arXiv subjects

W. Yao

Publications and source records attributed to W. Yao.

26 records · Page 2Linked to original sources

arXiv2019

A New Cryogenic Apparatus to Search for the Neutron Electric Dipole Moment

A cryogenic apparatus is described that enables a new experiment, nEDM@SNS, with a major improvement in sensitivity compared to the existing limit in the search for a neutron Electric Dipole Moment (EDM). It uses superfluid $^4$He to produce a high density of Ultra-Cold Neutrons (UCN) which are contained in a suitably coated pair of measurement cells. The experiment, to be operated at the Spallation Neutron Source at Oak Ridge National Laboratory, uses polarized $^3$He from an Atomic Beam Source injected into the superfluid $^4$He and transported to the measurement cells as a co-magnetometer. The superfluid $^4$He is also used as an insulating medium allowing significantly higher electric fields, compared to previous experiments, to be maintained across the measurement cells. These features provide an ultimate statistical uncertainty for the EDM of $2-3\times 10^{-28}$ e-cm, with anticipated systematic uncertainties below this level.

physics.ins-det↗

arXiv2019

The neutron electric dipole moment experiment at the Spallation Neutron Source

Novel experimental techniques are required to make the next big leap in neutron electric dipole moment experimental sensitivity, both in terms of statistics and systematic error control. The nEDM experiment at the Spallation Neutron Source (nEDM@SNS) will implement the scheme of Golub & Lamoreaux [Phys. Rep., 237, 1 (1994)]. The unique properties of combining polarized ultracold neutrons, polarized $^3$He, and superfluid $^4$He will be exploited to provide a sensitivity to $\sim 10^{-28}\,e{\rm \,\cdot\, cm}$. Our cryogenic apparatus will deploy two small ($3\,{\rm L}$) measurement cells with a high density of ultracold neutrons produced and spin analyzed in situ. The electric field strength, precession time, magnetic shielding, and detected UCN number will all be enhanced compared to previous room temperature Ramsey measurements. Our $^3$He co-magnetometer offers unique control of systematic effects, in particular the Bloch-Siegert induced false EDM. Furthermore, there will be two distinct measurement modes: free precession and dressed spin. This will provide an important self-check of our results. Following five years of "critical component demonstration," our collaboration transitioned to a "large scale integration" phase in 2018. An overview of our measurement techniques, experimental design, and brief updates are described in these proceedings.

nucl-ex↗

arXiv2016

An apparatus for studying electrical breakdown in liquid helium at 0.4 K and testing electrode materials for the SNS nEDM experiment

We have constructed an apparatus to study DC electrical breakdown in liquid helium at temperatures as low as 0.4 K and at pressures between the saturated vapor pressure and $\sim$600 torr. The apparatus can house a set of electrodes that are 12 cm in diameter with a gap of $1-2$ cm between them, and a potential up to $\pm 50$ kV can be applied to each electrode. Initial results demonstrated that it is possible to apply fields exceeding 100 kV/cm in a 1 cm gap between two electropolished stainless steel electrodes 12 cm in diameter for a wide range of pressures at 0.4 K. We also measured the current between two electrodes. Our initial results, $I<1$ pA at 45 kV, correspond to a lower bound on the effective volume resistivity of LHe of $ρ_V > 5\times10^{18}$ $Ω\cdot$cm. This lower bound is 5 times larger than the bound previously measured. We report the design, construction, and operational experience of the apparatus, as well as initial results.

physics.ins-det↗

arXiv2014

High electric field development for the SNS nEDM Experiment

A new experiment to search for the permanent electric dipole moment of the neutron is being developed for installation at the Spallation Neutron Source at Oak Ridge National Laboratory. This experiment will be performed in liquid helium at ? 0:4 K and requires a large electric field (E ~ 75 kV/cm) to be applied in liquid helium. We have constructed a new HV test apparatus to study electric breakdown in liquid helium. Initial results demonstrated that it is possible to apply fields exceeding 100 kV/cm in a 1 cm gap between two electropolished stainless steel electrodes12 cm in diameter for a wide range of pressures.

physics.ins-det↗

arXiv2011

Improved $b$-jet Energy Correction for $H \to b\bar{b}$ Searches at CDF

We present a method for improving the $b$-jet energy resolution in order to improve the signal sensitivity in searches for particles decaying to a $b$ quark and anti-$b$ quark. A correction function is computed for individual jets, which combines information from the secondary vertex tagger, the offline tracking and standard calorimeter-based jet-energy reconstruction algorithm in order to provide a more accurate measurement of the true $b$-quark energy. We apply the correction to Monte-Carlo-simulated jets in the process $WH \rightarrow \ell νb\bar b$ and find an improvement in both the mean and the resolution of the $b$-jet energy with respect to the $b$-quark energy. The correction improves the measured Higgs dijet invariant mass resolution from $\sim$ 15%(standard jet corrections) to $\sim$ 11%(improved jet corrections) in the Higgs mass range from 100 GeV/$c^2$ - 150 GeV/$c^2$. Using the corrected $b$-jet energies instead of the standard calorimeter-based $b$-jet energies results in a $\sim$ 9% improvement in the expected sensitivity for Higgs boson production cross section in the most sensitive search region of the $WH \rightarrow \ell νb\bar b$ analysis, which is two tagged jets and one charged central lepton.

hep-ex↗

arXiv2007

Potential for Precision Measurement of Solar Neutrino Luminosity by HERON

Results are presented for a simulation carried out to test the precision with which a detector design (HERON) based on a superfluid helium target material should be able to measure the solar pp and Be7 fluxes. It is found that precisions of +/- 1.68% and +/- 2.97% for pp and Be7 fluxes, respectively, should be achievable in a 5-year data sample. The physics motivation to aim for these precisions is outlined as are the detector design, the methods used in the simulation and sensitivity to solar orbit eccentricity.

astro-ph↗

arXiv2002

Rayleigh Scattering in Rare Gas Liquids

The Rayleigh scattering length has been calculated for rare-gas liquids in the ultraviolet for the frequencies at which they luminesce. The calculations are based on the measured dielectric constants in the gas phase, except in the case of xenon for which measurements are available in the liquid. The scattering length mayplace constraints on the design of some large-scale detectors, using uv luminescence, being proposed to observe solar neutrinos and dark matter. Rayleigh scattering in mixtures of rare-gas mixtures is also discussed.

hep-ex↗

arXiv1996

Precision SUSY Measurements at LHC

If supersymmetry exists at the electroweak scale, then it should be discovered at the LHC. Determining masses, of supersymmetric particles however, is more difficult. In this paper, methods are discussed to determine combinations of masses and of branching ratios precisely from experimentally observable distributions. In many cases such measurements alone can greatly constrain the particular supersymmetric model and determine its parameters with an accuracy of a few percent. Most of the results shown correspond to one year of running at LHC at ``low luminosity'.

hep-ph↗