Theory and phenomenology of two-Higgs-doublet models

http://www-com.physik.hu-berlin.de/~fjeger/gm2review.pdf

The muon g ― 2

Generalized parton distributions

QCD factorization for B→PP and B→PV decays

Weakly Interacting Massive Particles (WIMPs) are among the best-motivated dark matter candidates. No conclusive signal, despite an extensive search program that combines, often in a complementary way, direct, indirect, and collider probes, has been detected so far. This situation might change in near future due to the advent of one/multi-TON Direct Detection experiments. We thus, find it timely to provide a review of the WIMP paradigm with focus on a few models which can be probed at best by these facilities. Collider and Indirect Detection, nevertheless, will not be neglected when they represent a complementary probe.

/pdf/the-waning-of-the-wimp-a-review-of-models-searches-and-2nu358qery.pdf

The waning of the WIMP? A review of models, searches, and constraints

Excesses of muon g − 2, RD(⁎), and RK(⁎) in a leptoquark model

ATLAS and CMS recently show the first results from run 2 of the Large Hadron Collider (LHC) at $\sqrt{s}=13$ TeV. A resonant bump at a mass of around 750 GeV in the diphoton invariant mass spectrum is indicated and the corresponding diphoton production cross section is around 3-10 fb. Motivated by the LHC diphoton excess, we propose that the possible resonance candidate is a Higgs singlet. To produce the Higgs singlet via gluon-gluon fusion process, we embed the Higgs singlet in the framework of vector-like triplet quark (VLTQ) model. As a result, the Higgs singlet decaying to diphoton final state is via VLTQ loops. Using the enhanced number of new quarks and new Yukawa couplings of the VLTQs and Higgs singlet, we successfully explain the diphoton production cross section. We find that the width of the Higgs singlet is below 1 GeV, its production cross section can be of order of 1 pb at $\sqrt{s}=13$ TeV, and the branching ratio for it decaying to diphoton is around $0.017$ and is insensitive to the masses of VLTQs and new Yukawa couplings. We find a strong correlation between the Higgs Yukawa couplings to $s$-$b$ and $c$-$t$; the resulted branching ratio for $t \to c h$ can be $1.1\times 10^{-4}$ when the constraint from $B_s$ oscillation is applied. With the constrained parameter values, the signal strength for the SM Higgs decaying to diphoton is $\mu_{\gamma\gamma}< 1.18$, which is consistent with the current measurements at ATLAS and CMS.

/pdf/higgs-singlet-boson-as-a-diphoton-resonance-in-a-vectorlike-2z9vifuax9.pdf

Higgs singlet boson as a diphoton resonance in a vectorlike quark model

Three-body nonleptonic B decays in perturbative QCD

Motivated by the recent unexpected large forward-backward asymmetry of the top-quark observed by D0 and CDF at the Tevatron, we investigate a possible explanation for the anomaly within the framework of diquark models In the diquark models, the top-quark pair production is mediated by the u-channel diagram It is found that the color-triplet diquark can generate the forward-backward asymmetry of 20% when the constraint from the cross section of the top-quark pair production is taken into account

Forward-backward asymmetry of the top quark in diquark models

The effects of the peculiar $CP$ conserving phases in unparticle propagators are explored. We find that the phases have a great impact on $CP$ violation. We adopt the decays ${B}_{d}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ and ${B}_{d}\ensuremath{\rightarrow}{\ensuremath{\ell}}^{\ensuremath{-}}{\ensuremath{\ell}}^{+}$ as the illustrators to demonstrate the influences of these phases on the direct $CP$ asymmetries. In particular, we emphasize that unparticle physics is the only model suggested to date that could give the direct $CP$ asymmetries in ${B}_{d}\ensuremath{\rightarrow}{\ensuremath{\ell}}^{\ensuremath{-}}{\ensuremath{\ell}}^{+}$ as large as 15%. We also point out that the unparticle phases could be probed in $B\ensuremath{\rightarrow}{K}^{*}{\ensuremath{\ell}}^{+}{\ensuremath{\ell}}^{\ensuremath{-}}$ decays by using T-odd correlations.

Chuan-Hung Chen

Papers

Excesses of muon g − 2, RD(⁎), and RK(⁎) in a leptoquark model

Higgs singlet boson as a diphoton resonance in a vectorlike quark model

Three-body nonleptonic B decays in perturbative QCD

Forward-backward asymmetry of the top quark in diquark models

Unparticle physics effects on direct CP violation