We explore the correspondence between the final state in e^+e^- annihilation and the small-x hadronic wavefunction in the transverse plane both in weakly coupled QCD and strongly coupled N=4 SYM. At strong coupling, the virtual and static photon produced in e^+e^- annihilation can be treated as a shock wave propagating in AdS space leaving spherical energy and charge distributions on the boundary. This is shown to be mathematically identical to the computation of energy and charge distributions in the transverse plane generated by a high energy color singlet state. At weak coupling, the correspondence is useful in studying interjet observables. By performing the stereographic projection to the BFKL equation, we construct an exact solution to the evolution equation derived by Marchesini and Mueller, and find the angular distribution of small-x gluons in the interjet region. Finally we argue that the correspondence holds also for the energy correlation functions.
We give predictions for the branching ratios of several rare radiative B-decays which proceed only through weak annihilation mechanism. In addition to previous analysis we estimate the branching ratios of $\bar{B}^0_s\to D^{*0}γ$ and $B_c^-\toρ^-γ$ decays and obtain $2.87\cdot 10^{-9}$ and $2.59\cdot 10^{-7}$ for them correspondingly. The accuracy of the predictions is at the level of 20\%.
In this talk, we present the predictions for a number of radiative decays $B_{(s)}\to Vγ$, with the vector meson in the final state, which proceed through the weak-annihilation mechanism. Within the factorization approximation, we take into account the photon emission from the $B$-meson loop and from the vector-meson loop. The highest branching ratios for the weak-annihilation reactions reported here are ${\cal B}(\bar B^0_s\to J/ψγ)=1.5\cdot 10^{-7}$ and ${\cal B}(B^-\to \bar D_s^{*-}γ)=1.7\cdot 10^{-7}$, the estimated accuracy of these predictions being at the level of 20%.
We use currently available data of nonleptonic charmless 2-body $B\to MM$ decays ($MM = PP, PV, VV$) that are mediated by $b\to (d, s)$ QCD- and QED-penguin operators to study weak annihilation and new-physics effects in the framework of QCD factorization. In particular we introduce one weak annihilation parameter for decays related by ($u \leftrightarrow d$) quark interchange and test this universality assumption. Within the standard model, the data supports this assumption with the only exceptions in the $B\to K π$ system, which exhibits the well-known "$ΔA_{CP}$ puzzle", and some tensions i…
The recently measured semileptonic D_s decay rate can be used to constrain weak annihilation (WA) effects in semileptonic D and B decays. We revisit the theoretical predictions for inclusive semileptonic D_{(s)} decays using a variety of quark mass schemes. The most reliable results are obtained if the fits to B decay distributions are used to eliminate the charm quark mass dependence, without using any specific charm mass scheme. Our fit to the available data shows that WA is smaller than commonly assumed. There is no indication that the WA octet contribution (which is better constrained than…
We reinvestigate the effect of annihilations on the distribution of collisionless dark matter (DM) in a spherical density spike around a massive black hole. We first construct a very simple, pedagogic, analytic model for an isotropic phase space distribution function that accounts for annihilation and reproduces the "weak cusp" found by Vasiliev for DM deep within the spike and away from its boundaries. The DM density in the cusp varies as $r^{-1/2}$ for $s$-wave annihilation, where $r$ is the distance from the central black hole, and is not a flat "plateau" profile. We then extend this model …
In this research the weak decay of $B^+_c$ decays to the $K^+K^-π^+$ final state, which is observed by LHCb collaboration for the first time, is calculated in the quasi-two-body decays which takes into account the $B^0_s$, $χ_{c0}$ and $D^0$ resonances and weak annihilation nonresonant contributions. In this process, the $B^+_c$ meson decays first into $B^0_sπ^+$, $χ_{c0}π^+$ and $D^0π^+$ intermediate states, and then the $B^0_s$, $χ_{c0}$ and $D^0$ resonances decay into $K^+K^-$ components, which undergo final state interaction. The mode of the $B^+_c\rightarrow D^0(\rightarrow K^-π^+)K^+$ is…
Weak corrections to Minimal Dark Matter annihilations
INFN Sezione di Pisa, Italia（意大利国家核物理研究所比萨分部）；Dipartimento di Fisica dell’Università di Pisa, Italia（意大利比萨大学物理系）；Departamento de Física Teórica and Instituto de Física Teórica, Universidad Autónoma de Madrid, Spain（西班牙马德里自治大学理论物理系及理论物理研究所）
In this paper, in order to probe the spectator-scattering and weak annihilation contributions in charmless $B_s\to VV$ (where $V$ stands for a light vector meson) decays, we perform the $χ^2$-analyses for the end-point parameters within the QCD factorization framework, under the constraints from the measured $\bar B_{s}\to$$ρ^0ϕ$, $ϕK^{*0}$, $ϕϕ$ and $K^{*0}\bar K^{*0}$ decays. The fitted results indicate that the end-point parameters in the factorizable and nonfactorizable annihilation topologies are non-universal, which is also favored by the charmless $B\to PP$ and $PV$ (where $P$ stands fo…
We obtain predictions for a number of radiative decays $B_{(s)}\to Vγ$, $V$ the vector meson, which proceed through the weak-annihilation mechanism. Within the factorization approximation, we take into account the photon emission from the $B$-meson loop and from the vector-meson loop; the latter subprocesses were not considered in the previous analyses but are found to have sizeable impact on the $B_{(s)}\to Vγ$ decay rate. The highest branching ratios for the weak-annihilation reactions reported here are ${\cal B}(\bar B^0_s\to J/ψγ)=1.5\cdot 10^{-7}$ and ${\cal B}(B^-\to \bar D_s^{*-}γ)=1.7\…
In this paper, the contributions of weak annihilation and hard spectator scattering in $B\to ρK^*$, $ K^* \bar{K}^*$, $ϕK^*$, $ρρ$ and $ϕϕ$ decays are investigated within the framework of QCD factorization. Using the experimental data available, we perform $χ^2$ 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 $(ρ_A^{i},ϕ_A^{i})\neq (ρ_A^{f},ϕ_A^{f})$ gotten through $B\to PP$ and $PV$ decays is favored by the penguin-dominated $…
Imbalanced beauty-charmed baryons $ Ξ_{bc}^{+,0} $ are of great significance to the development of heavy flavor physics. In this work, we study the inclusive weak-annihilation decays of $Ξ_{bc}^{+,0}$ and their contributions to the $Ξ_{bc}^{+,0}$ lifetimes. For the calculation of the inclusive $Ξ_{bc}^{+,0}\to X_{cs}$ decay width where $X_{cs}$ stands for the sum of the final states with charm number +1 and strange number -1, we work in the heavy diquark effective theory which provides us with a convenient technical tool to construct the operator product expansion. The $Ξ_{bc}^{+,0}$ is consid…
At the tail of its velocity distribution, cold dark matter (DM) can annihilate at finite temperature to states heavier than itself. We explore the possibility that DM freezeout is dictated by these "forbidden annihilations" at the electroweak scale. Demanding that annihilation products be Standard Model particles, we find that for the forbidden mechanism to primarily set the DM relic abundance, DM must couple predominantly, if not solely, to top quarks. This can be arranged by invoking a non-trivial flavor structure such as Minimal Flavor Violation. We avail two avenues to achieve the correct …
We propose an alternative evaluation of the long-distance weak annihilation (WA, also called one-photon exchange in this paper) contribution to the rare semileptonic $B^{\pm}\to (π^{\pm},K^{\pm})\ell^+\ell^-$ ($\ell=e,\,μ$) decays. This hadronic description at low energies is matched at intermediate energies to its short-distance counterpart in terms of quark and gluon degrees of freedom. Although the WA contribution does not contribute to solve the possible breaking of lepton-universality observed by LHCb in the $B^{\pm}\to K^{\pm}(μ^+μ^-/e^+e^-)$ ratio, nor provides an important hadronic con…
Drawing analogy of replacing the nucleon by heavy chiral quark $Q$, the pion by Goldstone boson $G$, and $πNN$ coupling by $GQQ$ coupling, we construct a statistical model for $Q\bar Q \to nG$ annihilation, i.e. into $n$ longitudinal weak bosons. This analogy is becoming prescient since the LHC direct bound $m_Q > 611$ GeV implies strong Yukawa coupling. Taking $m_Q \in (1, 2)$ TeV, the mean number $<n_G>$ ranges from 6 to over 10, with negligible two or three boson production. With individual $t'$ or $b'$ decays suppressed either by phase space or quark mixing, and given the strong Yukawa cou…
We find model-independent upper limits on rates of dark matter annihilation in galactic halos. The Born approximation generally fails, while exotic threshold enhancements akin to "Sommerfeld factors" also turn out to be baseless The most efficient annihilation mechanism involves perturbatively small decay widths that have largely been ignored. Widths that are very small compared to TeV mass scales suffice to effectively saturate unitarity bounds on annihilation rates. Bound state formation in weakly coupled theories produces small effects due to wave function normalizations. Unitarity shows th…
We search for signals of Weak Annihilation in inclusive semileptonic D decays. We consider both the widths and the lepton energy moments, which are quite sensitive probes. Our analysis of Cleo data shows no clear evidence of Weak Annihilation, and allows us to put bounds on their relevance in charmless B semileptonic decays.
We consider the propagation and energy losses of protons and anti-protons produced by dark matter annihilation at redshifts 100<z<~2000. In the case of dark matter annihilations into quarks, gluons and weak gauge bosons, protons and anti-protons carry about 20% of the energy injected into e^\pm and γ's, but their interactions are normally neglected when deriving cosmic microwave background bounds from altered recombination histories. Here, we follow numerically the energy-loss history of typical protons/antiprotons in the cosmological medium. We show that about half of their energy is channele…
The computation of the energy spectra of Standard Model particles originated from the annihilation/decay of dark matter particles is of primary importance in indirect searches of dark matter. We compute how the inclusion of electroweak corrections significantly alter such spectra when the mass M of dark matter particles is larger than the electroweak scale: soft electroweak gauge bosons are copiously radiated opening new channels in the final states which otherwise would be forbidden if such corrections are neglected. All stable particles are therefore present in the final spectrum, independen…
We show that a Dirac right-handed scalar neutrino can be weakly interacting massive particle in the neutrinophilic Higgs model. When the additional Higgs fields couple only to the leptonic sector through neutrino Yukawa couplings, the right number of relic density of dark matter can be obtained from thermal freeze-out of the dark matter annihilation into charged leptons and neutrinos. At present, this annihilation is suppressed by the velocity of dark matter. However one-loop annihilation cross section into $γγ$ can be larger than that of the helicity suppressed annihilation into fermions, bec…
We consider dark matter (DM) with very weak couplings to the standard model (SM), such that its self-annihilation cross section is much smaller than the canonical one, $\langleσv\rangle_{χχ} \ll 10^{-26}\mathrm{cm}^3/\mathrm{s}$. In this case DM self-annihilation is negligible for the dynamics of freeze-out and DM dilution is solely driven by efficient annihilation of heavier accompanying dark sector particles provided that DM maintains chemical equilibrium with the dark sector. This chemical equilibrium is established by conversion processes which require much smaller couplings to be efficien…
Dark matter in the solar system II: WIMP annihilation rates in the Sun
我们计算了太阳中弱相互作用大质量粒子（WIMP）的湮灭率随其质量和弹性散射截面的变化。湮灭的副产品之一，μ子中微子，可能会被下一代中微子望远镜观测到。先前对湮灭率的估计假设来自银河系暗晕的任何WIMP被太阳核的弹性散射捕获，并在太阳中迅速达到热平衡。我们表明，太阳的光学深度WIMP和行星的引力都有助于降低湮灭率低于这些估计。虽然我们发现，即将到来的km^3级中微子望远镜对~100 GeV WIMP的灵敏度与之前的估计几乎没有变化，但这些实验对~10 TeV WIMP的灵敏度可能比标准计算所建议的要低一个数量级。湮灭率的新估计将指导未来的实验设计，并改善从中微子事件率到WIMP参数空间的映射。
We systematically study models with light scalar and pseudoscalar dark matter candidates and their potential signals at the LHC. First, we derive cosmological bounds on models with the Standard Model Higgs mediator and with a new weak-scale mediator. Next, we study two processes inspired by the indirect and direct detection process topologies, now happening inside the LHC detectors. We find that LHC can observe very light dark matter over a huge mass range if it is produced in mediator decays and then scatters with the detector material to generate jets in the nuclear recoil.
The extragalactic gamma-ray and neutrino emission may have a contribution from dark matter (DM) annihilations. In the case of discrepancies between observations and standard predictions, one could infer the DM pair annihilation cross section into cosmic rays by studying the shape of the energy spectrum. So far all analyses of the extragalactic DM signal have assumed the standard cosmological model (LambdaCDM) as the underlying theory. However, there are alternative DM scenarios where the number of low-mass objects is significantly suppressed. Therefore the characteristics of the gamma-ray and …
Recent observations suggest that some high-velocity clouds may be confined by massive dark matter halos. In particular, the proximity and proposed dark matter content of the Smith Cloud make it a tempting target for the indirect detection of dark matter annihilation. We argue that the Smith Cloud may be a better target than some Milky Way dwarf spheroidal satellite galaxies and use gamma-ray observations from the Fermi Large Area Telescope to search for a dark matter annihilation signal. No significant gamma-ray excess is found coincident with the Smith Cloud, and we set strong limits on the d…
