Flux-tube Breaking Research Articles

How large is the contribution of excited mesons in coupled-channel effects?

We study the excited $B$ mesons' contributions to the coupled-channel effects under the framework of ${}^3P_0$ model for the bottomonium. Contrary to what has been widely accepted, the contributions of $P$ wave $B$ mesons are generally the largest and this result is independent of the potential parameters to some extent. We also push the calculation beyond $B(1P)$ and carefully analyze the contributions of $B(2S)$. A form factor is a key ingredient to suppress the contributions of $B(2S)$ for low lying bottomonia. However, this suppression mechanism is not efficient for highly excited bottomonia such as $\Upsilon(5S)$ and $\Upsilon(6S)$. We give explanations why this difficulty happens to ${}^3P_0$ model and suggest analyzing flux-tube breaking model for the full calculation of coupled-channel effects.

Jets, Bulk Matter, and their Interaction in Heavy Ion Collisions at the LHC

We discuss a theoretical scheme that accounts for bulk matter, jets, and the interaction between the two. The physical picture of our approach is the following: Initial hard scatterings result in mainly longitudinal flux tubes, with transversely moving pieces carrying the pt of the partons from hard scatterings. These flux tubes constitute eventually both bulk matter (which thermalizes, flows, and finally hadronizes) and jets, according to some criteria based on partonic energy loss. High energy flux tube segments will leave the fluid, providing jet hadrons via the usual Schwinger mechanism of flux-tube breaking caused by quark-antiquark production. But the jets may also be produced at the freeze-out surface. Here we assume that the quark-antiquark needed for the flux tube breaking is provided by the fluid, with properties (momentum, flavor) determined by the fluid rather than the Schwinger mechanism. Considering transverse fluid velocities up to 0.7c, and thermal parton momentum distributions, one may get a "push" of a couple of GeV to be added to the transverse momentum of the string segment. This will be a crucial effect for intermediate pt jet hadrons.

Separating jets from bulk matter in heavy ion collisions at the LHC

We discuss a theoretical scheme that accounts for bulk matter, jets, and the interaction between the two. The physical picture of our approach is the following: Initial hard scatterings result in mainly longitudinal flux tubes, with transversely moving pieces carrying the pt of the partons from hard scatterings. These flux tubes constitute eventually both bulk matter (which thermalizes, flows, and finally hadronizes) and jets, according to some criteria based on partonic energy loss. High energy flux tube segments will leave the fluid, providing jet hadrons via the usual Schwinger mechanism of flux-tube breaking caused by quark-antiquark production. But the jets may also be produced at the freeze-out surface. Here we assume that the quark-antiquark needed for the flux tube breaking is provided by the fluid, with properties (momentum, flavor) determined by the fluid rather than the Schwinger mechanism. Considering transverse fluid velocities up to 0.7c, and thermal parton momentum distributions, one may get a "push" of a couple of GeV to be added to the transverse momentum of the string segment. This will be a crucial effect for intermediate pt jet hadrons.

The Klebanov-Strassler model with massive dynamical flavors

We present a fully backreacted D3-D7 supergravity solution dual to the Klebanov-Strassler cascading gauge theory coupled to a large number of massive dynamical flavors in the Veneziano limit. The mass of the flavors can be larger or smaller than the dynamically generated scale. The solution is always regular at the origin of the radial coordinate and as such it can be suitably employed to explore the rich IR physics of the dual gauge theory. In this paper we focus on the static quark-antiquark potential, the screening of chromoelectric charges induced by the dynamical flavors, the flux tube breaking and the mass spectrum of the first mesonic excitations. Moreover, we discuss the occurrence of quantum phase transitions in the connected part of the static quark-antiquark potential. Depending on the ratio of certain parameters, like the flavor mass, with respect to some critical values, we find a discontinuous (first order) or smooth transition from a Coulomb-like to a linear phase. We evaluate the related critical exponents finding that they take classical mean-field values and argue that this is a universal feature of analogous first order transitions occurring in the static potential for planar gauge theories having a dual supergravity description.

The anomalous suppression of π2(1670) → b1(1235) π

We show that current experimental data indicate that the strong decay mode π 2 → b 1 π is anomalously small (more than 3 times smaller than all other decay modes of the π 2. This acts as a powerful discriminator for and against various decay models. Non-relativistic quark models with spin-1 pair creation, e.g. 3 P 0 (flux-tube breaking) and 3 S 1 and 3 D 1 (chromo-electric string-breaking) models, as well as lowest order one-boson (in this case π) emission models, can accommodate the experimental data because of a quark-spin selection rule. Models that violate the selection rule, e.g. higher order one-boson emisson decay mechanisms, as well as mixing with other Fock states and relativistic effects, may be constrained by the small π 2 → b 1 π decay.

Origin of the Okubo-Zweig-Iizuka rule in QCD

The Okubo-Zweig-Iizuka (OZI) rule is prominent in hadronic phenomena only because OZI violation is typically an order of magnitude smaller than expected from large ${N}_{c}$ arguments. With its standard ${}^{3}{P}_{0}$ pair creation operator for hadronic decays by flux tube breaking, the quark model respects the OZI rule at the tree level and exhibits the cancellations between OZI-violating meson loop diagrams required for this dramatic suppression. However, if the quark model explanation for these cancellations is correct, then OZI violation would be expected to be large in the nonet with the same quantum numbers as the pair creation operator: the ${0}^{++}$ mesons. Experiment is currently unable to identify these mesons, but we report here on a lattice QCD calculation which confirms that the OZI rule arises from QCD in the vector and axial vector mesons as observed, and finds a large violation of the rule in the scalar mesons as anticipated by the quark model. In view of this result, we make some remarks on possible connections between the ${}^{3}{P}_{0}$ pair creation model, scalar mesons, and the ${U}_{A}(1)$ anomaly responsible for the large OZI violation which drives the ${\ensuremath{\eta}}^{\ensuremath{'}}$ mass.

Positive parity nonstrange baryons beyond 2 GeV

Previous studies of nonstrange baryons are extended to resonances of mass beyond 2 GeV, belonging to the N = 4 band. The framework is a semi-relativistic constituent quark model. The quark-quark interaction contains a Coulomb plus linear confinement term and a short-range spin-spin term. It turns out that the string tension value of 1 GeV fm−1 fixed previously in the N ≤ 3 bands is compatible with the N = 4 band. It is shown that the three-body confinement potential plays an important role in describing the inner structure of the band. The decay widths are calculated in a flux-tube breaking mechanism and compared to data and other models.

Properties of the strange axial mesons in the relativized quark model.

We studied properties of the strange axial mesons in the relativized quark model. We calculated the $K_1$ decay constant in the quark model and showed how it can be used to extract the $K_1 (^3P_1) - K_1 (^1P_1)$ mixing angle ($\theta_K$) from the weak decay $\tau \to K_1 \nu_\tau$. The ratio $BR(\tau \to \nu_\tau K_1 (1270))/BR(\tau\to \nu_\tau K_1(1400))$ is the most sensitive measurement and also the most reliable since the largest of the theoretical uncertainties factor out. However the current bounds extracted from the TPC/Two-Gamma collaboration measurements are rather weak: we typically obtain $-30^o \lesssim \theta_K \lesssim 50^o$ at 68\% C.L. We also calculated the strong OZI-allowed decays in the pseudoscalar emission model and the flux-tube breaking model and extracted a $^3P_1 - ^1P_1$ mixing angle of $\theta_K \simeq 45^o$. Our analysis also indicates that the heavy quark limit does not give a good description of the strange mesons.

Excited charmonium decays by flux-tube breaking and the ψ′ anomaly at CDF

The hadronic decay of radially and orbitally excited charmonium above charm threshold by 3 P 0 pair creation and chromoelectric flux-tube breaking is discussed in an harmonic oscillator approximation. We find independent evidence from a study of widths for a 2S admixture in the predominantly 1D state ψ(3770), and explore the possibility of metastable radially excited 2 3 P 0,1,2 states being a source of the anomalously large production of ψ′ at the Tevatron. At least one of them is expected to be narrow as a consequence of the existence of nodes in the radial wave function.

The production and decay of hybrid mesons by flux-tube breaking

An analytic calculation of the breaking of excited chromoelectric flux tubes is performed in an harmonic oscillator approximation and applied to predict the dynamics of all J PC low-lying gluonic excitations of mesons (hybrids). Widths, branching ratios and production dynamics of some recently discovered J PC = 1 −+,0 −+ and 1 −− mesons are found to be in remarkable agreement with these results. We introduce the selection rules that can be used to understand the systematics of numerical decay calculations and we find possible significant breaking of these rules for specific channels that may enable enhanced production and detection of hybrids.

Topological charge density around static colour sources in lattice QCD with dynamical quarks

We update our numerical investigation of topological structures around static quarks in pure gauge QCD by results of the first runs including dynamical quarks. Simulations were performed on an $8^3\times4$ lattice, with $SU(3)$ Wilson action, with 3 flavours of quarks of equal mass, both in the confinement and deconfinement phase. In the confinement phase we observe indications for the existence of a flux tube between a static quark and antiquark, flux-tube breaking for large separations, and local correlation between the topological charge density and chiral condensate. In the deconfinement phase almost all configurations turn out to be topologically trivial.

Flux tube profiles with dynamical quarks and finite temperatures

We analyze gluon string distributions in a static meson with dynamical quarks in the confinement and deconfinement regimes. We demonstrate flux tube breaking when sea quarks are considered or the temperature is increased beyond the deconfinement phase transition. The dependence of the string width on the meson elongation is explored for various QCD vacua. It turns out that the energy density is restricted to a thin flux tube of constant diameter in the confinement phase and takes dipole-like behavior across the deconfinement transition.

A study of the flux tube model

Abstract The process that a flux tube breaks into two flux tubes or into three flux tubes is studied by calculating the classical action and the fluctuation action. For the process, the minimal action determined by the classical and the fluctuation action implies that a simultaneous breaking into three flux tubes is suppressed. This provides a possible explanation of the quasi-two-body dominance in the N N annihilation. A comparison of our result for the flux tube breaking strength and that estimated phenomenologically indicates that an incorporation of dynamics of quarks in the model is indispensable.

Formula omitted]p annihilation into mesons in the 3P 0 model with a planar quark-diagram topology, and in the flux-tube model

The foundation of the 3P 0 model with a planar quark-diagram topology, which is called the A2 model and the A3 model, in the p p annihilation into two mesons and into three mesons, respectively, are studied in the flux-tube model. The flux-tube model is based on the strong coupling lattice QCD theory, and we calculate the amplitudes of a flux-tube breaking into two flux tubes and into three flux tubes numerically and compare with their continuum limits which can be calculated analytically. The strength of the flux-tube breaking is compared with the empirical strength of the 3P 0 model.

Meson-meson scattering in the flux tube model

Meson-meson scattering is described in terms of the rearrangement of colour-electric flux tubes. This reduces the problem to a knowledge of the flux-tube breaking amplitude for meson decay. Various forms of this basic amplitude are considered. However, in most cases the effect of the rearrangement mechanism appears to be small, with the resultant meson-meson potentials giving phase shifts of only a few degrees.

The flux tube and the flux tube breaking amplitude in the harmonic approximation

In the flux tube model the amplitude for meson hadronic decay A to B+C is given by an overlap integral containing a factor gamma bca which represents the amplitude that the initial flux tube a should break at a specific point, forming the two flux tubes b and c of the final two mesons. The authors estimate the factor gamma bca in a harmonic approximation for the decays of both ordinary quark model mesons (a=flux tube ground state) and the lowest vibrational hybrids (a=first excited state of flux tube). They also discuss the relationship of the flux tube model to the leading term in the evaluation of the Wilson loop expectation value.

Meson decays by flux-tube breaking.

We have examined meson decays in a model with chromoelectric flux-tube breaking motivated by the strong-coupling limit of QCD. Our analysis includes all of the simple decay modes of mesons with up to two units of orbital or one unit of radial excitation, as well as a number of other interesting modes and higher-mass resonances. In conjunction with the wave functions of a relativized version of the quark model, our calculations provide, in terms of a single elementary flux-tube-breaking amplitude, predictions for meson decay amplitudes which are in excellent correspondence to experiment. The model also (1) leads to an understanding of the relevance and success of the $^{3}\mathrm{P}_{0}$ model, (2) provides predictions for channels in which it should be possible to see many of the missing low-lying mesons of the quark model, (3) points toward solutions to some puzzles in meson phenomenology, and (4) promises to be a useful tool for understanding the properties of unconventional mesons, especially meson hybrids.