List of past RPMs -- 2016

Jan 12, 2016

Tomo Lazovich (Harvard) "One Higgs, Two Higgs, Old Higgs, New Higgs: the Higgs boson from discovery to new physics with the ATLAS experiment"

The discovery of the Higgs in Run 1 of the LHC provided a more complete picture of the Standard Model and also gave particle physicists a new tool to use in the search for Beyond the Standard Model physics. With center of mass energy now at 13 TeV in LHC Run 2, we are poised to produce new resonances and probe higher energy scales. I will first discuss the challenging WW decay channel of the Higgs and how we went from discovery to the current best measurement of the Higgs cross section and observation of the vector boson fusion production mode. I will then discuss searches for new physics in both resonant and non-resonant production of two Higgs bosons in the 4b final state in Run 2, detailing the advantages and difficulties of using this final state to search for new physics over a wide range of masses.

Jan 14, 2016

Franz Elsner (UCL) "Parameter estimation in cosmology - The Planck likelihood"

Abstract: The inference of cosmological parameters requires the construction of a likelihood function that acts as an interface between theory and observational data. Using the CMB experiment Planck as a worked example, I provide an overview of the challenges associated with the analysis of high-resolution, state of the art experiments. In particular, I will discuss the approximations necessary to make an analysis feasible in practice, the role of nuisance parameters, and tests used to assess the robustness of the results. Reviewing the most important cosmological implications of Planck, I will conclude with an outlook of what we can expect to learn from future experiments.
Jan 19, 2016

Shawn Westerdale (PRINCETON) "Detecting Dark Matter with DarkSide-50"

Abstract: Dark matter constitutes 85% of the matter in the universe, yet despite its abundance, very little is known about it. One popular theory is that dark matter is made of Weakly Interacting Massive Particles, or WIMPs. Due to the low cross section for WIMP-nucleus interactions, the event rate of WIMPs in a detector is expected to be very low. This means that detectors must have extraordinarily low background rates and good background rejection in order to be able to detect these rare events above their background. DarkSide-50 is a 50 kg liquid argon time project chamber, nested inside of a 30 tonne boron-loaded liquid scintillator neutron veto, which is inside a 1000 tonne water Cherenkov muon veto. Since neutrons can leave a signal identical to what is expected from WIMPs, neutrons are the most dangerous background to such an experiment. I will talk about the latest results from the DarkSide-50 detector, which recently published results from 120 days of running background free. This talk will also have a focus on the design and performance of the neutron veto system that enables the detector to remain free of neutron backgrounds by vetoing neutrons with > 99.2% efficiency.
Jan 21, 2016

Walter Pettus (YALE/WISCONSIN) "The DM-Ice Dark Matter Experiment"

Abstract: DM-Ice is a phased program towards the first direct detection search for dark matter in the Southern Hemisphere with a quarter ton scale NaI(Tl) crystal array.  It will provide an understanding of the modulation signal reported by DAMA by running arrays at both Northern and Southern Hemisphere sites.  A first generation experiment with 17-kg of active mass, DM-Ice17, was deployed in December 2010 at a depth of 2457 m under the ice at the geographic South Pole and has concluded its 3.5-yr primary physics run.  An active R&D program is ongoing at the Boulby Underground Laboratory to investigate clean crystals and optimize detector components.  A worldwide consortium of sodium iodide experiments is now preparing two 100-kg arrays to start data taking in 2016.  I will report on the successes of the DM-Ice program and how the stage is set for definitively testing the DAMA signal anomaly.
Jan 26, 2016

Gaosong Li (Shanghai Jiao Tong University) - "Daya Bay Experiment"

Abstract: The Daya Bay Reactor Neutrino Experiment is designed to measure the neutrino mixing angle with unprecedented precision. The experiment utilizes multiple pairs of identical antineutrino detectors (ADs) at different baselines from three pairs of reactor cores to minimize systematic uncertainties. In 2012, Daya Bay made the first definitive measurement of a non-zero value for $\theta_{13}$ using the first 55 days of data collected with six ADs by measuring the antineutrino rate deficit. With the final two ADs installed, Daya Bay resumed data taking in full 8-AD configuration in late 2012. More than 1 (0.15) million electron antineutrino candidates had been collected with the near (far) site detectors by the end of 2013, significantly improving the precision on . In addition to precision measurement of neutrino oscillation parameters, analyses exploring various other physics potential are carried out. In this talk, I will focus on the calibration system. I will present calibration related works I have been working on to improve the detector absolute efficiency and neutrino oscillation analysis. I will also present the results on neutrino oscillation parameters from an independent analysis.
Feb 04, 2016

Frank Golf (UCSB) "Searching for New Physics with the Large Hadron Collider"

Abstract: After a two-year shutdown, the LHC restarted proton-proton collisions in 2015 with an increase in center-of-mass energy to 13 TeV.  I describe some early results with data from the first year of running and plans for the significantly larger datasets that we expect to collect in the coming years.

Feb 11, 2016

Neal Dalal (Univ. Illinois at Urbana-Champaign) "Detecting Dark Matter Substructure Using ALMA"

Abstract:  Dark matter halos surrounding galaxies are expected to contain copious substructure, in the form of gravitationally bound subhalos.  Local Group observations suggest that our Galaxy has a deficit of substructure (the Missing Satellites Problem), possibly indicating new physics in the dark sector.  I will describe how gravitational lensing may be used to measure the amount of dark substructure that exists in typical galaxy halos.  In particular, I will explain how observations by the newly commissioned ALMA observatory of dusty galaxies from CMB surveys can probe halo substructure.  I will show first results from our ALMA Cycle 2 observations, and argue that ALMA should be able to answer the Missing Satellites Problem in upcoming years.
Feb 18, 2016

Special RPM | Daniel Holz (U. Chicago) " Observation of Gravitational Waves from a Binary Black Hole Merger"

We will provide an overview of LIGO's first event. The signal is consistent with the merger of two black holes of ~30 Msun at a distance of ~400 Mpc. We will discuss some aspects of the detection, including parameter estimation, tests of general relativity, and astrophysical constraints.
Feb 23, 2016

Andreu Font-Ribera (LBNL) "Studying the Expansion of the Universe with Quasar Spectra"

Abstract:  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 several 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 (Delubac et al. 2015), and from its cross-correlation with quasars (Font-Ribera et al. 2014). 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. In the near future, the Dark Energy Spectroscopic Instrument (DESI) will increase this data set by an order of magnitude. DESI will provide an exquisite measurement of the expansion over cosmic time, while at the same time addressing other interesting questions: the sum of the mass of the neutrino species, properties of dark matter particles, tests of general relativity and the shape of the primordial power spectrum of density fluctuations.
Feb 25, 2016

Heather Gray (CERN) " Chasing Beauty: Probing the Higgs Using B-Quarks

In the Standard Model, the Higgs has the highest probability to decay to b-quarks, yet this is one of the most challenging channels to observe at the LHC. I will explain the importance of measuring the coupling to the Higgs b-quarks, outline the ATLAS Run-1 H->bb analysis and review the current status of our knowledge of the coupling of the Higgs to b-quarks. I will also discuss how we might expect to observe the coupling of the Higgs to b-quarks during Run-2 of the LHC or in the future.  Finally, I will discuss future measurements towards the Higgs self-coupling to explore the mechanism of electroweak symmetry breaking.

Mar 01, 2016

Mariarosaria D'Alfonso (CERN) "New Physics at LHC: Energy and Precision Frontiers"

The evidence for the existence of dark matter in the universe is overwhelming; yet its exact nature, its mass(es) and coupling constants, are completely unknown. If kinematically accessible at colliders, these particles are expected to be produced directly or in the cascade of other new hypothetical particles. At the same time, the global fit to electroweak precision data impressively demonstrates the predictive power of Standard Model. Increasing the theoretical and experimental precision on electroweak observables may reveal inconsistencies between measurements and predictions due to the presence of new particles in the loop corrections. I will discuss a discovery physics program to take the full advantage of the ability of the LHC to probe the energy and the precision frontiers. I will highlight how improved scientific instruments with new possibilities will enable these searches.

Mar 03, 2016

Julien Guy (LPNHE) " The Prospects and Challenges of the Dark Energy Spectroscopic Instrument

Abstract : I will present the prospects of DESI for the measurement of Dark Energy in light of a decade of efforts to unveil its nature, from the discovery of cosmic acceleration with type Ia supernovae, to the most recent results with supernovae and baryon acoustic oscillations (BAO). DESI will map cosmic expansion up to redshifts of 3, anchoring distances at low redshift to the era of past deceleration with an order of magnitude gain in precision compared to current surveys. DESI data will offer a stringent test of the standard model of cosmology, with important possibilities for discovery. The project, however, is not free from experimental challenges. I will review the analysis efforts needed to extract the whole potential of the BAO probe, from the optimization and calibration of the efficiency of the redshift survey, to the characterization of the instrumental noise in the Lyman-alpha forests.
Mar 08, 2016

Sho Uemura (Stanford) "The Heavy Photon Search Experiment at Jefferson Lab"

Abstract: The Heavy Photon Search (HPS) is a new experiment at Jef ferson Lab searching for massive U(1) vector bosons (also known as heavy photons, dark photons, or A prime with a weak e ffective coupling to electric charge. The heavy photon is motivated as part of a hidden sector" model of dark matter, where it would mediate the self-interaction of dark matter and the interaction of dark and ordinary matter. HPS is sensitive to heavy photons of mass 10-500 MeV with coupling strength episilon squared of 1e-5 to 1e-10. The HPS experiment is designed to produce heavy photons in a process analoguous to bremsstrahlung using an electron beam on a fixed target, and detect decays to e+e pairs with two signatures (invariant mass resonance and displaced decay vertex). The detector is a compact, large-acceptance forward spectrometer comprising a silicon microstrip tracker for momentum measurement and vertexing and an electromagnetic calorimeter for triggering on e+e. Precise beamline controls, high-rate trigger and DAQ, and good time resolution are needed for a detector that comes within 0.5 mm of the beam and is sensitive down to  15 mrad from the beam plane, and must cope with the intense beam background in this environment. A low-mass tracker and clean track reconstruction are needed for the best sensitivity. This talk will describe the HPS experiment and its current status after test, commissioning, and engineering runs.
Mar 10, 2016

Shirley Ho (Carnegie Mellon University) " Joining Forces Against the Dark Universe: From the Cosmic Microwave Background to the Large Scale Structure"

Despite tremendous recent progress, gaps remain in our knowledge of our understanding of the Universe. We have not yet pinned down the properties of dark energy, nor have we confirmed Einstein’s theory of Gravity at the largest scales.Current and upcoming large sky surveys of the Cosmic Microwave Background (CMB), Large Scale Structure (LSS) in galaxies, quasars and Lyman-alpha forest present us with the best opportunity to understand  properties of the Universe.
I will first review recent cosmology results from CMB and LSS, concentrating on BOSS results using Baryon Acoustic Oscillations and Redshift Space Distortions. I will then introduce novel cosmological probes which combine CMB with LSS directly. These novel probes will open new windows into the momentum field of the Universe and Gravity at the largest scales. I will finally put these into the context of upcoming surveys such as Dark Energy Spectroscopic Instrument (DESI), Wide Field Infrared Survey Telescope (WFIRST) and CMB S4.

Mar 15, 2016

Dominick Olivito (CERN) "Searches for Dark Matter and Supersymmetry at 13 TeV with CMS"

Results will be presented from searches looking for a large transverse momentum imbalance motivated by dark matter and supersymmetry, using a sample of proton-proton collisions collected at a center-of-mass energy of 13 TeV in 2015 with the CMS detector at the LHC.  An inclusive analysis for hadronic jets and missing transverse momentum (MET), measured using the MT2 variable, will be covered, as well as an analysis searching for a pair of leptons with opposite-sign and the same flavor, hadronic jets, and MET.  The latter analysis looks for one of two features in the mass spectrum of the lepton pair: either a resonance compatible with the Z boson mass or a kinematic edge.  The results of each search are interpreted in simplified models of supersymmetry.

Mar 17, 2016

Michael Kagan (Stanford) "Exploring the TeV Energy Regime with Double Higgs Production at the LHC"

The discovery of the Higgs boson by the ATLAS and CMS experiments at the Large Hadron Collider provides a novel tool to search for signs of physics beyond the Standard Model at the LHC. The Higgs boson is central to two frontiers in high energy physics today: the fundamental understanding of the mechanism for Electroweak Symmetry Breaking and for the generation of particle masses, and the exciting prospect of discovering new heavy TeV-scale particles interacting with the Higgs boson.  Such new particles are predicted in theories of physics beyond the Standard Model which may incorporate  additional symmetries or extra dimensions of space-time.   In this talk, I will focus on how the search for di-Higgs boson production using the four bottom quark decay channel is central to probing both of these frontiers. I will discuss the critical developments in bottom quark identification that have enabled such searches for the first time.  I will also discuss key advancements in high performance silicon pixel detectors and in new pattern recognition techniques inspired by cutting-edge machine learning and computer vision methods that are extending the future discovery potential at the LHC.

Mar 24, 2016

Simone Pagan Griso (LBNL) "Search for Supersymmetric Long-Lived Particles with the ATLAS Experiment"

Abstract: Supersymmetry is a well motivated extension of the Standard Model of particle physics, although its realization in nature has yet to be proven. The main efforts at the Large Hadron Collider to probe for supersymmetry at the electroweak mass scale focus on the so-called "prompt" signatures. In these cases, the super-symmetric partners of the known Standard Model particles either decay close to the production point, within the detector resolution, or traverse the detector with no strong interaction, leaving usually a large imbalance of momentum in the transverse plane. In this seminar I will focus on searches for supersymmetric particles with a significant lifetime, that could be either directly or indirectly measured. Such particles can easily evade current constraints based on prompt signatures. After a brief introduction on the main mechanisms leading to long-lived particles in supersymmetric theories, I will review the experimental techniques employed in these searches using the ATLAS detector. I will then present an overview of the data analysis results, with a particular focus on the most recent ones.
Mar 31, 2016

Andrea Gabrielli, Michele Papucci, Zoltan Ligeti (LBNL) "Highlights from Morion EW and QCD"

A brief overview of the main highlights discussed at Moriond 2016 is presented, with particular focus on LHC results, neutrino and flavour physics. One of the main topic of the conference is the first look at the results from LHC after its first run of 13 TeV proton-proton collisions ended last year. The experimental data confirm the Standard Model expectation concerning the vector boson, top and Higgs production rates. Searches for new resonances decaying into two photons in the ATLAS and CMS experiments have shown that the most significant deviation from the background prediction is observed at a diphoton invariant mass around 750 GeV. At the same time, the negative searches for signals of new phenomena decaying into other final state tightly constrained many new-physics scenarios, challenging previous theoretical wisdom and opening new perspectives in fundamental physics.

Apr 21, 2016

Chris Marshall (Univ. of Rochester) "Measurement of $K^{+}$ production by neutrinos at MINERvA"

Abstract: Charged kaon production by atmospheric neutrinos is a background in searches for the proton decay $p \rightarrow K^{+} \bar{\nu}$. Measurements of neutrino-induced $K^{+}$ production are important inputs for current and future proton decay searches at Super-K, Hyper-K and DUNE. The MINERvA neutrino-nucleus cross section experiment at Fermilab uses timing information to isolate a sample of $K^{+}$ decay-at-rest events. I will present the first differential cross section measurements for both charged- and neutral-current $K^{+}$ production by neutrinos, and discuss how these measurements can be used to constrain background predictions for proton decay. I will also show the first experimental evidence for coherent $K^{+}$ production by neutrinos.
May 05, 2016

Giorgio Gratta (Stanford) "Probing Gravity - and Other Forces - at Extreme Scales"

The inverse square law of gravity has been empirically tested to various degrees for distances between <0.1mm to 1AU.   Outside this range very little is known and, yet, physics beyond the standard model may actually introduce new long-range forces that would be observed as anomalies in the 1/R^2 behavior of gravity.   I will discuss some new experiments designed to substantially advance our knowledge in this area, at the two extremes of the distance range.  While the long distance regime would involve a deep space mission, a new breed of experiments focusing on the micron regime is already taking data, not only on gravitational interactions.
May 12, 2016

Bharat Ratra (Kansas State U.) "Dark Energy: Constant or Time Variable? (...and other open questions)""

Experiments and observations over the last two decades have persuaded cosmologists that (as yet undetected) dark energy is by far the main component of the energy budget of the universe. I review a few simple dark energy models and compare their predictions to observational data, to derive dark energy model-parameter constraints and to test consistency of different data sets. I conclude with a list of open cosmological questions.
May 19, 2016

Kathryn Zurek (LBNL/UCB) "New Ideas in Dark Matter Direct Detection"

May 31, 2016

Prof. V.M. Datar (Tata Institute of Fundamental Research, Mumbai, India) "The India based Neutrino Observatory project"

Abstract: The Indian effort to build an underground laboratory for rare processes is outlined. The flagship experiment, based on the 50 kiloton Iron Calorimeter, will measure atmospheric muon neutrinos and antineutrinos, separately, and will target the open problem of the neutrino mass hierarchy. Together with other experiments worldwide this will help address CP violation in the neutrino sector and this may help us understand why there is a preponderance of matter over anti-matter in the universe. The other experiments that are being planned are in the areas of: (1) neutrinoless double beta decay using a cryogenic bolometer of 124Sn (2) dark matter search and (3) a low energy accelerator for measuring nuclear cross sections of astrophysical interest.
Jun 02, 2016

David Stuart (UCSB) "Recent CMS SUSY Results"

Abstract: The LHC energy increase from 8 TeV to 13 TeV in 2015 provided a significant increase in sensitivity for new, high mass particles. This had a large impact on the sensitivity of searches for supersymmetric squarks and gluinos even though the 2015 data sample is relatively small.  I will survey the results of these searches, discuss some of the strategy of the CMS SUSY program, and describe the methodology for three specific searches.
Jun 23, 2016

Kate Scholberg (Duke U.) "What Stubs and Sparkles Will Tell Us About Exploding Stars"

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.
Jun 30, 2016

Alan Poon (LBL) "Searches for Majorana Neutrinos"

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.
Jul 21, 2016

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"

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.
Jul 28, 2016

Francois Bouchett (IAP) "Latest Cosmological News from the Planck Satellite Project"

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.

Aug 02, 2016

Evan Pease (UCB/Yale) "New results from the 332-live-day exposure of the LUX dark matter experiment"

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.
Aug 11, 2016

Leslie Rosenberg (Univ. of Washington) "The Axion Dark-Matter Experiment (ADMX)"

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.
Aug 18, 2016

Simone Pagan Griso (LBNL) "Highlights from ICHEP on the LHC Results"

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.
Aug 25, 2016

Neil Spooner (Univ. of Sheffield) " Galactic Signatures and Directional Detection of Particle Dark Matter - the CYGNUS Project and Probing below the Neutrino Floor”

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.
Sep 08, 2016

Brian Fujikawa (LBNL) "New Neutrinoless Double Beta Decay Results from KamLAND-Zen"

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.
Sep 15, 2016

Nick Kaiser (Hawaii) "The Physics of Gravitational Redshifts in Clusters of Galaxies"

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.
Oct 13, 2016

Hans Walter Rix (Max Planck) "Fuel Exploration in the Early Universe: The ALMA Spectroscopic Survey of the Hubble Ultra Deep Field"

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.
Oct 18, 2016

Greg Aldering, Bob Cahn, Alex Kim, and Saul Perlmutter (LBNL) "Type Ia Supernova Program at LBNL: Status and Plans"

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.
Oct 20, 2016

Marilena Loverde (Stony Brook Univ.) "Neutrinos, Quintessence and Structure Formation in the Universe"

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.
Oct 27, 2016

Bruce Schumm (UCSC) "Supersymmetry Searches at the LHC: Status and a Thought or Two about the Future"

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.
Nov 15, 2016

Erez Etzion (Tel-Aviv U.) "Higgs hunting episode II - Searches for Beyond the SM Higgs at the LHC"

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.
Nov 15, 2016

Emmanuel Schaan (Princeton) "Non-linearities in the large-scale structure: noise and signal"


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.

Nov 17, 2016

Robert Kirshner (Moore Foundation) "Doing WFIRST Science Now: Supernovae in the Infrared"

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.
Nov 22, 2016

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"

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.
Nov 29, 2016

Scott Kravitz (Stanford) "Identification of Single Barium Atoms for the nEXO Neutrinoless Double Beta Decay Experiment"

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.
Nov 30, 2016

SPECIAL SEMINAR: Wai Ling Kimmy Wu (Stanford) "Constraining Inflation with BICEP/Keck and SPT"

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 ?m 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.

Dec 01, 2016

Evan Pease (Yale) "Searching for WIMPs and More: Results from 3 Years of Underground Science with the LUX Experiment"

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.
Dec 06, 2016

Cristián H. Peña (Caltech) "Searches for New Physics at CMS and Precision Timing Detectors"

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.

Dec 08, 2016

Johanna Nagy (Case Western) "Probing Inflation with SPIDER, a Balloon-Borne CMB Polarimeter"


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.

Dec 13, 2016

ChangHoon Hahn (NYU) "Fundamental Physics with Galaxy Clustering"

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.

Dec 15, 2016

Nan Lu (U. Michigan - Ann Arbor) ""Higgs Boson Property Measurements with ATLAS at the LHC""


"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."

Dec 20, 2016

Karol Krizka (U. Chicago) "Dark Matter Mediators and Dijet Resonance Searches by the ATLAS Experiment"

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.