Probing subnucleon scale fluctuations in ultraperipheral heavy ion collisions

We show that introducing subnucleon scale fluctuations constrained by HERA diffractive $J/\Psi$ production data significantly affects the incoherent diffractive $J/\Psi$ production cross section in ultraperipheral heavy ion collisions. We find that the inclusion of the additional fluctuations increases the ratio of the incoherent to the coherent cross section approximately by a factor of $2$, and modifies the transverse momentum spectra of the produced $J/\Psi$ at momenta larger than the scale that corresponds to the distance scale of the subnucleonic fluctuations. We present predictions for $J/\Psi$ production in ultraperipheral heavy ion collisions at $\sqrt{s_{NN}}=5.02\,{\rm TeV}$ at the LHC and $200\,{\rm GeV}$ at RHIC.Comment: 9 pages, 8 figures. v2: small clarifications to the text, matches the published versio

Diffractive scattering at next-to-leading order in the dipole picture

We discuss recent developments towards next-to-leading order (NLO) accuracy in the dipole picture. We review recent NLO results for exclusive vector meson production and diffractive structure functions, and discuss how it is becoming possible to describe both inclusive and exclusive DIS data simultaneously within the Color Glass Condensate framework at NLO accuracy. These developments will make it possible to probe the gluon saturation phenomena in detail especially when nuclear-DIS data from the EIC become available.Comment: 8 pages, 4 figures, contribution to the proceedings of the XXIX Cracow Epiphany Conferenc

Accessing the gluonic structure of light nuclei at a future electron-ion collider

We show how exclusive vector meson production off light ions can be used to probe the spatial distribution of small-x gluons in the deuteron and 3He wave functions. In particular, we demonstrate how short-range repulsive nucleon-nucleon interactions affect the predicted coherent J/Ψ production spectra. Fluctuations of the nucleon substructure are shown to have a significant effect on the incoherent cross section above |t|≳0.2GeV2. By explicitly performing the Jalilian-Marian–Iancu–McLerran–Weigert–Leonidov–Kovner (JIMWLK) evolution, we predict the x dependence of coherent and incoherent cross sections in the electron-ion collider energy range. In addition to the increase of the average size of the nucleus with decreasing x, both the growth of the nucleons and subnucleonic hot spots are visible in the cross sections. The decreasing length scale of color charge fluctuations with decreasing x is also present, but may not be observable for |t|<1GeV2, if subnucleonic spatial fluctuations are present.We show how exclusive vector meson production off light ions can be used to probe the spatial distribution of small-x gluons in the deuteron and He-3 wave functions. In particular, we demonstrate how short-range repulsive nucleon-nucleon interactions affect the predicted coherent J/Psi production spectra. Fluctuations of the nucleon substructure are shown to have a significant effect on the incoherent cross section above vertical bar t vertical bar greater than or similar to 0.2 GeV2. By explicitly performing the Jalilian-Marian-Iancu-McLerran-Weigert-Leonidov-Kovner (JIMWLK) evolution, we predict the x dependence of coherent and incoherent cross sections in the electron-ion collider energy range. In addition to the increase of the average size of the nucleus with decreasing x, both the growth of the nucleons and subnucleonic hot spots are visible in the cross sections. The decreasing length scale of color charge fluctuations with decreasing x is also present, but may not be observable for vertical bar t vertical bar <1 GeV2, if subnucleonic spatial fluctuations are present.Peer reviewe

Energy and system size dependence of subnucleonic fluctuations

The energy evolution of the fluctuating proton structure is studied by solving the JIMWLK renormalization group equation. The initial condition at moderate $x$ is obtained by fitting the charm reduced cross section data from HERA, requiring that the proton size remains compatible with the diffractive vector meson production measurements. Additionally, we show that the nucleon shape fluctuations are visible in exclusive vector meson production off nuclei.Comment: 4 pages, 4 figures. Quark Matter 2018 proceeding

Saturation and forward jets in proton-lead collisions at the LHC

We investigate the forward-jet energy spectrum within the color glass condensate framework at 5 TeV center-of-mass energy. In particular, we focus on the kinematic range covered by the CMS-CASTOR calorimeter. We show that our saturation-model calculations are compatible with the CASTOR measurements and that to optimally reproduce the data, effects of multiparton interactions need to be included. We predict a significant nuclear suppression-reaching down to 50% at the lowest considered jet energies E-jet similar to 500 GeV.Peer reviewe

Exclusive production of light vector mesons at next-to-leading order in the dipole picture

Exclusive production of light vector mesons in deep inelastic scattering is calculated at next-to-leading order in the dipole picture in the limit of high photon virtuality. The resulting expression is free of any divergences and suitable for numerical evaluations. The higher-order corrections are found to be numerically important, but they can be mostly captured by the nonperturbative fit parameters describing the initial condition for the small-x evolution of the dipole scattering amplitude. The vector meson production cross section is shown to depend only weakly on the meson distribution amplitude and the factorization scale. We also present phenomenological comparisons of our result to the existing exclusive ?? and ?? production data from HERA and find an excellent agreement at high virtualities.Peer reviewe

Complete Next-to-Leading Order Calculation of Single Inclusive π0\pi^0 Production in Forward Proton-Nucleus Collisions

We present the first fully consistent calculation of inclusive $\pi^0$ production at forward rapidities at next-to-leading order (NLO) accuracy in proton-lead collisions at $\sqrt{s}=8.16$ TeV within the Color Glass Condensate (CGC) approach. The center-of-mass energy dependence is determined by the Balitsky-Kovchegov (BK) equation with the initial condition constrained at NLO accuracy by the proton structure function measurements. We find that the LHCb data further constrain this non-perturbative input, and that both the NLO corrections to the evolution equation and to the impact factor have significant effects on the nuclear modification factor $R_{p\mathrm{Pb}}$. The complete NLO calculation is shown to be in qualitative agreement with the LHCb data, and the predictions are found to be sensitive to the details of the applied DIS fit. These results demonstrate the need to perform global analyses of DIS and LHC data in order to probe gluon saturation phenomena at precision level at very small momentum fraction $x$.Comment: 15 pages, 8 figure