Coupling of `t Hooft's determinant term is investigated in the framework of the three flavor linear sigma model as a function of the chiral condensate. Using perturbation theory around the minimum point of the effective action, we calculate the renormalization group flow of the first field dependent correction to the coupling of the conventional U_A(1) breaking determinant term. It is found that at low temperatures mesonic fluctuations make the anomaly increase when the chiral condensate decreases. As an application, we analyze the effect at the zero temperature nuclear liquid-gas transition.
We present an analysis of the three-flavor holographic model of QCD associated to a $D4/D8$ brane configuration, with symmetry breaking induced by a worldsheet instanton associated to a closed loop connecting $D4-D8-D6-\overline{D8}$. We calculate the electromagnetic and axial couplings of all octet and decuplet baryons, as well as several negative parity excitations, with and without symmetry breaking effects, and demonstrate qualitative and quantitative agreement with many available experimental measurements, with marked improvement over the analogous two-flavor models.
We discuss an Nf=3 linear sigma model with vector and axial-vector mesons (extended Linear Sigma Model - eLSM). We present first results regarding the masses of axial-vector mesons determined from the extended model.
The $SU(2)_A \times U(2)_V$-symmetric chiral linear sigma model in the presence of the axial anomaly is studied in the local-potential approximation of the Functional Renormalization Group (FRG). The renormalization group (RG) flow is investigated in a truncation which reproduces recent results for the $U(2)_A \times U(2)_V$-symmetric model in the limit of vanishing axial anomaly strength. We search for the conjectured O(4) fixed point in the presence of the $U(1)_A$ anomaly and analyze its stability properties.
We consider vector and axialvector mesons in the framework of a gauged linear sigma model with chiral $U(N_f)_R \times U(N_f)_L$ symmetry. For $N_f=2$, we investigate the behavior of the chiral condensate and the meson masses as a function of temperature by solving a system of coupled Dyson-Schwinger equations derived via the 2PI formalism in double-bubble approximation. We find that the inclusion of vector and axialvector mesons tends to sharpen the chiral transition. Within our approximation scheme, the mass of the $ρ$ meson increases by about 100 MeV towards the chiral transition.
We address the question whether it is possible to interpret the low-lying scalar mesons f0(600) and a0(980) as \bar q - q states within a U(3)xU(3) Linear Sigma Model containing vector and axial-vector degrees of freedom.
We discuss the phenomenology of the axial-vector mesons within a three-flavour Linear Sigma Model containing scalar, pseudoscalar, vector and axial-vector degrees of freedom.
Zero temperature properties of an (axial-) vector meson extended linear sigma model are discussed, concerning on the possible different realizations of the axial anomaly term. The different anomaly terms are compared with each other on the basis of a chi^2 minimalization process. It is found that there is no essential difference among the different realizations. This means that any of them can be equally used from phenomenological point of view.
In this article, we study the light-flavor scalar and axial-vector diquark states in the vacuum and in the nuclear matter using the QCD sum rules in an systematic way, and make reasonable predictions for their masses in the vacuum and in the nuclear matter.
In chiral models with SU(3) group structure, strange form factors of baryon octet are evaluated by constructing their sum rules to yield theoretical predictions comparable to the recent experimental data of SAMPLE Collaboration. We also study sum rules for the flavor singlet axial currents for the EMC experiment in a modified quark model.
We calculate the light quark condensate, the strange quark condensate, the pion condensate, and the axial condensate in three-flavor chiral perturbation theory ($χ$PT) in the presence of an isospin chemical potential at next-to-leading order at zero temperature. It is shown that the three-flavor $χ$PT effective potential and condensates can be mapped onto two-flavor $χ$PT ones by integrating out mesons with strange quark content (kaons and eta), with renormalized couplings. We compare the results for the light quark and pion condensates at finite pseudoscalar source with ($2+1$)-flavor lattice…
The interplay of mesonic fluctuations with an axial $U(1)_A$-symmetry breaking and resulting effects on the location of a possibly existing critical endpoint in the QCD phase diagram are investigated in a framework of the functional renormalization group within a $N_f = 2 + 1$ flavor quark-meson model truncation. The axial $U(1)_A$-symmetry breaking is imposed by a mesonic Kobayashi-Maskawa-'t Hooft determinant. The quark mass sensitivity of the chiral phase transition with and without the $U(1)_A$-symmetry breaking is studied.
The renormalization constant $Z_J$ of the flavor-singlet axial-vector current with a non-anticommuting $γ_5$ in dimensional regularization is determined to order $α_s^3$ in QCD with massless quarks. The result is obtained by computing the matrix elements of the operators appearing in the axial-anomaly equation $\big[\partial_μ J^μ_{5} \big]_{R} = \frac{α_s}{4 π}\, n_f\, {\displaystyle \mathrm{T}_{F}} \, \big[F \tilde{F} \big]_{R}$ between the vacuum and a state of two (off-shell) gluons to 4-loop order. Furthermore, through this computation, the conjectured equality between the $\overline{\mat…
We construct the electromagnetic anomaly effective term for a generalized linear sigma model with two chiral nonets, one with a quark-antiquark structure, the other one with a four quark content. We compute in the leading order of this framework the decays into two photons of six pseudoscalars: $π_0(137)$, $π_0(1300)$, $η(547)$, $η(958)$, $η(1295)$ and $η(1760)$. Our results agree well with the available experimental data.
We outline the extension of the globally chirally invariant Nf = 2 linear sigma model with vector and axial-vector degrees of freedom to Nf=3. We present preliminary results concerning the scalar meson masses.
The role of the axial anomaly in the chiral phase transition at finite temperature and quark chemical potential is investigated within a non-perturbative functional renormalization group approach. The flow equation for the grand potential is solved to leading-order in a derivative expansion of a three flavor quark-meson model truncation. The results are compared with a standard and an extended mean-field analysis, which facilitates the exploration of the influence of bosonic and fermionic fluctuations, respectively, on the phase transition. The influence of U(1)_A-symmetry breaking on the chir…
The extended linear sigma model describes the vacuum phenomenology of scalar, pseudoscalar, vector and axial-vector mesons at energies \(\simeq 1\text{ GeV}\). We combine the chiral \(U(2)_L\times U(2)_R\) symmetry of this model with a local \(SU(2)_L\times U(1)_Y\) symmetry and obtain a gauge invariant effective description for electroweak interaction of hadrons in the vacuum. Vector and axial-vector spectral functions can be described well by two intermediate resonances \(ρ\) and \(a_1\). They are implemented into this model as chiral partners and yield the predominant contributions to both …
The renormalization constant $Z_J$ of the flavor-singlet axial-vector current with a non-anticommuting $γ_5$ in dimensional regularization is determined to order $α_s^3$ in QCD with massless quarks. In addition, the equality between the $\overline{\mathrm{MS}}$ renormalization constant $Z_{F\tilde{F}}$ associated with the operator $\big[F \tilde{F} \big]_{R}$ and that of $α_s$ is verified explicitly to hold true at 4-loop order.
We evaluate the strangeness-conserving $N N$, $ΣΣ$, $ΞΞ$, $ΛΣ$ and the strangeness-changing $ΛN$, $ΣN$, $ΛΞ$, $ΣΞ$ axial charges in lattice QCD with two flavors of dynamical quarks and extend our previous work on pseudoscalar-meson-octet-baryon coupling constants so as to include $πΞΞ$, $KΛΞ$ and $KΣΞ$ coupling constants. We find that the axial charges have rather weak quark-mass dependence and the breaking in SU(3)-flavor symmetry is small at each quark-mass point we consider.
The axial-vector form factors and axial-vector constants of the baryon decuplet are investigated within a pion mean-field approach, which is also known as the chiral quark-soliton model. Given an axial-vector current with a specified flavor, there are four different form factors of a decuplet baryon. When we consider the singlet, triplet, and octet axial-vector currents, we have twelve different form factors for each member of the baryon decuplet. We compute all these axial-vector form factors of the baryon decuplet, taking into account the rotational $1/N_c$ corrections and effects of flavor …
With twisted boundary conditions on the quark fields, we study nucleon matrix elements of the axial current utilizing twisted heavy baryon chiral perturbation theory. One can explore the momentum transfer dependence of the axial form factors more easily than by using ordinary lattice quantized momenta alone. As examples, we derive expressions for the nucleon axial radius and pseudoscalar form factor.
The implications of Chiral Quark Model with SU(3) and axial U(1) symmetry breakings as well as configuration mixing generated by one gluon exchange forces ($χ$QM$_{gcm}$) are discussed in context of proton flavor and spin structure as well as hyperon $β$-decay data. Apart from reproducing the success of $χ$QM with symmetry breaking, it is able to improve upon the agreement with data in several cases such as, $G_A/G_V, Δ_8, <A_1^p>$ dependent on spin polarization functions and ($\frac{2 \bar s}{u+d}$), ($\frac{2 \bar s}{\bar u+\bar d}$) and f_s involving the quark distribution functions.
The phase diagram of strongly interacting matter is studied within a three-flavor Nambu--Jona-Lasinio model, which contains the coupling between chiral and diquark condensates through the axial anomaly. Our results show that it is essential to include the 2SC phase in the analysis. While this is expected for realistic strange quark masses, we find that even for equal up, down, and strange bare quark masses, 2SC pairing can be favored due to spontaneous flavor-symmetry breaking by the axial anomaly. This can lead to a rich phase structure, including BCS- and BEC-like 2SC and CFL phases and new …
We study scalar, pseudoscalar, vector, and axial-vector mesons with non-strange and strange quantum numbers in the framework of a linear sigma model with global chiral $U(N_f)_L \times U(N_f)_R$ symmetry. We perform a global fit of meson masses, decay widths, as well as decay amplitudes. The quality of the fit is, for a hadronic model that does not consider isospin-breaking effects, surprisingly good. We also investigate the question whether the scalar $\bar{q}q$ states lie below or above 1 GeV and find the scalar states above 1 GeV to be preferred as $\bar{q}q$ states. Additionally, we also d…
Using the axial-vector coupling and the electromagnetic form factors of the D and D* mesons in 2+1 flavor Lattice QCD, we compute the D*Dπ, DDρand D*D*ρcoupling constants, which play an important role in describing the charm hadron interactions in terms of meson-exchange models. We also extract the charge radii of D and D* mesons and determine the contributions of the light and charm quarks separately.
Nonlinear sigma model (NLSM) based on the coset $\text{SU}(N)\times \text{SU}(N)/\text{SU}(N)$ exhibits several intriguing features at the leading ${\cal O}(p^2)$ in the derivative expansion, such as the flavor-kinematics duality and an extended theory controlling the single and triple soft limits. In both cases the cubic biadjoint scalar theory plays a prominent role. We extend these features in two directions. First we uncover a new extended theory for $\text{SO}(N+1)/\text{SO}(N)$ NLSM at ${\cal O}(p^2)$, which is a cubic bifundamental/biadjoint scalar theory. Next we provide evidence for f…
The chiral quark model with a nonet of Goldstone bosons can yield an adequate description of the observed proton flavor and spin structure. In a previous publication we have compared the results of a SU(3) symmetric calculation with the phenomenological findings based on experimental measurements and SU(3) symmetry relations. In this paper we discuss their SU(3) and axial-U(1) breaking corrections. With two parameters, we obtain a very satisfactory fit to the F/D ratios for the octet baryon masses and for their axial vector couplings, as well as the different quark flavor contributions to the …
The in-medium behavior of ground-state $q\bar{q}$ mesons, where $q \in \{u,d,s,c\}$, in vector and axial-vector channels is studied based on the spectral analysis for mesonic correlators at finite temperature and zero chemical potential. We first compute the correlators by solving the quark gap equations and the inhomogeneous Bethe-Salpeter equations in the rainbow-ladder approximation. Using a phenomenological ansatz, the spectral functions are extracted by fitting the correlators. By analyzing the evolution of the spectral functions with the temperature, we obtain the dissociation temperatur…
Features of the non-strange \bar n-n and strange \bar s-s scalar mesons are investigated in the Extended Linear Sigma Model (eLSM) with Nf=3 and vector and axial-vector mesons. Our model contains a pure non-strange and a pure strange scalar state; implementing the mixing of the two states originates two new states, a predominantly non-strange and a predominantly strange one. We investigate the possibility to assign the two mixed states to experimentally well-established resonances. To this end, we calculate the masses and the two-pion decay widths of the mixed states and compare them with expe…
In this paper we explore the chiral phase transition in QCD within the three-flavor Nambu-Jona-Lasinio (NJL) model with a negative coupling constant in the isoscalar axial-vector channel, which is associated with a polarized instanton--anti-instanton molecule background. The QCD phase diagram described in this scenario shows a new first order phase transition around the transition temperature $T_c$ toward a phase without chiral condensates, but with nontrivial dynamic chiral chemical potentials for the light quarks, spontaneously giving rise to local $\mathcal {CP}$ violation and local chirali…
The structure of the scalar mesons has been a subject of debate for many decades. In this work we look for $\bar{q}q$ states among the physical resonances using an extended Linear Sigma Model that contains scalar, pseudoscalar, vector, and axial-vector mesons both in the non-strange and strange sectors. We perform global fits of meson masses, decay widths and amplitudes in order to ascertain whether the scalar $\bar{q}q$ states are below or above 1 GeV. We find the scalar states above 1 GeV to be preferred as $\bar{q}q$ states.
The baryon axial vector current is computed at one-loop order in large-N_c baryon chiral perturbation theory, where N_c is the number of colors. Loop graphs with octet and decuplet intermediate states are systematically incorporated into the analysis and the effects of the decuplet-octet mass difference and SU(3) flavor symmetry breaking are accounted for. As expected, large-N_c cancellations between different one-loop graphs are observed as a consequence of the large-N_c spin-flavor symmetry of QCD baryons. Fitting our analytical formulas against experimental data on baryon semileptonic decay…
Temperature dependence of the $U_A(1)$ anomaly is investigated by taking into account mesonic fluctuations in the $U(3)\times U(3)$ linear sigma model. A field dependent anomaly coefficient function of the effective potential is calculated within the finite temperature functional renormalization group approach. The applied approximation scheme is a generalization of the chiral invariant expansion technique developed in [G. Fejos, Phys. Rev. D 90, 096011 (2014)]. We provide an analytic expression and also numerical evidence that depending on the relationship between the two quartic couplings, m…
We study the QCD phase structure in the three-flavor Nambu-Jona-Lasinio model, incorporating the interplay between the chiral and diquark condensates induced by the axial anomaly. We demonstrate that for an appropriate range of parameters of the model, the interplay leads to the low temperature critical point in the phase structure predicted by a previous Ginzburg-Landau analysis. We also show that a Bose-Einstein condensate (BEC) of diquark molecules emerges in the intermediate density region, and as a result, a BEC-BCS crossover is realized with increasing quark chemical potential.
We investigate the phase structure of massless three-flavor QCD by extending the Nambu-Jona- Lasinio model to include the effects of confinement and the axial anomaly. We study the interplay between the chiral and diquark condensates induced by the axial anomaly, as well as their relationship with the Polyakov loop, which parameterizes confinement. By minimizing the thermodynamic potential we construct the QCD phase diagram and investigate the possibility of realizing a recently discovered low temperature critical point and an associated BEC-BCS crossover. We also perform a Ginzburg-Landau exp…
We take into account the sigma meson cloud effect in the meson cloud model to calculate the distributions of light flavor sea quarks in the proton. Our calculation gives a better description of the data for $\bar{d}(x)/\bar{u}(x)$. We also provide a picture that the probability of finding a physical proton in a Fock state $|Nω> $ is reasonable small with a smaller cutoff $Λ_ω$.
We have investigated the axial charges of the ground octet baryons within the extended chiral constituent quark model, where all the possible compact five-quark Fock components $qqq(q\bar{q}) (q=u, d, s)$ in the baryons are considered. The transition couplings between the three- and five-quark components in the baryons are assumed to be via the $^{3}P_{0}$ mechanism, which could reproduce the sea asymmetry in proton very well. The numerical results for the flavor-dependent axial charges of the octet baryons are comparable to those predicted by other theoretical approaches. It is shown that the…
The gluonic contributions to the conventional PCAC formulas due to flavor singlet axial anomaly have been instrumental in explaining the mass of the $η^{\prime}$ and providing a plausible explanation for solving the spin crisis. We show that they also play an important role in the description of photo- and electroproduction of vector mesons at low energy and high momentum transfers. We calculate the contributions of this type to $ϕ$ meson electromagnetic production in a model, which contains also a soft pomeron, and find agreement with recent CLAS data.
We derived the tree level spectrum to an extension to the linear sigma model describing an EFT for an $SU(3)_c$ gauge theory with $N_f$ flavors of fermions and $N_1$ fermions have a mass $m_l$ and $N_2$ fermions have a mass $m_h$. We examined the effects of a small mass splitting on single mass data for 8 and 12 flavors of fermions corresponding to the unperturbed case. Our intention is to encourage more simulations of split mass theories with 8, 10 and 12 flavors of fermions.
Branching ratios observed for $D$ and B decays to final states $a_1(1260)^{\pm} X$ are comparable to those for corresponding decays to $π^{\pm} X$ and $ρ^{\pm} X$ and much larger than those for all other decays. Implications are discussed of a "vector-dominance model" in which a $W$ is produced and immediately turns into an axial vector, vector or pseudoscalar meson. Data for decays to all such final states are shown to have large branching ratios and satisfy universality relations. Upper limits on small strong phase differences between amplitudes relevant to CP violation models are obtained f…
We extend the three-flavor linear sigma model with (axial-)vector mesons to four flavors. We compute the masses of (pseudo)scalar and (axial-)vector mesons including open and hidden charmed mesons as well as weak decay constants. The results are in good agreement with experimental data.
Quantum effects inside the chiral bag induce a color anomaly which requires a compensating surface term to prevent breakdown of color gauge invariance. We show that the presence of this surface term first discovered several years ago allows one to derive in a gauge-invariant way a chiral-bag version of the Shore-Veneziano two-component formula for the flavor-singlet axial charge of the proton. This has relevance to what is referred to as the ``proton spin problem" on the one hand and to the Cheshire-Cat phenomenon in hadron structure on the other. We show that when calculated to the leading or…
We present results for the $σ$-terms and axial charges for various hyperons and charmed baryons using $N_f=2+1+1$ twisted mass fermions. For the computation of the three-point function we use the fixed current method. For one of the $N_f=2+1+1$ ensembles with pion mass of 373 MeV we compare the results of the fixed current method with those obtained with a stochastic method for computing the all-to-all propagator involved in the evaluation of the three point functions.
We discuss electro-magnetic and weak axial N-Delta transition amplitudes in the linear sigma-model and the Cloudy-Bag Model as typical representatives of chiral quark models. We show that good qualitative understanding of the transition can be obtained in models which, in addition to the pion cloud, incorporate a fluctuating sigma-field inside the baryon.
We investigate the axial-vector transition form factors of the baryon octet to the baryon decuplet within the framework of the chiral quark-soliton model, with the effects of flavor SU(3) symmetry breaking included. We consider the rotational $1/N_c$ corrections and regard the strange current quark mass as a perturbation. We compare the present results for the $Δ\to N$ axial-vector transition with those from other models and lattice QCD. We also compute all possible axial-vector transitions from the baryon decuplet to the octet with the strangeness changed, i.e., $|ΔS|=1$. We obtain the value …
We investigate the twist-3 pion and kaon distribution amplitudes of the pseudoscalar (phi^p_{pi,K}) and pseudotensor (phi^{sigma}_{pi,K}) types, based on the effective chiral action from the instanton vacuum. Effects of flavor SU(3) symmetry breaking are explicitly taken into account. The Gegenbauer moments and the moments of the distribution amplitudes (<xi^m>) are also computed. Our results are summarized as follows: a^p_{2,pi} ~ 0.4, a^p_{1,K} ~ 0.02 and a^p_{2,K} ~ 0.14, and a^{sigma}_{2,pi} ~ 0.02 and a^{sigma}_{1,K} ~ a^{sigma}_{2,K} ~ 0; <xi^2>^p_π ~ <xi^2>^p_K ~ 0.37 and <xi>^p_K ~ 0, …
We study the two-color QCD matter within two fundamental quark flavors via both chiral perturbation theory and Nambu--Jona-Lasinio model methods. The effective Lagrangian described by low lying meson and baryon, i.e., diquark, is derived, where the excitations locate in the extended $\mathrm{SU}(4)$ flavor symmetry space. We determine the leading order terms on the dependence of the baryon and axial isospin densities. Then, the two-color NJL model is employed to run the numerical simulation and the phase diagram in the plane of $μ-ν_{5}$ is plotted.
We discuss the role of the axial $U(1)_A$ symmetry in the chiral phase transition using the $U(N_f)_R\times U(N_f)_L$ linear sigma model with two massless quark flavors. We expect that above a certain temperature the axial $U(1)_A$ symmetry will be effectively restored as well as $SU(N_f)_R\times SU(N_f)_L$. Then we can construct a string-like static solution the $η$ string and a kink-like classical solution the domain wall during the chiral phase transition. We give out the possible signals for detecting the domain wall in ultrarelativistic heavy-ion collisions.
The existence of quark matter inside the cores of heavy neutron stars is a possibility which can be probed with modern astrophysical observations. We use an (axial)vector meson extended quark-meson model to describe quark matter in the core of neutron stars. We discover that an additional parameter constraint is necessary in the quark model to ensure chiral restoration at high densities. By investigating hybrid star sequences with various parameter sets we show that low sigma meson masses are needed to fulfill the upper radius constraints, and that the maximum mass of stable hybrid stars is on…
We present an effective model, which is an extension of the usual linear sigma model, that contains a low energy multiplet for every hadronic particle type. These multiplets are a scalar nonet, a pseudoscalar nonet, a vector nonet, an axialvector nonet, a baryon octet and a baryon decuplet. Tree level baryon masses and possible two body decuplet decays are calculated. The baryon masses are generated through spontaneous symmetry breaking. The calculated quantities are used to determine the model parameters through a multiparametric minimalization process, which compares the calculated physical …
The flavor evolution of neutrinos emitted by a supernova (SN) core is strongly affected by the refractive effects associated with the neutrino-neutrino interactions in the deepest stellar regions. Till now, all numerical studies have assumed the axial symmetry for the "multi-angle effects" associated with the neutrino-neutrino interactions. Recently, it has been pointed out in \cite{Raffelt:2013rqa} that removing this assumption, a new multi-azimuthal-angle (MAA) instability would emerge in the flavor evolution of the dense SN neutrino gas in addition to the one caused by multi-zenith-angle (M…
Exploiting an approximate phenomenological symmetry of the $J^{PC}=1^{+-}$ light axial vector mesons and using pole dominance, we calculate the flavor contributions to the nucleon tensor charge. The result depends on the decay constants of the axial vector mesons and their couplings to the nucleons.
It is well known that because of the axial anomaly in QCD, mesons with $J^P = 0^-$ are close to $SU(3)_{\mathrm{V}}$ eigenstates: the $eta^\prime(958)$ meson is largely a singlet, and the $η$ meson an octet. In contrast, states with $J^P = 1^-$ are flavor diagonal: \textit{e.g.}, the $ϕ(1020)$ is almost pure $\bar{s} s$. Using effective Lagrangians, we show how this generalizes to states with higher spin, assuming that they can be classified according to the unbroken chiral symmetry of $G_{\mathrm{fl}} = SU(3)_{\mathrm{L}} \times SU(3)_{\mathrm{R}}$. We construct effective Lagrangians from ter…
The strange and flavor-singlet axial form factors of the nucleon from lattice QCD
Helmholtz-Institut Mainz, Johannes Gutenberg-Universität Mainz(美因茨亥姆霍兹研究所);GSI Helmholtzzentrum für Schwerionenforschung(GSI重离子研究中心);Theoretical Physics Department, CERN(欧洲核子研究中心理论物理部);Helmholtz-Institut für Strahlen- und Kernphysik, Universität Bonn(波恩大学辐射与核物理亥姆霍兹研究所)
We study the vector and axial-vector form factors of radiative kaon decay within the framework of the gauged nonlocal effective chiral action from the instanton vacuum, focusing on the effects of flavor SU(3) symmetry breaking. The general tendency of the results are rather similar to those of radiative pion decays: The nonlocal contributions make the results of the vector form factor increased by about $20\,\%$, whereas they reduce those of the axial-vector form factor by almost $30\,\%$. Suppressing the prefactors consisting of the kaon mass and the pion decay constant, we scrutinize how the…
We study the restoration of chiral symmetry in linear sigma models with two quark flavors. The models taken into consideration have a U(2)_L x U(2)_R and an O(4) internal symmetry. The physical mesons of these models are sigma, pion, eta and a_0 where the latter two are not present in the O(4) model. Including two-loop contributions through sunset graphs we calculate the temperature behavior of the order parameter and the masses for explicit chiral symmetry breaking and in the chiral limit. Decay threshold effects introduced by the sunset graphs alter the temperature dependence of the condensa…