Hadronic Wave Functions Research Articles

Intrinsic charm contribution to the prompt atmospheric neutrino flux

In this work we investigate the impact of intrinsic charm on the prompt atmospheric neutrino flux. The color dipole approach to heavy quark production is generalized to include the contribution of processes initiated by charm quarks. The prompt neutrino flux is calculated assuming the presence of intrinsic charm in the wave function of the projetile hadron. The predictions are compared with previous color dipole results which were obtained taking into account only the process initiated by gluons. In addition, we estimate the atmospheric (conventional + prompt) neutrino flux and compare our predictions with the ICECUBE results for the astrophysical neutrino flux. Our results demonstrate that the contribution of the charm quark initiated process is non - negligible and that the prompt neutrino flux can be enhanced by a factor $\approx$ 2 at large neutrino energies if an intrinsic charm component is present in the proton wave function.

Advances in Light-Front QCD: Supersymmetric Properties of Hadron Physics from Light-Front Holography and Superconformal Algebra

A remarkable feature of QCD is that the mass scale $$\kappa $$ which controls color confinement and light-quark hadron mass scales does not appear explicitly in the QCD Lagrangian. However, de Alfaro, Fubini, and Furlan have shown that a mass scale can appear in the equations of motion without affecting the conformal invariance of the action if one adds a term to the Hamiltonian proportional to the dilatation operator or the special conformal operator. If one applies the same procedure to the light-front Hamiltonian, it leads uniquely to a confinement potential $$\kappa ^4 \zeta ^2$$ for mesons, where $$\zeta ^2$$ is the LF radial variable conjugate to the $$q \bar{q}$$ invariant mass. The same result, including spin terms, is obtained using light-front holography—the duality between the front form and AdS $$_5$$ , the space of isometries of the conformal group—if one modifies the action of AdS $$_5$$ by the dilaton $$e^{\kappa ^2 z^2}$$ in the fifth dimension z. When one generalizes this procedure using superconformal algebra, the resulting light-front eigensolutions predict a unified Regge spectroscopy of meson, baryon, and tetraquarks, including remarkable supersymmetric relations between the masses of mesons and baryons of the same parity. One also predicts observables such as hadron structure functions, transverse momentum distributions, and the distribution amplitudes defined from the hadronic light-front wavefunctions. The mass scale $$\kappa $$ underlying confinement and hadron masses can be connected to the parameter $$\Lambda _{\overline{MS}}$$ in the QCD running coupling by matching the nonperturbative dynamics to the perturbative QCD regime. The result is an effective coupling $$\alpha _s(Q^2)$$ defined at all momenta. The matching of the high and low momentum transfer regimes determines a scale $$Q_0$$ which sets the interface between perturbative and nonperturbative hadron dynamics. The use of $$Q_0$$ to resolve the factorization scale uncertainty for structure functions and distribution amplitudes, in combination with the principle of maximal conformality for setting the renormalization scales, can greatly improve the precision of perturbative QCD predictions for collider phenomenology. The absence of vacuum excitations of the causal, frame-independent front-form vacuum has important consequences for the cosmological constant. I also discuss evidence that the antishadowing of nuclear structure functions is non-universal; i.e., flavor dependent, and why shadowing and antishadowing phenomena may be incompatible with sum rules for nuclear parton distribution functions.

Strong form factor of delta (1232)

Our article is devoted to study of the D®Np decay. Strong decay D®Np is one of the best modes to search for particles with spin 3/2. Strong decay is dominating channel of decay, i.e. D - isobar decay consist of 99% - hadronic decay, 1% - electromagnetic decay, therefore the decay is important for nuclear research. We calculate relevant form factors in the framework of the covariant quark model with infrared confinement in the full kinematical momentum transfer region. The covariant quark model has been applied to a large number of elementary particle processes. This model can be viewed as an effective quantum field approach to hadronic interactions, which based on an interaction Lagrangian of hadrons interacting with their constituent quarks. The coupling strength is determined by the compositeness condition ZH = 0 where ZH is the renormalization constant of the hadron wave function. We compare the obtained results with available experimental data and the results from other theoretical approaches.

Hadron Wave Functions from Lattice QCD

I give a brief account of the status and perspectives of lattice calculations of the light-front wave functions at small transverse separations, usually referred to as hadron distribution amplitudes (DAs). The existing calculations indicate that the corrections to the asymptotic form of such distributions at large scales are rather small as compared to earlier model estimates. Lattice calculations also suggest an alternating pattern of such corrections for the nucleon resonances with increasing mass. Several recent results are discussed, including precise determination of the second moment of the pion DA, leading-twist DAs of the nucleon and \(N^*(1535)\), and the first calculation of the flavor-symmetry breaking corrections in the DAs of the baryon octet.

Hard hadronic diffraction is not hard

Hadronic diffractive processes characterized by a hard scale (hard diffraction) contain a nontrivial interplay of hard and soft, nonperturbative interactions, which breaks down factorization of short and long distances. On the contrary to the expectations based on the factorization hypothesis, assuming that hard diffraction is a higher twist, these processes should be classified as a leading twist. We overview various implications of this important observation for diffractive radiation of Abelian (Drell–Yan, gauge bosons, Higgs boson) and non-Abelian (heavy flavors) particles, as well as direct coalescence into the Higgs boson of the nonperturbative intrinsic heavy flavor component of the hadronic wave function.

Time reversal invariance violating and parity conserving effects in proton-deuteron scattering

Time reversal invariance violating and parity conserving effects for low-energy elastic neutron-deuteron scattering are calculated for meson exchange and effective field theory type potentials in a distorted wave-born approximation using realistic hadronic wave functions, obtained by solving three-body Faddeev equations in configuration space.

Novel quark smearing for hadrons with high momenta in lattice QCD

Hadrons in lattice QCD are usually created employing smeared interpolators. We introduce a new quark smearing that allows us to maintain small statistical errors and good overlaps of hadronic wavefunctions with the respective ground states, also at high spatial momenta. The method is successfully tested for the pion and the nucleon at a pion mass $m_{\pi}\approx 295$ MeV and momenta as high as 2.8 GeV. We compare the results obtained to dispersion relations and suggest further optimizations.

Erratum: Time reversal invariance violating and parity conserving effects in neutron-deuteron scattering [Phys. Rev. C84, 025501 (2011)

Time reversal invariance violating parity conserving (TVPC) effects are calculated for elastic proton deuteron scattering with proton energies up to $2~$MeV. Distorted Wave Born Approximation is employed to estimate TVPC matrix elements, based on hadronic wave functions, obtained by solving three-body Faddeev-Merkuriev equations in configuration space with realistic potentials.

Initial State Correlations and the Ridge

We point out that Bose enhancement in a hadronic wave function generically leads to correlations between produced particles. We show explicitly, by calculating the projectile density matrix in the Color Glass Condensate approach to high-energy hadronic collisions, that the Bose enhancement of gluons in the projectile leads to azimuthal collimation of long range rapidity correlations of the produced particles, the so-called ridge correlations.

Bose enhancement and the ridge

We point out that Bose enhancement in a hadronic wave function generically leads to correlations between produced particles. We show explicitly, by calculating the projectile density matrix in the Color Glass Condensate approach to high-energy hadronic collisions, that the Bose enhancement of gluons in the projectile leads to azimuthal collimation of long range rapidity correlations of the produced particles, the so-called ridge correlations.

Hadron wave functions as a probe of a two-color baryonic medium

The properties of the ground state of two-color QCD at non-zero baryon chemical potential $\mu$ present an interesting problem in strongly-interacting gauge theory; in particular the nature of the physically-relevant degrees of freedom in the superfluid phase in the post-onset regime $\mu>m_\pi/2$ still needs clarification. In this study we present evidence for in-medium effects at high $\mu$ by studying the wavefunctions of mesonic and diquark states using orthodox lattice simulation techniques, made possible by the absence of a Sign Problem for the model with $N_f=2$. Our results show that beyond onset the spatial extent of hadrons decreases as $\mu$ grows, and that the wavefunction profiles are consistent with the existence of a dynamically-gapped Fermi surface in this regime.

The application of light front holographic QCD to B physics

Light front holography is a formalism developed by Brodsky and de Téramond in which analytic forms for the hadronic bound state wavefunctions can be obtained. We have used the holographic light front wavefunctions thus obtained to calculate the distribution amplitudes of the light vector mesons ρ and K∗. As a result, we are able to calculate the form factors for B → ρ, K∗ transitions as well as ΛQCD/mb contributions in radiative B(s) → (ρ, K∗)γ decays. We compare our predictions to the available experimental data.

Perturbative QCD factorization ofργ⋆→π

In this paper, we firstly verify that the factorization hypothesis is valid for the exclusive process $\ensuremath{\rho}{\ensuremath{\gamma}}^{\ensuremath{\star}}\ensuremath{\rightarrow}\ensuremath{\pi}$ at the next-to-leading order (NLO) with the collinear factorization approach, and then extend this proof to the case of the ${k}_{T}$ factorization approach. We particularly show that at the NLO level, the soft divergences in the full quark level calculation could be canceled completely as for the $\ensuremath{\pi}{\ensuremath{\gamma}}^{\ensuremath{\star}}\ensuremath{\rightarrow}\ensuremath{\pi}$ process where only the pseudoscalar $\ensuremath{\pi}$ meson is involved, and the remaining collinear divergences can be absorbed into the NLO hadron wave functions. The full amplitudes can be factorized as the convolution of the NLO wave functions and the infrared-finite hard kernels with these factorization approaches. We also write out the NLO meson distribution amplitudes in the form of nonlocal matrix elements.

Light-front holographic QCD and color confinement

One of the most fundamental problems in Quantum Chromodynamics is to understand the origin of the mass scale which controls the range of color confinement and the hadronic spectrum. For example, if one sets the Higgs couplings of quarks to zero, then no mass parameters appear in the QCD Lagrangian, and the theory is conformal at the classical level. Nevertheless, hadrons have a finite mass. We show that a mass gap and a fundamental color confinement scale arise when one extends the formalism of de Alfaro, Fubini and Furlan (dAFF) to frame-independent light-front Hamiltonian theory. Remarkably, the resulting light-front potential has a unique form of a harmonic oscillator in the light-front invariant impact variable if one requires that the action remains conformally invariant. The result is a single-variable relativistic equation of motion for [Formula: see text] bound states, a "Light-Front Schrödinger Equation," analogous to the nonrelativistic radial Schrödinger equation, which incorporates color confinement and other essential spectroscopic and dynamical features of hadron physics, including a massless pion for zero quark mass and linear Regge trajectories with the same slope in the radial quantum number and orbital angular momentum. The same light-front equations with the correct hadron spin dependence arise from the holographic mapping of "soft-wall model" modification of AdS5 space with a specific dilaton profile. The corresponding light-front Dirac equation provides a dynamical and spectroscopic model of nucleons. A fundamental mass parameter κ appears, determining the hadron masses and the length scale which underlies hadron structure. Quark masses can be introduced to account for the spectrum of strange hadrons. This Light-Front Holographic approach predicts not only hadron spectroscopy successfully, but also hadron dynamics — hadronic form factors, the QCD running coupling at small virtuality, the light-front wavefunctions of hadrons, ρ electroproduction, distribution amplitudes, valence structure functions, etc. Thus the combination of light-front dynamics, its holographic mapping to gravity in a higher-dimensional space and the dAFF procedure provides new insight into the physics underlying color confinement, chiral invariance, and the QCD mass scale, among the most profound questions in physics.

Relevance of various Dirac covariants in hadronic Bethe-Salpeter wave functions in electromagnetic decays of ground state vector mesons

In this work we have employed Bethe-Salpeter equation (BSE) under covariant instantaneous ansatz (CIA) to study electromagnetic decays of ground state equal mass vector mesons: $\rho$, $\omega$, $\phi$, $\psi$ and $Y$ through the process $V\rightarrow\gamma*\rightarrow e^+ + e^-$. We employ the generalized structure of hadron-quark vertex function $\Gamma$ which incorporates various Dirac structures from their complete set order-by-order in powers of inverse of meson mass. The electromagnetic decay constants for the above mesons are calculated using the leading order (LO) and the next-to-leading order (NLO) Dirac structures. The relevance of various Dirac structures in this calculation is studied.

Scaling behavior in exclusive meson photoproduction from Jefferson Lab at large momentum transfers

With the availability of new high-statistics and wide-angle measurements for several exclusive non-$\ensuremath{\pi}N$ meson photoproduction channels from Jefferson Lab, we examine the fundamental scaling law of 90\ifmmode^\circ\else\textdegree\fi{} scattering in QCD that was originally derived in the high-energy perturbative limit. The data show scaling to be prominently visible even in the medium-energy domain of 2.5 GeV $\ensuremath{\lesssim}\sqrt{s}\ensuremath{\lesssim}2.84\text{ }\text{ }\mathrm{GeV}$, where $\sqrt{s}$ is the center-of-mass energy. While constituent quark exchange suffices for pseudoscalar mesons, additional gluon exchanges from higher Fock states of the hadronic wave functions appear be needed for vector-meson production. The case of the $\ensuremath{\phi}(1020)$, where two-gluon exchanges are known to dominate, is especially illuminating.

Rapidity resummation forB-meson wave functions

Transverse-momentum dependent (TMD) hadronic wave functions develop light-cone divergences under QCD corrections, which are commonly regularized by the rapidity $\zeta$ of gauge vector defining the non-light-like Wilson lines. The yielding rapidity logarithms from infrared enhancement need to be resummed for both hadronic wave functions and short-distance functions, to achieve scheme-independent calculations of physical quantities. We briefly review the recent progress on the rapidity resummation for $B$-meson wave functions which are the key ingredients of TMD factorization formulae for radiative-leptonic, semi-leptonic and non-leptonic $B$-meson decays. The crucial observation is that rapidity resummation induces a strong suppression of $B$-meson wave functions at small light-quark momentum, strengthening the applicability of TMD factorization in exclusive $B$-meson decays. The phenomenological consequence of rapidity-resummation improved $B$-meson wave functions is further discussed in the context of $B \to \pi$ transition form factors at large hadronic recoil.

Joint resummation for pion wave function and pion transition form factor

We construct an evolution equation for the pion wave function in the $k_T$ factorization theorem, whose solution sums the mixed logarithm $\ln x\ln k_T$ to all orders, with $x$ ($k_T$) being a parton momentum fraction (transverse momentum). This joint resummation induces strong suppression of the pion wave function in the small $x$ and large $b$ regions, $b$ being the impact parameter conjugate to $k_T$, and improves the applicability of perturbative QCD to hard exclusive processes. The above effect is similar to those from the conventional threshold resummation for the double logarithm $\ln^2 x$ and the conventional $k_T$ resummation for $\ln^2 k_T$. Combining the evolution equation for the hard kernel, we are able to organize all large logarithms in the $\gamma^{\ast} \pi^{0} \to \gamma$ scattering, and to establish a scheme-independent $k_T$ factorization formula. It will be shown that the significance of next-to-leading-order contributions and saturation behaviors of this process at high energy differ from those under the conventional resummations. It implies that QCD logarithmic corrections to a process must be handled appropriately, before its data are used to extract a hadron wave function. Our predictions for the involved pion transition form factor, derived under the joint resummation and the input of a non-asymptotic pion wave function with the second Gegenbauer moment $a_2=0.05$, match reasonably well the CLEO, BaBar, and Belle data.

Transition from soft to hard Pomeron in the structure functions of hadrons at smallxfrom holography

We study the nucleon and pion structure functions at the small Bjorken-$x$ region in the framework of holographic QCD with a special emphasis on the roles of anti-de Sitter (AdS) space wave functions. Using the Brower-Polchinski-Strassler-Tan kernel for the Pomeron exchange and calculating its coupling to target hadrons in the AdS space, we obtain ${F}_{2}$ structure functions at the small $x$. Results for the proton ${F}_{2}^{p}$ as well as the pion ${F}_{2}^{\ensuremath{\pi}}$ are consistent with experimental data of the deep inelastic scattering and the forward electroproduction of a neutron. Observed ${Q}^{2}$ dependence of the Pomeron intercept is well reproduced from soft nonperturbative $({Q}^{2}\ensuremath{\sim}0)$ to hard perturbative $({Q}^{2}\ensuremath{\gg}1\text{ }\text{ }{\mathrm{GeV}}^{2})$ region. We find the interplay between soft and hard Pomerons is closely related with behavior of AdS wave functions of hadrons and the virtual photon.

Azimuthal Collimation of Long Range Rapidity Correlations by Strong Color Fields in High Multiplicity Hadron-Hadron Collisions

The azimuthal collimation of dihadrons with large rapidity separations in high multiplicity p+p collisions at the LHC is described in the color glass condensate (CGC) effective theory [A. Dumitru, K. Dusling, F. Gelis, J. Jalilian-Marian, T. Lappi, and R. Venugopalan, Phys. Lett. B 697, 21 (2011).] by N(c)(2) suppressed multiladder QCD diagrams that are enhanced α(S)(-8) due to gluon saturation in hadron wave functions. We show that quantitative computations in the CGC framework are in good agreement with data from the CMS experiment on per trigger dihadron yields and predict further systematics of these yields with varying trigger p(T) and charged hadron multiplicity. Radial flow generated by rescattering is strongly limited by the structure of the p+p dihadron correlations. In contrast, radial flow explains the systematics of identical measurements in heavy ion collisions.