arXiv subjects

Jun He

Publications and source records attributed to Jun He.

At least 343 records · Page 19Linked to original sources

arXiv2012

The roles of nucleon resonances in $Λ$(1520) photoproduciton off proton

In this work the roles of the nucleon resonances in the $Λ$(1520) photoproduction off proton target are investigated within the effective Lagrangian method. Besides the Born terms,including contact term, $s$-, $u$- and $K$ exchanged $t$-channels, vector meson $K^*$ exchanged $t-$channel is considered in our investigation, which is negligible at low energy and important at high energy. The important nucleon resonances predicted by the constituent quark model (CQM) are considered and the results are found well comparable with the experimental data. Besides the dominant $D_{13}(2080)$, the resonance $[\textstyle{5\over 2}^-]_2(2080)$ predicted by the CQM is found important to reproduce the experimental data. Other nucleon resonances are found to give small contributions in the channel considered in this work. With all important nucleon resonances predicted by CQM, the prediction of the differential cross section at the energy up to 5.5 GeV are presented also, which can be checked by the future CLAS experimental data.

nucl-th↗

arXiv2012

Few-Body Systems Composed of Heavy Quarks

Within the past ten years many new hadrons states were observed experimentally, some of which do not fit into the conventional quark model. I will talk about the few-body systems composed of heavy quarks, including the charmonium-like states and some loosely bound states.

hep-ph↗

arXiv2012

New structure around 3250 MeV in the baryonic B decay and the $D^*_0(2400)N$ molecular hadron

In this work, we first propose the isovector $nD^{*}_0(2400)^0$ molecular state to explain the enhancement structure around 3250 MeV ($X_c(3250)^0$) in the $Σ_c^{++}π^-π^-$ invariant mass spectrum newly observed by the BaBar Collaboration. Under this molecular state configuration, both the analysis of the mass spectrum and the study of its dominant decay channel can well depict its resonance parameters measured by BaBar. Our investigation also shows that the isovector $nD^{*}_0(2400)^0$ molecular state can decay into $Σ_c^{++}π^-π^-$, which is consistent with the experimental observation. These studies provide the direct support to the isovector $nD^{*}_0(2400)^0$ molecular state assignment to $X_c(3250)^0$.

hep-ph↗

arXiv2012

A hybrid artificial immune system and Self Organising Map for network intrusion detection

Network intrusion detection is the problem of detecting unauthorised use of, or access to, computer systems over a network. Two broad approaches exist to tackle this problem: anomaly detection and misuse detection. An anomaly detection system is trained only on examples of normal connections, and thus has the potential to detect novel attacks. However, many anomaly detection systems simply report the anomalous activity, rather than analysing it further in order to report higher-level information that is of more use to a security officer. On the other hand, misuse detection systems recognise known attack patterns, thereby allowing them to provide more detailed information about an intrusion. However, such systems cannot detect novel attacks. A hybrid system is presented in this paper with the aim of combining the advantages of both approaches. Specifically, anomalous network connections are initially detected using an artificial immune system. Connections that are flagged as anomalous are then categorised using a Kohonen Self Organising Map, allowing higher-level information, in the form of cluster membership, to be extracted. Experimental results on the KDD 1999 Cup dataset show a low false positive rate and a detection and classification rate for Denial-of-Service and User-to-Root attacks that is higher than those in a sample of other works.

cs.NE↗

arXiv2012

The open-charm radiative and pionic decays of molecular charmonium Y(4274)

In this work, we investigate the decay widths and the line shapes of the open-charm radiative and pionic decays of Y(4274) with the $D_s\bar{D}_{s0}(2317)$ molecular charmonium assignment. Our calculation indicates that the decay widths of $Y(4274)\to D^{+}_{s}D^{*-}_{s}γ$ and $Y(4274)\to D^+_{s}D^-_{s}π^0$ can reach up to 0.05 keV and 0.75 keV, respectively. In addition, the result of the line shape of the photon spectrum of $Y(4274)\to D_s^+ {D}_s^{*-} γ$ shows that there exists a very sharp peak near the large end point of photon energy. The line shape of the pion spectrum of $Y(4274)\to D_s^+ {D}_s^{*-} π^0$ is similar to that of the pion spectrum of $Y(4274)\to D_s^+ {D}_s^{*-} γ$, where we also find a very sharp peak near the large end point of pion energy. According to our calculation, we suggest further experiments to carry out the search for the open-charm radiative and pionic decays of Y(4274).

hep-ph↗

arXiv2011

Production of charmed baryon $Λ_c(2940)^+$ at PANDA

In this work we evaluate the production rate of the charmed baryon $Λ_c(2940)^+$ at PANDA. For possible assignments of $Λ_c(2940)^+$: $J^P=1/2^\pm$, $3/2^\pm$ and $5/2^\pm$, the total cross section of $p\bar{p}\to \barΛ_c Λ_c(2940)^+$ is estimated, which may exceed 1 nb. With the designed luminosity ($2\times10^{-32}$cm$^{-2}$/s) of PANDA, our estimate indicates that ten thousand events per day if $Λ_c(2940)^+$ is of $J^P=1/2^+$ or $10^8$ per day if it is of $J^P=5/2^+$ can be expected. Those values actually set the lower and upper limits of the $Λ_c(2940)^+$ production. In addition, we present the Dalitz plot and carry out a rough background analysis of the $Λ_c(2940)^+$ production in the $p\bar{p}\to D^0 p\barΛ_c$ and $p\bar{p}\to Σ_c^{0,++}π^{+,-}\barΛ_c$ processes, which would provide valuable information for accurate determination of the $Λ_c(2940)^+$ identity.

hep-ph↗

arXiv2011

The possible hidden-charm molecular baryons composed of anti-charmed meson and charmed baryon

With the one-boson-exchange model we have studied the possible existence of the very loosely bound hidden-charm molecular baryons composed of anti-charmed meson and charmed baryon. Our numerical results indicate that there exist $Σ_c\bar{D}^*$ states with $I(J^P)=1/2(1/2^-), 1/2(3/2^-), 3/2(1/2^-), 3/2(3/2^-)$ and $Σ_c\bar{D}$ state with $3/2(1/2^-)$. But the $Λ_c \bar{D}$ and $Λ_c \bar{D}^*$ molecular states do not exist.

hep-ph↗

arXiv2011

Online Robust Subspace Tracking from Partial Information

This paper presents GRASTA (Grassmannian Robust Adaptive Subspace Tracking Algorithm), an efficient and robust online algorithm for tracking subspaces from highly incomplete information. The algorithm uses a robust $l^1$-norm cost function in order to estimate and track non-stationary subspaces when the streaming data vectors are corrupted with outliers. We apply GRASTA to the problems of robust matrix completion and real-time separation of background from foreground in video. In this second application, we show that GRASTA performs high-quality separation of moving objects from background at exceptional speeds: In one popular benchmark video example, GRASTA achieves a rate of 57 frames per second, even when run in MATLAB on a personal laptop.

cs.IT↗

arXiv2011

Dipion invariant mass distribution of the anomalous $Υ(1S) π^{+} π^{-}$ and $Υ(2S) π^{+} π^{-}$ production near the peak of $Υ(10860)$

Considering the defects of the previous work for estimating the anomalous production rates of $e^+e^-\to Υ(1S)π^+π^-,\,Υ(2S)π^+π^-$ near the peak of the $Υ(5S)$ resonance at $\sqrt s=10.87$ GeV [K.F. Chen {\it et al}. (Belle Collaboration), Phys. Rev. Lett. {\bf 100}, 112001 (2008)], we suggest a new scenario where the contributions from the direct dipion transition and the final state interactions interfere to result in not only the anomalously large production rates, but also the lineshapes of the differential widths consistent with the experimental measurement when assuming the reactions are due to the dipion emission of $Υ(5S)$. At the end, we raise a new puzzle that the predicted differential width $dΓ(Υ(5S)\toΥ(2S)π^+π^-)/d\cosθ$ has a discrepant trend from the data while other predictions are well in accord with the data. It should be further clarified by more accurate measurements carried by future experiments.

hep-ph↗

arXiv2011

$Z_b(10610)^\pm$ and $Z_b(10650)^\pm$ as the $B^\bar{B}$ and $B^\bar{B}^{*}$ molecular states

In the framework of the one-boson-exchange model, we have studied the interaction of the $B^*\bar{B}$ and $B^*\bar{B}^{*}$ system. After considering the S-wave and D-wave mixing, we notice that both $Z_b(10610)^\pm$ and $Z_b(10650)^\pm$ can be interpreted as the $B^*\bar{B}$ and $B^*\bar{B}^{*}$ molecular states quite naturally. Within the same framework, there also exist several molecular charmonia including X(3872) and several other molecular bottomonia, which are the partners of $Z_b(10610)$ and $Z_b(10650)$. The long-range one-pion-exchange force alone is strong enough to form these loosely bound molecular states, which ensures the numerical results quite model-independent and robust.

hep-ph↗

arXiv2011

Exploration of hyperfine interaction between constituent quarks via eta productions

In this work, the different exchange freedom, one gluon, one pion or Goldstone boson, in constituent quark model is investigated, which is responsible to the hyperfine interaction between constituent quarks, via the combined analysis of the eta production processes, $π^{-}p\rightarrowηn$ and $γp\rightarrowηp$. With the Goldstone-boson exchange, as well as the one-gluon or one-pion exchange, both the spectrum and observables, such as, the differential cross section and polarized beam asymmetry, are fitted to the suggested values of Particle Data Group and the experimental data. The first two types of exchange freedoms give acceptable description of the spectrum and observables while the one pion exchange can not describe the observables and spectrum simultaneously, so can be excluded. The experimental data for the two processes considered here strongly support the mixing angles for two lowest S11 sates and D13 states as about -30 and 6 degree respectively.

nucl-th↗

arXiv2011

A novel explanation of charmonium-like structure in $e^+e^-\to ψ(2S)π^+π^-$

We first present a non-resonant description to charmonium-like structure $Y(4360)$ in the $ψ(2S)π^+π^-$ invariant mass spectrum of the $e^+e^-\to ψ(2S)π^+π^-$ process. The $Y(4360)$ structure is depicted well by the interference effect of the production amplitudes of $e^{+} e^{-} \to ψ(2S) π^+ π^-$ via the intermediate charmonia $ψ(4160)/ψ(4415)$ and direct $e^+e^-$ annihilation into $ψ(2S)π^+ π^-$. This fact shows that $Y(4360)$ is not a genuine resonance, which naturally explains why $Y(4360)$ was only reported in its hidden-charm decay channel $ψ(2S)π^+π^-$ and was not observed in the exclusive open-charm decay channel or $R$-value scan.

hep-ph↗

arXiv2011

Nonresonant explanation for the Y(4260) structure observed in the $e^+e^-\to J/ψπ^+π^-$ process

In this work, we proposed a nonresonant explanation for the Y(4260) structure observed in the $e^+e^-\to J/ψπ^+π^-$ process, i.e., Y(4260) is not a genuine resonance. Our result indicates that the Y(4260) structure can be reproduced by the interference of production amplitudes of the $e^+e^-\to J/ψπ^+π^-$ processes via direct $e^+e^-$ annihilation and through intermediate charmonia $ψ(4160)/ψ(4415)$. Besides describing Y(4260) line shape in $e^+e^-\to J/ψπ^+π^-$ well, such a nonresonant explanation for the Y(4260) structure naturally answers why there is no evidence of Y(4260) in the exclusive open-charm decay channel and $R$-value scan.

hep-ph↗

arXiv2010

The observed charmed hadron $Λ_c(2940)^+$ and the $D^*N$ interaction

In this work, we systematically study the interaction of $D^*$ and nucleon, which is stimulated by the observation of $Λ_c(2940)^+$ close to the threshold of $D^*p$. Our numerical result obtained by the dynamical investigation indicates the existence of the $D^*N$ systems with $J^P=1/2^\pm,\,3/2^\pm$, which not only provides valuable information to understand the underlying structure of $Λ_c(2940)^+$ but also improves our knowledge of the interaction of $D^*$ and nucleon. Additionally, the bottom partners of the $D^*N$ systems are predicted, which might be as one of the tasks in LHCb experiment.

hep-ph↗

arXiv2010

Recent progress towards acoustically mediated carrier injection into individual nanostructures for single photon generation

We report on recent progress towards single photon sources based on quantum dot and quantum post nanostructures which are manipulated using surface acoustic waves. For this concept acoustic charge conveyance in a quantum well is used to spatially separate electron and hole pairs and transport these in the plane of the quantum well. When conveyed to the location of a quantum dot or quantum post these carriers are sequentially captured into the confined levels. Their radiative decays gives rise to the emission of a train of single photons. Three different approaches using (i) strain- induced and (ii) self-assembled quantum dots, and (iii) self-assembled quantum posts are discussed and their application potential is discussed. First devices and initial experiments towards the realization of such an acoustically driven single photon source are presented and remote acoustically triggered injection into few individual emitters is demonstrated.

quant-ph↗

arXiv2010

$η$ production off the proton in a Regge-plus-chiral quark approach

A chiral constituent quark model approach, embodying s- and u-channel exchanges,complemented with a Reggeized treatment for t-channel is presented. A model is obtained allowing data for $π^- p \to ηn$ and $γp \to ηp$ to be describe satisfactorily. For the latter reaction, recently released data by CLAS and CBELSA/TAPS Collaborations in the system total energy range $1.6 \lesssim W \lesssim 2.8$ GeV are well reproduced due to the inclusion of Reggeized trajectories instead of simple $ρ$ and $ω$ poles. Contribution from "missing" resonances is found to be negligible in the considered processes.

nucl-th↗

arXiv2010

Control of the structural and magnetic properties of perovskite oxide ultrathin films through the substrate symmetry effect

Perovskite transition-metal oxides are networks of corner-sharing octahedra whose tilts and distortions are known to affect their electronic and magnetic properties. We report calculations on a model interfacial structure to avoid chemical influences and show that the symmetry mismatch imposes an interfacial layer with distortion modes that do not exist in either bulk material, creating new interface properties driven by symmetry alone. Depending on the resistance of the octahedra to deformation, the interface layer can be as small as one unit cell or extend deep into the thin film.

cond-mat.mtrl-sci↗

arXiv2010

Role of five-quark components in radiative and strong decays of the Lambda(1405) resonance

Within an extended chiral constituent quark model, three- and five-quark structure of the $S_{01}$ resonance $Λ(1405)$ is investigated. Helicity amplitudes for the electromagnetic decays ($Λ(1405) \to Λ(1116)γ$, $Σ(1194)γ$), and transition amplitudes for strong decays ($Λ(1405)\toΣ(1194)π$, $ K^{-}p$) are drived, as well as the relevant decay widths. The experimental value for the strong decay width, $Γ_{Λ(1405)\to (Σπ)^\circ}=50\pm 2$ MeV, is well reproduced with about 50% of five-quark admixture in the $Λ(1405)$. Important effects due to the configuration mixings among $Λ^{2}_{1}P_{A}$, $Λ^{2}_{8}P_{M}$ and $Λ^{4}_{8}P_{M}$ are found. In addition, transitions between the three- and five-quark components in the baryons turn out to be significant in both radiative and strong decays of the $Λ(1405)$ resonance.

nucl-th↗