arXiv subjects

Y. T. Shen

Publications and source records attributed to Y. T. Shen.

4 recordsLinked to original sources

arXiv2016

Characterization and Performance of Germanium Detectors with sub-keV Sensitivities for Neutrino and Dark Matter Experiments

Germanium ionization detectors with sensitivities as low as 100 eVee (electron-equivalent energy) open new windows for studies on neutrino and dark matter physics. The relevant physics subjects are summarized. The detectors have to measure physics signals whose amplitude is comparable to that of pedestal electronic noise. To fully exploit this new detector technique, various experimental issues including quenching factors, energy reconstruction and calibration, signal triggering and selection as well as evaluation of their associated efficiencies have to be attended. The efforts and results of a research program to address these challenges are presented.

physics.ins-det↗

arXiv2013

The tunneling spectra and superconducting gaps observed by using scanning tunneling microscope near the grain-boundary of FeSe0.3Te0.7 films

We used STM to study the tunneling spectra of FeSe0.3Te0.7 films with two orientations of ab-planes and the connection ramp between them. We have discovered that, using pulse laser deposition (PLD) method, the a- and b-axis of the FeSe0.3Te0.7 film deposited on Ar-ion-milled Magnesium Oxide (MgO) substrate are rotated 45 degree with respect to those of MgO, while the a- and b-axis of the film grown on pristine MgO substrate are parallel to those of MgO. With photolithography and this technique, we can prepare FeSe0.3Te0.7 film with two kinds of orientations on the same MgO substrate, and the connection between them forms a ramp at an angle about 25 degree to the substrate plane. In the planar region with either 0 degree or 45 degree orientation, we have observed tunneling spectra with a superconducting gap about 5 meV and 1.78 meV respectively. However, a much larger gap about 18 meV has been observed in the ramp region. Furthermore, we have also observed a small zero-bias conductance peak (ZBCP) inside the large gap at T = 4.3K. The ZBCP becomes smaller and disappear with increasing temperature to 7 K. The possible causes of such large gap and the ZBCP will be discussed.

cond-mat.supr-con↗

arXiv2013

Conductance spectrum and superconducting gap structures observed in c-axis FeSe0.3Te0.7/Au junctions

The electric transport properties of superconducting FeSe0.3Te0.7/Au c-axis (S/N) junctions, fabricated by using Pulsed Laser Deposition technique, have been investigated in the temperature range of 2 K to the superconducting transition temperature TC ~ 13.5 K, and in the presence of applied magnetic fields from 0 to 9 T. A large zero bias conductance peak has always been observed in the conductance spectra of several batches of junctions. In addition, we have also found several gap-like features. Using the extended BTK theory with the currently favored nodeless S+- wave symmetry, our conductance spectrum can be reproduced quite well in the low bias range with Δ1 = 4 meV, and Δ2 = 6 meV at 2 K. However the experimental conductance spectrum is substantially below the calculated one in the high bias range. Furthermore, there is a conductance minimum at about 20 meV, which may be the reason for the discrepancy.

cond-mat.supr-con↗

arXiv2008

Study of B-> phi phi K Decays

We report an observation of the decay B^\pm -> ϕϕK^\pm and evidence for B^0 -> ϕϕK^0. These results are based on a 414 fb^{-1} data sample collected with the Belle detector at the KEKB asymmetric-energy e^+e^- collider operating at the Υ(4S) resonance. The branching fractions for these decay modes are measured to be Br(B^{\pm} -> ϕϕK^\pm) = (3.2^{+0.6}_{-0.5} +- 0.3) * 10^{-6} and Br(B^{0} \to ϕϕK^{0}) = (2.3^{+1.0}_{-0.7} +- 0.2) * 10^{-6} for ϕϕinvariant mass below 2.85 GeV/c^2. The corresponding partial rate asymmetry for the charged B mode is measured to be A_{CP}(B^\pm -> ϕϕK^\pm) = 0.01^{+0.19}_{-0.16} +- 0.02. We also study the decays B^\pm -> J/ψK^\pm and B^\pm -> η_c K^\pm, where the J/ψand η_c decay to final states with four charged kaons. We find A_{CP}(B^\pm -> ϕϕK^\pm) with the ϕϕcandidates within the η_c mass region is 0.15^{+0.16}_{-0.17} +- 0.02, consistent with no asymmetry.

hep-ex↗