arXiv subjects

Xu-Rong Chen

Publications and source records attributed to Xu-Rong Chen.

17 recordsLinked to original sources

arXiv2024

The plan for a super $\eta$ factory at Huizhou accelerator complex

As an approximate Goldstone boson with zero quantum number and zero standard model charge, the decay processes of long-lived $\eta$ meson offer a unique opportunity to explore new physics beyond the standard model and new sources of CP violation, as well as test the low-energy QCD theory and measure the fundamental parameters of light quarks. To pursue these goals in the physics frontiers, we propose a plan to construct a super $\eta$ factory at HIAF high-energy terminal or at CiADS after its energy upgrade. The high-intensity proton beam at HIAF enables the production of a vast number of $\eta$ samples, exceeding $10^{13}$ events per year in the first stage, utilizing multiple layers of thin targets made of light nucleus. This paper presents the physics goals, the first-version conceptual design of the spectrometer, and some preliminary simulation results.

hep-ph↗

arXiv2024

Revealing mysteries in gamma-ray bursts: the role of gluon condensation

We use a newly recognized gluon distribution in the nucleon, which was predicted by a QCD evolution equation to consistently explain several intriguing phenomena associated with gamma-ray bursts. They are the GeV-TeV spectra of GRB 221009A, the remarkably symmetrical explosion cloud in kilonova AT2017gfo, and the absence of a very high-energy gamma-ray signature in GRB 170817A. We find that these occurrences can be attributed to the gluon condensation within nucleons, i.e., a significant number of soft gluons within nucleons are condensed at a critical momentum, resulting in the emergence of a steep and high peak in the gluon distributions. Through this profound connection between microscopic and macroscopic phenomena, we have not only expanded the applications of the hadronic scenario in cosmic gamma-ray emissions but also presented new evidence for the existence of gluon condensation.

astro-ph.HE↗

arXiv2023

Exclusive production of $T^ {-} _{cc}$ in hadron-hadron ultraperipheral collisions

Understanding the production mechanisms and utilizing them as probes to investigate the structure of exotic states represent some of the most actively studied research areas in particle physics. In this study, we present a theoretical analysis of the charmed meson $T^{-}_{cc}$ in the $\gamma{}p\to{}D^{+}T^{-}_{cc}\Lambda^{+}_{c}$ and $\gamma\gamma\to{}D^{+}T^{-}_{cc}D^{*0}$ reactions, considering $T^{+}_{cc}$ as a $DD^{*}$ molecule. The differential cross-section and total cross-section for the photoproduction of $T^{-}_{cc}$ in the $\gamma{}p\to{}D^+T^{-}_{cc}\Lambda^{+}_{c}$ and $\gamma\gamma\to{}D^{+}T^{-}_{cc}D^{*0}$ reactions are presented for nucleus-nucleus (nucleon-nucleon) ultraperipheral collisions at HL-LHC and RHIC, respectively. Taking into account the integrated luminosity per typical run and the luminosity of photons from the nucleus (nucleon), we observe a significant event count for $T^ {-} _{cc}$ production in p-p ultraperipheral collisions at HL-LHC.

hep-ph↗

arXiv2019

Pion-induced production of hidden-charm pentaquarks $P_{c}(4312),P_{c}(4440)$, and $P_{c}(4457)$

The production of the hidden-charm pentaquarks $P_{c}$ via pion-induced reaction on a proton target is investigated within an effective Lagrangian approach. Three experimentally observed states, $P_c(4312)$, $P_c(4440)$, and $P_c(4457)$, are considered in the calculation, and the Reggeized $t$-channel meson exchange is considered as main background for the reaction $\pi ^{-}p\rightarrow J/\psi n$. The numerical results show that the experimental data of the total cross section of the reaction $\pi^{-}p\rightarrow J/\psi n$ at $W\simeq 5$ GeV can be well explained by contribution of the Reggeized $t$ channel with reasonable cutoff. If the branching ratios $Br[P_{c}\rightarrow J/\psi N]\simeq 3\%$ and $Br[P_{c}\rightarrow \pi N]\simeq 0.05\%$ are taken, the average value of the cross section from the $P_{c}(4312)$ contribution is about 1.2 nb/100 MeV, which is consistent with existing rude data at near-threshold energies. The results indicate that the branching ratios of the $P_{c}$ states to the $J/\psi N$ and $\pi N$ should be small. The shape of differential cross sections shows that the Reggeized $t$-channel provides a sharp increase at extreme forward angles, while the differential cross sections from the $P_{c}$ states contributions are relatively flat. High-precision experimental measurements on the reaction $\pi ^{-}p\rightarrow J/\psi n$ at near-threshold energies are suggested to confirm the LHCb hidden-charm pentaquarks as genuine states, and such experiments are also helpful to understand the origin of these resonance structures.

hep-ph↗

arXiv2019

Possibility to study pentaquark states $P_{c}(4312), P_{c}(4440)$, and $P_{c}(4457)$ in $\gamma p\rightarrow J/\psi p$ reaction

Inspired by the observation of the pentaquark states $P_{c}(4312),P_{c}(4440)$ and $P_{c}(4457)$ at LHCb, photoproduction of these three $P_{c}$ states via the interaction $\gamma p\rightarrow J/\psi p$ is investigated in an effective Lagrangian approach. The $t$-channel Pomeron exchange diffractive process is considered as the main background for the $J/\psi $ photoproduction. The numerical results show that the theoretical cross section, which is calculated by assuming a branching ratio $Br[P_{c}\rightarrow J/\psi p]\simeq 3\%$, is consistent with the existing experimental data of the $ \gamma p\rightarrow J/\psi p$ process. With such a branching ratio, if experimental precision reaches 0.1 nb within a bin of 100 MeV for photon energy, two peaks are expected to be obviously observed in the $J/\psi $ photoproduction. To observe the two-peak structure from $P_{c}(4440)$ and $ P_{c}(4457)$, higher precision, about 0.1nb/10 MeV, is required to distinguish two close pentaquarks. If the physical branching ratio is larger, the requirement of experimental precision will be reduced. The differential cross sections for reaction $\gamma p\rightarrow J/\psi p$ are also present. It is found that the $t$-channel Pomeron exchange provides a sharp increase at extreme forward angles and gives a sizable contribution at most energy points, while the contributions from the $s$-channel $P_{c}$ exchanges play important roles at threshold energies. The experimental measurement of the $\gamma p\rightarrow J/\psi p$ process in the near-threshold energy region around $E_{\gamma }\simeq 9.4-10.5$ GeV is suggested, and is accessible at CEBAF@JLab and COMPASS.

hep-ph↗

arXiv2015

Neutral hidden charm pentaquark states $P_c^0(4380)$ and $P_c^0(4450)$ in $\pi^-p \to J/\psi n$ reaction

We investigate the neutral hidden charm pentaquark states $P_c^0(4380)$ and $P_c^0(4450)$ in $\pi^-p \to J/\psi n$ reaction within an effective Lagrangian approach. The background contributions for the process mainly come from $t$-channel $\pi$ and $\rho$ meson exchanges. The contributions of $P_c^0(4380)$ and $P_c^0(4450)$ states give clear peak structures in the magnitude of 1 $\mu$b at center of mass energy 4.38 GeV and 4.45 GeV in the total cross sections. Hence, this reaction may provide a new good platform to search for neutral $P_c$ states. It is expected that our estimated total cross sections together with the angular distributions can be tested by future experiments at J-PARC.

hep-ph↗

arXiv2015

Discovery potential for the neutral charmoniumlike $Z^{0}(4200)$ by $\bar{p}p$ annihilation

Inspired by the observation of charmoniumlike $Z(4200)$, we explore the discovery potential of the neutral $Z^{0}(4200)$ production by antiproton-proton annihilation with an effective Lagrangian approach. By investigating the $\bar{p}p\rightarrow J/\psi \pi ^{0}$ process including the $Z^{0}(4200)$ signal and background contributions, it is found that the center of mass energy $E_{c.m.}\simeq 4.0-4.5$ GeV is the best energy window for searching the neutral $Z^{0}(4200)$, where the signal can be clearly distinguished from background. The relevant calculations is not only helpful to search for the neutral $Z^{0}(4200)$ in the future experiment, but also will promote the understanding the nature and production mechanism of neutral $Z^{0}(4200)$ better.

hep-ph↗

arXiv2015

$\Lambda _{c}^{+}(2940)$ photoproduction off the neutron

By assuming that the $\Lambda _{c}^{\ast }(2940)$ is a $pD^{\ast 0}$ molecular state with spin-parity $J^{P}=\frac{1}{2}^{+}$ and $J^{P}=\frac{1}{2}^{-}$, the photoproduction of charmed $\Lambda _{c}^{\ast }(2940)$ baryon in the $\gamma n\rightarrow D^{-}\Lambda _{c}^{\ast }(2940)^{+}$ process is investigated with an effective Lagrangian approach. It is found that the contributions from $t$-channel with $D^{\ast }$ exchange are dominant, while the $s$-channel with nucleon pole exchange give a sizeable contribution around the threshold. The contributions from the $u$-channel and contact term are very small. The total cross section of the $\gamma n\rightarrow D^{-}\Lambda _{c}^{\ast }(2940)^{+}$ reaction is estimated, which indicate it is feasible to searching for the charmed $\Lambda _{c}^{\ast }(2940)$ baryon at the COMPASS experiment.

hep-ph↗

arXiv2015

Production of the superheavy baryon $\Lambda _{c\bar{c}}^{\ast}(4209) $ in kaon-induced reaction

The production of superheavy $\Lambda _{c\bar{c}}^{\ast }(4209)$ baryon in the $K^{-}p\rightarrow \eta _{c}\Lambda $ process via $s$-channel is investigated with an effective Lagrangian approach and the isobar model. Moreover, the $t$-channel with $K^{\ast }$ and $u$-channel with nucleon exchange are also considered, which are regarded as the background for the $\Lambda _{c\bar{c}}^{\ast }(4209)$ production in the $K^{-}p\rightarrow \eta_{c}\Lambda $ reaction. The numerical results indicate it is feasible to searching for the superheavy $\Lambda _{c\bar{c}}^{\ast }(4209)$ via $K^{-}p$ scattering. These theoretical results not only provide valuable informations to future experimental exploration of $\Lambda _{c\bar{c}}^{\ast }(4209)$ resonance but enable us to have a better understanding of the exotic baryons.

hep-ph↗

arXiv2014

Theoretical investigation of the decay of the $N(2120)$ resonance to nucleon resonances near 1.7 GeV

Background: Until now the knowledge about nucleon resonances with a mass higher than 2 GeV has been scarce. Huge amounts of experimental data of the multipion photoproduction have been accumulated, and more can be expected in the future in facilities such as JLab 12 GeV. It makes it possible to investigate the decay of a nucleon resonance into another nucleon resonance. Purpose: The possibility to research the decay of the $N(2120)$ to nucleon resonances near 1.7 GeV in the three-pion photoproduction will be explored to provide useful information for future experimental study. Method: The pion and radiative decay amplitudes of nucleon resonances are studied within the constituent quark model, which is used to calculate the couplings constants, especially for the decay of a nucleon resonance near 2.1 GeV to another nucleon resonance near 1.7 GeV. The three-pion photoproduction off the neutron target, i.e.,$\gamma n \to\pi^{-}\pi^{-}\Delta^{++}\to \pi^{-}\pi^{-}\pi^+ p$, is investigated based on the effective Lagrangian method with the coupling constant obtained form the decay amplitudes. Results: The resonance contribution with a state $N(^2P_M)\frac{3}{2}^{-}$ near 2.1 GeV decaying to a state $N(^4P_M)\frac{5}{2}^{-}$ near 1.7 GeV, i.\ e., $N(2120)\to N(1675)\pi$ is dominant in the process considered. The total cross section from the resonance contribution is at the order of 1 $\mu$b and can be easily distinguished from the background. Conclusions: Our results suggest it is practicable to research the decay of the $N(2120)$ to the $N(1675)$ in experiment.

nucl-th↗

arXiv2014

Nucleon resonances in the $\gamma p \to \phi K^+ \Lambda$ reaction near threshold

We investigate the $\gamma p \to \phi K^+ \Lambda$ reaction near threshold within an effective Lagrangian approach and the isobar model. Various nucleon resonances caused by the $\pi$ and $\eta$ meson exchanges and background contributions are considered. It is shown that the contribution from the $N^*(1535)$ resonance caused by the $\eta$ meson exchange plays the predominant role. Hence, this reaction provides a good new platform to study the $N^*(1535)$ resonance. The predicted total cross section and specific features of angular distributions can be tested by future experiments.

nucl-th↗

arXiv2014

Reexamination of the role of the $\Delta ^{\ast}$ resonances in the $pp\rightarrow nK^{+}\Sigma ^{+}$ reaction

In this work, the role of the $\Delta ^{\ast }$ resonances in the process of $pp\rightarrow nK^{+}\Sigma ^{+}$ are systematically investigated with the effective Lagrangian approach and the isobar model. We find that a $P_{31}$ state, either $\Delta ^{\ast }(1750)$ or $\Delta ^{\ast }(1910)$, is favored by the data while the $P_{33}$ state, namely $\Delta ^{\ast }(1920)$, has small contribution. Besides, either sub-threshold $S_{31}$ $\Delta ^{\ast }(1620)$ resonance or strong $n\Sigma $ final state interaction or both have possible contribution at near threshold region, depending on the measured cross sections. We demonstrate the invariant mass distributions and the Dalitz Plots in order to investigate whether it is possible to distinguish the controversial $K\Sigma $ production mechanism in these observables.

nucl-th↗

arXiv2014

Nucleon resonances in the $\pi^- p \to K^0 \Lambda$ reaction near threshold

We investigate the two-body reaction $\pi^- p \to K^{0} \Lambda$ within the effective Lagrangian approach and the isobar model. In addition to the "background" contributions from $t$-channel $K^*$ exchange, $u$-channel $\Sigma(1192)$ and $\Sigma^*(1385)$ exchanges, and $s$-channel nucleon pole terms, the contributions from the nucleon resonances $N^*(1535)$, $N^*(1650)$, and $N^*(1720)$ are investigated. It is shown that the inclusion of these nucleon resonances contributions leads to a good description of the experimental total and differential cross sections data at low energy region. The $s$-channel $N^*(1535)$, $N^*(1650)$, and $N^*(1720)$ resonances and the $t$-channel $K^*$ exchange give the dominant contributions below $W = 1.76$ GeV, while the $u$-channel $\Sigma(1192)$ and $\Sigma^*(1385)$ exchanges give the minor contributions.

nucl-th↗

arXiv2014

The $\bar{p} p \to \phi \phi $ reaction in an effective Lagrangian approach

We investigate the $\bar{p} p \to \phi \phi$ reaction within an effective Lagrangian approach.We show that the inclusion of either a scalar meson $f_0$ or a tensor meson $f_2$ in the $s$-channel can lead to a fairly good description of the bump structure of the total cross section around the invariant $\bar{p} p$ mass $W \simeq 2.2$ GeV, which cannot be reproduced with only the "background" contributions from $t$- and $u$-channel $N^*(1535)$ resonance as studied in a previous work. From the fits, we infer the properties of the involved scalar or tensor resonances.

nucl-th↗

arXiv2013

The $\gamma p \to n a^+_2(1320) \to n \rho^0 \pi^+$ reactions within an effective Lagrangian approach

We investigate the $a_2(1320)$ meson photon production in the $\gamma p \to n a^+_2(1320)$ and $\gamma p \to n \rho^0 \pi^+$ reactions within the effective Lagrangian method. For $\gamma p \to n a^+_2(1320)$ reaction, by considering the contributions only from the $t-$channel $\pi^+$ exchange, we get a fairly good description of the current experimental total cross section data. We also studied the $\gamma p \to n \rho^0 \pi^+$ reaction, which mainly contribute to the $\gamma p \to n \pi^+ \pi^+ \pi^-$ reaction. The latter reaction has measured by the CLAS Collaboration. The total cross sections, invariant mass distribution, and the Dalitz Plot of $\gamma p \to n \rho^0 \pi^+$ reaction are shown, which can be tested by future experiments.

hep-ph↗

arXiv2013

Discovery potential of hidden charm baryon resonances via photoproduction

In this work, we study the possibility to find $N^*_{c\bar{c}}$ and $\Lambda^*_{c\bar{c}}$ resonances with hidden charm with mass above 4 GeV in the photon-induced production. The cross sections for the photoproductions of hidden charmed baryons are predicted in the effective Lagrangian approach with the vector meson dominance mechanism. The $N^*(4412)$ can be produced directly by photon excitation with total cross section about 1 nb. The $N^*(4412)$ provides a obvious peak near threshold for $J/\psi$ photoproduction, which is promising to be checked by the future high precision experiment at JLab 12 GeV. The results will be helpful to the experimental search for the hidden-charmed baryon resonances in the coming experiment at JLab 12 GeV, such as SoLID, and the proposed electron-ion colliders at FAIR and HIAF.

nucl-th↗

arXiv2012

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

In this work the roles of the nucleon resonances in the $\Lambda$(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↗