Physics at future e+e- colliders:ARIEL project

L.V. Kalinovskaya, I.R. Boyko(DLNP)

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Future collider candidates

• ILC: 20-30 km, 250-500 GeV, Higgs factory (Giga-Z possible)

• CLIC: 50 km, 3000 GeV, Higgs, Top, discoveries

• CEPC: 100 km, 250 GeV, Higgs physics + Giga-Z

• FCC: 100 km, 350 GeV, Higgs + Tera-Z

• HL LHC: 14 TeV, 3 ab-1

• HE-LHC: 33 TeV, 2 ab-1

• CEPC-pp: 70 TeV, 10 ab-1

• FCC-pp: 100 TeV, 5 ab-1

Electron-positron Proton-proton

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ILC (2030) CLIC (2035)

CEPC (2030) FCC-ee (2039)

$ 4-5G$ 6.7G (380 GeV)+$6G (3000 GeV)

$ 5.5G $ 12G

Future e+e- colliders

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Comparison of e+e- projects

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Energy milestones of e+e- colliders

• 91 GeV: repeat LEP1 experiments– “Tera-Z”: full LEP1 data every 5 min!!!– Statistics 1 million x LEP experiment

• 161 GeV: E=2xMW, threshold scan– repeat 1996 at LEP2, 1000x lumi

• 240-250 GeV: Higgs factory• 350 GeV: E=2xMt, threshold scan• 400 GeV: maximum top-pair cross-section• 500-3000 GeV: discovery of new physics!

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Reaching ultimate precision• Statistical error

– Increase collider luminosity• Systematic error

– Novel detector technologies – Improved analysis methods

• Theoretical error– More precise calculations – Higher perturbative order – Include polarization

• Parametric error– Better measurement of external parameters

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This seminar content:

• Experimental program of future colliders– I.Boyko

• Precision theoretical calculations for the future colliders– L.Kalinovskaya

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Measurement of the electron size at 3 TeV CLIC run

• In Standard Model, the fundamental particles are assumed to be point-like

• Finite particle size distorts the SM predictions• The reaction most sensitive

to the electron size is ee→γγ• Both total and differential cross-section are

sensitive to electron size and to other BSM models

• The sensitivity is dramatically improved at high energy – 3000 GeV at CLIC!

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ee→γγ with CLIC full simulation• A fit to the differential cross-section has

been performed• 4 different BSM models considered• Systematic errors from background,

tracking, luminosity have been evaluated• Improvement of LEP results by a factor 15

is expected at CLIC

ee→γγee→ee

eγ→eγ

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Higgs boson mass measurement at 380 GeV CLIC running

• Higgs boson mass is the fundamental SM parameter. Its precision contributes a significant parametric uncertainty to the theoretical calculations

• At CLIC the best MH precision is reached in the reaction ee→ZH→μμbb at 380 GeV running

• Muons from Z decay are fully reconstructed; for the b-jets only directions (but not energies) must be measured

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MH with CLIC full simulation

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2020 Update of the EuropeanStrategy for Particle Physics

• FCC is preferred mostly due to its possible FCC-hh continuation

• “Feasibility” must be demonstrated by FCC in the coming years

• CLIC remains as a “spare option”

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Participation in the CEPC project

• JINR team remains a member of the CLIC collaboration

• However, given the ECFA recommendations, we are looking for possible diversification of our activity

• Recently we have joined the CEPC project (a proto-collaboration, being formed right now)

• We have studied the CEPC potential in the physics of gamma-gamma collisions

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γγ collisions at CEPC• Every e+e- collider is

simultaneously a γγcollider

• Events γγ→anythingrepresent an important background to the annihilation, but they also provide an interesting physics

• At CEPC several fb-1 will be collected at collision energy above 100 GeV

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Photoproduction of Higgs boson γγ→H

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Anomalous magnetic moment of tau lepton

• Magnetic moment is known at precision 10-12 (electron), 10-9

(muon), 10-2 (tau)• The cross-section of γγ→ττ

depends linearly on tau magnetic moment

• The easiest channel is γγ→ττ → eμ

• We estimated that 700K events can be selected at CEPC.

• Systematic error will dominate. A preliminary analysis gives 10-2

precision on tau magnetic moment (order of magnitude improvement)

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Summary on experimental program

• JINR group actively participates in preparation of CLIC experimental program

• Our results have been included in “Yellow book on New Physics at CLIC” and presented at several conferences

• Given the ESPP decision, we have also joined to the CEPC project, in addition to the participation in CLIC

• Our CEPC studies are submitted as a chapter in the “White book of CEPC physics program”