Indirect probe of electroweak-interacting particles at future lepton colliders

Keisuke Harigaya,Koji Ichikawa,Anirban Kundu,Shigeki Matsumoto,Satoshi Shirai

doi:10.1007/jhep09(2015)105

Abstract

Various types of electroweak-interacting particles, which have non-trivial charges under the $\mathrm{SU}(2)_L \times \mathrm{U}(1)_Y$ gauge symmetry, appear in various extensions of the Standard Model. These particles are good targets of future lepton colliders, such as the International Linear Collider (ILC), the Compact LInear Collider (CLIC) and the Future Circular Collider of electrons and positrons (FCC-ee). An advantage of the experiments is that, even if their beam energies are below the threshold of the production of the new particles, quantum effects of the particles can be detected through high precision measurements. We estimate the capability of future lepton colliders to probe electroweak-interacting particles through the quantum effects, with particular focus on the wino, the Higgsino and the so-called minimal dark matters, and found that a particle whose mass is greater than the beam energy by 100-1000 GeV is detectable by measuring di-fermion production cross sections with $O(0.1)$\% accuracy. In addition, with the use of the same analysis, we also discuss the sensitivity of the future colliders to model independent higher dimensional operators, and found that the cutoff scales corresponding to the operators can be probed up to a few ten TeV.

Highlights

JHEP09(2015)105 color-neutral, hadron colliders are not powerful to search for it due to huge backgrounds, unless the EWIMP gives a very special signature like a massive charged track [17, 36,37,38,39,40,41]
We eventually find that an EWIMP with its mass larger than the beam energy by 100–1000 GeV is detectable depending on its SU(2)L × U(1)Y charges when its differential cross section is measured with O(0.1)% accuracy under a well-polarized beam
We have studied the capability of future lepton colliders, such as the International Linear Collider (ILC), Compact LInear Collider (CLIC) and Future Circular Collider of electrons and positrons (FCC-ee), to probe EWIMPs indirectly

Summary

Direct and indirect collider signatures of an EWIMP

Let us consider an EWIMP of a mass m (> 0) which is an SU(2)L n-tuplet and has a hypercharge of Y. We will observe missing energy plus photons and/or (soft) hadrons and/or massive charged tracks accompanying with the EWIMP production [46].2 In this case, the detail of signatures depends strongly on how the mass of each component of the EWIMP multiplet is distributed, the potential for discovery of the EWIMP in future leptoWn hceonlli√desrsisilsespsrothmainsi2nmg., we can probe indirect effects of the EWIMP on SM processes, while the EWIMP itself cannot be direc√tly produced. As the operators involving two field strength tensors of Wμaν or Bμν become four Fermi-interactions via the equations of motions of the gauge fields, the operators affect the processes e−e+ → f f (with f being the SM f3e0r(m√iso/n1).TTeVh)r1o/u2g(Lh /t1haesbe−1p)r1o/c4eTsseeVs,, the suppression as we will see in scales can be probed the section. We up to Λ2W,2B ∼ expect that these di-fermion production processes will be better to probe the EWIMP indirectly

Corrections to di-fermion production processes

TeV MDM

Analysis method and detector performance

Examples

Summary