Bulletin of the American Physical Society
4th Joint Meeting of the APS Division of Nuclear Physics and the Physical Society of Japan
Volume 59, Number 10
Tuesday–Saturday, October 7–11, 2014; Waikoloa, Hawaii
Session KE: Mini-Symposium on Fundamental Symmetries (Neutrons and Gravity II) |
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Chair: Alexander Saunders, Los Alamos National Laboratory Room: King's 1 |
Saturday, October 11, 2014 9:00AM - 9:15AM |
KE.00001: Phenomenology of Neutron-Antineutron Oscillations Revisited Susan Gardner, Ehsan Jafari We revisit the phenomenology of neutron-antineutron ($n$-${\bar n}$) oscillations in the presence of external magnetic fields, highlighting the role of spin. We show, contrary to long-held belief, that the $n$-${\bar n}$ transition rate can be enhanced under special conditions, opening new pathways for its empirical study. [Preview Abstract] |
Saturday, October 11, 2014 9:15AM - 9:30AM |
KE.00002: Search for Neutron Anti-Neutron Oscillation using Cold Neutron Beams with Focusing Optics Hirohiko Shimizu The electric charge of neutrons is experimentally known as less than $10^{-21}$e and considered as exactly zero and the transition between neutron and anti-neutron is allowed in terms of the conservation of the electric charge but is considered forbidden according to the empirical conservation law of the baryon number. On the other hand, the existence of physical processes which violates the conservation of the baryon number is required in the Sakharov's conditions to explain the baryon assymmetry in the big-bang cosmology. The search for the neutron antineutron ($n\bar{n}$) oscillation offers information the baryon number violation with the $\Delta (B-L)=2$ complementary to the attempts with $\Delta (B-L)=0$. The sensitivity to the $n\bar{n}$ oscillation has been improved by searching for the instability of nuclei via $n\bar{n}$ oscillation in large-scale deep-underground experiments, which are now limited by the background. On the other hand, the improvement of accelerator-driven neutron sources and transport optics of slow neutron beams have introduced new possibility to improve the sensitivity to $n\bar{n}$ by orders of magnitude. In this paper, we discuss the experimental sensitivity to $n\bar{n}$ oscillation with accelerator-based neutron sources and neutron focusing optics. [Preview Abstract] |
Saturday, October 11, 2014 9:30AM - 9:45AM |
KE.00003: An update on the NPDGamma experiment David Blyth The NPDGamma experiment recently finished collecting roughly two-hundred fifty beam days of data measuring parity violation in the $np\rightarrow d\gamma$ reaction at the ORNL Spallation Neutron Source. The parity-violating directional asymmetry in the emission of prompt gammas from the capture of polarized cold neutrons on a liquid hydrogen target provides a measurement of the NN hadronic weak interaction that is unambiguously related to benchmark DDH model parameters (primarily $h_\pi^1$) and PV EFT couplings. An overview of the experiment and data selection/reduction challenges will be presented along with an initial low-statistics result. Projected uncertainties in the final result will be discussed taking into account the entirety of beam time at the FNPB dedicated to both hydrogen and background capture measurements. [Preview Abstract] |
Saturday, October 11, 2014 9:45AM - 10:00AM |
KE.00004: Neutron Spin Rotation Measurements by the NSR Collaboration Bret Crawford To constrain weak coupling constants between nucleons and place limits on the existence of possible long-range forces, the Neutron Spin Rotation (NSR) apparatus measures rotations of transversely-polarized neutrons passing through $\sim0.5$~m of target material [1,2]. A previous measurement on the NG6 beamline at the NCNR placed stringent limits on the size of parity-violating rotations of neutrons in liquid helium, $d\phi/dz = \left[ +1.7 \pm 9.1 (stat.)\pm1.4(sys.)\right] \times 10^{-7}$~rad/m [1]. A newly designed apparatus will accept the increased phase-space of the new high-flux NGC beam at NCNR to improve this statistically-limited measurement by about an order of magnitude. An experiment using the same apparatus with a room-temperature target is being proposed at LANSCE to place limits on parity-conserving rotations from possible fifth-force interactions to complement previous studies [3,4]. An overview of the experimental method, plans for upcoming measurements, and the status of upgrades will be presented.\\[4pt] [1] W. M. Snow et al., PRC {\bf 83}, 022501(R) (2011) \newline [2] H. Yan, W. M. Snow, PRL {\bf 110}, 082003 (2013)\newline [3] E. G. Adelberger, T.A. Wagner, PRD {\bf 88}, 031101(R) (2013)\newline [4] F. M. Piegsa, G. Pignol, PRL {\bf 108}, 181801 (2012) [Preview Abstract] |
Saturday, October 11, 2014 10:00AM - 10:15AM |
KE.00005: The n3He Experiment: Current Status Mark McCrea The n3He experiment aims to make a high precision measurement of the hadronic weak interaction in the reaction $\vec{n}+^3\!He \rightarrow p + T$ by measuring the parity violating asymmetry in the direction of proton emission relative to the neutron polarization direction. As the weak interaction is the only interaction to violate parity this allows us to extract the much smaller weak interaction effects from the larger strong interaction effects. The range of the asymmetry is estimated to be $(-9.5\rightarrow 2.5)\times 10^{-8}$. The goal is to measure this asymmetry with an accuracy of $2\times 10^{-8}$ to provide a benchmark for modern effective field theory calculations. n3He will run at the SNS Fundamental Neutron Physics Beamline. The combined target and detector is a multiwire $^3$He ionization chamber. A super mirror polarizer will be used to polarize the incoming cold neutron beam, and a spin flipper will reverse the spin in a sequence to control for systematic effects. [Preview Abstract] |
Saturday, October 11, 2014 10:15AM - 10:30AM |
KE.00006: Short-Range Gravity Experiment Newton-IVh at millimeter scale Tomomi Sakuta, Mirei Hatori, Reiko Kishi, Haruna Murakami, Kazufumi Ninomiya, Hironori Nishio, Shuntaro Saiba, Jiro Murata A large extra dimensional model predicts deviations from the Newtonian gravity at short distances below millimeters. Present NEWTON project at Rikkyo University aims an experimental test to Newton's inverse-square law at the millimeter scale. In order to examine the gravitational force at short range scale around millimeter, we have developed a new apparatus NEWTON-IVh using a torsion pendulum with a pico-precision displacement sensor using digital image analysis system, which was originally developed for a high energy collider experiment at RHIC. We determine the~~~gravitational force by measuring the twisting angle of the torsion pendulum when the gravitational sources are moved around the torsion pendulum.~~In this presentation, the development status and the results of the NEWTON-IVh experiment will be reported. [Preview Abstract] |
Saturday, October 11, 2014 10:30AM - 10:45AM |
KE.00007: Development of a next generation short range gravity experiment NEWTON-V, using digital microscope Shuntaro Saiba, Hiroaki Ando, Mirei Hatori, Shoki Inaba, Kazufumi Ninomiya, Tomomi Sakuta, Natsumi Shinozaki, Jiro Murata According to a large extra dimensional model, a deviation from Newton's inverse square law is expected at sub-millimeter range. Current NEWTON-IVh project aims to test the inverse-square law at millimeter scale, using a torsion pendulum. In order to examine the gravitational force at around micrometer distances, we are developing the new apparatus NEWTON-V, using a digital microscope. This experiment is going to measure gravity between two wires of around 10 to 100 micrometer, which are separated by distances in the range of 100 micrometer. One wire is used as a cantilever for the force sensing, which motion is measured by a pico-precision displacement sensor. This method was originally developed for the micron precision optical alignment system (OASys) for the PHENIX muon tracking chambers at RHIC, using digital image analysis technique. In this presentation, development status and preliminary results will be reported. [Preview Abstract] |
Saturday, October 11, 2014 10:45AM - 11:00AM |
KE.00008: ABSTRACT WITHDRAWN |
Saturday, October 11, 2014 11:00AM - 11:15AM |
KE.00009: Experimental studies of gravity with slow neutrons Masaaki Kitaguchi, Go Ichikawa, Katsuya Hirota, Hirohiko Shimizu, Naoyuki Sumi, Satoru Matsumoto, Tamaki Yoshioka, Tatsushi Shima, Kenji Mishima, Takashi Ino, Yoshichika Seki Neutron is a chargeless massive particle with the lifetime in the macroscopic range, which is suitable for precision measurement of the small influence of new physics including gravity. We have started the experimental studies of the gravity with slow neutrons in order to search non-Newtonian effect at the short range which is lead by the existence of extra-dimension of the space. Combination of the pulsed neutrons provided by J-PARC and the advanced optical devices enables us to perform new types of high precision measurements. Neutron scattering with noble gas target enables us to measure the interaction at the range of the order of 1 nm. The apparatus was installed into beamline NOP and commissioning has been started. Neutron interferometer has the advantage to measure the gravitational potential precisely. We are developing the large-scale interferometer using long-wavelength neutrons, which is realized by using multilayer mirrors. Ultra-cold neutrons in a small cavity can be bound to the discrete energy eigenstates by Earth's gravitational field. We are discussing the direct measurement of the spatial localization of the neutrons with high resolution detectors, for example, CCD and nuclear emulation. [Preview Abstract] |
Saturday, October 11, 2014 11:15AM - 11:30AM |
KE.00010: Neutron lifetime measurement with pulsed beam at J-PARC:Incident Beam Flux Risa Sakakibara, Hirohiko M. Shimizu, Masaaki Kitaguchi, Katsuya Hirota, Tomoaki Sugino, Satoru Yamashita, Ryo Katayama, Takahito Yamada, Nao Higashi, Harumichi Yokoyama, Hirochika Sumino, Tamaki Yoshioka, Hidetoshi Otono, Genki Tanaka, Naoyuki Sumi, Yoshihisa Iwashita, Ryunosuke Kitahara, Hideyuki Oide, Tatsushi Shima, Takashi Ino, Kenji Mishima, Kaoru Taketani, Yoshichika Seki The neutron lifetime is one of the important parameters in the estimation of the abundance of the light elements in the early universe through the Big Bang Nucleosynthesis (BBN). The accuracy of 0.1{\%} is desired in the neutron lifetime to quantitatively discuss the BBN in combination with the observation of the anisotropy of the cosmic microwave. We have started a lifetime measurement with pulsed neutrons at J-PARC/BL05. To measure the lifetime, we detect the decay electrons from the bunched neutrons and the incident neutron flux in the TPC at the same time. By diluting a small amount of $^{3}$He gas into the TPC, the incident flux is estimated by counting protons via $^{3}$He(n,p)$^{3}$H reactions. The accuracy of the selection of $^{3}$He(n,p)$^{3}$H events and the influence of the contamination of nitrogen gas are the major systematic errors. In this paper, the estimation of the systematic error in the incident flux is reported. [Preview Abstract] |
Saturday, October 11, 2014 11:30AM - 11:45AM |
KE.00011: Systematics of the UCN$\tau$ Experiment Robert Pattie Currently there is an approximately 4$\sigma$ discrepancy between measurements of the neutron lifetime performed using cold neutron beams and those performed with ultracold neutron (UCN) storage vessels. The UCN$\tau$ experiment uses a magneto-gravitational UCN trap to measure the neutron lifetime that eliminates systematics related to the loss of UCN on material trap walls. Careful accounting of all systematic effects in this effort is critical to resolving the discrepancy. Two approaches for determining the lifetime will be utilized to increase the robustness of the result: the lifetime will be determined by counting the surviving neutrons with a UCN counter, and also by UCN activation analysis of a vanadium foil. Both methods will have uncertainties arising from detector stability and efficiency, time dependent backgrounds, UCN depolarization, and normalization measurements. Other sources of systematic bias are also being investigated. The status of determining the systematic corrections and uncertainties of this experiment will be presented. [Preview Abstract] |
Saturday, October 11, 2014 11:45AM - 12:00PM |
KE.00012: Minimizing neutron population for one-sec lifetime measurement Zhehui Wang The number of ultracold neutrons (UCN) within a certain volume can be measured by counting the number of electrons or protons from the neutron beta-decay, or by direct counting of UCN [Salvat et al., Phys. Rev. C. {\bf 89} (2014) 052501]. In both cases, the error of measured neutron lifetime increases with the counting error, decreases with the waiting time inbetween counting, and is ultimately limited by the neutron population experimentally. A one-percent neutron lifetime measurement requires at least a few times 10$^4$ neutrons. A one-sec neutron lifetime measurement requires close to 10$^7$ neutrons initially. Both estimates are for a waiting period of about 1000 sec and a total neutron counting efficiency of 50\%. We lay out experimental options for error reduction with an emphasis on optimizing UCN detection efficiency, and discuss the minimum number of neutrons required to achieve one-second neutron lifetime measurement. [Preview Abstract] |
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