arXiv subjects

Ying Li

Publications and source records attributed to Ying Li.

At least 613 records · Page 34Linked to original sources

arXiv2010

Testing the Non-universal Z^\prime Model in Bs -> ϕπ^0 Decay

The branching ratio and direct CP asymmetry of the decay mode $B_s \to ϕπ^0$ have been calculated within the QCD factorization approach in both the standard model (SM) and the non-universal $Z^\prime$ model. In the standard model, the CP averaged branching ratio is about $1.3\times 10^{-7}$. Considering the effect of $Z^\prime$ boson, we found the branching ratio can be enlarged three times or decreased to one third %by the effect of $Z^\prime$ boson within the allowed parameter spaces. Furthermore, the direct CP asymmetry could reach 55% with a light $Z^\prime$ boson and suitable CKM phase, compared to 25% predicted in the SM. The enhancement of both branching ratio and CP asymmetry cannot be realized at the same parameter spaces, thus, if this decay mode is measured in the upcoming LHC-b experiment and/or Super B-factories, the peculiar deviation from the SM may provide a signal of the non-universal $Z^\prime$ model, which can be used to constrain the mass of $Z^\prime$ boson in turn.

hep-ph↗

arXiv2010

Annihilation-Type Charmless Radiative Decays of B Meson in Non-universal Z^\prime Model

We study charmless pure annihilation type radiative B decays within the QCD factorization approach. After adding the vertex corrections to the naive factorization approach, we find that the branching ratios of $\bar{B}^0_d\toϕγ$, $\bar{B}^0_s\toρ^0γ$ and $\bar{B}^0_s\toωγ$ within the standard model are at the order of $\mathcal{O}(10^{-12})$, $\mathcal{O}(10^{-10})$ and $\mathcal{O}(10^{-11})$, respectively. The smallness of these decays in the standard model makes them sensitive probes of flavor physics beyond the standard model. To explore their physics potential, we have estimated the contribution of $Z^\prime$ boson in the decays. Within the allowed parameter space, the branching ratios of these decay modes can be enhanced remarkably in the non-universal $Z^\prime$ model: The branching ratios can reach to $\mathcal{O}(10^{-8})$ for $\bar B_s^0 \to ρ^0(ω)γ$ and $\mathcal{O}(10^{-10})$ for the $\bar B_d^0 \to ϕγ$, which are large enough for LHC-b and/or Super B-factories to detect those channels in near future. Moreover, we also predict large CP asymmetries in suitable parameter space. The observation of these modes could in turn help us to constrain the $Z'$ mass within the model.

hep-ph↗

arXiv2009

Study of Decay Modes B -->K_0^*(1430) phi

Within the framework of perturbative QCD approach based on $\mathbf{k_T}$ factorization, we investigate the charmless decay mode $B \to K_0^*(1430)ϕ$. Under two different scenarios (S1 and S2) for the description of scalar meson $K_0^*(1430)$, we explore the branching fractions and related CP asymmetries. Besides the dominant contributions from the factorizable emission diagrams, penguin operators in the annihilation diagrams could also provide considerable contributions. The central values of our predictions are larger than those from the QCD factorization in both scenarios. Compared with the experimental measurements of the BaBar collaboration, the result of neutral channel in the S1 agrees with experimental data, while the result of the charged one is a bit smaller than the data. In the S2 scenario, although the central value for the branching fractions of both channels are much larger than the data, the predictions could agree with the data due to the large uncertainties to the branching fractions from the hadronic input parameters. The CP asymmetry in the charged channel is small and not sensitive to CKM angle $γ$. With the accurate data in near future from the various $B$ factories, these predictions will be under stringent tests.

hep-ph↗

arXiv2009

Artificial quantum-dot Helium molecules: Electronic spectra, spin structures, and Heisenberg clusters

Energy spectra and spin configurations of a system of N=4 electrons in lateral double quantum dots (quantum dot Helium molecules) are investigated using exact diagonalization (EXD), as a function of interdot separation, applied magnetic field (B), and strength of interelectron repulsion. As a function of the magnetic field, the energy spectra exhibit a low-energy band consisting of a group of six states, with the number six being a consequence of the conservation of the total spin and the ensuing spin degeneracies for four electrons. The energies of the six states appear to cross at a single value of the magnetic field, and with increasing Coulomb repulsion they tend to become degenerate, with a well defined energy gap separating them from the higher-in-energy excited states. The appearance of the low-energy band is a consequence of the formation of a Wigner supermolecule, with the four electrons (two in each dot) being localized at the vertices of a rectangle. Using spin-resolved pair-correlation distributions, a method for mapping the complicated EXD many-body wave functions onto simpler spin functions associated with a system of four localized spins is introduced. Detailed interpretation of the EXD spin functions and EXD spectra associated with the low-energy band via a 4-site Heisenberg cluster (with B-dependent exchange integrals) is demonstrated. Aspects of spin entanglement, referring to the well known N-qubit Dicke states, are also discussed.

cond-mat.mes-hall↗

arXiv2009

Buffer gas induced collision shift for the $^{88}$Sr $\bf{^1S_0-^3P_1}$ clock transition

Precision saturation spectroscopy of the $^{88}{\rm Sr} ^1S_0-^3P_1$ is performed in a vapor cell filled with various rare gas including He, Ne, Ar, and Xe. By continuously calibrating the absolute frequency of the probe laser, buffer gas induced collision shifts of $\sim $kHz are detected with gas pressure of 1-20 mTorr. Helium gave the largest fractional shift of $1.6 \times 10^{-9} {\rm Torr}^{-1}$. Comparing with a simple impact calculation and a Doppler-limited experiment of Holtgrave and Wolf [Phys. Rev. A {\bf 72}, 012711 (2005)], our results show larger broadening and smaller shifting coefficient, indicating effective atomic loss due to velocity changing collisions. The applicability of the result to the $^1S_0-^3P_0$ optical lattice clock transition is also discussed.

physics.atom-ph↗

arXiv2009

Exact results for the criticality of quench dynamics in quantum Ising models

Based on the obtained exact results we systematically study the quench dynamics of a one-dimensional spin-1/2 transverse field Ising model with zero- and finite-temperature initial states. We focus on the magnetization of the system after a sudden change of the external field and a coherent time-evolution process. With a zero-temperature initial state, the quench magnetic susceptibility as a function of the initial field strength exhibits strongly similar scaling behaviors to those of the static magnetic susceptibility, and the quench magnetic susceptibility as a function of the final field strength shows a discontinuity at the quantum critical point. This discontinuity remains robust and always occurs at the quantum critical point even for the case of finite-temperature initial systems, which indicates a great advantage of employing quench dynamics to study quantum phase transitions.

cond-mat.stat-mech↗

arXiv2009

Exact Analysis of Scaling and Dominant Attractors Beyond the Exponential Potential

By considering the potential parameter $Γ$ as a function of another potential parameter $λ$[47], We successfully extend the analysis of two-dimensional autonomous dynamical system of quintessence scalar field model to the analysis of three-dimension, which makes us be able to research the critical points of a large number of potentials beyond the exponential potential exactly. We find that there are ten critical points in all, three points $P_{3, 5, 6}$} are general points which are possessed by all quintessence models regardless of the form of potentials and the rest points are closely connected to the concrete potentials. It is quite surprising that, apart from the exponential potential, there are a large number of potentials which can give the scaling solution when the function $f(λ)(=Γ(λ)-1)$ equals zero for one or some values of $λ_{*}$ and if the parameter $λ_{*}$ also satisfies the condition Eq.(16) or Eq.(17) at the same time. We give the differential equations to derive these potentials $V(ϕ)$ from $f(λ)$. We also find that, if some conditions are satisfied, the de-Sitter-like dominant point $P_4$ and the scaling solution point $P_9$(or $P_{10}$) can be stable simultaneously but $P_9$ and $P_{10}$ can not be stable simultaneity. Although we survey scaling solutions beyond the exponential potential for ordinary quintessence models in standard general relativity, this method can be applied to other extensively scaling solution models studied in literature[46] including coupled quintessence, (coupled-)phantom scalar field, k-essence and even beyond the general relativity case $H^2 \proptoρ_T^n$. we also discuss the disadvantage of our approach.

hep-th↗

arXiv2009

Unparticle-Induced Lepton Flavor Violating Decays τ^- ->l^- (V^0, ~P^0)

We make an evaluation of the lepton flavor violating (LFV) decays $τ\to \ell (V^0, P^0)$, where $\ell=e$ or $μ$ and $V^0(P^0)$ is a neutral vector (pseudo-scalar) meson, in the context of unparticle physics. The constraints are investigated systematically on the related coupling parameters from all the available experimental data, and the parameter values are specified appropriately. The results show that whereas over the whole parameter space allowed by experiments all the $τ\to \ell P^0$ modes have a branching ratio too small to be measurable experimentally, in a large subspace as observed all of the $τ\to \ell V^0$ modes get simultaneously a branching ratio as high as ${\cal O}(10^{-10}-10^{-8})$, which is reachable at the LHC and super B factory. The important implications are drawn.

hep-ph↗

arXiv2009

Understanding B -->J/Ψϕin the Standard Model

The rare decay $\bar B_d^0\to J/ψϕ$ can proceed in four distinct mechanisms: (i) production of the $ϕ$ via tri-gluon fusion, (ii) photoproduction of the $J/ψ$ or $ϕ$, (iii) final-state rescattering of $D_s^{(*)}D_s^{(*)}$ produced in the $\bar B_d$ decay to $J/ψϕ$, and (iv) production of the $ϕ$ via $ω-ϕ$ mixing. In this work, we examine the contributions from photoproduction and final-state rescattering to $\bar B_d^0\to J/ψϕ$ and find that the corresponding branching ratios are of order $10^{-11}$ and $10^{-9}$, respectively. Hence, this decay is dominated by the $ω-ϕ$ mixing effect.

hep-ph↗

arXiv2009

Excitation spectra, spin structures, and entanglement characteristics of four-electron double-quantum-dot artificial molecules

Energy spectra, spin configurations, and entanglement characteristics of a system of four electrons in lateral double quantum dots are investigated using exact diagonalization (EXD), as a function of interdot separation, applied magnetic field, and strength of interelectron repulsion. A distinctly different quantum behavior is found compared to that of circular single quantum dots. As a function of the magnetic field, the energy spectra exhibit a low-energy band consisting of a group of six states, with the number six being a consequence of the conservation of the total spin of the four electrons and the ensuing spin degeneracies. These six states appear to cross at a single value of the magnetic field, with the crossing point becoming sharper for larger interdot distances. As the strength of the Coulomb repulsion increases, the six states tend to become degenerate and a well defined energy gap separates them from the higher-in-energy excited states. The appearance of the low-energy band is a consequence of the formation of a Wigner supermolecule, with the four electrons (two in each dot) being localized at the vertices of a rectangular parallelogram. Using the spin-resolved pair-correlation functions, one can map the EXD many-body wave functions onto the spin functions associated with the four localized electrons. Analogies with nanomagnets, such as finite Heisenberg clusters, are discussed. The ability to determine associated spin functions enables investigations concerning entanglement properties of the system of four electrons. In particular, the formation of Wigner supermolecules generates EXD solutions belonging to the class of strongly entangled states referred to as N-qubit Dicke states in the quantum-information literature.

cond-mat.mes-hall↗

arXiv2009

Revisiting B->phi pi Decays in the Standard Model

In the standard model (SM), we re-investigate the rare decay $B\to ϕπ$, which has been viewed as an ideal probe to detect the new physics signals beyond the SM. Contributions in the naive factorization method, the radiative corrections, the long-distance contributions, and the contributions due to the $ω$-$ϕ$ mixing are taken into account. We find that the tiny branching ratio in the naive factorization can be dramatically enhanced by the radiative corrections and the $ω$-$ϕ$ mixing effect, while the long-distance contributions are negligibly small. Assuming the Cabibbo-Kobayashi-Maskawa angle $γ=(58.6\pm 10)^\circ$ and the mixing angle $θ= -(3.0\pm 1.0)^\circ$, we obtain the branching ratios of $B\to ϕπ$ as $ {\rm Br}(B^\pm\to ϕπ^\pm)= (3.2 ^{+0.8-1.2}_{-0.7+1.8}) \times 10^{-8}$ and $ {\rm Br}(B^0 \to ϕπ^0) = (6.8 ^{+0.3-0.7}_{-0.3+1.0}) \times 10^{-9}$. If the future experiment reports a branching ratio of order $10^{-7}$ for $B^-\to ϕπ^-$ decay, it may not be a clear signal for any new physics scenario. In order to discriminate the large new physics contributions and those due to the $ω$-$ϕ$ mixing, we propose to measure the ratio of branching fractions of the charged and neutral B decay channel. We also study the direct CP asymmetries of these two channels, and the results are about $(-8.0^{+0.9+1.5}_{-1.0-0.1})%$ and $(-6.3^{-0.5+2.5}_{+0.7-2.5})%$ for $B^\pm\to ϕπ^\pm$ and $B^0 \to ϕπ^0$, respectively.

hep-ph↗

arXiv2008

Functioning of the dimeric GABA(B) receptor extracellular domain revealed by glycan wedge scanning

The G-protein-coupled receptor (GPCR) activated by the neurotransmitter GABA is made up of two subunits, GABA(B1) and GABA(B2). GABA(B1) binds agonists, whereas GABA(B2) is required for trafficking GABA(B1) to the cell surface, increasing agonist affinity to GABA(B1), and activating associated G proteins. These subunits each comprise two domains, a Venus flytrap domain (VFT) and a heptahelical transmembrane domain (7TM). How agonist binding to the GABA(B1) VFT leads to GABA(B2) 7TM activation remains unknown. Here, we used a glycan wedge scanning approach to investigate how the GABA(B) VFT dimer controls receptor activity. We first identified the dimerization interface using a bioinformatics approach and then showed that introducing an N-glycan at this interface prevents the association of the two subunits and abolishes all activities of GABA(B2), including agonist activation of the G protein. We also identified a second region in the VFT where insertion of an N-glycan does not prevent dimerization, but blocks agonist activation of the receptor. These data provide new insight into the function of this prototypical GPCR and demonstrate that a change in the dimerization interface is required for receptor activation.

q-bio.NC↗

arXiv2008

Rare Decays of Λ_b->Λ+ γand Λ_b ->Λ+ l^{+} l^{-} in the Light-cone Sum Rules

Within the Standard Model, we investigate the weak decays of $Λ_b \to Λ+ γ$ and $Λ_b \to Λ+ l^{+} l^{-}$ with the light-cone sum rules approach. The higher twist distribution amplitudes of $Λ$ baryon to the leading conformal spin are included in the sum rules for transition form factors. Our results indicate that the higher twist distribution amplitudes almost have no influences on the transition form factors retaining the heavy quark spin symmetry, while such corrections can result in significant impacts on the form factors breaking the heavy quark spin symmetry. Two phenomenological models (COZ and FZOZ) for the wave function of $Λ$ baryon are also employed in the sum rules for a comparison, which can give rise to the form factors approximately 5 times larger than that in terms of conformal expansion. Utilizing the form factors calculated in LCSR, we then perform a careful study on the decay rate, polarization asymmetry and forward-backward asymmetry, with respect to the decays of $Λ_b \to Λγ$, $Λl^{+}l^{-}$.

hep-ph↗

arXiv2008

Partners of Z(4430) and Productions in B Decays

Recently, Belle Collaboration has reported a resonant state produced in $B\to K πψ'$, which is called Z(4430). This state is charged, so it can not be interpreted as an ordinary charmonium state. In this paper, we analyze the octet to which this particle belongs and predict the masses of mesons in this octet. Utilizing flavor SU(3) symmetry, we study production rates in several kinds of B decays. The $\bar B^0\to Z_s^-π^+\to K^-ψ'π^+$ and $B^-\to \bar Z_s^0 π^-\to K_Sψ'π^-$ decay channels, favored by Cabibbo-Kobayashi-Maskawa (CKM) matrix elements, can have branching ratios of ${\cal O}(10^{-5})$. This large branching ratio could be observed at the running $B$ factories to detect $Z_s$ particles containing a strange quark. We also predict large branching ratios of the $Z$ and $Z_c$ ($\bar cc\bar c D, D=u,d,s$) particle production rates in non-leptonic $B_c$ decays and radiative B decays. Measurements of these decays at the ongoing $B$ factories and the forthcoming Large Hadron Collider (LHC)-b experiments are helpful to clarify the mysterious $Z$ particles.

hep-ph↗

arXiv2008

Probing Mott lobes via the AC Josephson effect

The alternating-current (AC) Josephson effect is studied in a system consisting of two weakly coupled Bose Hubbard models. In the framework of the mean field theory, Gross-Pitaevskii equations show that the amplitude of the Josephson current is proportional to the product of superfluid order parameters. In addition, the chemical potential--current relation for a small size system is obtained via the exact numerical computation. This allows us to propose a feasible experimental scheme to measure the Mott lobes of the quantum phase transition.

quant-ph↗

arXiv2008

Study Pure Annihilation Decays $B_s^0(\bar B_s^0)\to D^{\pm}π^{\mp}$ in PQCD Approach

The rare decays $B_s^0\to D^\pm π^\mp$ and $\bar B_s^0\to D^\mp π^\pm$ can occur only via annihilation type diagrams in the standard model. In this paper, we calculate branching ratios of these decays in perturbative QCD approach ignoring soft final state interaction. From our calculation, we find that their branching ratios are at $\mathcal{O}(10^{-6})$ with large CP asymmetry, which may be measured in LHC-b experiment in future.

hep-ph↗

arXiv2008

Photon-like flying qubit in the coupled cavity array

We propose a feasible scheme to realize a spin network via a coupled cavity array with the appropriate arrangement of external multi-driving lasers. It is demonstrated that the linear photon-like dispersion is achievable and this property opens up the possibility of realizing the pre-engineered spin network which is beneficial to quantum information processing.

quant-ph↗

arXiv2007

Study of Pure Annihilation Decays B_{d,s} \to D^{0} \bar D^{0}

With heavy quark limit and hierarchy approximation $λ_{QCD}\ll m_D\ll m_B$, we analyze the $B\to D^0\bar D^0$ and $B_s\to D^0\bar D^0$ decays, which occur purely via annihilation type diagrams. As a roughly estimation, we calculate their branching ratios and CP asymmetries in Perturbative QCD approach. The branching ratio of $B\to D^0\bar D^0$ is about $3.8\times10^{-5}$ that is just below the latest experimental upper limit. The branching ratio of $B_s\to D^0\bar D^0$ is about $6.8\times10^{-4}$, which could be measured in LHC-b. From the calculation, it could be found that this branching ratio is not sensitive to the weak phase angle $γ$. In these two decay modes, there exist CP asymmetries because of interference between weak and strong interaction. However, these asymmetries are too small to be measured easily.

hep-ph↗