WG1-PREC “Precision in theory and experiment”

Paolo Azzurri (INFN Pisa), Ayres Freitas (Univ. Pittsburgh), �Adrian Irles (IFIC CSIC/UV), Andreas B. Meyer (DESY)

LUMI Focus topic

• Team members: Ivanka Bozovic (Belgrade), Mogens Dam (Copenhagen), Jenny List (DESY), �Fulvio Piccinini (Pavia), Wiesiek Płaczek (Cracow), Andre Sailer (CERN), Maciej Skrzypek (Cracow), Benny Ward (Baylor), Graham Wilson (Kansas) + WG1-PREC conveners
• Motivation: Luminosity calibration important for total cross-section and lineshape measurements;�precision goal: 10^-4 absolute, 10^-5 point-to-point
• Small-angle Bhabha scattering (SABS):
• Advantages: large rate, well-understood (LEP)
• Challenges: metrology requirements (μm scale), �beam–beam and beam–final-state particle interactions, �beam energy systematics,�hadronic vacuum polarization uncertainty in theory calculation
• Recent work: �▸ updated metrology requirements for ILC (Smiljanic, Bozovic, et al.)�▸ metrology uncertainties at CEPC (Smiljanic, Bozovic, Kacarevic)

LUMI Focus topic

• Di-photon production:
• Advantages: smaller non-perturbative theory effects, no deflection of outgoing photon
• Challenges: smaller rate, large SABS background, few existing MC generators
• Recent work: �▸ high-granularity calorimeter and/or mini-tracker for improvement e+/e- angle measurements and e/γ separation (G. Wilson)
• Longer-term efforts / open questions:
• Improvement to MC generators: BabaYaga (Piccinini et al.), BHWIDE/BHUMI (Placzek, Skrzypek, Ward)
• Explore other processes besides ee → ee, ee → γγ
• Systematic uncertainties for point-to-point lumi calibration

New physics deviations in e+e- → γγ

Possible physics deviations in e+ e-→𝛾𝛾 at the Z pole have a simple and well defined functional form and are relatively easy to control. They can even be “measured” in situ or excluded with previous e+e- runs at larger center-of-mass energies

➜ talk by J. Alcaraz in � WG1-PREC session

PLUG-Cal: Precision Luminosity Ultra-Granular Calo.

➜ talk by G. Wilson in � WG1-PREC session

PLUG-Cal: Precision Luminosity Ultra-Granular Calo.

➜ talk by G. Wilson in � WG1-PREC session

Wmass Focus topic

• Team members: Martin Beneke (Aachen), Stefan Dittmaier (Freiburg), Simon Plaetzer (Graz), Josh Bendavid (MIT), Matthias Schott (Mainz), Raimund Stroehmer (Wurzburg), Graham Wilson (Kansas), Jorge de Blas (Granada) + WG1-PREC conveners
• Motivation: W-mass precision important for SM electroweak precision tests
• WW threshold measurement:
• Advantages: small beam energy uncertainty for ring colliders � (𝛥m_W=0.3-0.4 MeV, 𝛥𝛤_W=1 MeV)
• Challenges: theory description of cross-section, �experimental systematics
• Open questions: �▸ systematic uncertainties (cancellation) in � multi-point cross-section measurement�▸ perform full modern analysis

Wmass Focus topic

• W decay kinematics:
• Advantages: not limited by beam-energy uncertainty at linear colliders, stat. precision of �≲2 MeV possible
• Challenges: sys. uncertainties (energy calibration)
• Recent/ongoing work: �▸ energy calibration using di-lepton and meson � production (G. Wilson)
• Longer-term efforts / open questions:
• Reduction of uncertainties with simultaneous fit to �WW, ZZ, Zγ
• Final-state QCD effects

BCfrag/GSplit Focus topic

• Team members: Martin Beneke (Aachen), Stefan Dittmaier (Freiburg), Simon Plaetzer (Graz), Josh Bendavid (MIT), Matthias Schott (Mainz), Raimund Stroehmer (Wurzburg), Graham Wilson (Kansas), Jorge de Blas (Granada) + WG1-PREC conveners
• b/c-Fragmentation: Insufficient knowledge of fragmentation/hadronization of heavy quarks introduces significant uncertainties (e.g. A_FB(b/c), Higgs BFs, …)
• Are existing hadronization models flexible enough?
• Better understand cross-talk between shower and fragmentation
• Observables to constrain hadronization parameters with higher precision
• Gluon splitting: g→bb/cc introduces additional complication for heavy-flavor tagging
• Consistent implementation in parton-shower tools (in particular non-perturb. part)
• Study target physics observables
• Ongoing work:�▸ Re-study LEP data with modern tools (Gouskos et al.)�▸ Theory/modeling work in context of LHC studies (Plätzer et al.)

➜ talk by L. Gouskos on Wednesday

2f Focus topic

• Team members: Emanuele Bagnaschi, B. L. Ward, Keisho Hidaka, Daniel Jeans, Juergen Reuter, German Rodrigo, Freya Blekman, Eram Rizvi… + WG1-HTE & PREC conveners
• Scope: Understand ee → ff on and off Z pole for precision tests of SM/BSM
• Recent work:�▸ Tagging of (all) parton flavors using ML methods [F. Blekman et al., M. Ruan et al.]�▸ Electroweak couplings of light quarks using FSR [K. Mekala, J. Reuter, et al.]�▸ Det. of tau properties and polarization [D. Jeans, M. Cepeda, D. Garcia]�▸ Using A_FB(b/c) to constrain BSM physics [A. Irles et al.]�▸ Combination of Z-pole and off-pole measurements to separate Z- and 4f-couplings �[E. Bagnaschi et al.]
• Other considerations for report:
• Update on theory calculation (MC tools) requirements?
• Relate new developments to previous state of art (e.g. Snowmass EW)

➜ talk by D. Jeans on Wednesday

➜ talks by M. Cepeda, D. Jeans, K. Mekala in WG1-HTE+PREC session

Probing new physics with two-particle �angular correlations

➜ talk by R. Perez-Ramos� in WG1-PREC session

WG1-PREC work towards Final Report

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• First full draft my mid-November
• Please provide 2-page notes or contact conveners with input by Oct 20�[ecfa-whf-wg1-prec-conveners@cern.ch]

with ➚ WG1-HTE