UPC2025: The second international workshop on the physics of Ultra Peripheral Collisions

Session

Inclusive and diffractive processes and photon, proton and nuclear structure

12 Jun 2025, 09:00

Saariselkä, Finland

54. Probing the proton’s correlated spatial structure through UPCs

Prof. liuti simonetta

12/06/2025, 09:00

Inclusive and diffractive processes and photon, proton and nuclear structure

Generalized parton distributions (GPDs), probed through exclusive processes like deeply virtual Compton scattering, serve as indispensable tools in filling in the gaps of the angular momentum sum rules as well as mapping the partonic spatial structure of hadrons. In this work, we extend the utility of GPDs in mapping the proton’s spatial structure beyond the typical one-body partonic picture,...

37. Inclusive and diffractive dijet production with the ATLAS experiment

Benjamin Jacob Gilbert (Lawrence Livermore Nat. Laboratory (US))

12/06/2025, 09:20

Inclusive and diffractive processes and photon, proton and nuclear structure

In ultra-peripheral collisions (UPCs), emitted photons may participate in a hard-scattering process with partons within the struck nucleus, providing a clean, energetic probe of its parton distributions. This talk presents measurements of jet production in UPCs performed with the ATLAS detector using high-statistics 2018 Pb+Pb data. Events are selected using requirements on jet production and...

29. Coulomb Dissociation Measurement in Isobaric Collisions at $\sqrt{s_{NN}} = 200$ GeV with the STAR Experiment

Huda Nasrulloh (University of Science and Technology of China)

12/06/2025, 09:40

Inclusive and diffractive processes and photon, proton and nuclear structure

The STAR experiment collected large-statistics datasets from isobar collisions of $^{96}_{44}\text{Ru}+^{96}_{44}\text{Ru}$ and $^{96}_{40}\text{Zr}+^{96}_{40}\text{Zr}$ ions in 2018, offering a valuable opportunity to study Coulomb dissociation via Ultra-Peripheral Collisions (UPCs). Despite having identical mass numbers, these isobars exhibit distinct proton and neutron distributions,...

49. Production of $\pi$, $K$, p in inclusive UPC events in ALICE

Simone Ragoni (Creighton University (US))

12/06/2025, 10:00

Inclusive and diffractive processes and photon, proton and nuclear structure

High-multiplicity proton–proton and proton–lead collisions at LHC energies feature signatures similar to those observed in Pb--Pb collisions, such as e.g. strangeness enhancement and collective expansion effects, which are traditionally attributed to the formation of the quark–gluon plasma. One way to study them is through the measurement of $p_T$-spectra for identified hadrons such as charged...

89. Di-hadron spectroscopy in PbPb UPC events measured in LHCb

Cesar Luiz Da Silva (Los Alamos National Laboratory (US))

12/06/2025, 10:20

Inclusive and diffractive processes and photon, proton and nuclear structure

Vector, scalars and tensor mesons are accessible in the mass spectrum of di-hadrons measured in UPC events. The LHCb experiment is able to identify pions, kaons, proton, electrons, muons and photons at a very low transverse momentum, enabling the observation of a broad spectrum of mesons produced from different kinds of photon and pomeron interactions. This presentation will discuss the...

92. Measurement of inclusive D0 production in UPCs with CMS

Jordan Lang (Massachusetts Inst. of Technology (US))

12/06/2025, 11:10

Inclusive and diffractive processes and photon, proton and nuclear structure

To be included

74. Inclusive UPC charm photoproduction in ALICE

Sigurd Nese (University of Oslo (NO))

12/06/2025, 11:30

Inclusive and diffractive processes and photon, proton and nuclear structure

Inelastic photoproduction of charm has been used previously to constrain the proton gluon distribution at low-x, using e-p collisions. Ultra-peripheral heavy-ion collisions provide an opportunity to use the same mechanism to study the less known nuclear gluon distribution. In these collisions, a photon emitted from one nucleus interacts with a gluon in the target nucleus, producing a pair of...

51. Inclusive $\mathrm{D}^0$ photoproduction in ultra-peripheral collisions

Patricia Gimeno-Estivill

12/06/2025, 11:50

Inclusive and diffractive processes and photon, proton and nuclear structure

We compute the differential cross section for inclusive $\mathrm{D}^0$ production in ultra-peripheral collisions within the Color Glass Condensate framework. Our predictions are found to be in good agreement with preliminary CMS data. Furthermore, we parametrize saturation effects by a nuclear modification ratio for photoproduction $R_{pA}$ and examine the collinear factorization limit of the...

103. Predictions for Inclusive Charm Photoproduction in Ultraperipheral Collisions at the LHC Using FONLL

Anna Maria Stasto (Pennsylvania State University (US))

12/06/2025, 12:10

Inclusive and diffractive processes and photon, proton and nuclear structure

Abstract: We present theoretical predictions for the inclusive D0 production cross section in ultraperipheral Pb–Pb collisions at the LHC, as a function of transverse momentum and rapidity. The calculations are performed within the Fixed-Order Next-to-Leading Logarithm (FONLL) framework, which is validated using D^* photoproduction cross sections measured in electron–proton collisions at HERA....

75. Inclusive quarkonium photoproduction at the LHC

Kate Lynch (University College Dublin (IE) and Université Paris-Saclay (FR))

12/06/2025, 12:30

Inclusive and diffractive processes and photon, proton and nuclear structure

We demonstrate that hadron-hadron collisions at the LHC can be used to extract inclusive photoproduction cross sections. We focus on quarkonium cross sections in proton-lead collisions. We illustrate this by constructing a Monte Carlo for both the signal and background and show that, despite the background having a significantly larger cross section, the signal can be experimentally...

91. Small-x physics using ZDC at the LHC in UPCs and beyond

Mark Strikman (Pennsylvania State University (US))

Inclusive and diffractive processes and photon, proton and nuclear structure

We consider production of very forward neutrons in photon-nucleus and proton-nucleus inelastic collisions, which are detected in the LHC detectors by zero degree calorimeters (ZDC) with efficiency close to one. We argue that such measurements would provide a new probe of nuclear shadowing in soft and hard regimes of QCD. In particular, we calculate the distribution over the number of...

47. Updated Measurement of Dijet Production in Ultraperipheral PbPb Collisions with 2018 CMS Data

Cole Douglas Le Mahieu (University of Kansas)

Inclusive and diffractive processes and photon, proton and nuclear structure

Abstract: Exclusive dijet production in ultraperipheral lead-lead (PbPb) collisions has been proposed as a probe to constrain the elliptically polarized gluon distributions of heavy ions. Specifically, the second Fourier harmonic ($v_2$) of the angle ($\Delta\phi$) between the three-momentum vector sum ($\vec{Q}_T = \vec{p}_{T,1} + \vec{p}_{T,2}$) and vector difference ($\vec{q}_T =...