Ivan Schmidt

Universidad Técnica Federico Santa María · Department of Physics

In this paper we analyze the exclusive photoproduction of the D-meson pairs with large invariant mass. We perform evaluations in the collinear factorization framework and in the leading order of the strong coupling αs, expressing the cross section in terms of generalized parton distributions (GPDs) of different parton flavors in the proton. We focu...

We derive the equations of motion for the bulk-to-boundary propagators of the anti-de Sitter (AdS) boson and fermion fields with arbitrary total angular momentum J in a soft-wall AdS/QCD model and solve it analytically. It provides the opportunity to study transition form factors induced by these bulk-to-boundary propagators, both for on-shell and...

Heavy and light quarks produced in high-pT partonic collisions radiate differently. Heavy quarks regenerate their color field, stripped-off in the hard reaction, much faster than the light ones and radiate a significantly smaller fraction of the initial quark energy. This peculiar feature of heavy-quark jets leads to a specific shape of the fragmen...

We built an extended 2HDM theory with a spontaneously broken $U(1) _{X}$ global symmetry, where the tree level Universal Seesaw Mechanism generates the mass hierarchy of the Standard Model charged fermions and the Zee-Babu mechanism produces tiny active neutrino masses. The third family of SM charged fermions gets tree level masses from Yukawa inte...

A correction to this paper has been published: https://doi.org/10.1007/JHEP05(2023)054

Heavy and light quarks produced in high-$p_T$ partonic collisions radiate differently. Heavy quarks regenerate their color field, stripped-off in the hard reaction, much faster than the light ones and radiate a significantly smaller fraction of the initial quark energy. This peculiar feature of heavy-quark jets leads to a specific shape of the frag...

Heavy and light quarks produced in high-pT partonic collisions radiate differently. Heavy quarks regenerate their color field, stripped-off in the hard reaction, much faster than the light ones and radiate a significantly smaller fraction of the initial quark energy. This peculiar feature of heavy-quark jets leads to a specific shape of the fragmen...

The renormalization group equations of massive $\mathcal{N}=1$ supersymmetric quantum electrodynamics (SQED) are studied, using the functional renormalization group approach. Applying a supercovariant derivative expansion of the fields, we compute the non-perturbative beta function. In the local potential approximation, we verify the exact NSVZ $\b...

We derive the equations of motion for the bulk-to-boundary propagators of the AdS boson and fermion fields with arbitrary spin J in a soft-wall AdS/QCD model and solve it analytically. It provides the opportunity to study transition form factors induced by these bulk-to-boundary propagators, both for on-shell and off-shell hadrons. This is a contin...

In these proceedings we present our results on the exclusive photoproduction of $J/\psi\,\eta_{c}$ pairs in the collinear factorization framework. We argue that the process might be used as a complementary channel for studying the generalized parton distributions (GPDs) of gluons. We provide numerical estimates for the cross-section in the kinemati...

Nearly ten years ago, Kang, Ma, Qiu, and Sterman derived an evolution equation for a $Q\bar{Q}$ pair fragmenting into a quarkonium. In this study we explore the consequence of this evolution for the color-evaporation model, focusing on $J/\psi$ transverse-momentum ($p_t$) distributions in proton-proton collisions. We show that, as expected, it soft...

In this paper we analyze the photoproduction of heavy quarkonia pairs which include b -quarks, such as $$B_{c}^{+}B_{c}^{-}$$ B c + B c - -mesons or charmonium-bottomonium pairs. Compared to charmonia pair production, these channels get contributions only from some subsets of diagrams, and thus allow for a better theoretical understanding of differ...

We present a Left-Right symmetric model that provides an explanation for the mass hierarchy of the charged fermions within the framework of the Standard Model. This explanation is achieved through the utilization of both tree-level and radiative seesaw mechanisms. In this model, the tiny masses of the light active neutrinos are generated via a thre...

A bstract Quantum chromodynamics (QCD) rigorously predicts the existence of both nonperturbative intrinsic and perturbative extrinsic heavy quark contents of nucleons. In this article we discuss the heavy quark electroproduction on protons induced by the Fock states ∣ uud + g 〉 of three valence quarks in the proton and a nonperturbative gluon, and...

In this paper, we analyze the exclusive photoproduction of heavy quarkonia pairs in the collinear factorization framework. We evaluate the amplitude of the process for the J/ψ−ηc quarkonia pair in the leading order of the strong coupling αs, and express it in terms of generalized parton distributions (GPDs) of gluons in the proton. We make numerica...

We apply the functional renormalization group approach to a $$\mathcal {N}=1$$ N = 1 supersymmetric gauge model with one chiral superfield coupled to a vector U (1) superfield. We find that the nonrenormalization theorem still works at leading order in the supercovariant derivative expansion of the fields. We also find the beta functions and we stu...

In this paper we analyze the exclusive photoproduction of heavy quarkonia pairs in the collinear factorization framework. We evaluate the amplitude of the process for $J/\psi\,-\eta_{c}$ quarkonia pair in the leading order of the strong coupling $\alpha_{s},$ and express it in terms of generalized parton distributions (GPDs) of gluons in the proton...

Quantum chromodynamics (QCD) rigorously predicts the existence of both nonperturbative intrinsic and perturbative extrinsic heavy quark contents of nucleons. In this article we discuss the heavy quark electroproduction on protons induced by the Fock states $|uud+g\rangle$ of three valence quarks in the proton and a nonperturbative gluon, and the $|...

The anomalous excess of small-kT photons radiated along with multi-hadron production, is challenging the physics community over four decades, but no solution has been proposed so far. We argue that the problem is rooted in the comparison with an incorrect model, usually called bremsstrahlung model. It is believed to be an extension of the Low theor...

Quantum chromodynamics (QCD) predicts the existence of both nonperturbative intrinsic and perturbative extrinsic heavy quark contributions to the fundamental structure of hadrons. The existence of intrinsic charm at the 3-standard-deviation level in the proton has recently been established from structure function measurements by the NNPDF Collabora...

We apply the functional renormalization group approach to a $\mathcal{N}=1$ supersymmetric gauge model with one quiral superfield coupled to a vector $U(1)$ superfield. We find that the nonrenormalization theorem still works at leading order in the supercovariant derivative expansion of the fields. We also find the beta functions and we study the b...

The principle of maximum conformality (PMC) is used to remove uncertainties from the renormalization scale and the renormalization scheme, removing unnecessary systematic errors for high-precision pQCD predictions. In this paper, we will use PMC to improve the determination of the decay width of the W boson in hadrons, working the corrections comin...

The relation between the polar and running heavy quark masses to order $\mathcal{O}\left(\alpha_s^{4}\right)$ in perturbative quantum chromodynamics (pQCD) can be obtained with the help of the Principle of Maximum Conformity (PMC), which is a formalism that provides a rigorous method for eliminating renormalization scale and scheme ambiguities for...

Quantum chromodynamics (QCD) predicts the existence of both nonperturbative intrinsic and perturbative extrinsic heavy quark contributions to the fundamental structure of hadrons. The existence of intrinsic charm at the 3-standard-deviation level in the proton has recently been established from structure function measurements by the NNPDF collabora...

In this paper we analyze the photoproduction of heavy quarkonia pairs which include $b$-quarks, such as $B_{c}^{+}B_{c}^{-}$-mesons or charmonium-bottomonium pairs. Compared to charmonia pair production, these channels get contributions only from some subsets of diagrams, and thus allow for a better theoretical understanding of different production...

In this proceeding we discuss different mechanisms of open-heavy flavor meson production which contribute to inclusive and single diffractive cross-sections. For the case of inclusive production we demonstrate that the three-Pomeron fusion is significant for the D D -meson production in the kinematics of small transverse momenta p_{T} p T , as well...

A new approach to nonperturbative QCD, holographic light-front QCD, provides a comprehensive model for hadron dynamics and spectroscopy, incorporating color confinement, a universal hadron mass scale, the prediction of a massless pion in the chiral limit, and connections between the spectroscopy of mesons, baryons and tetraquarks across the full ha...

A new approach to nonperturbative QCD, holographic light-front QCD, provides a comprehensive model for hadron dynamics and spectroscopy, incorporating color confinement, a universal hadron mass scale, the prediction of a massless pion in the chiral limit, and connections between the spectroscopy of mesons, baryons and tetraquarks across the full ha...

In this paper we study the high-energy exclusive photoproduction of heavy quarkonia pairs in the leading order of the strong coupling constant αs. In the suggested mechanism, the quarkonia pairs are produced with opposite charge parities, and predominantly have oppositely directed transverse momenta. Using the Color Glass Condensate approach, we nu...

We focus on the chiral and heavy quark mass expansion of meson masses and decay constants. We propose a light-front QCD formalism for the evaluation of these quantities, consistent with chiral perturbation theory and heavy quark effective theory.

We focus on the chiral and heavy quark mass expansion of mesons masses and decay constants. We propose a light-front QCD formalism for the evaluation of these quantities, consistent with chiral perturbation theory and heavy quark effective theory.

In this paper we study the high energy exclusive photoproduction of heavy quarkonia pairs in the leading order of the strong coupling constant $\alpha_{s}$. In the suggested mechanism the quarkonia pairs are produced with opposite charge parities, and have predominantly oppositely directed transverse momenta. Using the Color Glass Condensate approa...

We propose a low scale renormalizable left-right symmetric theory that successfully explains the observed SM fermion mass hierarchy, the tiny values for the light active neutrino masses and is consistent with the lepton and baryon asymmetries of the Universe, the muon and electron anomalous magnetic moments as well as with the constraints arising f...

We build a renormalizable theory where the inverse seesaw mechanism explains the pattern of SM fermion masses. To the best of our knowledge, our model corresponds to the first implementation of the inverse seesaw mechanism for the charged fermion sector. In our theory, the inverse seesaw mechanism is implemented at the tree and one-loop levels in o...

The cross section for deep inelastic lepton-proton scattering (DIS) ℓp→ℓ′X includes a diffractive deep inelastic (DDIS) contribution ℓp→ℓ′p′X, in which the proton remains intact with a large longitudinal momentum fraction xF greater than 0.9 and small transverse momentum. The DDIS events, which can be identified with Pomeron exchange in the t-chann...

We address novel features of deep inelastic lepton scattering on nuclei at small Bjorken variable xBj. In this regime the lepton-nuclear cross section involves the interference between the standard lepton-quark scattering amplitude for the deep inelastic scattering (DIS) process on a single nucleon and a two-step process where diffractive scatterin...

We implement a minimal linear seesaw model (LSM) for addressing the Quasi-Dirac (QD) behaviour of heavy neutrinos, focusing on the mass regime of M N ≲ M W . Here we show that for relatively low neutrino masses, covering the few GeV range, the same-sign to opposite-sign dilepton ratio, Rℓ , can be anywhere between 0 and 1, thus signaling a Quasi-Di...

We address novel features of deep inelastic lepton scattering on nuclei at small Bjorken variable $x_{Bj}$. In this regime the lepton-nuclear cross section involves the interference between the standard lepton-quark scattering amplitude for the deep inelastic scattering (DIS) process on a single nucleon and a two-step process where diffractive scat...

A bstract We propose an extension of the three-Higgs-doublet model (3HDM), where the Standard Model (SM) particle content is enlarged by the inclusion of two inert SU 2 L scalar doublets, three inert and two active electrically neutral gauge singlet scalars, charged vector like fermions and Majorana neutrinos. These additional particles are introdu...

We build a renormalizable theory where the inverse seesaw mechanism explains the pattern of SM fermion masses. To the best of our knowledge, our model corresponds to the first implementation of the inverse seesaw mechanism for the charged fermion sector. In our theory, the inverse seesaw mechanism is implemented at the tree and one-loop levels in o...

In this paper, we study the electroproduction of open heavy flavor D and B mesons in the kinematics of future ep colliders, such as the Electron Ion Collider (EIC), the Large Hadron electron Collider (LHeC), and the Future Circular Collider (FCC-he). We study in detail the dependence of the cross sections on multiplicity of coproduced hadrons, in v...

In this paper we analyze in detail the production of strangeness in proton-proton collisions in the kinematics of large transverse momenta pT of produced hadrons. Using the color dipole framework, we estimate the production cross sections for kaons and demonstrate that the shapes of the pT dependence are in agreement with available experimental dat...

We analyze in detail the production of χc and χb mesons in pp collisions. Using the color dipole framework, we estimate the cross sections in the kinematics of ongoing and forthcoming experiments and find that our estimates are in reasonable agreement with currently available experimental data. We also analyze the dependence on multiplicity of copr...

We revisit the model-independent decomposition of the gluon correlator, producing T-even and T-odd gluon transverse momentum distributions (TMDs), at leading twist. We propose an expansion of the gluon correlator, using a basis of four tensors (one antisymmetric and three symmetric), which are expressed through generators of the U(2) group acting i...

In this proceeding we analyze possible mechanisms of quarkonia and open-heavy flavor meson production. We study in detail the contributions of the leading twist two-pomeron fusion and higher twist corrections due to three-pomeron fusion. We show that the latter mechanism is significant for charm production at small transverse momenta. We demonstrat...

A bstract We implement a minimal linear seesaw model (LSM) for addressing the Quasi-Dirac (QD) behaviour of heavy neutrinos, focusing on the mass regime of M N ≲ M W . Here we show that for relatively low neutrino masses, covering the few GeV range, the same-sign to opposite-sign dilepton ratio, R ℓℓ , can be anywhere between 0 and 1, thus signalin...

We revisit the model-independent decomposition of the gluon correlator, producing T even and T odd gluon transverse momentum distributions (TMDs), at leading twist-2. We propose an expansion of the gluon correlator, using a basis of four tensors (one antisymmetric and three symmetric), which are expressed through generators of the $U(2)$ group acti...

We study the gluon parton densities [parton distribution functions (PDFs), transverse momentum distributions (TMDs), generalized parton distributions (GPDs)] and form factors in soft-wall AdS/QCD. We show that the power behavior of gluon parton distributions and form factors at large values of the light-cone variable and large values of square mome...

The cross section for deep inelastic lepton-proton scattering (DIS) $\ell p \to \ell' X$ includes a diffractive deep inelastic (DDIS) contribution $\ell p \to \ell' p' X$, in which the proton remains intact with a large longitudinal momentum fraction $x_F$ greater than 0.9 and small transverse momentum. The DDIS events, which can be identified with...

We implement a minimal linear seesaw model (LSM) for addressing the Quasi-Dirac (QD) behaviour of heavy neutrinos, focusing on the mass regime of $M_{N} \lesssim M_{W}$. Here we show that for relatively low neutrino masses, covering the few GeV range, the same-sign to opposite-sign dilepton ratio, $R_{\ell \ell}$, can be anywhere between 0 and 1, t...

We propose an extension of the three-Higgs-doublet model (3HDM), where the Standard Model (SM) particle content is enlarged by the inclusion of two inert $SU(2)$ scalar doublets, two inert electrically neutral gauge singlet scalars, charged vector like fermions and Majorana neutrinos. These additional particles are introduced to generate the SM fer...

In this paper we study the electroproduction of open heavy flavor $D$- and $B$-mesons in the kinematics of future $ep$ colliders, such as the Electron Ion Collider (EIC), the Large Hadron electron Collider (LHeC) and the Future Circular Collider (FCC-he). We study in detail the dependence of the cross-sections on multiplicity of co-produced hadrons...

We propose a low scale renormalizable left-right symmetric theory that successfully explains the observed SM fermion mass hierarchy, the tiny values for the light active neutrino masses, the lepton and baryon asymmetries of the Universe, as well as the muon and electron anomalous magnetic moments. In the proposed model the top and exotic quarks obt...

In this paper we analyze in detail the production of strangeness in proton-proton collisions in the kinematics of large transverse momenta $p_{T}$ of produced hadrons. Using the color dipole framework, we estimated the production cross-sections for kaons, and demonstrated that the shapes of the $p_{T}$-dependence are in agreement with available exp...

In this paper we analyze in detail the production of the $\chi_{c}$ and $\chi_{b}$ mesons in $pp$ collisions. Using the color dipole framework, we estimated the cross-sections in the kinematics of ongoing and forthcoming experiments, and found that our estimates are in reasonable agreement with currently available experimental data. We also analyze...

We study the gluon parton densities [parton distribution functions (PDFs), transverse momentum distributions (TMDs), generalized parton distributions (GPDs)] and form factors in soft-wall AdS/QCD. We show that the power behavior of gluon parton distributions and form factors at large values of the light-cone variable and large values of square mome...

Hidden-color configurations are a key prediction of QCD with important physical consequences. In this work we examine a QCD color-singlet configuration in nuclei formed by combining six scalar [ud] diquarks in a strongly bound SU(3)C channel. The resulting hexadiquark state is a charge-2, spin-0, baryon number-4, isospin-0, color-singlet state. It...

We present a study of electroexcitation of nucleon resonances with higher spins, in a soft-wall AdS/QCD model, comparing our results with existing data from the CLAS Collaboration at JLab, from MAMI, and other experiments.

We propose a low-scale renormalizable trinification theory that successfully explains the flavor hierarchies and neutrino puzzle in the Standard Model (SM), as well as provides a dark matter candidate and also contains the necessary means for efficient leptogenesis. The proposed theory is based on the trinification SU(3)C×SU(3)L×SU(3)R gauge symmet...

In this paper, we discuss the single diffractive production of open heavy flavor mesons and nonprompt charmonia in pp collisions. Using the color dipole approach, we found that the single diffractive production constitutes 0.5%–2% of the inclusive production of the same mesons. In Tevatron kinematics, our theoretical results are in reasonable agree...

We present a study of electroexcitation of nucleon resonances with higher spins, in a soft-wall AdS/QCD model, comparing our results with existing data from the CLAS Collaboration at JLab, from MAMI, and other experiments.

In this paper we discuss the single diffractive production of open heavy flavor mesons and non-prompt charmonia in $pp$ collisions. Using the color dipole approach, we found that the single diffractive production constitutes 0.5-2 per cent of the inclusive production of the same mesons. In Tevatron kinematics our theoretical results are in reasonab...

We explicitly demonstrate how to correctly define the hadronic parton distributions [parton distribution functions (PDFs), transverse-momentum-dependent parton distribution functions, and generalized parton distributions] in the soft-wall anti–de Sitter/QCD approach, based on the use of a quadratic dilaton field, providing confinement and breaking...

We propose a systematic and renormalizable sequential loop suppression mechanism to generate the hierarchy of the Standard Model fermion masses from one discrete symmetry. The discrete symmetry is sequentially softly broken in order to generate one-loop level masses for the bottom, charm, tau and muon leptons and two-loop level masses for the light...

In the paper we develop, in the CGC approach, a new mechanism for quarkonia production in events with high multiplicity of the soft produced particles. In this mechanism both \(J/\varPsi \) and soft hadrons are produced at short distances \(r\, \propto \,1/Q_s\), where \(Q_s\) is the saturation scale, which is considered to be proportional to the m...

In this paper we discuss different mechanisms of open-heavy flavor meson production. Using the color dipole framework, we analyze in detail the contributions of the conventional two-Pomeron fusion and the three-Pomeron fusion correction. In a parameter-free way we found that the three-Pomeron mechanism is significant for D-meson production in the s...

We explicitly demonstrate how to correctly define the hadronic parton distributions (PDFs, TMDs, and GPDs) in the soft-wall AdS/QCD approach, based on the use of a quadratic dilaton field, providing confinement and spontaneous breaking of conformal and chiral symmetries. The power behavior of parton distributions at large values of the light-cone v...

A central feature of deep inelastic lepton-nucleus scattering is the EMC effect, a distortion of quark distributions within nuclei in the domain $0.3 < x_{B} < 0.7$, first measured by the European Muon Collaboration in 1983. The CLAS collaboration recently compared nuclear parton distribution functions for a large range of nuclei and confirmed that...

We propose a low scale renormalizable trinification theory that successfully explains the flavour hierarchies, neutrino puzzle, dark matter and leptogenesis. The proposed theory is based on the $SU(3)_{C}\times SU\left(3\right)_{L}\times SU\left( 3\right)_{R}$ gauge symmetry, which is supplemented with an additional flavor symmetry $U\left( 1\right...

The CLAS collaboration at Jefferson Laboratory has compared nuclear parton distributions for a range of nuclear targets and found that the EMC effect measured in deep inelastic lepton-nucleus scattering has a strongly “isophobic” nature. This surprising observation suggests short-range correlations between neighboring n and p nucleons in nuclear wa...

In this paper we discuss different mechanisms of open-heavy flavor meson production. Using the color dipole framework, we analyze in detail the contributions of the conventional two-pomeron fusion and the three-pomeron fusion correction. In a parameter-free way we found that the three-pomeron mechanism is significant for $D$-meson production in the...

We apply the functional renormalization group equation to a massive Fierz-Pauli action in curved space and find that, even though a massive term is a modification in the infrared sector, the mass term modifies the value of the non-gaussian fixed point in the UV sector.We obtained the beta function for the scale dependent mass parameter and found th...

High-multiplicity pp collisions exhibit features, traditionally associated with nuclear effects. Coherence motivates to treat high-multiplicity pp, pA, and AA collisions on an equal footing. We rely on the phenomenological parametrization for mean multiplicities of light hadrons and J/ψ, assuming their linear dependence on Ncoll in pA collisions. T...

Knowledge of the mechanism of neutrino mass generation would help understand a lot more about Lepton Number Violation (LNV), the cosmological evolution of the Universe, or the evolution of astronomical objects. Here we propose a verifiable and viable extension of the Standard model for neutrino mass generation, with a low-scale seesaw mechanism via...

We present a study of the nucleon electromagnetic form factors and of the Roper-nucleon transition at finite small temperature T, using an extended version of a soft-wall AdS/QCD approach developed by us previously. In the action we introduce the effective potential, which has quadratic dependence on the holographic coordinate z and depends on both...

We apply the functional renormalization group equation to a massive Fierz–Pauli action in curved space and find that, even though a massive term is a modification in the infrared sector, the mass term modifies the value of the non-gaussian fixed point in the UV sector. We obtained the beta function for the scale dependent mass parameter and found t...

We present a study of the N*(1535) resonance electroexcitation in a soft-wall AdS/QCD model. Both the transverse A1/2p and longitudinal S1/2p helicity amplitudes are calculated resulting in good agreement with data and with the MAID parametrization.

The CLAS collaboration at Jefferson Laboratory has compared nuclear parton distributions for a range of nuclear targets and found that the EMC effect measured in deep inelastic lepton-nucleus scattering has a strongly "isophobic" nature. This surprising observation suggests short-range correlations between neighboring $n$ and $p$ nucleons in nuclea...

We propose a systematic and renormalizable sequential loop suppression mechanism to generate the hierarchy of the Standard Model fermion masses from one discrete symmetry. The discrete symmetry is sequentially softly broken in order to generate one-loop level masses for the bottom, charm, tau and muon leptons and two-loop level masses for the light...

We present a study of the $N^*(1535)$ resonance electroexcitation in a soft-wall AdS/QCD model. Both the transverse $A_{1/2}^p$ and longitudinal $S_{1/2}^p$ helicity amplitudes are calculated resulting in good agreement with data and with the MAID parametrization.

In this paper we demonstrate that the vigorously growing multiplicity distributions measured by STAR and ALICE present a strong evidence in favor of multigluon fusion mechanisms of the quarkonia production in CGC approach. We analyze the contribution of 3-gluon fusion mechanism and demonstrate that it gives a sizeable contribution to quarkonia yiel...

We propose a verifiable and viable extension of the Standard model for neutrino mass generation, with a low-scale seesaw mechanism via LNV condensation in the sector of sterile neutrinos. To prove the concept, we analyze a simplified model of a single family of fermions and check it against a set of phenomenological constraints coming from electrow...

High-multiplicity pp collisions exhibit features, traditionally associated with nuclear effects. Coherence motivates to treat high-multiplicity pp, pA and AA collisions on an equal footing. We rely on the phenomenological parametrization for mean multiplicities of light hadrons and J/psi, assuming their linear dependence on N_{coll} in pA collision...