Jost functions for quarkonium

We examine the interaction in quarkonium by means of the potential V(r)=–/r+ r+V_o. Within the framework of the Fuda generalization of the van Leeuwen-Reiner approach, the off-shell Jost functions and the off-shell and half-off-shell T-matrices are derived.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, pp. 57–60, May, 1986.     

W boson inclusive decays to quarkonium and $B_{c}^{(*)}$ meson at the LHC

In this paper, the production rates of quarkonia η _c , J/ψ, η _b , ϒ and B_c^(*)B_{c}^{(*)} mesons through W ⁺ boson decay at the LHC are calculated, at the leading order in both the QCD coupling α _s and in v, the typical velocity of the heavy quark inside mesons. It shows that a sizable number of quarkonia and B_c^(*)B_{c}^{(*)} mesons from W ⁺ boson decay will be produced at the LHC. Comparison with the predictions by using quark fragmentation mechanism is also discussed. Results show that, for the charmonium production through W ⁺ decay, the difference between predictions by the fragmentation mechanism and complete leading order calculation is around 3%, and it is insensitive to the uncertainties of theoretical parameters; however, for the bottomonium and B_c^(*)B_{c}^{(*)} productions, the difference cannot be ignored as the fragmentation mechanism is less applicable here due to the relatively large ratio m _b /m _w .     

A new potential for quarkonium

We suggest a new potential for bound states of a heavy quark-antiquark pair. This potential has a logarithmic piece interpolating between a confining linear part at large distances and an asymptotically free Coulombic part at short distances. We show that the logarithmic piece of our potential considerably influences the $\text{ψ}\text{J}$-family spectrum, and dominates the ?-family. An excellent fit to the $\text{psi;}\text{J}$ data below the DD? threshold and the correct ?′?? mass splitting is obtained in a natural way. We suggest a possible test for this new potential through the leptonic widths of the ?-family.     

WKB approximation for a quarkonium equation

A fourth-order differential equation recently proposed for describing quarkonia is studied. The eigenvalue spectrum is self-similar. A WKB approximation reproduces the spectrum and the so-called magic numbers which characterize the self-similarity.     

Effective field theories for the heavy quarkonium

We briefly review how nonrelativistic effective field theories give us a definition of the QCD potentials and a coherent field-theory-derived quantum-mechanical scheme to calculate the properties of bound states made by two or more heavy quarks. In this framework heavy quarkonium properties depend only on the QCD parameters (quark masses and α _s ) and nonpotential corrections are systematically accounted for. The relation between the form of the nonperturbative potentials and the low-energy QCD dynamics is also discussed.     

Supermodels for early LHC

We investigate which new physics signatures could be discovered in the first year of the LHC, beyond the expected sensitivity of the Tevatron data by the end of 2010. We construct “supermodels”, for which the LHC sensitivity even with only 10 pb⁻¹ useful luminosity is greater than that of the Tevatron with 10 fb⁻¹. The simplest supermodels involve s  -channel resonances in the quark–antiquark and especially in the quark–quark channels. We concentrate on easily visible final states with small standard model backgrounds, and find that there are simple searches, besides those for Z^′$Z^{\prime }$ states, which could discover new physics in early LHC data. Many of these are well-suited to test searches for “more conventional” models, often discussed for multi-fb⁻¹ data sets.     

A new phenomenological potential for heavy quarkonium

We suggest a new phenomenological potential for heavy quarkonium. The potential has a Lorentz vector term motivated by experimental leptonic widths for vector mesons and perturbative QCD at short distances and a Lorentz scalar term responsible for quark confinement at large distances. Using this potential we calculate the energy levels, leptonic decay widths, radiative transition rates and hadronic decay rates of the \(c\bar c, b\bar b\) and \(t\bar t\) systems. Most results agree well with the experiment.     

Renormalization group improved predictions for quarkonium decay

A method recently suggested to resolve the ambiguity related to scheme dependence in perturbative QCD is applied to calculations of radiative corrections to quarkonium decay. Renormalization group improved predictions are given for the ratio $\text{R=Г(}{}^1\text{S}{}_0\text{→had)/Г(}{}^3\text{S}{}_1\text{→had)}$, as a function of $\text{λ}{}_{\mathrm{<mtext>MS</mtext>}}$. The values obtained are substantially larger than in conventional schemes. One finds in particular that R>182 for charmonium, and R>174 for bottomium, independently of the value of the quark mass and $\text{λ}{}_{\mathrm{<mtext>MS</mtext>}}$. It follows that $\text{Г(}\text{n}{}_{\mathrm{c}}\text{→}\text{had}\text{)>6.9}\text{MeV}$ and $\text{Г(}\text{n}{}_{\mathrm{b}}\text{→}\text{had}\text{)>3.6}\text{MeV}$. Values of the wave function at the origin as a function of $\text{λ}{}_{\mathrm{<mtext>MS</mtext>}}$ are also extracted from the measured gluonic width of the ³S₁ state. An upper bound for $\text{λ}{}_{\mathrm{<mtext>MS</mtext>}}$ is obtained under some assumptions.     

Heavy quarkonium effective theory

We formulate a QCD-based effective theory approach to heavy quarkonia-like systems as $\bar cc$ and $\bar bb$ resonances andB _c states. We apply the method to inclusive decays, working out a few examples in detail.     

Deconfinement and quarkonium suppression

Modifications in the production pattern of heavy quark bound states have long been considered to provide sensitive signatures for the thermal properties of dense matter created in heavy ion collisions. The original concept of Matsui and Satz for quarkonium suppression as a signature for deconfinement in heavy ion collisions has been challenged recently through lattice studies of spectral functions, which indicate the persistence of heavy quark bound states at temperatures well above the transition, as well as through the refined analysis of hadronization and recombination models, which take into account the thermal evolution of the medium generated in a heavy ion collision. We will review here recent developments on these topics.Arrival of the final proofs: 25 March 2005PACS: 11.15.Ha, 11.10.Wx, 12.38.Mh, 25.75.NqF. Karsch: Present address: Physics Department, Brookhaven National Laboratory, Upton, NY 11973, USA     

Gluons in quarkonium decay

We discuss what can be learned from the ³S₁ quarkonium decay $\text{Q}\text{Q}\text{→ 3}\text{gluons}$, $\text{Q}\text{Q}\text{→ γ + 2}\text{gluons}$. The former is a way to find gluon jets and test QCD. The latter also allows us to measure gluon + gluon → hadrons, and look for pure gluonic resonances (glueballs).     

Color screening melts quarkonium

We calculate quarkonium spectral functions in a quark-gluon plasma using a potential model based on full QCD lattice calculations of the free energy of a static quark-antiquark pair. We estimate the binding energy and the thermal width of different quarkonium states. The estimated upper limit for the dissociation temperatures is considerably lower than the ones suggested in the recent literature.     

Search for supersymmetry at LHC

One of the main motivations for the experiments at the Large Hadron Collider (LHC), scheduled to start around 2006, is to search for supersymmetric particles. The region of the parameter space of the minimal supersymmetric standard model, where supersymmetry can be discovered, is investigated. We show that if supersymmetry exists at the electroweak scale, it would be easy to find signals for it at the LHC. If the LHC does find supersymmetry, this would be one of the greatest achievements in the history of theoretical physics.     

Color confining parton model for heavy quarkonium decay

We present a gluon jet model for the heavy quarkonium decay incorporating the color neutralization mechanism. Postulating that final hadrons are produced from the color singlet quark-antiquark pair originated each from different gluons, we formulate the production mechanism of hadrons from gluons explicitly. The fragmentation function thus obtained can describe the hadron production not only in the fragmentation region but also in the central one owing to the usage of the Sudakov variables. The result of the average charged multiplicity from Υ(9.46) is in reasonable agreement with the data, in contrast to the naive estimates. Furthermore, the inclusive momentum and multiplicity distributions are discussed.     

重夸克偶素的高阶变分-积分微扰修正

利用基于积分方程的改进的变分微扰方法(变分-积分微扰法)求解重夸克偶素激发态.设置含有变分参数的母哈密顿量作为零级哈密顿量,选择该母哈密顿系统的精确解作为试探波函数,得到了只有几项的高阶修正波函数和高阶能量修正.该计算结果更接近精确能量值,修正波函数的有界性和收敛性也得到了证明.结果表明,这种方法不仅可提高计算结果的精度,而且可确保微扰级数解的收敛性. 关键词： 重夸克偶素 变分-积分微扰法 高阶能量修正