Working group report -- cosmology Bi XJ, Chen SL, Gu PH, Shu J, Yin PF, Yu ZH, Zhang XM, Zhou YF (more are welcome) IHEP 2014-2-25

We have clear evidence of new physics from the cosmo frontier: dark mater & matter-anti-matter asymmetry. It has a strong motivation that DM arises from new physics at the TeV scale. EW baryogensis has direct relation with the Higgs sector. Advantage & disadvantage: Guideline from theoretical consideration and from experimental results.

Outline dark matter EW baryogenesis some preliminary results more works in progress EW baryogenesis only research schedule available study is going on

Standard cosmology The cosmological and astrophysical evidence for dark matter is incontrovertible, but its particle origin is completely unknown. When we ask the origin of dark matter in universe, WIMP is the most natural candidate due to WIMP miracle. Dark matter (dark energy) exists in the universe. However, we have to figure out its property.

Thermal history of the WIMP (thermal production) Thermal equilibrium abundance Thermal history of the WIMP (thermal production) At T >> m, At T < m, At T ~ m/22, ，decoupled, relic density is inversely proportional to the interaction strength For the weak scale interaction and mass scale (non-relativistic dark matter particles) , if and WIMP is a natural dark matter candidate giving correct relic density

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

We have simulated the signals and background with a ILD-like detector. Constraints on the Og only at ~300 GeV. Generally weaker than the Fermi gamma-line search sensitivity. Constraints on DM gauge boson interaction are worse than LHC8!

Constraints on the 4-fermion operators @CEPC

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

Simulation of LHC and SPPC (@50TeV) Cuts on LHC is slightly different. Bkg fluctuation is large at high energies.

Constraints on the vector and axial-vector operators by LHC and SPPC

Comparison with the indirect detection by Fermi, CTA and AMS-02 (20yrs)

Comparison with the direct detection of SI and SD exps

Electroweak baryogenesis The matter antimatter asymmetry can be generated dynamically if the Sakharov conditions are satisfied B violation C, CP violation Out of thermal equillibrium the electroweak phase transition provides the 3rd condition if it is strong first order phase transition. EW sphaleron CKM EWPT EWBG refers to any mechanism that produces an asymmetry during the electroweak phase transition.

1st & 2nd phase transition 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 generated baryon asymmetry is kept without washout. The phase transition proceeds when bubbles of the broken phase nucleate and expand within the surrounding symmetric phase.

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 asymmetries All viable realizations of EWBG needs new physics beyond the SM. The new physics must couple to the SM Higgs 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).

1st order phase transition Class1 -- New scalars couple to the Higgs field and modify the Higgs effective potential by running in loops (MSSM) Class 2 -- New scalar fields coupling to the Higgs that develop VEV in the early Universe, which can influence the effective Higgs potential at tree level (NMSSM) Class 3 -- New particles that couple to Higgs field are heavy and induce effective operator at the Higgs potential Those coupling inevitably induce 1, deviation of Higgs potential and its couplings with SM particles 2, mixing with a hidden sector 3, exotic(invisible) decays High precision measurement of Higgs properties are essential to test those scenarios

Class I (MSSM) If X is colored particles (such as stop), to achieve a strongly first-order EWPT requires Q >= 1 and lighter masses mX < 200 GeV . Cohen et al. 2012 The scalars will contribute in loops to the amplitudes for Higgs boson production through gluon fusion and Higgs decay to diphotons. The result is enhancement in gluon fusion production of Higgs and a decrease in the branching fraction to diphotons. Already severely constrained by LHC. Precise measurement of Higgs properties put strong constraint on the model.

Class II (NMSSM) Cubic term is developed at the tree-level potential, which can lead to a strongly 1st EWPT. Usually the decays of h are similar to the SM. We expect exotic Higgs decays in many models of electroweak symmetry breaking, such as the NMSSM. But it is changed significantly if h -> nn is kinematically allowed. This induces possible Higgs Invisible decay or some distinctive channels such as4b, 2b2tau , and 4 tau final states, which has clear signals at CEPC.

Class III For values not too large, 600 GeV<f <1300 GeV, the new sextic term can also drive a strongly first-order electroweak phase transition; TLEP constrain \delta \lambda ~ 30%; LHC 3 ab-1 reach 30 – 50%; (CEPC may also give constraint with smaller luminosity.) ILC TDR

CP violation of EW baryogenesis at the CEPC CP violation term may induce effective anomalous Higgs coupling to 3rd generation fermion or gauge bosons. We intend to check the anomalous coupling to constrain the scenario of EW baryogensis. Zhang et al. 1993

Bicer et al. 1308.6176

Summary DM search at CEPC has little advantage. Study on DM @ SPPC is preliminary. More study (SUSYs, minimal …) is in progress EW baryogenesis is testable at the CEPC. Works are under way.