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All Results

On the Higgs fit and electroweak phase transition

Huang, Weicong; Shu, Jing; Zhang, YueSubjects: Physics >> The Physics of Elementary Particles and Fields

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. |

Subjects: Physics >> The Physics of Elementary Particles and Fields

After the discovery of a standard model (SM)-like Higgs boson, naturalness strongly favors the next-to-minimal supersymmetric SM. In this letter, we point out that the natural next-to-minimal supersymmetric SM usually predicts the following CP-even Higgs H-i sector: (A) H-2 is the SM-like Higgs boson with mass pushed upward by a lighter H-1 with mass overwhelmingly within [m(H2)/2, m(H2)]; (B) m(H3) similar or equal to 2 mu/sin 2 beta greater than or similar to 300 GeV; (C) H-3 has a significant coupling to the top quark and can decay to H1H2 with a large branching ratio. Using a jet substructure we show that these three Higgs bosons can be discovered via gg -> H-3 -> H1H2 -> b (b) over barl nu jj at the 14 TeV LHC. In particular, the LEP-LHC scenario with H-1 similar or equal to 98 GeV has a very good discovery potential. |

Impact of a CP-Violating Higgs Sector: From LHC to Baryogenesis

Shu, Jing; Zhang, YueSubjects: Physics >> The Physics of Elementary Particles and Fields

We observe a generic connection between LHC Higgs data and electroweak baryogenesis: the particle that contributes to the CP-odd hgg or h gamma gamma vertex would provide the CP-violating source during a first-order phase transition. It is illustrated in the two Higgs doublet model that a common complex phase controls the lightest Higgs properties at the LHC, electric dipole moments, and the CP-violating source for electroweak baryogenesis. We perform a general parametrization of Higgs effective couplings and a global fit to the LHC Higgs data. Current LHC measurements prefer a nonzero phase for tan beta less than or similar to 1 and electric dipole moment constraints still allow an order-one phase for tan beta similar to 1, which gives sufficient room to generate the correct cosmic baryon asymmetry. We also give some prospects in the direct measurements of CP violation in the Higgs sector at the LHC. |

Towards the fate of natural composite Higgs model through single t ' search at the 8 TeV LHC

Li, Jinmian; Liu, Da; Shu, JingSubjects: Physics >> The Physics of Elementary Particles and Fields

We analyze the observational potential of single t' production in both the t' -> bW and t' -> th decay channels at 8 TeV LHC using an integrated luminosity of 25 fb(-1). Our analysis is based on a simplified model with minimal coset SO(5)/SO(4) in which the t' is a singlet of the unbroken SO(4). The single t' production, as a consequence of electroweak symmetry breaking, is less kinematically suppressed, associated with a light forward jet and has boosted decay products at the 8 TeV LHC. Therefore it provides the most promising channel in searching for a heavy t'. We have exploited the above kinematical features and used the jet substructure method to reconstruct the boosted Higgs in th decay channel. It is shown that a strong constraint on the t'bW coupling (g(t'bW)/g(tbW,SM) < 0.2 similar to 0.3) at the 95% C. L. can be obtained for m(t') subset of (700, 1000) GeV. |

Probing CP violation in h -> gamma gamma with converted photons

Bishara, Fady; Grossman, Yuval; Harnik, Roni; Robinson, Dean J.; Shu, Jing; Zupan, JureSubjects: Physics >> The Physics of Elementary Particles and Fields

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. |

New insights in the electroweak phase transition in the NMSSM

Huang, Weicong; Kang, Zhaofeng; Shu, Jing; Wu, Peiwen; Yang, Jin MinSubjects: Physics >> The Physics of Elementary Particles and Fields

We perform a detailed semianalytical analysis of the electroweak phase transition (EWPT) property in the Next-to-Minimal Supersymmetric standard model, which serves as a good benchmark model in which the 126 GeV Higgs mixes with a singlet. In this case, a strongly first-order electroweak phase transition (SFOEWPT) is achieved by the tree-level effects, and the phase transition strength gamma(c) is determined by the vacua energy gap at T = 0. We make an anatomy of the energy gap at both tree level and loop level and extract out a dimensionless phase transition parameter R-kappa equivalent to 4 kappa v(s)/A(kappa), which can replace A(kappa) in the parameterization and affect the light CP-odd/even Higgs spectra. We find that SFOEWPT only occurs in R-kappa similar to -1 and positive R-kappa less than or similar to O(10), which in the non-PQ limit case would prefer either a relatively light CP-odd or CP-even Higgs boson similar to(60, 100) GeV, and therefore serves as a smoking gun signal and requires new search strategies at the LHC. |

Two component dark matter with multi-Higgs portals

Bian, Ligong; Li, Tianjun; Shu, Jing; Wang, Xiao-ChuanSubjects: Physics >> The Physics of Elementary Particles and Fields

With the assistance of two extra groups, i.e., an extra hidden gauge group SU(2)(D) and a global U(1) group, we propose a two component dark matter (DM) model. After the symmetry SU(2)(D) x U(1) being broken, we obtain both the vector and scalar DM candidates. The two DM candidates communicate with the standard model (SM) via three Higgs as multi-Higgs portals. The three Higgs are mixing states of the SM Higgs, the Higgs of the hidden sector and real part of a supplement complex scalar singlet. We study relic density and direct detection of DM in three scenarios. The resonance behaviors and interplay between the two component DM candidates are represented through investigating of the relic density in the parameter spaces of the two DMs masses. The electroweak precision parameters constrains the two Higgs portals couplings (lambda(m) and delta(2)). The relevant vacuum stability and naturalness problem in the parameter space of lambda(m) and delta(2) are studied as well. The model could alleviate these two problems in some parameter spaces under the constraints of electroweak precision observables and Higgs indirect search. |

Quantum effects in thermal Fock state for mesoscopic left-handed transmission lines

S.C. ZhaoSubjects: Physics >> Electromagnetism, Optics, Acoustics, Heat Transfer, Classical Mechanics, and Fluid Dynamics

Subjects: Physics >> General Physics: Statistical and Quantum Mechanics, Quantum Information, etc.

A quantization scheme for an ideal loss-less mesoscopic left-handed transmission lines (LH TL) unit cell equivalent circuit is proposed and the fluctuations of the current and the voltage of the LH TL equivalent circuit in thermal Fock space are studied by thermal field dynamics (TFD) theory. In thermal Fock state the negative refractive index (NRI) of the LH TL unit cell equivalent circuit is discussed. The results indicate that the quantum fluctuations show the linear dependent of NRI at some temperature, while the frequency and the thermal photons are destructive dependent of NRI within the microwave frequency band. When the unit cell equivalent circuit operates at the rising temperature, the NRI is decreasing. The results demonstrates the ideal loss-less mesoscopic LH TL equivalent circuit operating at a lower frequency, temperature and with little thermal photons is more conducive to NRI, which coincides with the macroscopic real LH TL. |

submitted time
2016-06-26
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Interpretation of the Galactic Center excess and electroweak phase transition in the NMSSM

Bi, Xiao-Jun; Bian, Ligong; Huang, Weicong; Shu, Jing; Yin, Peng-FeiSubjects: Physics >> The Physics of Elementary Particles and Fields

The gamma-ray excess observed by the Fermi-LAT in the Galactic Center can be interpreted by the dark matter annihilation to b (b) over bar via a light pseudoscalar in the next-to-minimal supersymmetric standard model (NMSSM). It is interesting to note that the corresponding singlet scalar is useful to achieve a strongly first-order phase transition required by the electroweak baryogenesis. In this paper, we investigate the possibility that the NMSSM model can simultaneously accommodate these two issues. The phase transition strength can be characterized by the vacua energy gap at zero temperature and be sufficiently enhanced by the tree-level effect in the NMSSM. We find that the annihilation of singlino/Higgsino dark matter (DM) particles occurring close to the light pseudoscalar resonance is favored by the Galactic Center excess and the observed DM relic density, and some resulting regions in the parameter space with a small kappa/lambda. and a negative A. can simultaneously account for a successful strongly first-order electroweak phase transition. |

Subjects: Physics >> The Physics of Elementary Particles and Fields

We present a class of cancellation conditions for suppressing the total contributions of Barr-Zee diagrams to the electron electric dipole moment (eEDM). Such a cancellation is of particular significance after the new eEDM upper limit was released by the ACME Collaboration, which strongly constrains the allowed magnitude of CP violation in Higgs couplings and hence the feasibility of electroweak baryogenesis (EWBG). Explicitly, if both the CP-odd Higgs-photon-photon (Z boson) and the CP-odd Higgs-electron-positron couplings are turned on, a cancellation may occur either between the contributions of a CP-mixing Higgs boson, with the other Higgs bosons being decoupled, or between the contributions of CP-even and CP-odd Higgs bosons. With a cancellation, large CP violation in the Higgs sector is still allowed, yielding successful EWBG. The reopened parameter regions would be probed by future neutron, mercury EDM measurements, and direct measurements of Higgs CP properties at the Large Hadron Collider Run II and future colliders. |