28851116
GENXICC2.1: An improved version of GENXICC for hadronic production of doubly heavy baryons
We present an improved version of GENXICC, which is a generator for hadronic production of the doubly heavy baryons $\Xi_{cc}$, $\Xi_{bc}$ and $\Xi_{bb}$ and has been raised by C.H. Chang, J.X. Wang and X.G. Wu [Comput. Phys. Commun. 177 (2007) 467; Comput. Phys. Commun. 181 (2010) 1144]. In comparison with the previous GENXICC versions, we update the program in order to generate the unweighted baryon events more effectively under various simulation environments, whose distributions are now generated according to the probability proportional to the integrand. One Les Houches Event (LHE) common block has been added to produce a standard LHE data file that contains useful information of the doubly heavy baryon and its accompanying partons. Such LHE data can be conveniently imported into PYTHIA to do further hadronization and decay simulation, especially, the color-flow problem can be solved with PYTHIA8.0.
118668401
Determination of the pion distribution amplitude
Currently, not enough is known to determine the hadron distribution amplitudes (DAs)-which are universal physical quantities in the high-energy processes involving hadrons-in order to apply perturbative QCD to exclusive processes. Even for the simplest pion, one cannot discriminate between different DA models. Conversely, one expects that processes involving pions can in principle provide strong constraints on the pion DA. For example, the pion-photon transition form factor (TFF) can get accurate information about the pion wave function or DA due to the single pion in this process. However, the data from Belle and BABAR show a big difference regarding this TFF in high-Q(2) regions; at present, they are unable to determine the pion DA. In the present paper, we think it is still possible to determine the pion DA as long as we perform a combined analysis of the existing data of the processes involving pions, such as pi -> mu(nu) over bar, pi(0) -> gamma gamma, B -> pi l nu, D -> pi l nu, etc. Based on the revised light-cone harmonic oscillator model, a convenient DA model is suggested, whose parameter B-which dominates its longitudinal behavior for phi(pi)(x, mu(2))-can be determined in a definite range by these processes. A light-cone sum rule analysis of the semileptonic processes B -> pi l nu and D -> pi l nu leads to a narrow region B = [0.01; 0.14], which indicates a slight deviation from the asymptotic DA. Then, one can predict the behavior of the pion-photon TFF in high-Q(2) regions which can be tested in future experiments. This method provides the possibility that the pion DA will be finally determined by a global fit.
118560703
Application of the principle of maximum conformality to the top-quark forward-backward asymmetry at the Tevatron
¯p¯ FB at the Tevatron will be increased by 42% in comparison to the previous estimates obtained by using conventional scale setting; i.e. we obtain A t ¯PMC FB ≃ 12.5% and A p¯ p,PMC FB ≃ 8.28%. Moreover, we obtain A t ¯ t,PMC FB (Mt¯ > 450 GeV) ≃ 35.0%. These predictions have a 1�-deviation from the present CDF and D0 measurements; the large discrepancies of the top quark forward-backward asymmetry between the Standard Model estimate and the CDF and D0 data are thus greatly reduced.
118633399
Next-to-leading order QCD corrections for the charmonium production via the channel $e^+ e^- \to H(|c\bar{c}\rangle) + \gamma$ round the $Z^0$ peak
In our previous work [2], it has been found that sizable charmonium events via the channel $e^+e^- \to \gamma^*/Z^0 \to H(|c\bar{c}\rangle) +\gamma$ can be produced at the suggested super $Z$ factory, where $H(|c\bar{c}\rangle)$ represents the dominant color-singlet $S$-wave and $P$-wave charmonium states $J/\psi$, $\eta_c$, $h_c$ and $\chi_{cJ}$ ($J=0, 1, 2$), respectively. As an important step forward, in the present paper, we present a next-to-leading order (NLO) QCD analysis within the framework of nonrelativistic QCD. In different to the case of $B$ factory in which the single charmonium production is dominated by the channel via a virtual photon, at the super $Z$ factory, its cross-section is dominated by the channel via a $Z^0$ boson. Estimations up to NLO level are done at both the $B$ factory and the super $Z$ factory experimental conditions. We observe that the NLO distributions have the same shapes as those of LO distributions, but their differences are sizable. This indicates that a NLO calculation is necessary and important to achieve a more accurate estimation. Due to $Z^0$ boson resonance effect, at the super $Z$ factory with a high luminosity up to $10^{36}{\rm cm}^{-2}{\rm s}^{-1}$, when summing all the color-singlet states' contribution together, one may observe about $8.0\times10^{4}$ charmonium events via the channel $e^+e^-\to Z^0 \to H(|c\bar{c}\rangle)+\gamma$ in one operation year. Then, such super $Z$ factory could provide another useful platform to study the charmonium properties, even for the higher charmonium states.
118446028
Z0 boson decays to $B^{(*)}_{c}$ meson and its uncertainties
The planned new e+e− collider with high luminosity shall provide another useful platform to study the properties of the doubly heavy Bc meson in addition to the hadronic colliders as LHC and TEVATRON. In the ‘New Trace Amplitude Approach’, we calculate the production of the spin-singlet Bc and the spin-triplet $B^{*}_{c}$ mesons through the Z0 boson decays, where uncertainties for the production are also discussed. Our results show $\varGamma_{(^{1}S_{0})}=81.4^{+102.1}_{-40.5}$ KeV and $\varGamma_{(^{3}S_{1})}=116.4^{+163.9}_{-62.8}$ KeV, where the errors are caused by varying mb and mc within their reasonable regions.
197508077
Twist-3 Distribution Amplitudes of Scalar Mesons within the QCD Sum Rules and Its Application to the $B \to S$ Transition Form Factors
We investigate the twist-3 light cone distribution amplitudes (LCDAs) of the scalar mesons $a_0$, $K^{\ast}_0$ and $f_0$ within the QCD sum rules. The sum rules are improved by a consistent treatment of the sizable mass effects. Adopting the valence quark component $(\bar{q}_1 q_2)$ as the dominant structure of the scalar mesons, our estimation for their masses are close to the measured $a_0(1450)$, $K^{\ast}_0(1430)$ and $f_0(1710)$. From the sum rules, we obtain the first two non-zero moments of the twist-3 DAs $\phi^{s,\sigma}_{a_0}$: $ =0.369 (0.245)$ and $ =0.203 (0.093)$; those of the twist-3 DAs $\phi_{K^*_0}^{s,\sigma}$: $ =0.004 (0.355)$ and $ =0.018 (0.207)$; and those of the twist-3 DAs $\phi_{f_0}^{s,\sigma}$: $ =0.335 (0.212)$ and $ =0.196 (0.088)$, respectively. As an application of these twist-3 LCDAs, we study the $B \to S$ transition form factors by introducing proper chiral currents in the correlator, which is constructed such that the twist-3 DAs give dominant contribution and the twist-2 DAs make negligible contribution. Our results of the $B \to S$ form factors at the large recoil region $q^2 \simeq 0$ are consistent with those obtained in the literature.
119073126
Improved approach to the heavy to light form-factors in the light cone QCD sum rules
A systematic analysis shows that the main uncertainties in the form factors are due to the twist-3 wave functions of the light mesons in the light-cone QCD sum rules. We propose an improved approach, in which the twist-3 wave functions do not make any contribution and therefore the possible pollution by them can be avoided, to reexamine B-->pi semileptonic form factors. Also, a comparison between previous results and our results from the light-cone QCD sum rules is made. Our method will be beneficial to the precise extraction of \V-ub\ from the experimental data on the processes B-->pil )over tilde>(l).
118371472
Holographic entanglement entropy and thermodynamic instability of planar R-charged black holes
The holographic entanglement entropy of an infinite strip subsystem on the asymptotic AdS boundary is used as a probe to study the thermodynamic instabilities of planar R-charged black holes (or their dual field theories). We focus on the single-charge AdS black holes in $D=5$, which correspond to spinning D3-branes with one non-vanishing angular momentum. Our results show that the holographic entanglement entropy indeed exhibits the thermodynamic instability associated with the divergence of the specific heat. When the width of the strip is large enough, the finite part of the holographic entanglement entropy as a function of the temperature resembles the thermal entropy, as is expected. As the width becomes smaller, however, the two entropies behave differently. In particular, there exists a critical value for the width of the strip, below which the finite part of the holographic entanglement entropy as a function of the temperature develops a self-intersection. We also find similar behavior in the single-charge black holes in $D=4$ and $7$.
10640583
Stability of a hot two-temperature accretion disc with advection
The effects of radial advection and thermal diffusion were considered in investigating the linear stability of an optically thin, two-temperature accretion disc. If the disc has only very little advection, we proved that the thermal instability exists when the disc is geometrically thin. But it dispears in a geometrically slim disc if the thermal diffusion was considered. Moreover, if the disc is advection dominated, the thermal instability does not exist. In addition, we found that the instabilities of inertial-acoustic modes exist only in a geometrically thin disc or an advection-dominated disc with low Mach number, whereas the Lightman & Eardley viscous instability always dispears in a two-temperature disc. A simple comparison also showed that an optically thin, bremsstrahlung cooling dominated disc is generally more thermally unstable than a two-temperature disc if it is not advection-dominated.
118599552
Some mass relations for mesons and baryons in Regge phenomenology
In the quasilinear Regge trajectory ansatz, some useful linear mass inequalities, quadratic mass inequalities, and quadratic mass equalities are derived for mesons and baryons. Based on these relations, mass ranges of some mesons and baryons are given. The masses of bc and ss belonging to the pseudoscalar, vector, and tensor meson multiplets are also extracted. The J{sup P} of the baryon {xi}{sub cc}{sup +}(3520) is assigned to be (1/2){sup +}. The parameters of the (1/2){sup +} and (3/2){sup +} SU(4) baryon trajectories are extracted and the masses of the orbital excited baryons lying on the (1/2){sup +} and (3/2){sup +} trajectories are estimated. The J{sup P} assignments of baryons {xi}{sub c}(2980), {xi}{sub c}(3055), {xi}{sub c}(3077), and {xi}{sub c}(3123) are discussed. The predictions are in reasonable agreement with the existing experimental data and those suggested in many other different approaches. The mass relations and the predictions may be useful for the discovery of the unobserved meson and baryon states and the J{sup P} assignment of these states.
5433221
A feedback compression star formation model and the black hole-bulge relations
We present a feedback compression model to describe galactic spheroid formation and its relation with the central nuclear activity. We suggest that the star formation itself can serve as the positive feedback in some extremely dense region to trigger the starburst. The star formation rate, as well as the related stellar feedback-induced turbulence, will be maximized under the regulation of the background dark halo's gravity. There is also stellar feedback acting inward to confine and obscure the central black hole (BH) until the BH grows sufficiently large to satisfy a balance condition between the accretion disk wind and the inward stellar feedback. The extremely vigorous star formation activity, the BH-bulge relations, the maximum velocity dispersion, and the maximum BH mass are investigated on the basis of such a scenario and are found to be consistent with observations.