Is the $J^P=2^-$ assignment for the $X(3872)$ compatible with the radiative transition data?
Yu Jia, Wen-Long Sang, Jia Xu
备注：
v2; 14 pages, 3 tables; references, a new table and several footnotes added, text refined; a minus sign added for the definition of J1 in (14b), accordingly Table I and II and equations (21,22,23) are corrected to reflect this change, but the conclusion remains
The very recent analysis by BaBar Collaboration indicates that the $X(3872)$ may favor the quantum number $J^{PC}=2^{-+}$ rather than the previously assumed $1^{++}$. By pretending the $η_{c2}(1D)$ charmonium to be the $X(3872)$, we study the parity-even radiative transition processes $η_{c2}(1D)\to J/ψ(ψ')+γ$ within several phenomenological potential models. We take the ${}^3D_1$ admixture in $ψ'$ into account, and consider the contributions from the magnetic dipole ($M1$), electric quadrupole ($E2$), and magnetic octupole ($M3$) amplitudes. It is found that the ratio of the branching fractions of these two channels, as well as the absolute branching fraction of $η_{c2}\to ψ'γ$, are in stark contradiction with the existing \textsc{BaBar} measurements. This may indicate that the $2^{-+}$ assignment for the $X(3872)$ is highly problematic.
Assuming that $X(3872)$ is a mixture between $2P$ charmonium and $\bar{D}D^{*}$ molecular states with $J^{PC}=1^{++}$, an analysis of $X(3872)$ radiative decays into $J/ψγ$ and $ψ(2S)γ$ is presented. The modification of the radiative branching ratio due to possible constructive or destructive interferences between the meson-loop and the short-distance contact term, which is modeled by a charm quark loop, is shown. The model predictions are shown to be compatible with the experimentally determined ratio of the mentioned branching fractions for a wide range of the $X(3872)$ charmonium content. I…
Very recently, the LHCb Collaboration reported the doubly charmed tetraquark state $T_{cc}^+$ below the $D^{*+}D^0$ threshold about $273$ keV. As a very near-threshold state, its long-distance structure is very important. In the molecular scheme, we relate the coupling constants of $T_{cc}^+$ with $D^{*0}D^+$ and $D^{*+}D^0$ to its binding energy and mixing angle of two components with a coupled-channel effective field theory. With the coupling constants, we investigate the kinetically allowed strong decays $T_{cc}^+\to D^0D^0π^+$, $T_{cc}^+\to D^+D^0π^0$ and radiative decays $D^+D^0 γ$. Our r…
Radiative Signature of New Scalar Boson Decays in the $m_{\ell \ell γ}$ Spectrum at the LHC
University of the Witwatersrand（威特沃特斯兰德大学）；SGTB Khalsa College, University of Delhi（德里大学SGTB卡尔萨学院）；Universitat Autònoma de Barcelona（巴塞罗那自治大学）；ICREA, Institució Catalana de Recerca i Estudis Avançats（加泰罗尼亚高级研究学会）；Delhi School of Analytics, Institution of Eminence, University of Delhi（德里大学卓越机构德里分析学院）；Institute of High Energy Physics（高能物理研究所）
We study the strong and radiative decays of the radial excitation of the $ρ$ meson, with quantum numbers $n$ $^{2S+1}L_{J}=2$ $^{3}S_{1},$ $I=1$, and denoted as $ρ_{E}$, by making use of an effective model. We test different masses: $1.45$ GeV, corresponding to well known assignment $ρ_{E}\equivρ(1450)$ state; $1.25$ GeV for the assignment $ρ_{E}\equivρ(1250)$ (a resonance whose existence has not yet been confirmed), and $1.35$ GeV, which lies just in the middle between them in order to study the dependence of the results on the mass. The decay widths for different decay processes and two bran…
Is right-handed neutrino degeneracy compatible with the solar and atmospheric neutrino data?
根据最近的太阳和大气中微子数据，我们研究了重右手Majorana中微子在大统一尺度下具有精确简并谱的可能性。分析的上下文中进行的最小超对称标准模型与不间断的R-宇称和扩展与三个重马约拉纳中微子领域，以实现跷跷板机制。在没有狄拉克型轻子混合的情况下，轻子味破坏的唯一来源是右手中微子扇区。受夸克、带电轻子和狄拉克中微子汤川耦合矩阵之间的大统一理论关系的启发，在考虑了辐射效应后，我们确定了电弱尺度下的有效中微子质量矩阵.利用99% C. L.的太阳和大气数据的最新全球分析，我们的结论是，在这个框架内，唯一的太阳能解决方案兼容的实验数据是低和LMA解决方案，后者是最受欢迎的。在90% C.L.，只允许使用LMA解决方案。
A Roadmap for neutrino charge assignments in $U(2)_F$ Flavor Models: Implications for LFV processes and leptonic anomalous magnetic moments
Universitá di Roma Tre（罗马三大学）；INFN Sezione di Roma Tre（意大利国家核物理研究所罗马三分部）；Instituto de Física Corpuscular (IFIC), Universitat de València-CSIC（瓦伦西亚大学-西班牙国家科研委员会粒子物理研究所）
动力学部分子密度，产生的辐射从价输入在一些低分辨率的规模，面临着最近的小x深非弹性和其他硬散射过程的数据。结果表明，在理论的不确定性，我们以前（1994年）的动力学/辐射部分子分布与最近的数据是兼容的，仍然适用于目前可用的次领先阶计算的精度范围内的限制。由于最近的高精度测量，我们还提出了一个更新的，更准确的版本，我们的（类价）动态输入分布。此外，我们的微扰稳定的无参数动力学预言被推广到了极小x区域10^-8 ~< x ~< 10^-5，这与超高能宇宙线和中微子天文学有关。
J-PARC E05 reported recently a hint of a $Ξ^--{^{11}{\rm B}}$ nuclear state in the ${^{12}}{\rm C}(K^-,K^+){^{12}_Ξ}{\rm Be}$ spectrum, bound by $B_{Ξ^-}=8.9\pm 1.4 {^{+3.8}_{-3.1}}$ MeV. Using a density-dependent $Ξ$-nuclear optical potential $V_{\rm opt}^Ξ(ρ)$ we explore to what extent a $Ξ^-_{1s}$ assignment of this nuclear state is compatible with $Ξ^-_{1s}$ and $Ξ^-_{1p}$ nuclear-state interpretations of $Ξ^-$ capture events in light emulsion-nuclei experiments. We find that the only acceptable $Ξ^-_{1s}$ assignment at present, barring an abnormally strong repulsive $ρ^2$ component of $V_…
