Bulletin of the American Physical Society
15th Annual Meeting of the Northwest Section of the APS
Volume 59, Number 6
Thursday–Saturday, May 1–3, 2014; Seattle, Washington
Session C3: Particle Physics |
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Chair: Justin Albert, University of Victoria Room: Alder Commons 105 |
Friday, May 2, 2014 1:30PM - 2:00PM |
C3.00001: The Higgs Boson: Discovery and Properties Invited Speaker: Michel Vetterli The discovery of the Higgs boson by the ATLAS and CMS collaborations, announced in July 2012, is the culmination of a very long search for this elusive ``cornerstone of electroweak symmetry breaking,'' or in simpler terms ``what gives subatomic partciles mass?.'' The effort since then has been to characterize the new particle (mass, spin, couplings) and determine whether it is the only such boson. This talk will describe the updated experimental evidence for the Higgs boson, built up from several production mechanisms and decay channels. Recent results have shown that the new particle is indeed consistent with the Standard Model Higgs boson. The presentation will focus on data from the ATLAS experiment. [Preview Abstract] |
Friday, May 2, 2014 2:00PM - 2:12PM |
C3.00002: Two Higgs Doublets and CP Violation Seyda Ipek Electroweak Baryogenesis, a way to explain matter/anti-matter asymmetry, needs a first order electroweak phase transition as well as CP violation. The Standard Model can not accommodate these two properties. Adding a second Higgs field to the Standard Model is shown to give a first order phase transition. I consider CP violation in this extended Higgs sector. The amount of CP violation one can get from new physics is constrained by the electron electric dipole moment. Taking the electric dipole moments into account, CP violation of $\mathcal{O}$(0.01) is allowed in the two Higgs doublet model. This CP violation could explain the matter/anti-matter asymmetry in the Universe. [Preview Abstract] |
Friday, May 2, 2014 2:12PM - 2:24PM |
C3.00003: The New Muon g-2 Experiment: E989 Status and Progress Update Loreto Alonzi The Higgs Boson has been discovered at the LHC, locking in the final piece of the Standard Model. Now it is time to focus on the tensions around the edges of the model. Work in the neutrino and cosmic sectors indicate a need for new physics at higher energy scales. A key tool in that search is the precision measurement of Standard Model predictions. Measurement of the muon anomalous magnetic moment ($a_{\mu}$) has long proved to be a useful guide, due in part to the exceptional sensitivity of the measurement technique first developed at CERN and most recently implemented at BNL where the E821 experiment measured it to 540$\,$ppb. This measurement resulted in a discrepancy from the Standard Model at a level greater than 3$\sigma$. The New Muon g-2 experiment at Fermilab (E989) aims to improve this precision by a factor of 4, down to 140$\,$ppb. Coupled with ongoing improvements in the theoretical calculation the new result will yield vital clues. The collaboration is making great progress and we will discuss: the completion of moving the superconducting electromagnet from Brookhaven National Lab to Fermilab, on site construction at Fermilab, detector development focusing on PbF$_{2}$ calorimetry with SiPM readout, and precision magnetic field monitors based on NMR technology. [Preview Abstract] |
Friday, May 2, 2014 2:24PM - 2:36PM |
C3.00004: Calorimeter Development for the New Muon g-2 Experiment Aaron Fienberg In the new muon g-2 experiment, determination of the anomalous magnetic moment requires energy and timing measurements of decay electrons. The calorimeter being designed to make these measurements is an array of lead fluoride (PbF$_{2}$) crystals coupled to silicon photomultipliers (SiPMs). Cherenkov light produced in the crystals allows for excellent timing and energy resolutions while the SiPMs' insensitivity to magnetic fields makes them a great choice for the experiment. Development of this detector is ongoing and recent work includes cosmic ray tests to evaluate the effects of different crystal wrappings, operation of SiPMs in a 1.5 T magnetic field, and evaluation of a prototype crystal array with an electron beam provided by the Stanford Linear Accelerator. We will present results from these tests and outline how they show that this novel detector will meet or exceed our design specifications. [Preview Abstract] |
Friday, May 2, 2014 2:36PM - 2:48PM |
C3.00005: Progress on the stationary pNMR array of the new muon (g-2) experiment at FNAL Martin Fertl, Alejandro Garcia, Rachael Morris, Cole Helling, Ronaldo Ortez, Rachel Osofsky, Erik Shaw, Matthias Smith, Erik Swanson One of the most stringent low-energy tests of the Standard Model (SM) of Particle Physics is the measurement of the muon's anomalous magnetic moment, called $(g-2)/2$. The BNL E821 collaboration has measured $(g-2)/2$ to a precision of 0.54 ppm. This result deviates by more than three standard deviations from the SM prediction. Thus the FNAL E969 collaboration has set out to measure $(g-2)/2$ to a precision of 0.14 ppm. The applied measurement technique relies on the accurate determination of the muon's Larmor frequency in a highly homogeneous magnetic field (0.17 ppm in BNL E821, 0.07 ppm in FNAL E969) of an electric and magnetic storage ring. The spatial magnetic field distribution along the storage ring is determined by pulling a trolley with pulsed proton nuclear magnetic resonance (pNMR) probes through its vacuum chamber. Since this cannot be performed during the muon measurements the magnetic field is interpolated in time between the trolley measurements using a fixed array of about 400 pulsed pNMR probes distributed around the storage ring. We will present the efforts made at the Center for Nuclear Physics and Astrophysics at the University of Washington to prepare and test the stationary pNMR probes array. Here we will present the status of the system. [Preview Abstract] |
Friday, May 2, 2014 2:48PM - 3:00PM |
C3.00006: Temperature dependence of the signal of the NMR probes for the muon (g-2) experiment Rachael Morris, Martin Fertl, Alejandro Garcia, Cole Helling, Ronaldo Ortez, Rachel Osofsky, Erik Shaw, Matthias Smith, Erik Swanson The latest investigation of the anomalous magnetic moment of the muon requires accurate and precise measurement of the magnetic field in the storage ring. The field is mapped using a series of pulsed proton NMR probes and knowing the response of the probes under different conditions is key to attaining the precision necessary for the experiment to take into account all possible systematic effects. While the temperature correction for the diamagnetic shielding of water in proton NMR is known experimentally and taken into account in previous incarnations of this experiment, the future probes will use petroleum jelly and the temperature dependence of the response of these probes is not well documented. We have been using a repurposed analyzing magnet used by the (g-2) group at the University of Washington for this investigation. Here I will discuss the methods, challenges and results we have obtained. [Preview Abstract] |
Friday, May 2, 2014 3:00PM - 3:15PM |
C3.00007: Break |
Friday, May 2, 2014 3:15PM - 3:45PM |
C3.00008: Messages for High Energy Physics from Astrophysics and Cosmology Invited Speaker: Ann Nelson I review some recently popular models of dark matter and baryogenesis and how the recent BICEP2 results, if confirmed, constrain the possibilities. [Preview Abstract] |
Friday, May 2, 2014 3:45PM - 3:57PM |
C3.00009: The MAJORANA Demonstrator status and prospects Clara Cuesta The MAJORANA Collaboration is constructing the MAJORANA Demonstrator, an ultra-low background, 40-kg modular high purity Ge detector array to search for neutrinoless double beta decay in Ge-76. In view of the next generation of tonne-scale Ge-based neutrinoless double-beta decay searches that will probe the neutrino mass scale in the inverted-hierarchy region, a major goal of the Demonstrator is to demonstrate a path forward to achieving a background rate at or below 1 count/tonne/year in the 4 keV region of interest around the Q-value at 2039 keV. The P-Type Point Contact design of the Demonstrator's germanium detectors allow for significant reduction of background through pulse shape analysis. An introduction to the MAJORANA Demonstrator technical design will be given, progress of the detector's construction at the Sanford Underground Research Facility at Homestake will be highlighted, and the sensitivity of the neutrinoless double beta decay search will be discussed. [Preview Abstract] |
Friday, May 2, 2014 3:57PM - 4:09PM |
C3.00010: Axion and Dark Matter Searches with the MAJORANA Demonstrator Julieta Gruszko The MAJORANA Demonstrator is an array of natural and enriched high purity germanium detectors that will search for the neutrinoless double-beta decay of germanium-76. The Demonstrator's projected low background, low threshold, and multi-site rejection capabilities will enable searches for other Beyond-the-Standard Model physics, including solar axions and light WIMP dark matter. The mechanisms for detection of these particles will be discussed. Simulations and data from research and development efforts will be used to predict the Demonstrator's performance in both axion and WIMP detection. [Preview Abstract] |
Friday, May 2, 2014 4:09PM - 4:21PM |
C3.00011: Holographic entanglement entropy vs backreaction Christoph Uhlemann, Han-Chih Chang, Andreas Karch The degree of entanglement among two systems can be quantified by the entanglement entropy, which plays a role in many areas of physics. Its calculation in QFT, however, is challenging. If available, a holographic description in terms of AdS/CFT simplifies this considerably, and thus provides the tool of choice. Many interesting AdS/CFT dualities are realized as small deformations of simpler cases, with the addition of probe branes to describe CFTs with flavor as a prominent example. We discuss new tools to efficiently compute the entanglement entropy in that setting and apply them to the D3/D7 system. [Preview Abstract] |
Friday, May 2, 2014 4:21PM - 4:33PM |
C3.00012: False Vacuum Decay in Deformed Gauge Theory Evan Thomas I present a calculation of the decay from a metastable vacuum state to the true ground state in a ``deformed'' QCD model. The deformed model coincides with undeformed Yang-Mills at strong coupling, but can be brought to weak coupling smoothly while preserving linear confinement, nontrivial vacuum structure, the proper $\theta$-dependence, and many other important aspects of true QCD. I show the presence of higher energy metastable vacuum states in this model, and discuss a euclidean bounce solution which gives a tunneling rate from one of these false vacuua to the true vacuum state. The calculation has been carried out in the semiclassical approximation and I present the numerical results, making comparisons with some old predictions for SU(N) gauge theories. [Preview Abstract] |
Friday, May 2, 2014 4:33PM - 4:45PM |
C3.00013: Ground State Masses of Charmonium Hybrids from QCD Sum-Rules Derek Harnett, Tom Steele, Jason Ho, Brendan Bulthuis, Timothy Richards, Ryan Berg, Robin Kleiv, Wei Chen, Shi-Lin Zhu Over the past decade or so, a number of new, charmonium-like resonances have been observed. However, few of these particles, collectively dubbed the XYZ resonances, can be neatly accommodated by a conventional charmonium meson interpretation as there are major discrepancies between theory and experiment with regards to masses, resonance widths, decay modes, and branching ratios. Quite naturally, this has fuelled a great deal of speculation that at least some of the newly discovered particles lie outside of the constituent quark model. Hybrids, hadrons with explicit quark and gluon degrees of freedom, represent one such possibility. In an effort to identify hybrid content within the XYZ resonances, we have performed a comprehensive QCD sum-rules analysis of ground state charmonium hybrid masses for a wide variety of quantum numbers. We present our findings and comment on the phenomenological implications. [Preview Abstract] |
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