Diffractive neutrino production of vector mesons

Using the diffractive vector dominance, we predict an event rate for charged vector mesons which is within the experimental bounds measured at Fermilab. Due to the very limited statistics no firm conclusion can be drawn on the structure of the neutral current. Similar estimations have been done for the Gargamelle experiment.     

Diffractive production of vector mesons in lepton-nucleon reactions

We calculate cross sections for the production of vector mesons V in reactions if ? + N → ?' + V + N, ?, ?' = ν, e, μ, taking into account all presently known information from electroproduction of ?'s. This leads to considerable differences in results from previous calculations, often more than an order of magnitude. The results for the ? are then largely a translation of electroproduction data into ν predictions and they will provide a direct test of the relation of weak and electromagnetic currents. The y or Q² distributions for the ? are instructive. The prediction for the A₁ provides a direct test of the existence of the A₁ and of whether vector and axial vector currents materialize into particles in the same way. The detection of a B meson would provide direct evidence for second-class currents and a measurement of their strength. We estimate all F¹ production will account for at most 2% of the total ν cross section at FNAL energies, which must be multiplied by the muon semi-leptonic branching ratio (and possibly a factor of 2 for an axial vector F¹) to calculate its contribution to the dimuon event rate.     

Diffractive large transferred momentum photoproduction of vector mesons

The large t behavior of the helicity amplitudes of diffractive photoproduction is estimated relying on models of the photon and meson light-cone wave functions and on the double-logarithmic approximation to the exchanged gluon interaction. The role of large-size color dipole contributions to the photon-meson transition impact factor is discussed.Received: 17 November 2003, Revised: 10 March 2004, Published online: 23 June 2004A. Ivanov: Corresponding author.     

Diffractive vector mesons beyond the s-channel helicity conservation

We derive a full set, and determine the twist, of helicity amplitudes for diffractive production of light to heavy vector mesons in deep inelastic scattering. For large Q ² all helicity amplitudes but the double-flip are calculable in perturbative QCD and are proportional to the gluon structure function of the proton at a similar hardness scale. We find a substantial breaking of the s-channel helicity conservation, which must persist in real photoproduction also. Pis’ma Zh. éksp. Teor. Fiz. 68, No. 9, 667–673 (10 November 1998) Published in English in the original Russian journal. Edited by Steve Torstveit.     

Diffractive S and D wave vector mesons in deep inelastic scattering

Helicity amplitudes for diffractive leptoproduction of the S and D wave states of vector mesons are derived. A dramatically different spin dependence for production of the S and D wave vector mesons is predicted. It is found that R=σ_L/σ_T is very small and that the higher twist effects in the production of longitudinally polarized D wave vector mesons are abnormally large. Pis’ma Zh. éksp. Teor. Fiz. 69, No. 4, 268–273 (25 February 1998) Published in English in the original Russian journal. Edited by Steve Torstveit.     

Diffractive production of charmed strange mesons by neutrinos and antineutrinos

The diffractive production of charmed strangeD _s ^* and possiblyD _s mesons by neutrinos and antineutrinos on nucleons in hydrogen, deuterium and neon targets is observed. The slope parameter of thet distribution is 3.3±0.8 (GeV)^?2. The production rate per charged current neutrino interaction with an isoscalar target times the D _s ⁺ →φτ⁺ branching fraction is (1.03±0.27)×10^?4.     

Diffractive vector meson production at large momentum transfer

The diffractive process γp→V+X (whereV is a vector meson andX results from the dissociation of the proton) is studied. In particular, we consider the region of large momentum transfer (i.e. |t| ?Λ _QCD ² ) and large centre-of-mass (CM) energy,s. The asymptotic (s→∞,s/|t|?1) behaviour is derived from the BFKL equation and compared to that which is obtained in the Born approximation (two-gluon exchange). We also calculate the corrections to the Born graphs by iterating the BFKL kernel numerically. Improved convergence of the BFKL series is found by summing the logarithms which occur when an exchanged gluon goes nearly on shell. Importantly, we find evidence that the asymptotic solution to the BFKL equation is inappropriate over most of the HERA range and we provide more realistic predictions for the cross section. The predicted cross section is not too small and can be measured at HERA, up to momentum transfers |t|≈10 GeV².     

Diffractive heavy vector meson production from the BFKL equation

Diffractive heavy vector meson photoproduction accompanied by proton dissociation is studied for arbitrary momentum transfer. The process is described by the non-forward BFKL equation, for which a complete analytical solution is found, giving the scattering amplitude. The impact of non-leading corrections to the BFKL equation is also analysed. Results are compared to the HERA data on production. Received: 2 July 2002 / Revised version: 29 August 2002 / Published online: 18 October 2002     

Inclusive production of neutral vector mesons in hadronic Z decays

A data sample of about 3.0 million hadronicZ decays collected by the ALEPH experiment at LEP in the years 1991 through 1994 is used to make an inclusive selection of B hadron events. In this event sample 4227±140±252B* mesons in the decayB*→Bγ and 1944±108±161B** _u,d mesons decaying into a B meson and a charged pion are reconstructed. Here and in the followingB** _u,d denotes the eightL=1(bū) and (bd) states and their charge conjugate. For the well establishedB* meson the following quantities are obtained:ΔM=M _B*−M_B=(45.30±0.35±0.87) MeV/c² andN _B*/(N _B+N _B*)=(77.1±2.6±7.0)%. The angular distribution of the photons in theB* rest frame is used to measure the relative contribution of longitudinalB* polarization states to beσ _L/(σ _L+σ _T)=(33±6±5)%.     

Light vector mesons

This article reviews the current status of experimental results obtained in the measurement of light vector mesons produced in proton-proton and heavy ion collisions at different energies. The review is focused on two phenomena related to the light vector mesons; the modification of the spectral shape in search of chiral symmetry restoration and suppression of the meson production in heavy ion collisions. The experimental results show that the spectral shape of light vector mesons are modified compared to the parameters measured in vacuum. The nature and the magnitude of the modification depends on the energy density of the media in which they are produced. The suppression patterns of light vector mesons are different from the measurements of other mesons and baryons. The mechanisms responsible for the suppression of the mesons are not yet understood. Systematic comparison of existing experimental results points to the missing data which may help to resolve the problem.     

Electrodynamics of charged vector mesons

Questions of the correctness of the motion equations are considered in Stückelberg and Borgardt's theory in the presence of anomalous magnetic and electric quadrupole moments for the vector meson. The coherence of the quantization scheme with indefinite metric developed leads to invariantness of the Lagrangian for the operation of metric conjugation, which in turn causes transitions between states with spin 1 and spin 0 to be forbidden. The vector meson pair formation section is calculated for photons in a nuclear field.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, pp 101–106, May, 1978.     

Masses of colored vector mesons

Mass formulas for colored vector mesons are derived under the assumption of one common mixing angle forSU(3)′, independent of the color quantum numbers, and correspondingly one common mixing angle (?″) forSU(3)″. This a priori plausible assumption turns out to have strong implications and thus might be too restrictive. We allow for a non-trivial spatial overlap integralρ between color-singlet and color-octet states. Various cases are treated and physical possibilities are identified. The best agreement is obtained for ?″ = 0. There are two models of this type with and without a part of the symmetry breaking Hamiltonian density transforming as (Y, Y) underSU(3)′?SU(3)″. Models with ?″ ≠ 0 are also possible. They cannot have a (Y, Y) and predict 3.34 GeV as the mass of theψ′ (3.7). This error of 10% may however be used to reject this possibility. Masses of colored vector mesons are predicted in the various models. If a (Y, Y) is present, ideal mixing inSU (3)′ is implied by the general formalism of the model.