arXiv subjects

Jian-Xiong Wang

Publications and source records attributed to Jian-Xiong Wang.

65 records · Page 4Linked to original sources

arXiv2005

The Color-Octet Contributions to $P$-wave $B_c$ Meson Hadroproduction

The contributions from the color-octet components $|(c\bar b)_{\bf 8}(^{1}S_{0}) g>$ and $|(c\bar b)_{\bf 8}(^{3}S_{1}) g>$ to the $h_{B_c}$ or $χ_{B_c}^J$ (the $P$-wave $B_c$ meson) hadroproduction are estimated in terms of the complete ${\cal O}(α_s^4)$ calculation. As necessary inputs in the estimate, we take the values of the octet matrix elements according to the NRQCD scaling rules, and as a result, we have found that the contributions to the $P$-wave production may be the same in order of magnitude as those from the color-singlet ones, $|(c\bar b)_{\bf 1}(^{1}P_{1})>$ and $|(c\bar b)_{\bf 1}(^{3}P_{J})>$ ($J=1,2,3$). Especially, our result indicates that the observation of the color-octet contributions to the $P$-wave production in the low transverse momentum region is not very far from the present experimental capability at Tevatron and LHC.

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arXiv2004

Hadronic production of the $P$-wave excited $B_c$-states ($B_{cJ,L=1}^*$)

Adopting the complete $α_s^4$ approach of the perturbative QCD (pQCD) and updated parton distribution functions, we have estimated the hadronic production of $P$-wave excited $B_c$-states ($B_{cJ,L=1}^*$). In the estimate, special care on the relation of the production amplitude to the derivative of wave function at origin of the potential model is payed. For experimental references, main uncertainties are discussed, and the total cross sections and the distributions of the production with reasonable cuts at the energies of Tevatron and LHC are computed and presented. The results show that $P$-wave production may contribute to the $B_c$-meson production indirectly by a factor about 0.5 of the direct production, and with such a big cross section, it is worth further to study the possibility to observe the $P$-wave production itself experimentally.

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arXiv2004

Phenomenology of quintessino dark matter -- Production of NLSP particles

In the model of quintessino as dark matter particle, the dark matter and dark energy are unified in one superfield, where the dynamics of the Quintessence drives the Universe acceleration and its superpartner, quintessino, makes up the dark matter of the Universe. This scenario predicts the existence of long lived $\tildeτ$ as the next lightest supersymmetric particle. In this paper we study the possibility of detecting $\tildeτ$ produced by the high energy cosmic neutrinos interacting with the earth matter. By a detailed calculation we find that the event rate is one to several hundred per year at a detector with effective area of $1 km^2$. The study in this paper can be also applied for models of gravitino or axino dark matter particles.

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arXiv2004

Progress in FDC Project

The FDC is a general-purpose program package for Feynman Diagram Calculation. We outline previous successes in calculations and focus on its recent progress about automatic deduction the Feynman rules for first principle model, especially for the supersymmetric model, proper evaluation of the rates of multi-final-particle processes and the event generators in the SM and MSSM. A few special applications are presented. The FDC-homepage shows an automatic translation of the FDC results into the HTTP version.

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arXiv2003

The Color Octet Effect from $e^+ e^-\to{J/ψ}+X+γ$ at B Factory

We study the initial state radiation process $e^+ e^-\to{J/ψ}+X+γ$ for $J/ψ$ production at B factory, and find the cross section is 61% larger than it's Born one for color octet part and is about half as it's Born one for color singlet part. Furthermore, the color singlet and color octet signal are very clearly separated in it's $E_γ$ spectra due to kinematics difference. We suggest to measure this $E_γ$ spectra at B factory to determine the color octet effect.

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arXiv2003

$J/ψ+ c + \bar{c}$ Photoproduction in $e^+ e^-$ Scattering

We investigate the $J/ψ$ + c + $\bar{c}$ photoproduction in $e^+ e^-$ collision at the LEP II energy. The physical motivations for this study are: 1) such next-to-leading order(NLO) process was not considered in previous investigations of $J/ψ$ photoproduction in $e^+ e^-$ interaction, and it is worthwhile to do so in order to make sound predictions for experimental comparison; 2) from recent Belle experiment results, the process with same final states at the $B$ factory has a theoretically yet unexplainable large fraction; hence it is interesting to see what may happen at other colliders; 3) the existing LEP data are marginal in observing such process, and at the planed Linear Colliders(LCs) this process can be measured with high accuracy; 4) it is necessary to take this process into consideration in the aim of elucidating the quarkonium production mechanism, especially in testing the universality of NRQCD nonperturbative matrix elements via $J/ψ$ photoproduction in electron-position collisions.

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arXiv1999

Further Study On U(1) Gauge Invariance Restoration

To further investigate the applicability of the projection scheme for eliminating the unphysical divergence $s/m_e^2$ due to U(1) gauge invariance violation, we study the process $e^-+W^+\to e^-+\bar t+b$ which possesses advantages of simplicity and clearness. Our study indicates that the projection scheme can indeed eliminate the unphysical divergence $s/m_e^2$ caused by the U(1) gauge invariance violation and the scheme can apply to very high energy region.

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arXiv1998

Probing anomalous top quark couplings at eγcolliders

We study in the effective Lagrangian approach the possibility of probing anomalous top quark charged current couplings in the single top production at a high energy eγcollider. We analyzed all possible dimension-six CP-conserving operators which can give rise to an anomalous Wtb coupling which represent new physics effect generated at a higher energy scale. For those operators which also give rise to anomalous Zbb_bar or right-handed Wtb couplings, we find that they are strongly constrained by the existing R_b and b->sγdata. As a result, a collider with a luminosity of the order of 100 fb^{-1} is required to observe the anomalous effects. For other operators which currently subject to no strong constraints, the high energy eγcollider can probe their couplings effectively because of the clean environment of such a collider.

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arXiv1997

J/ψElectromagnetic Production at e^+e^- colliders

Within the framework of QED we investigate the inclusive J/ψproduction at $e^+e^-$ colliders. It is expected to be as a further test to the charmonium production mechanisms and QED. We find that at the energies of CESR, BEPC, and TRISTAN (e.g. 4.0 GeV \leq \sqrt s \leq 60 GeV), the contributions of the concerned electromagnetic processes to the $J/ψ$ inclusive production are great, even dominant, thus they greatly affect the observation of the color-octet $J/ψ$ production signature at $e^+e^-$ colliders. The production of ψ', being similar to that of J/ψ's, is roughly estimated, and its influence on the observation of the color-octet J/ψproduction signature in e^+e^- collision is also discussed.

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arXiv1997

The J/ψProduction Associated with a Hard Photon and the Color-Octet Singnature in e^+e^- Annihilation

J/ψproduction associated with a hard photon in e^+e^- annihilation, being of QED nature, is invastigated thoroughly in the paper. To show its influence on the observation of the color-octet singnature in the e^+e^- annihilation via J/ψinclusive production, the cross sections of the J/ψproductions through different mechanisms at various energies are compared quantatively by presenting them in figures together. The contribution from the production associated with a hard photon to the inclusive production of J/ψis pointed out to be significant at the concerned energies, thus the influence from it on the observation of the color-octet signature should be dealt with carefully.

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arXiv1995

On the observation of $e^+e^-\to b \bar{b}Z^0$ at LEP II with two Higgs doublets

We study possible observational effects of the two Higgs doublets in the $e^+e^- \to b \bar{b} Z^0$ at the LEP II energy. We have found that the observational values can be obviously different from that predicted by the minimal Standard Model (MSM), but the results depend on the parameters of the extended model. The possibilities of the observation are discussed in some details.

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