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...
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...
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 =...
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,...
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...
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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...
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...
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....
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...
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...
