Subjects: Physics >> The Physics of Elementary Particles and Fields submitted time 2016-06-28
Abstract： We consider the Higgs portal through which light scalars contribute both to the Higgs production and decay and Higgs effective potential at finite temperature via quantum loops. The positive Higgs portal coupling required by a strongly first order electroweak phase transition is disfavored by the current Higgs data if we consider one such scalar. We observe that by introducing a second scalar with negative Higgs portal coupling, one can not only improve the Higgs fits, but also enhance the strength of first order EWPT. We apply this mechanism to the light stop scenario for electroweak baryogenesis in the MSSM and find a light sbottom could play the role as the second scalar, which allows the stop to be relatively heavier. Non-decoupled effects on the Higgs or sbottom self-interactions from physics beyond MSSM are found to be indispensable for this scenario to work. A clear prediction from the picture is the existence of a light sbottom (below 200 GeV) and a light stop (can be as heavy as 140 GeV), which can be directly tested in the near future.
Peer Review Status:
Awaiting Review
Subjects: Physics >> The Physics of Elementary Particles and Fields submitted time 2016-06-27
Abstract： We study Higgs diphoton decays, in which both photons undergo nuclear conversion to electron-positron pairs. The kinematic distribution of the two electron-positron pairs may be used to probe the CP violating (CPV) coupling of the Higgs to photons, that may be produced by new physics. Detecting CPV in this manner requires interference between the spin-polarized helicity amplitudes for both conversions. We derive leading order, analytic forms for these amplitudes. In turn, we obtain compact, leading-order expressions for the full process rate. While performing experiments involving photon conversions may be challenging, we use the results of our analysis to construct experimental cuts on certain observables that may enhance sensitivity to CPV. We show that there exist regions of phase space on which sensitivity to CPV is of order unity. The statistical sensitivity of these cuts are verified numerically, using dedicated Monte-Carlo simulations.
Peer Review Status:Awaiting Review
Subjects: Physics submitted time 2016-05-08
Abstract： Using finite-size scaling, we have investigated the percolation phase transitions of evolving random networks under a generalized Achlioptas process (GAP). During this GAP, the edge with a minimum product of two connecting cluster sizes is taken with a probability p from two randomly chosen edges. This model becomes the Erdos-Renyi network at p = 0.5 and the random network under the Achlioptas process at p = 1. Using both the fixed point of the size ratio s(2)/s(1) and the straight line of ln s(1), where s(1) and s(2) are the reduced sizes of the largest and the second-largest cluster, we demonstrate that the phase transitions of this model are continuous for 0.5 <= p <= 1. From the slopes of ln s(1) and ln(s(2)/s(1))' at the critical point, we get critical exponents beta and upsilon of the phase transitions. At 0.5 <= p <= 0.8, it is found that beta, upsilon and s(2)/s(1) at critical point are unchanged and the phase transitions belong to the same universality class. When p >= 0.9, beta, upsilon, and s(2)/s(1) at critical point vary with p and the universality class of phase transitions depends on p.
Peer Review Status:Awaiting Review
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