55839524
An apparatus to control and monitor the para-D2 concentration in a solid deuterium, superthermal source of ultra-cold neutrons
Abstract Controlling and measuring the concentration of para-D 2 is an essential step toward realizing solid deuterium as an intense ultra-cold neutron source. To this end, we implemented an experimental technique to convert para- to ortho-deuterium molecules by flowing D 2 gas through a cryogenic cell filled with paramagnetic hydrous ferric oxide granules. This process efficiently reduced the para-D 2 concentration from 33.3% to 1.5%. Rotational Raman spectroscopy was applied to measure the residual para-D 2 contamination to better than 2 parts in 10 3 , and the hydrogen contamination to 1 part in 10 3 . We also contrast our optical technique to conventional thermal conductivity measurements of the para-D 2 concentration, reporting some of the relevant strengths and weaknesses of our implementation of each technique.
27442116
Cold neutron energy dependent production of ultracold neutrons in solid deuterium.
A measurement of the production of ultracold neutrons from velocity-selected cold neutrons on gaseous and solid deuterium targets is reported. The expected energy dependence for two-particle collisions with well defined neutron and Maxwell-Boltzmann distributed molecular velocities is found for the gas target. The solid target data agree in shape with the phonon density-of-states curve and provide strong evidence for the phonon model including multiphonon excitations.
119507247
Storage of Ultracold Neutrons in the Magneto-Gravitational Trap of the UCN Experiment
The UCN experiment is designed to measure the lifetime n of the free neutron by trapping ultracold neutrons (UCN) in a magneto-gravitational trap. An asymmetric bowl-shaped NdFeB magnet Halbach array confines low-field-seeking UCN within the apparatus, and a set of electromagnetic coils in a toroidal geometry provides a background holding field to eliminate depolarization-induced UCN loss caused by magnetic field nodes. We present a measurement of the storage time store of the trap by storing UCN for various times and counting the survivors. The data are consistent with a single exponential decay, and we find store = 860 19 s, within 1 of current global averages for n. The storage time with the holding field deactivated is found to be store = 470 160 s; this decreased storage time is due to the loss of UCN, which undergo Majorana spin flips while being stored. We discuss plans to increase the statistical sensitivity of the measurement and investigate potential systematic effects.
5816062
Temperature-dependent neutron scattering cross-sections for polyethylene
Abstract This note presents neutron scattering cross-sections for polyethylene at 296, 77 and 4 K derived from a new scattering kernel for neutron scattering off of hydrogen in polyethylene. The kernel was developed in ENDF-6 format as a set of S ( α , β ) tables using the LEAPR module of the NJOY94 code package. The polyethylene density of states (from 0 to sub eV) adopted to derive the new kernel is presented. We compare our calculated room temperature total scattering cross-sections and double differential cross-sections at 232 meV at various angles with the available experimental data (at room temperature), and then extrapolate the calculations to lower temperatures (77 and 4 K). The new temperature-dependent scattering kernel gives a good quantitative fit to the available room temperature data and has a temperature dependence that is qualitatively consistent with thermodynamics.
118837551
New experimental limit on the electric dipole moment of the electron in a paramagnetic insulator
We report results of an experimental search for the intrinsic Electric Dipole Moment (EDM) of the electron using a solid-state technique. The experiment employs a paramagnetic, insulating gadolinium gallium garnet (GGG) that has a large magnetic response at low temperatures. The presence of the eEDM would lead to a small but non-zero magnetization as the GGG sample is subject to a strong electric field. We search for the resulting Stark-induced magnetization with a sensitive magnetometer. Recent progress on the suppression of several sources of background allows the experiment to run free of spurious signals at the level of the statistical uncertainties. We report our first limit on the eEDM of ( 5.57 ± 7.98 ± 0.12)×10 25 e·cm with 5 days of data averaging. The search for the electric dipole moment (EDM) of elementary particles is motivated to test the discrete symmetries assumed in the Standard Model (SM) of particle physics. An account of the different transformation properties of the EDM (a polar vector) and the spin (a pseudo-vector), the fundamental physical laws governing particles must violate both time-reversal (T) and parity-inversion (P) symmetries for a fermion to acquire an EDM [1]. While the phenomena of P violation is firmly established in numerous experiments, T violation has only been observed directly in the neutral kaon system [2], with more searches in the B system underway [3]. Measurements of EDMs of elementary particles use different experimental techniques, often on low energy systems at Q ≃ 0, to probe the physics of T violation (with no flavor-changing) at energy scales higher than tens of TeV, and could provide information complementary to that from high-energy collider experiments on the nature of symmetry breaking. The physics of T violation is often linked, via the CPT theorem, to the violation of the combined Charge conjugate (C) and P symmetry. The only confirmed source of CP violation in the SM is the complex phase of the CKM matrix (that describes the quark mixing in charged-current weak interactions). With it, the electron EDM (eEDM) manifests through high-order loop couplings that involve flavor-changing quark interactions with the exchange of W ± weak bosons. The resulting size of eEDM predicted within the framework of SM is no larger than 10 −38 e·cm, which is well beyond the reach of current experimental techniques. The current experimental upper bound is established using thallium atomic beams with a sensitivity of 1.6×10 −27 e·cm [4]. New sources of CP violation introduced by theories beyond
121822416
Beta decay measurements with ultracold neutrons: a review of recent measurements and the research program at Los Alamos National Laboratory
We present a review of the motivation and results of recent experiments which utilize ultracold neutrons for measurements of neutron beta decay. Because these experiments hinge critically on the available ultracold neutron source technology, we also review the status of ultracold neutron source development, emphasizing the Los Alamos ultracold neutron facility and the ongoing beta decay research program sited there.
5164847
Cyclic family symmetry and lepton hierarchy in supersymmetry
A cyclic symmetry among the left-handed doublets of the three families is proposed. This symmetry can naturally result in a realistic hierarchical pattern of the fermion masses within the framework of supersymmetry with nonvanishing sneutrino vacuum expectation values.
118639447
Pure gauge glueballs at finite temperature
Pure gauge glueballs at finite temperature are investigated in a large temperature range from 0:3Tc to 1:9Tc on anisotropic lattices. Optimized glueball operators are used to obtain better signals. It is found in all 20 symmetry channels that the pole masses MG of glueballs remain almost constants when the temperature approaches the critical temperature Tc from below, and start to reduce gradually with the temperature going above Tc. The glueball correlators in 0 ++ , 0 i+ , and 2 ++ channels, are also analyzed based on the Breit-Wigner ansatz by assuming a thermal width Γ to the pole mass ω0. While ω0's are insensitive to T in the whole temperature range, Γ's exhibit distinct behavior below and above Tc: They are only few percents of ω0 when T Tc and reach values of roughly Γ » ω0=2 at T … 1:9Tc.
17829085
Heavy baryon masses in large Nc HQET
Abstract We argue that in the large N c HQET, the masses of the s-wave low-spin heavy baryons approximately equal to the heavy quark mass plus proton mass. To the subleading order, the heavy baryon mass 1 N c expansion not only has the same form, but also has the same coefficients as that of the light baryon. Based on this, a numerical analysis is made.
43722033
Topological susceptibility near T-c in SU(3) gauge theory
Abstract Topological charge susceptibility χ t for pure gauge SU(3) theory at finite temperature is studied using anisotropic lattices. The over-improved stout-link smoothing method is utilized to calculate the topological charge. Near the phase transition point we find a rapid declining behavior for χ t with values decreasing from ( 188 ( 1 )  MeV ) 4 to ( 67 ( 3 )  MeV ) 4 as the temperature increased from zero temperature to 1.9 T c which demonstrates the existence of topological excitations far above T c . The 4th order cumulant c 4 of topological charge, as well as the ratio c 4 / χ t is also investigated. Results of c 4 show step-like behavior near T c while the ratio at high temperature agrees with the value as predicted by the diluted instanton gas model.
121293716
Symmetry Breaking in Finite Volume
Spontaneous symmetry breaking is a cooperative phenomenon for systems with infinitely many degrees of freedom and it plays an essential role in quantum field theories. Lattice O(N) model is studied within the Hamiltonian approach using an adiabatic approximation. It is shown that the low-lying spectrum of the system in the broken phase can be understood by using the adiabatic, or Born-Oppenheimer approximation, which turns out to become an expansion in the inverse power of volume. In the infinite volume limit, the symmetry is broken while in the finite volume the slow rotation of the zero-momentum mode restores the symmetry and gives rise to the rotator spectrum, which has been observed in realistic Monte Carlo simulations.