Zhen-Jun Xiao

Branching ratio and CP asymmetry of B→πη(′) decays in the perturbative QCD approach

Abstract We calculate the branching ratios and CP-violating asymmetries for B 0 → π 0 η ( ′ ) and B + → π + η ( ′ ) decays in the perturbative QCD (pQCD) factorization approach here. We not only calculate the usual factorizable contributions, but also evaluate the non-factorizable and annihilation type contributions. Besides the current–current operators, the contributions from the QCD and electroweak penguin operators are also taken into account. The pQCD results for the CP-averaged branching ratios are Br ( B + → π + η ) ≈ 4.1 × 10 −6 , Br ( B + → π + η ′ ) ≈ 2.4 × 10 −6 , and Br ( B 0 → π 0 η ( ′ ) ) ≈ 0.2 × 10 −6 , which agree very well with the measured values or currently available experimental upper limits. We also predict large CP-violating asymmetries in these decays: A CP dir ( π ± η ( ′ ) ) ∼ A CP dir ( π 0 η ( ′ ) ) ∼ − 0.35 , and A CP mix ( π 0 η ( ′ ) ) ∼ 0.67 , but with large errors. The pQCD prediction for A CP dir ( π ± η ) ( A CP dir ( π ± η ′ ) ) has the same (opposite) sign with the primary measured values. Further improvements in both theory and experiments are needed to clarify this discrepancy.

The production and decay of the top partner T in the left–right twin Higgs model at the ILC and CLIC

Abstract The left–right twin Higgs model (LRTHM) predicts the existence of the top partner T . In this work, we make a systematic investigation for the single and pair production of this top partner T through the processes: e + e − → t T ¯ + T t ¯ and T T ¯ , the neutral scalar (the SM-like Higgs boson h or neutral pseudoscalar boson ϕ 0 ) associate productions e + e − → t T ¯ h + T t ¯ h , T T ¯ h , t T ¯ ϕ 0 + T t ¯ ϕ 0 and T T ¯ ϕ 0 . From the numerical evaluations for the production cross sections and relevant phenomenological analysis we find that (a) the production rates of these processes, in the reasonable parameter space, can reach the level of several or tens of femtobarns; (b) for some cases, the peak value of the resonance production cross section can be enhanced significantly and reaches to the level of pb; (c) the subsequent decay of T → ϕ + b → t b ¯ b may generate typical phenomenological features rather different from the signals from other new physics models beyond the standard model (SM); and (d) since the relevant SM background is generally not large, some signals of the top partner T predicted by the LRTHM may be detectable in the future ILC and CLIC experiments.

Left-right twin Higgs model confronted with the latest LHC Higgs data

Motivated by the latest LHC Higgs data, we calculate the new physics contributions to the Higgs decay channels of

The NLO contributions to the scalar pion form factors and the O(αs2) annihilation corrections to the B→ππ decays

hto gammagamma, Zgamma, tautau, WW^*

Improved perturbative QCD formalism for

and

B_c

ZZ^*

meson decays

in the left-right twin Higgs (LRTH) model, induced by the loops involving the heavy T-quark, the

Revisiting the factorization theorem for

W_H

\rho \gamma^{*} \to \pi(\rho)

and

at twist 3

phi^pm