CEPC Flavor Physics Discussion

Thursday 8 Dec 2022, 10:30 → 12:30 Asia/Shanghai

Overleaf link of CEPC Flavor White Paper for co-editing:
https://www.overleaf.com/6544624919ndzjrvxdcbzb

Relevant documents (e.g. minutes, slides, references...) can be found at:
https://docs.ihep.ac.cn/link/AAB56818007D3A46D8839ABDB81124C410

Zoom link:
Topic 主题: CEPC Flavor White Paper Discussion
Meeting ID 会议号: 83278870513
Begin Time 开始时间: 2022-12-08T 10:30:00
Duration 持续时长: 150 minutes
Meeting URL 会议链接:: https://ihep-ac-cn.zoom.us/j/83278870513?pwd=UDZGR0R5NG9uc1VaNVNhbDZMd1B0UT09
Password 会议密码: 819418
H323 接入IP: 221.122.88.195
Resource ID 资源号: video10@zoomrooms.cn
Timezone 时区: Asia/Shanghai

Minutes for CEPC Flavor White Paper Discussion

Date: 2022.12.08 10:30-12:00 (Beijing time)

Participants (12): Tao Liu, Lorenzo, Liming Zhang, Lingfeng Li, Anson, Yingying Li, Xuai Zhuang, Manqi Ruan, Hao Liang, Hanhua Cui, Yongfeng Zhu, Yuexin Wang

Indico page: https://indico.ihep.ac.cn/event/18498/

 

Talk by Hao: Measurement of Vcb from W→μνqq

• Need further comparison with FCC (the fundamental difference?)
  • Signal efficiency & purity
  • Full simulation results
  • Assumption of flavor tagging
  • Luminosity, etc.
• Anticipated precision of Vcb should at 1% level
  • Ref. https://arxiv.org/pdf/2006.04824.pdf
• Possibility to measure Vcb via full hadronic decay?
  • May provide additional information, but challenging (e.g. jet confusion)
  • Corresponding accuracy unlikely overwhelms the semileptonic one (which is much easier to handle)
• Using information at event level instead of jet level analysis
  • We always lose some message at jet level analysis
  • Hao proposes to use neural network with particle level information as inputs
    • Using truth level particles as first step
• Flavor tagging efficiency should be a function, instead of using the average efficiency
  • Dependence on the jet energy/P_T/polar angle, etc.
• Efficiency of W→cb different from that of W→c(s/d) or W→u(s/d)
  • Possible reason: the missing P_T cut or the MC uncertainty?
  • The missing P_T cut may cause systematics

Talk by Hanhua: Jet charge measurement at CEPC

• To further understand the fragmentation method of different generators
  • The only difference of different generators is the hadronization and the parton shower
• To quantify the possible correlation induced by hard gluon emission
  • Look into the dependence on some jet shape parameters (like thrust, Y23, etc.)
• Also plan to look into the dependence of jet charge performance on the E_CM
• Muon has the biggest difference
  • Maybe hadron decay should be taken into account
  • b cascading
• Benchmark applications
  • All CP violation related measurements
  • Some new physics may be also sensitive to the jet charge
• Current two methods (Leading Particle & Weighted Charge)
  • Weighted Charge: the traditional one, dominate the b-performance
  • Leading Particle: only use one dimensional information
  • Suggest to explore other more methods to include more information (like 2^nd/3^rd vertex), all the LEP methods can be a good reference to start with
  • Worry about correlations between multiple methods when combining them
    • Suggest at least 3 subcategories (B0, Bs, Λb, only the neutral ones need to be tagged)

1 Measurement of Vcb via W->cb

Speakers: Hao Liang, Yongfeng Zhu

Measurement of Vcb from W→μνqq.pdf

2 Jet Charge Measurement

Speaker: Hanhua CUI

Jet_Charge_Cuihh_20221208.pdf