arXiv subjects

Z. Liang

Publications and source records attributed to Z. Liang.

27 records · Page 2Linked to original sources

arXiv2020

Beam test results of IHEP-NDL Low Gain Avalanche Detectors(LGAD)

To meet the timing resolution requirement of up-coming High Luminosity LHC (HL-LHC), a new detector based on the Low-Gain Avalanche Detector(LGAD), High-Granularity Timing Detector (HGTD), is under intensive research in ATLAS. Two types of IHEP-NDL LGADs(BV60 and BV170) for this update is being developed by Institute of High Energy Physics (IHEP) of Chinese Academic of Sciences (CAS) cooperated with Novel Device Laboratory (NDL) of Beijing Normal University and they are now under detailed study. These detectors are tested with $5GeV$ electron beam at DESY. A SiPM detector is chosen as a reference detector to get the timing resolution of LGADs. The fluctuation of time difference between LGAD and SiPM is extracted by fitting with a Gaussian function. Constant fraction discriminator (CFD) method is used to mitigate the effect of time walk. The timing resolution of $41 \pm 1 ps$ and $63 \pm 1 ps$ are obtained for BV60 and BV170 respectively.

physics.ins-det↗

arXiv2020

Radiation Campaign of HPK Prototype LGAD sensors for the High-Granularity Timing Detector (HGTD)

We report on the results of a radiation campaign with neutrons and protons of Low Gain Avalanche Detectors (LGAD) produced by Hamamatsu (HPK) as prototypes for the High-Granularity Timing Detector (HGTD) in ATLAS. Sensors with an active thickness of 50~$μ$m were irradiated in steps of roughly 2$\times$ up to a fluence of $3\times10^{15}~\mathrm{n_{eq}cm^{-2}}$. As a function of the fluence, the collected charge and time resolution of the irradiated sensors will be reported for operation at $-30^{\circ}$.

physics.ins-det↗

arXiv2015

Recent Technological Developments on LGAD and iLGAD Detectors for Tracking and Timing Applications

This paper reports the last technological development on the Low Gain Avalanche Detector (LGAD) and introduces a new architecture of these detectors called inverse-LGAD (iLGAD). Both approaches are based on the standard Avalanche Photo Diodes (APD) concept, commonly used in optical and X-ray detection applications, including an internal multiplication of the charge generated by radiation. The multiplication is inherent to the basic n++-p+-p structure, where the doping profile of the p+ layer is optimized to achieve high field and high impact ionization at the junction. The LGAD structures are optimized for applications such as tracking or timing detectors for high energy physics experiments or medical applications where time resolution lower than 30 ps is required. Detailed TCAD device simulations together with the electrical and charge collection measurements are presented through this work.

physics.ins-det↗

arXiv2012

All-sky Observational Evidence for An Inverse Correlation between Dust Temperature and Emissivity Spectral Index

We show that a one-component variable-emissivity-spectral-index model (the free-α model) provides more physically motivated estimates of dust temperature at the Galactic polar caps than one- or two-component fixed-emissivity-spectral-index models (fixed-α models) for interstellar dust thermal emission at far-infrared and millimeter wavelengths. For the comparison we have fit all-sky one-component dust models with fixed or variable emissivity spectral index to a new and improved version of the 210-channel dust spectra from the COBE-FIRAS, the 100 - 240 μm maps from the COBE-DIRBE and the 94 GHz dust map from the WMAP. The best model, the free-α model, is well constrained by data at 60-3000 GHz over 86 per cent of the total sky area. It predicts dust temperature (Tdust) to be 13.7-22.7 (+/-1.3) K, the emissivity spectral index (α) to be 1.2 - 3.1 (+/-0.3) and the optical depth (τ) to range 0.6 - 46 x 10^(-5) at ν0 = 900 GHz (λ0 = 333 μm) with a 23 per cent uncertainty. Using these estimates, we present all-sky evidence for an inverse correlation between the emissivity spectral index and dust temperature, which fits the relation α = 1/(δ+ω Tdust) with δ = -0.510 +/- 0.011 and ω = 0.059 +/- 0.001. This best model will be useful to cosmic microwave background experiments for removing foreground dust contamination and it can serve as an all-sky extended-frequency reference for future higher resolution dust models.

astro-ph.GA↗

arXiv2012

Study of ageing in Al-Mg-Si alloys by positron annihilation spectroscopy

In many common Al-Mg-Si alloys (6000 series) intermediate storage at or near 'room temperature' after solutionising leads to pronounced changes of the precipitation kinetics during the ensuing artificial ageing step at \approx 180°C. This is not only an annoyance in production, but also a challenge for researchers. We studied the kinetics of natural 'room temperature' ageing (NA) in Al-Mg-Si alloys by means of various different techniques, namely electrical resistivity and hardness measurement, thermoanalysis and positron lifetime and Doppler broadening (DB) spectroscopy to identify the stages in which the negative effect of NA on artificial ageing might appear. Positron lifetime measurements were carried out in a fast mode, allowing us to measure average lifetimes in below 1 minute. DB measurements were carried out with a single detector and a 68Ge positron source by employing high momentum analysis. The various measurements show that NA is much more complex than anticipated and at least four different stages can be distinguished. The nature of these stages cannot be given with certainty, but a possible sequence includes vacancy diffusion to individual solute atoms, nucleation of solute clusters, Mg agglomeration to clusters and coarsening or ordering of such clusters. Positron lifetime measurements after more complex ageing treatments involving storage at 0°C, 20°C and 180°C have also been carried out and help to understand the mechanisms involved.

cond-mat.mtrl-sci↗

arXiv2012

The SM and NLO Multileg and SM MC Working Groups: Summary Report

The 2011 Les Houches workshop was the first to confront LHC data. In the two years since the previous workshop there have been significant advances in both soft and hard QCD, particularly in the areas of multi-leg NLO calculations, the inclusion of those NLO calculations into parton shower Monte Carlos, and the tuning of the non-perturbative parameters of those Monte Carlos. These proceedings describe the theoretical advances that have taken place, the impact of the early LHC data, and the areas for future development.

hep-ph↗

arXiv2010

The Tate-Shafarevich group for elliptic curves with complex multiplication II

Let E be an elliptic curve over Q with complex multiplication. The aim of the present paper is to strengthen the theoretical and numerical results of \cite{CZS}. For each prime p, let t_{E/Q, p} denote the Z_p-corank of the p-primary subgroup of the Tate-Shafarevich group of E/Q. For each ε 0, we prove that t_{E/Q, p} is bounded above by (1/2+ε)p for all sufficiently large good ordinary primes p. We also do numerical calculations on one such E of rank 3, and 5 such E of rank 2, showing in all cases that t_{E/Q, p} = 0 for all good ordinary primes p < 30,000. In fact, we show that, with the possible exception of one good ordinary prime in this range for just one of the curves of rank 2, the p-primary subgroup of the Tate-Shafarevich group of the curve is zero (always supposing p is a good ordinary prime).

math.NT↗

arXiv2009

Tate Safarevich groups of elliptic curves with complex multiplication

We show that the number of copies of ${\Bbb Q}_p/{\Bbb Z}_p$ in the Tate-Shafarevich group of an elliptic curve $E$ over ${\Bbb Q}$ with complex multipication, is at most $2p - g$, where $g$ is the rank of $E({\Bbb Q})$, and for all sufficiently large good ordinary primes $p$.

math.NT↗

arXiv1996

Testing the mechanisms proposed in different models for single-spin asymmetries

It is shown that the origin of the striking left-right asymmetries observed in single-spin inclusive hadron production processes in high energy hadron-hadron collisions can be traced by performing suitable experiments. Several new experiments are proposed. The possible outcomes are summarized together with those of other relevant experiments which have already been suggested. It is pointed out that the results of such a set of experiments will not only be able to differentiate between existing theoretical models, but also be helpful in locating the source(s) of the observed asymmetries.

hep-ph↗