Bulletin of the American Physical Society
2005 2nd Joint Meeting of the Nuclear Physics Divisions of the APS and The Physical Society of Japan
Sunday–Thursday, September 18–22, 2005; Maui, Hawaii
Session JB: Mini-symposium on Low Energy Tests of the SM and Searches for New Physics II |
Hide Abstracts |
Sponsoring Units: DNP JPS Chair: Jun Imazato, KEK Room: Ritz-Carlton Hotel Salon 3 |
Thursday, September 22, 2005 9:00AM - 9:30AM |
JB.00001: Testing CPT using low energy antiprotons Invited Speaker: According to the CPT theorem, physics laws are unchanged under the simultaneous inversion of charge (C), parity (P) and time (T). Since many of candidate theories for unifying gravity and the standard model include effects that violate assumptions for the CPT theorem, such as curved spacetime, nonpointlike interactions and unitarity violation through decoherence, it is important to experimentally test CPT to the highest possible precision. Since the 1s-2s two-photon laser spectroscopy and the ground-state hyperfine splitting microwave spectroscopy of atomic hydrogen have already been carried out respectively to $10^{-14}$ and $10^{-12}$ relative precision, high-precision comparison of hydrogen and antihydrogen will be one of the most sensitive CPT tests. For the 1s-2s experiment, we need to make cold antihydrogen atoms in the ground state so that they can be trapped in a magnetic trap. For the hyperfine splitting measurement, a slow antihydrogen beam must be produced. At present, even though antihydrogen atoms can be routinely produced at CERN's antiproton decelerator (AD) at a rate of some 100 Hz, the produced anti-atoms are neither in the ground state nor cold enough to be useful for spectroscopy. Current status and future directions are discussed. I will also discuss the status of high-precision laser spectroscopy of antiprotonic helium atoms ($¥bar{p} - e^- -$He), which now offers the best baryonic CPT test. [Preview Abstract] |
Thursday, September 22, 2005 9:30AM - 9:45AM |
JB.00002: Way to CPT test with cold antihydrogen Ryo Funakoshi The CPT theorem and the Weak Equivalence Principle (WEP) are foundational principles on which the standard description of the fundamental interactions is based. The validity of such basic principles should be tested using the largest possible sample of physical systems. Cold neutral antimatter (low-energy antihydrogen atoms) could be a tool for testing the CPT symmetry with high precision. After several years of experimental efforts, the production of low energy antihydrogen through the combination of antiprotons and positrons is a well established experimental reality. An overview of the ATHENA experiment at CERN will be given and the main experimental results on antihydrogen formation will be reviewed. [Preview Abstract] |
Thursday, September 22, 2005 9:45AM - 10:00AM |
JB.00003: Experiments on Laser-Induced Radiative Formation of Antihydrogen Atoms. Lawrence Gene C. Posada, Ryo Funakoshi, Ryugo S. Hayano, Makoto C. Fujiwara, Yasunori Yamazaki Spectroscopy of antihydrogen and hydrogen atoms can provide a direct test for CPT invariance and the Weak Equivalence Principle, and perhaps also offer insights to searches for new physics. As a step towards that goal, we report on the ATHENA Collaboration's experiments on laser-induced radiative formation of antihydrogen. In this process, i.e. $e^++\bar {p}+\gamma \to \bar {H}+\gamma $ a positron and an antiproton are induced to form a bound state of antihydrogen by using a photon of a specific wavelength. Our main objective is to use a CW $^{13}$C$^{18}$O$_{2}$ laser to induce the formation of antihydrogen atoms with the principal quantum number n = 11. Control of the quantum states of antihydrogen will be necessary for future experiments. This experiment has been performed at the CERN Antiproton Decelerator facility. [Preview Abstract] |
Thursday, September 22, 2005 10:00AM - 10:15AM |
JB.00004: High precision spectroscopy of antiprotonic helium atoms N. Ono, D. Barna, A.J. Dax, J. Eades, K. Gomikawa, R.S. Hayano, M. Hori, T. Ishikawa, W. Pirkl, H.A. Torii, T. Yamazaki, B. Juhasz, E. Widmann, D. Horvath Antiprotonic helium is an exotic three body metastable system consisting of an antiproton, an electron and an alpha particle. We have measured the transition energies of the states of this atom with a laser spectroscopy method at the AD (Antiproton Decelerator) of CERN. By comparing the results of 2002 experiment with theoretical calculations, we set a limit of the possible differences between the antiproton and the proton charges and masses at 1$\times10^{-8}$. These are the best CPT limits for baryonic masses and charges. In 2004, we developed the laser to improve the experimental precision. We used a narrow-bandwidth ($\delta f/f<10^{-9}$) single-frequency CW laser. The frequencies of the laser were measured and stabilized by an optical frequency synthesizer with a relative accuracy of $10^{-10}$. The CW laser was amplified with dye, and we generated the laser pulses which had high energy and narrow bandwidth thorough enough to measure the transition energies more precise than the experiment in 2002. Using this laser system, we measured the transition frequencies of antiprotonic helium atoms to about a factor 10 better than the experiment in 2002. [Preview Abstract] |
Thursday, September 22, 2005 10:15AM - 10:30AM |
JB.00005: New limit on the T-violating transverse muon polarization in K$^{+}\to \pi ^{0}\mu ^{+}\nu $ (K$\mu $3) decays Suguru Shimizu A search for T-violating transverse polarization (Pt) in the K$\mu $3 decay was performed using kaon decays at rest. Pt is the polarization component normal to the decay plane, and a T-odd observable. A nonzero value would be evidence for violation of time reversal invariance, because spurious effects from final state interaction are known to be small. Moreover, due to negligible contribution from the standard model, Pt would provide important clue to new physics beyond the standard model. The experiment was performed at the KEK 12 GeV proton synchrotron. The decay products were emitted in all directions and detected by a 12-sector ion-core superconducting toroidal spectrometer and a $\pi ^{0}$ calorimeter with large directional acceptance. Pt was measured as the azimuthal muon polarization when $\pi ^{0}$ is tagged in the forward or the backward direction relative to the beam direction. The signature of nonzero Pt is an asymmetry between clockwise and counterclockwise Michel positrons. The final result using all data taken in 1996-2000 was obtained to be Pt=-0.0017$\pm $0.0023(stat)$\pm $0.0011(syst). The T-violation parameter was determined to be Im$\xi $=-0.053$\pm $0.0071(stat) $\pm $0.0036(syst) giving an upper bound $\vert $Im$\xi \vert <$0.016. [Preview Abstract] |
Thursday, September 22, 2005 10:30AM - 10:45AM |
JB.00006: The emiT Experiment: A Search for Time-reversal Invariance Violation in Neutron Beta Decay H.P. Mumm, M.S. Dewey, J.S. Nico, A.K. Thompson, A. Garcia, J.F. Wilkerson, T.E. Chupp, R.L. Cooper, C.A. Trull, F.E. Wietfeldt, S.J. Freedman, B.K. Fujikawa, G.L. Jones The emiT experiment tests time-reversal symmetry in the beta decay of polarized free neutrons by searching for the time reversal-odd, parity-even triple correlation between the neutron spin and momentum of both the electron and proton. The detection of this correlation above the small calculable effect due to final state interactions would be a direct indication of time reversal symmetry violation, independent of charge conjugation-parity. In the experiment, a beam of cold neutrons is polarized to better than 90\% using a supermirror polarizer. Decays are observed using an alternating array of electron and proton detection paddles. The highly symmetric octagonal geometry both reduces systematic effects and increases the detection efficiency relative to many previous experiments. The emiT collaboration has published a result [1] from its first run. A highly successful second run of the emiT experiment has recently been completed at the NIST Center for Neutron Research. The analysis of this greatly improved data set will be presented along with implications for time reversal violation. [1] Phys. Rev. C. 62, 055501, (2000). [Preview Abstract] |
Thursday, September 22, 2005 10:45AM - 11:00AM |
JB.00007: Performance test of the prototype detector for Dark Matter Search Akiko Yanagisawa, Tadafumi Kishimoto, Izumi Ogawa, Ryuta Hazama, Sei Yoshida, Saori Umehara Extensive observational evidence indicates that non-luminous, dark matter comprises a large fraction of the matter in the universe. Recent observation of cosmic microwave background suggests that dark matter consists predominantly of non-baryonic particles, and Weakly Interacting Massive Particles (WIMPs), neutralino dark matter are presently most favored. These WIMPs would interact elastically with nuclei, generating recoil energy of a few tens of keV, at a rate smaller than $\sim $1event/kg/day. We have developed a CaF$_{2}$ scintillation detector system (ELEGANT VI) to search for spin coupled dark matter by elastic scattering of $^{19}$F. Because of the low-energy and low-event-rate, to improve the sensitivity of the detector system, we must achieve more light collection and background reduction. So we have started the study of the new design of the detector system which consists of cubic CaF$_{2}$ (pure) crystal all sides covered by light guides. In this system, more light collection and less background level are expected for much larger photo-coverage and CaF$_{2}$ (pure) low radioactivity, respectively. As a first stage, we are developing the prototype detector and testing the photon collection efficiency of the light guide system for the optimization. The performance of the prototype detector will be reported. [Preview Abstract] |
Thursday, September 22, 2005 11:00AM - 11:15AM |
JB.00008: EDM Searches in Muons and Deuterons J.A. Miller The observation of a permanent electric dipole moment aligned along the spin of an elementary particle is a violation of both parity (P) and time reversal (T) invariances. So far, no such observation has been made. T violation implies, under the assumption of CPT invariance, that there would be a corresponding violation of CP invariance. Because the properties of CP invariance play important roles in the unraveling of the mysteries of the Standard Model (SM) and in understanding the baryon asymmetry of the universe, much experimental effort has occurred or is planned to search for EDMs in a variety of atoms and elementary particles. Here, high precision searches of the EDMs of the muon and the deuteron will be discussed. The muon sensitivity will be at the level of 10$^{-24}$-10$^{-26}$ e-cm, which is largely limited by available muon fluxes. Models outside the SM predict an EDM as large as a few times 10$^{-22}$ e-cm. The much larger available flux of deuterons can lead to a measurement at the 10$^{-29}$ e-cm level, which would make it the best EDM limit on any particle. The proposed experiments would employ the thus far relatively unexploited technique of storage rings, which enables the measurement of the EDM of free charged particles to high precision for the first time. All experimental approaches measure the interaction of the putative EDM with a strong electric field. The proposed approach completely circumvents the 'Schiff suppression' of the EDM signal when particles are embedded inside neutral atoms. [Preview Abstract] |
Thursday, September 22, 2005 11:15AM - 11:30AM |
JB.00009: Nuclear spin maser at low frequency and atomic EDM of $^{129}$Xe Akihiro Yoshimi, Koichiro Asahi, Makoto Uchida, Sachiko Oshima A search for electric dipole moment (EDM), which indicates a direct evidence for the violation of time reversal symmetry, is one of the important sites for studying the origin of CP violation. The standard model predicts the EDM value of 5-6 orders smaller than present experimental upper limits, while predictions of the non-standard models such as supersymmetry are not far from the upper limit. In order to perform the search for atomic EDM of $^{129}$Xe, we have developed nuclear spin maser with optically pumped $^{129}$Xe, which operates at a low magnetic field of mG by using sensitive optical detection of nuclear precession and feedback system of the transverse oscillating field which is synchronism with the spin precession. This low frequency nuclear spin maser which involves the artificial feedback system enables us to measure a continuous nuclear spin precession at a stabilized low magnetic field, and thus the determination frequency precision of spin precession can be dramatically improved. We have developed an atomic magnetometer with Rb and a stabilized current source for the magnetic field control to continuously operate the spin maser under highly stabilized magnetic field. We will report on performance of the new type of nuclear spin maser especially on the frequency stability, and feasibility for EDM search with the experimental sensitivity of 1-2 orders better than the present ones. [Preview Abstract] |
Thursday, September 22, 2005 11:30AM - 11:45AM |
JB.00010: Demonstration of Thousands of Successive Bragg Reflections from a Perfect Silicon Crystal and Its Application in the Search for the Neutron EDM Thomas Dombeck, Helmut Kaiser, Michael Huber, Dmitry Pushin, Daniel Hussey, David Jacobson, Robert Smither, Donald Koetke Using neutrons from the National Institute of Standards and Technology reactor we have measured the reflectivity from the (220) planes of Si using multiple Bragg reflections from a channel-cut perfect crystal to obtain R=0.999949 with a rms error of 0.000017. This is in good agreement with model calculations and indicates that at least 20,000 reflections are possible before there is significant loss of neutron intensity. We are currently setting up to measure the neutron magnetic dipole moment (MDM) interaction with Si using multiple reflections of polarized neutrons. This interaction results in a rotation of the neutron spin due to the torque on the moving MDM in the atomic electric field. The spin rotations from multiple reflections will be additive yielding a measurable signal. One result of this experiment will be a measure of the atomic electric field experienced by the neutrons which is needed for an Electric Dipole Moment (EDM) search using this technique. [Preview Abstract] |
Thursday, September 22, 2005 11:45AM - 12:00PM |
JB.00011: Search for a Neutron Electric Dipole Moment Paul Huffman The possible existence of a nonzero electric dipole moment (EDM) of the neutron is of great fundamental interest in itself and directly impacts our understanding of the nature of electro-weak and strong interactions. The experimental search for this moment has the potential to reveal new sources of T and CP violation and to challenge calculations that propose extensions to the Standard Model. The goal of the current experiment is to significantly improve the measurement sensitivity to the neutron EDM over what is reported in the literature. The experiment has the potential to either measure the magnitude of the neutron EDM or to lower the current experimental limit by two orders of magnitude. Achieving these objectives will have a major impact on our understanding of the physics of both weak and strong interactions. I will provide an overview of the experiment and report on recent progress. [Preview Abstract] |
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