119119923
Explaining the anomalous $\Upsilon(5S)\to \chi_{bJ}\omega$ decays through the hadronic loop effect
In this work, we carry out the study on $\Upsilon(5S)\to \chi_{bJ}\omega$ ($J=0,1,2$) by considering the hadronic loop mechanism. Our results show that the Belle's preliminary data of the branching ratios for $\Upsilon(5S)\to \chi_{bJ}\omega$ can be well reproduced in our calculation with a common parameter range, which reflects the similarity among these $\Upsilon(5S)\to \chi_{bJ}\omega$ decays of concern.
119249008
Does the enhancement observed in $\gamma\gamma\to D\bar{D}$ contain two P-wave higher charmonia?
We solve a new puzzle raised by the observation of an enhancement structure Z(3930) in $\gamma\gamma\to D\bar{D}$. If categorizing Z(3930) as χc2(2P), as suggested by Belle and BaBar, we must explain why χc0(2P) dominantly decaying into $D\bar{D}$ is missing in the $D\bar{D}$ invariant mass spectrum. In this work, we propose that the Z(3930) enhancement structure may contain two P-wave higher charmonia χc0(2P) and χc2(2P). We show that this assumption is supported by our analysis of the $D\bar{D}$ invariant mass spectrum and cosθ∗ distribution of $\gamma\gamma\to D\bar{D}$. This observation would not only provide valuable information of two P-wave higher charmonia χc0(2P) and χc2(2P), but also serve as the crucial test of our novel proposal to the observed enhancement structure Z(3930), especially at the forthcoming BelleII and the approved SuperB.
31555802
Mixing of Pentaquark and Molecular States
There are experimental evidences for the existence of narrow states Θ+ and Θc with the same quantum numbers of uudds̄ and uuddc̄ pentaquarks and also NK(∗) and ND(∗) molecular states. Their masses deviate from many theoretical estimates of the pure pentaquark and molecular states. In this work we study the possibility that the observed Θ+ and Θc are mixtures of pure pentaquark and molecular states. The mixing parameters are in general related to non-perturbative QCD which are not calculable at present. We determine them by fitting data from known states and then generalize the mechanism to Θb to predict its mass and width. The mixing mechanism can also naturally explain the narrow width for Θ+ and Θc through destructive interferences, even if the pure pentaquark and molecular states have much larger decay widths. We also briefly discuss the properties of the partner eigenstates of Θ+ and Θc and the possibility of experimentally observe them. Moreover, probable consequences of multi-state mixing are also addressed.
119155043
Effects of hadronic loops on the direct CP violation of $B_c$
It is well-known that the final state interaction plays an important role in the decays of B meson. The contribution of the final state interaction, which is supposed to be long-distance effects, to the concerned processes can interfere with that of the short-distance effects produced via the tree and/or loop diagrams at quark-gluon level. The interference may provide a source for the direct CP violation A{sub CP} in the process B{sub c}{sup +}{yields}D{sup 0}{pi}{sup +}. We find that a typical value of A{sub CP} when the final state interaction effect is taken into account can be about -22% which is different from that without the final state interaction effect. Therefore, when we extract information on CP violation from the data which will be available at the Large Hadron Collider beauty experiment (LHCb) and the new experiments in B factories, the contribution from the final state interaction must be included. This study may be crucial for searching new physics in the future.
28437592
A possible global group structure for exotic states
Based on the fact that the long expected pentaquark which possesses the exotic quantum numbers of $$B=1$$B=1 and $$S=1$$S=1 was not experimentally found, although exotic states of $$XYZ$$XYZ have been observed recently, we conjecture that the heavy flavors may play an important role in stabilizing the hadronic structures beyond the traditional $$q\bar{q}$$qq¯ and $$qqq$$qqq composites.
51398146
Some properties of the newly observed X(1835) state at BES
Recently the BES collaboration has announced the observation of a resonant state in the π+π-η’ spectrum in J/ψ→γπ+π-η’ decay. Fitting the data with a 0-+ state, the mass is determined to be 1833.7 MeV with 7.7σ statistic significance. This state is consistent with the one extracted from previously reported pp̄ threshold enhancement data in J/ψ→γpp̄. We study the properties of this state using QCD anomaly and QCD sum rules, assuming X(1835) to be a pseudoscalar, and we show that it is consistent with the data. We find that this state has a sizeable matrix element $\langle0|G\widetilde{G}|G_{\text{p}}\rangle$, leading to branching ratios of (2.61–7.37)×10-3 and (2.21–10.61)×10-2 for J/ψ→γGp and for Gp→π+π-η′, respectively. Combining the calculated branching ratio of J/ψ→γGp and data on threshold enhancement in J/ψ→γpp̄, we determine the coupling for the Gp–p–p̄ interaction. We finally study the branching ratios of the other J/ψ→γ+three mesons decay modes. We find that J/ψ→γGp→γ(π+π-η,KKπ0) can provide useful tests for the mechanism proposed.
119303160
On the relation of accretion rate and spin induced jet power in low luminosity AGN
From Liu and Han (2014), the accretion-dominated jet power has a linear proportionality with the accretion rate, whereas the power law index is <=0.5 at lower accretion rate. Attributing the jet power in low accretion rate AGN to the black hole spin, it implies that the jet power has a flatter spectrum than the accretion-dominated jet versus the accretion rate. The black hole must be spinning rapidly for producing such jet power efficiently, and this may allow us to find high-spin black holes in the radio-loud low-luminosity AGN.
118434102
Study of baryon octet electromagnetic form factors in perturbative chiral quark model
The electromagnetic properties of baryon octet are studied in the perturbative chiral quark model (PCQM). The relativistic quark wave function is extracted by fitting the theoretical results of the proton charge form factor to experimental data and the predetermined quark wave function is applied to study the electromagnetic form factors of other octet baryons as well as magnetic moments, charge and magnetic radii. The PCQM results are found, based on the predetermined quark wave function, in good agreement with experimental data.
118442162
The two-body hadronic decays of Bc meson in the perturbative QCD approach: a short review
Along with the running of Large Hadron Collider (LHC) located at CERN in November 2009, a large number of data samples of $$B_c$$Bc meson have been collected and some hadronic $$B_c$$Bc decay modes have been measured by the LHC experiments. In view of the special and important roles of $$B_c$$Bc meson decays playing in the heavy flavor sector, we here give a short review on the status of two body hadronic decays $$B_c \rightarrow M_1 M_2$$Bc→M1M2 at both experimental and theoretical aspects. For the theoretical progresses, specifically, we will show lots of theoretical studies on two body hadronic $$B_c$$Bc decays involving pseudoscalar, vector, scalar, axial-vector, even tensor meson(s) in the final states by employing the perturbative QCD (pQCD) factorization approach. We will present a general analysis about the two-body hadronic decays of the heavy $$B_c$$Bc meson and also provide some expectations for the future developments.
118587112
Extremely metal-poor star candidates in the SDSS
For a sample of metal-poor stars ( 3.3 � (Fe/H) � 2.2) that have high- resolution spectroscopic abundance determinations, we have measured equivalent widths of the Ca II K, Mg I b and near-infrared Ca II triplet lines using low-resolution spectra from the Sloan Digital Sky Survey (SDSS), calculated effective temperatures from (g z)0 color, deduced stellar surface gravities by fitting stellar isochrones, and determined metallicities based on the aforementioned quantities. Metallicities thus derived from the Ca II K line are in much better agreement with the results deter- mined from high-resolution spectra than the values given in the SDSS Data Release 7. The metallicities derived from the Mg I b lines have a large dispersion owing to the large measurement errors, whereas those deduced from the Ca II triplet lines are too high due to both non-local thermodynamical equilibrium (NLTE) effects and mea- surement errors. Abundances after correction for the NLTE effect for the Mg I b lines and Ca II triplet lines are also presented. Following this method, we have identified six candidates of ultra-metal-poor stars with (Fe/H) � 4.0 from a sample of 166 metal-poor star candidates. One of them, SDSS J102915+172927, was recently con- firmed to be an ultra-metal-poor ((Fe/H) < 4.0) star with the lowest metallicity ever measured. Follow-up high-resolution spectroscopy for the other five ultra-metal-poor stars in our sample will therefore be of great interest.
119117794
Charmless hadronic $B \to (f_1(1285),f_1(1420)) P$ decays in the perturbative QCD approach
We study 20 charmless hadronic $B \to f_1 P$ decays in the perturbative QCD(pQCD) formalism with $f_1$ representing axial-vector mesons $f_1(1285)$ and $f_1(1420)$ that result from a mixing of quark-flavor $f_{1q}$ and $f_{1s}$ states with the angle $\phi_{f_1}$. The estimations of branching ratios and CP asymmetries of the considered $B \to f_1 P$ decays are presented in the pQCD approach with $\phi_{f_1} \sim 24^\circ$ from recently measured $B_{d/s} \to J/\psi f_1(1285)$ decays. It is found that (a) the tree(penguin) dominant $B^+ \to f_1 \pi^+(K^+)$ decays with large branching ratios[${\cal O}(10^{-6})$] and large direct CP violations(around 14% $\sim$ 28% in magnitude) simultaneously are believed to be clearly measurable at the LHCb and Belle II experiments; (b) the $B_d \to f_1 K_S^0$ and $B_s \to f_1 (\eta, \eta^{\prime})$ decays with nearly pure penguin contributions and safely negligible tree pollution also have large decay rates in the order of $10^{-6} \sim 10^{-5}$, which can be confronted with the experimental measurements in the near future; (c) as the alternative channels, the $B^+ \to f_1 (\pi^+, K^+)$ and $B_d \to f_1 K_S^0$ decays have the supplementary power in providing more effective constraints on the Cabibbo-Kobayashi-Maskawa weak phases $\alpha$, $\gamma$, and $\beta$ correspondingly, which are explicitly analyzed through the large decay rates and the direct and mixing-induced CP asymmetries in the pQCD approach and are expected to be stringently examined by the measurements with high precision. The complete abstraction can be found in the paper.