisely its properties. These measurements have primarily been made via rare Higgs boson decays to two photons or two Z bosons due to their distinct experimental signatures. Although 60% of the Higgs bosons are predicted to decay to bottom quarks, it was not originally expected to observe this Higgs boson dominant decay mode until much later in the LHC program due to an overwhelming background of bottom quarks produced via strong interactions. This milestone observation was achieved this summer by both the ATLAS and CMS experiments at the LHC. This seminar presents the observation of the Higgs boson decay to bottom quarks by the CMS experiment, with an emphasis on the latest results using data collected in 2017. The observation was made possible by incorporating deep learning techniques and novel analysis methods. This constitutes the first observation of a Yukawa coupling to down-type quarks. Moreover, it demonstrates the feasibility of the first precision measurements of Higgs bosons in the VH production mode in the near future.
