arXiv subjects

Hong-Fei Zhang

Publications and source records attributed to Hong-Fei Zhang.

At least 37 records · Page 2Linked to original sources

arXiv2019

Phenomenological NLO analysis of eta(c) production at the LHC in the collider and fixed-target modes

In view of the good agreement between the LHCb prompt-eta(c) data at sqrt(s)=7 and 8 TeV and the NLO colour-singlet model predictions --i.e. the leading v^2 NRQCD contribution--, we provide predictions in the LHCb acceptance for the forthcoming 13 TeV analysis bearing on data taken during the LHC Run2. We also provide predictions for sqrt(s)=115 GeV for proton-hydrogen collisions in the fixed-target mode which could be studied during the LHC Run3. Our predictions are complemented by a full theoretical uncertainty analysis. In addition to cross section predictions, we elaborate on the uncertainties on the p bar-p branching ratio --necessary for data-theory comparison-- and discuss other usable branching fractions for future studies.

hep-ph↗

arXiv2018

Double longitudinal-spin asymmetries in $J/ψ$ production at RHIC

The double longitudinal-spin asymmetry, $A_{LL}$, of the $J/ψ$ production in polarized proton-proton collisions is presented in this paper at QCD next-to-leading order. It is found that the obtained values of $A_{LL}$ are in general consistent with the PHENIX measurements. Various sets of the long-distance matrix elements (LDMEs) are employed in our calculation to study the possible theoretical uncertainties. It is found that, for $p_t<5\gev$, all these LDMEs lead to almost the same results, which are within the tolerance of the experimental data uncertainties.

hep-ph↗

arXiv2018

$ψ(2S)$ versus $J/ψ$ suppression in proton-nucleus collisions from factorization violating soft color exchanges

We argue that the large suppression of the $ψ(2S)$ inclusive cross-section relative to the $J/ψ$ inclusive cross-section in proton-nucleus (p+A) collisions can be attributed to factorization breaking effects in the formation of quarkonium. These factorization breaking effects arise from soft color exchanges between charm-anticharm pairs undergoing hadronization and comoving partons that are long-lived on time scales of quarkonium formation. We compute the short distance pair production of heavy quarks in the Color Glass Condensate (CGC) effective field theory and employ an improved Color Evaporation model (ICEM) to describe their hadronization into quarkonium at large distances. The combined CGC+ICEM model provides a quantitative description of $J/ψ$ and $ψ(2S)$ data in proton-proton (p+p) collisions from both RHIC and the LHC. Factorization breaking effects in hadronization, due to additional parton comovers in the nucleus, are introduced heuristically by imposing a cutoff $Λ$, representing the momentum kick from soft color exchanges, in the ICEM model. Such soft exchanges have no perceptible effect on $J/ψ$ suppression in p+A collisions. In contrast, the interplay of the physics of these soft exchanges at large distances, with the physics of semi-hard rescattering at short distances, causes a significant additional suppression of $ψ(2S)$ yields relative to that of the $J/ψ$. A good fit of all RHIC and LHC $J/ψ$ and $ψ(2S)$ data, for transverse momenta $P_\perp\leq 5$ GeV in p+p and p+A collisions, is obtained for $Λ\sim 10$ MeV.

hep-ph↗

arXiv2017

QCD leading order study of the $J/ψ$ leptoproduction at HERA within the nonrelativistic QCD framework

As indicated in our previous paper (Phys.Rev.D96.034002), the existing literatures studying the $J/ψ$ production in deeply inelastic scattering (DIS) in collinear factorization are on the basis of a formalism that will lead to wrong results when the ranges of the transverse momentum or the rapidity of the $J/ψ$ in the laboratory frame do not cover all values possible for them. In this paper, we present the renewed results for the $J/ψ$ production in DIS at HERA within the nonrelativistic QCD framework at QCD leading order (LO). Three different sets of the long-distance matrix elements are employed for comparison. The predictions via the colour-singlet (CS) model at QCD LO are generally below the experimental data especially in the regions where perturbation theory are expected to work well, while the colour-octet contributions are of the same order of magnitude as the CS ones, however, in general make the agreement between theory and experiment better.

hep-ph↗

arXiv2017

QCD Corrections to the Color-singlet $J/ψ$ Production in Deeply Inelastic Scattering at HERA

We present the first study of the QCD corrections to the color-singlet (CS) $J/ψ$ production in deeply inelastic $ep$ scattering at HERA. The $K$-factor ranges from $0.85$ to $2.38$ in the kinematic regions we study. In low transverse momentum regions, the $K$-factors is even smaller, and close to 1, which indicates good convergence of the perturbative expansion. With the QCD corrections, the CS cross section is still below the data. At least at QCD next-to-leading order, the color-octet mechanism is necessary to describe the data.

hep-ph↗

arXiv2017

$η_c'$ Hadroproduction at Next-to-Leading Order and its Relevance to $ψ'$ Production

We proceed to the first study of $η_c'$ prompt hadroproduction at next-to-leading order in $α_s$. Based on heavy-quark-spin symmetry, which is systematically used in quarkonium-production phenomenology, we demonstrate that prompt $η_c'$ can be studied at the LHC with the existing data. We emphasize its relevance to constrain $ψ'$ production, in the same way as the first prompt $η_c'$ data at the LHC lately strongly impacted the phenomenology of $J/ψ$ studies.

hep-ph↗

arXiv2017

The leptonic current structure and azimuthal asymmetry in deeply inelastic scattering

We present a compact form of the leptonic currents for the computation of the processes involving an initial virtual boson (photon, $W^{\pm}$ or $Z_0$). For deeply inelastic scattering, once the azimuthal angle of the plane expanded by the initial- and final-state leptons are integrated over in the boson-proton rest frame, the azimuthal-asymmetric terms vanish, which, however, is NOT true when some physical quantities (such as the transverse momentum of the observed particle) are specified in laboratory frame. The abuse of the symmetry may lead to wrong results.

hep-ph↗

arXiv2017

Is the colour-octet mechanism consistent with the double $J/ψ$ production measurement at B-factories?

Double $J/ψ$ production in $e^+e^-$ collisions involving colour-octet channels are evaluated up to order $α^2α_s^3$. Having implemented the variation of the parameters ($m_c$, $μ_r$ and long-distance matrix elements), we found that the cross sections for producing double $J/ψ$ at B-factories range from $-0.016$fb to $0.245$fb, which are even much smaller than that via the colour-siglet mechanism. Accordingly, this result is consistent with the measurement by the Belle and BABAR Collaborations.

hep-ph↗

arXiv2016

Production of proton-rich nuclei around Z=84-90 in fusion-evaporation reactions

Within the framework of the dinuclear system model, production cross sections of proton-rich nuclei with charged numbers of Z=84-90 are investigated systematically. Possible combinations with the $^{28}$Si, $^{32}$S, $^{40}$Ar bombarding the target nuclides $^{165}$Ho, $^{169}$Tm, $^{170-174}$Yb, $^{175,176}$Lu, $^{174,176-180}$Hf and $^{181}$Ta are analyzed thoroughly. The optimal excitation energies and evaporation channels are proposed to produce the proton-rich nuclei. The systems are feasible to be constructed in experiments. It is found that the neutron shell closure of N=126 is of importance during the evaporation of neutrons. The experimental excitation functions in the $^{40}$Ar induced reactions can be nicely reproduced. The charged particle evaporation is comparable with neutrons in cooling the excited proton-rich nuclei, in particular for the channels with $α$ and proton evaporation. The production cross section increases with the mass asymmetry of colliding systems because of the decrease of the inner fusion barrier. The channels with pure neutron evaporation depend on the isotopic targets. But it is different for the channels with charged particles and more sensitive to the odd-even effect.

nucl-th↗

arXiv2016

Isospin splitting of nucleon effective mass and symmetry energy in isotopic nuclear reactions

Within an isospin and momentum dependent transport model, the dynamics of isospin particles (nucleons and light clusters) in Fermi-energy heavy-ion collisions are investigated for constraining the isospin splitting of nucleon effective mass and the symmetry energy at subsaturation densities. The mass splitting of $m^{*}_{n}>m^{*}_{p}$ and $m^{*}_{n}<m^{*}_{p}$ in nuclear matter and the different stiffness of symmetry energy are used in the model. The single and double neutron to proton ratios of free nucleons and light particles are thoroughly investigated in the isotopic nuclear reactions of $^{112}$Sn+$^{112}$Sn and $^{124}$Sn+$^{124}$Sn at the incident energies of 50 and 120 MeV/nucleon, respectively. It is found that the both effective mass splitting and symmetry energy impact the kinetic energy spectra of the single ratios, in particular at the high energy tail (larger than 20 MeV). Specific constraints are obtained from the double ratio spectra, which are evaluated from the ratios of isospin observables produced in $^{124}$Sn+$^{124}$Sn over $^{112}$Sn+$^{112}$Sn collisions. A mass splitting of $m^{*}_{n}<m^{*}_{p}$ is constrained from the available data at the energy of 120 MeV/nucleon. A soft symmetry energy with the stiffness of $γ_{s}=$0.5 is close to the experimental double ratio spectra at both energies.

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arXiv2016

Production of charmed baryon $Λ_c(2940)$ by kaon-induced reaction on a proton target

We investigate the possibility to study the charmed baryon $Λ_c(2940)$ by kaon-induced reaction on a proton target. By assuming the $Λ_c(2940)$ as a $pD^{*0}$ molecular state with spin-parity $J^{p}=1/2^{\pm}$, an effective Lagrangian approach was adopted to calculate the cross section, the $D^0p$ invariant mass spectrum and Dalitz plot of the $Λ(2940)$ production. The total cross section of the $K^{-}p\toΛ_c(2940)D_s^{-}$ reaction is found at an order of magnitude about 10 $μ$b. By considering the sub sequential decay $Λ_c(2940)\to{}D^0p$ with contributions from the $Λ_c(2286)$ and the $Σ_c(2455)$ as background, the $K^{-}p\to{}D_{s}^{-}D^{0}p$ reaction are studied. It is found that the $Λ_c(2940)$ is produced mainly at forward angles. The $Λ_c(2940)$ signal is predicted to be significant in the $D^0p$ invariant mass spectrum and the Dalitz plot of the $K^{-}p\to{}D_{s}^{-}D^{0}p$ reaction. The results suggest that it is promising to study the $Λ_c(2940)$ with high-energy kaon beam on a proton target in experiment.

hep-ph↗

arXiv2016

Photoproduction of hidden-charm states in the $γp \to \bar{D}^{*0} Λ^+_c$ reaction near threshold

We report on a theoretical study of the hidden charm $N^*_{c \bar{c}}$ states in the $γp \to \bar{D}^{*0} Λ^+_c$ reaction near threshold within an effective Lagrangian approach. In addition to the contributions from the $s$-channel nucleon pole, the $t$-channel $D^0$ exchange, the $u$-channel $Λ^+_c$ exchange and the contact term, we study the contributions from the $N^*_{c \bar{c}}$ states with spin-parity $J^P = 1/2^-$ and $3/2^-$. The total and differential cross sections of the $γp \to \bar{D}^{*0} Lambda^+_c$ reaction are predicted. It is found that the contributions of these $N^*_{c \bar{c}}$ states give clear peak structures in the total cross sections. Thus, this reaction is another new platform to study the hidden-charm states. It is expected that our model calculation may be tested by the future experiments.

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arXiv2016

$η_c$ production associated with light hadrons at the B-factories and the future super B-factories

We present a complete study of the associated production of the $η_c$ meson with light hadrons in $e^+e^-$ collisions at the B-factory energy, which is demonstrated to be one of the best laboratories for testing the colour-octet (CO) mechanism. The colour-siglet contributions are evaluated up to $O(α^2α_s^3)$ while the CO ones are evaluated up to $O(α^2α_s^2)$. For the first time, the angular distribution of the $^1S_0^{[8]}$ production is studied at QCD next-to-leading order. We find that the $^1S_0^{[8]}$ channel dominate the total cross section, while the $^1P_1^{[8]}$ one exhibit its importance in the angular distribution, which turns out to be downward going with respect to $\mathrm{cos}θ$. This can be considered as the most distinct signal for the CO mechanism.

hep-ph↗

arXiv2016

A Statistical Approach to Describe Highly Excited Heavy and Superheavy Nuclei

A statistical approach based on the Weisskopf evaporation theory has been developed to describe the de-excitation process of highly excited heavy and superheavy nuclei, in particular for the proton-rich nuclei. The excited nucleus is cooled by evaporating $γ$-ray, light particles (neutrons, protons, $α$ etc) in competition with the binary fission, in which the structure effects (shell correction, fission barrier, particle separation energy) contribute to the processes. The formation of residual nuclei is evaluated via sequential emission of possible particles above the separation energies. The available data of fusion-evaporation excitation functions in the $^{28}$Si+$^{198}$Pt reaction can be reproduced nicely well within the approach.

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arXiv2016

Global analysis of the experimental data on $χ_c$ meson hadroproduction

We carry out a global analysis of the experimental data on the $χ_c$ production cross section and the ratio $σ(χ_{c2})/σ(χ_{c1})$ at the LHC and the Tevatron. The related long-distance matrix elements (LDMEs) at both leading order (LO) and next-to-leading order (NLO) in the QCD coupling constant are renewed. We also present the transverse momentum distribution of the $χ_c$ production cross section and the ratio $σ(χ_{c2})/σ(χ_{c1})$ for several experimental conditions and find that NLO predictions agree with all sets of experimental data. By contrast, at LO, one cannot explain all the data with a unique value of the color-octet LDME. A brief analysis of the nonrelativistic QCD scale dependence of the cross sections shows that, for the conditions we are concerned with in this paper, the dependence can be almost totally absorbed into the LDME.

hep-ph↗

arXiv2015

An Autonomous Observation and Control System Based on EPICS and RTS2 for Antarctic Telescopes

For an unattended telescopes in Antarctic, the remote operation, autonomous observation and control are essential. An EPICS (Experimental Physics and Industrial Control System) and RTS2(Remote Telescope System, 2nd Version) based autonomous observation and control system with remoted operation is introduced in this paper. EPICS is a set of Open Source software tools, libraries and applications developed collaboratively and used worldwide to create distributed soft real-time control systems for scientific instruments while RTS2 is an open source environment for control of a fully autonomous observatory. Using the advantage of EPICS and RTS2 respectively, a combined integrated software framework for autonomous observation and control is established that use RTS2 to fulfill the function of astronomical observation and use EPICS to fulfill the device control of telescope. A command and status interface for EPICS and RTS2 is designed to make the EPICS IOC (Input/Output Controller) components integrate to RTS2 directly. For the specification and requirement of control system of telescope in Antarctic, core components named Executor and Auto-focus for autonomous observation is designed and implemented with remote operation user interface based on Browser-Server mode. The whole system including the telescope is tested in Lijiang Observatory in Yunnan Province for practical observation to complete the autonomous observation and control, including telescope control, camera control, dome control, weather information acquisition with the local and remote operation.

astro-ph.IM↗

arXiv2015

The prompt $J/ψ$ production in Association with a $c\bar{c}$ Pair within the Framework of Non-relativistic QCD via photon-photon collision at the International Linear Collider

We present a systematical study on the prompt $J/ψ$ production in association with a $c\bar{c}$ pair via the process, $γγ\to H(c\bar{c}) +c+\bar{c}$, within the framework of non-relativistic QCD at the future high-energy $e^{+}e^{-}$ collider - International Linear Collider (ILC), including both direct and feed-down contributions. For direct $J/ψ$ production, the states with color-octet channels, especially the $^3P_J^{[8]}$ and $^1S_0^{[8]}$ ones, provide dominant contribution to the production cross-section, which are about fifty-two times over that of the color-singlet one. This is clearly shown by the transverse momentum ($p_t$) and rapidity distributions. The feed-down contribution from $ψ'$ and $χ_{cJ}$ ($J=0,1,2$) is sizable, which is about $20\%$ to the total prompt cross-section. Besides the yields, we also calculate the $J/ψ$ polarization parameter $λ$. In small $p_t$ region, the polarization of the prompt $J/ψ$ is longitudinal due to large contributions through the $^3P_J^{[8]}$ channel, and becomes transverse in high $p_t$ region due to $^3S_1^{[8]}$ channel. Thus the $J/ψ$ production via photon-photon collisions at the ILC shall provide a useful platform for testing the color-octet mechanism.

hep-ph↗

arXiv2015

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.,$γn \toπ^{-}π^{-}Δ^{++}\to π^{-}π^{-}π^+ p$, 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., $N(2120)\to N(1675)π$ is dominant in the process considered. The total cross section from the resonance contribution is at the order of 1 $μ$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.

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