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P. Bydžovský

Publications and source records attributed to P. Bydžovský.

14 recordsLinked to original sources
arXiv2025

Backward-angle electroproduction of $η'$ mesons off protons at $W=2.13~\text{GeV}$ and $Q^{2}=0.46~\left(\text{GeV}/c\right)^{2}$

The electroproduction of $η'$ mesons from a $\mathrm{^{1}H}$ target at $W=2.13~\text{GeV}$, $Q^{2} = 0.46~\left( \text{GeV}/c\right)^{2}$ and $\cos θ^{\text{CM}}_{γ^{*}η'} \approx -1$ has been experimentally measured. The differential cross section of virtual-photoproduction has been obtained as $4.4 \pm 0.8 ~\left( \text{stat.} \right) \pm 0.4 ~\left( \text{sys.} \right)~ \text{nb/sr}$ in the One-Photon-Exchange Approximation. This value is one-sixth of that of real-photoproduction at backward angles. A comparison with newly-developed isobar model calculations not only shows validity of the theoretical framewark employed, but also imposes new constrains on coupling strength between the $η'p$ final state and nucleon resonances.

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arXiv2025

Electroproduction of medium- and heavy-mass hypernuclei

The DWIA formalism for computing the cross sections in electroproduction of hypernuclei used before for lighter (p-shell and sd-shell) systems is utilized in studying electroproduction on heavier targets such as $^{52}$Cr, and $^{208}$Pb. First, the effects from kaon distortion and kinematics are re-examined and then results for the heavy targets are discussed in view of various forms of the $Λ$N effective interaction, the elementary amplitude, and kinematics. Apparent sensitivity of the hypernucleus excitation spectra to various forms of the $Λ$N effective interaction is shown. Predictions of the excitation spectrum in electroproduction of $^{208}_{~~Λ}$Tl are also given in kinematics of the experiment E12-20-013 in preparation at Jefferson Lab.

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arXiv2024

Electroproduction of the Lambda/Sigma^0 hyperons at Q^2~0.5 (GeV/c)^2 at forward angles

In 2018, the E12-17-003 experiment was conducted at the Thomas Jefferson National Accelerator Facility (JLab) to explore the possible existence of an nnLambda state in the reconstructed missing mass distribution from a tritium gas target [K. N. Suzuki et al., Prog. Theor. Exp. Phys. 2022, 013D01 (2022), B. Pandey et al., Phys. Rev. C 105, L051001 (2022)]. As part of this investigation, data was also collected using a gaseous hydrogen target, not only for a precise absolute mass scale calibration but also for the study of Lambda/Sigma^0 electroproduction. This dataset was acquired at Q^2~0.5 (GeV/c)^2, W=2.14 GeV, and theta_{gamma K}^{c.m.}~8 deg. It covers forward angles where photoproduction data is scarce and a low-Q^2 region that is of interest for hypernuclear experiments. On the other hand, this kinematic region is at a slightly higher Q^2 than previous hypernuclear experiments, thus providing crucial information for understanding the Q^2 dependence of the differential cross sections for Lambda/Sigma^0 hyperon electroproduction. This paper reports on the Q^2 dependence of the differential cross section for the e + p -> e' + K^+ + Lambda/Sigma^0 reaction in the 0.2-0.8 (GeV/c)^2, and provides comparisons with the currently available theoretical models.

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arXiv2023

Self-consistent many-body approach to the electroproduction of hypernuclei

The electroproduction of selected $p$- and $sd$-shell hypernuclei was studied within a many-body approach using realistic interactions between the constituent baryons. The cross sections were computed in distorted-wave impulse approximation using two elementary amplitudes for the electroproduction of the $Λ$ hyperon. The structure of the hypernuclei was investigated within the framework of the self-consistent $Λ$-nucleon Tamm-Dancoff approach and its extension known as the $Λ$-nucleon equation of motion phonon method. Use was made of the NNLOsat chiral potential plus the effective Nijmegen-F YN interaction. The method was first implemented on light nuclei for studying the available experimental data and establishing a relation to other approaches. After this proof test, it was adopted for predicting the electroproduction cross section of the hypernuclei $^{40}_{~Λ}$K and $^{48}_{~Λ}$K in view of the E12-15-008 experiment in preparation at JLab. On the ground of these predictions, appreciable effects on the spectra are expected to be induced by the YN interaction.

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arXiv2022

Fermi motion effects in electroproduction of hypernuclei

In a previous analysis of electroproduction of hypernuclei the cross sections were calculated in distorted-wave impulse approximation where the momentum of the initial proton in the nucleus was set to zero (the frozen-proton approximation). In this paper we go beyond this approximation assuming a non zero effective proton momentum due to proton Fermi motion inside of the target nucleus discussing also other kinematical effects. To this end we have derived a more general form of the two-component elementary electroproduction amplitude (Chew-Goldberger-Low-Nambu like) which allows its use in a general reference frame moving with respect to the nucleus-rest frame. The effects of Fermi motion were found to depend on kinematics and elementary amplitudes. The largest effects were observed in the contributions from the longitudinal and interference parts of the cross sections. The extension of the calculations beyond the frozen-proton approximation improved the agreement of predicted theoretical cross sections with experimental data and once we assumed the optimum on-shell approximation, we were able to remove an inconsistency which was previously present in the calculations.

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arXiv2019

Meson resonances in forward-angle $π^+π^-$ photoproduction

Assuming that the $π^+π^-$ photoproduction at forward angles and high energies is dominated by one pion exchange we calculate the $π^+π^-$ mass distributions for low partial waves. Predictions of the model agree well Assuming that the $π^+π^-$ photoproduction at forward angles and high energies is dominated by one pion exchange we calculate the $π^+π^-$ mass distributions for low partial waves. Predictions of the model agree well with the experimental data which indicate that the $S$, $P$ and $D$ waves are dominated by the $f_0(980)$, $ρ(770)$ and $f_2(1270)$, resonances respectively.

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arXiv2018

Photo- and electroproduction of $K^{+}Λ$ with unitarity-restored isobar model

Exploiting the isobar model, kaon photo- and electroproduction on the proton in the resonance region comes under scrutiny. An upgrade of our previous model, comprising higher-spin nucleon and hyperon exchanges in the consistent formalism, was accomplished by implementing energy-dependent widths of nucleon resonances, which leads to a different choice of hadron form factor with much softer values of cutoff parameter for the resonant part. For a reliable description of electroproduction, the necessity of including longitudinal couplings of nucleon resonances to virtual photons was revealed. We present a new model whose free parameters were adjusted to photo- and electroproduction data and which provides a reliable overall description of experimental data in all kinematic regions. The majority of nucleon resonances chosen in this analysis coincide with those selected in our previous analysis and also in the Bayesian analysis with the Regge-plus-resonance model as the states contributing to this process with the highest probability.

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arXiv2016

Dispersive analysis of the $S$-, $P$-, $D$-, and $F$-wave $ππ$ amplitudes

A reanalysis of $ππ$ amplitudes for all important partial-waves below about 2 GeV is presented. A set of once subtracted dispersion relations with imposed crossing symmetry condition is used to modify unitary multi-channel amplitudes in the $S$, $P$, $D$, and $F$ waves. So far, these specific amplitudes constructed in our works and many other analyzes have been fitted only to experimental data and therefore do not fulfill the crossing symmetry condition. In the present analysis, the self consistent, i.e. unitary and fulfilling the crossing symmetry, amplitudes for the $S$, $P$, $D$, and $F$ waves are formed. The proposed very effective and simple method of modification of the $ππ$ amplitudes does not change their previous-original mathematical structure and the method can be easily applied in various other analyzes.

hep-ph↗
arXiv2016

Effect of the $ηη$ channel and interference phenomena in the two-pion transitions of charmonia and bottomonia

The basic shape of di-pion mass spectra in the two-pion transitions of both charmonia and bottomonia states is explained by an unified mechanism based on contributions of the $ππ$, $K\overline{K}$ and $ηη$ coupled channels including their interference. The role of the individual $f_0$ resonances in shaping the di-pion mass distributions in the charmonia and bottomonia decays is considered.

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arXiv2015

Effect of coupled channels of the multi-channel pion-pion scattering in two-pion transitions of the $Υ$ mesons

The effect of isoscalar S-wave processes $ππ\toππ,K\overline{K},ηη$ is considered in the analysis of data (from the ARGUS, CLEO, CUSB, Crystal Ball, Belle, BABAR collaborations) on the bottomonia decays --- $Υ(mS)\toΥ(nS)ππ$ ($m>n, m=2,3,4,5, n=1,2,3$). It is shown that the dipion mass spectra of these decays are explained by the unified mechanism related to the contribution of the multichannel $ππ$ scattering in the final states of these reactions. Since in the analysis the multichannel $ππ$-scattering amplitudes did not change in comparison with the ones in our combined analysis of data on the multichannel $ππ$ scattering and on the charmonia decays --- $J/ψ\toϕ(ππ, K\overline{K})$ and $ψ(2S)\to J/ψ(ππ)$ (from the Crystal Ball, DM2, Mark II, Mark III, and BES II) --- the results confirm all our earlier conclusions on the scalar mesons.

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arXiv2014

Modified $ππ$ amplitude with $σ$ pole

A set of well known once subtracted dispersion relations with imposed crossing symmetry condition is used to modify unitary multichannel $S$ ($ππ$, $K \bar K$, and $ηη$) and $P$ ($ππ$, $ρ2π$, and $ρσ$) wave amplitudes mostly below 1 GeV. Before the modifications, these amplitudes significantly did not satisfy the crossing symmetry condition and did not describe the $ππ$ threshold region. Moreover, the pole of the $S$ wave amplitude related with the $f_0(500)$ meson (former $f_0(600)$ or $σ$) had much smaller imaginary part and bigger real one in comparison with those in the newest Particle Data Group Tables. Here, these amplitudes are supplemented by near threshold expansion polynomials and refitted to the experimental data in the effective two pion mass from the threshold to 1.8 GeV and to the dispersion relations up to 1.1 GeV. In result the self consistent, i.e. unitary and fulfilling the crossing symmetry condition, $S$ and $P$ wave amplitudes are formed and the $σ$ pole becomes much narrower and lighter. To eliminate doubts about the uniqueness of the so obtained sigma pole position short and purely mathematical proof of the uniqueness of the results is also presented. This analysis is addressed to a wide group of physicists and aims at providing a very effective and easy method of modification of, many presently used, $ππ$ amplitudes with a heavy and broad $σ$ meson without changing of their original mathematical structure.

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arXiv2011

Exclusive electroproduction of K+ Lambda and K+ Sigma^0 final states at Q^2 = 0.030-0.055 (GeV/c)^2

Cross section measurements of the exclusive p(e,e'K+)Lambda,Sigma^0 electroproduction reactions have been performed at the Mainz Microtron MAMI in the A1 spectrometer facility using for the first time the Kaos spectrometer for kaon detection. These processes were studied in a kinematical region not covered by any previous experiment. The nucleon was probed in its third resonance region with virtual photons of low four-momenta, Q^2= 0.030-0.055 (GeV/c)^2. The MAMI data indicate a smooth transition in Q^2 from photoproduction to electroproduction cross sections. Comparison with predictions of effective Lagrangian models based on the isobar approach reveal that strong longitudinal couplings of the virtual photon to the N* resonances can be excluded from these models.

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arXiv2006

Photo-production of neutral kaons on 12C in the threshold region

Kaon photo-production process on $^{12}$C has been studied by measuring neutral kaons in a photon energy range of 0.8$-$1.1 GeV. Neutral kaons were identified by the invariant mass constructed from two charged pions emitted in the $K^{0}_{S}\toπ^{+}π^{-}$ decay channel. The differential cross sections as well as the integrated ones in the threshold photon energy region were obtained. The obtained momentum spectra were compared with a Spectator model calculation using elementary amplitudes of kaon photo-production given by recent isobar models. Present result provides, for the first time, the information on $n(γ,K^{0})Λ$ reaction which is expected to play an important role to construct models for strangeness production by the electromagnetic interaction. Experimental results show that cross section of $^{12}{\rm C}(γ,K^0)$ is of the same order to that of $^{12}{\rm C}(γ,K^+)$ and suggest that slightly backward $K^0$ angular distribution is favored in the $γn\to K^0Λ$ process.

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