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Michael Fucilla

Publications and source records attributed to Michael Fucilla.

At least 37 records · Page 2Linked to original sources
arXiv2024

Twist corrections to exclusive vector meson production in a saturation framework

We develop a framework combining the higher-twist formalism of exclusive processes in the $s$ channel with the semi-classical effective description of small-$x$ physics in the $t$ channel. We apply it to transversely polarized light vector meson production, $γ^{*} p \rightarrow V (ρ, φ,ω) \; p$, which starts at the next-to-leading power and for which a purely collinear treatment leads to end-point singularities. The result is obtained in the most general kinematics, including both forward and non-forward cases by preserving the full impact parameter dependence in the non-perturbative correlators, in both momentum and coordinate space representations. A systematic expansion of the Wilson lines in terms of Reggeized gluon fields is performed in order to obtain the results in the weak-field BFKL approximation. These new results will allow for investigating the dilute-to-dense regime transition of QCD for a wide class of observables.

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arXiv2024

Probing gluonic saturation in deeply virtual meson production beyond leading power

Exclusive diffractive meson production represents a golden channel for investigating gluonic saturation inside nucleons and nuclei. In this letter, we settle a systematic framework to deal with beyond leading power corrections at small-$x$, including the saturation regime, and obtain the $γ^{*} \rightarrow M (ρ, ϕ, ω)$ impact factor with both incoming photon and outgoing meson carrying arbitrary polarizations. This is of particular interest since the saturation scale at modern colliders, although entering a perturbative regime, is not large enough to prevents higher-twist effects to be sizable.

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arXiv2024

The next-to-leading order Higgs impact factor at physical top mass: The real corrections

We compute the real corrections to the impact factor for the production of a forward Higgs boson, retaining full top-mass dependence. We demonstrate that the rapidity divergence is the one predicted by the BFKL factorization and perform the explicit subtraction in the BFKL scheme. We show that the IR-structure of the impact factor is the expected one and that, in the infinite-top-mass approximation, the previously known result is recovered. We also verify that the impact factor vanishes when the transverse momenta of the $t$-channel Reggeon goes to zero, in agreement with its gauge-invariant definition, exploiting the $m_t \rightarrow \infty$ expansion up to the next-to-next-to-leading order.

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arXiv2024

Gluon tomography through diffractive processes in a saturation framework

We discuss a series of results aimed at bringing saturation physics and gluon tomography into an era of precision. In particular, the NLO treatment of diffractive: 1) exclusive dijet, 2) exclusive longitudinally polarized light vector meson and 3) semi-inclusive single or double hadron photo- or electroproduction with large $p_T$, on a nucleon or a nuclei. Finally, we discuss the more complicated 4) exclusive transversely polarized light vector meson production, which starts at the next-to-leading power and therefore requires a beyond leading twist treatment. This new class of processes provides an access to precision physics of gluon saturation dynamics, with very promising future phenomenological studies at the EIC, or, at the LHC in $p A$ and $A A$ scattering, using Ultra Peripheral Collisions (UPC).

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arXiv2024

Higgs production at NLL accuracy in the BFKL approach

Precision physics in the Higgs sector has been one of the main challenges of particle physics in the recent years. The pure fixed-order calculations entering the collinear factorization framework, which have been pushed up to next-cube-leading-order, are not able to describe the entire kinematic spectrum. In particular sectors, they have to be necessarily enhanced by all-order resummations. In the so-called semi-hard regime, large energy-type logarithms spoil the perturbative convergence of the series and must be resummed to all orders. This resummation is a core ingredient for a correct description of the inclusive hadroproduction of a forward Higgs boson in the limit of small Bjorken $x$, as well as for a precision study of inclusive forward emissions of a Higgs boson in association with a backward identified object. A complete resummation for these processes can be achieved at the at next-to-leading logarithmic accuracy thanks to the Balitsky-Fadin-Kuraev-Lipatov approach. In the present work we present and discuss a series of recent phenomenological results within a partial next-to-leading accuracy. They include the analysis of rapidity and azimuthal-angle differential rates for Higgs plus jet and Higgs plus charm reactions in forward and ultraforward directions of rapidity at the LHC.

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arXiv2024

Towards Higgs and $Z$ boson plus jet distributions at NLL/NLO$^+$

We present novel predictions for rapidity and transverse-momentum distributions sensitive to the emission of a Higgs boson accompanied by a jet in proton collisions, calculated within the NLO fixed order in QCD and matched with the next-to leading energy-logarithmic accuracy. We also highlight first advancements in the extension of our analysis to the $Z$-boson case. We come out with the message that the improvement of fixed-order calculations on Higgs- and $Z$-boson plus jet distributions is a required step to reach the precision level of the description of observables relevant for Higgs and electroweak physics at current LHC energies and nominal FCC ones.

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arXiv2024

On the breakdown of eikonal approximation and survival of Reggeization in presence of dimension-5 Higgs-gluon coupling

We consider the one-loop effective vertex for the interaction of a gluon with a Reggeized gluon and a Higgs boson in the infinite-top-mass limit, which is described by a dimension-5 non-renormalizable operator. This vertex enters the calculation of differential cross sections for the forward inclusive production of a Higgs boson in high-energy proton-proton collisions, possibly in association with a backward jet or identified hadron, in a framework where next-to-leading logarithms of the energy are resummed to all orders. The effective vertex is extracted from the high-energy behavior of two-to-two amplitudes for the Higgs production in parton-parton collisions and relies on the validity of the Regge form for these amplitudes. We find that the usual eikonal approximation (Gribov prescription) for the Regge limit and the known region-expansion technique in this limit lead to an incomplete result for the amplitude. The discrepancy is traced back to the non-renormalizable nature of the involved operator. However, the Regge limit of the exact QCD amplitude agrees with the Regge-pole exchange form at one loop, nontrivially supporting the Reggeization hypothesis.

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arXiv2024

Diffractive single hadron production in a saturation framework at the NLO

We calculate the cross-sections of diffractive single hadron photo- or electroproduction with large $p_T$, on a nucleon or a nucleus in the shockwave formalism. We use the hybrid formalism mixing collinear factorization with high energy small-$x$ factorization with the impact factors computed at next-to-leading order accuracy. We prove the cancellation of divergence and we determine the finite parts of the differential cross-sections. We work in general kinematics such that both photoproduction and leptoproduction are considered. The results can be used to detect saturation effects, at both the future EIC or already at LHC, using Ultra-Peripheral Collisions.

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arXiv2024

One-loop Lipatov vertex in QCD with higher $ε$-accuracy

The effective Reggeon-Reggeon-gluon vertex, known as Lipatov vertex, is the key ingredient that allows to develop the BFKL approach in QCD. Within the next-to-leading logarithmic approximation, it is sufficient to know its one-loop corrections, in dimensional regularization ($D=4+2ε$), up to the constant term in the $ε$-expansion. In the next-to-next-to-leading approximation, however, the one-loop Lipatov vertex is needed up to the order $ε^2$. In this paper we present the expression for this vertex in dimensional regularization up to the required accuracy.

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arXiv2023

Towards high-energy Higgs+jet distributions at NLL matched to NLO

We report progress on the study of the inclusive semi-hard hadroproduction of a Higgs+jet system at LHC and FCC collision energies. We describe a prototype matching procedure aimed at combining NLO fixed-order computations via POWHEG, with the NLL resummation of energy logarithms from JETHAD. We present preliminary analyses on assessing the weight of systematic uncertainties, such as the ones coming from finite top- and bottom-quark masses.

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arXiv2023

NLL/NLO$^-$ studies on Higgs-plus-jet production with POWHEG+JETHAD

We consider the semi-inclusive emission of a Higgs boson in association with a light-flavored jet separated by a large rapidity interval at the LHC. The accessed kinematic regimes fall into the so-called semi-hard sector, whose theoretical description lies at the intersection corner between the collinear factorization and the high-energy resummation. We present a prototype version of a matching procedure aimed at combining next-to-leading fixed-order (NLO) calculations from POWHEG with the resummation of next-to-leading energy logarithms (NLL) as obtained from JETHAD.

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arXiv2023

Probing the high-energy dynamics of QCD: selected theoretical and phenomenological studies

The center-of-mass energies available at modern accelerators, such as the Large Hadron Collider (LHC), and at forthcoming generation accelerators, such as the Electron-Ion Collider (EIC), offer us a unique opportunity to investigate hadronic matter under the most extreme conditions ever reached. In particular, we can access the Regge-Gribov regime of QCD, described by the Balitsky-Fadin-Kuraev-Lipatov (BFKL) approach along with its non-linear generalizations (the set of B-JIMWLK equations). The aim of these approaches is to resum large-energy logarithmic corrections which spoil the convergence of perturbative series at high-energy. The aforementioned approaches are theoretically developed both in the leading (LL) and the next-to-leading (NLL) approximation, but precise full NLL predictions still remains an open challenge. Furthermore, extending BFKL beyond the NLL approximation has been an open problem for more than twenty years. We face the task of hunting precision in this field from different perspectives. In particular, within the BFKL approach, we calculate the next-to-leading order (NLO) impact factor for the Higgs boson production. This is the necessary ingredient to study the inclusive forward emissions of a Higgs boson in association with a backward identified jet. Moreover, by using already known NLO impact factors, we propose a series of new semi-hard reactions that can be used to investigate BFKL dynamics at the LHC within NLL accuracy. We consider also the problem of extending BFKL beyond the NLL approximation and compute one of the ingredients entering the BFKL kernel at the next-to-NLL (NNLL) accuracy. Finally, in the saturation (non-linear) framework, we calculate the diffractive double hadron photo- or electroproduction cross sections with full NLL accuracy, useful to detect saturation effects, at both the future EIC or already at LHC (via Ultra Peripheral Collisions).

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arXiv2023

Higgs boson production at next-to-leading logarithmic accuracy

It has been recently argued that the inclusive hadroproduction at the LHC of a Higgs boson in association with a jet can be sensitive to the high-energy dynamics. Moreover, the impact of the resummation at FCC energies is expected to be large also in the inclusive cross section for the main Higgs production channel in proton-proton collisions, namely the gluon fusion. As the energy increases, a pure $k_t$-factorization framework or a collinear-factorization approach supplemented by the high-energy resummation are adequate formalisms to describe these processes. In both cases, the fundamental missing ingredient for a next-to-leading logarithmic description is the Higgs boson impact factor. We present the full next-to-leading result for the forward Higgs impact factor, obtained in the infinite top-mass limit, discussing possible future extensions, such as the calculation of the impact factor in the central rapidity region.

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arXiv2023

High-energy resummed Higgs-plus-jet distributions at NLL/NLO* with POWHEG+JETHAD

We study the inclusive production, at hadron colliders, of a Higgs boson and a jet widely separated in rapidity. Kinematic sectors explored fall into the so-called semi-hard regime, where both fixed-order and high-energy dynamics come into play. Therefore, we propose a first version of a matching procedure aimed at combining NLO fixed-order computations, as obtained from POWHEG, with the NLL resummation of energy logarithms via JETHAD. According to our knowledge, this represents a novel implementation of a matching in the context of the high-energy resummation at NLL and for rapidity-separated two-particle final states.

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arXiv2023

The high-energy limit of perturbative QCD: Theory and phenomenology

After a brief introduction of formal and phenomenological progresses in the study of the high-energy limit of perturbative QCD, we present arguments supporting the statement that the inclusive emission of Higgs bosons or heavy-flavored hadrons acts as fair stabilizer of high-energy resummed differential distributions. We come out with the message that the hybrid high-energy and collinear factorization, built in term of the next-to-leading logarithmic resummation \emph{à la} BFKL and supplemented by collinear parton distributions and fragmentation functions, is a valid and powerful tool to gauge the feasibility of precision analyses of QCD in its high-energy limit.

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arXiv2022

NLO computation of diffractive di-hadron production in a saturation framework

The cross-sections of diffractive double hadron photo- or electroproduction with large $p_T$, on a nucleon or a nucleus, are calculated to NLO accuracy. A hybrid formalism mixing collinear factorization and high energy small-$x$ factorization, more precisely the shockwave formalism for the latter, is used to derive the results. The cancellation of divergences is explicitly shown, and the finite parts of the NLO differential cross-sections are found. We work in arbitrary kinematics such that both photoproduction and leptoproduction are considered. The results are therefore usable, to detect saturation effects, at both the future EIC or already at LHC, using Ultra Peripheral Collisions.

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