chung-yao chao fellowship...

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Chung-Yao Chao Fellowship

Interview

5 月 22 日， 2015

Loh Chang Wei

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个人简介

Loh, Chang Wei (罗章维)

马来西亚籍

2015 年 3 月加入南京大学祁鸣教授科研组

Thomson Reuters ResearcherID # I-1310-2014

http://www.researcherid.com/rid/I-1310-2014

南京大学的科研路线：

Diamond detector (ATLAS upgrade and beyond)

Daya Bay experiment data analysis

http://www.researcherid.com/rid/I-1310-2014

Education

Ph.D. from the University of British Columbia, Canada

加拿大英属哥伦比亚大学， 2014UBC Four-Year Fellowship, 2009

Graduate Entrance Scholarship, 2006

B.Sc. from the University of Malaya, Malaysia

马来西亚马来亚大学，2006

Student exchange program (学生交流), Singapore

新加坡国立大学 (NUS), 2004ASEAN University Network AUN-NUS Study Award, 2004

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Experience(Non-Research)

知识产权：专利代理人（马来西亚），2013 – 2015

助教（加拿大），2006 – 2013

暑假工作（美国），2006

作者 (兼职) [Pearson；培生教育集团] （马来西亚），2005-2006

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Previous Research in Canada

for ATLAS, LHC at CERN

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Previous Research in Canada(ATLAS, LHC at CERN)

Search for Long-Lived Particles Decay with Displaced Vertices

Difficult search in hadron colliders like ATLAS

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We are proud to say that ATLAS is

the first to publish on such decays in

experimental particle physics.

Publication (1)

Title: Search for long-lived, heavy particles in final states with a

muon and multi-track displaced vertex in proton-proton collisions

at root s=7 TeV with the ATLAS detector

Author(s): The ATLAS Collaboration

Source: Physics Letters B Volume: 719 Issue: 4-5 Pages: 280-

298 Published: 2013

Times Cited: 20

Invented new techniques：

1. Pure fake vertex estimation technique

2. Fake track + material vertex estimation technique

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Brief on one：

Pure fake vertex estimation technique

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Publication（2）

Title: Search for displaced vertices arising from decays of new

heavy particles in 7 TeV pp collisions at ATLAS


Source: Physics Letters B Volume: 707 Issue: 5 Pages: 478-496 Published: 2012

Times Cited: 27

Invented new background estimation technique：

1.

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Data-driven background and distribution

estimation:

Reweighting according to mass and number of

tracks in the control region from two sets of

differently-triggered events

Publication（3）

Title: Search for Supersymmetry in Events with Three Leptons and

Missing Transverse Momentum in root s=7 TeV pp Collisions with

the ATLAS Detector


Source: Physical Review Letters Volume: 108 Issue: 26 Published: 2012

Times Cited: 26

Contribution to another ATLAS physics group with my displaced vertex

expertise：

a. Decay-in-flight muon background study from long-lived hadron decays

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Other works

Unfinished idea from my time in Canada but

documented in my thesis:

CERN-THESIS-2013-33

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Difficult search !

Invented new signal-background discriminators

and proved that it is not difficult.

Research at Nanjing University

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Research at Nanjing U.

(ATLAS upgrade)

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Main tech. candidates for

MiniFCal :

1. Liquid argon

2. Diamond (upgrade

and for the future)

Super Large Hadron

Collider (sLHC)

> 5 X 1034 cm2 s-1

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Benefits of Diamond

High thermal conductivity (No need for

cryostats unlike liquid argon)

High radiation hardness

Low noise

Good charge collection distance

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Degradation curve

Kurchanikov & Cheplakov, 2013

Polycrystalline diamond

Neutrons 1 MeV (Dubna, Russia)

(Canada)

Polycrystalline diamond degrades

faster under neutron irradiation

Single crystal diamond (scCVD) sample

0.6 X 0.6 cm2 size, 300 – 400 microns thick

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Why not substitute polycrystalline with single crystal diamond?

scCVD 2 – 3 times better charge collection distance than polycrystalline diamond.Isberg, et al., 2004, 14th European Conf. on Diamond, Diamond-Like Mat., C. Nanotube, Nitrides and Si.

Carbide

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Plan for Diamond

(Looking Forward)

Monte Carlo (Geant4) simulation within ATLAS

Electrical characterization, e.g.

Irradiation with hadrons (proton, neutron, pion)

Metallization

• Prelim.: Square wafers (1 cm X 1 cm), O(1) mm separation in η and ϕ;

• Test various geometries;

• Irradiation simulation based on experimental results on single wafer;

• Possible front-end electronics and readouts for online-offline mapping,

pulse-shaping.

• Charge collection distance, d;

• d ~ collected charge;

• d depends on radiation damage history of sample.

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Plan B (If things are not as expected)

Still publishable and with patents, if any, e.g.

(权利要求)

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Research at Nanjing U.

(for the Daya Bay experiment)

Cosmic muons interacting with liquid scintillator

can produce 9Li and 8He background mimicking

antineutrino signal.

vs.

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Daya Bay Antineutrino Experiment

Work

Reconstruct muon track with a charge-

weighted coordinate computation:

Lingyu Wang,

DYB-doc # 7838-v9

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Distributions are almost similar for all “symmetric” K-weights.

Charge-weighted method (CWM) for track coordinates can be improved.

Deviation of reco. from truth muon track coord.

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Summary

Self-introduction

Previous work in ATLAS until the shutdown

thereof after Higgs discovery

Future work with ATLAS upgrade and beyond,

and with Daya Bay experiment data analysis

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多谢

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BACKUP

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Charge collection distance = mean distance that electrons and holes drift apart before

Being trapped

26YuenKeung, Hor (2009)

Invented new techniques：

2。Fake track + material vertex estimation

technique

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K-short hadron

mass peak

chung-yao chao fellowship...

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