arXiv subjects

Meng Shi

Publications and source records attributed to Meng Shi.

25 records · Page 2Linked to original sources

arXiv2019

Multipartite entanglement of fermionic system in accelerated frames

We investigate the entanglement measures of tripartite W-State and GHZ-state in noninertial frame through the coordinate transformation between Minkowski and Rindler. First it is shown that all three qubits undergo in a uniform acceleration $a$ of W-State, we find that the one-tangle, two-tangle, and $π$-tangle decrease when the acceleration parameter $r$ increases, and the two-tangle cannot arrive to infinity of the acceleration. Next we show that the one qubit goes in a uniform acceleration $a_{1}$ and the other two undergo in a uniform acceleration $a$ of GHZ-state, we find that the two-tangle is equal to zero and $N_{B_I (A_I C_I)} = N_{C_I (A_I B_I)}\neq N_{A_I (B_I C_I)}$, but one-tangle and $π$-tangle never reduce to zero for any acceleration.

quant-ph↗

arXiv2019

Constraints on $U(1)_{L_μ-L_τ}$ from LHC Data

In this study, we apply LHC data to constrain the extension of the Standard Model by an anomaly-free $U(1)_{L_μ-L_τ}$ gauge group; this model contains a new gauge boson ($Z^\prime$) and a scalar dark matter particle ($ϕ_{\rm DM}$). We recast a large number of LHC analyses from ATLAS and CMS of multi-lepton final states. We find that for $10$ GeV $< m_{Z^\prime} < 60$ GeV the strongest constraint comes from a dedicated $Z^\prime$ search in the $4μ$ final state by the CMS collaboration; for larger $Z^\prime$ masses, searches for final states with three leptons plus missing $E_T$ are more sensitive. Searches for final states with two leptons and missing $E_T$, which are sensitive to $Z^\prime$ decays into dark matter particles, can only probe regions of parameter space that are excluded by searches in the $3$ and $4$ lepton channels. The combination of LHC data excludes values of $Z^\prime$ mass and coupling constant that can explain the deficit in $g_μ-2$ for $4$ GeV $\leq m_{Z^\prime} \leq 500$ GeV. However, for much of this range the LHC bound is weaker than the bound that can be derived from searches for trident events in neutrino-nucleus scattering.

hep-ph↗

arXiv2018

Excluded volume effect in flexible dendrimer systems: A self-consistent field theory

We have studied the conformational and scaling behaviors of a flexible dendrimer immersed in athermal or good solvents. A self-consistent field theory combined with a pre-averaged excluded volume potential representing the two-body short-ranged interaction between the segments, was adopted to calculate the density profile of various generations and branch points thoroughly. Our calculation results support the "dense-core" model. We find the conformation of the dendrimer is strongly stretched in the dense central region, but much weakly stretched in the outer region where the segment density profile is shoulder shaped. Both our self-consistent field theory calculation and the Flory mean-field theory calculation give the same scaling law R proportional to (GP)^0.2N^0.4, where G is the generation number of the dendrimer, P is the spacer segment number, and N is the total segment number. If we fix G, the scaling law is simplified to R proportional to P^0.6 in good solvent.

cond-mat.soft↗

arXiv2015

Bootstrap Random Walks

Consider a one dimensional simple random walk $X=(X_n)_{n\geq0}$. We form a new simple symmetric random walk $Y=(Y_n)_{n\geq0}$ by taking sums of products of the increments of $X$ and study the two-dimensional walk $(X,Y)=((X_n,Y_n))_{n\geq0}$. We show that it is recurrent and when suitably normalised converges to a two-dimensional Brownian motion with independent components; this independence occurs despite the functional dependence between the pre-limit processes. The process of recycling increments in this way is repeated and a multi-dimensional analog of this limit theorem together with a transience result are obtained. The construction and results are extended to include the case where the increments take values in a finite set (not necessarily $\{-1,+1\}$).

math.PR↗

arXiv2015

On the Nature of X(4260)

We study the property of $X(4260)$ resonance by re-analyzing all experimental data available, especially the $e^+e^- \rightarrow J/ψ\,π^+π^-,\,\,\,ωχ_{c0}$ cross section data. The final state interactions of the $ππ$, $K\bar K$ couple channel system are also taken into account. A sizable coupling between the $X(4260)$ and $ωχ_{c0}$ is found. The inclusion of the $ωχ_{c0}$ data indicates a small value of $Γ_{e^+e^-}=23.30\pm 3.55$eV.

hep-ph↗

arXiv2014

A Refined Analysis on the $X(3872)$ Resonance

We study the property of the $X(3872)$ meson by analyzing the $B\to K D\bar D^*$ and $B\to K J/ψπ^+π^-$ decay processes. The competition between the rescattering mediated through a Breit-Wigner resonance and the rescattering generated from a local $D\bar{D}^* \to D\bar{D}^*$ interaction is carefully studied through an effective lagrangian approach. Three different fits are performed: pure Breit-Wigner case, pure $D\bar{D}^*$ molecule case with only local rescattering vertices (generated by the loop chain), and the mixed case. It is found that data supports the picture where X(3872) is mainly a ($\bar cc$) Breit-Wigner resonance with a small contribution to the self-energy generated by $\bar DD^*$ final state interaction. For our optimal fit, the pole mass and width are found to be: $M_X=3871.2\pm0.7$MeV and $Γ_X=6.5\pm1.2$MeV.

hep-ph↗

arXiv2013

Studies on X(4260) and X(4660) particles

Studies on the X(4260) and X(4660) resonant states in an effective lagrangian approach are reviewed. Using a Breit--Wigner propagator to describe their propagation, we find that the X(4260) has a sizable coupling to the $ωχ_{c0}$ channel, while other couplings are found to be negligible. Besides, it couples much stronger to $σ$ than to $f_0(980)$: $|g_{XΨσ}^2/g^2_{XΨf_0(980)}|\sim O(10) \ .$ As an approximate result for X(4660), we obtain that the ratio of $\frac{Br(X\rightarrowΛ_c^+Λ_c^-)}{Br(X\rightarrowΨ(2s)π^+π^-)}\simeq 20$. Finally, taking X(3872) as an example, we also point out a possible way to extend the previous method to a more general one in the effective lagrangian approach.

hep-ph↗