CEPC Physics at a glance
Manqi Ruan
For the CEPC study group
22/8/2021

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1Known Unknowns of the SM●Inflation●

Mass hierarchy●

Neutrino mass & Oscillation●

Matter anti-matter asymmetry●

Vacuum stabilities: depends on particle mass●

Dark matter, Dark energy: nature & origin of its/their mass●

Naturalness: EW (Higgs mass) V.S. Planck scale●

Flavor Structure: mass & flavor eigenstates●...

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Lomonosov2Known Unknowns of the SM●The Clue:●Inflation●

Mass hierarchy●

Neutrino mass & Oscillation●

Matter anti-matter asymmetry●

Vacuum stabilities: depends on particle mass●

Dark matter, Dark energy: nature & origin of its/their mass●

Naturalness: EW (Higgs mass) V.S. Planck scale●

Flavor Structure: mass & flavor eigenstates●...

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3Key parameters of the CEPC-SPPC●

Tunnel ~ 100 km●

CEPC (90 – 250 GeV)–––●●

Higgs factory: 1M Higgs boson●

Absolute measurements of Higgs boson width and couplings●

Searching for exotic Higgs decay modes (New Physics)

Z & W factory: ~ 1 Tera Z boson●Precision test of the SM●Rare decay

Flavor factory: b, c, tau and QCD studies

SPPC (~ 100 TeV)–

Direct search for new physics–

Complementary Higgs measurements to CEPC g(HHH), g(Htt)–...

Complementary

Heavy ion, e-p collision...

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4Higgs @ CEPC

Observables: Higgs mass, CP, σ(ZH), event rates ( σ(ZH, vvH)*Br(H→X) ), Diff. distributions
Derive: Absolute Higgs width, branching ratios, couplings
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5Timeline

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6CDR released in Nov. 2018●

Baseline designs for the Accelerator, Detector & Software–Subsystems' designs supported with Prototype construction & test

●Physics potential●

Significant international participation (~1/3 authors, very senior & influential IAC support)
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Lomonosov7Baseline Collider Design

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Luminosity/IP（ 1034cm-2s-1 ）Z poleW thresholdHiggs

CDR (2018)31016 - 32

Now

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8Detector & Reconstruction

Starting from the ilcsoft & rewriting all the PFA/high-level reconstruction algorithms.
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9Z→2 muon,
H→2 b~2%Z→2 jet,H→2 tau~5%Z→2 muon
H→WW*→eevv~1%

ZH→4 jets~50%

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10Reconstructed Higgs Signatures

Higgs Signals

Clear Higgs Signature in all SM decay modes
Massive production of the SM background (2 fermion and 4 fermions) at the full Simulation level
Right corner: di-tau mass distribution at qqH events using collinear approximation
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Lomonosov11Model-independent measurement of σ(ZH)
Zhenxing Chen & Yacine Haddad0.9%●

●

1.5%

0.65%

Recoil mass method. Combined
precision:δσ(ZH)/σ(ZH) = 0.5% δg(HZZ)/g(HZZ) = 0.25%
Indirect Access to g(HHH)●

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M. McCullough, 1312.3322
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Higgs benchmark analyses

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Higgs BSM Decay modes

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Measuring Higgs width

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Higgs white paper delivered

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CEPC upgrading option: 360 GeV Run●

2 ab-1 @ 360 GeV●For Higgs●–30% more Higgs events–Higgs width accuracy improves by 2 times (2.8%→1.4%)–...

For Top, For NP...

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EW

With 2 years of Z pole operation (~ 1 Tera Z) and 1 year of W mass scan (~1E7 W)

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EW

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QCD @ CEPC• How to achieve the ultimate precision for alphaS at the CEPC ?
• Can we see gluon spin interference at the CEPC ??
• How to observe entanglement from non-global observables atthe CEPC ???
• Can we quantitatively understand hadronization ????

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Physics @ CEPC●●●

CEPC is not only a high precision Higgs factory, but also a Discovery machine!
–

Boost the Higgs/EW precision by ~ 10 times w.r.t HL-LHC/current boundary–

Huge potential on QCD, Flavor, BSM

Promoting dedicated physics studies,–

To quantify CEPC physics potential with benchmark analyses, and Global interpretation–To guide the design/optimization of the facility & Maximize the physics output: to quantify therequirements on Luminosity, beam quality, & detector performance–Your idea & inputs are more than welcome!

Giving the importance of electron positron Higgs/Z factory, we hope at least one of them (ILC,CLIC, CEPC, FCC) can be realized.

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Back up

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EW interpretation

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Electron Positron Higgs factories
2020

ILC (a):FCC (b):
CEPC (c):CLIC (d):TDR @ 2013
CDR @ 2019
CDR @ 2018
CDR @ 2013

Direct Competition!

Aug 2016, 中国高能物理分会： CEPC 是我国未来加速器首选项目22/8/2021

Lomonosov29Electron Positron Higgs factories

ILC: Prelab proposal released
CERN: significantly invest into the FCC studies...

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Lomonosov30New beam parameters: in progress●●●

Luminosity @ Higgs: increases by 60%(3→5*1034 cm-2s-1/IP) by squeezing thebeam size at IP
Luminosity @ Z: increased by ~4 times(32→115*1034 cm-2s-1/IP) by increasing
bunch charge
Upgrading option: Luminosity @ top ~0.5*1034 cm-2s-1/IP

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Energy Flow in the Collider
High energy beam, SR light, ...

Electricity
Heat

RF WaveHeat废热Klystron (Photon from SNS,ORNL, US)
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RF Cavities (Photon FromILC design)
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SRF Cavity: design goal reached

RF Cavity for both
Booster &Collider ring reaches
Design goal

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High efficiency Klystron
Zusheng, etc

多注速调管三维机械图●●High efficiency prototype (eff~77%) in construction: to be tested within this year!
Multi-beam concept (eff ~ 80.5%): mechanic design finished. Hopefully to be delivered by
the end of 2022.
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IHEP SC Lab @ Huairou: in operation

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Sha Peng, etc

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Iron based high-T super conductingtechnology
Qingjin's team

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CIPC & Candidate sites

The CEPC Industrial Promotion Consortium (CICP) is established inNov 2017.
Till now, ~ 70 companies joined CICP, covering superconductor,superconducting cavities, cryogenics, vacuum, klystron, electronics,
power supply, civil engineering, precise machinery, etc.
The CIPC serves as a communication forum for the industrial and theHEP community.
Candidate sites: Qinghuadao, Huangling, Shenshan, Huzhou,Changchun, Changsha...

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39Better understood detector Performance●

Acceptance: |cos(θ)| < 0.99●

Tracks:●–Pt threshold, ~ 100 MeV–

δp/p ~ o(0.1%)●●

Photons:–

Energy threshold, ~ 100 MeV–

δE/E: 3 – 15%/sqrt(E)

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BMR: 3.7%●

b-tagging: eff*purity @ Z→qq: 70%●

c-tagging: eff*purity @ Z→qq: 40%●

Pi-Kaon separation: 3-sigma (requirement)●Pi-0: eff*purity @ Z→qq > 60% @ 5GeV

●Jet charge: eff*(1-2ω)2 ~ 15%/30% @ Z→bb/cc

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Lepton inside jets: eff*purity @ Z→qq
~ 90% (energy > 3 GeV): slightdegrading in jet
Tau: eff*purity @ WW→tauvqq: 70%,
mis id from jet fragments ~ o(1%)
Reconstruction of simple
combinations: Ks/Lambda/D with all
tracks @ Z→qq: 60/75 – 80/85%
Missing Energy: Consistent with BMR.

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