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Register a new userHow to understand the underlying structures of $X(4140)$, $X(4274)$, $X(4500)$ and $X(4700)$
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Authors
Xiao-Hai Liu
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We investigate the possible rescattering effects which may contribute to the process $B^+to J/psiphi K^+$. It is shown that the $D_{s}^{*+}D_{s}^-$ rescattering via the open-charmed meson loops, and $psi^prime phi$ rescattering via the $psi^prime K_1$ loops may simulate the structures of $X(4140)$ and $X(4700)$, respectively. However, if the quantum numbers of $X(4274)$ ($X(4500)$) are $1^{++}$ ($0^{++}$), it is hard to to ascribe the observation of $X(4274)$ and $X(4500)$ to the $P$-wave threshold rescattering effects, which implies that $X(4274)$ and $X(4500)$ could be genuine resonances. We also suggest that $X(4274)$ may be the conventional orbitally excited state $chi_{c1}(3P)$.
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In this work, the $S$- and $P$-wave $bar{D}^ast K^ast$ interactions are studied in a coupled-channel formalism to understand the recently observed $X_0(2900)$ and $X_1(2900)$ at LHCb. The experimental event distributions can be well described, and two states with $I(J^P)=0(0^+)$ and $0(1^-)$ are yielded in an unified framework with the same set of parameters. Their masses and widths are determined to be $[m,Gamma]_{0^+}=[2873.2^{+10.8}_{-12.2},72.2^{+9.6}_{-8.3}]$ MeV and $[m,Gamma]_{1^-}=[2905.6^{+14.6}_{-10.7},52.5_{-1.3}^{+9.5}]$ MeV from the pole analyses, respectively. The masses of the $0^+$ and $1^-$ states are consistent with the experimental data, but the width of the $0^+$ state is larger than that of the $1^-$ one. The $X_1(2900)$ can be interpreted as the $P$-wave excitation of the ground-state $X_0(2900)$ in the hadronic molecular picture. The $S$- and $P$-wave multiplets in the $bar{D}^ast K^ast$ system have many members, so the present peak in the $D^-K^+$ invariant mass distributions might contain multi subpeaks. In order to probe the fine structures behind the single whole peak now, more refined measurements in the $B^+to D^+D^-K^+$ decay channel are necessary.
For the last decade numerous researchers have been trying to develop experimental techniques to use X-ray Thomson scattering as a method to measure the temperature, electron density, and ionization state of high energy density plasmas such as those used in inertial confinement fusion. With the advent of the X-ray free electron laser (X-FEL) at the SLAC Linac Coherent Light Source (LCLS) we now have such a source available in the keV regime. One challenge with X-ray Thomson scattering experiments is understanding how to model the scattering for partially ionized plasmas. Most Thomson scattering codes used to model experimental data greatly simplify or neglect the contributions of the bound electrons to the scattered intensity. In this work we take the existing models of Thomson scattering that include elastic ion-ion scattering and the electron-electron plasmon scattering and add the contribution of the bound electrons in the partially ionized plasmas. Except for hydrogen plasmas almost every plasma that is studied today has bound electrons and it is important to understand their contribution to the Thomson scattering, especially as new X-ray sources such as the X-FEL will allow us to study much higher Z plasmas. Currently most experiments have looked at hydrogen or beryllium. We will first look at the bound electron contributions to beryllium by analysing existing experimental data. We then consider several higher Z materials such as Cr and predict the existence of additional peaks in the scattering spectrum that requires new computational tools to understand. For a Sn plasma we show that the bound contributions changes the shape of the scattered spectrum in a way that would change the plasma temperature and density inferred by the experiment.
Inspired by the newly observed state $X^{*}(3860)$, we analyze the strong decay behaviors of some charmonium-like states $X^{*}(3860)$,$X(3872)$, $X(3915)$, $X(3930)$ and $X(3940)$ by the $^{3}P_{0}$ model. We carry out our work based on the hypothesis that these states are all being the charmonium systems. Our analysis indicates that $0^{++}$ charmonium state can be a good candidate for $X^{*}(3860)$ and $1^{++}$ state is the possible assignment for $X(3872)$. Considering as the $3^{1}S_{0}$ state, the decay behavior of $X(3940)$ is inconsistent with the experimental data. So, we can not assign $X(3940)$ as the $3^{1}S_{0}$ charmonium state by present work. Besides, our analysis imply that it is reasonable to assign $X(3915)$ and $X(3930)$ to be the same state, $2^{++}$. However, combining our analysis with that of Zhou~cite{ZhouZY}, we speculate that $X(3915)$/$X(3930)$ might not be a pure $coverline{c}$ systems.
A search for the X(4140) state in B+ to J/psi phi K+ decays is performed with 0.37 fb-1 of pp collisions at sqrt(s)=7 TeV collected by the LHCb experiment. No evidence for this state is found, in 2.4 sigma disagreement with a measurement by CDF. An upper limit on its production rate is set, BR(B+ to X(4140) K+) BR(X(4140) to J/psi phi) / BR(B+ to J/psi phi K+) < 0.07 at 90% confidence level.
Using the QCD spectral sum rule approach we investigate different currents with $J^{PC}=1^{++}$, which could be associated with the $X(3872)$ meson. Our results indicate that, with a four-quark or molecular structure, it is very difficult to explain the narrow width of the state unless the quarks have a special color configuration.
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