197452857
Renormalization group improved QCD prediction for $\Upsilon(1S)$ leptonic decay
The complete next-to-next-to-next-to-leading order short-distance and bound-state QCD corrections to $\Upsilon(1S)$ leptonic decay rate $\Gamma(\Upsilon(1S)\to \ell^+\ell^-)$ has been finished by Beneke {\it etal.} [5]. Based on those improvements, we present a renormalization group (RG) improved pQCD prediction for $\Gamma(\Upsilon(1S)\to \ell^+\ell^-)$ by applying the principle of maximum conformality (PMC). The PMC is based on RG-invariance and is designed to solve the renormalization scheme and scale ambiguities. After applying the PMC for $\Upsilon(1S)$ leptonic decay, all known-type of $\beta$-terms at all orders, which are controlled by the RG-equation, are resummed to determine optimal renormalization scales for its strong running coupling at each perturbative order. We then achieve a more convergent pQCD series, a scheme-independent and more accurate pQCD prediction, i.e. $\Gamma_{\Upsilon(1S) \to e^+ e^-}|_{\rm PMC} = 1.361^{+0.154}_{-0.214}$ keV, where the uncertainty is squared average of the mentioned pQCD error sources. This RG-improved pQCD prediction agrees well with the experimental measurement within errors.
5502533
A trick to improve the efficiency of generating unweighted Bc events from BCVEGPY
In the present paper, we provide an addendum to improve the efficiency of generating unweighted events within PYTHIA environment for the generator BCVEGPY2.1 [C.H. Chang, J.X. Wang, X.G. Wu, Comput. Phys. Commun. 174 (2006) 241]. This trick is helpful for experimental simulation. Moreover, the BCVEGPY output has also been improved, i.e. one Les Houches Event common block has been added so as to generate a standard Les Houches Event file that contains the information of the generated Bc meson and the accompanying partons, which can be more conveniently used for further simulation.
119268284
Uncertainties in estimating the indirect production of Bc and its excited states via top quark decays at CERN LHC
Abstract Main theoretical uncertainties in estimating the indirect production of ( b c ¯ ) -quarkonium ( B c − meson and its excited states) via top quark decays, t → ( b c ¯ ) + c + W + , are studied within the non-relativistic QCD framework. It is found that the dimensionless reduced decay width for a particular ( b c ¯ ) -quarkonium state, Γ ¯ n = Γ n / Γ t → W + + b , is very sensitive to the c -quark mass, while the uncertainties from the b -quark and t -quark masses are small, where n stands for the eight ( b c ¯ ) -quarkonium states up to O ( v 4 ) : | ( b c ¯ ) ( S 0 1 ) 1 〉 , | ( b c ¯ ) ( S 1 3 ) 1 〉 , | ( b c ¯ ) ( P 1 1 ) 1 〉 , | ( b c ¯ ) ( P J 3 ) 1 〉 (with J = ( 1 , 2 , 3 ) ), | ( b c ¯ ) ( S 0 1 ) 8 g 〉 and | ( b c ¯ ) ( S 1 3 ) 8 g 〉 respectively. About 10 8 t t ¯ -pairs shall be produced per year at CERN LHC, if adopting the assumption that all the higher Fock states decay to the ground state with 100% probability, then we shall have ( 1.038 −0.782 +1.353 ) × 10 5 B c − events per year. So the indirect production provides another important way to study the properties of B c − meson in comparison to that of the direct hadronic production at CERN LHC.
119260697
Photoproduction of doubly heavy baryon at the ILC
A bstractIn the present paper, we make a detailed study on the doubly heavy baryon photoproduction in the future e+e− International Linear Collider (ILC). The baryons Ξcc, Ξbc, and Ξbb are produced via the channel γγ→ΞQQ′+Q¯′+Q¯$$ \gamma \gamma \to {\Xi}_{QQ\prime }+\overline{Q}^{\prime }+\overline{Q} $$, where Q and Q′ stand for heavy c or b quark, respectively. As for the ΞQQ′-baryon production, it shall first generate a (QQ′)[n]-diquark and then form the final baryon via fragmentation, where [n] stands for the color- and spin- configurations for the (QQ′)-diquark states. According to the non-relativistic QCD theory, four diquark configurations shall provide sizable contributions to the baryon production, e.g., [n] equals 3S13¯,1S06,3S16,or1S03¯$$ {\left[{}^3{S}_1\right]}_{\overline{3}},\;{\left[{}^1{S}_0\right]}_6,\;{\left[{}^3{S}_1\right]}_6,\;\mathrm{or}\kern0.37em {\left[{}^1{S}_0\right]}_{\overline{3}} $$, respectively. We adopt the improved helicity amplitude approach for the hard scattering amplitude to improve the calculation efficiency. Total and differential cross sections of those channels, as well as the theoretical uncertainties, are presented. We show that sizable amounts of baryon events can be generated at the ILC, i.e., about 2.0 × 106 Ξcc, 2.2 × 105 Ξbc, as well as 3.0 × 103 Ξbb events are to be generated in one operation year for S=500$$ \sqrt{S}=500 $$ GeV and ℒ ≃ 1036 cm−2s−1.
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.
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.
450968
Studying the scalar bound states of KK system in Bethe-Salpeter formalism
We study the possible bound states of the KK system in the Bethe-Salpeter formalism in the ladder and instantaneous approximations. We find that the bound states exist. However, these bound states have very small decay widths. Therefore, besides the possible KK component, there may be some other structures in the observed f{sub 0}(980) and a{sub 0}(980)
54195518
Twist-3 distribution amplitudes of the pion and kaon from the QCD sum rules
Abstract.Twist-3 distribution amplitudes of the pion and kaon are studied in this paper. We calculate the first several moments for the twist-3 distribution amplitudes ($ \phi_{p,\sigma}^\pi$ and $ \phi_{p,\sigma}^K$) of the pion and kaon by applying the QCD sum rules. Our results show that (i) the first three moments of $ \phi_p^K $ and the first two moments of $ \phi_p^\pi $ and $ \phi_\sigma^{\pi,K} $ of the pion and kaon can be obtained with 30$\%$ uncertainty; (ii) the fourth moment of the $ \phi_p^\pi $ and the second moment of the $ \phi_\sigma^K $ can be obtained when the uncertainty are relaxed to 35$\%$; (iii) the fourth moment of the $ \phi_\sigma^\pi $ can be obtained only when the uncertainty are relaxed to 40$\%$; (iv) we have $m_{0\pi}^p = 1.10\pm 0.08 {\mathrm {GeV}}$ and $m_{0K}^p = 1.25\pm 0.15 {\mathrm {GeV}}$ after including the $\alpha_{\mathrm {s}}$-corrections to the perturbative part. These moments will be helpful for constructing the twist-3 wave functions of the pion and kaon.
119292600
SDSS quasars in the WISE preliminary data release and quasar candidate selection with optical/infrared colors
We present a catalog of 37,842 quasars in the Sloan Digital Sky Survey (SDSS) Data Release 7, which have counterparts within 6'' in the Wide-field Infrared Survey Explorer (WISE) Preliminary Data Release. The overall WISE detection rate of the SDSS quasars is 86.7%, and it decreases to less than 50.0% when the quasar magnitude is fainter than i = 20.5. We derive the median color-redshift relations based on this SDSS-WISE quasar sample and apply them to estimate the photometric redshifts of the SDSS-WISE quasars. We find that by adding the WISE W1- and W2-band data to the SDSS photometry we can increase the photometric redshift reliability, defined as the percentage of sources with photometric and spectroscopic redshift difference less than 0.2, from 70.3% to 77.2%. We also obtain the samples of WISE-detected normal and late-type stars with SDSS spectroscopy, and present a criterion in the z – W1 versus g – z color-color diagram, z – W1 > 0.66(g – z) + 2.01, to separate quasars from stars. With this criterion we can recover 98.6% of 3089 radio-detected SDSS-WISE quasars with redshifts less than four and overcome the difficulty in selecting quasars with redshifts between 2.2 and 3 from SDSS photometric data alone. We also suggest another criterion involving the WISE color only, W1 – W2 > 0.57, to efficiently separate quasars with redshifts less than 3.2 from stars. In addition, we compile a catalog of 5614 SDSS quasars detected by both WISE and UKIDSS surveys and present their color-redshift relations in the optical and infrared bands. By using the SDSS ugriz, UKIDSS, YJHK, and WISE W1- and W2-band photometric data, we can efficiently select quasar candidates and increase the photometric redshift reliability up to 87.0%. We discuss the implications of our results on the future quasar surveys. An updated SDSS-WISE quasar catalog consisting of 101,853 quasars with the recently released WISE all-sky data is also provided.
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).
119328486
The Fundamental Plane of Spiral Galaxies: Search from Observational Data
The fundamental plane of spiral galaxies was searched from observational data, which can be approximately represented in observational parameters by L proportional to V-2 R, where L, R, and V are the luminosity, the linear size of galactic disk, and the rotation velocity. This plane exists at all optical bands in our samples of more than 500 spiral galaxies in total. It is more fundamental than the relationship between any two of the parameters, and can reduce the residual of the Tully-Fisher L-V relations by about 50%. Noticed that the power index of V is doubled from that of R, which implies that the total mass and the mass distribution of galaxies plays an important role in forming the fundamental plane. Involving the third parameter of galactic size has a strong physical implication on galaxy formation and the dark-mass distribution.