arXiv subjects

Akira Watanabe

Publications and source records attributed to Akira Watanabe.

At least 19 recordsLinked to original sources

arXiv2025

Gravitational form factors of the baryon octet in holographic QCD

The gravitational form factors (GFFs) of the baryon octet, including hyperons, are investigated in a bottom-up holographic QCD model that explicitly incorporates the SU(3) flavor symmetry breaking through the strange quark mass. We fit the model parameters to reproduce the empirical masses of the baryon octet and examine the dependence of GFFs on the probe momentum. Our numerical results show distinct differences in the GFFs across the baryon octet. The computed GFFs are found to be in reasonable agreement with available lattice QCD results for the non-strange/nucleon sector. We also calculate the gravitational radii of the baryon octet and find that they decrease with increasing strangeness, indicating that heavier hyperons are more compact.

hep-ph↗

arXiv2025

Holographic description of the kaon gravitational form factor

We compute the kaon gravitational form factor (GFF) using a bottom-up holographic QCD approach that incorporates SU(3) flavor symmetry breaking through the strange quark mass. We present the resulting Q^2 dependence of the kaon GFF and compare it with that of the pion. In the high-energy limit, the kaon GFF exhibits a 1/Q^2 falloff, in agreement with perturbative QCD. Furthermore, we extract the gravitational radius of the kaon and find it to be almost the same as that of the pion, with a slightly smaller value.

hep-ph↗

arXiv2025

Vector meson dominance in photon structure functions at small $x$ from holography

We investigate the photon structure functions via the photon-photon and photon-vector meson scattering within the framework of holographic QCD, focusing on the small Bjorken $x$ region and assuming that the Pomeron exchange dominates. The quasi-real photon structure functions are formulated as the convolution of the known U(1) vector field wave function with the Brower-Polchinski-Strassler-Tan (BPST) Pomeron exchange kernel in the five-dimensional AdS space. Assuming the vector meson dominance, the photon structure functions can be calculated in a different way with the BPST kernel and vector meson gravitational form factor, which can be obtained in a bottom-up AdS/QCD model, for the Pomeron-vector meson coupling. It is shown that the obtained $F_2$ structure functions in the both ways agree with the experimental data, which implies the realization of the vector meson dominance within the present model setup. Calculations for the longitudinal structure function and the longitudinal-to-transverse ratio are also presented.

hep-ph↗

arXiv2025

Gravitational form factor of the kaon in holographic QCD

The gravitational form factor (GFF) of the kaon is investigated in a bottom-up holographic QCD model, in which the strange quark mass breaks the SU(3) flavor symmetry. The probe energy ($Q^2$) dependence of the kaon GFF is explicitly shown and compared to that of the pion. It is presented that our result shows the $1/Q^2$ behavior in the high energy region, which is consistent with the perturbative QCD prediction. The gravitational radius of the kaon is also calculated, and it is found that the result is quite close to that of the pion but slightly smaller.

hep-ph↗

arXiv2025

High-precise determination of critical exponents in holographic QCD

The precise determination of critical exponents is crucial for understanding the properties of strongly interacting matter under extreme conditions. These exponents are fundamentally linked to the system's behavior near the critical end point (CEP), making precise localization of the CEP essential. However, precisely identifying the CEP within the framework of AdS/CFT correspondence presents considerable challenges. In this study, we explore critical phenomena and critical exponents within a holographic QCD model. We achieve high-precision calculations of the CEP's position and dynamically analyze the behavior of the critical exponent as it approaches the CEP using limiting methods. Our results indicate that linear fitting is only appropriate in regions very close to the CEP. Furthermore, we find that although the values of the critical exponents vary when approaching the CEP from different directions, they ultimately converge to a single fixed value, revealing a universal behavior among these exponents. Our research underscores the importance of precisely determining the CEP, selecting the fitting region, and considering the direction of the approach when predicting critical exponents. These findings establish a vital benchmark for identifying critical phenomena and their associated exponents.

hep-ph↗

arXiv2024

Moving doubly heavy baryon in a strongly coupled plasma from holography

Gauge/gravity duality is used to study properties of the doubly heavy baryon $(\mathrm{QQq})$ at finite rapidity and temperature in the heavy-ion collision. We investigate the impact of rapidity on string breaking and screening of $\mathrm{QQq}$, and compare these effects with the results for $\rm Q\bar{Q}$ in detail. Computations reveal that the string-breaking distances of $\mathrm{QQq}$ and $\rm Q\bar{Q}$ are close in the confined state and the effects of rapidity and temperature on the string breaking are not significant. An interesting result shows that $\mathrm{QQq}$ cannot be found at high enough temperatures and rapidities; however, $\rm Q\bar{Q}$ can exist under any conditions as long as the separation distance is small enough. Besides, the screening distances of $\mathrm{QQq}$ and $\rm Q\bar{Q}$ are also compared at finite rapidity and temperature. Based on the above analysis, we infer that $\rm Q\bar{Q}$ is more stable than $\mathrm{QQq}$ at finite rapidity and temperature.

hep-ph↗

arXiv2024

Holographic description of elastic photon-proton and photon-photon scattering

We investigate the elastic photon-proton and photon-photon scattering in a holographic QCD model, focusing on the Regge regime. Considering contributions of the Pomeron and Reggeon exchange, the total and differential cross sections are calculated. While our model involves several parameters, by virtue of the universality of the Pomeron and Reggeon, for most of them the values determined in the preceding study on the proton-proton and proton-antiproton scattering can be employed. Once the two adjustable parameters, the Pomeron-photon and Reggeon-photon coupling constant, are determined with the experimental data of the total cross sections, predicting the both cross sections in a wide kinematic region, from the GeV to TeV scale, becomes possible. We show that the total cross section data can be well described within the model, and our predictions for the photon-proton differential cross section are consistent with the data.

hep-ph↗

arXiv2024

Elastic proton-neutron and antiproton-neutron scattering in holographic QCD

The total and differential cross sections of the elastic proton-neutron and antiproton-neutron scattering are studied in a holographic QCD model, focusing on the Regge regime. Taking into account the Pomeron and Reggeon exchange, which are described by the Reggeized spin-2 glueball and vector meson propagator respectively, those cross sections are obtained. It is presented that the currently available experimental data of the total cross sections can be well described within the model. Once a single adjustable parameter is determined with the total cross section data, the differential cross sections can be calculated without any additional parameters. Although the available differential cross section data are limited, it is found that our predictions are consistent with those.

hep-ph↗

arXiv2024

Elastic pion-proton and pion-pion scattering via the holographic Pomeron and Reggeon exchange

The elastic pion-proton and pion-pion scattering are studied in a holographic QCD model, focusing on the Regge regime. Taking into account the Pomeron and Reggeon exchange, which are described by the Reggeized $2^{++}$ glueball and vector meson propagator respectively, the total and differential cross sections are calculated. The adjustable parameters involved in the model are determined with the experimental data of the pion-proton total cross sections. The differential cross sections can be predicted without any additional parameters, and it is shown that our predictions are consistent with the data. The energy dependence of the Pomeron and Reggeon contribution is also discussed.

hep-ph↗

arXiv2024

Pomeron and Reggeon contributions to elastic proton-proton and proton-antiproton scattering in holographic QCD

The total and differential cross sections of elastic proton-proton and proton-antiproton scattering are studied in a holographic QCD model, considering the Pomeron and Reggeon exchanges in the Regge regime. In our model setup, the Pomeron and Reggeon exchanges are described by the Reggeized spin-2 glueball and vector meson propagators, respectively. How those contributions change with the energy is explicitly shown, focusing on the contribution ratios. The adjustable parameters included in the model are determined with the experimental data, and it is presented that the resulting total and differential cross sections are consistent with the data in a wide kinematic region.

hep-ph↗

arXiv2024

Role of Coulomb interaction in elastic pion-proton scattering from holography

Differential cross sections of the elastic pion-proton scattering are investigated at very small momentum transfer in a holographic QCD model, considering both the strong and Coulomb interaction in the Regge regime. The strong interaction is described by the Pomeron and Reggeon exchange, and the Coulomb interaction is characterized by the one photon exchange. The two interactions are linked through an interference term and we only need to determine a single adjustable parameter involved in this term. As to the parameters for the strong interaction, we can utilize the values determined in the previous studies. The differential cross sections can be predicted without any additional parameters, and it is shown that our predictions are consistent with the experimental data. We explicitly show the momentum transfer dependence for the interference effect. The energy dependence of the contribution ratios for each component is also discussed.

hep-ph↗

arXiv2023

Contribution of Coulomb interaction to elastic pp and p p\bar scattering in holographic QCD

The differential cross sections of elastic proton-proton (pp) and proton-antiproton (pp\bar) scattering are studied in a holographic QCD model, considering the strong and Coulomb interaction in the Regge regime. Based on previous studies of strong interactions described in terms of Pomeron and Reggeon exchange, we add the contribution of Coulomb interaction described by photon exchange. We present the momentum transfer dependence of the contribution rates for each component, especially for the Coulomb-nuclear interference, which refers to the cross term between both interactions. For the adjustable parameters for the strong interaction, we can adopt the values determined in previous studies, and there are no extra adjustable parameters that need to be determined for the Coulomb interaction. It is presented that the resulting differential cross sections are consistent with the data for pp and pp\bar scattering.

hep-ph↗

arXiv2022

Elastic pion-proton and pion-pion scattering at high energies in holographic QCD

The total and differential cross sections of high energy pion-proton and pion-pion scattering are investigated in a holographic QCD model, focusing on the Regge regime in which the Pomeron exchange gives the dominant contribution to those cross sections. The Pomeron is described by the Reggeized spin-2 particle propagator, and the hadron-Pomeron couplings are given by gravitational form factors of the hadrons, which are obtained from the bottom-up AdS/QCD models. Since the parameters, which characterize the Pomeron trajectory, have been determined in a preceding study of the proton-proton scattering, the pion-proton cross sections can be expressed with a single adjustable parameter. Once this parameter is determined by the experimental data of the pion-proton total cross section, its differential cross section and the pion-pion cross sections can be calculated without any additional parameter. Although the currently available data are limited, it is found that our calculation is consistent with those. Our predictions are explicitly shown, and the present model can be tested at the future experimental facilities.

hep-ph↗

arXiv2022

Elastic proton-proton scattering at LHC energies in holographic QCD

The cross sections of the high energy proton-proton scattering are studied in a holographic QCD model, focusing on the Regge regime. In our model setup, the involved nonperturbative partonic dynamics is described by the Pomeron exchange, which is realized by applying the Reggeized spin-2 particle propagator together with the proton gravitational form factor obtained from the bottom-up AdS/QCD model. Our model includes three adjustable parameters which are to be fitted by experimental data. We show that both the resulting differential and total cross sections are consistent with data, including the ones recently measured at $\sqrt{s}=13$ TeV by the TOTEM collaboration at the LHC. Our results imply that the present framework works well in the considered TeV scale, and further applications to other high energy scattering processes, in which the involved strong interaction can be approximated by the Pomeron exchange, are possible.

hep-ph↗

arXiv2020

Extraction of gluon distributions from structure functions at small x in holographic QCD

We investigate the nucleon and pion gluon distribution functions in the framework of holographic QCD, focusing on the small Bjorken x region. Based on an approximate relation, the gluon distributions are extracted from structure functions of the unpolarized deep inelastic scattering which can be calculated with a holographic QCD model, assuming the Pomeron exchange. All the adjustable parameters of the model are determined with the HERA data of the proton structure functions. We explicitly show that the extracted proton gluon distribution is consistent with results of the recent global QCD analysis. The structure functions of the pion can be computed without any additional parameter, which enables us to predict its gluon distribution also. We find that the resulting pion gluon density is smaller than the proton's, and agrees with the recent global QCD analysis result within the uncertainties.

hep-ph↗

arXiv2020

Total hadronic cross sections at high energies in holographic QCD

We present our analysis on high energy hadron-hadron scattering in the framework of the holographic QCD. Combining the Brower-Polchinski-Strassler-Tan Pomeron exchange kernel and gravitational form factors of the involved hadrons which are obtained by using the bottom-up AdS/QCD models in the five-dimensional AdS space, we calculate the total cross sections at high energies. We show that our calculations for the nucleon-nucleon scattering agree with the experimental data including the recent ones taken by the TOTEM collaboration at the LHC. The present framework is applicable to any high energy process, in which the strong interaction can be approximated by the Pomeron exchange. We present the results for the pion-nucleon and pion-pion scattering as examples, which can be obtained without any additional parameter because all the adjustable parameters are fixed via the analysis on the nucleon-nucleon scattering. The resulting total cross section ratios are $σ_{tot}^{πN} / σ_{tot}^{N N} = 0.63$ and $σ_{tot}^{ππ} / σ_{tot}^{N N} = 0.45$, respectively.

hep-ph↗

arXiv2019

Differential and total cross sections of high energy proton-proton scattering in holographic QCD

The analysis on the high energy proton-proton scattering is presented, focusing on the Regge regime and considering the Pomeron exchange to describe the involved nonperturbative dynamics in the framework of holographic QCD. We combine the Reggeized spin-2 particle propagator and the proton gravitational form factor, which is obtained from the bottom-up AdS/QCD model, and calculate the differential and total cross sections. We explicitly demonstrate the comparison between our calculations and the currently available experimental data including the recent ones measured at $\sqrt{s} = 13$ TeV by the TOTEM collaboration at the LHC. It is shown that our results are consistent with the data, which implies that the present framework works in the considered TeV scale.

hep-ph↗

arXiv2019

Total Hadronic Cross Sections via the Holographic Pomeron Exchange

The analysis on the hadron-hadron scattering at high energies in the framework of holographic QCD is presented. Combining the Pomeron exchange kernel and the hadron-Pomeron couplings which are obtained from the bottom-up AdS/QCD models, we calculate the total cross sections. Our calculation for the nucleon-nucleon scattering is consistent with the experimental data including the recent ones measured by the TOTEM collaboration at the LHC. Within the framework, one can consider other processes involving other hadrons. As examples to show this feature of the model, the resulting total cross sections of the pion-nucleon and pion-pion scattering are also presented.

hep-ph↗