Cosmology study at CEPC/SppC on behalf of the TeV cosmology working group Bi Xiao-Jun (IHEP) 2015-8-11

Outline EW baryogenesis Dark matter

After the discovery of Higgs the next question is what is the shape of the Higgs potential. The EW phase transition is first order or second order? Strongly 1st order phase transition is motivated by the EW baryogenesis. Why only baryons exist in the universe? An attractive idea is that baryon asymmetry is generated during the electroweak phase transition, EW baryogenesis. The physics is at EW scale and testable at the colliders.

1st & 2nd phase transition - EWBG Some time after the temperature falls below Tc, regions of the cosmological plasma tunnel to the deeper broken minimum and the phase transition proceeds by the nucleation of bubbles. It is during this phase transition that EWBG takes place. Successful EWBG requires a strongly first-order electroweak phase transition. The 1st phase transition proceeds when bubbles of the broken phase nucleate and expand within the surrounding symmetric phase. CP violating interaction generate baryon number. The generated baryon asymmetry is kept without washout only IF 1st order PT.

Test the EWPT is one of the primary goals of CEPC. SM electroweak phase transition is first-order only if the mass of the Higgs boson m_h <75 GeV Even if the phase transition is first order, the CP violation by CKM phase is not large enough to generate sufficient B asymmetries All viable realizations of EWBG needs new physics beyond the SM. The new physics must couple to the SM Higgs quite strongly and new particle masses not too far above the electroweak scale. A generic prediction of EWBG is that new phenomena should be discovered (severely constrained) at LHC-HL, CEPC (SPPC). Test the EWPT is one of the primary goals of CEPC.

At the level of renormalizable operators, a broad range of possibilities for SFOEWPT are embodied in the Higgs portal interaction Φ: singlet or charged under SM SU(2)L*U(1)Y represent generic features of full theory (NMSSM, GUTs ….) Novel feature of SSB

Simplest case: singlets Two Higgs-like mixing states Modified SM Higgs self-coupling Reduce the SM Higgs signal strength Resonant di-Higgs production Exotic Higgs decays Tree level barrier

Modified Higgs self-coupling S. Profumo et al. 1407.5342 Modified Higgs self-coupling Higgs self-coupling g111 is closely correlated with critical temperature Tc g111 covers from nearly 0 to 60, with SM g111 is ~30GeV CEPC sensitivity is about 30%. CEPC HL-LHC SPPC

Higgs-singlet mixing angle S. Profumo et al. 1407.5342 Black points are viable models to achieve strongly 1st order PT and satisfy all the EW precision constraints CEPC constrains most models

Non-singlet scalars: triplet Baryogenesis at T1 B preserved at T2 H-> γγ is modified by new charged particle CEPC at 5% Two step PT

Non-renormalizable operators For values not too large, 600 GeV<f <1300 GeV, the new sextic term can also drive a strongly first-order electroweak phase transition; CEPC constrain \delta \lambda ~ 30%; LHC 3 ab-1 reach 30 – 50%; ILC TDR

A nightmare scenario: Z2 symmetry singlet S 1st PT S is stable and no mixing with Higgs. The direct signal at colliders is miss energy. Self coupling shift; 30% for CEPC ZH coupling shift; 0.4% for CEPC D. Curtin et al., 1409.0005

Constrain the effective interaction @ CEPC Bi, Yin, Yu, Yuan We have given an study to constrain the interaction between DM and SM particle with effective operators. Operators: Signals: mono-gamma, mono-Z

Constraints on the 4-fermion operators @CEPC

Comparison with the sensitivities of indirect DM detection by Fermi, AMS-02

Simulation of SppC sensitivity of DM search via a simplified Z’ model Estimated 90% C.L. limits in the mχ-gq plane for the monojet+ / ET channel at the SppC with √s = 50 TeV (blue lines) and 100 TeV (red lines), assuming an integrated luminosity of 3 ab−1.

Comparison of sensitivity by SppC and direct DM detection exps

Comparison of sensitivity of SppC and indirect DM exps

Simplified SU(2) mutltiplets (SUSY) by LT Wang

Higgsino (monojet)

Summary EW baryogenesis requires new physics at the EW scale to realize 1st order PT. It is found that most cases can be tested at CEPC. Together with SppC nearly all the scenarios are covered. Dark matter search is promising at SppC.