Searching for New physics in Charm Radiative decays
Aritra Biswas, Sanjoy Mandal, Nita Sinha
备注：
26 pages, 3 figures. Few references added and some typos corrected. Figures 2 and 3 replaced by new figures. Modifications in the text discussing the figures. Conclusions largely unchanged
We show that for a heavy vector-like quark model with a down type isosinglet, branching ratio for $c\rightarrow uγ$ decay is enhanced by more than $\mathcal{O}(10^2)$ as compared to that in the Standard model when QCD corrections to next-to-leading order are incorporated. In a left-right symmetric model (LRSM) along with a heavy vector-like fermion, enhancement of this order can be achieved at the bare (QCD uncorrected) level itself. We propose that a measurement of the photon polarization could be used to signal the presence of such new physics inspite of the large long distance effects. We find that there is a large region within the allowed parameter space of model with vector-like quark with additional left-right symmetry, where depending on the exact size of the long distance contribution, the photon polarization can be dominantly right-handed.
It is proposed to search for $C\!P$ violation through the two-fold angular distributions in the four-body decays of bottom and charmed hadrons. The two polar angles in the two-fold angular distributions are correlated, to which the interferences of intermediate resonances are one important origin. These interferences will leave tracks in the two-fold angular distributions, with which the $C\!P$ violation can be studied. Special attention is paid to the case when all the intermediate resonances are different, which is unique to four-body decays. It is suggested to look for $C\!P$ violation in f…
Motivated by very recent measurement of the radiative decays of $Υ(1S)$ to $χ_{c1}$ at Belle, we use the nonrelativistic QCD factorization theory and calculate the branching fractions of the radiative decays of bottomonium into S-wave and P-wave charmonium, i.e. $Υ(nS) \to η_c(nS)+γ$ and $Υ(nS)\to χ_{cJ}+γ$. We systematically studied the branching fractions of the radiative decays of bottomonium into charmonium. Compared to the previous calculation, we obtained the analytical expression for the decay widths and considered the color-octet contributions. For $Υ(nS) \to η_c(nS)+γ$, the relativist…
Searching for hidden-charm baryonium signals in QCD sum rules
本文对夸克含量为$u\bar u d\bar d c\bar c$、自旋为$J=0/1/2/3$、宇称为正宇称和负宇称的隐魅重子态进行了QCD求和规则研究。我们系统地构造了相应的局域隐魅重子素内插流，它可以耦合到各种结构，包括隐魅重子素态、隐魅重子素态加两个π介子、隐魅四夸克态加一个π介子等。我们起初不知道这些流耦合到哪种结构，但通过求和规则分析，我们可以得到一些信息。我们发现它们中的一些可以耦合到隐魅重子态，并由此估算了最低能级的隐魅重子态的质量，其量子数为$J^P=2^-/3^-/0^+/1^+/2^+$，约为5.0 GeV.我们建议在这个能区的$D$波$J/ψππ$和$P$波$J/ψρ$和$J/ψω$通道中寻找重子的隐魅态，特别是$J=3^-$的隐魅态.
结合重夸克有效理论和手征拉格朗日方法，我们研究了D介子的辐射衰变。首先，我们重新分析$D^{*} \rightarrow D γ$衰变使用重夸克自旋对称性，手征对称性拉格朗日，但也包括轻矢量介子。然后，我们计算分支比$D \rightarrow V γ$。本文对Cabbibo抑制的$D \to ρ/ ωγ$衰变和$D \rightarrow P P γ$衰变的分支比作了一些评论。
The $c \to u γ$ Contribution to Weak Radiative Charm Decay
$c \to u γ$转换不会发生在标准模型的树级别，并且在一个循环中受到强烈的GIM抑制。已知领先的QCD振幅可以提高两个数量级。我们指出，振幅进一步增加了两个数量级后，包括完整的2圈QCD的贡献。尽管如此，粲强子的$ΔS =0$辐射衰变仍然由$c \to d \bar{d} u γ$和$c \to s \bar{s} u γ$夸克子过程控制。
We study the photon spectrum in the radiative decays of the charmonium $\frac{1}Γ\frac{dΓ(J/ψ\rightarrowγgg)}{dz}$ as an excellent scene for hunting the exotic mesons (hybrids $q\bar{q}g$ and glueballs $gg$) and an ideal frame for the theoretical and phenomenological investigations of the gluon nature in IR, by subtle estimation of its non-zero effective mass which seems required in Quark-Gluon Constituent Model (QGCM) for identifying the nature of these exotic species.
Using the dynamical diquark model, we calculate the electric-dipole radiative decay widths to $X(3872)$ of the lightest negative-parity exotic candidates, including the four $I=0$, $J^{PC} \! = \! 1^{--}$ ("$Y$") states. The $O$(100--1000 keV) values obtained test the hypothesis of a common substructure shared by all of these states. We also calculate the magnetic-dipole radiative decay width for $Z_c(4020)^0 \! \to \! γX(3872)$, and find it to be rather smaller ($<$~10 keV) than its predicted value in molecular models.
Testing the predicted dynamically generated hidden charm $X$ scalar state through the $D\bar D$ invariant mass spectrum and the radiative decay of the $ψ(3770)$
在这项工作中，我们提出了我们的模型，动态产生共振的魅力和轻的赝标量和矢量介子。该模型产生了丰富的频谱的魅力和隐藏的魅力标量和轴向共振，其中大部分可以与观察到的状态。其他国家的预测，特别是一个隐藏的魅力标量共振质量接近$D\bar D$阈值。对于这种共振，我们提出的计算表明，观察到的增强在$D\bar D$质谱测定贝尔在反应中产生$D\bar D J/ψ$在最终状态可以起源于这个预测的状态。我们还提出了理论计算的辐射衰减宽度的$ψ(3770)$到这个状态。预测的分支分数表明，这种预测的状态可以观察到的BES在$ψ(3770)$峰运行一年的统计。
