Annihilation Corrections Research Articles

Application of the light-front holographic wavefunction for heavy-light pseudoscalar meson in Bd,s → Dd,sP decays

In this paper we extend our analyses of the decay constant and distribution amplitude with an improved holographic wavefunction to the heavy-light pseudoscalar mesons. In the evaluations, the helicity-dependence of the holographic wavefunction is considered; and an independent mass scale parameter is employed to moderate the strong suppression induced by the heavy quark. Under the constraints from decay constants and masses of pseudoscalar mesons, the χ2-analyses for the holographic parameters exhibit a rough consistence with the results obtained by fitting the Regge trajectory. With the fitted parameters, the results for the decay constants and distribution amplitudes are presented. We then show their application in evaluating the Bd,s→Dd,sP decays, in which the power-suppressed spectator scattering and weak annihilation corrections are first estimated. Numerically, the spectator scattering and weak annihilation corrections present a negative shift of about 0.7% on the branching fractions; while, the predictions are still larger than the experimental data. Such small negative shift confirms the estimation based on the power counting rules.

Study of the weak annihilation contributions in charmless varvec{B_srightarrow VV} decays

In this paper, in order to probe the spectator-scattering and weak annihilation contributions in charmless B_srightarrow VV (where V stands for a light vector meson) decays, we perform the chi ^2-analyses for the endpoint parameters within the QCD factorization framework, under the constraints from the measured bar{B}_{s}rightarrow rho ^0phi , phi K^{*0}, phi phi and K^{*0}bar{K}^{*0} decays. The fitted results indicate that the endpoint parameters in the factorizable and nonfactorizable annihilation topologies are non-universal, which is also favored by the charmless Brightarrow PP and PV (where P stands for a light pseudo-scalar meson) decays observed in previous work. Moreover, the abnormal polarization fractions f_{L,bot }(bar{B}_{s}rightarrow K^{*0}bar{K}^{*0})=(20.1pm 7.0)%,(58.4pm 8.5)% measured by the LHCb collaboration can be reconciled through the weak annihilation corrections. However, the branching ratio of bar{B}_{s}rightarrow phi K^{*0} decay exhibits a tension between the data and theoretical result, which dominates the contributions to chi _mathrm{min}^2 in the fits. Using the fitted endpoint parameters, we update the theoretical results for the charmless B_srightarrow VV decays, which will be further tested by the LHCb and Belle-II experiments in the near future.

NNLL soft and Coulomb resummation for squark and gluino production at the LHC

We present predictions for the total cross sections for pair production of squarks and gluinos at the LHC including a combined NNLL resummation of soft and Coulomb gluon effects. We derive all terms in the NNLO cross section that are enhanced near the production threshold, which include contributions from spin-dependent potentials and so-called annihilation corrections. The NNLL corrections at $\sqrt{s}=13$ TeV range from up to $20\%$ for squark-squark production to $90\%$ for gluino pair production relative to the NLO results and reduce the theoretical uncertainties of the perturbative calculation to the $10\%$ level. Grid files with our numerical results are publicly available.

Fits of weak annihilation and hard spectator scattering corrections in Bu,d VV decays

In this paper, the contributions of weak annihilation and hard spectator scattering in , , , and decays are investigated within the framework of quantum chromodynamics factorization. Using the experimental data available, we perform analyses of end-point parameters in four cases based on the topology-dependent and polarization-dependent parameterization schemes. The fitted results indicate that: (i) in the topology-dependent scheme, the relation obtained through and PV decays is favored by the penguin-dominated decays at 95% CL; (ii) the large hard spectator scattering corrections and/or the simplification are challenged by , even though they are allowed by and PV decays and helpful for resolving the ‘ puzzle’; (iii) in the polarization-dependent scheme, the relation is always required. Moreover, we have updated the theoretical results for decays with the best-fit values of end-point parameters. A few observables, such as the ones of pure annihilation decay, are also identified for probing the annihilation corrections.

Probing spectator scattering and annihilation corrections inBs→PVdecays

Motivated by the recent LHCb measurements on ${\overline{B}}_{s}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{\ensuremath{-}}{K}^{*+}$ and ${\overline{B}}_{s}\ensuremath{\rightarrow}{K}^{\ifmmode\pm\else\textpm\fi{}}{K}^{*\ensuremath{\mp}}$ decay modes, we revisit the ${B}_{s}\ensuremath{\rightarrow}PV$ decays within QCD factorization framework. The effects of hard-spectator scattering and annihilation corrections are studied in detail. After performing a ${\ensuremath{\chi}}^{2}$-fit on the end-point parameters ${X}_{A}^{i,f}({\ensuremath{\rho}}_{A}^{i,f},{\ensuremath{\phi}}_{A}^{i,f})$ and ${X}_{H}({\ensuremath{\rho}}_{H},{\ensuremath{\phi}}_{H})$ with available data, it is found that although some possible mismatches exist, the universalities of ${X}_{A}^{i,f}$ and ${X}_{H}$ in ${B}_{s}$ and ${B}_{u,d}$ systems are still allowed within theoretical uncertainties and experimental errors. With the end-point parameters obtained from ${B}_{u,d}\ensuremath{\rightarrow}PV$ decays, the numerical results and detailed analyses for the observables of ${\overline{B}}_{s}\ensuremath{\rightarrow}\ensuremath{\pi}{K}^{*}$, $\ensuremath{\rho}K$, $\ensuremath{\pi}\ensuremath{\rho}$, $\ensuremath{\pi}\ensuremath{\phi}$, and $K\ensuremath{\phi}$ decay modes are presented. In addition, we have identified a few useful observables, especially the ones of ${\overline{B}}_{s}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{0}\ensuremath{\phi}$ decay for instance, for probing hard-spectator scattering and annihilation contributions.

Constraints on hard spectator scattering and annihilation corrections in Bu,d → PV decays within QCD factorization

In this paper, we investigate the contributions of hard spectator scattering and annihilation in B→PV decays within the QCD factorization framework. With available experimental data on B→πK⁎,ρK,πρ and Kϕ decays, comprehensive χ2 analyses of the parameters XA,Hi,f(ρA,Hi,f,ϕA,Hi,f) are performed, where XAf(XAi) and XH are used to parameterize the endpoint divergences of the (non)factorizable annihilation and hard spectator scattering amplitudes, respectively. Based on χ2 analyses, it is observed that (1) The topology-dependent parameterization scheme is feasible for B→PV decays; (2) At the current accuracy of experimental measurements and theoretical evaluations, XH=XAi is allowed by B→PV decays, but XH≠XAf at 68% C.L.; (3) With the simplification XH=XAi, parameters XAf and XAi should be treated individually. The above-described findings are very similar to those obtained from B→PP decays. Numerically, for B→PV decays, we obtain (ρA,Hi,ϕA,Hi[°])=(2.87−1.95+0.66,−145−21+14) and (ρAf,ϕAf[°])=(0.91−0.13+0.12,−37−9+10) at 68% C.L. With the best-fit values, most of the theoretical results are in good agreement with the experimental data within errors. However, significant corrections to the color-suppressed tree amplitude α2 related to a large ρH result in the wrong sign for ACPdir(B−→π0K⁎−) compared with the most recent BABAR data, which presents a new obstacle in solving “ππ” and “πK” puzzles through α2. A crosscheck with measurements at Belle (or Belle II) and LHCb, which offer higher precision, is urgently expected to confirm or refute such possible mismatch.

A combined fit on the annihilation corrections in [formula omitted] decays within QCDF

Motivated by the possible large annihilation contributions implied by recent CDF and LHCb measurements on nonleptonic annihilation B-meson decays, and the refined experimental measurements on hadronic B-meson decays, we study the strength of annihilation contributions within QCD factorization (QCDF) in this paper. With the available measurements of two-body Bu,d,s→ππ,πK,KK decays, a comprehensive fit on the phenomenological parameters XAi,f (or ρAi,f and ϕAi,f) which are used to parameterize the endpoint singularity in annihilation amplitudes is performed with the statistical χ2 approach. It is found that (1) flavor symmetry breaking effects are hardly to be distinguished between XA,si and XA,di due to the large experimental errors and theoretical uncertainties, where XA,si and XA,di are related to the nonfactorization annihilation contributions in Bs and Bu,d decay, respectively. So XA,si≃XA,di is a good approximation by now. (2) In principle, parameter XAf which is related to the factorization annihilation contributions and independent of the initial state can be regarded as the same variable for Bu,d,s decays. (3) Numerically, two solutions are found, one is (ρAi,ϕAi[°])=(2.98−0.86+1.12,−105−24+34) and (ρAf,ϕAf[°])=(1.18−0.23+0.20,−40−8+11), the other is (ρAi,ϕAi[°])=(2.97−0.90+1.19,−105−24+32) and (ρAf,ϕAf[°])=(2.80−0.21+0.25,165−3+4). Obviously, nonfactorization annihilation parameter XAi is generally unequal to factorization annihilation parameter XAf, which differs from the traditional treatment. With the fitted parameters, all results for observables of Bu,d,s→ππ,πK,KK decays are in good agreement with experimental data.

Revisiting the annihilation corrections in nonleptonicB¯s0decays within QCD factorization

Motivated by the recent measurements of nonleptonic ${\overline{B}}_{s}^{0}$ decays by the CDF and LHCb collaborations, especially the large $\mathcal{B}({\overline{B}}_{s}^{0}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}})$, we revisit the hard spectator and annihilation corrections in ${\overline{B}}_{s}^{0}$ decays within a QCD factorization approach, with two schemes for the possible parameters for the known end-point divergence appearing in the estimation of the hard spectator and annihilation diagrams. The first one is to conservatively estimate the possible contributions by parametrization (scheme I); another one uses an infrared finite gluon propagator (scheme II) to regulate the end-point singularity. In scheme I, with the constraints from the measured ${\overline{B}}_{s}^{0}\ensuremath{\rightarrow}PP(VV)$ decays, two (four) restricted solutions of the parameter spaces are found. In scheme II, we find that most of the theoretical predictions agree well with the experimental data with a single parameter ${m}_{g}\ensuremath{\sim}0.5\text{ }\text{ }\mathrm{GeV}$. However, within both schemes, $\mathcal{B}({\overline{B}}_{s}^{0}\ensuremath{\rightarrow}\ensuremath{\phi}\ensuremath{\phi})$ are always much larger than $\mathcal{B}({\overline{B}}_{s}^{0}\ensuremath{\rightarrow}{K}^{*0}{\overline{K}}^{*0})$, in contrast to the experimental results $\mathcal{B}({\overline{B}}_{s}^{0}\ensuremath{\rightarrow}\ensuremath{\phi}\ensuremath{\phi})\ensuremath{\simeq}\mathcal{B}({\overline{B}}_{s}^{0}\ensuremath{\rightarrow}{K}^{*0}{\overline{K}}^{*0})$. It is noted that the pattern $\mathcal{B}({\overline{B}}_{s}^{0}\ensuremath{\rightarrow}\ensuremath{\phi}\ensuremath{\phi})>\mathcal{B}({\overline{B}}_{s}^{0}\ensuremath{\rightarrow}{K}^{*0}{\overline{K}}^{*0})$ also persists in other theoretical frameworks; thus, the present experimental result $\mathcal{B}({\overline{B}}_{s}^{0}\ensuremath{\rightarrow}\ensuremath{\phi}\ensuremath{\phi})\ensuremath{\simeq}\mathcal{B}({\overline{B}}_{s}^{0}\ensuremath{\rightarrow}{K}^{*0}{\overline{K}}^{*0})$ raises a challenge to theoretical approaches for B nonleptonic decays. Further refined measurements and theoretical studies are called for to resolve such a possible anomaly.