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Junjie Zhu

Publications and source records attributed to Junjie Zhu.

49 records · Page 3Linked to original sources
arXiv2017

A Programmable Time Alignment Scheme for Detector Signals from the Upgraded muon Spectrometer at the ATLAS Experiment

We present a programmable time alignment scheme used in an ASIC for the ATLAS forward muon trigger development. The scheme utilizes regenerated clocks with programmable phases to compensate for the timing offsets introduced by different detector trace lengths. Each ASIC used in the design has 104 input channels with delay compensation circuitry providing steps of ~ 3 ns and a full range of 25 ns for each channel. Detailed implementation of the scheme including majority logic to suppress single-event effects is presented. The scheme is flexible and fully synthesizable. The approach is adaptable to other applications with similar phase shifting requirements. In addition, the design is resource efficient and is suitable for cost-effective digital implementation with a large number of channels.

physics.ins-det↗
arXiv2017

Design of a Trigger Data Serializer ASIC for the Upgrade of the ATLAS Forward Muon Spectrometer

The small-strip Thin Gap Chamber (sTGC) will be used for both triggering and precision tracking purposes in the upgrade of the ATLAS forward muon spectrometer. Both sTGC pad and strip detectors are readout by a Trigger Data Serializer (TDS) ASIC in the trigger path. This ASIC has two operation modes to prepare trigger data from pad and strip detectors respectively. The pad mode (pad-TDS) collects the firing status for up to 104 pads from one detector layer and transmits the data at 4.8 Gbps to the pad trigger extractor every 25 ns. The pad trigger extractor collects pad-TDS data from eight detector layers and defines a region of interest along the path of a muon candidate. In the strip mode (strip-TDS), the deposited charges from up to 128 strips are buffered, time-stamped, and a trigger matching procedure is performed to read out strips underneath the region of interest. The strip-TDS output is also transmitted at 4.8 Gbps to the following FPGA processing circuits. Details about the ASIC design and test results are presented in this paper.

physics.ins-det↗
arXiv2016

Determination of the $WW$ polarization fractions in $pp \to W^\pm W^\pm jj$ using a deep machine learning technique

The unitarization of the longitudinal vector boson scattering (VBS) cross section by the Higgs boson is a fundamental prediction of the Standard Model which has not been experimentally verified. One of the most promising ways to measure VBS uses events containing two leptonically-decaying same-electric-charge $W$ bosons produced in association with two jets. However, the angular distributions of the leptons in the $W$ boson rest frame, which are commonly used to fit polarization fractions, are not readily available in this process due to the presence of two neutrinos in the final state. In this paper we present a method to alleviate this problem by using a deep machine learning technique to recover these angular distributions from measurable event kinematics and demonstrate how the longitudinal-longitudinal scattering fraction could be studied. We show that this method doubles the expected sensitivity when compared to previous proposals.

hep-ph↗
arXiv2015

Electroweak results from the ATLAS and CMS experiments

I summarize an extensive ATLAS and CMS electroweak physics program that involves a variety of single boson, diboson, triboson, and vector boson scattering measurements. The relevance of these studies to our understanding of the electroweak sector and electroweak symmetry breaking is emphasized. I describe the recent results and prospects for future measurements.

hep-ex↗
arXiv2015

FPGA Implementation of a Fixed Latency Scheme in a Signal Packet Router for the Upgrade of ATLAS Forward Muon Trigger Electronics

We propose a new fixed latency scheme for Xilinx gigabit transceivers that will be used in the upgrade of the ATLAS forward muon spectrometer at the Large Hadron Collider. The fixed latency scheme is implemented in a 4.8 Gbps link between a frontend data serializer ASIC and a packet router. To achieve fixed latency, we use IO delay and dedicated carry in resources in a Xilinx FPGA, while minimally relying on the embedded features of the FPGA transceivers. The scheme is protocol independent and can be adapted to FPGA from other vendors with similar resources. This paper presents a detailed implementation of the fixed latency scheme, as well as simulations of the real environment in the ATLAS forward muon region.

physics.ins-det↗
arXiv2015

Characterization of a Serializer ASIC chip for the upgrade of the ATLAS muon detector

We report on the design of a serializer ASIC to be used in the ATLAS forward muon detector for trigger data transmission. We discuss the performance of a prototype chip covering power dissipation, latency and stable operating line rate. Tests show that the serializer is capable of running at least at 5.76 Gbps with a bit error ratio below 1x10^{-15}, and a power consumption of 200 mW running at 4.8 Gbps. The latency between the start of loading 30 bits into the serializer to the transmission of the first bit from the serializer is measured to be about 6 ns.

physics.ins-det↗
arXiv2014

Diboson Production in Proton-Proton Collisions at $\sqrt{s}=7$ TeV

This review article summarizes results on the production cross section measurements of electroweak boson pairs ($WW$, $WZ$, $ZZ$, $Wγ$ and $Zγ$) at the Large Hadron Collider (LHC) in $pp$ collisions at a center-of-mass energy of $\sqrt{s}=7$ \TeV. The two general-purpose detectors at the LHC, ATLAS and CMS, recorded an integrated luminosity of $5fb^{-1}$ in 2011, which offered the possibility to study the properties of diboson production to high precision. These measurements test predictions of the Standard Model (SM) in a new energy regime and are crucial for the understanding and the measurement of the SM Higgs boson and other new particles. In this review, special emphasis is drawn on the combination of results from both experiments and a common interpretation with respect to state-of-the-art SM predictions.

hep-ex↗
arXiv2014

Performance of Multiantenna Linear MMSE Receivers in Doubly Stochastic Networks

A technique is presented to characterize the Signal-to-Interference-plus-Noise Ratio (SINR) of a representative link with a multiantenna linear Minimum-Mean-Square-Error receiver in a wireless network with transmitting nodes distributed according to a doubly stochastic process, which is a generalization of the Poisson point process. The cumulative distribution function of the SINR of the representative link is derived assuming independent Rayleigh fading between antennas. Several representative spatial node distributions are considered, including networks with both deterministic and random clusters, strip networks (used to model roadways, e.g.), hard-core networks and networks with generalized path-loss models. In addition, it is shown that if the number of antennas at the representative receiver is increased linearly with the nominal node density, the signal-to-interference ratio converges in distribution to a random variable that is non-zero in general, and a positive constant in certain cases. This result indicates that to the extent that the system assumptions hold, it is possible to scale such networks by increasing the number of receiver antennas linearly with the node density. The results presented here are useful in characterizing the performance of multiantenna wireless networks in more general network models than what is currently available.

cs.IT↗
arXiv2014

Performance of Multi-Antenna Linear MMSE Receivers in Non-homogeneous Poisson and Poisson Cluster Networks

A technique is presented to evaluate the performance of a wireless link with a multi-antenna linear Minimum-Mean-Square Error (MMSE) receiver in the presence of interferers distributed according to non-homogeneous Poisson processes or Poisson cluster processes on the plane. The Cumulative Distribution Function (CDF) of the Signal-to-Interference-plus-Noise Ratio (SINR) of a representative link is derived for both types of networks assuming independent Rayleigh fading between antennas. Several representative spatial node distributions are considered, for which the derived CDFs are verified by numerical simulations. In addition, for non-homogeneous Poisson networks, it is shown that the Signal-to-Interference Ratio (SIR) converges to a deterministic non-zero value if the number of antennas at the representative receiver increases linearly with the nominal interferer density. This indicates that to the extent that the system assumptions hold, it is possible to scale such networks by increasing the number of receiver antennas linearly with user density. The results presented here are useful in characterizing the performance of multiantenna wireless networks with non-homogenous spatial node distributions and networks with clusters of users which often arise in practice, but for which few results are available.

cs.IT↗
arXiv2012

The RPC-based proposal for the ATLAS forward muon trigger upgrade in view of super-LHC

The innermost station of the present ATLAS forward muon detector needs to be upgraded for the super-LHC. We present a proposal to replace it with a sandwiched detector composed of several layers of small-radius Monitored Drift Tube chambers (sMDT) for precision tracking measurement and two stations of multi-gap Resistive Plate Chambers (mRPC) for triggering purpose. We describe the layout of the upgraded detector and the trigger strategy. Several modifications to the RPCs used in the ATLAS barrel region are needed to satisfy the super-LHC requirements. Various studies with the proposed mRPC timing resolution, spatial resolution and rate capability have been performed.

physics.ins-det↗
arXiv2011

Performance of Multi-Antenna MMSE Receivers in Non-homogeneous Poisson Networks

A technique to compute the Cumulative Distribution Function (CDF) of the Signal-to-Interference-plus-Noise-Ratio (SINR) for a wireless link with a multi-antenna, Linear, Minimum-Mean-Square-Error (MMSE) receiver in the presence of interferers distributed according to a non-homogenous Poisson point process on the plane, and independent Rayleigh fading between antennas is presented. This technique is used to compute the CDF of the SINR for several different models of intensity functions, in particular, power-law intensity functions, circular-symmetric Gaussian intensity functions and intensity functions described by a polynomial in a bounded domain. Additionally it is shown that if the number of receiver antennas is scaled linearly with the intensity function, the SINR converges in probability to a limit determined by the "shape" of the underlying intensity function. This work generalizes known results for homogenous Poisson networks to non-homogenous Poisson networks.

cs.IT↗