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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

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, 2009Graduate 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 CollaborationSource: 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

Author(s): The ATLAS Collaboration 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

Author(s): The ATLAS Collaboration 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 argon2. 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) sample0.6 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

21Distributions 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)

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Invented new techniques ：

2 。 Fake track + material vertex estimation technique

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K-short hadron mass peak