arXiv subjects

V. V. Anisovich

Publications and source records attributed to V. V. Anisovich.

At least 73 records · Page 4Linked to original sources

arXiv2001

Radiative decays of basic scalar, vector and tensor mesons and the determination of the P-wave q\bar q multiplet

We perform simultaneous calculations of the radiative decays of scalar mesons f_0(980)-> γγ, a_0(980)-> γγ, vector meson ϕ(1020)-> γf_0(980), γa_0(980), γπ^0, γη, γη' and tensor mesons a_2(1320)-> γγ, f_2(1270)-> γγ, f_2(1525)-> γγassuming all these states to be dominantly the q\bar q ones. A good description of the considered radiative decays is reached by using almost the same radial wave functions for scalar and tensor mesons that supports the idea for the f_0(980), a_0(980) and a_2(1320), f_2(1270), f_2(1525) to belong to the same P -wave q\bar q multiplet.

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arXiv2001

Quark-gluonium content of the scalar-isoscalar states f_0(980), f_0(1300), f_0(1500), f_0(1750), f_0(1420 ^{+150}_{- 70}) from hadronic decays

On the basis of the decay couplings f_0 -> ππ, K\bar K, ηη, ηη', which had been found before, in the study of analytical (IJ^{PC}=00^{++})-amplitude in the mass range 450-1900 MeV, we analyse the quark-gluonium content of resonances f_0(980), f_0(1300), f_0(1500), f_0(1750) and the broad state f_0(1420 ^{+ 150}_{-70}). The K-matrix technique used in the analysis makes it possible to evaluate the quark-gluonium content both for the states with switched-off decay channels (bare states, f^{bare}_0) and the real resonances. We observe significant change of the quark-gluonium composition in the evolution from bare states to real resonances, that is due to the mixing of states in the transitions f_0(m_1)-> real mesons-> f_0(m_2) responsible for the decay processes as well. For the f_0(980), the analysis confirmed the dominance of q\bar q component thus proving the n\bar n/s\bar s composition found in the study of the radiative decays. For the mesons f_0(1300), f_0(1500) and f_0(1750), the hadronic decays do not allow one to determine uniquely the n\bar n, s\bar s and gluonium components providing relative pecentage only. The analysis shows that the broad state f_0(1420 ^{+ 150}_{-70}) can mix with the flavour singlet q\bar q component only, that is consistent with gluonium origin of the broad resonance.

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arXiv2001

Quark structure of f0(980) from the radiative decays phi(1020)->gamma f0(980), gamma eta, gamma eta', gamma pi0 and f0(980)->gamma gamma

Partial widths of the radiative decays $ϕ(1020)\toγf_0(980)$, $γη$, $γη'$, $γπ^0$ and $f_0(980)\toγγ$ are calculated assuming all mesons under consideration to be $q\bar q$ states: $ϕ(1020)$ is dominantly an $s\bar s$ state ($n\bar n$ component $\lesssim 1%$), $η$, $η'$ and $π^0$ are standard $q\bar q$ states, $η= n\bar n\cosθ- s\bar s\sinθ$ and $η'=n\bar n\sinθ+ s\bar s\cosθ$ with $θ\simeq 37^\circ$, and $f_0(980)$ is the $q\bar q$ meson with the flavour wave function $n\bar n\cosϕ+ s\bar s \sinϕ$. Calculated partial widths for the decays $ϕ\toγη$, $γη'$, $γπ^0$ are in a reasonable agreement with experiment. The measured value of the branching ratio $BR(ϕ\toγf_0(980))$ requires $25^\circ\le |ϕ|\le 90^\circ$; for the decay $f_0(980)\toγγ$ the agreement with data is reached at either $77^\circ\leϕ\le 93^\circ$ or $(-54^\circ)\leϕ\le (-38^\circ)$. Simultaneous analysis of the decays $ϕ(1020)\toγf_0(980)$ and $f_0(980)\toγγ$ provides arguments in favour of the solution with negative mixing angle $ϕ=-48^\circ\pm 6^\circ$.

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arXiv2001

Determination of hadronic partial widths for scalar-isoscalar resonances f0(980), f0(1300), f0(1500), f_0(1750) and the broad state f0(1530^{+90}_{-250})

In the article of V.V. Anisovich et al., Yad. Fiz. 63, 1489 (2000), the K-matrix solutions for the wave IJ^{PC}=00^{++} were obtained in the mass region 450 - 1900 MeV where four resonances f0(980), f0(1300), f0(1500), f0(1750) and the broad state f0(1530^{+90}_{-250}) are located. Based on these solutions, we determine partial widths for scalar-isoscalar states decaying into the channels pi-pi, K-anti K, eta-eta, eta-eta', pi-pi-pi-pi and corresponding decay couplings.

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arXiv2000

Quark combinatorics and meson production ratios in hadronic Z^0 decays

Rich experimental data accumulated in the past few years in the hadronic $Z^0$ decays allow one to check the quark combinatorics relations for a new type of processes, namely: quark jets in the decays $Z^0 \to q\bar q \to hadrons$. In this paper we review quark combinatorics rules for the yields of vector and pseudoscalar mesons, $V/P$, in the central and fragmentation regions of the hadronic $Z^0$ decays. It is stressed that in the central region a direct verification of quark combinatorics rules is rather problematic because of a considerable background related to the decay of highly excited resonances; however such a verification is possible in the fragmentation region, at $x_{hadron} \sim 0.5-1$, where the contribution of resonance decays is suppressed due to the rapid decrease of spectra with increasing $x_{hadron}$. It is shown that the experimental data in the fragmentation region for $ρ^0/π^0$ and $p/π^+$ are in a reasonable agreement with the predictions of quark combinatorics. The ratios of the heavy meson yields, $B^*/B$ and $D^*/D$, are also discussed: the data demonstrate a good agreement with the quark combinatorial results. We analyse the structure of the suppression parameters for strange and heavy quark productions in soft processes and estimate their order of magnitudes in the multiperipheral processes; the ratio $K^{\pm}/π^{\pm}$ at $x_{hadron}\sim 0.5-0.8$ and production probabilities of the $c\bar c$ and $b \bar b$ mesons are in a good agreement with the estimates.

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arXiv2000

The light sigma meson

In the framework of the dispersion relation N/D-approach, we restore the low-energy pi-pi (IJ^{PC}=00^{++})-wave amplitude sewing it with the previously obtained K-matrix solution for the region 450-1900 MeV. The restored N/D-amplitude has a pole on the second sheet of the complex-s plane near the pi-pi threshold, that is the light sigma meson.

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arXiv2000

Systematics of q anti-q states in the (n,M^2) and (J,M^2) planes

In the mass region up to M < 2400 MeV we systematise mesons on the plots (n,M^2) and (J,M^2), thus setting their classification in terms of n^{2S+1}L_J q anti-q states. The trajectories on the (n,M^2)-plots are drawn for the following (IJ^{PC})-states: a_0(10^{++}), a_1(11^{++}), a_2(12^{++}), a_3(13^{++}), a_4(14^{++}), pi(10^{-+}), pi_2(12^{-+}), eta(00^{-+}), eta_2(02^{-+})$, rho(11^{--}), f_0(00^{++}), f_2(02^{++}). All trajectories are linear, with nearly the same slopes. At the (J,M^2)-plot we set out meson states for leading and daughter trajectories: for pi, rho, a_1, a_2 and P'.

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arXiv1999

The low-mass sigma-meson: Is it an eyewitness of confinement?

In the framework of the dispersion relation N/D-method we restore the low-energy pi-pi (IJ^{PC}=00^{++})-wave amplitude sewing it with the previously obtained K-matrix solution for the region 450--1900 MeV [V.V. Anisovich, Yu.D. Prokoshkin and A.V. Sarantsev, Phys. Lett. B389, 388 (1996)]. The restored N/D-amplitude has a pole on the second sheet of the complex-s plane, near the pi-pi threshold. We discuss the hypothesis that this low-mass pole, or the low-mass sigma-meson, corresponds to the dynamical state related to the confinement forces, that is the eyewitness of confinement.

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arXiv1999

Partial widths for the decays eta(1295) -> gamma gamma and eta(1440) -> gamma gamma

We discuss gamma gamma partial widths of pseudoscalar/isoscalar mesons eta(M) in the mass region M = 1000-1500 MeV. The transition amplitudes eta(1295) -> gamma gamma and eta(1440) -> gamma gamma are studied within an assumption that the decaying mesons are the members of the first radial excitation nonet 2^1S_0 q\bar q. The calculations show that partial widths being of the order of 0.1 keV are dominantly due to the n\bar n meson component while the contribution of the s\bar s component is small.

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arXiv1999

Reactions gamma gamma -> pi pi and gamma gamma -> K \bar K: the (IJ^{PC}=00^{++})-wave spectra at E_{gamma gamma}^{(c.m.)} = 300- 1900 MeV

We calculate the $00^{++}$-wave two-meson spectra for the reactions $γγ\toπ^0π^0$, $γγ\toπ^+π^-$, $γγ\to K^0\bar K^0$ and $γγ\to K^+ K^-$ on the basis of: (i) the results of the $K$-matrix analysis of the $00^{++}$ amplitudes for the reactions $ππ\to ππ$, $K\bar K$, $ηη$, $ηη'$, $ππππ$, and (ii) recently developed method for calculation of the decay amplitudes $f_0(1^3P_0q\bar q)\to γγ$, $f_0(2^3P_0q\bar q)\to γγ$. The reconstructed $ππ$ and $K\bar K$ spectra can be used as a guide for the extraction of partial widths of scalar/isoscalar resonances $f_0(980)\to γγ$, $f_0(1300)\to γγ$, $f_0(1500)\to γγ$, $f_0(1750)\to γγ$. As follows from our calculations, the resonances $f_0(980)$ and $f_0(1500)$ in the $π^+π^-$ and $π^0π^0$ spectra reveal themselves as dips.

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arXiv1999

Partial widths a_0(980)\toγγ, f_0(980)\toγγand q\bar q-classification of the lightest scalar mesons

We calculate partial widths for the decays a_0(980)\toγγand f_0(980)\toγγunder the assumption that a_0(980) and f_0(980) are members of the basic 1^3P_0 q\bar q nonet. The results are in a reasonable agreement with data thus giving an argument for a q\bar q origin of these mesons. We also calculate the γγpartial widths for the other scalar mesons, members of the 2^3P_0 q\bar q nonet.

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arXiv1999

Pomeron in diffractive processes $γ^(Q^2)p\toρ^0 p$ and $γ^(Q^2)p\toγ^*(Q^2) p$ at large Q^2: the onset of pQCD

We study the reactions $γ^*(Q^2)p\toρ^0 p$ and $γ^*(Q^2)p\toγ^*(Q^2) p$ at large Q^2 and $W^2/Q^2$ and small momentum transfer, $κ^2_\perp$, to the nucleon where the pomeron exchange dominates. At large Q^2 the virtual photon selects a hard $q\bar q$ pair, thus selecting the hard pomeron component (the BFKL pomeron). The amplitudes for both transverse and longitudinal polarizations of the initial photon and outgoing $ρ$-meson (photon) are calculated in the framework of the BFKL pomeron exchange. Our calculations show that one cannot expect the early onset of the pure perturbative regime in the discussed diffractive processes: the small interquark distances, $ρ_{q\bar q} <0.2$ fm, start to dominate not earlier than at $Q^2 \simeq 100 GeV^2, W^2/Q^2 \simeq 10^7$ in $γ^*(Q^2)p\toρ^0 p$ and $Q^2 \simeq 50 GeV^2, W^2/Q^2 \simeq 10^6$ in $γ^*(Q^2)p\toγ^*(Q^2) p$.

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arXiv1998

Exotic mesons, locking states and their role in the formation of the confinement barrier

We discuss a mechanism by which a set of $q\bar q$-states mixes with an exotic one, so that the exotic state accumulates the widths of the overlapping $\bar qq$ resonances. The broad state created this way acts as a 'locking' state for the others. Using results of a previous analysis of the $(IJ^{PC}=00^{++})$-wave, we estimate the mean radius squared of the broad state $f_0 (1530^{+90}_{-250})$; it appears to be distinctly larger than the mean squared radii of the locked narrow states. This supports an idea about the constructive role of broad states in forming the confinement barrier.

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arXiv1997

The lightest scalar glueball

Recently performed investigations of meson spectra allow us to determine the resonance structure for the waves $IJ^{PC}=00^{++}$, $10^{++}$, $02^{++}$, $12^{++}$ = $IJ^P= 1/2 0^+$ in the mass region up to 1900 MeV, thus establishing the meson multiplets $1^3P_0q\bar q$ and $2^3P_0q\bar q$. Experimental data demonstrate that there are five scalar/isoscalar states in this mass region. Four of them are $q\bar q$ states, that is, members of the $1^3P_0q\bar q$ and $2^3P_0q\bar q$ nonets, while the fifth state is an extra one not accomodated by $q \bar q$ systematics; it has the properties of the lightest scalar glueball. Analysis of the $00^{++}$-wave performed within the framework of the dispersion relation technique allows us to reconstruct the mixing of a pure gluonium with neighbouring scalar $q \bar q$ states belonging to $1^3P_0q\bar q$ and $2^3P_0q\bar q$ nonets: three scalar mesons share the gluonium state between each other -- those are two comparatively narrow resonances $f_0(1300)$ and $f_0(1500)$ and a broad resonance $f_0(1530^{+90}_{-250})$. The broad state is a descendant of the gluonium, keeping about 40-50% of its component.

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arXiv1997

Broad resonances as locking states and the problem of confinement

We discuss the mechanism of broad state formation when one of several overlapping resonances accumulates the widths of others. This mechanism may be important in the mixing of quark states with exotic ones. The broad resonance acts as a locking state for other states which mix with it; we consider the role of the broad state in the formation of the confinement barrier.

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arXiv1997

The two-pion spectra for the reaction π^- p -> π^0π^0 n at 38 GeV/c pion momentum and combined analysis of the GAMS, Crystal Barrel and BNL data

We perform the K-matrix analysis of meson partial waves with IJ^{PC} =00^{++}, 10^{++}, 02^{++}, 12^{++} basing on GAMS data on π^-p -> π^0π^0 n, ηηn, ηη' n together with BNL data on π^-p -> K\bar K n and Crystal Barrel data on p\bar p (at rest) -> π^0π^0π^0, π^0ηη, π^0π^0η. The positions of the amplitude poles (physical resonances) are determined as well as the positions of the K-matrix poles (bare states) and the values of bare state couplings to two-meson channels. Nonet classification of the determined bare states is discussed.

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arXiv1997

η-η' -Glueball mixing from photon-meson transition form factors and decay ratio D_s --> ηl ν/ η' l ν

The background due to the direct diffractive dissociation of the photon into the $π^+π^-$-pair to the "elastic" diffractive $ρ^0$-meson production in electron-proton collisions is calculated. The amplitude for the background process $γp \to π^+ π^- p$ is proportional to the $π$-meson - proton cross section. Therefore, describing the HERA data, we can estimate $σ(πp)$ at energy $s_{πp}\sim (2 - 3) 10^{3} GeV^2$ that is considerably higher the existing data. At large $Q^2$ the interference between resonant and non-resonant $π^+ π^-$ production leads also to the more slow increase of the $σ^L/σ^T$ ratio with the mass of the $2π$ (i.e. $ρ^0$-meson) state.

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arXiv1997

Scalar glueball: analysis of the (IJ^{PC}=00^{++})-wave

Basing on the previously performed K-matrix analysis of experimental data, we investigate, in the framework of the propagator matrix (D-matrix) technique, the 1100-1900 MeV mass region, where overlapping resonances $f_0(1300)$, $f_0(1500)$, $f_0(1530^{+90}_{-250})$, and $f_0(1780)$ are located. Necessary elements of the D-matrix technique are developed. The D-matrix analysis confirms previous K-matrix results: in the region 900-1900 MeV five scalar/isoscalar states are located. Four of them are members of the two $q\bar q$-nonets, while one state is an extra for the $q\bar q$ systematics, being a good candidate for the lightest scalar glueball. The D-matrix analysis shows that this extra state, a candidate for the lightest scalar glueball, is dispersed, due to a mixing with $q\bar q$- states, over three resonances: $f_0(1300)$, $f_0(1500)$, and $f_0(1530^{+90}_{-250})$. The broad resonance $f_0(1530^+{90}_{-250})$ is a descendant of the lightest glueball carrying about 50% of the gluonium component, the rest of the gluonium is shared between $f_0(1300)$ and $f_0(1500)$.

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