Bulletin of the American Physical Society
2015 Fall Meeting of the APS Division of Nuclear Physics
Volume 60, Number 13
Wednesday–Saturday, October 28–31, 2015; Santa Fe, New Mexico
Session NJ: Electroweak II |
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Chair: Steven Clayton, Los Alamos National Laboratory Room: Coronado |
Saturday, October 31, 2015 8:30AM - 8:42AM |
NJ.00001: Connecting Fermion Masses and Mixings to BSM Physics -- Quarks Terrence Goldman, Gerard J. Stephenson, Jr. The ``democratic'' mass matrix with BSM physics assumptions has been studied without success. We invert the process and use the ``democratic'' mass matrix plus a parametrization of all possible BSM corrections to analyze the implications of the observed masses and CKM weak interaction current mixing for the BSM parameter values for the up-quarks and down-quarks. We observe that the small mixing of the so-called ``third generation'' is directly related to the large mass gap from the two lighter generations. Conversely, the relatively large value of the Cabibbo angle arises because the mass matrices in the light sub-sector (block diagonalized from the full three channel problem) are neither diagonal nor degenerate and differ significantly between the up and down cases. [Preview Abstract] |
Saturday, October 31, 2015 8:42AM - 8:54AM |
NJ.00002: Connecting Fermion Masses and Mixings to BSM Physics -- Leptons Gerard J. Stephenson, Jr., Terrence Goldman The universality of the Weak Interaction suggests that the structure of the Dirac mass matrix for neutrinos should be the same as that for the charged fermions. Thus, it must be true that there are at least three Majorana fermions, not necessarily mass eigenstates, which are sterile under the weak and electromagnetic interactions, and that three of these couple to the Higgs. We show that specific models of the sterile Majorana mass matrix exist for which the resulting effective active neutrino Majorana mass matrix is nearly diagonal in the current basis, with small but finite masses. Combined with the structure of the mass matrix for the charged leptons, this leads to a PMNS matrix for the lepton mixing that is nearly, but not exactly, tri-bi-maximal. [Preview Abstract] |
Saturday, October 31, 2015 8:54AM - 9:06AM |
NJ.00003: Analysis of the Kinematics in the Qweak Experiment Valerie Gray The Qweak experiment at Jefferson Lab aims to determine the weak charge of the proton to a high precision by parity-violating elastic electron scattering on protons in a liquid hydrogen target. After two years of data-taking, the experiment is in its analysis phase and the first results from the experiment's commissioning period have been published. The weak charge of the proton is directly related to the measured asymmetry, which is proportional to the squared four-momentum transfer $Q^2$ of the scattered electron. The uncertainty in $Q^2$ contributes directly to the precision of the measurement of the weak charge. Using two independent sets of drift chambers we can reconstruct the electron trajectory and its momentum. Horizontal drift chambers are located just after the target while vertical drift chambers are located after a magnetic field just before the final Cerenkov detectors. With a Geant4 Monte Carlo simulation we deduce the scattering vertex kinematics from the observed scattered energy and momentum. I will present the work on determining the $Q^2$ of the Qweak experiment from data and using the Geant4 simulation. I will discuss the sources that contribute to the uncertainty in the momentum transfer, and our progress towards a precision of 0.5\% on $Q^2$. [Preview Abstract] |
Saturday, October 31, 2015 9:06AM - 9:18AM |
NJ.00004: MOLLER/PREX Detector Development Dustin McNulty The high luminosity requirements of parity violating asymmetry measurements, such as those proposed by the Jefferson lab experiments MOLLER and PREX, create several challenges for detector design. Our current design focus is on thin quartz Cherenkov detectors with and without air light guides. These designs are radiation hard and give a consistent/robust response for each electron independent of energy. The quartz thickness, its distance from the pmt, the orientation between quartz and beam, and light guide geometry are some of the key design considerations. Several new thin quartz integrating detector prototypes have been constructed and recently tested at MAMI with the help of the P2 collaboration. These prototypes consisted of M\o ller and super-elastic rings for the MOLLER experiment, the new PREX II detector, and re-designed Jefferson Lab Hall A Luminosity monitor. This talk will introduce the new designs, give results from the recent beam studies, and give plans for future work. [Preview Abstract] |
Saturday, October 31, 2015 9:18AM - 9:30AM |
NJ.00005: PVDIS with the proposed SoLID spectrometer at Jefferson Lab Paul Souder The SoLID spectrometer is a new facility proposed for the JLab 11 GeV upgrade that combines the ability to obtain data with both high luminosity and large acceptance. One application is to measure parity-violation in deep inelastic scattering, covering a large range of $Q^2$ and Bjorken $x$ with high statistics. The experiment will search for new physics that involves vector coupling to the electron and axial vector coupling to the quarks. In addition, the results will probe the possibility that charge symmetry is violated at the quark level and also search for higher twist effects due to quark-quark correlations. The SoLID spectrometer is based on the CLEO solenoid which is being shipped from Cornell, instrumented with GEM tracking detectors, gas Ceremkov detectors, and a Shashlyk electron calorimeter. [Preview Abstract] |
Saturday, October 31, 2015 9:30AM - 9:42AM |
NJ.00006: Progress toward a new measurement of the neutron lifetime Kyle Grammer Free neutron decay is the simplest nuclear beta decay. A precise value for the neutron lifetime is valuable for standard model consistency tests and Big Bang Nucleosynthesis models. There is a disagreement between the measured neutron lifetime from cold neutron beam experiments and ultracold neutron storage experiments. A new measurement of the neutron lifetime using the beam method is planned at the National Institute of Standards and Technology Center for Neutron Research. Experimental improvements should result in a 1s uncertainty measurement of the neutron lifetime. The technical improvements, recent apparatus tests, and the path towards the new measurement will be discussed. This work is supported by DOE Office of Science, NIST, and NSF. [Preview Abstract] |
Saturday, October 31, 2015 9:42AM - 9:54AM |
NJ.00007: Absolute Neutron Fluence Measurements at the NIST Center for Neutron Research A. Yue, M. Dewey, D. Gilliam, J. Nico, E. Anderson, M. Snow, G. Greene, A. Laptev Precise, absolute fluence measurements of cold and thermal neutron beams are of primary importance to beam-type determinations of the neutron lifetime, measurements of standard neutron cross sections, and the development of standards for neutron dosimetry. At the National Institute of Standards and Technology (NIST), a totally absorbing neutron detector based on absolute counting of the $^{10}$B(n,$\alpha_{1}$)$^{7}$Li reaction 478 keV gamma ray has been used to perform fluence measurements with a precision of 0.06\,\%. This detector has been used to improve the neutron fluence determination in the 2000 NIST beam neutron lifetime by a factor of five, significantly reducing the uncertainty in the lifetime result. Ongoing and possible future uses of the Alpha-Gamma device include 1) Calibration of the neutron fluence monitors that will be used in the upcoming NIST beam neutron lifetime measurement BL2; 2) The first direct, absolute measurement of the $^{6}$Li(n,t)$^{4}$He neutron cross section at sub-thermal neutron energy; 3) Measurements of the $^{10}$B(n,$\gamma$)$^{11}$B and $^{235}$U(n,f) neutron cross sections; 4) A re-calibration of the national neutron standard NBS-1. The apparatus, measurement technique, and applications will be discussed. [Preview Abstract] |
Saturday, October 31, 2015 9:54AM - 10:06AM |
NJ.00008: Analysis of the Neutron Lifetime Data from the UCN$\tau$ Experiment Evan Adamek The UCN$\tau$ experiment seeks to precisely measure the neutron lifetime by storing ultracold neutrons in a magneto-gravitational trap. During the 2014-2015 run cycle at the Ultracold Neutron Facility at the Los Alamos Neutron Science Center, the experiment collected data to investigate systematic and statistical uncertainties. Preliminary analysis of this data set has allowed estimation of the eventual statistical reach of our current experimental configuration. Additionally, analysis of the effect of changing detector backgrounds has resulted in an improved understanding of their effect on measured trap lifetimes. Finally, analysis of this data set has allowed preliminary estimation of many of the leading systematic uncertainties in the experiment. [Preview Abstract] |
Saturday, October 31, 2015 10:06AM - 10:18AM |
NJ.00009: High sensitivity test of the Pauli Exclusion Principle for electrons with X-ray spectroscopy (VIP2) Johann Marton The Pauli Exclusion Principle (PEP) is one of the most fundamental rules in physics and it has various important consequences ranging from atomic and subatomic systems to the stability of matter and stellar objects like neutron stars. Due to many observations This rule must be valid to an extremely high degree and consequently no violations were found so far. On the other hand a simple explanation of PEP is still missing. Many experimental investigations based on different assumptions were performed to search for a tiny PEP violation in various systems. The experiment VIP2 at the Gran Sasso underground laboratory (LNGS of INFN) is designed to test the PEP for electrons with high sensitivity by searching for forbidden X-ray transitions in copper atoms. This experiment aims to improve the PEP violation limit obtained with our preceding experiment VIP by orders of magnitude. The experimental method, comparison of the VIP result with different PEP searches and the present status of the VIP2 experiment will be presented. [Preview Abstract] |
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