Hadron tomography by generalized distribution amplitudes in pion-pair production process $γ^* γ\rightarrow π^0 π^0 $ and gravitational form factors for pion
S. Kumano, Qin-Tao Song, O. V. Teryaev
备注：
27 pages, 21 figures. Errata on the first and second versions of arXiv:1711.08088 [Phys. Rev. D 97, 014020 (2018)] are reflected
Hadron tomography can be investigated by three-dimensional structure functions such as generalized parton distributions (GPDs), transverse-momentum-dependent parton distributions, and generalized distribution amplitudes (GDAs). Here, we extract the GDAs, which are $s$-$t$ crossed quantities of the GPDs, from cross-section measurements of hadron-pair production process $γ^* γ\rightarrow π^0 π^0$ at KEKB. This work is the first attempt to obtain the GDAs from the actual experimental data. The GDAs are expressed by a number of parameters and they are determined from the data of $γ^* γ\rightarrow π^0 π^0$ by including intermediate scalar- and tensor-meson contributions to the cross section. Our results indicate that the dependence of parton-momentum fraction $z$ in the GDAs is close to the asymptotic one. The timelike gravitational form factors $Θ_1$ and $Θ_2$ are obtained from our GDAs, and they are converted to the spacelike ones by the dispersion relation.From the spacelike $Θ_1$ and $Θ_2$, gravitational densities of the pion are calculated. Then, we obtained the mass (energy) radius and the mechanical (pressure and shear force) radius from $Θ_2$ and $Θ_1$, respectively. They are calculated as $\sqrt {\langle r^2 \rangle _{\text{mass}}} =0.32 \sim 0.39$ fm, whereas the mechanical radius is larger $\sqrt {\langle r^2 \rangle _{\text{mech}}} =0.82 \sim 0.88$ fm. This is the first report on the gravitational radius of a hadron from actual experimental measurements. It is interesting to find the possibility that the gravitational mass and mechanical radii could be different from the experimental charge radius $\sqrt {\langle r^2 \rangle _{\text{charge}}} =0.672 \pm 0.008$ fm for the charged pion.
We present the first lattice calculation of the nucleon isovector unpolarized generalized parton distribution (GPD) at the physical pion mass using a lattice ensemble with 2+1+1 flavors of highly improved staggered quarks (HISQ) generated by MILC Collaboration, with lattice spacing $a\approx 0.09$~fm and volume $64^3\times 96$. We use momentum-smeared sources to improve the signal at nucleon boost momentum $P_z \approx 2.2$ GeV, and report results at nonzero momentum transfers in $[0.2,1.0]\text{ GeV}^2$. Nonperturbative renormalization in RI/MOM scheme is used to obtain the quasi-distribution…
The two-photon-exchange (TPE) effects in the process $e^+e^- \rightarrow π^+π^-$ at large momentum transfer are discussed within the perturbative QCD (pQCD). The contributions from the twist-2 and twist-3 distribution amplitudes (DAs) of pion are considered in the estimation. Different with the results under the one-photon-exchange (OPE) approximation, the TPE effects result in an asymmetry of the differential cross section on the scattering angle. The precise measurement of this asymmetry by the further experiment is an precise test of pQCD at large momentum transfer. The time-like electromag…
Generalized parton distributions (GPDs) are three-dimensional structure functions of hadrons, and they can reveal the orbital-angular-momentum contributions to the nucleon spin. Therefore, GPDs are important for solving the proton spin puzzle. The generalized distribution amplitudes (GDAs) are the $s$-$t$ crossed quantities of the GPDs, and the GDAs can be investigated in two-photon process ($γ^* γ\to h\bar h$) which is accessible at KEKB. The pion GDAs were obtained by analyzing the Belle measurements for $π^0 π^0$ production in the $e^+ e^-$ collision. From the obtained GDAs, the form factor…
We report on ongoing work to determine the pion-cloud contribution to the electromagnetic $N\rightarrowΔ$ transition form factors. The starting point is an $SU(6)$ spin-flavor symmetric constituent-quark model with instantaneous confinement that is augmented by dynamical pions which couple directly to the quarks. This system is treated in a relativistically invariant way within the framework of point-form quantum mechanics using a multichannel formulation. The first step is to determine the electromagnetic form factors of the bare particles that consist only of three quarks. These form factors…
Hadron tomography has been investigated by three-dimensional structure functions, such as generalized parton distributions (GPDs) and generalized distribution amplitudes (GDAs). The GDAs are $s$-$t$ crossed quantities of the GPDs, and both functions probe gravitational form factors for hadrons. We determined the pion GDAs by analyzing Belle data on the differential cross section for the two-photon process $γ^* γ\to π^0 π^0$. From the determined GDAs, we calculated timelike gravitational form factors of the pion and they were converted to the spacelike form factors by using the dispersion relat…
A sizable $\cos 4ϕ$ azimuthal asymmetry in exclusive di-pion production near $ρ^0$ resonance peak in ultraperipheral heavy ion collisions recently has been reported by STAR collaboration. We show that both elliptic gluon Wigner distribution and final state soft photon radiation can give rise to this azimuthal asymmetry. The fact that the QED effect alone severely underestimates the observed asymmetry might signal the existence of the nontrivial correlation in quantum phase distribution of gluons.
The quark flavor sector of the Standard Model is a fertile ground to look for new physics effects through a unitarity test of the Cabbibo-Kobayashi-Maskawa (CKM) matrix. We present a lattice QCD calculation of the scalar and the vector form factors (over a large $q^2$ region including $q^2 = 0$) associated with the $D \rightarrow Klν$ semi-leptonic decay. This calculation will then allow us to determine the central CKM matrix element, $V_{cs}$ in the Standard Model, by comparing the lattice QCD results for the form factors and the experimental decay rate. This form factor calculation has been …
We investigate the tomographical structure of pion and kaon in light cone quark model (LCQM). In particular, we study the parton distribution amplitude (PDA) of pion and kaon. We obtain the parton distribution function (PDF) and the generalized parton distributions (GPDs) of the pion and kaon. The valence quark PDA and PDF of pion, after QCD evolution, are found to be consistent with the data from the E791 and the E615 experiments at Fermilab, respectively. Further, we investigate the transverse momentum distributions (TMDs) of pion and kaon. We also discuss the unpolarized TMD evolution for p…
We examine the axion emission from supernovae with a complete set of relevant axion couplings including the axion-pion-nucleon contact interaction which was ignored in the previous studies. Two processes are affected by the axion-pion-nucleon contact interaction, $π^-+p \rightarrow n + a$ and $n+p\rightarrow n+p+a$, and these processes can be the dominant source of axions for some region in the axion parameter space or in astrophysical conditions encountered inside supernovae. We find that the contact interaction can enhance the axion emissivity of $π^-+p \rightarrow n + a$ by a factor of $2-4…
Generalized parton distributions (GPDs) are 3-dimensional (3D) structure functions for hadrons, and they are important for solving the proton spin puzzle including partonic orbital-angular-momentum contributions. The $s$-$t$ crossed quantities of the GPDs are generalized distribution amplitudes (GDAs). Here, $s$ and $t$ are Mandelstam variables. The GDAs can be studied in two-photon processes ($γ^* γ\to h \bar h$) at KEKB. A GDA describes the amplitude from quark and antiquark to the hadron pair $h \bar h$. In 2016, the Belle collaboration reported measurements for pion-pair production in elec…
We examine the contribution of the pion cloud to the electromagnetic $N \rightarrow Δ$ transition form factors within a relativistic hybrid constituent-quark model. In this model baryons consist not only of the $3q$ valence component, but contain, in addition, a $3 q π$ non-valence component. We start with constituent quarks which are subject to a scalar, isoscalar confining force. This leads to an $SU(6)$ spin-flavor symmetric spectrum with degenerate nucleon and Delta masses. Mass splitting is caused by pions which are assumed to couple directly to the quarks. The point-form of relativistic …
Within the multiple scattering formulation, the incoherent pion production in neutrino-deuteron reactions at energies near the $Δ(1232)$ resonance is investigated. The calculations include an impulse term and one-loop contributions from nucleon-nucleon ($NN$) and pion-nucleon ($πN$) final state interactions. The input amplitudes of $πN$ scattering and electroweak pion production reaction on nucleon are generated from a dynamical model which describes very extensive data of $πN$ scattering and both the electromagnetic and the weak pion production reactions on the nucleon. The $NN$ scattering am…
The electric $α_π$ and magnetic $β_π$ charged pion Compton polarizabilities are of fundamental interest in the low-energy sector of quantum chromodynamics (QCD).They are directly linked to the phenomenon of spontaneously broken chiral symmetry within QCD and to the dynamics of the pion-photon interaction.The combination ($α_π-β_π$) was measured by:(1) CERN COMPASS via radiative pion Primakoff scattering (Bremsstrahlung) in the nuclear Coulomb field, $π^- Z \rightarrow π^-Z γ$, (2) SLAC PEP Mark-II via two-photon production of pion pairs, $γγ\rightarrowπ^+π^-$, and (3) Mainz Microtron via radia…
The $η'$ meson is associated with the U(1) anomaly. In this paper, a successful effective chiral theory of mesons has been applied to study the anomalous decay of $η'\rightarrow π^+π^-π^{+(0)}π^{-(0)}$. In this study, the contributions of triangle and box anomalies are calculated. It is shown that the contribution of box diagrams is important in this process. We predict branching ratios of $Br(η' \rightarrow π^+ π^- π^+ π^-)={1 \over 2}Br(η' \rightarrow π^+ π^- π^0 π^0) = (8.3 \pm 1.2) \times 10^{-5}$, which is in good agreement with BESIII measurement.
Using the upper bound on the effective number of light neutrino species during primordial nucleosynthesis and the cosmological pion-pole mechanism $γγ\rightarrow π^0\rightarrow γX$, we obtain an upper limit on the branching ratio for the decay BR$(π^0\rightarrow γX)<3\times 10^{-13}$, where $X$ is any long-lived weakly interacting neutral vector particle with mass smaller than the neutral pion mass.
The electric $α_π$ and magnetic $β_π$ charged pion Compton polarizabilities are of fundamental interest in the low-energy sector of quantum chromodynamics (QCD). They characterize the induced dipole moments of the pion during $γπ$ Compton scattering. Pion polarizabilities affect the shape of the $γπ$ Compton scattering angular distribution.The combination $(α_π - β_π)$ was measured by: (1) CERN COMPASS via $π Z \rightarrow π Z γ$ radiative pion Primakoff scattering in the nuclear Coulomb field, (2) SLAC PEP Mark-II via two-photon production of pion pairs, $γ γ \rightarrow π^+ π^-$, and (3) Mai…
We study the self-energy amplitudes for the rho-omega meson system produced by an effective field theory model at the quark level characterized by a finite range quark-quark interaction and an isospin breaking bare quark mass difference $m_u - m_d$. Dynamical effects associated with confinement and dressing of quarks and the finite size of the produced $\bar{q}q$ meson modes are treated. Parameters of this approach, previously constrained by soft pion physics, are here supplemented in a minimal way to reproduce $m_ω$ and $g_{ρππ}$. Calculations are carried out up to the one pion loop level and…
We derive a master formula for chiral $SU(2)\times SU(2)$ breaking, based on the Veltman-Bell equations and the Peierls-Dyson relation. Our approach does not rely on the use of the soft pion limit or an expansion around the chiral limit, and yields exact results for on-shell pions. Threshold theorems for $πN\rightarrow πN$, $γN\rightarrow πN$, $πN\rightarrowππN$, $γN\rightarrow γπN$, $γN\rightarrow ππN$ and $πN\rightarrow πγN$ are recovered, and corrections to them are given. The reactions $π\rightarrow eνγ$, $π\rightarrow eνe^+e^-$, $γπ\rightarrow γπ$ and $γγ\rightarrow ππ$ are also discussed…
The $m_{ππ}$ spectrum and various angular distributions in $\upss$ are studied including the effects of the $ππ$ phase shift in the $I=L=0$ channel using the lowest order amplitude in the pion momentum expansion. Our results are compared with the recent CLEO data, and we find good agreement except for the $\cosθ_π^*$ distributions. We argue that the $\cosθ_π^*$ distribution, contrary to other distributions, is sensitive to the higher order corrections in the pion momentum expansion. This argument is supported by using an ansatz for the amplitude which is of higher order in the pion momentum ex…
We use three-flavour hard pion Chiral Perturbation Theory (HPChPT) in both the heavy meson and a relativistic formulation to calculate the chiral logarithms $m^2\log(m^2/μ^2)$ contributing to the formfactors of the $B_{(s)}\rightarrow π,K,η$ and $D_{(s)}\rightarrow π,K,η$ transitions at momentum transfer $q^2$ away from the endpoint $q^2_\mathrm{max}=(m_B-m_M)^2$. We compare our results with CLEO $D\toπ$ and $D\to K$ data. We also calculate the Isgur-Wise function of the $B_{(s)}\rightarrow D_{(s)}$ semileptonic decay away from the endpoint and the chiral logarithms for the pion and kaon elect…
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The inclusive decay rate into pions of the charmed $D_s$ meson is surprisingly larger than estimates expected from the $W$ annihilation, adopting commonly used values of current-algebra up and down quark masses. We then go beyond this tree diagram and consider possible QCD effects that might cause such a large rate. There are two; the first one is related to the spectator decay $ c{\bar s} \rightarrow s{\bar s} + u {\bar d}$ followed by $ s {\bar s} \rightarrow d{\bar d}~,~ u{\bar u}$ via two-gluon exchange box diagram. The second one is a gluon emission in weak annihilation for which the usua…
We evaluate the contribution of the final state interaction (FSI) due to single pion exchange inelastic scattering for $D^+\rightarrow \bar {K}^{0*}π^+$ and $D^+\rightarrow \bar K^0ρ^+$ processes. The effects are found to be very significant. The hadronic matrix elements of the weak transition are calculated in terms of the heavy quark effective theory (HQET), so are less model-dependent and more reliable.
Generalized parton distributions (GPDs) have been investigated in the deeply virtual Compton scattering (DVCS) to solve the proton spin puzzle. On the other hand, the generalized distribution amplitudes (GDAs) can be studied in the two-photon process $γ^* γ\rightarrow h \bar{h}$ which is accessible at KEKB. Namely, the GDAs are the $s$-$t$ crossed quantities of the GPDs. In 2016, the differential cross section of the process $γ^* γ\rightarrow π^0 π^0$ was measured by the Belle collaboration in the $e^+e^-$collision , so that the pion GDAs can be obtained by analyzing the Belle data. Expressing…
Decoding the structure near the $π^+π^-$ mass threshold in $ψ(3686) \rightarrow J/ψπ^+π^-$ decays
University of Science and Technology Beijing（北京科技大学）；Helmholtz-Institut für Strahlen- und Kernphysik (Theorie) and Bethe Center for Theoretical Physics, Universität Bonn（波恩大学亥姆霍兹射线与核物理研究所（理论）及贝特理论物理中心）；Institute of Theoretical Physics, Chinese Academy of Sciences（中国科学院理论物理研究所）；School of Physical Sciences, University of Chinese Academy of Sciences（中国科学院大学物理科学学院）；Southern Center for Nuclear-Science Theory (SCNT), Institute of Modern Physics, Chinese Academy of Sciences（中国科学院现代物理研究所南方核科学理论中心）；Institute for Advanced Simulation, Forschungszentrum Jülich（于利希研究中心先进模拟研究所）
The three-body decays $B^0_s \rightarrow ψ(2S,3S) π^+ π^-$ are studied based on the perturbative QCD approach. With the help of the nonperturbative two-pion distribution amplitudes, the analysis is simplified into the quasi-two-body processes. Besides the traditional factorizable and nonfactorizable diagrams at the leading order, the next-to-leading order vertex corrections are also included to cancel the scale dependence. The $f_0(980)$, $f_0(1500)$ resonance contributions as well as the nonresonant contributions are taken into account using the presently known $ππ$ time-like scalar form fact…
There exists a longstanding disagreement between bubble chamber measurements of the single pion production channel $ν_μp\rightarrow μ^{-}pπ^{+}$ from the Argonne and Brookhaven National Laboratories. We digitize and reanalyse data from both experiments to produce cross-section ratios for various interaction channels, for which the flux uncertainties cancel, and find good agreement between the experiments. By multiplying the cross-section ratio by the well-understood charged current quasi-elastic cross-section on free nucleons, we extract single-pion production cross-sections which do not depen…
Can one expect gamma rays rates from the QGP to be higher than from the hot hadronic gas phase? Xiong, Shuryak, Brown (XSB) calculate photon production from a hot hadronic gas via the reaction $π^- + ρ^0 \rightarrow π^- + γ$. They assume that this reaction proceeds through the a$_1$(1260). They also use their estimated a$_1$ radiative width to calculate the pion polarizability; following a connection noted previously by Holstein. However, for a$_1$(1260) $\rightarrow πγ$, the experimental radiative width is more than two times less than the value 1.4 MeV estimated and used by XSB. We describe …
The determination of the Argonne National Laboratory-Osaka University (ANL-Osaka) Partial-Wave Amplitudes (PWA) of $πN$ and $γN$ Reactions is reviewed. The predicted PWA are presented on a web page (https://www.phy.anl.gov/theory/research/anl-osaka-pwa). The formulas are given for using the predicted PWA to calculate the cross sections of (1) meson-baryon ($MB$) scattering $MB \rightarrow M'B'$ with $MB, M'B'= πN, ηN, KΛ, KΣ$, (2) two-pion production $πN \rightarrow πΔ, ρN, σN \rightarrow ππN$, (3) Meson photoproduction $γN \rightarrow πN, ηN, KΛ, KΣ$, (4) Pion electroproduction $N(e,e'π)N$, (…
The $f_{1}(1420)$ productions via pion and kaon induced reactions on a proton target are investigated in an effective Lagrangian approach. Two treatments of the $t$-channel Born term, the Feynman model and the Regge model, are introduced to calculate the total and differential cross sections of the $π^{-}p\rightarrow f_{1}(1420)n$ and $K^{-}p\rightarrow f_{1}(1420)Λ$ reactions. The numerical results indicate that the experimental data of the total cross section of the $π^{-}p\rightarrow f_{1}(1420)n$ reaction can be reproduced in both the Feynman and the Regge models. Based on the parameters d…
This is an extension of the prediction of strange baryon decays to the decays of charmed baryons using QCD Sum Rules. Using QCD Sum Rules we estimate the decay $Λ^+_c (udc) \rightarrow Λ^o_s(uds)+ π^+$. Although some weak decays of the $Λ^+_c$ have been measured, since it is difficult to measure $Λ^+_c \rightarrow Λ^o_s+ π^+$ our estimates should be useful for future experiments
The quasielastic charged current (CCQE) $ν_e n \rightarrow e^- p$ scattering is the dominant mechanism to detect appearance of a $ν_e$ in an almost $ν_μ$ flux at the 1 GeV scale. Actual experiments show a precision below 1% and between less known background contributions, but necessary to constraint the event excess, we have the radiative corrections. A consistent model recently developed for the simultaneous description of elastic and radiative $πN$ scattering, pion-photoproduction and single pion production processes, both for charged and neutral current neutrino-nucleon scattering, is exten…
We present the study of radiative tau decay ($τ^- \rightarrow π^- ν_τγ$), computing the structure dependent contribution using Light Cone Sum Rules. This decay includes the same form factors as the radiative pion decay with the crucial difference that the momentum transfer squared, $t$, between the pion-photon system is positive, which makes these form factors timelike and also as $t$ can now take values upto $m_τ^2$ , it can produce real hadronic resonances. The analytical form for these form factors has been calculated using light cone sum rules method and the invariant mass-spectrum in the …
We study the strangeness and charm productions induced by the pion beam, i.e. the $π^-$p $\rightarrow$ $K^{*0}Λ$ and $π^-$p $\rightarrow$ $D^{*-}Λ_c^+$ reactions, based on two different theoretical frameworks: an effective Lagrangian method and a Regge approach. In order to estimate the magnitude of the charm production relative to that of the strangeness production, we assume that the coupling constants for the charmed meson and baryon vertices are the same as those for the strangeness channel. We found that the total cross section for the charm production was about $10^3 - 10^6$ times smalle…
This paper presents a method for the analysis of process $J/ψ\rightarrow ρπ\rightarrow π^+π^-π^0$ based on the consideration of the angles of expansion of finite pion pairs. The proposed approach makes it possible to effectively carry out selection of events in both neutral and charge-conjugate modes of the decay of $J/ψ\rightarrow ρπ$. Application of the method for the analysis of similar three-body decays in some cases will simplify the analysis and refine current results.
We present the differential branching fractions for the $B\rightarrow ψππ$ decays with the charmonia $ψ=J/ψ,ψ(2S)$ in the invariant mass of the $P$-wave pion pairs in the perturbative QCD approach. The two-pion distribution amplitudes (DAs) corresponding to both longitudinal and transverse polarizations are constructed to capture important final state interactions in the processes. The time-like form factors, normalizing the two-pion DAs, contains contributions from the $ρ$ resonance and radial excitations fitted to the BaBar data. Given the hadronic parameters for the two-pion DAs associated …
Dielectron production in reactions $π^- p \rightarrow n e^+e^-$ and $π^- p \rightarrow n e^+e^- γ$ at energies less than 1 GeV is studied assuming electron-positron pair production to occur in the virtual time-like photon splitting process. Theoretical predictions of the effective mass distribution of dielectrons and their angular dependence are presented. Extraction of the electromagnetic form factor of baryon transition in the time-like region from future experiments of the HADES Collaboration is discussed.
The lowest-lying resonance in the QCD spectrum is the $0^{++}$ isoscalar $σ$ meson, also known as the $f_0(500)$. We augment SU(2) chiral perturbation theory ($χ$PT) by including the $σ$ meson as an additional explicit degree of freedom, as proposed by Soto, Talavera, and Tarrús and others. In this effective field theory, denoted $χ$PT$_S$, the $σ$ meson's well-established mass and decay width are not sufficient to properly renormalize its self energy. At $\mathcal{O}(p^4)$ another low-energy constant appears in the dressed $σ$-meson propagator; we adjust it so that the isoscalar pion-pion sca…
The production of the hidden-charm pentaquarks $P_{c}$ via pion-induced reaction on a proton target is investigated within an effective Lagrangian approach. Three experimentally observed states, $P_c(4312)$, $P_c(4440)$, and $P_c(4457)$, are considered in the calculation, and the Reggeized $t$-channel meson exchange is considered as main background for the reaction $π^{-}p\rightarrow J/ψn$. The numerical results show that the experimental data of the total cross section of the reaction $π^{-}p\rightarrow J/ψn$ at $W\simeq 5$ GeV can be well explained by contribution of the Reggeized $t$ channe…
We present a dispersive representation of the D-term form factor for hard exclusive reactions, using unsubtracted $t$-channel dispersion relations. The $t$-channel unitarity relation is saturated with the contribution of two-pion intermediate states, using the two-pion distributions amplitude for the $γ^*γ\rightarrow ππ$ subprocess and reconstructing the $ππ\rightarrow N\bar N$ subprocess from available information on pion-nucleon partial-wave helicity amplitudes. Results for the D-term form factor as function of $t$ as well as at $t=0$ are discussed in comparison with available model predicti…
The electromagnetic pion form factor, $F_π(q^2)$, is calculated for spacelike-$q^2$ in impulse approximation using a confining quark propagator, $S$, and a dressed quark-photon vertex, $Γ_μ$, obtained from realistic, nonperturbative Dyson-Schwinger equation studies. Good agreement with the available data is obtained for $F_π(q^2)$ and other pion observables, including the decay $π^0 \rightarrow γ\,γ$. This calculation suggests that soft, nonperturbative contributions dominate $F_π(q^2)$ at presently accessible~$q^2$.
In the framework of Chiral Perturbation Theory including photons, we found that the contribution of the photon exchange between two intermediate charged Kaons to the slope parameter of the decay (η\rightarrow 3π^{0}) amounts to (-0.0221\pm 0.0034). When compared with the experimental value, (α=-0.0317\pm 0.0016), on the one hand, and with the contribution of the up and down quark mass difference, (+0.013\pm 0.032), on the other hand, our result leads to the direct conclusion: \textit{The} (η\rightarrow 3π^{0}) \textit{decay \uline{cannot} be used to determine} (m_{d}-m_{u}).
We obtain the distribution amplitude (DA) of the pion from its light-front wave functions in the basis light-front quantization framework. This light-front wave function of the pion is given by the lowest eigenvector of a light-front effective Hamiltonian consisting a three-dimensional confinement potential and the color-singlet Nambu--Jona-Lasinion interaction both between the constituent quark and antiquark. The quantum chromodynamics (QCD) evolution of the DA is subsequently given by the perturbative Efremov-Radyushkin-Brodsky-Lepage evolution equation. Based on this DA, we then evaluate th…
We study the photoproduction of the charged top-pion predicted by the top triangle moose ($TTM$) model (a deconstructed version of the topcolor-assisted technicolor $TC2$ model) via the processes $pp\rightarrow p γp \rightarrow π^\pm_t t +X$ at the 14 $TeV$ Large Hadron Collider ($LHC$) including next-to-leading order ($NLO$) $QCD$ corrections. Our results show that the production cross sections and distributions are sensitive to the free parameters $\sinω$ and $M_{π_t}$. Typical $QCD$ correction value is $7\% \sim 11\%$ and does not depend much on $\sinω$ as well as the forward detector accep…
We propose to describe the process $ p ~ \bar{p} \rightarrow π^+ ~ π^-$ in a perturbative, QCD motivated framework in which a hard $ud \, \bar{u} \bar{d} \rightarrow d \, \bar{d} $ annihilation factorizes from soft transition distribution amplitudes. We advocate that the scale allowing for this factorization is the large transverse momentum transfer. In our simplified model, in which the proton is considered as a (scalar)diqark-quark system, a transition distribution amplitude describes the non-perturbative transition of the proton to the meson by emission of a scalar, isoscalar $ ud $-diquark…
Dark mesons are bosonic composites of a new, strongly-coupled sector beyond the Standard Model. We consider several dark sectors with fermions that transform under the electroweak group, as arise from a variety of models including strongly-coupled theories of dark matter (e.g., stealth dark matter), bosonic technicolor (strongly-coupled indcued electroweak symmetry breaking), vector-like confinement, etc. We consider theories with two and four flavors under an $SU(N)$ strong group that acquire variously chiral, vector-like, and mixed contributions to their masses. We construct the non-linear s…
In the present work, we investigate the production of $P_{c}$ and $Z_c(3900)/Z_{cs}(3985)$ states in the processes of $πp \rightarrow Z_{c}(3900) P_{c} $/$Kp\rightarrow Z_{cs}(3985) P_{c}$ with an effective Lagrangian approach. Our estimations indicates that the cross sections depends on the model parameters and beam energies, in particular, the cross sections for $πp \to Z_c(3900) P_c(4312)$ and $πp \to Z_c(3900) P_c(4440)$ are similar and can reach up to 10 nb, while those for $πp \to Z_c(3900) P_c(4457)$ can be 30 nb. As for $Kp \to Z_{cs}(3985)P_c$, the cross sections are about 2.5 times s…
The exclusive semileptonic decay $B \rightarrow π\ell ν$ is a key process for the determination of the Cabibbo-Kobayashi-Maskawa matrix element $V_{ub}$ from the comparison of experimental rates as a function of $q^2$ with theoretically determined form factors. The sensitivity of the form factors to the $u/d$ quark mass has meant significant systematic uncertainties in lattice QCD calculations at unphysically heavy pion masses. Here we give the first lattice QCD calculations of this process for u/d quark masses going down to their physical values, calculating the $f_0$ form factor at zero reco…
Recent attempts to detect the pion polarizability via analysis of $γγ\rightarrowππ$ measurements are examined. The connection between calculations based on dispersion relations and on chiral perturbation theory is established by matching the low energy chiral amplitude with that given by a full dispersive treatment. Using the values for the polarizability required by chiral symmetry, predicted and experimental cross sections are shown to be in agreement.
Three-dimensional tomography of hadrons can be investigated by generalized parton distributions (GPDs), transverse-momentum-dependent parton distributions (TMDs), and generalized distribution amplitudes (GDAs). The GDA studies had been only theoretical for a long time because there was no experimental measurement until recently, whereas the GPDs and TMDs have been investigated extensively by deeply virtual Compton scattering and semi-inclusive deep inelastic scattering. Here, we report our studies to determine pion GDAs from recent KEKB measurements on the differential cross section of $γ^* γ\…
We investigate how the gravitational form factors of the nucleon undergo changes in nuclear matter, emphasizing the Abel transformation from the three-dimensional (3D) Breit frame to the two-dimensional (2D) light-front frame. Since the gravitational form factors reveal the mechanical structure of the nucleon, we examine also the medium modifications of the energy-momentum, pressure, and shear-force distributions. We scrutinize the stabilities of the nucleon in nuclear matter. For this purpose, we employ the in-medium modified SU(2) Skyrme model to study these mechanical quantities of the nucl…
We here compute the reaction $ γ\; γ\rightarrow G \; π^{0} $ for various glueball candidates $ G $ and their assumed quantum states, using a non-relativistic gluon bound-state model for the glueball.
Assuming that the pion-pion scattering amplitude and its absorptive part are analytic inside an ellipse in $t$- plane with foci $t=0$, $u=0$ and right extremity $t=4 m_π^2 +ε$, ($ε> 0$), except for cuts prescribed by Mandelstam representation for $t\geq 4 m_π^2$, $u\geq 4 m_π^2$ , and bounded by $s^N$ on the boundary of this domain, we prove that for $s\rightarrow \infty$, σ_{inel} (s) > \frac{Const}{s^{5/2} }\exp {[-\frac{\sqrt{s}}{4} (N+5/2) \ln {s} ]}.
