arXiv subjects

D. Su

Publications and source records attributed to D. Su.

11 recordsLinked to original sources

arXiv2025

Development of a Test System for Data Links of the ATLAS Inner Tracker (ITk) Upgrade Silicon Pixel Detector

This contribution introduces a novel test system developed to evaluate the signal transmission quality in high-speed data links for the 2026 Inner Tracker (ITk) upgrade of the ATLAS experiment. Using an FPGA-based data acquisition (DAQ) framework, the setup can run simultaneous Bit Error Rate (BER) tests for up to 64 channels and generate virtual eye diagrams, for qualifying the $\sim$26k electrical links at the ATLAS ITk data rate of 1.28Gb/s. The paper includes results from system calibration, yielding its contribution to the measured losses, and preliminary results from tests of prototype and pre-production assemblies of on-detector links of the three ATLAS ITk Pixel subsystems.

physics.ins-det↗

arXiv2022

Measurement of flavor asymmetry of light-quark sea in the proton with Drell-Yan dimuon production in $p+p$ and $p+d$ collisions at 120 GeV

Evidence for a flavor asymmetry between the $\bar u$ and $\bar d$ quark distributions in the proton has been found in deep-inelastic scattering and Drell-Yan experiments. The pronounced dependence of this flavor asymmetry on $x$ (fraction of nucleon momentum carried by partons) observed in the Fermilab E866 Drell-Yan experiment suggested a drop of the $\bar d\left(x\right) / \bar u\left(x\right)$ ratio in the $x > 0.15$ region. We report results from the SeaQuest Fermilab E906 experiment with improved statistical precision for $\bar d\left(x\right) / \bar u\left(x\right)$ in the large $x$ region up to $x=0.45$ using the 120 GeV proton beam. Two different methods for extracting the Drell-Yan cross section ratios, $\sigma^{pd} /2 \sigma^{pp}$, from the SeaQuest data give consistent results. The $\bar{d}\left(x\right) / \bar{u}\left(x\right)$ ratios and the $\bar d\left(x\right) - \bar u\left(x\right)$ differences are deduced from these cross section ratios for $0.13 < x < 0.45$. The SeaQuest and E866/NuSea $\bar{d}\left(x\right) / \bar{u}\left(x\right)$ ratios are in good agreement for the $x\lesssim 0.25$ region. The new SeaQuest data, however, show that $\bar d\left(x\right)$ continues to be greater than $\bar u\left(x\right)$ up to the highest $x$ value ($x = 0.45$). The new results on $\bar{d}\left(x\right) / \bar{u}\left(x\right)$ and $\bar{d}\left(x\right) - \bar{u}\left(x\right)$ are compared with various parton distribution functions and theoretical calculations.

hep-ph↗

arXiv2021

The Asymmetry of Antimatter in the Proton

The fundamental building blocks of the proton, quarks and gluons, have been known for decades. However, we still have an incomplete theoretical and experimental understanding of how these particles and their dynamics give rise to the quantum bound state of the proton and its physical properties, such as for example its spin. The two up and the single down quarks that comprise the proton in the simplest picture account only for a few percent of the proton mass, the bulk of which is in the form of quark kinetic and potential energy and gluon energy from the strong force. An essential feature of this force, as described by quantum chromodynamics, is its ability to create matter-antimatter quark pairs inside the proton that exist only for a very short time. Their fleeting existence makes the antimatter quarks within protons difficult to study, but their existence is discernible in reactions where a matter-antimatter quark pair annihilates. In this picture of quark-antiquark creation by the strong force, the probability distributions as a function of momentum for the presence of up and down antimatter quarks should be nearly identical, since their masses are quite similar and small compared to the mass of the proton. In the present manuscript, we show evidence from muon pair production measurements that these distributions are significantly different, with more abundant down antimatter quarks than up antimatter quarks over a wide range of momentum. These results revive interest in several proposed mechanisms as the origin of this antimatter asymmetry in the proton that had been disfavored by the previous results and point to the future measurements that can distinguish between these mechanisms.

hep-ph↗

arXiv2021

Quantum circuits with many photons on a programmable nanophotonic chip

Growing interest in quantum computing for practical applications has led to a surge in the availability of programmable machines for executing quantum algorithms. Present day photonic quantum computers have been limited either to non-deterministic operation, low photon numbers and rates, or fixed random gate sequences. Here we introduce a full-stack hardware-software system for executing many-photon quantum circuits using integrated nanophotonics: a programmable chip, operating at room temperature and interfaced with a fully automated control system. It enables remote users to execute quantum algorithms requiring up to eight modes of strongly squeezed vacuum initialized as two-mode squeezed states in single temporal modes, a fully general and programmable four-mode interferometer, and genuine photon number-resolving readout on all outputs. Multi-photon detection events with photon numbers and rates exceeding any previous quantum optical demonstration on a programmable device are made possible by strong squeezing and high sampling rates. We verify the non-classicality of the device output, and use the platform to carry out proof-of-principle demonstrations of three quantum algorithms: Gaussian boson sampling, molecular vibronic spectra, and graph similarity.

quant-ph↗

arXiv2017

Superconducting epitaxial YBa2Cu3O7-{\delta} on SrTiO3 buffered Si (001)

Thin films of optimally-doped (001)-oriented YBa2Cu3O7-{\delta} are epitaxially integrated on silicon (001) through growth on a single crystalline SrTiO3 buffer. The former is grown using pulsed-laser deposition and the latter is grown on Si using oxide molecular beam epitaxy. The single crystal nature of the SrTiO3 buffer enables high quality YBa2Cu3O7-{\delta} films exhibiting high transition temperatures to be integrated on Si. For a 30 nm thick SrTiO3 buffer, 50 nm thick YBa2Cu3O7-{\delta} films that exhibit a transition temperature of ~ 93 K, and a narrow transition width (< 5 K) are achieved. The integration of single crystalline YBa2Cu3O7-{\delta} on Si (001) paves the way for the potential exploration of cuprate materials in a variety of applications.

cond-mat.supr-con↗

arXiv2017

The SeaQuest Spectrometer at Fermilab

The SeaQuest spectrometer at Fermilab was designed to detect oppositely-charged pairs of muons (dimuons) produced by interactions between a 120 GeV proton beam and liquid hydrogen, liquid deuterium and solid nuclear targets. The primary physics program uses the Drell-Yan process to probe antiquark distributions in the target nucleon. The spectrometer consists of a target system, two dipole magnets and four detector stations. The upstream magnet is a closed-aperture solid iron magnet which also serves as the beam dump, while the second magnet is an open aperture magnet. Each of the detector stations consists of scintillator hodoscopes and a high-resolution tracking device. The FPGA-based trigger compares the hodoscope signals to a set of pre-programmed roads to determine if the event contains oppositely-signed, high-mass muon pairs.

physics.ins-det↗

arXiv2014

Band-gap engineering at a semiconductor - crystalline oxide interface

The epitaxial growth of crystalline oxides on semiconductors provides a pathway to introduce new functionalities to semiconductor devices. Key to electrically coupling crystalline oxides with semiconductors to realize functional behavior is controlling the manner in which their bands align at interfaces. Here we apply principles of band gap engineering traditionally used at heterojunctions between conventional semiconductors to control the band offset between a single crystalline oxide and a semiconductor. Reactive molecular beam epitaxy is used to realize atomically abrupt and structurally coherent interfaces between SrZr$_{x}$Ti$_{1-x}$O$_3$ and Ge, in which the band-gap of the former is enhanced with Zr content $x$. We present structural and electrical characterization of SrZr$_{x}$Ti$_{1-x}$O$_3$-Ge heterojunctions for $x$ = 0.2 to 0.75 and demonstrate the band offset can be tuned from type-II to type-I, with the latter being verified using photoemission measurements. The type-I band offset provides a platform to integrate the dielectric, ferroelectric and ferromagnetic functionalities of oxides with semiconducting devices.

cond-mat.mtrl-sci↗

arXiv2012

Engineering polarization rotation in a ferroelectric superlattice

A key property that drives research in ferroelectric perovskite oxides is their strong piezoelectric response in which an electric field is induced by an applied strain, and vice-versa for the converse piezoelectric effect. We have achieved an experimental enhancement of the piezoelectric response and dielectric tunability in artificially layered epitaxial PbTiO$_{3}$/CaTiO$_{3}$ superlattices through an engineered rotation of the polarization direction. As the relative layer thicknesses within the superlattice were changed from sample to sample we found evidence for polarization rotation in multiple x-ray diffraction measurements. Associated changes in functional properties were seen in electrical measurements and piezoforce microscopy. The results demonstrate a new approach to inducing polarization rotation under ambient conditions in an artificially layered thin film.

cond-mat.mtrl-sci↗

arXiv2012

Ferroelectric PbTiO$_{3}$/SrRuO$_{3}$ superlattices with broken inversion symmetry

We have fabricated PbTiO$_{3}$/SrRuO$_{3}$ superlattices with ultra-thin SrRuO$_{3}$ layers. Due to the superlattice geometry, the samples show a large anisotropy in their electrical resistivity, which can be controlled by changing the thickness of the PbTiO$_{3}$ layers. Therefore, along the ferroelectric direction, SrRuO$_{3}$ layers can act as dielectric, rather than metallic, elements. We show that, by reducing the concentration of PbTiO$_{3}$, an increasingly important effect of polarization asymmetry due to compositional inversion symmetry breaking occurs. The results are significant as they represent a new class of ferroelectric superlattices, with a rich and complex phase diagram. By expanding our set of materials we are able to introduce new behaviors that can only occur when one of the materials is not a perovskite titanate. Here, compositional inversion symmetry breaking in bi-color superlattices, due to the combined variation of A and B site ions within the superlattice, is demonstrated using a combination of experimental measurements and first principles density functional theory.

cond-mat.mtrl-sci↗

arXiv2011

Test Beam Results of 3D Silicon Pixel Sensors for the ATLAS upgrade

Results on beam tests of 3D silicon pixel sensors aimed at the ATLAS Insertable-B-Layer and High Luminosity LHC (HL-LHC)) upgrades are presented. Measurements include charge collection, tracking efficiency and charge sharing between pixel cells, as a function of track incident angle, and were performed with and without a 1.6 T magnetic field oriented as the ATLAS Inner Detector solenoid field. Sensors were bump bonded to the front-end chip currently used in the ATLAS pixel detector. Full 3D sensors, with electrodes penetrating through the entire wafer thickness and active edge, and double-sided 3D sensors with partially overlapping bias and read-out electrodes were tested and showed comparable performance.

physics.ins-det↗

arXiv2010

Atomic Imaging Using Secondary Electrons in a Scanning Transmission Electron Microscope : Experimental Observations and Possible Mechanisms

We report our detailed investigation of high-resolution imaging using secondary electrons (SE) with a subnanometer probe in an aberration-corrected transmission electron microscope, Hitachi HD2700C. This instrument also allows us to acquire the corresponding annular-dark-field (ADF) images simultaneously and separately. We demonstrate that atomic SE imaging is achievable for a wide range of elements, from uranium to carbon. Using the ADF images as a reference, we study the SE image intensity and contrast as a function of applied bias, atomic number, crystal tilt and thickness to shed light on the origin of the unexpected ultrahigh resolution in SE imaging. We have also demonstrated that the SE signal is sensitive to the terminating species at a crystal surface. Possible mechanisms for atomicscale SE imaging are proposed. The ability to image both the surface and bulk of a sample at atomic scale is unprecedented, and could revolutionize the field of electron microscopy and imaging.

cond-mat.mtrl-sci↗