arXiv subjects

Cong-Feng Qiao

Publications and source records attributed to Cong-Feng Qiao.

At least 181 records · Page 10Linked to original sources

arXiv2009

Bell Inequalities in High Energy Physics

We review in this paper the research status on testing the completeness of Quantum mechanics in High Energy Physics, especially on the Bell Inequalities. We briefly introduce the basic idea of Einstein, Podolsky, and Rosen paradox and the results obtained in photon experiments. In the tests of Bell inequalities in high energy physics, the early attempts of using spin correlations in particle decays and later on the mixing of neutral mesons used to form the quasi-spin entangled states are covered. The related experimental results in K^0 and B^0 systems are presented and discussed. We introduce the new scheme, which is based on the non-maximally entangled state and proposed to implement in ϕfactory, in testing the Local Hidden Variable Theory. And, we also discuss the possibility in generalizing it to the tau charm factory.

hep-ph↗

arXiv2009

Phase Diagram for Nflation

Recently, it was showed that there is a large N phase transition in Nflation, in which when the number of fields is large enough, the slow roll inflation phase will disappear. In this brief report, we illustrate the phase diagram for Nflation, and discuss the entropy bound and some relevant results. It is found that near the critical point the number of fields saturates dS entropy.

hep-th↗

arXiv2009

Cosmological Evolution of a Tachyon-Quintom Model of Dark Energy

In this work we study the cosmological evolution of a dark energy model with two scalar fields, i.e. the tachyon and the phantom tachyon. This model enables the equation of state $w$ to change from $w>-1$ to $w<-1$ in the evolution of the universe. The phase-space analysis for such a system with inverse square potentials shows that there exists a unique stable critical point, which has power-law solutions. In this paper, we also study another form of tachyon-quintom model with two fields, which voluntarily involves the interactions between both fields.

astro-ph↗

arXiv2008

Possible contributions to $e^+e^- \to J/ψ+ η_c$ due to intermediate meson rescatterings

Inspired by the obvious discrepancies between experiment and non-relativistic QCD (NRQCD) studies of $e^+ e^-\to J/ψ+η_c$ at $\sqrt{s}\simeq 10.6$ GeV, we investigate contributions from intermediate meson loops as long-range interaction transitions to this process. The intermediate meson loops include $D\bar D(\bar D^\ast)$, $D\bar D^\ast(D {or} D^\ast)$, $D^\ast \bar D^\ast(D)$ and corresponding $D_s$ intermediate mesons. With the constraints from experimental data on the vertex couplings, we find that the intermediate meson loops account for $2.7\sim 6.7 fb$ of the cross sections within a reasonable range of cut-off energies of the factor parameter. We also investigate contributions from the absorptive part and find that it accounts for approximately $0.58\sim 1.38 fb$. These results imply that contributions from long-range interaction transitions may still play a role in such an energy region.

hep-ph↗

arXiv2008

EtabFDC: an $η_b$ event generator in hadroproduction at LHC

The EtabFDC is a matrix-element event generator package for $η_b$ hadroproduction at LHC. It generates $pp\toη_b X$ events for all possible parton-level $2\to2$ leading-order processes with three commonly used $η_b$ decay channels being implemented. The \pythia interface is used for parton-shower and hadronization to obtain the hadronic events. The FORTRAN codes of this package are generated by FDC (Feynman Diagram Calculation) system automatically.

hep-ph↗

arXiv2008

On Number of Nflation Fields

We study the Nflation model, in which a collection of massive scalar fields drive the inflation simultaneously. We find, when the number of fields is larger than the square of ratio of the Planck scale $M_p$ to the average value $\bar m$ of fields masses, the slow roll inflation region will disappear. This suggests that in order to make Nflation responsible for our observable universe, the number of fields driving the Nflation must be bounded by the above ratio. This result is also consistent with recent arguments from black hole physics.

hep-th↗

arXiv2008

A Uniform Description of the States Recently Observed at B-factories

The newly found states Y(4260), Y(4361), Y(4664) and Z$^\pm$(4430) stir broad interest in the study of spectroscopy in a typical charmonium scale. The Y(4260) which was observed earlier has been interpreted as hybrid, molecular state, and baryonium, etc. In this note we show for the first time that these new structures, which are hard to be interpreted as charmonium states, can be systematically embedded into an extended baryonium picture. According to this assignment, the so far known characters of these states are understandable. And, in the same framework, we make some predictions for experimenters to measure in the future.

hep-ph↗

arXiv2008

Spectrum of Curvature Perturbation of Multi-field Inflation with Small-Field Potential

In this paper, we have studied the spectrum of curvature perturbation of multi-field inflation with general small-field potential. We assume that the isocurvature perturbation may be neglected, and by using the Sasaki-Stewart formalism, we found that the spectrum may be redder or bluer than of its corresponding single field. The result depends upon the values of fields and their effective masses at the horizon-crossing time. We discuss the relevant cases.

astro-ph↗

arXiv2007

Investigation of the bottomonium ground state η_b via its inclusive charm decays

Based on the non-relativistic QCD factorization formalism, we calculate the bottomonium ground state, $η_b$, inclusive charm decays at the leading order in the strong coupling constant $α_s$ and quarkonium internal relative velocity $v$. The inclusive charm pair production in $η_b$ decay is mainly realized through $η_b \to c \bar{c} g$ process, where the charm and anti-charm quarks then dominantly hadronize into charmed hadrons. The momentum distributions of the final states are presented. In this work, we also calculate the $J/ψ$ inclusive production rate in the $η_b$ decays, where the color-octet contribution is found to be very important. We expect this study may shed some light on finding $η_b$ or knowing more about its nature.

hep-ph↗

arXiv2007

Hadronic Production of the Doubly Charmed Baryon $Ξ_{cc}$ with Intrinsic Charm

The effects of the intrinsic charm on the hadronic production of $Ξ_{cc}$ are studied. By taking reasonable intrinsic charm component into account, the change of the theoretical prediction on the production of $Ξ_{cc}$ for LHC and Tevatron is small, but in contrast it may enhance significantly for SELEX. The reason is that the collision energy at LHC and Tevatron is so large that the gluon-gluon fusion sub-process, which is irrelevant to intrinsic charm, becomes dominant. But the situation for SELEX is quite different. Our numerical results for SELEX show that by considering all the contributions from various sub-processes, the predicted cross-section may be enhanced by a factor so big as $10^2$ due to a modulating intrinsic charm being taken into account. Therefore, the hadronic production of $Ξ_{cc}$ at SELEX may be sensitive enough in observing the intrinsic charm inside the incident hadrons.

hep-ph↗

arXiv2007

Hunting eta_b through radiative decay into J/psi

We propose that the radiative decay process, η_b\to J/ψγ, may serve as a clean searching mode for η_b in hadron collision facilities. By a perturbative QCD calculation, we estimate the corresponding branching ratio to be of order 10^{-7}. Though very suppressed, this radiative decay channel in fact has larger branching ratio than the hadronic decay process η_b\to J/ψJ/ψ, which was previously hoped to be a viable mode for ferreting out η_b in Tevatron Run 2. The discovery potential of η_b through this channel seems promising in the forthcoming LHC experiments and maybe even in Tevatron Run 2, thanks to the huge statistics of η_b to be accumulated in these experiments. The same calculational scheme is also used to estimate the branching ratios for the processes η_b (η_c) \to ϕγ.

hep-ph↗

arXiv2006

The Feasibility of Testing LHVTs in Charm Factory

It is commonly believed that the LHVTs can be tested through measuring the Bell's inequalities. This scheme, for the massive particle system, was originally set up for the entangled K^0\bar{K^0} pair system from the ϕfactory. In this Letter we show that the J/Ψ-> K^0\bar{K^0} process is even more realistic for this goal. We analyze the unique properties of J/Ψin the detection of basic quantum effects, and find that it is possible to use J/Ψdecay as a test of LHVTs in the future τ-Charm factory. Our analyses and conclusions are generally also true for other heavy Onium decays.

hep-ph↗

arXiv2006

0^-+ Trigluon Glueball and its Implication for a Recent BES Observation

We calculate the mass of $0^{-+}$ triple-valence-gluon resonance, the trigluon glueball, with QCD sum rules. Its mass is found to be approximately in the region between 1.9 GeV and 2.7 GeV with some theoretical uncertainties. Moreover, it is likely that the new BES measurement of the $p \bar{p}$ enhancement near threshold in the $J/ψ$ decays exhibits the behavior of this trigluon state. Our analyzes favor the baryonium-gluonium mixing picture for the BES observation.

hep-ph↗

arXiv2006

One Explanation for the Exotic State Y(4260)

In this Letter we interpret the Y(4260), a state recently discovered by the BaBar Collaboration that has a mass within the range of conventional charmonium states, as having a molecular-state structure. In our scheme this molecular-like state is not constructed out of two-quark mesons, but rather out of baryons, i.e., the Y(4260) is a baryonium state. With this interpretation, the unusual measured properties of the Y(4260) are easily understood and some further peculiar decay characteristics are predicted.

hep-ph↗

arXiv2006

B-Meson Wavefunction with Contributions from 3-particle Fock States

The B-meson light-cone wavefunctions, $Ψ_{\pm}(ω,z^2)$, are investigated up to the next-to-leading order in Fock state expansion in the heavy quark limit. In order to know the transverse momentum dependence of the B-meson wavefunctions with 3-particle Fock states' contributions, we make use of the relations between 2- and 3- particle wavefunctions derived from the QCD equations of motion and the heavy quark symmetry, especially two constraints derived from the gauge field equation of motion are employed. Our results show that the use of gluon equation of motion can give a constraint on the transverse momentum dependence $χ(ω,\mathbf{k}_\perp)$ of the B-meson wavefunctions, whose distribution tends to be a hyperbola-like curve under the condition $0<c_1<1$, which is quite different from the WW type wavefunctions, whose transverse momentum dependence $χ^{WW}(ω,\mathbf{k}_\perp)$ is merely a delta function. Based on the derived results, we propose a simple model for the B-meson wavefunctions with 3-particle Fock states' contributions.

hep-ph↗

arXiv2006

Estimate of the Hadronic Production of the Doubly Charmed Baryon $Ξ_{cc}$ under GM-VFN Scheme

Hadronic production of the doubly charmed baryon $Ξ_{cc}$ ($Ξ^{++}_{cc}$ and $Ξ^{+}_{cc}$) is investigated under the general-mass variable-flavor-number (GM-VFN) scheme. The gluon-gluon fusion mechanism and the intrinsic charm mechanisms, i.e. via the sub-processes $g+g\to(cc)[^3S_1]_{\bar 3}+\bar{c}+\bar{c}$, $g+g\to(cc)[^1S_0]_6+\bar{c}+\bar{c}$; $g+c\to (cc)[^3S_1]_{\bar 3}+\bar{c}$, $g+c\to (cc)[^1S_0]_6+\bar{c}$ and $c+c\to (cc)[^3S_1]_{\bar 3}+g$, $c+c\to (cc)[^1S_0]_6+g$, are taken into account in the investigation, where $(cc)[^3S_1]_{\bar 3}$ (in color {\bf $\bar 3$}) and $(cc)[^1S_0]_6$ (in color {\bf 6}) are two possible $S$-wave configurations of the doubly charmed diquark pair $(cc)$ inside the baryon $Ξ_{cc}$. Numerical results for the production at hadornic colliders LHC and TEVATRON show that both the contributions from the doubly charmed diquark pairs $(cc)[^1S_0]_6$ and $(cc)[^3S_1]_{\bar 3}$ are sizable with the assumption that the two NRQCD matrix elements are equal, and the total contributions from the `intrinsic' charm mechanisms are bigger than those of the gluon-gluon fusion mechanism. For the production in the region of small transverse-momentum $p_t$, the intrinsic mechanisms are dominant over the gluon-gluon fusion mechanism and they can raise the theoretical prediction of the $Ξ_{cc}$ by almost one order.

hep-ph↗

arXiv2005

Rare decays of B-> J/ψD^() and B->η_c D^()in pQCD Approach

Motivated by the recent measurement of the upper limit of ${B}^0 \to J/ψD$ branching ratio, which is important in accounting for the soft $J/ψ$ production in B decays, we investigate ${B}^0 \to J/ψD^{(\star)}$ and $η_c D^{(\star)}$ decays in perturbative QCD approach based on $k_T$ factorization. Being pure annihilation (W-exchange) decays, these branching ratios are estimated to be at the order of $10^{-5} \sim 10^{-7}$, which are just at the corner of being observable at the $B$ factories. The measurements of these decay channels may help us to understand the QCD dynamics in the corresponding energy scale, especially the reliability of pQCD approach to these processes.

hep-ph↗

arXiv2005

Hadronic Production of $B_c(B^*_c)$ Meson Induced by the Heavy Quarks inside the Collision Hadrons

In general-mass variable-flavor-number (GM-VFN) scheme, the `heavy quark mechanisms' of $B_c(B_c^*)$ meson hadroproduction via the sub-processes $g+c\to B_c(B_c^*)+...$ and $g+\bar{b}\to B_c(B_c^*)+...$ are investigated. In the scheme, possible double counting from these mechanisms and the `light mechanisms' (the gluon-gluon fusion and quark-antiquark annihilation mechanisms) is subtracted properly. The numerical results show that the transverse momentum, $p_t$, distribution of the produced $B_c(B_c^*)$ from the `intrinsic heavy quark mechanisms' (i.e. the heavy quark mechanisms in which the double counting components have been subtracted accordingly) declines faster with the increment of the $p_t$ than that from the `light mechanisms', and only in small $p_t$ region ($p_t\lesssim 7.0$ GeV) the `intrinsic heavy quark mechanisms' themselves may make remarkable contributions. The combined contributions from the `intrinsic heavy quark mechanisms' and the `light mechanisms' to the production are compared with that obtained by the most calculations in literature, which in some sense are within the fixed flavor number (FFN) scheme at leading order, and we find that the production by virtue of the GM-VFN scheme is more or less the same as the one in literature, except in the small $p_t$ region.

hep-ph↗