Implications of the 750 GeV γγ Resonance as a Case Study for the International Linear Collider

If the γγ resonance at 750 GeV suggested by 2015 LHC data turns out to be a real effect, what are the implications for the physics case and upgrade path of the International Linear Collider? Whether or not the resonance is confirmed, this question provides an interesting case study testing the robustness of the ILC physics case. In this note, we address this question with two points: (1) Almost all models proposed for the new 750 GeV particle require additional new particles with electroweak couplings. The key elements of the 500 GeV ILC physics program—precision measurements of the Higgs boson, the top quark, and 4-fermion interactions— will powerfully discriminate among these models. This information will be important in conjunction with new LHC data, or alone, if the new particles accompanying the 750 GeV resonance are beyond the mass reach of the LHC. (2) Over a longer term, the energy upgrade of the ILC to 1 TeV already discussed in the ILC TDR will enable experiments in γγ and e+e− collisions to directly produce and study the 750 GeV particle from these unique initial states. ar X iv :1 60 7. 03 82 9v 2 [ he pph ] 3 1 Ju l 2 01 6 1 High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki, JAPAN 2 DESY, Notkestrasse 85, 22607 Hamburg, GERMANY 3 ICREA at IFAE, Univesitat Autónoma de Barcelona, E-08193 Bellaterra, SPAIN 4 SLAC, Stanford University, Menlo Park, CA 94025, USA 5 Center for High Energy Physics, Tsinghua University, Beijing, CHINA 6 Department of Physics, University of Toyama, Toyama 930-8555, JAPAN 7 Department of Physics and Astronomy, Seoul National University, Seoul 151-747, KOREA 8 Kavli Institute for the Physics and Mathematics of the Universe, University of Tokyo, Kashiwa 277-8583, JAPAN 9 Laboratory for Elementary Particle Physics, Cornell University, Ithaca, NY 14853, USA 10 LAL, Centre Scientifique d’Orsay, Université Paris-Sud, F-91898 Orsay CEDEX, FRANCE 11 Max-Planck-Institut für Physik, Föhringer Ring 6, 80805 Munich, GERMANY 12 ICEPP, University of Tokyo, Hongo, Bunkyo-ku, Tokyo, 113-0033, JAPAN 13 Department of Physics, University of Texas, Arlington, TX 76019, USA 14 Michigan Center for Theoretical Physics, University of Michigan, Ann Arbor, MI 48109, USA 15 LPT, Université Paris-Sud, 91405 Orsay, FRANCE 16 Department of Physics, University of Tokyo, Tokyo 113-0033, JAPAN 17 IFIC (UVEG/CSIC), Edificios de Investigacion, c./ Catedratico Jose Beltran 2, E-46980 Paterna, Valencia, SPAIN 18 Quantum Universe Center, KIAS, Seoul 02455, KOREA 19 Department of Physics, University of California, Berkeley, CA 94720, USA 20 Theoretical Physics Group, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA 21 Department of Physics, Tohoku University, Sendai, Miyagi 980-8578, JAPAN