We study the scattering of the gluon-dressed physical quarks, defined as the eigenstates of the vacuum QCD Hamiltonian, off a colored medium. We solve the wave function of the physical quark state by diagonalizing the QCD Hamiltonian in vacuum in a <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mo stretchy="false">|</mo><mi>q</mi><mo stretchy="false">⟩</mo><mo>+</mo><mo stretchy="false">|</mo><mrow><mi>q</mi><mi>g</mi></mrow><mo stretchy="false">⟩</mo></math> Fock space, with implementing the sector-dependent mass renormalization scheme. We then perform numerical simulations of the real-time quantum state evolution of the initially dressed quark state at various medium densities. The results are compared with those of an initially bare or off-shell quark states. With the obtained light-front wave function of the evolved state, we extract the quark jet transverse momentum broadening, the quenching parameter, the cross section, the gluon emission rate, and the evolution of the invariant mass. The scenario considered is relevant for high energy scattering processes, where the quark originates from far outside the color field describing the scattering target. This investigation on dressed quarks complements our earlier studies of the single quark scattering in the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mo stretchy="false">|</mo><mi>q</mi><mo stretchy="false">⟩</mo></math> Fock space, and of the bare quark scattering in the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mo stretchy="false">|</mo><mi>q</mi><mo stretchy="false">⟩</mo><mo>+</mo><mo stretchy="false">|</mo><mrow><mi>q</mi><mi>g</mi></mrow><mo stretchy="false">⟩</mo></math> Fock space, providing a novel systematic description of quark scattering process using a nonperturbative formalism.

Spain

Meijian Li

Finland

Tuomas Lappi

China

Xingbo Zhao

Carlos A. Salgado

Scattering and gluon emission of physical quarks in a SU(3) colored field

We compute the differential cross section for inclusive <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi mathvariant="normal">D</mi><mn>0</mn></msup></math> production in ultraperipheral collisions within the color glass condensate framework. Our predictions are found to be in relatively good agreement with the compact muon solenoid data at small transverse momentum, which is the region of validity of our approach. Furthermore, we quantify saturation effects by a nuclear modification ratio <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>R</mi><mrow><mi>p</mi><mi>A</mi></mrow></msub></math> for <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi mathvariant="normal">D</mi><mn>0</mn></msup></math> photoproduction and examine both analytically and numerically the collinear factorization limit of the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi mathvariant="normal">D</mi><mn>0</mn></msup></math> differential photoproduction cross section.

Patricia Gimeno-Estivill

Heikki Mäntysaari

Inclusive <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>D</mi><mn>0</mn></msup></math> photoproduction in ultraperipheral collisions

We study the phenomenological impact of the preequilibrium glasma initial stage of heavy-ion collisions on heavy quark azimuthal correlations and spectra. Using our numerical solver, we simulate the transport of heavy quark test particles in an SU(3) glasma background field. The glasma field equations are formulated using classical real-time lattice gauge theory, and the heavy quark dynamics are described by classical transport equations numerically solved using the colored particle-in-cell method. For the first time, the effect of the glasma stage on the azimuthal correlations of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>c</mi><mover accent="true"><mrow><mi>c</mi></mrow><mrow><mo stretchy="false">¯</mo></mrow></mover></mrow></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>b</mi><mover accent="true"><mi>b</mi><mo stretchy="false">¯</mo></mover></math> pairs is studied. The resulting azimuthal width <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>σ</mi><mrow><mi mathvariant="normal">Δ</mi><mi>ϕ</mi></mrow></msub></math> exhibits a large and quick decorrelation due to the strong glasma fields. Further, we evaluate how the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>p</mi><mi>T</mi></msub></math>-broadening in the glasma affects heavy quark <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>p</mi><mi>T</mi></msub></math>-spectra, which are initialized according to the Fixed-Order Next-to-Leading Logarithm (FONLL) heavy quark production calculation. The nuclear modification factor <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>R</mi><mrow><mi>A</mi><mi>A</mi></mrow></msub></math> is extracted for <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>c</mi></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>b</mi></math> quarks in the glasma and additional nuclear PDF effects accounting for gluon shadowing are included.

Dana Avramescu

Italy

Vincenzo Greco

Austria

David Müller

Impact of glasma on heavy flavor azimuthal correlations and spectra

We use classical equations of motion for heavy quarks to show that the preequilibrium glasma phase of a heavy ion collision has an extremely strong effect on heavy quark angular correlations. At the same time the effect on the single inclusive spectrum is much more moderate. This suggests that <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>D</mi><mover accent="true"><mi>D</mi><mo stretchy="false">¯</mo></mover></math> meson angular correlations in future LHC measurements could provide a direct experimental access to the physics of the preequilibrium stage.

Heavy-Flavor Angular Correlations as a Direct Probe of the Glasma

We formulate and numerically solve the Dokshitzer–Gribov–Lipatov–Altarelli–Parisi (DGLAP) evolution equations at next-to-leading order in perturbation theory directly for a basis of 6 physical, observable structure functions in deeply inelastic scattering. By expressing the evolution in the physical basis one evades the factorization scale and scheme dependence. Working in terms of observable quantities, rather than parametrizing and fitting unobservable parton distribution functions (PDFs), provides an unambiguous way to confront predictions of perturbative Quantum Chromodynamics with experimental measurements. We compare numerical results for the DGLAP evolution for structure functions in the physical basis to the conventional evolution with PDFs.

Hannu Paukkunen

Mirja Tevio

Next-to-leading order evolution of structure functions without PDFs

Erratum: Evolution of structure functions in momentum space

We calculate the cross section for forward <math><mi>J</mi><mo>/</mo><mi>ψ</mi></math> production in proton-proton and minimum bias proton-lead collisions using the color glass condensate (CGC) and nonrelativistic QCD (NRQCD) formalism consistently with deep inelastic scattering data. The cross section for color singlet states is sensitive to a four-point correlator of Wilson lines for which we describe in the Gaussian approximation in the large-<math><msub><mi>N</mi><mi>c</mi></msub></math> limit. Furthermore, we quantify the importance of finite-<math><msub><mi>N</mi><mi>c</mi></msub></math> corrections to have a small <math><mo>∼</mo><mn>12</mn><mo>%</mo></math> effect. In contrast with the generic NRQCD expectation, we show that the color singlet contribution is only 15% to the total cross section. We also compare our predictions for <math><mi>J</mi><mo>/</mo><mi>ψ</mi></math> production as well as for the nuclear modification ratio <math><msub><mi>R</mi><mrow><mi>p</mi><mi>P</mi><mi>b</mi></mrow></msub></math> to LHCb and ALICE data. We find a good agreement at forward rapidities, except at low transverse momenta where the cross sections are overestimated.

Inclusive <math><mrow><mi>J</mi><mo>/</mo><mi>ψ</mi></mrow></math> production in forward proton-proton and proton-lead collisions at high energy

We compute the transverse and longitudinal diffractive structure functions to full next-to-leading order accuracy in the dipole picture of deep inelastic scattering. Our calculation uses the standard light-cone perturbation theory method for the partonic content of the virtual photon, together with the Color Glass Condensate description of the target color field. Our result includes as a subset the  $$q\overline{q }g$$  contribution calculated earlier. We show that there is a rapidity divergence that can be factorized into the BK/JIMWLK evolution of the target Wilson lines, and that all other divergences cancel.

Poland

Guillaume Beuf

Risto Paatelainen

United States

Jani Penttala

Diffractive deep inelastic scattering at NLO in the dipole picture

We formulate the momentum-space Dokshitzer–Gribov–Lipatov-Altarelli–Parisi (DGLAP) evolution equations for structure functions measurable in deeply inelastic scattering. We construct a six-dimensional basis of structure functions that allows for a full three flavor structure and thereby provides a way to calculate perturbative predictions for physical cross sections directly without unobservable parton distribution functions (PDFs) and without the associated scheme dependence. We derive the DGLAP equations to first non-zero order in strong coupling $$\alpha _\textrm{s}$$ , but the approach can be pursued to arbitrary order in perturbation theory. We also numerically check our equations against the conventional PDF formulation.

Evolution of structure functions in momentum space

We use the Kovchegov-Levin equation to resum contributions of large invariant mass diffractive final states to diffractive structure functions in the dipole picture of deep inelastic scattering. For protons we use a (modified) McLerran-Venugopalan model as the initial condition for the evolution, with free parameters obtained from fits to the HERA inclusive data. We obtain an adequate agreement to the HERA diffractive data in the moderately high-mass regimes when the proton density profile is fitted to the diffractive structure function data in the low-mass region. The HERA data is found to prefer a proton shape that is steeper than a Gaussian. The initial conditions are generalized to the nuclear case using the optical Glauber model. Strong nuclear modification effects are predicted in diffractive scattering off a nuclear target in kinematics accessible at the future Electron-Ion Collider. In particular, the Kovchegov-Levin evolution has a strong effect on the <math><msup><mi>Q</mi><mn>2</mn></msup></math>-dependence of the diffractive cross section.

Anh Dung Le

Rapidity gap distribution of diffractive small-<math><mrow><msub><mrow><mi>x</mi></mrow><mrow><mi>p</mi></mrow></msub></mrow></math> events at HERA and at the EIC