arXiv subjects

Jiang Yi

Publications and source records attributed to Jiang Yi.

At least 19 recordsLinked to original sources

arXiv2024

Channel Estimation Considerate Precoder Design for Multi-user Massive MIMO-OFDM Systems: The Concept and Fast Algorithms

The sixth-generation (6G) communication networks target peak data rates exceeding 1Tbps, necessitating base stations (BS) to support up to 100 simultaneous data streams. However, sparse pilot allocation to accommodate such streams poses challenges for users' channel estimation. This paper presents Channel Estimation Considerate Precoding (CECP), where BS precoders prioritize facilitating channel estimation alongside maximizing transmission rate. To address the computational complexity of 6G large-scale multi-input multi-output (MIMO) systems, we propose a computationally-efficient space-time block diagonal channel shortening (ST-BDCS) precoding scheme. By leveraging the sparse Toeplitz property of orthogonal frequency division multiplexing (OFDM) channels, this time-domain precoding design effectively mitigates multi-user interference in the downlink and shortens the effective channel's temporal length. Consequently, users can estimate the channels using sparse pilots. To enable fast implementation, we develop a generalized complex-valued Toeplitz matrix QR decomposition algorithm applicable to various space-time signal processing problems. Simulation results demonstrate that the ST-BDCS precoding method approximates the rate performance of conventional subcarrier-by-subcarrier precoding schemes. However, it offers the advantages of easier channel estimation for users and significantly reduced computational complexity for the BS.

cs.IT↗

arXiv2021

A Parallel Scalable Domain Decomposition Preconditioner for Elastic Crack Simulation Using XFEM

In this paper, a parallel overlapping domain decomposition preconditioner is proposed to solve the linear system of equations arising from the extended finite element discretization of elastic crack problems. The algorithm partitions the computational mesh into two types of subdomains: the regular subdomains and the crack tip subdomains based on the observation that the crack tips have a significant impact on the convergence of the iterative method while the impact of the crack lines is not that different from those of regular mesh points. The tip subdomains consist of mesh points at crack tips and all neighboring points where the branch enrichment functions are applied. The regular subdomains consist of all other mesh points, including those on the crack lines. To overcome the mismatch between the number of subdomains and the number of processor cores, the proposed method is divided into two steps: solve the crack tip problem and then the regular subdomain problem during each iteration. The proposed method was used to develop a parallel XFEM package which is able to test different types of iterative methods. To achieve good parallel efficiency, additional methods were introduced to reduce communication and to maintain the load balance between processors. Numerical experiments indicate that the proposed method significantly reduces the number of iterations and the total computation time compared to the classical methods. In addition, the method scales up to 8192 processor cores with over 70\% parallel efficiency to solve problems with more than $2\times10^8$ degrees of freedom.

cs.CE↗

arXiv2017

Photoproduction of the $B_c^{(*)}$ Meson at the LHeC

We make a detailed study on the photoproduction mechanism of the doubly heavy flavored $B_c^{(*)}$ meson at the purposed Large Hadron Electron Collider (LHeC) within the framework of nonrelativistic QCD. In addition to the photoproduction mechanism via the gluon-induced channel $γ+ g \to B_c^{(*)} + b + \bar{c}$, the extrinsic heavy quark mechanism via the two channels $γ+ c \to B_c^{(*)} + b $ and $γ+ \bar{b} \to B_c^{(*)} + \bar{c}$ has also been studied. Those two extrinsic channels are generally suppressed by the heavy quark distribution functions in proton, which however provide significant contributions in low and intermediate $p_T$ region. A detailed comparison of those channels together with the theoretical uncertainties has been presented. By summing up all the mentioned photoproduction channels, we observe that about $(1.04^{+0.90}_{-0.53})\times 10^{5}$ $B_c$ and $(4.86^{+3.72}_{-2.30})\times 10^{5}$ $B_c^*$ events can be generated at the LHeC in one operation year with the proton-electron collision energy $\sqrt{S}=1.30$ TeV and the luminosity ${\mathcal L}\simeq 10^{33}$ ${\rm cm}^{-2} {\rm s}^{-1}$. Here the errors are for $m_c=1.50\pm0.20$ GeV and $m_b=4.9\pm0.40$ GeV. Thus, in addition to the hadronic experiments, the LHeC shall provide another helpful platform for studying the $B_c^{(*)}$ meson properties, especially to test the extrinsic heavy quark mechanism.

hep-ph↗

arXiv2007

Revisiting the QCD corrections to the R-parity violating processes $p\bar{p}/pp \to eμ+X$

We present the theoretical predictions up to QCD NLO for the cross section of high-mass electron-muon pair production at the Tevatron and the LHC, considering only the dominant contributions from the third-generation sneutrino. The dependence of the renormalization and factorization scales on the total cross section, and the effects on the K-factor due to the uncertainty of parton distribution function(PDF) have been carefully investigated. By considering soft-gluon resummation effects to all order in $α_s$ of leading logarithm, we present the transverse momentum distributions of the final $eμ$ pair.

hep-ph↗

arXiv2007

QCD corrections to t\bar t b \bar b productions via photon-photon collisions at linear colliders

We calculated the complete next-to-leading order(NLO) QCD corrections to the $t\bar t b \bar b$ production process at a $γγ$ collider in the standard model(SM). The calculation of the one-loop QCD correction includes the evaluations of the hexagon and pentagon amplitudes. We studied the NLO QCD corrected total cross section, the distributions of transverse momenta of final top- and bottom-quark states, and the dependence of the cross section on renormalization scale $μ$. It shows that NLO QCD correction generally increases the LO cross section in our chosen parameter space, and the K-factor varies from 1.70 to 1.14 when colliding energy goes up from $400 GeV$ to $2 TeV$. We find that the correction distinctly changes the distributions of transverse momenta of the final top- and bottom-quark states, and the NLO QCD correction obviously improves the independence of the cross section for process $γγ\to t\bar t b\bar b$ on the renormalization scale.

hep-ph↗

arXiv2007

The effects of the little Higgs models on $t\bar{t} h^0$ production via $γγ$ collision at linear colliders

In the frameworks of the littlest Higgs($LH$) model and its extension with T-parity($LHT$), we studied the associated $t\bar th^0$ production process $e^+ e^- \to γγ\to t \bar t h^0$ at the future $e^+e^-$ linear colliders up to QCD next-to-leading order. We present the regions of $\sqrt{s}-f$ parameter space in which the $LH$ and $LHT$ effects can and cannot be discovered with the criteria assumed in this paper. The production rates of process $γγ\to t \bar t h^0$ in different photon polarization collision modes are also discussed. We conclude that one could observe the effects contributed by the $LH$ or $LHT$ model on the cross section for the process $e^+ e^- \to γγ\to t \bar t h^0$ in a reasonable parameter space, or might put more stringent constraints on the $LH$/$LHT$ parameters in the future experiments at linear colliders.

hep-ph↗

arXiv2007

Flavor changing effects on single charged Higgs boson production associated with a bottom-charm pair at CERN Large Hadron Collider

We study flavor changing effects on the \ppbchT process at the Large Hadron Collider(LHC), which are inspired by the left-handed up-type squark mixings in the Minimal Supersymmetric Standard Model(MSSM). We find that the SUSY QCD radiative corrections to $bcH^\pm$ coupling can significantly enhance the cross sections at the tree-level by a factor about $1.5 \sim 5$ with our choice of parameters. We conclude that the squark mixing mechanism in the MSSM makes the \ppbchT process a new channel for discovering a charged Higgs boson and investigating flavor changing effects.

hep-ph↗

arXiv2007

Full one-loop electroweak corrections to $h^0(H^0,A^0) H^\pm W^\mp$ associated productions at $e^+e^-$ linear colliders

We study the complete one-loop electroweak(EW) corrections to the processes of single charged Higgs boson production associated with a neutral Higgs boson$(h^0,H^0,A^0)$ and a gauge boson $W^\pm$ in the framework of the minimal supersymmetric standard model(MSSM). Numerical results at the ${\rm SPS1a'}$ benchmark point as proposed in the SPA project, are presented for demonstration. We find that for the process $e^+e^-\to h^0H^\pm W^\mp$ the EW relative correction can be either positive or negative and in the range of $-15%\sim 20%$ in our chosen parameter space. While for the processes $e^+e^-\to H^0(A^0)H^\pm W^\mp$ the corrections generally reduce the Born cross sections and the EW relative corrections are typically of order $-10%\sim -20%$.

hep-ph↗

arXiv2006

QCD corrections to the R-parity violating processes $p\bar{p}/pp \to eμ+X$ at hadron colliders

We present the QCD corrections to the processes $p\bar{p}/pp \to eμ+X$ at the Tevatron and the CERN large hadron collider(LHC). The numerical results show that variation of K factor is in the range between $1.28(1.32)$ and $1.79(1.58)$ at the Tevatron(LHC). We find that the QCD correction part from the one-loop gluon-gluon fusion subprocess is remarkable at the LHC and should be taken into account.

hep-ph↗

arXiv2006

The annihilation decays $B^-_c \to η^{'}(η,π^0) l^- \barν$

We investigate the simileptonic OZI-forbidden annihilation decays $B^-_c \to η^{'}(η,π^0) l^- \barν$ for $l=μ,e$ in the perturbative QCD, and carry out a precise calculation without any approximation for the one-loop contributions, which involves integrals of 4- and 5-point loop functions. Our results show that the branching ratios of decays $B^-_c \to η^{'} l^- \barν$, $B^-_c \to ηl^- \barν$ and $B^-_c \to π^0 l^- \barν$, turn out to be of orders $10^{-4}$, $10^{-5}$ and $10^{-6}$, respectively, which could be observable in the future experiments at the LHC.

hep-ph↗

arXiv2006

Electroweak radiative corrections to the Higgs-boson production in association with $Z^0$-boson pair at $e^+ e^-$ colliders

We present the full ${\cal O}(α_{ew})$ electroweak radiative corrections to the Higgs-boson production in association with $Z^0$-boson pair at an electron-positron linear collider(LC) in the standard model. We analyze the dependence of the full one-loop corrections on the Higgs-boson mass $m_{H}$ and colliding energy $\sqrt{s}$. We find that the corrections significantly suppress the Born cross section, and the ${\cal O}(α_{ew})$ electroweak radiative corrections are generally between 1.0% and -15% in our chosen parameter space, which should be taken into consideration in the future precise experiments.

hep-ph↗

arXiv2006

Full one-loop electroweak and NLO QCD corrections to the associated production of chargino and neutralino at hadron colliders

We study the process of the association production of chargino and neutralino including the NLO QCD and the complete one-loop electroweak corrections in the framework of the minimal supersymmetric standard model(MSSM) at the Fermilab Tevatron and the CERN Large Hadron Collider (LHC). In both the NLO QCD and one-loop electroweak calculations we apply the algorithm of the phase-space slicing(PSS) method. We find that the NLO QCD corrections generally increase the Born cross sections, while the electroweak relative corrections decrease the Born cross section in most of the chosen parameter space. The NLO QCD and electroweak relative corrections typically have the values of about 32% and -8% at the Tevatron, and about 42% and -6% at the LHC respectively. The results show that both the NLO QCD and the complete one-loop electroweak corrections to the processes $p \bar p/pp \to \widetildeχ_1^{\pm} \widetildeχ_2^0+X$ are generally significant and should be taken into consideration in precision experimental analysis.

hep-ph↗

arXiv2006

NLO supersymmetric QCD corrections to the $t \bar b H^-$ associated production at hadron colliders

We present the next-to-leading order QCD corrected total cross sections and the distributions of the transverse momenta of the final anti-bottom-quark, top-quark and charged Higgs-boson for the processes of $p\bar p/pp \to t\bar b H^-+X$ in the minimal supersymmetric standard model(MSSM) at the Tevatron and the LHC. We find that the NLO QCD corrections significantly modify the leading-order distributions of the transverse momenta of final particles($p_T^b$, $p_T^t$ and $p_T^{H^-}$), and the total NLO QCD corrections reduce the dependence of the cross section on the renormalization and factorization scales, especially the NLO QCD corrected cross sections at the LHC are nearly independent of these scales. Our results show that the relative correction is obviously related to $m_{H^-}$ and $\tanβ$, and the total NLO QCD relative corrections can be beyond -50% at the Tevatron and approach -40% at the LHC in our chosen parameter space.

hep-ph↗

arXiv2005

Full one-loop supersymmetric corrections to charged Higgs boson pair production in $γγ$ collisions

The complete one-loop electroweak corrections to charged Higgs boson pair production in $γγ$ collision mode at linear colliders in the minimal supersymmetric standard model (MSSM), are calculated in this paper. We discuss the dependence of the corrections to the subprocess $γγ\to H^{+}H^{-}$ on the related parameters, such as the colliding energy, charged Higgs boson mass $M_{H^{\pm}}$ and some supersymmetric parameters $\tan β$, $M_{SUSY}$ and gaugino mass parameter $M_2$. We find that the corrections generally reduce the Born cross sections and the relative one-loop corrections to both the subprocess typically in the range of -10% to -30%. We also present the numerical results at the SPS1a' point from the SPA project. We conclude that the full one-loop electroweak corrections to subprocess $γγ\to H^{+}H^{-}$ and the parent process $e^+e^- \to γγ\to H^{+}H^{-}$ are significant and therefore should be considered in precise analysis of charged Higgs boson pair productions via $γγ$ collision at future linear colliders.

hep-ph↗

arXiv2005

Full one-loop supersymmetric electroweak corrections to $t\bar{t}h^{0}$ associated production in $e^+e^-$ annihilation

We present a precise calculation of the lightest neutral Higgs boson production associated with top quark pair at a linear collider. The full one-loop electroweak ${\cal O}(α_{ew})$ contributions to the process $e^+e^- \to t\bar t h^0$ within the minimal supersymmetric standard model (MSSM) are included. We analyze the dependence of the electroweak corrections on the MSSM parameters such as $M_{A^0}$, $\tanβ$, $M_2$, $A_{f}$, $M_{SUSY}$ and $μ$. The results show that the full one-loop electroweak radiative corrections turn out to be about -20% quantitatively and thus are important for future $e^+e^-$ linear colliders.

hep-ph↗

arXiv2005

NLO Supersymmetric QCD Corrections to $t \bar t h^0$ Associated Production at Hadron Colliders

We calculate NLO QCD corrections to the lightest neutral Higgs boson production associated with top quark pair at hadron colliders in the minimal supersymmetric standard model(MSSM). Our calculation shows that the total QCD correction significantly reduces its dependence on the renormalization/factorization scale. The relative correction from the SUSY QCD part approaches to be a constant, if either $M_S$ or $m_{\tilde{g}}$ is heavy enough. The corrections are generally moderate(in the range of few percent to 20%) and under control in most of the SUSY parameter space. The relative correction is obviously related to $m_{\tilde{g}}$, $A_t$ and $μ$, but not very sensitive to $\tanβ$, $M_S$ at both the Tevatron and the LHC with our specified parameters.

hep-ph↗

arXiv2005

Pair Production of Charged Higgs Bosons from Bottom-Quark Fusion

For very large values of $\tanβ$, charged Higgs boson pair production at the Large Hadron Collider (LHC) from the scattering of two bottom quarks can proceed dominantly. We investigated the cross sections of charged Higgs boson pair production via the subprocess $b\bar{b} \to H^+H^-$ at the LHC including the next-to-leading order (NLO) QCD corrections in the minimal supersymmetric standard model (MSSM). We find that the NLO QCD corrections can significantly reduce the dependence of the cross sections on the renormalization and factorization scales.

hep-ph↗

arXiv2005

The effects of large extra dimensions on associated $t\bar{t} h^0$ production at linear colliders

In the framework of the large extra dimensions (LED) model, the effects of LED on the processes \rrtth and \eetth at future linear colliders are investigated in both polarized and unpolarized collision modes. The results show that the virtual Kaluza-Klein (KK) graviton exchange can significantly modify the standard model expectations for these processes with certain polarizations of initial states. The process \rrtth with $\sqrt{s}=3.5 TeV$ allows the effective scale $Λ_T$ to be probed up to 7.8 and 8.6 TeV in the unpolarized and $P_γ = 0.9$, J=2 polarized $γγ$ collision modes, respectively. For the \eetth process with $\sqrt{s}=3.5 TeV$, the upper limits of $Λ_T$ to be observed can be 6.7 and 7.0 TeV in the unpolarized and $P_{e^+} = 0.6$, $P_{e^-} = 0.8$, $-+$ polarized $e^+e^-$ collision modes, respectively. We find the \rrtth channel in J=2 polarized photon collision mode provides a possibility to improve the sensitivity to the graviton tower exchange.

hep-ph↗