How the minuscule can contribute to the big picture: the neutron electric dipole moment project at TRIUMF

A permanent electric dipole moment (EDM) of a fundamental particle violates both parity (P) and time (T) reversal symmetry and combined charge and parity (CP) reversal symmetry if the combined reversal of charge, parity \textit{and} time (CPT) is preserved. It is a very promising place to search for physics beyond the Standard Model. Ultracold neutrons (UCN) are the ideal tool to study the neutron electric dipole moment since they can be observed for hundreds of seconds. This article summarizes the current searches for the neutron EDM using UCN and introduces the project to measure the neutron electric dipole moment at TRIUMF using its unique accelerator driven spallation neutron and liquid helium UCN source. The aim is to reach a sensitivity for the neutron EDM of around $10^{-27} \,e \cdot$cm.Comment: 12 pages, 6 figures, MENU 2016 Conference, Kyoto, Japa

CP asymmetries in neutralino production in e+e- collisions

We study two CP sensitive triple-product asymmetries for neutralino production e+e- \to\tilde\chi^0_i \tilde\chi^0_j and the subsequent leptonic two-body decay \tilde\chi^0_i \to \tilde l l, \tilde l \to \tilde\chi^0_1 l, for \l= e,\mu,\tau. We calculate the asymmetries, cross sections and branching ratios in the Minimal Supersymmetric Standard Model with complex parameters \mu and M_1. We present numerical results for the asymmetries to be expected at a linear electron-positron collider in the 500 GeV range. The asymmetries can go up to 25 %. We estimate the event rates which are necessary to observe the asymmetries. Polarized electron and positron beams can significantly enhance the asymmetries and cross sections. In addition, we show how the two decay leptons can be distinguished by making use of their energy distributions.Comment: 22 pages, 7 figures; typos corrected, version to appear in Phys. Rev.

Impact of motion along the field direction on geometric-phase-induced false electric dipole moment signals

Geometric-phase-induced false electric dipole moment (EDM) signals, resulting from interference between magnetic field gradients and particle motion in electric fields, have been studied extensively in the literature, especially for neutron EDM experiments utilizing stored ultracold neutrons and co-magnetometer atoms. Previous studies have considered particle motion in the transverse plane perpendicular to the direction of the applied electric and magnetic fields. We show, via Monte Carlo studies, that motion along the field direction can impact the magnitude of this false EDM signal if the wall surfaces are rough such that the wall collisions can be modeled as diffuse, with the results dependent on the size of the storage cell's dimension along the field direction.Comment: 7 pages, 3 figures, NIM A, in pres

A CP asymmetry in e^+e^- \to \chi^0_i\chi^0_j \to \chi^0_j \tau stau_k with tau polarization

We propose a CP-odd asymmetry in the supersymmetric process e^+e^- \to \chi^0_i \chi^0_j \to \chi^0_j \tau stau_k by means of the transverse \tau polarization. We calculate the asymmetry and cross sections at a future linear collider in the 500 GeV c.m.s. energy range with longitudinal polarized beams and high luminosity. We work in the Minimal Supersymmetric Standard Model with complex parameters \mu, M_1 and A_\tau. The asymmetry can reach values up to 60 %. We also estimate the sensitivity for measuring the \tau polarization necessary to probe the CP asymmetry.Comment: 12 pages, 7 figure

Constraining spin-dependent short range interactions using neutron spin precession close to a mirror

Spin-dependent short range interactions of free neutrons with matter may be searched for in various ways. This short note discusses pseudomagnetic precession of trapped ultracold neutrons in vicinity to bulk matter, which should be several orders of magnitude more sensitive than any other method proposed so far.Comment: 4 page

UCN transport simulation in solid deuterium crystals

The extraction efficiency of ultracold neutrons from cryogenic moderators depends critically on the neutron transparency of the moderator material. The Monte Carlo simulation of the probability of the UCN going out from non-ideal (disordered) solid deuterium crystals has been performed. It was based on the use of the correlation function describing the density fluctuations in a disordered material, the latter being inferred from the measured very low neutron energy total cross sections for this material.Comment: 9 pages + 8 figures; expanded information about cross-sections used in calculations, references adde

CP-Violating Phases in the MSSM

We combine experimental bounds on the electric dipole moments of the neutron and electron with cosmological limits on the relic density of a gaugino-type LSP neutralino to constrain certain CP-violating phases appearing in the MSSM. We find that in the Constrained MSSM, the phase |\theta_\mu | < \pi/10, while the phase \theta_A remains essentially unconstrained.Comment: Summary of a talk presented at SUSY-96, College Park, Maryland, USA (May 1996), 4 pages in LaTeX including 4 embedded postscript figures, uses epsf.sty, espcrc2.st

CP violation in charged Higgs boson decays in the MSSM with complex parameters

Supersymmetric loop contributions can lead to different decay rates of H+\to t\bar b and H-\to b\bar t. We calculate the decay rate asymmetry \delta^CP = \frac{\Gamma(H+\to t\bar b)-\Gamma(H-\to b\bar t)}{{\Gamma(H+\to t\bar b)+\Gamma(H-\to b\bar t)} at next-to-leading order in the MSSM with complex parameters. We analyse the parameter dependence of \delta^CP with emphasis on the phases of A_t and A_b. It turns out that the most important contribution comes from the loop with stop, sbottom, and gluino. If this contribution is present, \delta^CP can go up to 10-15% for tan(beta)~10, and to ~5% for large values of tan(beta).Comment: Eqs. (9) and (25) corrected and numerical analysis modified accordingl

CPCP violation in minimal supersymmetric standard model

$CP$ violating phenomena predicted by the minimal supersymmetric standard model are discussed in a case where the $CP$ violating phases in SUSY sector are not suppressed. The electric dipole moments of the neutron and the electron are large, but can be smaller than their experimental upper bounds if the scalar quarks and leptons are heavier than a few TeV. $T$ violating asymmetries in the production processes of the different neutralino pair and the different chargino pair emerge at the tree level. They could be as large as of order $10^{-2}$ in unpolarized electron beam experiments and $10^{-1}$ in polarized electron beam experiments. In a pair production of the charginos of the same mass, the asymmetry emerges through the electric and the weak "electric" dipole moments of the charginos at the loop level, but its magnitude is at most of order $10^{-4}$.Comment: 7 pages with 7 figures, TKU-HEP 94/02; IFM 2/94, LaTeX with Elsevir Science Publisher's style file, espcrc2.sty. (To appear in the proceedings of the Third KEK Topical Conference on CP Violation, November 1993) Figures are not included. The complete PostScript file can be obtained by anonymous ftp from ape.sp.u-tokai.ac.jp in the directr

Parity-Violating Electron Scattering and the Electric and Magnetic Strange Form Factors of the Nucleon

Measurement of the neutral weak vector form factors of the nucleon provides unique access to the strange quark content of the nucleon. These form factors can be studied using parity-violating electron scattering. A comprehensive program of experiments has been performed at three accelerator laboratories to determine the role of strange quarks in the electromagnetic form factors of the nucleon. This article reviews the remarkable technical progress associated with this program, describes the various methods used in the different experiments, and summarizes the physics results along with recent theoretical calculations.Comment: Invited review for Annual Reviews of Nuclear and Particle Science, Oct 2012; as per Ann. Rev. policy, this is the originally submitted version, before refereeing and editorial wor