1. Hidden sector effects on double Higgs production near threshold Rogerio Rosenfeld Rogerio Rosenfeld Instituto de Física Teórica Instituto de Física Teórica UNESP UNESP VIII Simpósio Latinoamericano de Física de Altas Energias SILAFAE 2010 – Valparaíso – Chile Work done with Alexandra Oliveira ( arXiv:1009.4497) Dedicated to the memory of Olivier Espinosa

2. Idea: many BSM models with new interactions in the Higgs sector: “Higgs portal” new interactions in the Higgs sector could lead to enhancements in Higgs pair production near threshold (light Higgs has weak self-interactions) H-H bound states ( Higgsium, Grinstein and Trott 07) gluon distribution functions are largest near threshold.

3. ... Idea: Effective ggHH vertex Plehn, Spira and Zerwas (96) new scalar particle Possible enhancement in Higgs pair production near threshold due to new physics:

4. Analogous to Sommerfeld enhancements invoked in annihilation of DM particles and similar to QCD corrections to top quark pair production near threshold: Fadin and Khoze(87) Fadin, Khoze and Sjostrand (90) Strassler and Peskin (91) Hagiwara, Sumino and Yokoya (08)

5. Toy model: Use optical theorem to find correction to the cross section: is the amplitude for gg scattering via a higgs loop. Goal: compute this amplitude in the nonrelativistic limit including contributions from the hidden sector.

6. Summing up ladder diagrams: Integral Bethe-Salpeter equation:

7. Complete scattering amplitude

8. Nonrelativistic approximation (after Fourier transform) results in a Schroedinger-like equation: Solve equation numerically.

9. Enhancement of the cross section:

10. Enhancement depends on: “strength of new interaction” Solid line: SM  = 0.01, 0.1, 0.3

11. Solid line: SM  = 0.1, 0.7 and 1 Large enhancements for large couplings: Peaks are due to HH bound states below threshold

12. Conclusions Initial study on the enhancement of Higgs pair production near threshold due to new physics in Higgs sector; Enhancement occurs for strong couplings; Simplest model with an extra scalar field does not lead to enhancements because of mixing: Signal: excess of 4 gauge bosons production below Higgs pair threshold (small background)

13. ICTP-South American Institute for Fundamental Research November 8 Agreement between the State University of São Paulo (UNESP) and ICTP: new institute will be hosted by IFT-UNESP UNESP will hire 5 researchers in 5 years (light teaching load) selected by an international scientific committee and 3 administrative staff ICTP will help in organizing events and raising funds