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Jian-Feng Cheng

Publications and source records attributed to Jian-Feng Cheng.

8 recordsLinked to original sources
arXiv2011

The cuprate superconductors: a phenomenological overlook

We, basing on the quantum critical point (QCP)($p = 0.19 $), propose a phenomenological description on high-$T_c$ superconductivity in the cuprate superconductors, and suggest it divides the whole doping region into two parts: the underdoped region ($p < 0.19 $) and the overdoped region ($ p> 0.19 $). The electrons in the former are localized and form the localized Fermi liquid, a kind of the non-Fermi liquid, where the carriers are the holes; the electrons in the latter are itinerant and form the Fermi liquid, where the carriers are the electrons. We further argue that localization is a prerequisite to the pseudogap; the superconductivity gap and coherence forms at the same time, which both share the same energy scale; coherence induces phonon around the node.

cond-mat.supr-con↗
arXiv2006

Search for new physics from $B\toπϕ$

We investigate the pure penguin process $B^-\to π^-ϕ$ using QCD factorization approach to calculate hadronic matrix elements to the $α_s$ order in some well-known NP models. It is shown that the NP contributions in R-parity conserved SUSY models and 2HDMs are not enough to saturate the experimental upper bounds for $B\to ϕπ$. We have shown that the flavor changing $Z^\prime$ models can make the branching ratios of $B\to ϕπ$ to saturate the bound under all relevant experimental constraints.

hep-ph↗
arXiv2006

Implications for new physics from ${\bar B}^0\to π^0π^0$ and ${\bar B}^0\to {\bar K}^0K^0$

We have analyzed the ${\bar B}^0\to π^0π^0$ puzzle in three kinds of models beyond the standard model (SM). It is shown that the minimal flavor violation (MFV) models, the minimal supersymmetric standard model (MSSM), and the two Higgs doublet models (2HDM) I and II can not give an explanation of the ${\bar B}^0\to π^0π^0$ puzzle within $1 σ$ experimental bounds and the model III 2HDM can explain the puzzle without a conflict with other experimental measurements. If the constraint on $C_{8g}$ from $b\to s g$ is not imposed, for all kinds of insertions considered there are regions of parameter space, where the scalar quark mass is larger (much larger) than the gluino mass in the case of LR or RL (LL or RR), in which the puzzle can be resolved within $1 σ$ experimental bounds.

hep-ph↗
arXiv2005

Prediction of $B_c\to Dπ$ in the pQCD approach

We investigate the branching ratios and direct CP asymmetries of $B_c^+\to D^0π^+$ and $B_c^+\to D^+π^0$ decays in the PQCD approach. All the diagrams with emission topology or annihilation topology are calculated strictly. A branching ratio of $10^{-6}$ and $10^{-7}$ for $B_c^+\to D^0π^+$ and $B_c^+\to D^+π^0$ decay is predicted, respectively. Because of the different weak phase and strong phase from penguin operator and two kinds of tree operator contributions, we predict a possible large direct CP violation: $A^{\rm dir}_{cp} (B_c^\pm \to D^0 π^\pm)\approx -50%$ and $A^{\rm dir}_{cp} (B_c^\pm \to D^\pm π^0)\approx 25%$ when $γ=55^\circ$, which can be tested in the coming LHC.

hep-ph↗
arXiv2004

CP asymmetries in $B\to ϕK_S$ and $B\to η' K_S$ in MSSM

We study the $B\to ϕK_S$ and $B\to \ep K_S$ decays in MSSM by calculating hadronic matrix elements of operators with QCD factorization approach and including neutral Higgs boson (NHB) contributions. We calculate the Wilson coefficients of operators including the new operators which are induced by NHB penguins at LO using the MIA with double insertions. We calculate the $α_s$ order hadronic matrix elements of the new operators for $B\to ϕK_s$ and $B\to η^\prime K_s$. It is shown that the recent experimental results on the time-dependent CP asymmetries in $B\to ϕK_S$ and $B\to \ep K_S$, $S_{ϕK}$ is negative and $S_{η^{\prime} K}$ is positive, which can not be explained in SM, can be explained in MSSM if there are flavor non-diagonal squark mass matrix elements of 2nd and 3rd generations whose size satisfies all relevant constraints from known experiments ($B\to X_Sγ, B_s\to μ^+μ^-, B\to X_s μ^+μ^-, B\to X_s g, ΔM_s$, etc.). In particular, we find that one can explain the experimental results with a flavor non-diagonal mass insertion of any chirality when $α_s$ corrections of hadronic matrix elements of operators are included, in contrast with the claim in the literature. At the same time, the branching ratios for the two decays can also be in agreement with experimental measurements.

hep-ph↗
arXiv2003

Neutral Higgs boson contributions to CP asymmetry of $B \to ΦK_S$ in MSSM

We have studied the neutral Higgs boson (NHB) contributions to the pure penguin process $B\to ϕK_S$ in MSSM with middle and large $\tanβ$ (say, $>$ 8). We show that the $α_s$ order hadronic matrix elements of NHB induced operators can make sizable effects on both the branch ratio and time dependent CP asymmetry $S_{ϕK}$. Under the all relevant experimental constraints, the Higgs mediated contributions to $S_{ϕK}$ alone can provide a significant deviation from SM and, in particular, lead to a negative $S_{ϕK}$ which is reported by BaBar and Belle.

hep-ph↗
arXiv2002

B\to πϕin SM and MSSM

We investigate the pure penguin decays $B\to πϕ$ in the Standard Model(SM) and in the Constrained Minimal Supersymmetric Standard Model (CMSSM) using the QCD factorization approach and consider the Sudakov effects in the twist-3 contribution. We find ${\rm Br}(B^-\to π^-ϕ) = (1.95-5.70)\times 10^{-9}$ in SM and $(1.1-2.4)\times 10^{-8}$ in CMSSM with large $\tanβ$ which is about one order of magnitude larger than that in SM.

hep-ph↗