SMU Physics Department Speaker Series: Dr. Keping Xie (University of Pittsburgh)
Channel: Stephen Sekula
Date: 2022-04-26

The recent breakthrough in the muon beam cooling technology make a multi-TeV muon collider feasible in the future. Compared with a hadron or electron collider, a muon collider embraces advantages of both a high effective energy reach and a clean environment. Our recently studies suggest that the physics at a high-energy muon collider can be treated in a factorization picture. At an energy well above the electroweak scale, the collinear splitting phenomena dominate due to the large logarithm enhancement both in the initial and final state radiations. All the Standard Model particles, including electroweak gauge bosons, essentially become massless, and the electroweak gauge symmetry is gradually restored. With the Dokshitzer-Gribov-Lipatov-Altarelli-Parisi (DGLAP) formalism, we resum large logarithms in the initial state radiations as electroweak parton distribution functions (EW PDFs). The final state radiations should be treated similarly with fragmentation functions. We present several semi-inclusive cross sections as standard candles for the Standard Model processes at a high-energy muon collider. Besides the Standard Model phyiscs, a high-energy muon collider is also an ideal machine to search new physics. We take the muon-Higgs coupling as an example, which can receive new contribution beyond the Standard Model. To be model-independent, we parameterize new physics with linear Standard Model effective theory (SMEFT) or a non-linear Higgs effective field theory (HEFT). We found that, due to the anomalous muon-Higgs coupling, multi-boson production at a high-energy muon collider can significantly deviate from the Standard Model expectation, which provides us a great chance to either discover new physics or test the Standard Model at a high precision.