arXiv subjects

T. Mart

Publications and source records attributed to T. Mart.

At least 19 recordsLinked to original sources

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.

nucl-ex↗

arXiv2023

Note on the electromagnetic radius of proton

We have analyzed the proton form factor data by using a number of phenomenological parameterizations (models) and extracting the proton electric and magnetic radii. To this end we performed a global fit to all available form factor data, with the virtual photon momentum squared $Q^2$ from $0.0002$ to nearly 10 GeV$^2$ for electric form factor and from $0.015$ to 31 GeV$^2$ for magnetic one. Special attention was given to the small structure shown by the form factor data near $Q^2 = 0.2$ GeV$^2$. It was found that different models yield different structures with different numbers of minimum at this kinematics. Since the slope of form factor in the limit of $Q^2\to 0$ is influenced by this structure, the extracted proton radii are consequently different for different models. Our finding recommends that future experiments should focus on this kinematics instead of low $Q^2$. Experimental data with accuracies comparable to those of the latest data at low $Q^2$ would clearly help to clarify the effect of this structure on the proton charge radius. Interestingly, most of the extracted proton charge radii were found to be closer to the value obtained from the muonic hydrogen atom spectroscopy.

hep-ph↗

arXiv2023

Inclusion of $K\Lambda$ electroproduction data in a coupled channel analysis

Exclusive electroproduction reactions provide an access to the structure of excited baryons. To extract electroproduction multipoles encoding this information, the J\"ulich-Bonn-Washington (JBW) analysis framework is extended to the analysis of differential cross sections in $K\Lambda$ electroproduction. This update enlarges the scope of previous coupled-channel analyses of pions and eta mesons, with photoproduction reactions as boundary condition in all analyzed electroproduction reactions. Polarization observables are predicted and compared to recent CLAS data. The comparison shows the relevance of these data to pin down baryon properties.

nucl-th↗

arXiv2021

Role of the high-spin nucleon and delta resonances in the $K\Lambda$ and $K\Sigma$ photoproduction off the nucleon

We have investigated the effect of nucleon and delta resonances with spins 11/2, 13/2, and 15/2 in the kaon photoproduction process $\gamma + N \to K + Y$ by using two covariant isobar models. The formalism for high-spin propagators and interaction Lagrangians were adopted from the works of Pascalutsa and Vrancx et al. The unknown parameters in the amplitudes, i.e., the coupling constants and hadronic form factor cutoffs, were obtained by fitting the calculated observables to experimental data. In the $K\Lambda$ channels the inclusion of $N(2600)I_{1,11}$ and $N(2700)K_{1,13}$ resonances improves the agreement between model calculations and experimental data significantly and reduces the dominance of resonances in the model by increasing the hadronic form factor cutoff of the Born terms. Furthermore, the inclusion of these resonances reduces the number of resonance structures in cross sections, including the structure in the $K^0\Lambda$ differential cross section at $W\approx 1650$ MeV, which could become a hint of the narrow resonance. In the $K\Sigma$ channels the inclusion of $N(2600)I_{1,11}$, $N(2700)K_{1,13}$, $\Delta(2420)H_{3,11}$, $\Delta(2750)I_{3,13}$, and $\Delta(2950)K_{3,15}$ states also significantly improves the model and increases the hadronic form factor cutoff of the Born terms. However, different from the $K\Lambda$ channels, the inclusion of these high-spin resonances leads to more resonance structures in the $K^+\Sigma^0$ differential cross section. This investigation reveals that the second and third peaks in the $K^+\Sigma^0$ differential cross section originate from the $\Delta(2000)F_{35}$ and $N(2290)G_{19}$ resonances, respectively. We have also evaluated the resonance properties at the pole positions and using the Breit-Wigner method.

hep-ph↗

arXiv2021

Extracting the pole and Breit-Wigner properties of nucleon and $\Delta$ resonances from the $\gamma N\to K\Sigma$ photoproduction

We have developed a covariant isobar model to phenomenologically explain the four possible isospin channels of $K\Sigma$ photoproduction. To obtain a consistent reaction amplitude, which is free from the lower-spin background problem, we used the consistent electromagnetic and hadronic interactions described in our previous report. We used all available experimental data, including the recent MAMI A2 2018 data obtained for the $K^0\Sigma^+$ and $K^0\Sigma^0$ isospin channels. By fitting the calculated observables to these data we extract the resonance properties, including their Breit-Wigner and pole parameters. Comparison of the extracted parameters with those listed by the Particle Data Group yields a nice agreement. An extensive comparison of the calculated observables with experimental data is also presented. By using the model we investigated the effects of three different form factors used in the hadronic vertex of each diagram. A brief discussion on the form factors is given.

hep-ph↗

arXiv2020

How do I introduce Schr\"odinger equation during the quantum mechanics course?

In this paper I explain how I usually introduce the Schr\"odinger equation during the quantum mechanics course. My preferred method is the chronological one. Since the Schr\"odinger equation belongs to a special case of wave equations I start the course with introducing the wave equation. The Schr\"odinger equation is derived with the help of the two quantum concepts introduced by Max Planck, Einstein, and de Broglie, i.e., the energy of a photon $E=\hbar\omega$ and the wavelength of the de Broglie wave $\lambda=h/p$. Finally, the difference between the classical wave equation and the quantum Schr\"odinger one is explained in order to help the students to grasp the meaning of quantum wavefunction $\Psi({\bf r},t)$. A comparison of the present method to the approaches given by the authors of quantum mechanics textbooks as well as that of the original Nuffield A level is presented. It is found that the present approach is different from those given by these authors, except by Weinberg or Dicke and Wittke. However, the approach is in line with the original Nuffield A level one.

physics.ed-ph↗

arXiv2019

Pure spin-3/2 representation with consistent interactions

We have investigated the use of pure spin-3/2 propagator with consistent interaction Lagrangians to describe the property of spin-3/2 resonance. For this purpose we use the antisymmetric tensor spinor representation. By using the primary and secondary constraints we obtain the interaction fields that have the correct degrees of freedom. To visualize the result we calculate the contribution of spin-3/2 $Δ$ resonance to the total cross section of pion scattering and pion photoproduction off the nucleon. The result confirms that the scattering and photoproduction amplitudes obtained from the pure spin-3/2 representation with consistent interaction Lagrangians exhibit the required property of a resonance. Therefore, the formalism can be used for phenomenological investigations in the realm of nuclear and particle physics.

nucl-th↗

arXiv2019

Coupled $K^+Λ$ and $K^0Λ$ photoproduction off the nucleon: Consequences from the recent CLAS and MAMI data and the $N(1680)P_{11}$ narrow state

The new $γn\to K^0Λ$ data obtained from the CLAS and MAMI collaborations are analyzed by employing an effective Lagrangian method. The constructed model can describe all available experimental data in both $γp \to K^+Λ$ and $γn\to K^0Λ$ channels, simultaneously. The background part of the model is built from the appropriate intermediate states involving the nucleon, kaon, and hyperon exchanges, whereas the resonance part is constructed from the consistent interaction Lagrangians and propagators. To check the performance of the model a detailed comparison between the calculated observables and experimental data in both isospin channels is presented, from which a nice agreement can be observed. The discrepancy between the CLAS and MAMI data in the $γn\to K^0Λ$ channel is analyzed by utilizing three different models; M1, M2, and M3 that fit the CLAS, MAMI, and both CLAS and MAMI data sets, respectively. The effect of this discrepancy is studied by investigating the significance of individual nucleon resonances and the predicted beam-target helicity asymmetry $E$ that has been measured by the CLAS collaboration recently. It is found that the $N(1720)P_{13}$, $N(1900)P_{13}$, and $N(2060)D_{15}$ resonances are significant for improving the agreement between model calculation and data. This result is relatively stable to the choice of the model. The helicity asymmetry $E$ can be better explained by the models M1 and M3. Finally, the effect of the $N(1680)P_{11}$ narrow resonance on the cross section of both isospin channels is explored. It is found that the effect is more sensitive in the $γn\to K^0Λ$ channel. In this case the model M3, that fits both CLAS and MAMI data, yields a more realistic effect.

hep-ph↗

arXiv2019

Some Phenomenological Aspects of Kaon Photoproduction in the Extreme Kinematics

We have investigated phenomenological aspects of kaon photoproduction in three different extreme kinematics. The first kinematics of interest is the threshold region. At the threshold we have investigated the convergence of kaon photoproduction amplitude by expanding the square of the amplitude in terms of the ratio $m_K/m$, where $m_K$ is the mass of kaon and $m$ is the averaged mass of nucleon and $Λ$-hyperon. The amplitude is calculated from the appropriate Feynman diagrams by using the pseudovector theory. The contact diagram as a consequence of the PCAC hypothesis is also taken into account in the amplitude. Our finding indicates that the convergence can be only achieved if the amplitude was expanded up to at least $12^{\rm th}$ order. As a consequence, applications of some theoretical calculations based on the expansion the scattering amplitude, such as the Low Energy Theorem or Soft Kaon Approximation, cannot be easily managed in kaon photoproduction. The second kinematics is the forward region, where we could assume only $t$-channel contributes to the process. Here we have investigated the effect of amplitude expansion on the extraction of the coupling constants $g_{K^+Λp}$ and $g^V_{K_1^+Λp}$. The last kinematics is the backward region, where we have also assumed that only $u$-channel survives and we could extract the leading coupling constants $g_{K^+Λp} $ and $g_{K^+Σ^0 p}$.

hep-ph↗

arXiv2017

Pure spin-3/2 propagator for use in particle and nuclear physics

We propose the use of pure spin-3/2 propagator in the $(3/2,0) \oplus (0,3/2)$ representation in particle and nuclear physics. To formulate the propagator in a covariant form we use the antisymmetric tensor spinor representation and we consider the $Δ$ resonance contribution to the elastic $πN$ scattering as an example. We find that the use of conventional gauge invariant interaction Lagrangian leads to a problem; the obtained scattering amplitude does not exhibit the resonance behavior. To overcome this problem we modify the interaction by adding a momentum dependence. As in the case of Rarita-Schwinger we find that a perfect resonance description could be obtained in the pure spin-3/2 formulation only if hadronic form factors were considered in the interactions.

nucl-th↗

arXiv2017

Imprint of Nucleon Radius on the Slowly Rotating Neutron Star Properties

We have studied the effect of free space nucleon radius on the nuclear matter and slowly rotating neutron star properties within a relativistic mean field model with the inclusion of omega-rho mixing nonlinear term. We use the same density dependent radius as in our previous work. However, in the present work we utilize the parameter sets with more proper symmetric nuclear matter (SNM) predictions for a number of different nucleon radii. To this end, the isoscalar parameters in each parameter set and the cutoff parameter $β$ are adjusted by fitting the corresponding SNM properties at sub-saturation density to the prediction of IUFSU parameter set. We have obtained that the assumption of composite nucleons with free space radius $r \le 0.83$ fm is still compatible with the currently acceptable nuclear matter (NM) properties beyond the saturation density. We have also found that the effect of free space nucleon radius could be imprinted in the radius, moment of inertia, and crust properties of the slowly rotating neutron star.

nucl-th↗

arXiv2016

Extraction of the proton charge radius from experiments

Static properties of hadrons such as their radii and other moments of the electric and magnetic distributions can only be extracted using theoretical methods and not directly measured from experiments. As a result, discrepancies between the extracted values from different precision measurements can exist. The proton charge radius, $r_p$, which is either extracted from electron proton elastic scattering data or from hydrogen atom spectroscopy seems to be no exception. The value $r_p = 0.84087(39)$ fm extracted from muonic hydrogen spectroscopy is about 4% smaller than that obtained from electron proton scattering or standard hydrogen spectroscopy. The resolution of this so called proton radius puzzle has been attempted in many different ways over the past six years. The present article reviews these attempts with a focus on the methods of extracting the radius.

hep-ph↗

arXiv2015

Viscosities of Gluon Dominated QGP Model within Relativistic Non-Abelian Hydrodynamics

Based on the first principle calculation, a Lagrangian for the system describing quarks, gluons, and their interactions, is constructed. Ascribed to the existence of dissipative behavior as a consequence of strong interaction within quark-gluon plasma (QGP) matter, auxiliary terms describing viscosities are constituted into the Lagrangian. Through a "kind" of phase transition, gluon field is redefined as a scalar field with four-vector velocity inherently attached. Then, the Lagrangian is elaborated further to produce the energy-momentum tensor of dissipative fluid-like system and the equation of motion (EOM). By imposing the law of energy and momentum conservation, the values of shear and bulk viscosities are analytically calculated. Our result shows that, at the energy level close to hadronization, the bulk viscosity is bigger than shear viscosity. By making use of the conjectured values $η/ s \sim 1 / 4π$ and $ζ/ s \sim 1$, the ratio of bulk to shear viscosity is found to be $ζ/ η> 4 π$.

hep-ph↗

arXiv2014

Electromagnetic production of $KΣ$ on the nucleon near threshold

Photo- and electroproduction of $KΣ$ have been investigated near their production thresholds by using an effective Lagrangian approach. For this purpose, the background amplitude is constructed from suitable Feynman diagrams, whereas the resonance terms are calculated by means of the Breit-Wigner form of multipoles. Experimental data available in the proton channels ($K^+Σ^0$ and $K^0Σ^+$) with energies up to 50 MeV above the thresholds have been utilized to extract the unknown parameters. In these proton channels the calculated observables fit nicely the experimental data, whereas in the neutron channels ($K^+Σ^-$ and $K^0Σ^0$) the predicted observables contain some uncertainties due to the the uncertainties in the values of helicity photon couplings. To this end, new $K^0Σ^+$ photoproduction data are urgently required. The present analysis indicates the validity of the $P_Λ= -\frac{1}{3} P_Σ$ relation derived a long time ago. In the electroproduction sector the present analysis confirms the smooth transition between photoproduction and low $Q^2$ electroproduction data. The effect of new Crystal Ball data is shown to be mild at the backward angles. It is also found that the electroproductions of $K^0Σ^+$ and $K^0Σ^0$ are practically not the suitable reactions for investigating the $K^0$ charge form factor, since the effect is small.

nucl-th↗

arXiv2014

Boson star at finite temperature

By using a simple thermodynamical method we confirm the finding of Chavanis and Harko that stable Bose-Einstein condensate stars can form. However, by using a thermodynamically consistent boson equation of state, we obtain a less massive Bose-Einstein condensate star compared to the one predicted by Chavanis and Harko. We also obtain that the maximum mass of a boson star is insensitive to the change of matter temperature. However, the mass of boson star with relatively large radius depends significantly on the temperature of the boson matter.

astro-ph.SR↗

arXiv2014

Viscous Quark-Gluon Plasma Model Through Fluid QCD Approach

A Lagrangian density for viscous quark-gluon plasma has been constructed within the fluid-like QCD framework. Gauge symmetry is preserved for all terms inside the Lagrangian, except for the viscous term. The transition mechanism from point particle field to fluid field, and vice versa, is discussed. The energy momentum tensor that is relevant for the gluonic plasma having the nature of fluid bulk of gluon sea is derived within the model. By imposing conservation law in the energy momentum tensor, shear viscosity appears as extractable from the equation.

nucl-th↗

arXiv2014

$K^+Λ$ and $K^+Σ^0$ photoproduction with fine center-of-mass energy resolution

Measurements of $γp \rightarrow K^{+} Λ$ and $γp \rightarrow K^{+} Σ^0$ cross-sections have been obtained with the photon tagging facility and the Crystal Ball calorimeter at MAMI-C. The measurement uses a novel $K^+$ meson identification technique in which the weak decay products are characterized using the energy and timing characteristics of the energy deposit in the calorimeter, a method that has the potential to be applied at many other facilities. The fine center-of-mass energy ($W$) resolution and statistical accuracy of the new data results in a significant impact on partial wave analyses aiming to better establish the excitation spectrum of the nucleon. The new analyses disfavor a strong role for quark-diquark dynamics in the nucleon.

nucl-ex↗

arXiv2013

Constraining the mass and width of the $N^*(1685)$ resonance

We have examined the existence of the $N^*(1685)$ resonance, which is recently listed by the Particle Data Group as a one-star nucleon resonance, by using a covariant isobar model for kaon photoproduction and assuming that the resonance has $J^p=1/2^+$, in accordance with our previous finding. After the inclusion of this resonance the changes in the total $χ^2$ show two clear minima at $M_{N^*}=1650$ and 1696 MeV, which correspond to two different resonance states. The former corresponds to the narrow nucleon resonance found in our previous investigation, whereas the latter corresponds to a new resonance found as we increase the resonance width. From the latter we derive the mass and width relation of the $N^*(1685)$ resonance. We observe that the properties of both the $N^*(1685)$ and $N^*(1710)P_{11}$ resonances are strongly correlated. Although the best fit of the present work yields $M_{N^*}=1696$ MeV and $Γ_{N^*}=76$ MeV, the apparently small $N^*(1710)P_{11}$ coupling constant to the $K^+Λ$ channel found in previous investigations suggests that $Γ_{N^*}\lesssim 35$ MeV, which, according to the mass and width relation, corresponds to $M_{N^*}\lesssim 1680$ MeV.

hep-ph↗