arXiv subjects

Igor I. Strakovsky

Publications and source records attributed to Igor I. Strakovsky.

At least 19 recordsLinked to original sources

arXiv2026

JLab and J-PARC for the J/{\ensuremathψ} Production at the Threshold

New threshold measurements for $γ~p\to p~J/ψ\to p~(μ^+μ^-)$ by 007 and $γ^\ast~p\to p~J/ψ\to p~(e^+e^-)$ by CLAS12 allow us to extend the previous phenomenological determination of the J/\ensuremathψ-proton scattering length, $α_{J/ψp}$, using GlueX threshold data for $γ~p\to p~J/ψ\to p~(e^+e^-)$. The agreement between all three J/\ensuremathψ data sets shows no indication of systematic differences between methodologies. Furthermore, perturbative QCD predictions support the phenomenological determination of heavy vector meson-nucleon scattering lengths. The role of the nucleon form factor, $F_N$, is discussed, and a possible correction to the phenomenological scattering length for heavy vector meson photoproduction is calculated using the pole form of $F_N$. Upcoming J-PARC threshold measurements of the reaction $π^-~p\to n~J/ψ\to n~(l^+l^-)$ will help to evaluate the possible role of heavy pentaquark, $P_c$, states in low-energy $J/ψ$ production and the effects caused by the nucleon form factors.

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arXiv2026

Amplitude-Based Analysis of QED Radiative Corrections to Electroproduction of $η$-Mesons on Protons

A formalism for radiative correction calculations in exclusive $η$ electroproduction on the proton is presented, extending the treatment developed for the pion channel. The EXCLURAD code is used in the radiative correction procedure with EtaMAID-2023 multipole amplitudes. The cross-section correction factor $δ$ varies by up to ${\sim}\,30\%$ across the resonance region $W = 1.49$-$2.0$ GeV at $E_{\rm beam} = 6.535$ GeV, with a local maximum near $W \simeq 1.66$ GeV driven by the $S_{11}(1535)$ and $S_{11}(1650)$ resonances. The beam-spin asymmetry is suppressed by 15-25% at the same kinematics. Numerical results covering $Q^2 = 0.3$-$4.0$ GeV$^2$ and the full angular range are provided for kinematics relevant to CLAS12 experiments at Jefferson Lab.

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arXiv2025

$J/ψ$-Meson Nucleon Scattering Length from Threshold Photoproduction on Light Nuclei

The quality of recent SRC/CT Collaboration $J/ψ$ photoproduction data off a $^4$He target from Hall~D at Jefferson Laboratory, combined with the feasibility of measuring the reaction close to the free-nucleon energy threshold, opens the door to using incoherent $J/ψ$ photoproduction to access a variety of interesting physics aspects. An example is an estimate of the $J/ψ~p$ scattering length $|α_{J/ψ~p}|$ on the bound proton obtained using the Vector Meson Dominance model. This value can be compared with that of the free proton from the GlueX Collaboration. One may then project what would be expected from the SRC/CT Collaboration Experiment E12--25--002, which was recently approved by the JLab PAC. Using a plane-wave theoretical model to generate quasi-data, we find the experiment could achieve a result of $|α_{J/ψ~p}| = 3.08\pm 0.45~\mathrm{mfm}$, an uncertainty competitive with that of the free-proton measurement. A comparison between the two would allow an evaluation of the effects of medium modification in the case of light nuclei.

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arXiv2025

rho-Meson Nucleon Scattering Length from CLAS Threshold Photoproduction Measurements

Extending our study of the vector meson-nucleon scattering lengths (summary is given in Ref.~\cite{Strakovsky:2021vyk}), we are focusing on the $ρ$-meson case using recent CLAS threshold data for the reaction $γp \to ρp$ within the meson-baryon reaction model~\cite{CLAS:2018drk}. The total $σ_t(γp\to ρp)$ and $σ_t(γp\to ωp)$ cross sections are close below the momentum of the vector meson in CM $q = 0.2~\mathrm{GeV/c}$. Then the $ρp$ photoproduction cross section grows rapidly. Our result for $ρN$ scattering length is a factor of 4 smaller than the size of the hadron and the phenomenological determination of the $ω$ nucleon scattering length using threshold photoproduction cross sections. The observed difference between $ρN$ and $ωN$ scattering lengths is of interest for further understanding within the hadron structure theory.

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arXiv2024

Search for {Θ^+} in KLp \to K+n reaction in KLF at JLab

The possibility of the existence of multiquark hadrons made of 4-quark for mesons and 5-quark for baryons was predicted by Gell-Mann in Ref. [1]. The renewed interest for the search of exotic pentaquark states was initiated by the paper by Diakonov, Petrov, and Polyakov in Ref. [2]. The 2003 experimental reports on the observation of {Θ^+} pentaquark with a uudd{\bar s} quark content created a big excitement and many following experiments have reported its observation [3]. After high-statistics experiments at JLab, which did not confirm previous claims by the CLAS collaboration, the community concluded that the {Θ^+} pentaquark either does not exist at all or has an extremely small cross section, making it currently unobserved. There were different review papers on this subject, either questioning the existence of the {Θ^+} or attempting to explain the reasons why reaching a conclusion based on production experiments is challenging [4]. To address the challenge of minimal 3-body final states, a formation experiment with a projectile kaon beam is proposed. Below, we discuss how the {Θ^+} could be observed in the KLp \to {Θ^+} \to {K^+}n reaction in the KLF experiment at JLab [5].

hep-ex↗

arXiv2023

New Experimental Opportunities in Spin-Physics for Meson Beams

During the past several decades a large quantity of high-quality mesonic photo- and electro- production data have been measured at electromagnetic facilities worldwide. By contrast, meson-beam data for these same final states are mostly outdated, largely of poorer quality, or even non-existent, especially those involving spin asymmetries and polarizations. Thus existing meson beam results provide inadequate input to interpret, analyze, and exploit the potential of the new electromagnetic data. To achieve full benefit of these high-precision electromagnetic data, new high-statistics data from measurements with meson beams, with good angle and energy coverage for a wide range of reactions, are critically needed to advance our knowledge in baryon and meson spectroscopy and other related areas of hadron physics. To address this situation, new, state-of-the-art meson-beam facilities are needed. This presentation summarizes unresolved issues in hadron physics and outlines the opportunities and advances that are possible with such facilities.

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arXiv2022

Pseudoscalar and Scalar Meson Photoproduction Interpreted by Regge Phenomenology

We have evaluated pseudoscalar and scalar neutral pion photoproduction in $\vecγp\toπ^0p$ and $\vecγp\to a_0^0p$ above the resonance region and within Regge phenomenology. Our fit, including GlueX $Σ$ pseudoscalar photoproduction data, shows that previous SLAC $Σ$ measurements for $\vecγp \to π^0p$ above $E_γ= 4~\mathrm{GeV}$ are at variance with SLAC data with more recent measurements made by GlueX in vicinity of $E_γ= 9~\mathrm{GeV}$. The Regge model predicts that the beam polarization asymmetry $Σ$ of the scalar meson is opposite to that of pseudoscalar meson photoproduction, however, the cross sections are similar. While the vector natural parity meson exchange is dominant in both cases, the contribution of the pseudovector unnatural parity meson exchange is very small. Using Regge phenomenology, we predicted high energy behavior for double polarized observables $\mathbb{E}$, $\mathbb{F}$, $\mathbb{G}$, and $\mathbb{H}$ for the reactions $γp\to π^0p$ and $γp\to a_0^0p$.

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arXiv2022

The $ψ^{(\ast)}p$ scattering length based on near-threshold charmoniums photoproduction

Under the framework of Vector Meson Dominance model, the value of scattering length can be expressed as a function of the ratio between total cross section $σ(W)$ and $R (W)$, where $R(W)$ is the ratio between final momentum $|{\bf p}_3 |$ and initial momentum $|{\bf p}_1|$ and positively correlated with the center-of-mass energy. Based on the theoretical study of charmoniums photoproduction within two gluon exchange model and effective pomeron model, we research the scattering lengths of vector mesons and proton interaction in this work. Results show that the scattering length $\left|α_{J/ψp}\right|$ obtained from the two models are close and basically in agreement with the theoretical prediction of Strakovsky and co-workers. Additionally, we first calculate the scattering length of $ψ(2S) $-proton interaction in two gluon exchange model and effective pomeron model as $ 1.31\pm 0.92$ am (1 am = $10^{-3}$ fm) and $ 3.24 \pm 0.63$ am, respectively. This is a little bit different from the two models and requires precise measurements from subsequent experiments. In short, our results will provide a theoretical reference for future studies on characterizing the vector meson-proton scattering length.

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arXiv2021

On the Photoproduction Reactions $γd\toπNN$

A review of our works providing a theoretical description of incoherent pion photoproduction on the deuteron is presented. The existing $γd\toπNN$ data are analysed, especially those obtained more recently by the CLAS Collaboration at JLab, the A2 Collaboration at MAMI at Mainz, and the PION@MAX-lab Collaboration at Lund. A procedure, which accounts for the final state interactions (FSI), is applied to extract $γn\toπN$ differential cross sections from the deuteron data. The role of FSI is discussed. We also comment on the results of other works in connection with some discrepancies seen in comparing the model with experiment. The electromagnetic properties of baryon $N^\ast$ resonances, improved using the extracted $γn\toπN$ differential cross sections, are presented. A model description of the cross section data from charged-pion photoproduction reactions $γd\toπ^{\pm}NN$ near threshold is also given. The $γd\toπ^-pp$ data are used to extract the $E_{0+}$ multipole and total crsoss sections of the reaction $γn\toπ^-p$ near threshold.

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arXiv2021

Threshold Upsilon-meson Photoproduction at EIC and EicC

High-accuracy $Υ$-meson photoproduction data from EIC and EicC experiments will allow the measurement of the near-threshold total cross section of the reaction $γp\toΥp$, from which the absolute value of the $Υp$ scattering length, $|α_{Υp}|$, can be extracted using a Vector-Meson Dominance model. For this evaluation, we used $Υ$-meson photoproduction quasi-data from the QCD approach (the production amplitude can be factorized in terms of gluonic generalized parton distributions and the quarkonium distribution amplitude). A comparative analysis of $|α_{Υp}|$ with the recently determined scattering lengths for $ωp$, $ϕp$, and $J/ψp$ using the A2, CLAS, and GlueX experimental data are performed. The role of the "young" vector-meson effect is evaluated.

hep-ph↗

arXiv2021

High Energy Behaviour of Light Meson Photoproduction

We evaluated recent CLAS Collaboration measurements for the $90^\circ$ meson photoproduction off the nucleon using a tagged photon beam spanning the energy interval $s = 3 - 11$ GeV$^2$. The results are compared with the "Quark Counting Rules" predictions.

hep-ph↗

arXiv2021

$J/ψ$-$p$ Scattering Length from the Total and Differential Photoproduction Cross Sections

The $J/ψ$-$p$ scattering length, $α_{J/ψp}$, can be extracted from the $J/ψ$ photoproduction cross section near threshold using the Vector Meson Dominance (VMD) model to relate the reaction $γp \to J/ψp$ to $J/ψp \to J/ψp$. Such estimates based on experimental data result in values for $|α_{J/ψp}|$, which are much lower than most of the theoretical predictions. In this work, we study the relations between the different results, depending on the use of the total or the differential cross sections, and the method of extrapolating the data to threshold in the case of a low-statistics data sample, such as the near threshold $J/ψ$ photoproduction dataset. We estimate a range for $|α_{J/ψp}|$ of $0.003$ to $0.025$~fm as extracted from experimental data within the VMD model and discuss possible reasons for such lower values compared to the theoretical results.

hep-ph↗

arXiv2016

Legendre Analysis of Differential Distributions in Hadronic Reactions

Modern experimental facilities, such as CBELSA, ELPH, JLab, MAMI and SPring-8 have provided a tremendous volume of data, often with wide energy and angular coverage, and with increasing precision. For reactions with two hadrons in the final state, these data are often presented as multiple sets of panels, with angular distributions at numerous specific energies. Such presentations have limited visual appeal, and their physical content is typically extracted through some model- dependent treatment. Instead, we explore the use of a Legendre series expansion with a relatively small number of essential coefficients. This approach has been applied in several recent experimental investigations. We present some general properties of the Legendre coefficients in the helicity framework and consider what physical information can be extracted without any model-dependent assumptions.

hep-ph↗

arXiv2016

Partial-Wave Analysis of Nucleon-Nucleon Elastic Scattering Data

Energy-dependent and single-energy fits to the existing nucleon-nucleon database have been updated to incorporate recent measurements. The fits cover a region from threshold to 3 GeV, in the laboratory kinetic energy, for proton-proton scattering, with an upper limit of 1.3 GeV for neutron-proton scattering. Experiments carried out at the COSY-WASA and COSY-ANKE facilities have had a significant impact on the partial-wave solutions. Results are discussed in terms of both partial-wave and direct reconstruction amplitudes.

nucl-th↗

arXiv2016

K-Long Facility for JLab and its Scientific Potential

Our main interest in creating a secondary high-quality KL-beam is to investigate hyperon spectroscopy through both formation and production processes. We propose to study two-body reactions induced by the KL-beam on the proton target. The experiment should measure both differential cross sections and self-analyzed polarizations of the produced $Λ$-, $Σ$-, and $Ξ$-hyperons using the GlueX detector at the Jefferson Lab Hall D. New data will greatly constrain partial-wave analysis and reduce model-dependent uncertainties in the extraction of strange resonance properties, providing a new benchmark for comparisons with QCD-inspired models and LQCD calculations. The measurements will span c.m. $\cosθ$ from -0.95 to 0.95 in c.m. range above W = 1490MeV and up to 4000 MeV.

nucl-ex↗

arXiv2015

Physics Opportunities with Meson Beams

Over the past two decades, meson photo- and electro-production data of unprecedented quality and quantity have been measured at electromagnetic facilities worldwide. By contrast, the meson-beam data for the same hadronic final states are mostly outdated and largely of poor quality, or even nonexistent, and thus provide inadequate input to help interpret, analyze, and exploit the full potential of the new electromagnetic data. To reap the full benefit of the high-precision electromagnetic data, new high-statistics data from measurements with meson beams, with good angle and energy coverage for a wide range of reactions, are critically needed to advance our knowledge in baryon and meson spectroscopy and other related areas of hadron physics. To address this situation, a state of-the-art meson-beam facility needs to be constructed. The present paper summarizes unresolved issues in hadron physics and outlines the vast opportunities and advances that only become possible with such a facility.

hep-ph↗

arXiv2015

Radiative Decay Width of Neutral non-Strange Baryons from PWA

An overview of the GW SAID and ITEP groups effort to analyze pion photoproduction on the neutron-target will be given. The disentanglement the isoscalar and isovector EM couplings of N* and Delta* resonances does require compatible data on both proton and neutron targets. The final-state interaction plays a critical role in the state-of-the-art analysis in extraction of the gamma n --> pi N data from the deuteron target experiments. It is important component of the current JLab, MAMI-C, SPring-8, ELSA, and ELPH programs

nucl-th↗

arXiv2012

Unified Chew-Mandelstam SAID analysis of pion photoproduction data

A unified description of single-pion photoproduction data, together with pion- and eta-hadroproduction data, has been achieved in a Chew-Mandelstam parametrization which is consistent with unitarity at the two-body level. Energy-dependent and single-energy partial wave analyses of pion photoproduction data have been performed and compared to previous SAID fits and multipoles from the Mainz and Bonn-Gatchina groups.

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