LBNL Physics Division Research Progress Meetings

David Shih (Rutgers/LBNL) "Searching for the Unexpected at the LHC with Unsupervised Machine Learning"
2019-10-22 16:00 - 17:00 UTC | HYBRID 50A-5132 (Sessler Conference Room), https://lbnl.zoom.us/j/91782268585, 50A-5132
ABSTRACT:
Conventional methods for searching for new physics at the LHC have mostly been “top-down”: starting from a specific model, searches are designed and optimized to have the best sensitivity to that model. Despite hundreds of conventional new physics searches at the LHC, none have turned up any hint of new physics. Maybe it’s time to admit that we don’t know what we’re looking for.
Breakthroughs in modern deep learning have the potential to revolutionize how we search for new physics at the LHC. In particular, techniques borrowed from unsupervised machine learning could enable us to search for new physics in a largely model-agnostic way. In this talk I will review some promising recent proposals in this direction. These proposed search strategies could complement more conventional methods by finding surprising signals that were not anticipated by any model, ensuring that we leave no stone unturned in the hunt for new physics at the LHC.

Koji Terashi (CERN) " Quantum Computing and Possible Application to High-Energy Physics"
2019-10-31 16:00 - 17:00 | HYBRID 50A-5132 (Sessler Conference Room), https://lbnl.zoom.us/j/91782268585, 50A-5132
Abstract:
High-energy frontier in particle physics is going to enter into an era of precision studies after Run 3 at the LHC, with the increase of proton luminosity and upgraded detectors. This will pose a significant challenge to the event reconstruction and data analysis, where one has to look for (tiny) hints of new physics in a huge amount of collected data. Over the last few years quantum computing, in particular the hardware systems with superconducting qubits, has grown significantly, making a quantum computer with order of 50-100 qubits, called NISQ device, nearly in hand. This motivates an exploration of this new technology in high energy physics (HEP) experiments, aiming to identify interesting application of quantum algorithms to data analysis. In this talk, I will discuss about possible HEP applications of quantum computing and current status of those studies.

Reserved
2019-11-05 16:00 - 17:00, 2019-11-07 16:00 - 17:00, 2019-11-12 16:00 - 17:00, 2019-11-14 16:00 - 17:00, 2019-11-19 16:00 - 17:00, 2019-11-26 16:00 - 17:00, 2019-11-28 16:00 - 17:00, 2019-12-19 16:00 - 17:00 and 4 more dates | HYBRID 50A-5132 (Sessler Conference Room), https://lbnl.zoom.us/j/91782268585, 50A-5132

Zhaodi Pan (U. Chicago) "Instrument and science for the SPT-3G cosmic microwave background receiver"
2019-11-21 16:00 - 17:00 | HYBRID 50A-5132 (Sessler Conference Room), https://lbnl.zoom.us/j/91782268585, 50A-5132
Abstract:

SPT-3G is a third-generation camera for the 10-meter diameter South Pole Telescope (SPT), which is designed to measure the cosmic microwave background (CMB). To achieve a high mapping speed, we have developed a new multichroic receiver with a total of 16,000 polarization-sensitive detectors. SPT-3G began a 6-year 1500 square degree survey in February 2018, which will produce measurements of CMB temperature and polarization anisotropies with an unprecedented combination of angular resolution and sensitivity. In this talk, I will summarize the instrument status and highlight the development of the most compact millimeter-wavelength Fourier transform spectrometer, which was used for SPT-3G and is also a prototype for the proposed PIXIE satellite. I will also discuss the science goals and current data analyses, with a focus on the gravitational lensing analysis using SPT-3G’s first-year data.

Tommaso Ghigna (Oxford U.) "The quest for CMB B-modes and the challenge of controlling systematic effects"
2019-12-03 16:00 - 17:00 | HYBRID 50A-5132 (Sessler Conference Room), https://lbnl.zoom.us/j/91782268585, 50A-5132
Abstract:
The Cosmic Microwave Background has played a central role for cosmology in the past few decades. From the very first detection of its temperature more than 50 years ago to the measurement of the temperature anisotropy, every step contributed to advancing our understanding of the fundamental laws that govern our Universe. One of the most ambitious targets of current and future experiments is the detection of the primordial polarized B-mode signal. This signal is a tracer of inflation and it is expected to be most visible at large angular scales.
I will review the current status of the search for B-modes focusing on one of the main challenges: instrumental systematic effects and strategies to keep them under control. In particular I will discuss the impact of band-pass uncertainty in the presence of Galactic foregrounds. I will describe a simulation procedure developed to study the induced bias into CMB polarization maps, and the recovered tensor-to-scalar ratio parameter. I will describe the connection between the simulation results and the instrumental parameters for a representative space mission, and define requirements to minimize the effect. Furthermore, I will introduce our current plan to develop a testbed, which we can use to address multiple systematic effects without waiting for the fully assembled instrument.
The required sensitivity for a definitive measurement of the B-mode signal is extremely challenging, and focal planes of experiments are growing in size to increase the optical throughput in order to meet the requirements. This will require extra efforts in designing, fabricating, and testing all telescope components; only through meticulous knowledge of the instrument and all its sub-systems, as well as a careful calibration, we will be able to reach this ambitious goal.

Peter Timbie (UW-Madison) "21cm Intensity Mapping: A New Cosmological Tool?"
2019-12-05 16:00 - 17:00 | HYBRID 50A-5132 (Sessler Conference Room), https://lbnl.zoom.us/j/91782268585, 50A-5132
ABSTRACT:
The 21 cm line from neutral hydrogen gas has many useful properties for mapping large volumes of the cosmos. These maps will give us a view of the Universe when the first luminous objects formed through gravity – the Cosmic Dawn and the Epoch of Reionization, and later, the post-Reionization Universe. They may even allow us to map the epoch before these luminous objects, the cosmic dark ages. The large volumes of these maps promise dramatic improvements in estimation of cosmological parameters. Data is flowing now from a new generation of radio telescopes optimized for this task. Unfortunately, the main challenge for all of them is that the astrophysical radio foregrounds are ~10,000 times brighter than the expected hydrogen signal. In this talk I will focus on current and planned efforts to use the new technique of` ‘hydrogen intensity mapping’ to make tomographic maps of the post-Reionization universe. In particular, I will describe the first measurements from an instrument in China, called the Tianlai (‘Cosmic Sound’) Pathfinder.

Jelle Aalbers (Stockholm U) "XENON1T: When All Other Lights Go Out"
2019-12-10 16:00 - 17:00 | 50B-4205
Abstract:
Direct detection experiments create the most radioactively quiet spots on earth, to reveal collisions between dark and ordinary matter. XENON1T, the most sensitive such experiment currently, will soon be succeeded by LZ and XENONnT. This talk highlights XENON1T’s recent light dark matter search results, and modern analysis techniques — full online processing, and tensorflow-based profile likelihoods — to boost the physics reach of future direct detection experiments and other rare-event searches.

Qing Shilo Xia (Yale) "Hunting for neutrinoless double beta decay with liquid xenon detectors"
2019-12-12 16:00 - 17:00 | HYBRID 50A-5132 (Sessler Conference Room), https://lbnl.zoom.us/j/91782268585, 50A-5132
Abstract:

Liquid xenon (LXe) is employed in a number of current and future detectors for rare event searches. In this talk, I will present the latest results from EXO-200, which searched for neutrinoless double beta decay (0υββ) in Xe-136 between 2011 and 2018. I will also present a measurement of the absolute scintillation and ionization response generated by MeV energy gamma sources over a range of electric fields in EXO-200. These measurements are useful for simulating the performance of future 0υββ detectors employing LXe, such as nEXO, which is a next generation 0υββ experiment using Xe-136 aiming to reach a half-life sensitivity ~10^28 years. nEXO will require ultra-low radioactivity, high-speed cabling to carry digital signals from in-LXe electronics. I will describe the development of high-bandwidth digital cable prototypes with sufficiently low radioactivity for use in the experiment. While designed specifically for nEXO, the demonstration of radiopure high-bandwidth cabling and interconnection techniques is relevant for many next-generation rare-event searches with large channel counts and high-speed digital electronics.

Sumit Dahal (Johns Hopkins U) "The Cosmology Large Angular Scale Surveyor: Detector Design and Performance"
2019-12-17 16:00 - 17:00 | HYBRID 50A-5132 (Sessler Conference Room), https://lbnl.zoom.us/j/91782268585, 50A-5132
Abstract:
The Cosmology Large Angular Scale Surveyor (CLASS) aims to characterize the primordial gravitational waves at the level of tensor-to-scalar ratio of 0.01, and make a cosmic-variance-limited measurement of the optical depth to reionization. CLASS is an array of four telescopes that surveys 70% of the microwave sky from the Atacama Desert at 40, 90, 150, and 220 GHz frequency bands. A unique combination of large sky coverage, rapid front-end polarization modulator, broad frequency coverage, and background-limited detectors enables CLASS to characterize the B-mode and E-mode power spectra on both the reionization and recombination scales. The detector arrays for all four CLASS telescopes contain smooth-walled feedhorns that couple to transition-edge sensor bolometers through planar orthomode transducers fabricated on mono-crystalline silicon. In this talk, I will give an overview of the design and performance of the CLASS detectors and provide an update on the current status of CLASS telescopes.

Hanna Herde (Brandeis U.) "Measuring the Mass of the Higgs Boson in the Four-Lepton Final State with the ATLAS Detector"
2020-01-07 16:00 - 17:00 | 50B-4205
Abstract:
The Higgs boson mass determines its couplings to every other known particle – and it is a free parameter of the Standard Model of Particle Physics. Understanding the Higgs’ connections with the rest of the universe requires measuring its mass experimentally. This talk presents the mass measurement in the four-lepton final state with the ATLAS detector using the full LHC Run 2 proton-proton dataset of 139 fb at sqrt{s}=13 TeV. It will particularly emphasize the role of the detector and include a look at ATLAS’ future in the High Luminosity era – the Phase II Inner Tracker upgrade.

Zhi Zheng (U. Michigan) "Physics with the same-sign dilepton and multilepton events"
2020-01-09 16:00 - 17:00 | 50B-4205
Abstract:
Despite of the discovery of a Higgs-like particle in 2012, there are still many unanswered questions. Studying events with the same-sign dilepton and multilepton (SSML) may help to gain insight into those questions. In this presentation, I will give an overview of physics and challenges related to the analyses of SSML events, focusing on the three analyses I worked on, namely, search for beyond standard model physics, studies of ttH and ttW production and search for four-top production with the ATLAS detector.

Marjon Moulai (MIT) "Unstable Sterile Neutrinos in IceCube and Beyond
2020-01-14 16:00 - 17:00 | HYBRID 50A-5132 (Sessler Conference Room), https://lbnl.zoom.us/j/91782268585, 50A-5132
Abstract:
Long-standing anomalies in short-baseline neutrino oscillation experiments suggest the existence of a new particle: the sterile neutrino. Unlike other neutrinos, sterile neutrinos do not interact via the weak nuclear force. Global fits to experimental data find a significant preference for a 3+1 sterile neutrino model, which introduces a fourth, heavier mass eigenstate, over the Standard Model with three massive neutrinos. However, disagreement between the preferred parameter regions in the appearance and disappearance datasets suggest that something beyond the 3+1 model is needed. In this talk, I will address this problem in two ways: the first is a new, unique search for sterile neutrinos, and the second is an unstable sterile neutrino model. IceCube, a gigaton ice-Cherenkov detector, is uniquely sensitive to a signature of sterile neutrinos that occurs for neutrinos traversing the earth at TeV energies. I will present the new 3+1 sterile neutrino search result from IceCube using eight years of data. Then I will discuss a sterile neutrino model involving neutrino decay. I will present: the phenomenology of this model in the case of IceCube; the result of incorporating IceCube data into recent global fits; and finally, the status of an eight-year search for unstable sterile neutrinos in IceCube.

Daniel Joseph Antrim (UCI) "It Takes Two to Lambda: A New Dilepton Channel for the Search for Higgs Boson Pairs and a Pair of New Small Wheels for the Upgrade of the ATLAS Detector at CERN"
2020-01-16 16:00 - 17:00 | INPA Common Room (50-5026), 50-5026
Abstract:
The rich program of study opened up by the discovery of a 125 GeV boson in 2012 so far leads us to consider this particle to be the Higgs boson as predicted by the Standard Model (SM) of particle physics, the particle famously responsible for providing elementary particles their masses. To be sure that this is the case, the last-remaining fundamental parameter of the SM — the Higgs self-coupling parameter, “lambda” — will have to be measured and checked for consistency with SM-prediction. In the SM, the parameter lambda gives structure to the Higgs vacuum and is therefore fundamental to our understanding of electroweak physics and symmetry breaking that is paramount to our understanding of the Universe. Measurement of lambda at the LHC will proceed via the study of ultra-rare pp collision events in which Higgs boson pairs (HH) are produced. If the LHC is to have a chance at making meaningful statements about lambda, all avenues of study of HH must be sought out. In this talk I will therefore discuss a promising brand new channel in the search for Higgs boson pairs that I have developed and introduced over the past several years using the ATLAS detector at CERN. Additionally, with the foreseen increases in pp collision intensities over the next decades, the ATLAS detector will have to be upgraded if the physics program is to remain successful. This is especially true if we wish to have any hope of observing HH events. With this in mind, I will also touch upon my involvement in the on-going upgrade of the forward muon system of the ATLAS detector, the so-called “New Small Wheel” (NSW) Upgrade, which comprises an upgrade of over 60% of ATLAS’ muon spectrometer coverage as well as being the largest on-going upgrade of any of the LHC experiments.

Damian Goeldi (Carleton U) "Enhancing the Physics Reach of the DUNE far Detector"
2020-01-21 16:00 - 17:00 | Zoom Talk, 50A-5132, Berkeley, ca, 94720
Abstract:

DUNE is a planned long-baseline neutrino oscillation experiment measuring μ disappearance and e appearance in an accelerator μ beam (arXiv:1601.05471). Its primary goals are measuring CP violation in the lepton sector, determining the ordering of the three neutrino masses, and precision tests of the three-flavour neutrino oscillation paradigm. Furthermore, DUNE aims to investigate proton decay, and the neutrino flux from the core-collapse of a potential supernova within our galaxy. Finally, it has recently been proposed (DOI:10.1103/PhysRevLett.123.131803) that an upgraded far detector design could enable DUNE to shed light on the current 2 discrepancy between reactor and solar neutrino oscillation measurements. Liquid argon time projection chambers (LArTPCs) were chosen as primary detectors for the DUNE near and far detector complexes due to their excellent tracking and calorimetry performance. The far detector complex will consist of four multi-kt detectors, whose baseline design is of semi-monolithic nature (arXiv:1807.10327), segmenting each module along the drift axis into multiple TPCs. In contrast a near detector LAr component needs to be fully segmented due to the high event rates present there. This motivated the development of ArgonCube, a fully modular TPC concept, alleviating high-voltage requirements, reducing optical pile-up, and providing ambiguity-free tracking and calorimetry by means of a pixelated charge readout. While near detector development is well on track, we have recently made the case for an ArgonCube far detector design (arXiv:1908.10956). Full segmentation would alleviate high-voltage requirements drastically. Combined with the pixelated charge readout eliminating bulky wire frames, the sensitive volume could be increased significantly. A pixelated charge readout providing true 3D tracking free from ambiguity would simplify event reconstruction. Reconstruction efficiency would no longer depend on the incident angle of an interaction, enhancing sensitivity to isotropic events, such as proton decay, solar, and supernova neutrinos. This talk will first introduce the ArgonCube concept, and show how it addresses the DUNE near detector challenges. I will then focus on the potential of an ArgonCube far detector to enhance DUNE’s capabilities in regards to its secondary physics goals, as well as the changes required compared to the near detector design.

Special RPM | Gregor Kasieczka (Hamburg U) "Faster, Deeper, Stronger: Machines Learn Particle Physics
2020-01-22 16:00 - 17:00 | HYBRID 50A-5132 (Sessler Conference Room), https://lbnl.zoom.us/j/91782268585, 50A-5132
Abstract:
Many experimental results from both particle and astrophysics hint that the Standard Model (SM) of particle physics cannot be a complete theory of Nature. However, in its first years of operation, the Large Hadron Collider at CERN was very successful in excluding large regions of parameter space for potential models beyond the SM. We present how deep learning can be used to search for deviations from the SM in a model independent way. Beyond searching for new physics, we explore ways to increase the robustness and understanding of network decisions and show how generative models can speed up simulations.

Michal Zamkovsky (CERN) "New result on K+→π+vv ̅ from the NA62 experiment"
2020-01-23 16:00 - 17:00 | HYBRID 50A-5132 (Sessler Conference Room), https://lbnl.zoom.us/j/91782268585, 50A-5132
ABSTRACT:

The decay K+→π+vv ̅, with a very precisely predicted branching ratio of less than 10exp(-10), is one of the best candidates to reveal indirect effects of new physics at the highest mass scales. The NA62 experiment at the CERN SPS is designed to measure the branching ratio of the K+→π+vv ̅ with a decay-in-flight technique. NA62 took data so far in 2016-2018. Statistics collected in 2016 allowed NA62 to reach the Standard Model sensitivity for K+→π+vv ̅, entering the domain of 10-10 single event sensitivity and showing the proof of principle of the experiment. Thanks to the statistics collected in 2017, NA62 surpasses the present best sensitivity. The analysis strategy is reviewed and the preliminary result from the 2017 data set is presented.

Vivek Singh (LBNL) "New results for Neutrinoless Double-Beta Decay search in 130Te with CUORE "
2020-01-28 16:00 - 17:00 | HYBRID 50A-5132 (Sessler Conference Room), https://lbnl.zoom.us/j/91782268585, 50A-5132
Abstract:
The CUORE experiment — with a detector array comprising 988 cube-shaped radiopure natTeO2 crystals — is the world’s largest and most sensitive low temperature calorimetric search for neutrinoless double beta (0νββ) in 130Te. We completed the construction of the experiment in August 2016 and started science data taking in Spring 2017. Since our first results from Fall 2017, we have quadrupled our exposure and have bettered the sensitivity for the $0
ubetabeta$ search using analysis improvements. In this talk, I will delve into the data taking campaign, analysis techniques, and discuss the recent physics results from the full CUORE datasets accumulated over the last two years.

Huilin Qu (UCSB) "Search for the Higgs Boson Decaying to Charm Quarks with the CMS Experiment"
2020-01-30 16:00 - 17:00 | HYBRID 50A-5132 (Sessler Conference Room), https://lbnl.zoom.us/j/91782268585, 50A-5132
Abstract:

After the discovery of the Higgs boson at the LHC, thoroughly studying the properties of the Higgs boson has become one of the top priorities of the LHC physics program. Measurement of the decay of the Higgs boson to charm quarks provides a direct probe of the Higgs coupling to second-generation quarks, therefore it is crucial for understanding the structure of Yukawa couplings. However, such a measurement is extremely challenging at the LHC due to large backgrounds. Recently, a search for the Higgs boson decaying to charm quarks has been performed in the CMS experiment. Novel approaches and advanced machine learning-based techniques for the Higgs boson reconstruction and charm quark identification are adopted in this analysis, leading to significantly improved results compared to previous experimental searches.

Matthew Solt (Stanford U) "The Heavy Photon Search Experiment
2020-02-04 16:00 - 17:00 | HYBRID 50A-5132 (Sessler Conference Room), https://lbnl.zoom.us/j/91782268585, 50A-5132
Abstract:

The Heavy Photon Search (HPS) experiment is a fixed target experiment at Jefferson Lab searching for a new dark-force mediator called a heavy photon (or dark photon or A’). A heavy photon is a hypothetical U(1) vector boson that couples to the Standard Model photon through kinetic mixing, and thus can be produced in a process analogous to bremsstrahlung by an electron beam incident on a dense target. If kinematically allowed, subsequent decays into e+e- pairs can be detected by the HPS detector – a compact, large acceptance spectrometer consisting of a silicon vertex tracker and lead-tungstate electromagnetic calorimeter. For large couplings, heavy photons would appear as a resonance peak in the invariant mass spectrum on top of a large QED background. For sufficiently small couplings, heavy photons are long-lived and would appear as decay vertices displaced from the target beyond a prompt QED background. In this talk, I will discuss the motivation for heavy photons and the HPS detector. I will then focus on the displaced vertex analysis and discuss the results from our engineering in 2015 (1.06 GeV beam energy), the ongoing analysis of the engineering run in 2016 (2.3 GeV beam energy), and finally the upgrades and commissioning of our most recent physics run in 2019 (4.55 GeV beam energy).
