Bulletin of the American Physical Society
14th Annual Meeting of the Northwest Section of the APS
Volume 57, Number 7
Thursday–Saturday, October 18–20, 2012; Vancouver, British Columbia, Canada
Session C3: Particle Physics I |
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Chair: Janis McKenna, University of British Columbia Room: SFU Harbour Centre 2270 Sauder Industries Policy Room |
Friday, October 19, 2012 1:30PM - 1:42PM |
C3.00001: Prototype of a Cluster-Counting Drift Chamber Jean-Fran\c{c}ois Caron In August 2012 a prototype drift chamber was tested at TRIUMF using a $\sim 200$ MeV/c beam of electrons, muons, and pions. The drift chamber is instrumented to allow the use of a cluster-counting technique, whereby the full waveform on the sense wire is recorded. The signal from each primary ionization can be resolved with suitable algorithms, allowing for better particle identification than traditional charge measurements which merely integrate the sense wire signal. Instrumenting a full-scale drift chamber for cluster counting would be expensive, and this study quantifies the particle identification aspect of the potential improvements obtained from such an expense. [Preview Abstract] |
Friday, October 19, 2012 1:42PM - 1:54PM |
C3.00002: SRF cavity and HOM damper tests at TRIUMF for ARIEL Philipp Kolb, Robert Laxdal, Vladimir Zvyagintsev The eLINAC for ARIEL\footnote{Advanced Rare Isotope Experiment Laboratory} consists of 5 superconducting nine cell cavities operating at 1.3 GHz, each cavity with a accelerating voltage of 10 MV. The design requires a quality factor of $1 \cdot 10^{10}$ or higher at the operating temperature of 2 K for 10 W dissipated power in the cavity walls. Latest SRF\footnote{Superconducting Radio Frequency} tests of a 1.3 GHz niobium single cell cavity will show that procedures at TRIUMF are capable of exceeding the RF requirements of ARIEL. Future upgrade plans for the eLINAC include a recirculating arc to either increase the energy of the 10 mA electron beam or drive an FEL\footnote{Free Electron Laser} in ERL\footnote{Energy Recovery LINAC} mode. BBU\footnote{Beam Break-Up} is a limitation in recirculating LINACs. Its strength depends on a number of parameters including the shunt impedance $R_{Sh}$ of HOM,\footnote{Higher Order Modes} especially dipole modes, of the SRF cavity. Using beam line absorbers made out of a low electric conductive material reduces the $Q_L$ of the cavity and therefore reduces the $R_{Sh}$. Qualification of such a material is essential and measurements of the electrical conductivity of a candidate material will be presented in addition to the cavity tests. [Preview Abstract] |
Friday, October 19, 2012 1:54PM - 2:06PM |
C3.00003: TRIUMF Ultra-cold Neutron Source Facility Yun Chang Shin An ultra-cold neutron (UCN) source is planned for installation at TRIUMF, Canada, aiming to produce the world's highest density of UCNs using down-scattering of cold neutrons in superfluid helium. This project is a collaboration of Japan and Canada funded by JSPS (KEK) and CFI (University of Winnipeg). The first experiment using this UCN source will be the measurement of the electric dipole moment of the neutron (nEDM). Development of the UCN source and the prototype nEDM experiment will be done at RCNP, Japan in 2013-14. After that, the UCN source and the EDM apparatus will be moved and installed at TRIUMF. Beam commissioning is scheduled for 2015 and neutron EDM experiment is scheduled to start in 2016 at TRIUMF. The goal is to improve the current upper limit of nEDM of $d_{n} < 2.9\times 10^{-26}$e-cm by two order of magnitude at TRIUMF. An overview of the TRIUMF UCN facility including design of a new beam line, development of a spallation target, and re-configuring of the shielding arrangement will be presented in this talk. [Preview Abstract] |
Friday, October 19, 2012 2:06PM - 2:18PM |
C3.00004: Developments related to ultracold neutron detection and magnetic field stability for the nEDM experiment at TRIUMF Edgard Pierre A new experiment to search for the neutron electric dipole moment (nEDM) is currently under development at RCNP, Japan and TRIUMF, Canada. Lowering the upper limit on the nEDM, currently d$_{n}<$ 2.9$\cdot$10$^{-26}\ e\ $cm, by a two orders of magnitude would test theoretical models beyond the Standard Model. The experiment will use ultra-cold neutrons (UCN) produced from down-scattering of cold neutrons in superfluid helium. The very high UCN density expected in the storage chamber ( $\sim$ 5$\cdot$10$^{3}$ UCN/cc) requires the development of a new UCN detector efficient at the MHz level. Another challenge of the experiment is the control of the magnetic field inside the storage chamber. In order to reach the expected sensitivity, the magnetic field must be stable at the pT level, and any magnetic field gradients must be less than 1 nT/m. An overview of the progress and future developments in these two fields will be given in this talk. [Preview Abstract] |
Friday, October 19, 2012 2:18PM - 2:30PM |
C3.00005: A New Event Reconstruction Algorithm for Super-Kamiokande Water Cherenkov Detector Shimpei Tobayama Super-Kamiokande is the world's largest water Cherenkov particle detector located underground in Kamioka-mine, Gifu, Japan. The detector has been used for proton decay search, and observation of atmospheric, solar and supernova neutrinos. It also serves as the far detector for T2K long baseline neutrino oscillation experiment. The detector consists of a cylindrical tank filled with 50kt of ultra-pure water, and an array of 11,000 photomultiplier tubes (PMT) installed on the tank's inner wall record the time and intensity of the Cherenkov light emitted by charged particles traveling in the water. Using the information from the PMTs, particle type, interaction vertex, direction and momentum can be reconstructed. A new reconstruction algorithm is being developed which performs a simultaneous maximum likelihood determination of such parameters. Through Monte Carlo studies, it was found that the new algorithm has a significantly better particle identification performance and vertex/momentum resolutions, compared to the existing reconstruction software. In this talk, an outline of the new algorithm, its performance and implications on physics analyses will be presented. [Preview Abstract] |
Friday, October 19, 2012 2:30PM - 2:42PM |
C3.00006: High Precision Measurement Of The Pion Branching Ratio Tristan Sullivan The pion branching ratio $ R = \frac{\Gamma\left(\pi \rightarrow e \nu \hspace{1 mm} + \hspace{1 mm} \pi \rightarrow e \nu \gamma \right)}{\Gamma\left(\pi \rightarrow \mu \nu \hspace{1 mm} + \hspace{1 mm} \pi \rightarrow \mu \nu \gamma \right)}$ can be calculated to a precision of better than one part in ten thousand using the Standard Model (SM). Averaging the most precise measurements of this quantity gives a value consistent with the SM prediction but whose error is more than ten times greater than the theoretical \ uncertainty. The PIENU experiment at TRIUMF aims to exceed the precision on the world average by more \ than a factor of five. The largest contribution to the overall error comes from the response function of the primary calorimeter to positrons produced by $ \pi \rightarrow e \nu $ decay. Measurements have been taken to characterize this effect, and have been compared in detail to Monte Carlo simulation. The agreement between data and simulation suggests the response function can be determined to the required precision. The analysis of the data and comparison with simluation will be presented. [Preview Abstract] |
Friday, October 19, 2012 2:42PM - 2:54PM |
C3.00007: Of Spheres and Matrices Philippe Sabella-Garnier, Ken Huai-Che Yeh, Joanna Karczmarek Gauge theory with a Higgs field on a sphere emerges from a Lagrangian with matrix degrees of freedom and no explicit spatial dependence. The sphere is noncommutative, leading to a deep connection between the fields and the underlying geometry. More specifically, we examine how the Higgs field corresponds to a deformation of the sphere in the radial direction. We show that in certain cases this effect persists even in the commutative limit. We also compare this approach with the construction of surfaces from matrix representations of D-branes. [Preview Abstract] |
Friday, October 19, 2012 2:54PM - 3:06PM |
C3.00008: ABSTRACT WITHDRAWN |
Friday, October 19, 2012 3:06PM - 3:26PM |
C3.00009: BREAK |
Friday, October 19, 2012 3:26PM - 3:38PM |
C3.00010: Experimental Demonstration of Fermion Spin Correlations Robert Close Bell's Theorem places limits on correlations between local measurements of particles whose properties are independent of measurement. In particular, Bell's Theorem limits the mean product of binary spin measurements at $45^\circ$ (or $135^\circ$) separation to be $|P| \le 0.5$. However, Bell's Theorem is not valid for spins sampled on a spherical distribution because the density of sampled states depends on the sampling location. We model spin-1/2 fermions as azimuthally symmetric spherical standing waves with one hemisphere of spin up and one hemisphere of spin down. We experimentally determine the spin correlation for $45^\circ$ separation by randomly placing two points with fixed separation on a ball marked with lines of latitude. The normalized product of spins is $+1$ if the two points are on the same side of the equator, and $-1$ if the points are on opposite sides of the equator. The expected correlation (mean product) is $P=1-45/90 = 0.5$. Correcting for the lack of azimuthal symmetry in the experimental ball increases the expected correlation in our model to approximately $P = \cos 45^\circ \approx 0.71$, inconsistent with Bell's Theorem but consistent with experimental measurements on entangled spin-1/2 fermions. [Preview Abstract] |
Friday, October 19, 2012 3:38PM - 3:50PM |
C3.00011: Nuclear recoil energy spectrum of finite-sized dark matter Anffany Chen Research has shown that direct dark matter detection experiments can distinguish between pointlike and finite-sized dark-matter candidates, both of which are of theoretical interests. In particular, there is an additional form factor in the typical cross section of finite-sized dark matter, causing the nuclear recoil energy spectrum of finite-sized dark matter to decrease more rapidly with the recoil energy than that of pointlike dark matter. Since the spectrum of finite-sized dark matter peaks below 1 keV, which is the common experimental threshold, and falls off rapidly at higher energies, detector with sub-keV threshold is necessary. The current goal of TEXONO-CDEX research program, on the studies of low energy neutrino and dark matter physics at Kuo-Sheng Reactor Neutrino Laboratory and China Jin-Ping Underground Laboratory, is to open the sub-keV detector window with germanium detectors. This work derives a model-independent, theoretical prediction of the nuclear recoil energy spectrum of finite-sized dark matter and is working toward using the predicted spectrum to analyze the experimental data of TEXONO-CDEX, in hope to substantiate or rule out dark matter candidates. [Preview Abstract] |
Friday, October 19, 2012 3:50PM - 4:02PM |
C3.00012: Dark Matter Antibaryons from a Supersymmetric Hidden Sector Nikita Blinov, David Morrissey, Kris Sigurdson, Sean Tulin The cosmological origin of dark matter and the baryon asymmetry of the universe can be explained through a unified mechanism called hylogenesis where baryon and antibaryon number are sequestered into a visible and a GeV-scale hidden sector. The universe remains baryon symmetric and the hidden antibaryons are the dark matter. We study the cosmology and phenomenology of this scenario in a supersymmetric theory in order to stabilize the electroweak and GeV hidden sector mass scales. This class of models contains a novel direct detection signature where a dark matter particle can scatter inelastically off a nucleon, destroying it and producing a meson and a dark matter antiparticle. This induced nucleon decay can be searched for in present and future nucleon decay experiments. [Preview Abstract] |
Friday, October 19, 2012 4:02PM - 4:14PM |
C3.00013: Reactor neutrino anomaly and sterile neutrinos revisited Annika Lennarz In this contribution we will present results from two separate experiments dealing with the neutrino response on 71Ga. Both experiments provide input to the calibration of the SAGE and GALLEX solar neutrino detectors and address a long-standing discrepancy between the measured and evaluated capture rates from the 51Cr and 37Ar neutrino calibration sources. The first is a 71Ga(3He,t)71Ge charge-exchange experiment performed at RCNP, Osaka, which allows to extract with high precision the Gamow-Teller transition strengths to the three lowest-lying states in 71Ge, i.e., the ground state (1/2-), the 175 (5/2-) and the 500 keV (3/2-) excited states. These are the states, which are populated via a charged-current reaction induced by neutrinos from reactor produced 51Cr and 37Ar sources. In the second part we present a new precision Q-value measurement for the 71Ga(nu,e-)71Ge reaction using the TITAN mass measurement facility at TRIUMF. From the results of the two experiments we now conclude that there are no further unknowns in the nuclear structure, which could remove the persistent discrepancy in the SAGE and GALLEX calibration measurement performed with neutrinos from 51Cr and 37Ar sources. [Preview Abstract] |
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