Wave functions for dynamically generated resonances; the two $Λ(1405)$ and $Λ(1670)$
J. Yamagata-Sekihara, J. Nieves, E. Oset
备注：
5pages, 1 figure. To appear in the proceedings of the International Workshop on Chiral Symmetry in Hadrons and Nuclei (Chiral10), Valencia, Spain, Jun 21-24, 2010
In this work we develop a formalism to evaluate wave functions in momentum and coordinate space for the resonant states dynamically generated in a unitary coupled channel approach. The on shell approach for the scattering matrix, commonly used, is also obtained in Quantum Mechanics with a separable potential, which allows one to write wave functions in a trivial way. We develop useful relationships among the couplings of the dynamically generated resonances to the different channels and the wave functions at the origin. The formalism provides an intuitive picture of the resonances in the coupled channel approach, as bound states of one bound channel, which decays into open ones. It also provides an insight and practical rules for evaluating couplings of the resonances to external sources and how to deal with final state interaction in production processes. As an application of the formalism we evaluate the wave functions of the two $Λ(1405)$ states in the $πΣ$, $\bar{K} N$ and other coupled channels. It also offers a practical way to study three body systems when two of them cluster into a resonance.
We study the radiative decay into $γ$ and a baryon of the SU(3) decuplet of ten resonances that are dynamically generated from the interaction of vector mesons with baryons of the decuplet. We obtain quite different partial decay widths for the various resonances, and for different charge states of the same resonance, suggesting that the experimental investigation of these radiative decays should bring much information on the nature of these resonances.
We evaluate the radiative decay into a vector a pseudoscalar and a photon of several resonances dynamically generated from the vector vector interaction. The process proceeds via the decay of one of the vector components into a pseudoscalar and a photon, which have an invariant mass distribution very different from phase space as a consequence of the two vector structure of the resonances. Experimental work along these lines should provide useful information on the nature of these resonances.
We present the formalism for the decay of dynamically generated scalar mesons with open- or hidden-charm and give results for the decay of D^*_{s0} (2317) to γD_s^* plus that of a hidden charm scalar meson state predicted by the theory around 3700 MeV decaying into γJ/ψ.
We study the interaction of the octet of vector mesons with the decuplet of baryons using Lagrangians of the hidden gauge theory for vector interactions. The unitary amplitudes in coupled channels develop poles that can be associated with some known baryonic resonances, while there are predictions for new ones at the energy frontier of the experimental research. The work offers guidelines on how to search for these resonances.
In this talk I report on recent work related to the dynamical generation of baryonic resonances, some made up from pseudoscalar meson-baryon, others from vector meson-baryon and a third type from two meson-one baryon systems. We can establish a correspondence with known baryonic resonances, reinforcing conclusions previously drawn and bringing new light on the nature of some baryonic resonances of higher mass.
In this talk we report on the use of a chiral unitary approach for the interaction of the octets of meson and baryon and the octet of mesons with the decuplet of baryons. Two octets of $J^π=1/2^-$ baryon states and a singlet are generated dynamically in the first case, resulting in the case of strangeness $S=-1$ in two poles of the scattering matrix close to the nominal $Λ(1405)$ resonance. In the second case many resonances are also generated, among them an exotic baryon with S=1 corresponding to a $ΔK$ resonance. We make suggestions of experiments which could show evidence for the existence …
We make a theoretical study of the s-wave interaction of the nonet of vector mesons with the octet of pseudoscalar mesons starting from a chiral invariant Lagrangian and implementing unitarity in coupled channels. By looking for poles in the unphysical Riemann sheets of the unitarized scattering amplitudes, we get two octets and one singlet of axial-vector dynamically generated resonances. The poles found can be associated to most of the low lying axial-vector resonances quoted in the Particle Data Book: $b_1(1235)$, $h_1(1170)$, $h_1(1380)$, $a_1(1260)$, $f_1(1285)$ and two poles to the $K_1(…
We study the radiative decay properties of the charmonium-like X, Y and Z mesons generated dynamically from vector meson-vector meson interaction in the framework of a unitarized hidden-gauge formalism. In the present work we calculate the one- and two-photon decay widths of the hidden-charm Y(3940), Z(3930) (or X(3915)) and X(4160) mesons in the framework of the vector meson dominance formalism. We obtain good agreement with experiment in case of the two photon width of the X(3915) which we associate with the $2^+$ resonance that we find at 3922 MeV.
We study baryon resonances with heavy flavor in a molecular approach, thus as dynamically generated by baryon-meson scattering. This is accomplished by using a unitary coupled-channel model taking, as bare interaction, the extension of the Weinberg-Tomozawa SU(3) Lagrangian. A special attention is payed to the inclusion of heavy-quark spin symmetry and to the study of the generated baryon resonances that complete the heavy-quark spin multiplets. Our model reproduces the Λ_b(5912) and Λ_b(5920) baryons, which were recently observed by the LHCb collaboration. According to our analysis, these two…
Identifying a zero-range exchange of vector mesons as the driving force for the s-wave scattering of pseudo-scalar mesons off the baryon ground states, a rich spectrum of hadronic nuclei is formed. We argue that chiral symmetry and large-$N_c$ considerations determine that part of the interaction which generates the spectrum. We suggest the existence of strongly bound crypto-exotic baryons, which contain a charm-anti-charm pair. Such states are narrow since they can decay only via OZI-violating processes.
We study the vector-vector interaction within the framework of the hidden gauge formalism for the sector with quantum numbers charm C=0 and strangeness S=0 in the region around 4000 MeV. We get five poles, three of which could be identified with the Y(3940), Z(3930) and X(4160). These poles appear with quantum numbers I=0 and $J^{PC}=0^{++},2^{++}$ and $2^{++}$, respectively, and can be considered as hadronic molecules made of $D^*\bar{D}^*$, $D_s^*\bar{D}^*_s$.
We present a recent study of vector meson-vector meson interaction using a unitary approach based on the hidden-gauge Lagrangians. We find that 11 states get dynamically generated, corresponding to poles of the scattering matrices on the second Riemann sheet. Five of them are associated to the $f_0(1370)$, $f_0(1710)$, $f_2(1270)$, $f_2'(1525)$, and $K^*_2(1430)$, by comparing the mass, width, and decay pattern of these states with those of their experimental counterparts. Six others with the quantum numbers of $h_1$, $a_0$, $b_1$, $a_2$, $K^*_0$, and $K_1$ can not be clearly identified with a…
We study the vector-vector interaction within the framework of the hidden gauge formalism for the channels with quantum numbers Charm C=0 and Strangeness S=0 in the energy region around 4000 MeV. By looking for poles in the complex plane we find three resonances that could be identified by the mass, width and quantum numbers with the Y(3940), Z(3940) and X(4160), these poles appear with isospin I=0 and J^{PC}=0^{++}, 2^{++} and 2^{++} respectively. Whereas the Y(3940) and Z(3940) are coupled more strongly to D^*\bar{D}^*, the X(4160) is basically a D^*_s \bar{D}^*_s molecular state. Another tw…
We study the radiative decay into $γ$ and a baryon of the SU(3) octet and decuplet of nine and ten resonances that are dynamically generated from the interaction of vector mesons with baryons of the octet and the decuplet respectively. We obtain quite different partial decay widths for the various resonances, and for different charge states of the same resonance, suggesting that the experimental investigation of these radiative decays should bring much information on the nature of these resonances. For the case of baryons of the octet we determine the helicity amplitudes and compare them with …
O(N) linear $σ$ model is solvable in the large $N$ limit and hence provides a useful theoretical laboratory to test various unitarization approximations. We find that the large $N_c$ limit and the $m_σ\to \infty$ limit do not commute. In order to get the correct large $N_c$ spectrum one has to firstly take the large $N_c$ limit. We argue that the $f_0(600)$ meson may not be described as generated dynamically. On the contrary, it is most appropriately described at the same level as the pions, i.e, both appear explicitly in the effective lagrangian. Actually it is very likely the $σ$ meson respo…
We study dynamically generated $a_0$ resonances by interactions between vector mesons including their coupling to channels of pseudoscalar mesons within coupled-channel approach. Both vector and pseudoscalar mesons are considered as $t$-channel exchanged mesons for calculating interactions between vector mesons. Analogous to $a_0(980)$ as a $K\bar K-πη$ dynamically generated state, there is an $a_0(1710)$ as a coupled channel dynamically generated state near $K^*\bar{K}^*$ threshold. The channels involved are $ρϕ,K^*\bar{K}^*,ρω, K\bar{K},πη$. This $a_0$ mainly decays to $ρω$, $πη$ and $K\bar{…
The idea of ``dynamically'' generated parton distribution functions, based on regular initial conditions at low momentum scale, is reanalyzed with particular emphasize paid to its compatibility with the factorization mechanism. Basic consequences of this approach are discussed and compared to those of the conventional approach, employing singular initial distribution functions.
In this talk I report on the recent developments in the subject of dynamically generated resonances. In particular I discuss the $γp \to K^0 Σ^+$ and $γn \to K^0 Σ^0$ reactions, with a peculiar behavior around the $K^{*0} Λ$ threshold, due to a $1/2^-$ resonance around 2035 MeV. Similarly, I discuss a BES experiment, $J/ψ\to ηK^{*0} \bar K^{*0}$ decay, which provides evidence for a new $h_1$ resonance around 1830 MeV that was predicted from the vector-vector interaction. A short discussion is then made about recent advances in the charm and beauty sectors.
The scalar-meson assignments of Shakin and Wang in a generalized Nambu--Jona-Lasinio model are contradicted by recent experimental information. Also the strict distinction made by these authors between ``intrinsic'' and ``dynamically generated'' states is contested, as well as a number of other statements.
In this presentation I explain our framework for dynamically generating resonances from the meson meson interaction. Our model generates many poles in the T-matrix which are associated with known states, while at the same time new states are predicted.
It is shown that the gauge fixings of the Z and the W fields and three scalars are via nonconserved axial-vector and charged vector currents of massive fermions dynamically generated by fermion masses in the SM of EW interactions. The top quark mass provides enough strength for this chiral symmetry breaking. The masses of the three scalars are determined to be about $10^{14}$ GeV. These scalars have negative probability. They are the nonperturbative solutions of the SM. A new perturbation theory with dynamically generated and fixed gauge fixings is constructed. The Faddeev-Popov procedure is n…
We study the problem whether the $σ$ meson is generated `dynamically'. A pedagogical analysis on the toy O(N) linear sigma model is performed and we find that the large $N_c$ limit and the $m_σ\to \infty$ limit does not commute. The sigma meson may not necessarily be described as a dynamically generated resonance. On the contrary, the sigma meson may be more appropriately described by considering it as an explicit degree of freedom in the effective lagrangian.
We study the interaction of vector mesons with the octet of stable baryons in the framework of the local hidden gauge formalism using a coupled channels unitary approach, including also the pseudoscalar-baryon channels which couple to the same quantum numbers. We examine the scattering amplitudes and their poles, which can be associated to known $J^P=1/2^-,3/2^-$ baryon resonances, and determine the role of the pseudoscalar-baryon channels, changing the width and eventually the mass of the resonances generated with only the basis of vector-baryon states.
In this work we present our model that dynamically generates resonances from charmed and light pseudoscalar and vector mesons. The model generates a rich spectrum of charmed and hidden charm scalar and axial resonances, most of them which can be associated with observed states. Other states are predicted, in particular a hidden charm scalar resonance with mass close to the $D\bar D$ threshold. For this resonance we present calculations which show that an observed enhancement in the $D\bar D$ mass spectrum measured by Belle in reactions producing $D\bar D J/ψ$ in the final state could be origin…
Radiative decays of the $Λ(1520)$ as a dynamically generated resonance
Guangxi Normal University（广西师范大学）；Beihang University（北京航空航天大学）；École Centrale de Pékin/School of General Engineering, Beihang University（北京航空航天大学中法工程师学院）；Institute of Modern Physics, Chinese Academy of Sciences（中国科学院近代物理研究所）
Recent developments in hadron spectroscopy triggers the discussion on various exotic configurations beyond the simple three-quark state for baryons and quark-anti-quark pair for mesons. In particular, the states observed near a two-hadron threshold are often regarded as candidates of hadronic molecules, which are made of constituent hadrons and dynamically generated by the hadronic interactions. However, identification of the hadronic molecules involves several subtle difficulties which are often overlooked or underestimated. Here we summarize these subtleties and present a promising approach …
It is explained why the interpretation of the resonances $f_{2}(1270),$ $a_{1}(1260)$ and $f_{0}(1370)$ as quark-antiquark states is legitimate. The result of the quark model and of recently performed Bethe-Salpeter studies are not (necessarily) in conflict and can be understood as two different approaches toward the description of the same quark-antiquark resonances.
We will study open and hidden charm scalar meson resonances within two different models. The first one is a direct application of a chiral Lagrangian already used to study flavor symmetry breaking in Skyrme models. In another approach to the problem a SU(4) symmetric Lagrangian is built and the symmetry is broken down to SU(3) by identifying currents where heavy mesons are exchanged and suppressing those. Unitarization in couple channels leads to dynamical generation of resonances in both models, in particular a new hidden charm resonance with mass 3.7 GeV is predicted. The small differences b…
We discuss baryon resonances which are dynamically generated in hadron dynamics based on chiral coupled channels approach. With the dynamical description of the baryon resonance, we discuss the origin of the resonance pole, finding that for the description of N(1535) some other components than meson and baryon are necessary. Since the chiral unitary model provides a microscopic description in terms of constituent hadrons, it is straightforward to calculate transition amplitudes and form factors of resonances without introducing further parameters. Finally we briefly discuss few-body nuclear ka…
In two recent reactions by Belle producing $D\bar D$ and $D\bar D^*$ meson pairs, peaks above threshold have been measured in the differential cross sections, possibly indicating new resonances in these channels. We want to study such reactions from the point of view that the $D$ meson pairs are produced from already known or predicted resonances below threshold. Our study shows that the peak in the $D\bar D^*$ production is not likely to be caused by the X(3872) resonance, but the peak seen in $D\bar D$ invariant mass can be well described if the $D\bar D$ pair comes from the already predicte…
The interactions of $\bar{D}Σ_{c}$-$\bar DΛ_c$, $\bar{D}^{*}Σ_{c}$-$\bar D^*Λ_c$, and related strangeness channels, are studied within the framework of the coupled channel unitary approach with the local hidden gauge formalism. A series of meson-baryon dynamically generated relatively narrow $N^*$ and $Λ^*$ resonances are predicted around 4.3 GeV in the hidden charm sector. We make estimates of production cross sections of these predicted resonances in $\bar{p} p $ collisions for PANDA at the forthcoming FAIR facility.
We study 4D QED in which one spatial dimension is dynamically generated from 3D action, following the mechanism proposed by Arkani-Hamed, Cohen and Georgi. In this model, the generated fourth dimension is discretized by an interval parameter $a$. We examine the phenomenological constraint on the parameter $a$ coming from the collider experiments on the QED process $e^+ e^- \to γγ$. It is found that the LEP2 experiments give the constraint of $1/a \simgt 461\gev$. Expected bound on the same parameter $a$ at the future $e^+ e^-$ linear collider is briefly discussed.
The strength of the dynamically generated Yukawa coupling among composite fields is calculated. The system of N=1 supersymmetric SU(2) gauge theory with massive three flavors is considered as an example. We use the techniques of "integrating in" the gluino-gluino bound state in the low energy effective theory and the instanton calculation and Shifman-Vainshtein-Zakharov sum rule (QCD sum rule) in the fundamental theory. The obtained value of the Yukawa coupling is of the order of unity. The method which is developed in this paper can be applied to the other supersymmetric gauge theories.
We study the interaction of vector mesons with the octet of stable baryons in the framework of the local hidden gauge formalism using a coupled channels unitary approach. We examine the scattering amplitudes and their poles, which can be associated to known J^P=1/2^-,3/2^- baryon resonances, in some cases, or give predictions in other ones. The formalism employed produces doublets of degenerate J^P=1/2^-,3/2^- states, a pattern which is observed experimentally in several cases. The findings of this work should also be useful to guide present experimental programs searching for new resonances, …
Following a model based on the $\rm{SU}(8)$ symmetry that treats heavy pseudo-scalars and heavy vector mesons on an equal footing, as required by heavy quark symmetry, we study the interaction of baryons and mesons in coupled channels within an unitary approach that generates dynamically poles in the scattering $T$-matrix. We concentrate in the exotic channels with negative charm quantum number for which there is the experimental claim of one state.
We present recent results on the vector meson-vector meson and vector meson-baryon interaction using a unitary approach based on the hidden-gauge Lagrangians. For the vector-vector case we find that 11 states get dynamically generated, corresponding to poles of the scattering matrices on the second Riemann sheet. In the vector-baryon sector we also find 9 states dynamically generated from the vector-baryon octet interaction and 10 from the vector-baryon decuplet interaction. We also report on baryon states found from the interaction of two mesons and a baryon.
It is generally assumed that the dynamical generation of the Higgs mass parameter of the superpotential, $μ$, implies the existence of a light singlet at or below the supersymmetry breaking scale, $\msusy$. We present a counter-example in which the singlet field can receive an arbitrarily heavy mass (\eg, of the order of the Planck scale, $M_{\rm P}\approx 10^{19}~\gev$). In this example, a non-zero value of $μ$ is generated through soft supersymmetry breaking parameters and is thus naturally of the order of $\msusy$.
Identifying a zero-range exchange of vector mesons as the driving force for the s-wave scattering of pseudo-scalar mesons off the baryon ground states, a rich spectrum of molecules is formed. We argue that chiral symmetry and large-$N_c$ considerations determine that part of the interaction which generates the spectrum. We suggest the existence of strongly bound crypto-exotic baryons, which contain a charm-anti-charm pair. Such states are narrow since they can decay only via OZI-violating processes. A narrow nucleon resonance is found at mass 3.52 GeV. It is a coupled-channel bound state of th…
We report on some recent developments in understanding the nature of the low-lying mesonic resonances $f_0(1370)$, $f_0(1710)$, $f_2(1270)$, $f_2'(1525)$, and $K_2^*(1430)$. In particular we show that these five resonances can be dynamically generated from vector meson--vector meson interaction in a coupled-channel unitary approach, which utilizes the phenomenologically very successful hidden-gauge Lagrangians to produce the interaction kernel between two vector mesons, which is then unitarized by the Bethe-Salpeter-equation method. The data on the strong decay branching ratios, total decay wi…
Neutrinos may be the harbingers of new dark sectors, since the renormalizable neutrino portal allows for their interactions with hidden new physics. We propose here to use this fact to connect the generation of neutrino masses to a light dark sector, charged under a new $U(1)_{\cal D}$ dark gauge symmetry. We introduce the minimal number of dark fields to obtain an anomaly free theory with spontaneous breaking of the dark symmetry, and obtain automatically the inverse seesaw Lagrangian. In addition, the so-called $μ$-term of the inverse seesaw is dynamically generated and technically natural i…
The $ρρ$ interaction and the corresponding dynamically generated bound states are revisited. We demonstrate that an improved unitarization method is necessary to study the pole structures of amplitudes outside the near-threshold region. In this work, we extend the study of the covariant $ρρ$ scattering in a unitarized chiral theory to the $S$-wave interactions for the whole vector-meson nonet. We demonstrate that there are unphysical left-hand cuts in the on-shell factorization approach of the Bethe-Salpeter equation. This is in conflict with the correct analytic behavior and makes the so-obta…
The dynamically generated $N(1535)$ state in the $Λ_c^+ \to p\bar{K}^0 π^0$ decay
Beihang University（北京航空航天大学）；Zhengzhou University（郑州大学）；École Centrale de Pékin/School of General Engineering, Beihang University（北京航空航天大学高等工程学院）；Peng Huanwu Collaborative Center for Research and Education, Beihang University（北京航空航天大学彭桓武研究中心）；Beijing Key Laboratory of Advanced Nuclear Materials and Physics, Beihang University（北京航空航天大学先进核材料物理北京市重点实验室）；Southern Center for Nuclear-Science Theory (SCNT), Institute of Modern Physics, Chinese Academy of Sciences（中国科学院近代物理研究所南方核科学理论中心）；State Key Laboratory of Heavy Ion Science and Technology, Institute of Modern Physics, Chinese Academy of Sciences（中国科学院近代物理研究所重离子科学和技术国家重点实验室）；School of Nuclear Sciences and Technology, University of Chinese Academy of Sciences（中国科学院大学核科学与技术学院）
The interaction of the low lying pseudo-scalar mesons with the ground state baryons in the charm sector is studied within a coupled channel approach using a t-channel vector-exchange driving force. The amplitudes describing the scattering of the pseudo-scalar mesons off the ground-state baryons are obtained by solving the Lippmann--Schwinger equation. We analyze in detail the effects of going beyond the $t=0$ approximation. Our model predicts the dynamical generation of several open charmed baryon resonances in different isospin and strangeness channels, some of which can be clearly identified…
The interaction potentials between vector mesons and octet baryons are calculated explicitly with a summation of t-, s-, u-channel diagrams and a contact term originating from the tensor interaction. Many resonances are generated dynamically in different channels of strangeness zero by solving the coupled-channel Lippman-Schwinger equations with the method of partial wave analysis, and their total angular momenta are determined. The spin partners N(1650)1/2^{-} and N(1700)3/2^-, N(1895)1/2^{-} and N(1875)3/2^-, and the state N(2120)3/2^- are all produced respectively in the isospin I=1/2 secto…
In view of the recent results of lattice QCD simulation in the P11 partial wave that has found no clear signal for the three-quark Roper state we investigate a different mechanism for the formation of the Roper resonance in a coupled channel approach including the $πN$, $πΔ$ and $σN$ channels. We fix the pion-baryon vertices in the underlying quark model while the $s$-wave sigma-baryon interaction is introduced phenomenologically with the coupling strength, the mass and the width of the $σ$ meson as free parameters. The Laurent-Pietarinen expansion is used to extract the information about the …
We study baryon resonances with heavy flavor in a molecular approach, thus as dynamically generated by meson-baryon scattering. This is accomplished by using a unitary coupled-channel model taking, as bare interaction, the extension to four flavors and spin symmetry of the Weinberg-Tomozawa interaction potential. A special attention is paid to the inclusion of heavy-quark spin symmetry and to the studies of the generated baryon resonances which complete the heavy-quark spin multiplets. We reproduce few charmed and strange baryon resonances found experimentally, that is, Λ_c(2595), Λ_c(2625), Ξ…
In this work we study the radiative decay of dynamically generated $J^P=\oh^-$ charm baryons into the ground state $J^P=\oh^+$ baryons. Since different theoretical interpretations of these baryonic resonances, and in particular of the $Λ_c(2595)$, give different predictions, a precise experimental measurement of these decays would be an important step for understanding their nature.
In this paper we investigate the non-perturbative generation of an anomalous magnetic moment for massless fermions in the presence of an external magnetic field. In the context of massless QED in a magnetic field, we prove that the phenomenon of magnetic catalysis of chiral symmetry breaking, which has been associated in the literature with dynamical mass generation, is also responsible for the generation of a dynamical anomalous magnetic moment. As a consequence, the degenerate energy of electrons in Landau levels higher than zero exhibits Zeeman splitting. We explicitly report the splitting …
Recent studies have shown that the well established $Λ_c(2595)$ resonance contains a large meson-baryon component, which can vary depending on the specific formalism. In this work, we examine such a picture by utilizing the compositeness condition and the large number of colors ($N_c$) expansion. We examine three different models fulfilling two body unitarity in coupled-channels, and adopting renormalization schemes where the mass of the $Λ_c(2595)$ resonance is well described, but not necessarily its width, since we do not consider three body channels and work at the isospin symmetric limit. …
It is argued that the quantum gravity attractions dynamically generate tiny degenerate Majorana masses for the neutrinos. The unequal masses of the charged leptons then induce a computable neutrino mass matrix with splittings and mixings through the electroweak interactions. In this way the Standard Model including quantum gravity can accommodate and predict the neutrino masses and mixings. Some consequences are pointed out.
We analyze two recent reactions of Belle, producing $D\bar D$ and $D\bar D^*$ states that have an enhancement of the invariant $D\bar D$, $D\bar D^*$ mass distribution close to threshold, from the point of view that they might be indicative of the existence of a hidden charm scalar and an axial vector meson states below $D\bar D$ or $D\bar D^*$ thresholds, respectively. We conclude that the data is compatible with the existing prediction of a hidden charm scalar meson with mass around 3700 MeV, though other possibilities cannot be discarded. The peak seen in the $D\bar D^*$ spectrum above thre…
The aim of the thesis is to study models of the electroweak symmetry breaking caused by dynamically generated masses of quarks and leptons. (1) We perform the basic analysis whether the main underlying idea, that the masses of only known fermions can provide the electroweak symmetry breaking, is actually feasible. For that we elaborate a two-composite-Higgs-doublet model of the top-quark and neutrino condensation. The model suggests rather large number, $\mathcal{O}(100)$, of right-handed neutrinos. (2) We analyze the model of strong Yukawa dynamics where the dynamical fermion mass generation …
We analyze s-wave pion-nucleon scattering in a unitarized chiral effective Lagrangian including all dimension two contact terms. We find that both the S11(1535) and the S11(1650) are dynamically generated, but the S31(1620) is not. We further discuss the structure of these dynamically generated resonances.
We compare and review the theoretical predictions for the $\bar{K}N$ and $ηN$ elastic amplitudes where sizable variations are found among the considered approaches, especially at subthreshold energies relevant for studies of kaonic atoms and meson-nuclear quasi-bound states. Conditions for an appearance of dynamically generated states in meson-baryon multi-channel interactions are established and discussed for the $\bar{K}N$ and $ηN$ systems.
The quark-level linear sigma model is revisited, in particular concerning the identification of the f_0(400-1200) (or σ(600)) scalar meson as the chiral partner of the pion. We demonstrate the predictive power of the linear sigma model through the pi-pi and pi-N s-wave scattering lengths, as well as several electromagnetic, weak, and strong decays of pseudoscalar and vector mesons. The ease with which the data for these observables are reproduced in the linear sigma model lends credit to the necessity to include the sigma as a fundamental q\bar{q} degree of freedom, to be contrasted with appro…
We consider the dilepton emission from a dense and hot hadron gas near a critical point. The hadron gas is described as a resonance one. The dilepton spectrum generated by vector resonances is shown to be equivalent to the one generated by quarks.
We show that the $Ξ(1690)$ resonance can be dynamically generated in the $s$-wave $\bar{K} Σ$-$\bar{K} Λ$-$πΞ$-$ηΞ$ coupled-channels chiral unitary approach. In our model, the $Ξ(1690)$ resonance appears near the $\bar{K} Σ$ threshold as a $\bar{K} Σ$ molecular state and the experimental data are reproduced well. We discuss properties of the dynamically generated $Ξ(1690)$.
Recently, the compositeness, defined as the norm of a two-body wave function for bound and resonance states, has been investigated to discuss the internal structure of hadrons in terms of hadronic molecular components. From the studies of the compositeness, it has been clarified that the two-body wave function of a bound state can be extracted from the residue of the scattering amplitude at the bound state pole. Of special interest is that the two-body wave function from the scattering amplitude is automatically normalized. In particular, while the compositeness is unity for energy-independent…
Nonperturbative studies of the strong running coupling constant in the infrared region are discussed. Starting from the analyses of the Dyson -- Schwinger equations in the gauge sector of QCD, the conclusion is made on an incomplete fixing of the perturbation theory summation ambiguity within "(forced) analytization procedure" (called also a dispersive approach). A minimal model for $\barα_s(q^2)$ is proposed so that the perturbative time-like discontinuity is preserved and nonperturbative terms not only remove the Landau singularity but also provide the ultraviolet convergence of the gluon co…
