Enhancement of heavy quarkonium production in hadron collisions at finite temperature

We estimate how the masses and wave functions of heavy quarkonium mesons change with temperature below the deconfining temperatureT _c . To do so we use simple, theoretically motivated parametrizations of the way the heavy quark potential and quark masses vary with temperature. The effect of these changes on the production of charmonium and bottonium in hadron-hadron collisions is estimated using a standard phenomenological model. We find, for example, that forT close toT _c enhancements by as much as a factor of 3 are possible for charmonium and bottonium highp _T production at SPS energies \(\sqrt s\) =20 GeV. Thep _T and energy dependence of this enhancement is non-trivial. We discuss the relevance of our results for the interpretation of recentJ/ψ data from heavy ion collisions.     

Minimal and two-doublet Higgs production in heavy quarkonium decays

The decay of a heavy vector toponium state into a photon or Z boson and a Higgs particle is investigated in both the minimal standard model and in a two Higgs doublet model. The decay into a minimal model Higgs boson and a Z is found to be suppressed due to a cancellation of different contributions. However, in the two-doublet case the rates are shown to sometimes be enhanced making this mode an interesting complement to the Wilczek process of the vector particle decaying into a photon and a Higgs boson. It is argued that the combined measurement of these processes would give valuable information on the structure of the Higgs sector of the electroweak interactions. In particular, two-doublet models with restrictions given by supersymmetry are shown to imply a specific pattern for these decays. If there would be a fourth generation, the quarkonium system built from the new b-like quark could decay quite frequently to a Higgs and a Z boson.     

Proof of perturbative gauge invariance for tree diagrams to all orders

It is proved that classical BRS‐invariance of the Lagrangian implies perturbative gauge invariance for tree diagrams to all orders. The proof applies in particular to the Einstein Hilbert Lagrangian of gravity.     

Proof of confinement of static quarks in 3-dimensionalU(1) lattice gauge theory for all values of the coupling constant

We study the 3-dimensional pureU(1) lattice gauge theory with Villain action which is related to the 3-dimensional -ferromagnet by an exact duality transformation (and also to a Coulomb system). We show that its string tension is nonzero for all values of the coupling constantg ², and obeys a bound const·m _D^–1 for smallag ², with =4²/g ² and . A continuum limita0,m _D fixed, exists and represents a scalar free field theory of massm _D. The string tension m _D ^–2 in physical units tends to in this limit. Characteristic differences in the behaviour of the model for large and small coupling constantag ² are found. Renormalization group aspects are discussed.Work supported in part by Deutsche Forschungsgemeinschaft     

Fragmentation of heavy quarks in polarized quarkonium in the effective heavy quark theory

Fragmentation of abantiquark into polarized B_c ^* mesons has been studied within the framework of the effective theory of heavy quarks. The functions ofb fragmentation into longitudinally polarized and transversely polarizedb S-wave states have been calculated with precise account for corrections of the first order in 1/m_b. The results are shown to agree with the corresponding calculations in quantum chromodynamics. Samara State University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, p. 97–104, July, 1996.     

Dipion decays of heavy quarkonium in the field correlator method

The mechanism of dipion transitions nS → n′Sππ (n = 3, 2; n′ = 2, 1) in bottomonium and charmonium is studied with the use of the chiral string-breaking Lagrangian allowing for the emission of any number of π(K, ν), and not containing fitting parameters. The transition amplitude contains two terms: M = a − b, where the first term (a) refers to subsequent one-pion emission, , and the second term (b) refers to two-pion emission, . The one parameter formula for the dipion mass distribution is derived, dw/dq∼ (phase space) × | η − x|², where x = (q ² − 4m _π²)/(q _max² − 4m _π²), q ² m= M _ππ². The parameter ν dependent on the process is calculated, using SHO wave functions and imposing PCAC restrictions (Adler zero) on amplitudes a and b. The resulting dipion mass distributions are in agreement with experimental data. The text was submitted by the authors in English.     

A comment on the potential in heavy quarkonium quantum-mechanical systems

I discuss the characteristics of the non-relativistic potential responsible for the ψ and ? systems. In particular a comparison is made between the recently advocated flavour independent power behaved potential and the QCD inspired Coulomb + linear potential. The ratios $\text{ΔM}{}_{\mathrm{?}}\text{ΔM}{}_{\mathrm{\psi }}$ of radical excitation energy level differences are used as sensitive tests to the r dependence of V(r). Deviations of these ratios from a constant value may indicate a gradual increase in the effective power of the potentials as r increases (in agreement with the Coulomb + linear potential). Decisive tests have to come from the not yet discovered toponium family where the ratios $\text{ΔM}{}_{\mathrm{T}}\text{ΔM?}$ should start to become greater than 1 if a singularity of the potential exists at r → 0.     

Analysis of the QCD sum rules for the heavy quarkonium

We study phenomenologically the QCD sum rules given by Shifman et al. for the heavy quarkonium. In the charmonium sum rules, we find that the contribution of the physical continuum to the moment ?_n is consistent with that of the effective one. As for the bottonium, the sum rules corrected by the Coulomb-like interaction are saturated very well by the four resonances observed at CESR. It is predicted that the³S₁ ground state of the toponium must exist in the range of \(M_{t\bar t} \) =30–44GeV, if the sum rules for the top quark are assumed.     

Proof of factorization of fragmentation function in non-equilibrium QCD

In this paper, we prove factorization of fragmentation function in non-equilibrium QCD by using Schwinger-Keldysh closed-time path integral formalism. We use the background field method of QCD in a pure gauge in path integral approach to prove factorization of fragmentation function in non-equilibrium QCD. Our proof is valid in any arbitrary gauge fixing parameter α. This may be relevant to study hadron production from quark-gluon plasma at high energy heavy-ion colliders at RHIC and LHC.     

Heavy quarkonium production in the regge limit of quantum chromodynamics

Heavy quarkonium \((c\bar c,b\bar b)\) hadronic production at Tevatron (run I and run II) and LHC energies is considered in the framework of nonrelativistic quantum chromodynamics in the leading order with respect to α _s and v using the quasi-multi-Regge kinematics approach. Fitting of p _T spectra of different S and P wave heavy quarkonium states at Tevatron (run I and run II) energies is carried out. The obtained set of octet nonperturbative matrix elements is used for prediction of heavy quarkonium production at LHC energies. The results obtained in the framework of quasi-multi-Regge kinematics are compared with predictions of the collinear parton model.