arXiv subjects

M. Praszalowicz

Publications and source records attributed to M. Praszalowicz.

17 recordsLinked to original sources

arXiv2009

Covariant Non-local Chiral Quark Model and Pion-photon Transition Distribution Amplitudes

Using non-local chiral quark model with simple pole ansatz for mass dependence on momentum and non-local currents satisfying Ward-Takahashi identities, we calculate pion to photon transition distribution amplitudes and relevant form factors. For vector amplitude we recover correct normalization fixed by the axial anomaly. We find that due to the non-locality in the vector current, the value of axial form factor at zero momentum transfer is lowered with respect to the vector form factor. Such behaviour - consistent with experiment - is not seen in the local models. Where possible we compare our results to the experimental data.

hep-ph↗

arXiv2005

Successes and Problems of Chiral Soliton Approach to Exotic Baryons

We briefly review the formulation of chiral quark soliton model and explain the difference and similarities with the Skyrme model. Next, we apply the model to calculate non-exotic and exotic mass spectra. We concentrate on large $N_{c}$ counting both for mass splittings and decay widths. It is shown that pure large $N_{c}$ arguments do not explain the small width of exotic pentaquark states.

hep-ph↗

arXiv2003

An attempt to construct pion distribution amplitude from the PCAC relation in the nonlocal chiral quark model

Using the PCAC relation, we derive a compact formula for the pion decay constant $F_π$ in the nonlocal chiral quark model. For practical calculations this formula may be used both in the Minkowski and in the Euclidean space. For the pion momentum $P_μ\to0$ it reduces to the well known expression derived earlier by other authors. Using a generalized dipole Ansatz for the momentum dependence of the constituent quark mass in the Minkowski space, we express $F_π^{2}$ in terms of a single integral over the quark momentum fraction $u$. We interpret the integrand as a pion distribution amplitude $ϕ(u)$. We discuss its properties and compare with the $π$DA's obtained in other models.

hep-ph↗

arXiv2002

Spontaneously Broken Chiral Symmetry and Hard QCD Phenomena

These are the mini-proceedings of the workshop ``Spontaneously Broken Chiral Symmetry and Hard QCD Phenomena" held at the Physikzentrum Bad Honnef from July 15 to 19, 2002. Every author presents a summary of his talk. The transparencies of all speakers and further information on the workshop can be found on the website: http://www.tp2.ruhr-uni-bochum.de/hardreactions.html

hep-ph↗

arXiv2002

Vacuum condensates and the pion wave functions in the nonlocal chiral model

We use the simple instanton motivated Nambu Jona-Lasinio - type model to calculate a twist 3 pseudoscalar pion light cone wave function. Using normalisation condition for this wave function we calculate the quark condensate and also the gluon condensate, which agree with the phenomenological values for these quantities. Since we can compute also the k_T^2 dependence of the light cone wave functions, we calculate k_T^2 moments of the pseudo-scalar and axial-vector wave functions which are related to the mixed vacuum condensates. This allows us to extract the condensates and compare them with existing estimates.

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arXiv2001

Nonleptonic $Ω^{-}$ decays and the Skyrme model

Nonleptonic $Ω^{-}$ decay branching ratios are estimated by means of the QCD enhanced effective weak Hamiltonian supplemented by the SU(3) Skyrme model used to estimate the nonperturbative matrix elements. The model has only one free parameter, namely the Skyrme charge $e$, which is fixed through the experimental values of the octet-decuplet mass splitting $Δ$ and the axial coupling constant $g_{A}$. The whole scheme is equivalent to that which works well for the nonleptonic hyperon decays. The ratios of calculated amplitudes are in agreement with experiment. However, the absolute values are about twice too large if short-distance corrections and only ground intermediate states are included.

hep-ph↗

arXiv2001

SU(3) Symmetry Breaking and Polarized Parton Densities

We analyze the semileptonic weak decays of the octet baryons in a "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.

hep-ph↗

arXiv2001

Pion light cone wave function in the non-local NJL model

We use the simple instanton motivated NJL-type model to calculate the leading twist pion light cone wave function. The model consists in employing the momentum dependent quark mass in the quark loop entering the definition of the wave function. The result is analytical up to a solution of a certain algebraic equation. Various properties including the kT dependence of the pion wave function are discussed. The resulting kT integrated wave function is not asymptotic and is in agreement with recent analysis of the CLEO data.

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arXiv2001

Skyrme model and nonleptonic hyperon decays

This report is an attempt to explain both s- and p-wave nonleptonic hyperon decays by means of the QCD enhanced effective weak Hamiltonian supplemented by the SU(3) Skyrme model used to estimate nonperturbative matrix elements. The model has only one free parameter, namely, the Skyrme charge $e$, which is fixed through the experimental values of the octet-decuplet mass splitting $Δ$ and the axial coupling constant $g_{A}$. Such a dynamical approach produces nonleptonic hyperon decay amplitudes that agree with experimental data reasonably well.

hep-ph↗

arXiv1998

Symmetry conserving approach to the quantization of the non-topological SU(3) soliton

We reconsider canonical quantization of the rotating soliton in the SU(3) Chiral Quark-Soliton Model. We show that at the level of 1/N_c, in contrast to the SU(2) version of the model, there appear terms which spoil the commutation rules of the flavor generators. Terms of similar origin are also present in the expressions for axial couplings and magnetic moments. We investigate the small soliton limit of the model, and require that the results for the physical observables reduce to the ones of the non-relativistic quark model. This procedure allows to identify the troublesome terms. Next, we introduce a symmetry conserving approach by subtracting these terms and discuss numerical predictions obtained that way.

hep-ph↗

arXiv1997

Problems with proton in the QCD dipole picture

The soft gluon part of a proton wave function is investigated and compared with an onium case. It is argued that at every step of the gluon cascade new color structures appear. Dipole equation kernel emerges when a diquark limit is assumed.

hep-ph↗

arXiv1995

The Constituent Quark Limit and the Skyrmion Limit of the Chiral Quark Soliton Model

We calculate $g_A^3$ and $g_A^0$ in the Chiral Quark-Soliton Model (or equivalently in semibosonized Nambu--Jona-Lasinio model) in the limit of small and large soliton size. In small soliton limit we recover the results of the Constituent Quark Model. The agreement between the two models is achieved due to the recently calculated $1/\Nc$ contributions to $g_A^3$ and to $g_A^0$. In the case of $g_A^3$ these terms arise from the {\it time-ordering} of the collective operators. For large solitons simple scaling arguments show that the $1/\Nc$ contributions vanish with the inverse power of the soliton size.

hep-ph↗

arXiv1994

Isospin Mass Splittings and the $\ms$ Corrections in the Semibosonized SU(3)-NJL-Model

The mass splittings of hyperons including the isospin splittings are calculated with $O(\ms^2)$ and $O(\ms \dm)$ accuracy respectively within the semibosonized SU(3)-NJL model. The pattern of the isospin splittings is not spoiled by the terms of the order $O(\ms \dm)$, and both splittings between the different isospin multiplets and within the same multiplet are well reproduced for acceptable values of $\ms$ and $\dm$.

hep-ph↗

arXiv1994

Hyperon in Chiral Effective Quark Models

Baryonic correlation functions are calculated within an effective chiral quark model motivated by the instanton liquid model of QCD. Using a flavour SU(3) symmetry for the local four-quark interaction and taking rotational zero modes for the quantization into account low-energy hadronic observables are in surprising agreement with experimental data. (Talk presented at the Conference on Hypernuclear and Strange Particle Physics (HYP94), Vancouver, B.C., Canada, 4.-8- Juli 1994)

hep-ph↗

arXiv1994

Axial Properties of the Nucleon with $1/N_c$-Corrections in the solitonic SU(3)-NJL-Model

Within the semibosonized SU(3)-NJL model the mass splittings of baryons and the axial vector coupling constants of the nucleon are evaluated. The mass splittings of the hyperons are reproduced with great accuracy if second order corrections in $m_s$ are taken into account. New corrections to the axial vector currents coming from the subleading terms in the $1/N_c$ expansion are shown to be non-vanishing and substantially improving the phenomenological predictions for axial quantities. Finally the numerical values for the $g_{\rm A}$'s are $g_A^{(0)}=0.37$, $g_A^{(3)}=1.38$ and $g_A^{(8)}=0.31$ reproducing reasonably well the recent data from lepton scattering.

hep-ph↗

arXiv1993

Rotational Corrections to Axial Currents in Semibosonized SU(3) Nambu--Jona-Lasinio Model

We examine $O(1/\Ne)$ rotational corrections to axial couplings \gt~ and \go~ in the framework of the semibosonized SU(3) Nambu--Jona-Lasinio model. A novelty is due to the observation that the rotational (cranking) velocity and the rotation matrix itself do not commute within semiclassical quantization scheme. If time ordering in the quark loop is maintained new contributions, which have no analogue in the Skyrme model, appear. They substantially improve numerical results for the axial couplings which without the present corrections are badly underestimated.

hep-ph↗

arXiv1992

Strangeness in the Skyrme and in Nambu-Jona Lasinio Models

We discuss the phenomenology of SU(3) Skyrme and Nambu--Jona-Lasinio models. We show that while the Skyrme model, in its simplest version, is unable do reproduce the hyperon spectrum, the NJL model describes both hyperon and isospin splittings with satisfactory accuracy. The difference between the two models lies in new {\em anomalous} moments of inertia, which vanish in the Skyrme model and get non-zero contribution from the {\em valence} quarks in the NJL model

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