arXiv subjects
Publications and source records attributed to Michal Praszalowicz.
In this talk, we present our recent investigation on the magnetic moments of the exotic pentaquark states, based on the chiral quark-soliton model, all relevant intrinsic parameters being fixed by using empirical data.
We present in this talk a recent analysis for the magnetic moments of the baryon antidecuplet within the framework of the chiral quark-soliton model with linear $m_s$ corrections considered. We take into account the mixing of higher representations to the collective magnetic moment operator, which comes from the SU(3) symmetry breaking. Dynamical parameters of the model are fixed by experimental data for the magnetic moments of the baryon octet as well as by the masses of the octet, decuplet and of $Θ^{+}$. The magnetic moment of $Θ^{+}$ is rather sensitive to the pion-nucleon sigma term and ranges from $-1.19 {\rm n.m.}$ to $-0.33 {\rm n.m.}$ as the sigma term is varied from $Σ_{πN} = 45$ to 75 MeV, respectively. On top of them, we obtained that the strange magnetic moment of the nucleon has the value of $μ^{(s)}_N =+0.39$ n.m. within this scheme and turns out to be almost independent of the sigma term.
We examine SU(3) constraints on the spectrum and decay widths of cryptoexotic nucleon-like states in antidecuplet of pentaquarks. We show that in the ideal mixing scenario the number of free matrix elements describing splittings reduces from 4 to 2. Model-independent sum rules are derived. Using as input $Θ^+$ and $Ξ_{3/2}$ masses we show that it is difficult to interpret Roper and $N^{\ast}(1710)$ nucleon resonances as cryptoexotic pentaquarks. Large $N_c$ limit for antidecuplet and accompanying octet in the diqaurk picture and the analogy with the soliton model is also discussed.
We re-analyze the predictions of chiral-soliton models for the masses and decay widths of baryons in the exotic antidecuplet of flavour SU(3). The calculated ranges of the chiral-soliton moment of inertia and the π-nucleon scattering Σterm are used together with the observed baryon octet and decuplet mass splittings to estimate 1430 MeV < m_{Θ^+} < 1660 MeV} and 1790 MeV < m_{Ξ^{--}} < 1970 MeV. These are consistent with the masses reported recently, but more precise predictions rely on ambiguous identifications of non-exotic baryon resonances. The overall decay rates of antidecuplet states are sensitive to the singlet axial-current matrix element in the nucleon. Taking this from polarized deep-inelastic scattering experiments, we find a suppression of the total Θ^+ and Ξ^{--} decay widths that may not be sufficient by itself to reproduce the narrow widths required by experiments. We calculate SU(3) breaking effects due to representation mixing and find that they tend to suppress the Θ^+ decay width, while enhancing that of the Ξ^{--}. We predict light masses for some exotic 27 baryons, including the I=1, J^P={3/2}^+ Θ^+ and I=3/2, J^P={3/2}^+ Ξmultiplets, and calculate their decay widths.
Within the chiral soliton model the SU(3) breaking collective hamiltonian introduces representation mixing in the baryonic wave functions. We calculate ${\cal{O}}(m_s)$ effects of this mixing on the decay widths of decuplet and antidecuplet baryons. We find importance of the 27-plet admixture in the $Θ^+$ and $Ξ_{\bar{10}}$ decays. The role of the $1/N_c$ nonleading terms in ${\cal{O}}(m_s)$ transition matrix elements is discussed.
We discuss the consequences of the chiral doubling scenario for baryons built of heavy and light quarks. In particular, we use the soliton description for baryons, demonstrating why each heavy-light baryon should be accompanied by the opposite parity partner. Our argumentation holds both for ordinary baryons and for exotic heavy pentaquarks which are required by the symmetries of QCD to appear in parity doublets, seperated by the mass shift of the chiral origin. Interpreting the recently observed by BaBaR, CLEO and Belle charmed mesons with assignment $(0^+,1^+)$ as the chiral partners of known $D$ and $D^*$ mesons, allows us to estimate the parameters of the mesonic effective lagrangian, and in consequence, estimate the masses of ground states and excited states of both parities. In particular, we interpret the state recently reported by the H1 experiment at HERA as a chiral partner $\tildeΘ_c^0(3099)$ of yet undiscovered ground state pentaquark $Θ_c^0(2700)$.
In the chiral quark soliton model the smallness of $Θ^+$ width is due to the cancellation of the coupling constants which are of different order in $N_c$. We show that taking properly into account the flavor structure of relevant SU(3) representations for arbitrary number of colors enahnces the nonleading term by an additional factor of $N_c$, making the cancellation consistent with the $N_c$ counting. Moreover, we show that, for the same reason, $Θ^+$ width is suppressed by a group-theoretical factor ${\cal O}(1/N_c)$ with respect to $Δ$ and discuss the $N_c$ dependence of the phase space factors for these two decays.
We investigate the magnetic moments of the baryon antidecuplet within the framework of the chiral quark-soliton model in the chiral limit in a ``\emph{model-independent}'' approach. Sum rules for the magnetic moments are derived. The magnetic moment of $Θ^{+}$ is found to be about $0.2\sim 0.3 μ_{N}$.
The mass of the newly discovered pentaquark is calculated within the framework of the SU(3) Skyrme Model. Various estimates based on the \emph{model independent} approach are compared with the model results and with the Chiral Quark Model. Our discussion shows that $Θ^{+}$ is light with the mass of the order 1.5 GeV.
We use a simple, instanton motivated, nonlocal chiral quark model to calculate pion Generalized Distribution Amplitudes (GDAs). The nonlocality appears due to the momentum dependence of the constituent quark mass, which we take in a form of a generalized dipole formula. With this choice all calculations can be performed directly in the Minkowski space and the sensitivity to the shape of the cutoff function can be studied. We demonstrate that the model fulfills soft pion theorems both for chirally even and chirally odd GDAs. The latter one cannot be derived by the methods of current algebra. Whenever possible we compare our results with the existing data. This can be done for the pion electromagnetic form factor and quark distributions as measured in the proton-pion scattering.
We calculate skewed parton distributions $H^I$ of a pion within a non-local NJL model with momentum dependent constituent quark mass $M(k)$. In the forward limit $H^I$ correspond to parton distributions, whereas for $t<0$, $H^I$ is related to the pion electromagnetic form-factor
We formulate the nonlocal NJL model with a momentum dependent constituent quark mass and calculate pion light cone wave functions of twist 2 and 3. The leading twist wave function is not asymptotic and agrees well with the new CLEO data. Normalization conditions for the twist 3 wave functions are used to calculate the quark condensate. A prescription to calculate the gluon condensate is proposed. The numerical value of the gluon condensate nicely agrees with the phenomenological value, whereas the quark condensate is larger than the phenomenological value of $-(250$ MeV$)^3$. The relation between the $k_T^2$ moments and mixed condensates are used to estimate the mixed quark-gluon condensate of dimension 5.
The quantization conditions which come from the requirement of the singlevaluedness of the odderon wave function are formulated and solved numerically in the 4 dimensional space of the odderon charge q3 and the conformal weight h. It turns out that these conditions are fulfilled along one dimensional curves parametrized by a discrete set of values of Re(h) in 3 dimensional subspace (Im(h),Im(q3),Re(q3)). The odderon energy calculated along these curves corresponds in all cases to the intercept lower than 1.
We present the recent investigation on the effect of the SU(3) symmetry breaking in the spin structure of the octet baryons.
We analyze the semileptonic weak decays of the octet baryons in a "{\em model independent}" approach, based on the algebraic structure of the Chiral Quark-Soliton Model. We argue that this analysis is in fact more general than the model itself. While the symmetry breaking for the semileptonic decays themselves is not strong, other quantities like $Δs$ and $ΔΣ$ are much more affected. We calculate $ΔΣ$ and $Δq$ for all octet baryons. Unfortunately, large experimental errors of $Ξ^-$ decays propagate in our analysis, in particular, in the case of $ΔΣ$ and $Δs$. Only if the errors for these decays are reduced, the accurate theoretical predictions for $ΔΣ$ and $Δs$ will be possible.
Using the known experimental data for the hyperon semileptonic decay constants, we calculate integrated quark densities $Δq_Λ$ and $% ΔΣ_Λ$ for the hyperon $Λ$ with flavor SU(3) symmetry breaking taken into account. Symmetry breaking is implemented with the help of the chiral quark-soliton model in an approach, in which the dynamical parameters are fixed by the experimental data for six hyperon semileptonic decay constants. This parametrization allows us to reproduce the first moment of the $g_1^{\rm p}(x)$ of the proton. For the $Λ$ we obtain: $Δu_Λ=Δd_Λ \approx 0$ and $Δs_Λ$ of the order of 1. Unfortunately large experimental errors of $Ξ^-$ decays propagate in our analysis especially in the case of $ΔΣ_Λ$ and $Δs_Λ$. Only if the errors for these decays are reduced, the accurate theoretical predictions for $ΔΣ_Λ$ and $% Δs_Λ$ will be possible.
We investigate the hyperon semileptonic decays and the quark spin content of the proton $ΔΣ$ taking into account flavor SU(3) symmetry breaking. Symmetry breaking is implemented with the help of the chiral quark-soliton model in an approach, in which the dynamical parameters are fixed by the experimental data for six hyperon semileptonic decay constants. As a result we predict the unmeasured decay constants, particularly for $Ξ^0 \to Σ^+$, which will be soon measured and examine the effect of the SU(3) symmetry breaking on the spin content $ΔΣ$ of the proton. Unfortunately large experimental errors of $Ξ^-$ decays propagate in our analysis making $ΔΣ$ and $Δs$ practically undetermined. We conclude that statements concerning the values of these two quantities, which are based on the exact SU(3) symmetry, are premature. We stress that the meaningful results can be obtained only if the experimental errors for the $Ξ$ decays are reduced.