15449960
QCD Factorization For B Decays To Two Light Pseudoscalars Including Chirally Enhanced Corrections
Since b quark mass is not asymptotically large, chirally enhanced corrections which arise from twist-3 wave functions may be important in B decays. We thus evaluate the hadronic matrix elements with the emitted meson described by leading twist and twist-3 distribution amplitudes $\Phi_p(x)$. After summing over the four "vertex correction" diagrams, we obtain the results with infrared finiteness which shows that chirally enhanced corrections arise from $\Phi_p(x)$ can be consistently included in QCD factorization. We also briefly discuss the contributions from "hard spectator" diagrams.
11323590
Charmless two-body B decays: A global analysis with QCD factorization
In this paper, we perform a global analysis of $\stackrel{\ensuremath{\rightarrow}}{B}\mathrm{PP}$ and $\mathrm{PV}$ decays with the QCD factorization approach. It is encouraging to observe that the predictions of QCD factorization are in good agreement with experiment. The best fit $\ensuremath{\gamma}$ is around $79\ifmmode^\circ\else\textdegree\fi{}.$ The penguin-diagram--to--tree-diagram ratio $|{P}_{\ensuremath{\pi}\ensuremath{\pi}}{/T}_{\ensuremath{\pi}\ensuremath{\pi}}|$ of ${\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ decays is preferred to be larger than $0.3.$ We also show the confidence levels for some interesting channels: ${B}^{0}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{0}{\ensuremath{\pi}}^{0},$ ${K}^{+}{K}^{\ensuremath{-}},$ and ${B}^{+}\ensuremath{\rightarrow}\ensuremath{\omega}{\ensuremath{\pi}}^{+},\ensuremath{\omega}{K}^{+}.$ For $\stackrel{\ensuremath{\rightarrow}}{B}\ensuremath{\pi}{K}^{*}$ decays, they are expected to have smaller branching ratios with more precise measurements.
14205678
Phenomenological analysis of B -> PP decays with QCD factorization
In this paper, we study nonleptonic charmless B decays to two light pseudoscalar mesons within the frame of QCD factorization, including the contributions from the chirally enhanced power corrections and weak annihilation. Predictions for the CP-averaged branching ratios and CP-violating asymmetries are given. Within the reasonable range of the parameters, we find that our predictions for the branching ratios of B-->PP are consistent with the present experimental data. But because of the logarithmic divergences at the end points in the hard spectator scatterings and weak annihilation, there are still large uncertainties in these predictions.
7838966
QCD factorization for B ---> P P
In this work, we give a detailed discussion for QCD factorization involved in the complete chirally enhanced power corrections in the heavy quark limit for B decays to two light pseudoscalar mesons, and present some detailed calculations of radiative corrections at the order of ${\ensuremath{\alpha}}_{s}.$ We point out that the infrared finiteness of the vertex corrections in the chirally enhanced power corrections requires twist-3 light-cone distribution amplitudes (LCDAs) of the light pseudoscalar symmetric. However, even in the symmetric condition, there is also a logarithmic divergence from the end points of the twist-3 LCDAs in the hard spectator scattering. We point out that the decay amplitudes of $\stackrel{\ensuremath{\rightarrow}}{B}\mathrm{PP}$ predicted by QCD factorization are really free of the renormalization scale dependence, at least at the order of ${\ensuremath{\alpha}}_{s}.$ At last, we briefly compare the QCD factorization with the generalized factorization and PQCD method.
119189533
The leading twist light-cone distribution amplitudes for the S-wave and P-wave quarkonia and their applications in single quarkonium exclusive productions
A bstractIn this paper, we calculate twist-2 light-cone distribution amplitudes (LCDAs) of the S-wave and P-wave quarkonia (namely 1S0 state ηQ, 3S1 state $ J/\psi \left(\varUpsilon \right) $, 1P1 state hQ and 3PJ states χQJ with J = 0, 1, 2 and Q = c, b) to the next-leading order of the strong coupling αs and leading order of the velocity expansion v in the non-relativistic QCD (NRQCD). We apply these LCDAs to some single quarkonium exclusive productions at large center-of-mass energy, such as γ* → ηQγ, χQJγ (J = 0, 1, 2), Z → ηQγ, χQJγ (J = 0, 1, 2),$ J/\psi \left(\varUpsilon \right)\gamma $, hQγ and h → J/ψγ, by adopting the collinear factorization. The asymptotic behaviors of those processes obtained in NRQCD factorization are reproduced.
119210077
Refactorizing NRQCD short-distance coefficients in exclusive quarkonium production
In a typical exclusive quarkonium production process, when the center-of-mass energy, is much greater than the heavy quark mass in, large kinematic logarithms of s/m(2) will unavoidably arise at each order of perturbative expansion in the short-distance coefficients of the nonrelativistic QCD (NRQCD) factorization formalism, which may potentially harm the perturbative expansion. This symptom reflects that the hard regime in NRQCD factorization is too coarse and should be further factorized. We suggest that this regime can be further separated into "hard" and "collinear" degrees of freedom, so that the familiar light-cone approach can be employed to reproduce the NRQCD matching coefficients at the zeroth order of m(2)/s and order by order in alpha(s). Taking two simple processes, exclusive eta(b)+ gamma production in e(+)e(-) annihilation and Higgs boson radiative decay into gamma, as examples, we illustrate how the leading logarithms of s/m(2) in the NRQCD matching coefficients are identified and summed to all orders in alpha(s) with the aid of Brodsky-Lepage evolution equation. (C) 2009 Elsevier B.V. All rights reserved.
119112269
Probing W+W−γ production and anomalous quartic gauge boson couplings at the CERN LHC
A bstractTriple gauge boson associated production at the LHC serves as an interesting channel to test the robustness of the Standard Model. Any deviation from its SM prediction may indicate possible existence of relevant new physics, e.g., anomalous quartic gauge boson couplings. In this paper, a Monte-Carlo feasibility study of measuring W+W−γ production with pure leptonic decays and probing anomalous quartic gauge-boson (e.g., WWγγ) couplings, is presented in detail for the first time, with parton shower and detector simulation effects taken into account. Our results show that at the $ \sqrt{s}=14 $ TeV LHC with an integrated luminosity of 100 (30) fb−1, one can reach a significance of 9 (5) σ to observe the SM W+W−γ production, and can constrain at the 95% C.L. the anomalous WWγγ coupling parameters, e.g., $ a{{{_{0,c}^W}} \left/ {{{\varLambda^2}}} \right.} $ (see ref. [16] for their definitions), at 1 × 10−5 GeV−2 level, respectively.
54838095
Holographic photon production with magnetic field in anisotropic plasmas
A bstractWe investigate the thermal photon production from constant magnetic field in a strongly coupled and anisotropic plasma via the gauge/gravity duality. The dual geometry with pressure anisotropy is generated from the axion-dilaton gravity action introduced by Mateos and Trancancelli and the magnetic field is coupled to fundamental matters(quarks) through the D3/D7 embeddings. We find that the photon spectra with different quark mass are enhanced at large frequency when the photons are emitted parallel to the anisotropic direction with larger pressure or perpendicular to the magnetic field. However, in the opposite conditions for the emitted directions, the spectra approximately saturate isotropic results in the absence of magnetic field. On the other hand, a resonance emerges at moderate frequency for the photon spectrum with heavy quarks when the photons move perpendicular to the magnetic field. The resonance is more robust when the photons are polarized along the magnetic field. On the contrary, in the presence of pressure anisotropy, the resonance will be suppressed. There exist competing effects of magnetic field and pressure anisotropy on meson melting in the strongly coupled super Yang-Mills plasma, while we argue that the suppression led by anisotropy may not be applied to the quark gluon plasma.
118635824
Jet quenching and holographic thermalization with a chemical potential
A bstractWe investigate jet quenching of virtual gluons and thermalization of a strongly-coupled plasma with a non-zero chemical potential via the gauge/gravity duality. By tracking a charged shell falling in an asymptotic AdSd+1 background for d = 3 and d = 4, which is characterized by the AdS-Reissner-Nordström-Vaidya (AdS-RN-Vaidya) geometry, we extract a thermalization time of the medium with a non-zero chemical potential. In addition, we study the falling string as the holographic dual of a virtual gluon in the AdS-RN-Vaidya spacetime. The stopping distance of the massless particle representing the tip of the falling string in such a spacetime could reveal the jet quenching of an energetic light probe traversing the medium in the presence of a chemical potential. We find that the stopping distance decreases when the chemical potential is increased in both AdS-RN and AdS-RN-Vaidya spacetimes, which correspond to the thermalized and thermalizing media respectively. Moreover, we find that the soft gluon with an energy comparable to the thermalization temperature and chemical potential in the medium travels further in the non-equilibrium plasma. The thermalization time obtained here by tracking a falling charged shell does not exhibit, generically, the same qualitative features as the one obtained studying non-local observables. This indicates that — holographically — the definition of thermalization time is observer dependent and there is no unambiguos definition.