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Nomenclature

• LLCP: HSCP and in-flight decay particles
• HSCP: ~stable until muon chambers
• in-flight decay particles
  • disappearing track: e.g., $\tilde W^+\to \tilde W^0 + \pi$ and $\pi$ is too soft to be reconstructed
  • kink track: e.g., $\tilde e^- \to e^- + \tilde B$ and $e^-$ is hard enough. Possibly reconstructed as disappearing track signature if the secondary track is lost.
  • non-pointing photon: e.g., $\tilde B \to \tilde G + \gamma$, where $\gamma$ is hard.
  • displaced vertex: e.g., $\tilde W^0 \to l^+l^- + \tilde B$, where leptons are hard.

FCC-he

$\sqrt s = \sqrt{2(60\GeV)(50\TeV)} = 3.5\TeV$; pair production up to 1.7 TeV.

Possible models

Theory-motivated

• Wino LSP $W^+\to W^0 + \pi$
  • $c\tau=(11,8,7,6)\cm$ for $(100, 150, 200, \infty)$-Wino if the other SUSY particles are decoupled.
  • DM underabundant (if thermal and $m_{\tilde W} < 3\TeV$).
• Higgsino LSP
  • mass splitting ~355 MeV [9804359,0512090].
  • DM underabundant (if thermal and $m_{\tilde H}<1\TeV$).
• Bino-Higgsino LSP
  • but decay length would be too short?
• Slepton-Bino degeneracy
  • DM overabundant (or co-annihilation)
• Stau-Higgsino degeneracy
  • DM underabundant
  • For slepton it is difficult to close the phase space; small Yukawa will not help.

$pp$-collider expectation

• HSCP will be covered upto 1.1 TeV (3 TeV) $\tilde l\w R$ at HL-LHC (FCC-hh) [1505.02996].
• Monojet: up to 250 GeV (1 TeV) $\tilde W^0$ (maybe $\tilde W^\pm$ generated?), 100 (500) GeV $\tilde H^0$ [1404.0682].
• Disappearing: up to 150 GeV (2TeV) $\tilde W^\pm$, 100 (500) GeV $\tilde H^\pm$ [1404.0682] (using 100% efficiency for $30<c\tau/\mathrm{cm}<80$).

Strength of $ep$ collider

• selectron will be produced more efficiently through the process $ep\to\tilde e \tilde \chi j$

Sho’s TODOs

• Calculate production cross sections for each of above (motivated) theories
• Especially selectron case is interesting; firstly compare it with FCC-hh.

Scrap ideas

• in EP collider, the boost of the system is related to the total energy of the system? i.e., We might tell initial parton momenta $p_q$ if we measure $\sum\w{final} p^\mu$ ?