33191226
Fragmentation function and hadronic production of the heavy supersymmetric hadrons
The light top-squark $\widetilde{t}_1$ may be the lightest squark, and its lifetime may be ‘long enough’ in a kind of SUSY models that have not been ruled out yet experimentally, so colorless ‘supersymmetric hadrons (superhadrons)’ $(\widetilde{t}_1 \overline{q})$ (q is a quark excluding the t-quark) may be formed as long as the light top-squark $\widetilde{t}_1$ can be produced. The fragmentation function of $\widetilde{t}_1$ into heavy ‘supersymmetric hadrons (superhadrons)’ $(\widetilde{t}_1 \overline{Q})$ (Q̄=c̄ or b̄) and hadronic production of the superhadrons are investigated quantitatively. The fragmentation function is calculated precisely. Due to the difference in spin of the SUSY component, the asymptotic behavior of the fragmentation function is different from those of the existing ones. The fragmentation function is also applied to compute the production of heavy superhadrons at the hadronic colliders Tevatron and LHC in the so-called fragmentation approach. The resultant cross-section for the heavy superhadrons is too small to observe at Tevatron, but large enough at LHC, when all the relevant parameters in the SUSY models are taken within the favored region for the heavy superhadrons. The production of ‘light superhadrons’ $(\widetilde{t}_1 \overline{q})$ (q=u,d,s) is also roughly estimated with the same SUSY parameters. It is pointed out that the production cross-sections of the light superhadrons $(\widetilde{t}_1 \overline{q})$ may be much greater than those of the heavy superhadrons, so that even at Tevatron the light superhadrons may be produced in great quantities.
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.
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.
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.
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.
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.
9257590
Black hole mass estimation using a relation between the BLR size and emission line luminosity of AGN
An empirical relation between the broad line region (BLR) size and optical continuum luminosity is often adopted to estimate the BLR size and then the black hole mass of AGNs. However, optical luminosity may not be a good indicator of photoionizing luminosity for extremely radio-loud AGNs because the jets usually contribute significantly to the optical continuum. Therefore, the black hole masses derived for blazar-type AGNs with this method are probably overestimated. Here we first derived a tight empirical relation between the BLR size and the H β  emission line luminosity, $R({\rm light-days})= 24.05(L_{{\rm H}_\beta}/10^{42}$ ergs s$^{-1})^{0.68}$, from a sample of 34 AGNs with the BLR size estimated with the reverberation mapping technique. Then we applied this relation to estimate the black hole masses of some AGNs and found that for many extremely radio-loud AGNs the black hole masses obtained with the $R-L_{\rm H_\beta}$ relation are systematically lower than those derived previously with the $R-L_{5100~{\rm \AA}}$ relation, while for radio-quiet and slightly radio-loud AGNs the results obtained with these two methods are almost the same. The difference of black hole masses estimated with these two relations increases with the radio-loudness for extremely radio-loud AGNs, which is consistent with the fact that their equivalent widths of the H$_{\beta}$ emission line become smaller at greater radio-loudness. If the small H$_{\beta}$ equivalent widths of extremely radio-loud  AGNs are indeed caused by the beaming effect, we argue that the optical emission line luminosity may be a better tracer of ionizing luminosity for blazar-type AGNs and the black hole masses derived with the $R-L_{{\rm H}_\beta}$ relation are probably more accurate.
16592506
CO Line Width and the Black Hole-Bulge Relationship at High Redshift
Recently, it has been suggested that the CO line width [FWHM(CO)] is a surrogate for the bulge velocity dispersion (σ) of the host galaxies of high-redshift quasars, and the black hole-bulge (MBH-σ) relation obtained with this assumption departs significantly from the MBH-σ relation in the local universe. In this study, we first present an investigation of the correlation between the CO line width and the bulge velocity dispersion using a sample of 33 nearby Seyfert galaxies. We find that the formula adopted in previous studies, σ = FWHM(CO)/2.35, is generally not a good approximation. Using it, one may underestimate the value of bulge velocity dispersion significantly when the CO line is narrower than 400 km s-1. By involving the galactic inclination angle i as an additional parameter, we obtain a tight correlation between the inclination-corrected CO line width and the bulge velocity dispersion, namely, FWHM(CO)/ sin i = − (67.16 ± 80.18) + (3.62 ± 0.68) σ. Using this new relation, we can better estimate the bulge velocity dispersion from the CO line width if the galactic inclination is known. We apply this new relation to nine high-redshift quasars with CO line detections and find that they are consistent with the local MBH-σ relation if their inclination angles are around 15°. The possible smaller inclinations of the high-redshift quasars are preferred because of their relatively greater likelihood of detection, and are also consistent with their relatively smaller CO line widths compared to submillimeter galaxies (SMGs) at high redshift having a similar total amount of molecular gas. Future observations are needed to confirm these results.
118440734
Observational Constraints on Agegraphic Dark Energy
In this paper, we use the Type Ia supernova data as well as the CMB and LSS data to constrain the agegraphic dark energy model recently proposed by Cai. Due to its peculiar nature, the parameter $n$ of this model cannot be well constrained by the SNIa data, while the other parameter $\Omega_{m0}$ can be constrained to be $0.34\pm0.04$. When combined with CMB and LSS data, the range of $1\sigma$ confidence level for $n$ is greatly narrowed, albeit still very large. The best fit result is $\Omega_{m0}=0.28\pm0.02$, which is consistent with most observations like WMAP and SDSS, and $n=3.4$, of which a meaningful range of confidence level can not be obtained due to the fact that the contours are not closed. Despite of this result, we conclude that for $n>1$ this model is consistent with SNIa, CMB and LSS observations. Furthermore, the fitting results indicate a generalized definition for the agegraphic dark energy.
2829016
OPTICAL MONITORING OF BL LACERTAE OBJECT OJ 287: A 40 DAY PERIOD?
We present the results of our optical monitoring of the BL Lacertae object OJ 287 during the first half of 2005. The source did not show large-amplitude variations during this period and was in a relatively quiescent state. A possible period of 40 days was derived from its light curves in three BATC wave bands. A bluer-when-brighter chromatism was discovered, which is different from the extremely stable color during the outburst in 1994-1996. The different color behaviors imply different variation mechanisms in the two states. We then revisited the optical data on OJ 287 from the OJ-94 project and also found a probable period of 40 days in its optical variability during the late 1994 outburst. The results suggest that two components contribute to the variability of OJ 287 during its outburst state. The first component is the normal blazar variation. This component has an amplitude similar to that of the quiescent state and also may share a similar periodicity. The second component can be taken as a "low-frequency modulation" to the first component. It may be induced by the interaction of the assumed binary black holes in the center of this object. The 40 day period may be related to the helical structure of the magnetic field at the base of the jet or to the orbital motion close to the central primary black hole.
2515645
The Black Hole Fundamental Plane: Revisited with a Larger Sample of Radio and X-Ray-Emitting Broad-Line AGNs
We use a recently released SDSS catalog of X-ray-emitting AGNs in conjunction with the FIRST radio survey to investigate the black hole (BH) fundamental plane relationship between the 1.4 GHz radio luminosity ( -->Lr), 0.1-2.4 keV X-ray luminosity ( -->LX), and black hole mass ( -->M), namely, -->log Lr = ξRXlog LX + ξRMlog M + constant . For this purpose, we compile a large sample of 725 broad-line AGNs, which consists of 498 radio-loud sources and 227 radio-quiet sources. We confirm that radio-loud objects have a steeper slope ( -->ξRX) with respect to radio-quiet objects and that the dependence of the BH fundamental plane on the BH mass ( -->ξRM) is weak. We also find tight correlation with a similar slope between the soft X-ray luminosity and broad emission-line luminosity for both radio-loud and radio-quiet AGNs, which implies that their soft X-ray emission is unbeamed and probably related to the accretion process. With the current larger sample, we find that there is no clear evidence of evolution for radio-quiet AGNs, while for radio-loud ones there is a weak trend in which -->ξRM decreases as the redshift increases. This may be understood in part as due to the observed evolution of the radio spectral index as a function of redshift. Finally, we discuss the relativistic beaming effect and other uncertainties related to the BH fundamental plane. We conclude that, although it does introduce scatter into the fundamental plane relation, Doppler boosting alone is not enough to explain the observed steeper value of -->ξRX in the radio-loud subsample with respect to the radio-quiet ones.