arXiv subjects

Jiao Zhang

Publications and source records attributed to Jiao Zhang.

31 records · Page 2Linked to original sources

arXiv2018

Progress in the Construction and Testing of the Tianlai Radio Interferometers

The Tianlai Pathfinder is designed to demonstrate the feasibility of using a wide field of view radio interferometers to map the density of neutral hydrogen in the Universe after the Epoch of Reionizaton. This approach, called 21~cm intensity-mapping, promises an inexpensive means for surveying the large-scale structure of the cosmos. The Tianlai Pathfinder presently consists of an array of three, 15~m $\times$ 40~m cylinder telescopes and an array of sixteen, 6~m diameter dish antennas located in a radio-quiet part of western China. The two types of arrays were chosen to determine the advantages and disadvantages of each approach. The primary goal of the Pathfinder is to make 3D maps by surveying neutral hydrogen over large areas of the sky %$20,000 {\rm deg}^2$ in two different redshift ranges: first at $1.03 > z > 0.78$ ($700 - 800$~MHz) and later at $0.21 > z > 0.12$ ($1170 - 1270$~MHz). The most significant challenge to $21$~cm intensity-mapping is the removal of strong foreground radiation that dwarfs the cosmological signal. It requires exquisite knowledge of the instrumental response, i.e. calibration. In this paper, we provide an overview of the status of the Pathfinder and discuss the details of some of the analysis that we have carried out to measure the beam function of both arrays. We compare electromagnetic simulations of the arrays to measurements, discuss measurements of the gain and phase stability of the instrument, and provide a brief overview of the data processing pipeline.

astro-ph.IM↗

arXiv2017

Realization of $U_q({\mathfrak{sp}}_{2n})$ within the Differential Algebra on Quantum Symplectic Space

We realize the Hopf algebra $U_q({\mathfrak {sp}}_{2n})$ as an algebra of quantum differential operators on the quantum symplectic space $\mathcal{X}(f_s;\mathrm{R})$ and prove that $\mathcal{X}(f_s;\mathrm{R})$ is a $U_q({\mathfrak{sp}}_{2n})$-module algebra whose irreducible summands are just its homogeneous subspaces. We give a coherence realization for all the positive root vectors under the actions of Lusztig's braid automorphisms of $U_q({\mathfrak {sp}}_{2n})$.

math.RT↗

arXiv2016

Sky reconstruction for the Tianlai cylinder array

In this paper, we apply our sky map reconstruction method for transit type interferometers to the Tianlai cylinder array. The method is based on the spherical harmonic decomposition, and can be applied to cylindrical array as well as dish arrays and we can compute the instrument response, synthesised beam, transfer function and the noise power spectrum. We consider cylinder arrays with feed spacing larger than half wavelength, and as expected, we find that the arrays with regular spacing have grating lobes which produce spurious images in the reconstructed maps. We show that this problem can be overcome, using arrays with different feed spacing on each cylinder. We present the reconstructed maps, and study the performance in terms of noise power spectrum, transfer function and beams for both regular and irregular feed spacing configurations.

astro-ph.IM↗

arXiv2016

Sky reconstruction from transit visibilities: PAON-4 and Tianlai Dish Array

The spherical harmonics $m$-mode decomposition is a powerful sky map reconstruction method suitable for radio interferometers operating in transit mode. It can be applied to various configurations, including dish arrays and cylinders. We describe the computation of the instrument response function, the point spread function (PSF), transfer function, the noise covariance matrix and noise power spectrum. The analysis in this paper is focused on dish arrays operating in transit mode. We show that arrays with regular spacing have more pronounced side lobes as well as structures in their noise power spectrum, compared to arrays with irregular spacing, specially in the north-south direction. A good knowledge of the noise power spectrum $C^{\mathrm{noise}}(\ell)$ is essential for intensity mapping experiments as non uniform $C^{\mathrm{noise}}(\ell)$ is a potential problem for the measurement of the HI power spectrum. Different configurations have been studied to optimise the PAON-4 and Tianlai dish array layouts. We present their expected performance and their sensitivities to the 21-cm emission of the Milky Way and local extragalactic HI clumps

astro-ph.IM↗

arXiv2013

Rare baryonic decays $Λ_b \to Λl^+ l^-$ in the TTM model

In the framework of the top triangle moose $(TTM)$ model, we analyze the rare decays $Λ_{b}\rightarrow Λl^{+}l^{-} (l=e,μ,τ)$ by using the form factors calculated in full $QCD$. We calculate the contributions of the new particles predicted by this model to observables, such as the branching ratios, forward-backward asymmetry ($A_{FB}$) and polarizations related these decay processes. We find that, in wide range of the parameter space, the values of the branching ratios are enhanced by one order of magnitude comparing to the $SM$ predictions. This model can also produce significant corrections to $A_{FB}$, normal polarization $P_N$ and transversal polarization $P_T$.

hep-ph↗

arXiv2012

Pair production of the heavy leptons associated with a gauge boson gamma or Z at the ILC

The T-odd leptons are the typical particles predicted by the littlest Higgs model with T-parity (LHT model) and the observation of these particles might be regarded as the direct evidence of the LHT model. In this paper, we investigate the production of a pair of T-odd leptons associated with a gauge boson $V$($γ$ or $Z$) at the international linear $e^{+}e^{-}$ collider (ILC). The numerical results show that the possible signals of the T-odd leptons may be detected in the future ILC experiments.

hep-ph↗

arXiv2012

Photoproduction of the charged top-pions at the LHeC

The top triangle moose $(TTM)$ model, which can be seen as the deconstructed version of the topcolor-assisted technicolor ($TC2$) model, predicts the existence of the charged top-pions $ π_{t}^{\pm}$ in low energy spectrum. In the context of this model, we consider photoproduction of $π^{\pm}_{t}$ via the subprocesses $γb\to t π_{t}^{-}$ and $γ\bar{b}\to \bar{t} π_{t}^{+}$ at the large hadron-electron collider ($LHeC$), in which high energy photon beams are generated by using the Compton backscatting method. We find that, as long as the charged top-pions are not too heavy, they can be abundantly produced via $γb$ collision.

hep-ph↗

arXiv2010

Rare decays B\to Mν\barν in the TC2 model and the LHT model

In the framework of the topcolor-assisted technicolor ($TC2$) model and the littlest Higgs model with $T$-parity ($LHT$ model), we consider the rare B decays $B\to Mν\barν$ with $M=π,K,ρ,$ or $K^{\ast}$. We find that the contributions of the $TC2$ model to the branching ratios of these decay processes are larger than those for the $LHT$ model. The experimental upper limits for some branching ratios can give severe constraints on the free parameters of the $TC2$ model.

hep-ph↗

arXiv2010

Lepton flavor violating signals of the LHT model via e^{+}e^{-} and γγcollisions at the ILC

Taking into account the constraints on the free parameters of the littlest Higgs model with T-parity (called $LHT$ model) from some rare decay processes, such as $μ\rightarrow eγ$ and $μ\rightarrow 3e$, we consider the contributions of the $LHT$ model to the lepton flavor violating ($LFV$) processes $e^{+}e^{-}\rightarrow l_{i}\bar{l}_{j}$ and $γγ\rightarrow l_{i}\bar{l}_{j}$ ($i\neq j$). We find that the $LHT$ model can indeed produce significant contributions to these $LFV$ processes and its $LFV$ signal might has a chance of being observed in the future $ILC$ experiments.

hep-ph↗

arXiv2010

Single production of the doubly charged Higgs boson via eγcollision in the Higgs triplet model

The Higgs triplet model (HTM) predicts the existence of a pair of doubly charged Higgs bosons $H^{\pm \pm}$. Single production of $H^{\pm \pm}$ via e collision at the next generation e+e- International Linear Collider (ILC) and the Large Hadron electron Collider (LHeC) is considered. The numerical results show that the production cross sections are very sensitive to the neutrino oscillation parameters. Their values for the inverted hierarchy mass spectrum are larger than those for the normal hierarchy mass spectrum at these two kinds of collider experiments. With reasonable values of the relevant free parameters, the possible signals of the doubly charged Higgs bosons predicted by the HTM might be detected in future ILC experiments.

hep-ph↗

arXiv2010

Cyclic Homology of Strong Smash Product Algebras

For any strong smash product algebra $A\#_{_R}B$ of two algebras $A$ and $B$ with a bijective morphism $R$ mapping from $B\ot A$ to $A\ot B$, we construct a cylindrical module $A\natural B$ whose diagonal cyclic module $Δ_{\bullet}(A\natural B)$ is graphically proven to be isomorphic to $C_{\bullet}(A\#_{_R}B)$ the cyclic module of the algebra. A spectral sequence is established to converge to the cyclic homology of $A\#_{_R}B$. Examples are provided to show how our results work. Particularly, the cyclic homology of the Pareigis' Hopf algebra is obtained in the way.

math.QA↗

arXiv2010

Lepton flavor violation decays $τ^-\to μ^- P_1 P_2$ in the topcolor-assisted technicolor model and the littlest Higgs model with $T$ parity

The new particles predicted by the topcolor-assisted technicolor ($TC2$) model and the littlest Higgs model with T-parity (called $LHT$ model) can induce the lepton flavor violation ($LFV$) couplings at tree level or one loop level, which might generate large contributions to some $LFV$ processes. Taking into account the constraints of the experimental data on the relevant free parameters, we calculate the branching ratios of the $LFV$ decay processes $τ^-\toμ^- P_1 P_2 $ with $P_1 P_2$ = $π^+π^-$, $K^+K^-$ and $K^0\bar{K^0}$ in the context of these two kinds of new physics models. We find that the $TC2$ model and the $LHT$ model can indeed produce significant contributions to some of these $LFV$ decay processes.

hep-ph↗

arXiv2010

Quantum Quasi-Shuffle Algebras

We establish some properties of quantum quasi-shuffle algebras. They include the necessary and sufficient condition for the construction of the quantum quasi-shuffle product, the universal property, and the commutativity condition. As an application, we use the quantum quasi-shuffle product to construct a linear basis of $T(V)$, for a special kind of Yang-Baxter algebras $(V,m,σ)$.

math.QA↗