The production cross sections of charmonia, charmonium-bottomonium and bottomonia pairs in a single boson $e^+e^-$ annihilation have been studied in a wide range of energies, which will be achieved at future $e^+e^-$ colliders such as ILC and FCC. One loop QCD corrections to QCD and EW contributions as well as their interference are considered. The both intermediate bosons $γ$ and $Z$ are taken into account.
Within the framework of nonrelativistic quark-antiquark Cornell potential model formalism, we study the annihilation of heavy quarkonia. We determine their annihilation widths resulting into digluon, dilepton, $3γ$, $3g$ and $γgg$ and compare our findings with the available theoretical results and experimental data. We also provide the charge radii and absolute square of radial Schrödinger wave function at zero quark-antiquark separation for heavy quarkonia and $B_c$ mesons.
We calculate the annihilation decay rates of the $^3D_2(2^{--})$ and $^3D_3(3^{--})$ charmonia and bottomonia by using the instantaneous Bethe-Salpeter method. The wave functions of states with quantum numbers $J^{PC}=2^{--}$ and $3^{--}$ are constructed. By solving the corresponding instantaneous Bethe-Salpeter equations, we obtain the mass spectra and wave functions of the quarkonia. The annihilation amplitude is written within Mandelstam formalism and the relativistic corrections are taken into account properly. This is important, especially for high excited states, since their relativistic…
In this work, the non-relativistic asymptotic behavior of the transition $q\overline{q}\rightarrow2g\rightarrow q\overline{q}$ in the $^1S_0$ channel is discussed. Different with the usual calculation which expands the physical amplitude around the quark anti-quark threshold, we take the quark anti-quark pairs as off shell and only expand the expression on the three-dimensional momenta of the quarks and anti-quarks. We calculate the results to order 6. The imagine part of the results after applying the on shell conditions can reproduce the non-relativistic QCD (NRQCD) results in leading order …
In this work, we calculate the nonrelativistic asymptotic behavior of the amplitudes of $q\overline{q}\rightarrow 2g \rightarrow q\overline{q}$ in the leading order of $α_s$ (LO-$α_s$) with $q\overline{q}$ in the $^3P_J$ channels. In the practical calculation we take the momenta of quarks and antiquarks on-shell and expand the amplitudes on the three-momentum of the quarks and antiquarks to order 6 and get three nonzero terms. The imaginary parts of the first term and the second term are the old. The real parts of the results have IR divergence. When applying the results to the heavy quarkonia…
Relativistic two-photon and two-gluon decay rates of heavy quarkonia
利用完全相对论性衰变振幅和一个复杂的重夸克偶素量子色动力学势模型，计算了$c\bar{c}$和$b\bar{b}$通过双光子或双胶子湮灭的衰变率。我们对1 S 0，3 P0和3 P2态的光子和胶子宽度的计算结果与现有的实验数据非常吻合。我们处理费米子-反费米子束缚态的方法和数学技巧也适用于其它衰变过程。
We improve the pNRQCD approach to annihilation processes of heavy quarkonium and make first pNRQCD predictions for exclusive electromagnetic production of heavy quarkonium. We consider strongly coupled quarkonia, i.e., quarkonia that are not Coulombic bound states. Possible strongly coupled quarkonia include excited charmonium and bottomonium states. For these, pNRQCD provides expressions for the decay and exclusive electromagnetic production NRQCD matrix elements that depend on the wavefunctions at the origin and few universal gluon field correlators. We compute electromagnetic decay widths a…
We improve the theoretical predictions for the decays of the Higgs boson to an $S$-wave vector quarkonium plus a photon by calculating the relativistic correction of order $v^2$, where $v$ is the heavy-quark velocity in the quarkonium rest frame. Our numerical results are given for the $J/ψ$ and $Υ(nS)$ channels, with $n=1,2,3$. The numerical results include a previously calculated correction of order $α_s$ and summations, to all orders in $α_s$, of leading logarithms of $m_H^2/m_Q^2$, where $m_H$ is the Higgs-boson mass and $m_Q$ is the heavy-quark mass. These QCD corrections apply to the con…
We address the impact of sterile fermions on the lepton flavor violating decays of quarkonia as well as of the $Z$ boson. We compute the relevant Wilson coefficients and show that the ${\rm B}(V\to\ell_α\ell_β)$, where $V=ϕ,ψ^{(n)}$, $Υ^{(n)},Z$ can be significantly enhanced in the case of large sterile fermion masses and a non-negligible active-sterile mixing. We illustrate that feature in a specific minimal realization of the inverse seesaw mechanism, known as $(2,3)$-ISS, and in an effective model in which the presence of non-standard sterile fermions is parameterized by means of one heavy …
Rare Higgs decays into a pair of heavy vector quarkonia, $h\to VV$ ($V=J/Ψ$, $Υ$ etc.), have been investigated in the standard model. Different from the past literature in which these decays are thought to be only dominated by the longitudinally polarized final states, we also include the transitions, which proceed through $h\to γ^*γ^*$/$h\to Vγ^*$, followed by $γ^*\to V$. The final vector quarkonia via these ways are dominantly transversely polarized. Our calculation however shows that these transitions could lead to significant contributions to the decay rate, especially for the charmonium f…
Within the standard model, we have investigated rare $Z$-boson decays into double heavy quarkonia, $Z\to VV$ and $Z\to VP$ with $V$ denoting vector and $P$ denoting pseudoscalar quarkonia, respectively. It is assumed that the leading-order QCD diagrams would give the dominant contributions to these processes, and the corresponding branching fractions, for instance, ${\cal B}(Z\to J/ΨJ/Ψ)$ has been estimated to be around $10^{-13}$ in the literature. However, these decays could also happen through the electromagnetic transition $Z\to Vγ^*$ and $Z\to Pγ^*$, with the virtual photon transforming i…
Cross sections for the concurrent production of pairs of quarkonia (J/psi, Upsilon) and/or gauge bosons (W, Z) from double-parton scatterings (DPS) in high-energy proton-nucleus and nucleus-nucleus collisions at the LHC are calculated. The estimates are based on next-to-leading-order perturbative QCD predictions, including nuclear modifications of the parton densities, for the corresponding single-scattering cross sections. Expected event rates for J/psi+J/psi, J/psi+Upsilon, J/psi+W, J/psi+Z, Upsilon+Upsilon, Upsilon+W, Upsilon+Z, and same-sign W+W production in their (di)leptonic decay modes…
In the current work, We investigated the production of neutral Higgs boson and two charged Charginos owing to electron-positron annihilation via different propagators
I present theoretical calculations for charged Higgs production in association with a $W$ boson via bottom quark annihilation. I discuss higher-order radiative corrections from collinear and soft gluon emission and show that they are important. I present theoretical results for total cross sections, and for transverse-momentum and rapidity distributions of the charged Higgs boson at LHC energies.
We calculate the leading order cross section for the associated production of Z and J/ψ. Processes that include associated production of electroweak bosons and heavy quarlonium can give valuable insight to the production mechanism of quarkonia. We conclude that this process is accessible by the LHC statistics.
The production cross sections of $J/ψ~η_b$, $Υ\;η_c$ pairs in a single boson $e^+e^-$ annihilation have been studied in a wide range of energies, which will be achieved at future $e^+e^-$ colliders. The main color singlet contributions to the production processes are taken into account, including the one loop QCD contribution.
Conventional versus single-ladder-splitting contributions to double parton scattering production of two quarkonia, two Higgs bosons and $c \bar c c \bar c$
计算并比较了不同两部分子组合的常规和部分子分裂的部分子分布。常规和分裂dPDF在$x_1$和$x_2$中具有非常相似的形状。本文首次定量计算了单梯分裂对两个S波或P波夸克偶、两个希格斯玻色子和$c \bar c c \bar c$的双部分子散射（DPS）产生的贡献。的比例的单梯分裂常规的贡献进行了讨论作为一个函数的质心能量，质量的生产系统和其他运动学变量。使用一个简单的模型的依赖于传统的两部分子分布的横向部分子分离（高斯和独立的$x_i$和标度），我们发现，2v1的贡献是一样大的2v2的贡献，近年来在文献中讨论。这意味着，$σ_{eff}$的唯象分析，只包括传统的DPS机制，必须加以修订，包括明确的单阶梯分裂的贡献这里讨论。然而，传统的和单阶梯分裂DPS过程计算的快度和横动量的微分分布是非常相似的，这导致他们的实验分离是相当困难的，如果不是不可能的。两个组件（常规和分裂）的存在的直接后果是能量和工艺依赖的经验参数$σ_{eff}$。这是说明在我们的文件中所考虑的过程。
Dark matter annihilations into two light fermions and one gauge boson: general analysis and antiproton constraints
本文研究了由Majorana粒子通过汤川耦合与轻标准模型费米子和额外标量耦合构成暗物质的情形。在这种情况下，轻费米子的湮灭率与调解的标量粒子强烈抑制费米子的质量。然而，螺旋度的抑制被规范玻色子的相关发射所解除，产生的湮灭率可能足够大，可以间接探测到暗物质粒子。我们对这种情况进行了一般性的分析，计算了当暗物质粒子为SU（2）_L单重态或二重态，f为轻子或夸克，V为光子、弱规范玻色子或胶子时，过程χχ \rightarrow f \bar f V的湮灭截面.我们指出，湮灭率是特别增强时，暗物质粒子是质量退化的中间标量粒子，这是一个场景几乎没有约束的碰撞搜索的外来带电或有色粒子。最后，我们从PAMELA测量的宇宙反质子-质子比的过量的非观测中推导出相关截面的上限。
It is well known that the annihilation of Majorana dark matter into fermions is helicity suppressed. Here, we point out that the underlying mechanism is a subtle combination of two distinct effects, and we present a comprehensive analysis of how the suppression can be partially or fully lifted by the internal bremsstrahlung of an additional boson in the final state. As a concrete illustration, we compute analytically the full amplitudes and annihilation rates of supersymmetric neutralinos to final states that contain any combination of two standard model fermions, plus one electroweak gauge bo…
We present theoretical analysis of paired $B_c$ mesons production in $e^+e^-$ annihilation at different energy scales taking into account full next-to-leading order QCD corrections. Both possible electroweak channels are considered: production via virtual photon and via virtual $Z$-boson. We study in detail the role of radiative QCD corrections, which were found to be significant especially at low energies. It is shown that the contribution from $Z$-boson is significant at high energies ($\sqrt{s} > M_Z/2$) especially in the case of paired production of pseudo-scalar and vector ($B_c + B_c^*$)…
Theory results on precision measurements in electron-positron annihilation at low and high energies are collected. These cover pure QCD calculations as well as mixed electroweak and QCD results, involving light and heavy quarks. The impact of QCD corrections on the $W$-boson mass is discussed and, last not least, the status and the perspectives for the Higgs boson decay rate into $b\bar b$, $c\bar c$ and into two gluons.
