LBNL Physics Division Research Progress Meetings

Karol Krizka (U. Chicago) "Dark Matter Mediators and Dijet Resonance Searches by the ATLAS Experiment"
2016-12-20 16:00 - 17:00 (America/Los_Angeles) | Zoom Talk, 50A-5132, Berkeley, ca, 94720
Abstract:Using 13 TeV pp collisions, the ATLAS experiment has used a collection of dijet resonance searches (high-mass dijet, trigger-level dijet and dijet+ISR) to search for new particles with masses ranging from 200 GeV to 7 TeV. This talk summarizes the searches, with a focus on new the “dijet+ISR” channel. The dijet+ISR analysis is an LHC-first and reaches mediator masses below 500 GeV by utilizing an ISR jet or photon to trigger the event. This region was previously accessible only by the LEP and Tevatron experiments. This is an important improvement for Dark Matter simplified models, based on a mediator between a Dark Matter particle and the Standard Model. Cosmological measurements of the Dark Matter relic density prefer the mediator mass to be sub-TeV. By searching for a dijet resonance produced by the mediator decaying back into quarks, powerful new limits are set on the simplified Dark Matter models.

Nan Lu (U. Michigan - Ann Arbor) ""Higgs Boson Property Measurements with ATLAS at the LHC""
2016-12-15 16:00 - 17:00 | Zoom Talk, 50A-5132, Berkeley, ca, 94720
Abstract:
“After the discovery of Higgs boson by the ATLAS and CMS experiments at the LHC in 2012, a new era of studying the properties of this new particle has begun. In this talk, I will give a brief overview of Higgs boson property measurements using LHC Run 1 data, and then focus on the measurements of Higgs boson production in the four-lepton decay channel and in combination with the diphoton decay channel using 13.3 fb-1 to 14.8 fb-1 of Run 2 data collected at √s=13 TeV by the ATLAS detector.”

ChangHoon Hahn (NYU) "Fundamental Physics with Galaxy Clustering"
2016-12-13 16:00 - 17:00 | Zoom Talk, 50A-5132, Berkeley, ca, 94720
Abstract:

Galaxies’ connection to the cosmic web allows us to use them to trace the matter distribution in the Universe and make precise measurements of large scale structure. The next galaxy surveys (eBOSS and DESI) will expand the cosmic volumes probed with galaxies by an order of magnitude and provide unprecedented statistical power. The main challenges for realizing their full potential are methodological.

I will present how the main challenges can be solved with robust treatment of systematics (e.g. fiber collisions), accurate probabilistic inference, and higher order statistics. By overcoming these challenges and unlocking the full potential of eBOSS and DESI, I will present how we can measure the growth of structure and total neutrino mass with unprecedented precision.

Johanna Nagy (Case Western) "Probing Inflation with SPIDER, a Balloon-Borne CMB Polarimeter"
2016-12-08 16:00 - 17:00 | Zoom Talk, 50A-5132, Berkeley, ca, 94720
Abstract:

The generation of a stochastic gravitational wave background is a key prediction of cosmological theories of inflation. At large angular scales, these gravitational waves imprint a “B-mode” polarization pattern in the Cosmic Microwave Background, providing a new window into the physics of the early universe and helping to constrain and distinguish between inflationary models. SPIDER is a balloon-borne telescope that has been uniquely optimized to search for the inflationary B-mode signature in the CMB. Over the course of two Antarctic flights, SPIDER will make polarization maps over 10% of the sky in three frequency bands with degree-scale angular resolution. After an overview of the instrument and science goals, preliminary results from SPIDER’s 2015 flight will be presented along with a summary of progress towards the second flight.

Cristián H. Peña (Caltech) "Searches for New Physics at CMS and Precision Timing Detectors"
2016-12-06 16:00 - 17:00 | Zoom Talk, 50A-5132, Berkeley, ca, 94720
ABSTRACT:

Searches for dark matter and supersymmetry are part of an ambitious and well motivated quest to discover new physics at the LHC. In the first part of this seminar I will be presenting two novel searches for new physics using the data collected by the CMS experiment. The first is a search for dark matter in multijet events using the razor variables to discriminate signal from background events. The second is a search for anomalous production of Higgs bosons in association with jets, where the Higgs is reconstructed through its diphoton decay channel. The second part of my seminar will cover cutting edge detector R&D towards a device with ~10 ps time resolution. Such detectors will have a positively disruptive impact in future experiments such as the High Luminosity upgrade of the LHC by maintaining the current event reconstruction performance, which is expected to otherwise significantly deteriorate due to the high pileup environment.

Evan Pease (Yale) "Searching for WIMPs and More: Results from 3 Years of Underground Science with the LUX Experiment"
2016-12-01 16:00 - 17:00 | Zoom Talk, 50A-5132, Berkeley, ca, 94720
ABSTRACT:
The Large Underground Xenon (LUX) experiment recently concluded underground operationat the Sanford Underground Research Facility. This talk will cover the full LUX search for dark matter in the form of Weakly Interacting Massive Particles (WIMPs) and will describe new measurements of xenon’s properties and new analysis techniques developed for further LUX science.

SPECIAL SEMINAR: Wai Ling Kimmy Wu (Stanford) "Constraining Inflation with BICEP/Keck and SPT"
2016-11-30 12:00 - 13:00 | Zoom Talk, 50A-5132, Berkeley, ca, 94720
Abstract:

Inflation generically predicts a background of stochastic gravitational waves. In the standard cosmological model LCDM, these primordial gravitational waves (PGW) are the only source to the odd-parity (curl) B-mode polarization on the Cosmic Microwave Background (CMB) at the epoch of recombination. Therefore, we can learn much about inflation by constraining or potentially detecting primordial gravitational waves. In this talk, I will present two frontiers that advance the search for primordial gravitational waves: instrumentation of BICEP3 and delensing with SPTpol. I will conclude with the future outlook of such search with CMB-S4.

In the first part of the talk, I will discuss the design and performance of BICEP3 — the path-finder of BICEP/Keck program’s Stage-3 effort. The BICEP/Keck telescopes are small aperture (~0.5m) cryogenic refractors that focus on measuring the degree-angular scale feature of the PGW-generated B modes. BICEP3 has ~10x optical throughput compared to BICEP2 due to a larger field-of-view and aperture size. As a result, we adopt new designs in BICEP3 for thermal filtering, optical elements selection, and detector modules packing. We deployed BICEP3 in the Austral summer of 2014-2015 and upgraded the instrument after the first season of testing and observations. I will present the improvements of the noise levels due to this upgrade.

The second part of my talk will focus on delensing SPTpol data. Gravitational lensing of primordial (curl-free) E modes generates B modes. These lensing B modes are a source of foreground contamination to detecting the PGW-generated B modes. We can characterize and reduce the lensing B-mode contribution through a technique called “delensing.” I will present results of a first demonstration of delensing on polarization data. In this work, we delens B-mode maps from multi-frequency SPTpol observations of a 100 deg^2 patch of sky by subtracting a lensing B template constructed from two components: SPTpol E-mode maps and a lensing potential map formed from a Herschel 500 μm map of the CIB. In addition, we build and use a suite of realistic simulations to study the current limitations and expected future improvements in delensing with implications for future experiments.

Scott Kravitz (Stanford) "Identification of Single Barium Atoms for the nEXO Neutrinoless Double Beta Decay Experiment"
2016-11-29 16:00 - 17:00
Abstract:
nEXO is a next-generation experiment designed to search for neutrinoless double beta decay of xenon-136 in a liquid xenon time projection chamber. Positive observation of this decay would determine the neutrino to be a Majorana particle, as well as measure the absolute neutrino mass scale. In order to greatly reduce background contributions to this search, the collaboration is developing several “barium tagging” techniques to recover and identify the decay daughter, barium-136. Barium tagging may be available for a second phase of nEXO operation, allowing for neutrino mass sensitivity beyond the inverted mass hierarchy. Tagging methods for this phase include barium-ion capture on a probe with identification by resonance ionization laser spectroscopy (RIS). An apparatus has been built to deposit barium atoms onto a surface and recover them using infrared laser desorption followed by RIS, with the resulting ions passing through a time-of-flight mass spectrometer for further identification. Recent results from this system will be presented, including those from incorporating an argon ion gun which allows for improved cleaning and preparation of the barium deposition substrate.

John Bradmiller-Feld (UCSB) "An Inclusive and Generic Search for Supersymmetry in the Multijet + Missing Momentum Final State Performed on pp Collision Data Collected with the CMS Detector"
2016-11-22 16:00 - 17:00 | Zoom Talk, 50A-5132, Berkeley, ca, 94720
ABSTRACT
For the past two years, the LHC has collided protons at a record-high center-of-mass energy of 13 TeV. This time has provided an opportunity to search for beyond standard model particles at the TeV scale, including those predicted by supersymmetry, with unprecedented sensitivity. I will present an overview of a generic search for strongly-produced supersymmetric particles in pp collisions in the multijet + missing transverse momentum final state. The data sample corresponds to 12.9 fb-1 recorded by the CMS experiment in 2016. I will review the theoretical and experimental motivation for this search, then describe the central challenges of the analysis, namely the data-driven measurements of the standard model backgrounds. Finally, I will summarize the results of the analysis, and look ahead to possible directions for this and similar searches in the coming years.

Robert Kirshner (Moore Foundation) "Doing WFIRST Science Now: Supernovae in the Infrared"
2016-11-17 16:00 - 17:00 | Zoom Talk, 50A-5132, Berkeley, ca, 94720
Abstract.- An infrared-capable 2.4m telescope is presently in orbit: the Hubble Space Telescope. This makes it possible to do rest-frame infrared observations of Type Ia supernovae. In the infrared, SN Ia are more nearly standard candles and there is less obscuration by dust. I will give a status report on RAISIN2, an HST program that tiptoes into the realm of WFIRST science today.

Emmanuel Schaan (Princeton) "Non-linearities in the large-scale structure: noise and signal"
2016-11-15 16:00 - 17:00 | Zoom Talk, 50A-5132, Berkeley, ca, 94720
Abstract:
The primordial density perturbations seen in the cosmic microwave background have collapsed under gravity to form the large-scale structure we see in the universe today. This evolution is non-linear, and therefore introduces coupling between Fourier modes that would otherwise be independent. I will present two consequences of this non-linear coupling.
Halo sample variance (arXiv:1406.3330):
Gaussian estimates for the errors in large-scale structure measurements exaggerate the scientific impact of these measurements. Non-linear evolution and finite volume effects are both significant sources of non-Gaussian covariance, which reduce the ability of power spectrum measurements to constrain cosmological parameters. I will present a joint likelihood for cluster counts, power spectrum and bispectrum, including the non-Gaussian covariances, and show that a joint analysis of these observables can reduce this “information loss”. In some cases, the resulting improvement on cosmological parameters is equivalent to doubling the survey area.
Lyman-alpha – CMB lensing bispectrum (arXiv:1607.03625):
The Lyman-alpha forest seen in the spectra of quasars is a powerful tool for constraining warm dark matter models and the neutrino masses, as well as properties of the intergalactic medium. Its use as a cosmological probe relies on modeling the connection between neutral gas and dark matter. I will present the first detection of the correlation between the Lyman-alpha forest and the cosmic microwave background, using data from BOSS and Planck. This signal quantifies the non-linear response of the neutral hydrogen to a large-scale overdensity, and thus tests our understanding of the connection between neutral gas and the dark matter.

Erez Etzion (Tel-Aviv U.) "Higgs hunting episode II - Searches for Beyond the SM Higgs at the LHC"
2016-11-15 14:00 - 15:00 | Zoom Talk, 50A-5132, Berkeley, ca, 94720
ABSTRACT
The discovery of the “Higgs like” particle in summer 2012 completed about fifty years of search. In short time with significantly more data we renamed it to be the Higgs particle and continued with studying its characteristic. In parallel to the precision measurements it increased the effort to look for additional Higgs like particles and Higgs related extensions to the Standard Model. I will review some of these searches with the ATLAS and CMS experiments focusing on the recent data collected by ATLAS in LHC pp collisions at centre of mass of 13 TeV.

Reserved
2016-11-10 16:00 - 17:00, 2016-11-08 16:00 - 17:00, 2016-11-03 16:00 - 17:00, 2016-11-01 04:00 - 17:00 | Zoom Talk, 50A-5132, Berkeley, ca, 94720

Bruce Schumm (UCSC) "Supersymmetry Searches at the LHC: Status and a Thought or Two about the Future"
2016-10-27 16:00 - 17:00 | Zoom Talk, 50A-5132, Berkeley, ca, 94720
Abstract:

I’ll remind us all of the motivation for Supersymmetry searches at the LHC, and provide a general overview of the status of the search. Since, even after results making use of in excess of 10 fb-1 of 13 TeV data we see no significant signals, I’ll end with a discussion of how imperiled SUSY may or may not be at this point.

Marilena Loverde (Stony Brook Univ.) "Neutrinos, Quintessence and Structure Formation in the Universe"
2016-10-20 16:00 - 17:00 | Zoom Talk, 50A-5132, Berkeley, ca, 94720
Abstract:
The large-scale structure of our universe (the distribution of galaxies on very large-scales for instance) contains a wealth of information about the origin, evolution, and matter content of the universe. Extracting this information relies crucially on understanding how galaxies and other biased objects trace the large-scale matter distribution. In a universe such as our own, with both cold dark matter and massive neutrinos, or in alternative cosmologies with clustered quintessence, this problem is much more complicated. I will discuss new tools that my group has developed to study gravitational evolution in cosmologies with multiple fluids, the novel signatures we have identified including a new probe of neutrino mass, and the broader implications for models of large-scale structure.

Greg Aldering, Bob Cahn, Alex Kim, and Saul Perlmutter (LBNL) "Type Ia Supernova Program at LBNL: Status and Plans"
2016-10-18 16:00 - 17:00 | Zoom Talk, 50A-5132, Berkeley, ca, 94720
ABSTRACT:
Supernovae remain a central part of dark energy science, complementing the programs with BAO and weak lensing. The LBNL group is active with the nearby supernova search with the SN factory, a role in the intermediate-redshift DES supernova program, and the collection of increasing numbers of high-z Type Ia supernovae. The SuperNova factory has revealed a number of systematic issues and some means to address them. While LSST will discover hundreds of thousands of supernovae, only if the systematic issues can be addressed will a Stage-IV experiment be possible. Combining WFIRST and LSST with what is being learned at the SN factory and at DES can provide the path to Stage-IV.

Hans Walter Rix (Max Planck) "Fuel Exploration in the Early Universe: The ALMA Spectroscopic Survey of the Hubble Ultra Deep Field"
2016-10-13 16:00 - 17:00 | Zoom Talk, 50A-5132, Berkeley, ca, 94720
Abstract:
Much of the exploration of the high-redshift
Universe has focussed on first finding sites of ongoing star formation.
This can then lead to pointed follow-up of how much
cold (molecular) gas there is that feeds this star formation.
ALMA now enables ‘blind’ surveys for molecular gas, the fuel
supply for galaxy formation at early epochs.
I will report on initial results of what such surveys can yield.

Nick Kaiser (Hawaii) "The Physics of Gravitational Redshifts in Clusters of Galaxies"
2016-09-15 16:00 - 17:00 | Zoom Talk, 50A-5132, Berkeley, ca, 94720
ABSTRACT:
Wojtak, Hansen and Hjorth and others have measured the long-predicted gravitational redshift of light escaping from galaxy clusters using Sloan Digital Sky Survey data. The effect is very small, corresponding to a velocity shift of only ~10 km/s in clusters with internal random motions of order 600 km/s, but the result appears to be robust and is in good agreement with general relativity predictions and possibly in conflict with some alternative theories. It was soon realised that the interpretation of this measurement is more complex than initially thought as one needs to allow for the transverse Doppler (TD) redshift. In this talk I will describe how there are actually two more rather subtle and unexpected physical effects that need to be considered in interpreting these observations; there is a `light cone’ effect that augments the TD shift, and there is a competing effect that reverses the sign of the transverse Doppler effect so that we actually observe a transverse Doppler blue-shift. I will discuss how these observations constrain gravitation theory, and along the way discuss some issues concerning the interpretation of astronomical redshifts in a broader context.

Brian Fujikawa (LBNL) "New Neutrinoless Double Beta Decay Results from KamLAND-Zen"
2016-09-08 16:00 - 17:00 | Zoom Talk, 50A-5132, Berkeley, ca, 94720
Abstract:
KamLAND is a one-kiloton liquid scintillator-based neutrino detector and is one of the recipients of the 2016 Breakthrough Prize in Fundamental Physics for its 2002 investigation of neutrino oscillations. KamLAND-Zen is the current phase of KamLAND, and it is an experiment to search for the neutrinoless double beta decay of Xe-136. In this talk, I will describe the KamLAND experiment and present the new results from KamLAND-Zen. I will conclude by describing the plans and future objectives of KamLAND and KamLAND-Zen.

Neil Spooner (Univ. of Sheffield) " Galactic Signatures and Directional Detection of Particle Dark Matter - the CYGNUS Project and Probing below the Neutrino Floor”
2016-08-25 16:00 - 17:00 | Zoom Talk, 50A-5132, Berkeley, ca, 94720
Abstract:
I’ll briefly review the arguments for and status of particle dark matter searches and then focus on the possibility of looking for a definitive galactic signature. There have been several hints for WIMP dark matter over the years, most notably the DAM/LIBRE annual modulation result. There are new efforts to study this, for instance DM-ICE. I’ll describe the efforts and latest results then focus on prospects for a directional signal using gas Time Projection Chamber technology including the new CYGNUS global collaboration aiming to deploy targets at multiple latitudes deep underground.

Simone Pagan Griso (LBNL) "Highlights from ICHEP on the LHC Results"
2016-08-18 16:00 - 17:00 | Zoom Talk, 50A-5132, Berkeley, ca, 94720
Abstract:

The 38th International Conference on High Energy Physics has
just concluded in Chicago, US. New results from various areas of
high-energy particle physics, as well as neutrino physics, cosmology
and theory were presented in front of about 1400 attendees. In
particular, new results from the LHC experiments were highly
anticipated, using more than 10/fb of proton-proton collision data
collected at a center-of-mass energy of 13 TeV. I will review a
selection of the results presented, focusing on the LHC experiments.

Leslie Rosenberg (Univ. of Washington) "The Axion Dark-Matter Experiment (ADMX)"
2016-08-11 16:00 - 17:00 | Zoom Talk, 50A-5132, Berkeley, ca, 94720
ABSTRACT:
The axion is a hypothetical elementary particle whose existence would explain the
baffling absence of CP violation in the strong interactions. Axions also happen to be a
compelling dark-matter candidate. Axions could comprise the
overwhelming majority of mass in the universe, yet they would be extraordinarily difficult
to detect. However, several experiments, either under construction or in operation,
would be sensitive to even the more pessimistically coupled dark-matter axions. The
Axion Dark-Matter Experiment (ADMX) is perhaps the most powerful of these experiments.
ADMX is in the DOE/NSF Generation-2 portfolio of large dark-matter experiments and is
just transitioning into data-taking. This talk reviews the capabilities and the status of ADMX.

Evan Pease (UCB/Yale) "New results from the 332-live-day exposure of the LUX dark matter experiment"
2016-08-02 16:00 - 17:00 | Zoom Talk, 50A-5132, Berkeley, ca, 94720
Abstract:
Earlier this year the Large Underground Xenon (LUX) experiment completed its final dark matter search from 4850 feet below ground in the Sanford Underground Research Facility in Lead, South Dakota. Between September 2014 and May 2016 the LUX detector amassed 332 live days of exposure in its hunt for dark matter, primarily in search of Weakly Interacting Massive Particles (WIMPs), a favored dark matter candidate. Our analysis of this exposure yields improved and world-leading constraints on the interaction of WIMPs for a wide range of possible masses, placing a 90%-confidence exclusion limit on spin-independent WIMP-nucleon cross-section greater than 2.2 x 10^-46 cm^2 at 50 GeV/c^2 WIMP mass. This result includes a factor of 4 improvement over the previous LUX sensitivity to WIMP masses 100 GeV/c^2 and above. This presentation will include a discussion of changes in detector performance from the previous LUX search in 2013, a description of the “salted” data analysis approach, and a look at the frequent in-situ calibrations of the complex time-varying detector response during 20 months of operation.

Francois Bouchett (IAP) "Latest Cosmological News from the Planck Satellite Project"
2016-07-28 16:00 - 17:00 | Zoom Talk, 50A-5132, Berkeley, ca, 94720
Abstract:
Sketched out in 1992, selected by ESA in 1996, and launched in 2009, the Planck satellite was shut off in 2013, after a measuring mission that exceeded all expectations. The Planck collaboration delivered a first set of cosmological data and results in March 21st 2013, and the full set in February 2015. Part of the data delivery is a “definitive” map of the anisotropies of the Cosmic Microwave Background (CMB), its angular power spectrum together with their full statistical characterization. The 2015 delivery further include pioneering polarisation data. I’ll briefly recall salient scientific results we derived from these data. The Planck collaboration is now working towards a “legacy release” by the end of 2016 which will mark the end of the formal collaboration we set up back in the previous century. To this end, we keep improving further our control on the potential level of residual systematics in the data and in accounting for these uncertainties in the final cosmological results to further enhance the robustness and precision of the constraints posed by Planck. For instance, we announced in May an improved likelihood analysis using detailed end-to-end simulation as well as an improved constraint on the reionization optical depth by using for the first time the E-mode polarisation data from the HFI instrument. This determination fully reconciles the CMB results with other astrophysical measurements of reionization from sources at high redshift. It also gives constraints on the level of reionization at redshifts beyond that of the most distant sources (z > 10). I will further give some perspectives on what is coming next.

Joint Physics and ATAP Divisions Seminar | William Barletta (USPAS/ MIT) & Martin Breidenbach (SLAC) "Accelerator Research in the U.S. for High Energy Physics: A biased perspective"
2016-07-21 16:00 - 17:00 | 50-Auditorium
Abstract:
The U.S. could move boldly toward accelerating transformational accelerator research for high-energy physics. Profound questions remain to be answered in particle physics; recent discoveries reconfirm the value of continued investments. However, going beyond the present generation of high energy accelerators will require changing the capability-cost curve of accelerators, which can only happen through an aggressive, sustained, and imaginative R&D program aimed at building the future accelerators at a dramatically lower cost. Both of us were members of Department of Energy panel that recently studied the potential structure of such a research program. We participated fully in the process and approve the report. Nonetheless, our experience led us to continue and extend our analysis of the issues that will drive accelerator research aimed at future accelerators for high-energy physics with the aim of informing interested physicists from all disciplines, not just accelerator experts. Broadly, we will look at prospects for proton-proton colliders and electron-position colliders – all interlaced with our biases and (and perhaps not politically correct) opinions.

Alan Poon (LBL) "Searches for Majorana Neutrinos"
2016-06-30 16:00 - 17:00 | Zoom Talk, 50A-5132, Berkeley, ca, 94720
Abstract:
Neutrino oscillation experiments have demonstrated conclusively that neutrinos have mass. In many Standard Model extensions neutrinos are favored to be Majorana fermions. A worldwide experimental program to search for this Majorana nature of neutrinos is underway. In this talk, I will review the status of experimental searches for Majorana neutrinos, with the focus on neutrinoless double-beta decay experiments.
I will also give a brief summary on GERDA Phase-II results that were released on June 29.

Kate Scholberg (Duke U.) "What Stubs and Sparkles Will Tell Us About Exploding Stars"
2016-06-23 04:00 - 17:00 | Zoom Talk, 50A-5132, Berkeley, ca, 94720
Abstract:
When a massive star collapses at the end of its life, nearly all of
the gravitational binding energy of the resulting remnant is released
in the form of neutrinos. I will discuss the nature of the
core-collapse neutrino burst and what we can learn about particle
physics and about astrophysics from the detection of these neutrinos.
I will cover supernova neutrino detection techniques in general,
current supernova neutrino detectors, and prospects for specific
future experiments.
