Perturbative QCD Factorization Approach Research Articles

Study of W-Exchange Mode D0→ϕK̄0

We calculate the branching ratio of rare decay D0→ϕK̄0 using the perturbative QCD factorization approach based on kTfactorization. Our result shows this branching ratio is (8.7±1.4)×10−3, which is consistent with experimental data. Wehope that the CLEO-C and BES-III can measure it more accurately, whichwill help us to understand QCD dynamics and D meson weak decays.

Branching ratio andCPAsymmetry ofB→ρη(′)decays in the perturbative QCD approach

In this paper,we calculate the branching ratios and CP-violating asymmetries for $B^0 \to \rho^0 \eta^{(\prime)}$ and $B^+\to \rho^+ \etap$ decays in the perturbative QCD factorization approach. In this approach, 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 theoretical predictions for the branching ratios are $Br(B^+ \to \rho^+ \eta^{(\prime)}) \approx 9 \times 10^{-6}$ and $Br(B^0 \to \rho^0 \eta^{(\prime)}) \approx 5 \times 10^{-8}$, which agree well with the measured values and currently available experimental upper limits. We also predict large CP-violating asymmetries in these decays: $A_{CP}^{dir}(\rho^\pm \eta)\approx -13 %$, $A_{CP}^{dir}(\rho^\pm \eta^\prime)\approx -18 %$, $A_{CP}^{dir}(\rho^0 \eta)\approx -41%$, $A_{CP}^{dir}(\rho^0 \eta^\prime)\approx -27%$, $A_{CP}^{mix}(\rho^0 \eta)\approx +25%$, and $A_{CP}^{mix}(\rho^0 \eta^\prime) \approx +11%$, which can be tested by the current or future B factory experiments.

Coherent QCD multiple scattering in proton–nucleus collisions

We argue that high energy proton–nucleus (p + A) collisions provide an excellent laboratory for studying nuclear size enhanced parton multiple scattering where power corrections to the leading twist perturbative QCD factorization approach can be systematically computed. We identify and resum these corrections and calculate the centrality- and rapidity-dependent nuclear suppression of single and double inclusive hadron production at moderate transverse momenta. We demonstrate that both spectra and dihadron correlations in p + A reactions are sensitive measures of such dynamical nuclear attenuation effects.

Difference inB+andB0DirectCPAsymmetry as an Effect of a Fourth Generation

Direct CP violation in B0 --> K+ pi- decay has emerged at the -10% level, but the asymmetry in B+ --> K+ pi0 mode is consistent with zero. This difference points towards possible new physics in the electroweak penguin operator. We point out that a sequential fourth generation, with sizable V(t' s)* V(t' b) and near maximal phase, could be a natural cause. We use the perturbative QCD factorization approach for B --> Kpi amplitudes. While the B0 --> K+ pi- mode is insensitive to t', we critically compare t' effects on direct CP violation in B+ --> K+ pi0 with b --> sl+ l- and B(s) mixing. If the K+ pi0 - K+ pi- asymmetry difference persists, we predict sin2phi(Bs) to be negative.

The perturbative QCD factorization approach in high energy nuclear collisions

I discuss the systematic modifications to the perturbative QCD factorization approach in high energy ℓ + A, p + A and A + A reactions. These include transverse momentum diffusion manifest in the Cronin effect and a small increase in the dijet acoplanarity; nuclear size enhanced power corrections that lead to shadowing in deeply inelastic scattering and suppression of single and double inclusive hadron production at forward rapidity at RHIC but disappear as a function of the transverse momentum; inelastic attenuation of the jet cross sections or jet quenching that persists to much higher pT.