In this paper, we discuss the exclusive photoproduction of ground and excited states of $ψ(1S,2S)$ and $Υ(1S,2S)$ in ultraperipheral collisions (UPCs). Using the potential model in order to obtain the vector meson wave function, we find a good agreement of our calculations with data from the LHC and HERA colliders for $J/ψ(1S,2S) $ and $Υ(1S)$ in $γp$ collisions. We extend the calculations to the nuclear target case applying them to $AA$ UPCs with the use of the shadowing and finite coherence length effects fitted to the data. Our results are compared to the recent LHC data, in both incoherent ($J/Ψ(1S)$ at 2.76 TeV) and coherent ($J/Ψ(1S)$ at 2.76 and 5.02 TeV) processes. We also show the corresponding predictions for the excited states, in the hope that future measurements could provide more detailed information about the vector meson wave functions and nuclear effects.
Photoproduction of $ρ^0$ mesons in ultraperipheral heavy ion collisions at energies available at the BNL Relativistic Heavy Ion Collider (RHIC) and CERN Large Hadron Collider (LHC)
We present predictions for the rapidity-differential cross sections of exclusive $Υ$ photoproduction in ultraperipheral collisions (UPCs) of lead ions at the Large Hadron Collider (LHC). We work in the framework of collinear factorization at next-to-leading order (NLO) in perturbative QCD, modeling the generalized parton distributions (GPDs) through the Shuvaev transform of nuclear parton distribution functions (nPDFs). While the effects due to the GPD modeling turn out to be small, the direct NLO predictions still carry significant nPDF-originating uncertainties and depend strongly on the cho…
We compute the cross section of inclusive dijet photoproduction in ultraperipheral Pb-Pb collisions at the LHC using next-to-leading order perturbative QCD. We demonstrate that our theoretical calculations provide a good description of various kinematic distributions measured by the ATLAS collaboration. We find that the calculated dijet photoproduction cross section is sensitive to nuclear modifications of parton distribution functions (PDFs) at the level of 10 to 20%. Hence, this process can be used to reduce uncertainties in the determination of these nuclear PDFs, whose current magnitude is…
We argue that the STAR data on $J/ψ$ photoproduction in $d+Au$ ultraperipheral collisions (UPCs) at the momentum transfer $t \neq 0$ primarily probes elastic and possibly nucleon-dissociative $J/ψ$ photoproduction on quasi-free nucleons, while being essentially insensitive to expectedly weak nuclear modifications of the gluon distribution in the deuteron. Analyzing the STAR detector capabilities for selection of UPC events, we explore the possibility that the contribution of nucleon-dissociative $J/ψ$ photoproduction is negligibly small and obtain a very good description of the $t$ dependence …
We present the first study of rapidity-differential cross sections of coherent exclusive $J/ψ$ photoproduction in heavy-ion ultraperipheral collisions (UPCs) at the LHC, $\text{d}σ(\text{Pb}+\text{Pb}\rightarrow \text{Pb}+J/ψ+\text{Pb})/\text{d}y$, to NLO in collinear factorisation. Taking the generalised parton distributions as their forward limit counterparts, the NLO contributions in the cross sections are quantified and we show that the real part of the amplitude and quark-PDF contributions must not be neglected. We further evaluate the uncertainties arising from the scale-choice at both L…
We present the first next-to-leading-order (NLO) perturbative QCD (pQCD) study of rapidity-differential cross sections of coherent exclusive photoproduction of $J/ψ$ mesons in heavy-ion ultraperipheral collisions (UPCs) at the LHC, $dσ/dy(\text{Pb} + \text{Pb} \rightarrow \text{Pb} + J/ψ+ \text{Pb})$. For this, we account for the photon-nucleon NLO cross sections at the forward limit, the $t$ dependence using a standard nuclear form factor, and the photon fluxes of the colliding nuclei. Approximating the generalized parton distributions with their forward-limit parton distribution functions (P…
In this paper we analyze the associated $ϕ$ and $J/Ψ$ photoproduction in ultraperipheral $PbPb$ collisions through the double scattering mechanism for the energies of the Large Hadron Collider (LHC) and Future Circular Collider (FCC). Our results complement a previous analysis for the $ρρ$, $J/ΨJ/Ψ$ and $ρJ/Ψ$ production. We present our predictions for the total cross sections and rapidity distributions considering the rapidity ranges covered by the ALICE and LHCb detectors, which indicate that a future experimental analysis of $ϕJ/Ψ$ final state is feasible. These results point out that the s…
We calculate the cross section of inclusive dijet photoproduction in ultraperipheral collisions (UPCs) of heavy ions at the CERN Large Hadron Collider using next-to-leading order perturbative QCD and demonstrate that it provides a good description of the ATLAS data. We study the role of this data in constraining nuclear parton distribution functions (nPDFs) using the Bayesian reweighting technique and find that it can reduce current uncertainties of nPDFs at small $x$ by a factor of 2. We also make predictions for diffractive dijet photoproduction in UPCs and examine its potential to shed ligh…
Using the Gribov-Glauber model for photon-nucleus scattering and a generalization of the vector meson dominance model for the hadronic structure of the photon, we make predictions for the cross section of incoherent $ρ$ photoproduction in Pb-Pb ultraperipheral collisions (UPCs) in the Large Hadron Collider kinematics. We find that the effect of the inelastic nuclear shadowing is significant and leads to an additional 25% suppression of the incoherent cross section. Comparing our predictions to those of the STARlight Monte Carlo framework, we observe very significant differences.
Evaluating the ratio of the exclusive vector meson photoproduction to inclusive hadron/jet production cross section in ultraperipheral heavy ion collisions
Universidade Federal de Santa Catarina（圣卡塔琳娜联邦大学）；Federal University of Rio Grande do Sul (UFRGS)（南里奥格兰德联邦大学）
Coherent photoproduction of heavy quarkonia on nuclear targets is studied within the QCD color dipole formalism including several main phenomena: i) The correlation between impact parameter of a collision $\vec b$ and dipole orientation $\vec r$; ii) The higher-twist nuclear shadowing related to the $\bar QQ$ Fock state of the photon; iii) The leading-twist gluon shadowing corresponding to higher Fock components of the photon containing gluons; iv) Reduced effects of quantum coherence in a popular Balitsky-Kovchegov equation compared to calculations, which are frequently presented in the liter…
Nuclear effects in photoproduction of heavy quarks and vector mesons in ultraperipheral PbPb and pPb collisions at the LHC
通过比较$c\bar{c}$和b-b（bar）在PbPb和pPb碰撞中的光生截面，可以得到对核遮蔽效应的敏感性.光生矢量介子对底层胶子的分布更为敏感。本文研究了在sqrt（s_NN）=5 TeV和sqrt（s_NN）=2.76 $ TeV, respectively. The potentials of using these processes for constraining nuclear gluon shadowing are explored. It is found that photoproduction of $ J/J条件下，在大型强子对撞机上进行的超周边pPb和PbPb碰撞中，重夸克光生和矢量介子光生的截面及其与快度的关系。特别是PbPb碰撞中的$ and $对胶子遮蔽表现出很好的敏感性。
The elastic differential and integrated total cross section for the exclusive $ρ^0$ photoproduction in electron-proton ($ep$) collisions are evaluated taking into account nonperturbative Pomeron exchange approach. By using three different models based on Regge phenomenology the results are compared to recent measurements by H1 Collaboration in $ep$ collisions and by the CMS collaboration from ultraperipheral proton-lead collisions. The analysis is expanded by calculating the coherent nuclear cross section, $σ(γA\rightarrow ρ^0 A)$, which is applied to $ρ^0$ production in ultraperipheral lead-l…
We present a detailed study of vector meson photoproduction in ultraperipheral heavy ion collisions (UPCs). Using the dipole model, we develop a framework for the joint impact parameter and transverse momentum dependent cross sections. We compute the unpolarized cross section and $\cos 2ϕ$ azimuthal angular correlation for $ρ^0$ photoproduction with $ϕ$ defined as the angle between the $ρ^0$'s transverse momentum and its decay product pion meson's transverse momentum. Our result on unpolarized coherent differential cross section gives excellent description to the STAR experimental data. A firs…
Ultraperipheral collisions (UPCs) of protons and nuclei are important for the study of the photoproduction of vector mesons and exotic states. The photoproduction of vector mesons in the pentaquark resonance channel in $p\mbox{-}Au$ UPCs at the Relative Heavy Ion Collider (RHIC) and $p$-$Pb$ UPCs at the Large Hadron Collider (LHC) is investigated by employing STARlight package. The cross sections of vector mesons via pentaquark state resonances channel are obtained using effective Lagrangian method. The pseudo-rapidity and rapidity distributions of $J/ψ$ and $Υ(1S) $ are given for $p\mbox{-}Au…
In this paper, we study fully differential quarkonia photoproduction observables in ultraperipheral collisions (UPCs) as functions of momentum transfer squared. We employ the dipole picture of the QCD part of the scattering with proton and nucleus targets, with the projectile being a quasi-real photon flux emitted by an incoming hadron. We analyse such observables for ground $J/ψ$, $Υ(1S)$ and excited $ψ'$, $Υ(2S)$ states whose light-front wave functions are obtained in the framework of interquark potential model incorporating the Melosh spin transformation. Two different low-$x$ saturation mo…
Using the general notion of cross section fluctuations in hadron--nucleus scattering at high energies, we derive an expression for the cross section of incoherent $J/ψ$ photoproduction on heavy nuclei $dσ_{γA \to J/ψY}/dt$, which includes both elastic $dσ_{γp \to J/ψp}/dt$ and proton-dissociation $dσ_{γp \to J/ψY}/dt$ photoproduction on target nucleons. We find that with good accuracy, $dσ_{γA \to J/ψY}/dt$ can be expressed as a product of the sum of the $dσ_{γp \to J/ψp}/dt$ and $dσ_{γp \to J/ψY}/dt$ cross sections, which have been measured at HERA, and the common nuclear shadowing factor, wh…
Accessing transverse nucleon and gluon distributions in heavy nuclei using coherent vector meson photoproduction at high energies in ion ultraperipheral collisions
In this work we present for the first time the comprehensive study of the Melosh spin rotation effects in diffractive electroproduction of S-wave heavy quarkonia off a nucleon target. Such a study has been performed within the color dipole approach using, as an example and a reference point, two popular parametrizations of the dipole cross section and two potentials describing the interaction between Q and bar{Q} and entering in the Schroedinger equation based formalism for determination of the quarkonia wave functions. We find a strong onset of spin rotation effects in 1S charmonium photoprod…
In this paper we study the high energy exclusive photoproduction of heavy quarkonia pairs in the leading order of the strong coupling constant $α_{s}$. In the suggested mechanism the quarkonia pairs are produced with opposite charge parities, and have predominantly oppositely directed transverse momenta. Using the Color Glass Condensate approach, we estimated numerically the production cross-sections in the kinematics of the forthcoming electron-proton colliders, as well as proton-ion colliders in ultraperipheral collisions. We found that the cross-sections are within the reach of planned expe…
In this letter we complement previous studies on exclusive vector meson photoproduction in hadronic collisions presenting a comprehensive analysis of the $t$ - spectrum measured in exclusive $ρ$ and $J/Ψ$ photoproduction in $pA$ collisions at the LHC. We compute the differential cross sections considering two phenomenological models for the gluon saturation effects and present predictions for $pPb$ and $pCa$ collisions. Moreover, we compare our predictions with the recent preliminary CMS data for the exclusive $ρ$ photoproduction. We demonstrate that the gluon saturation models are able to des…
In this paper we analyze the exclusive photoproduction of heavy quarkonia pairs in the collinear factorization framework. We evaluate the amplitude of the process for $J/ψ\,-η_{c}$ quarkonia pair in the leading order of the strong coupling $α_{s},$ and express it in terms of generalized parton distributions (GPDs) of gluons in the proton. We made numerical estimates in the kinematics of the Electron Ion Collider, and found that in the photoproduction regime, when the virtuality of the photon is much smaller than the quarkonia mass, the cross-section of the process is sufficiently large for exp…
We investigate the exclusive photoproduction of $J/ψ$-mesons in ultraperipheral heavy ion collisions in the color dipole approach. We first test a number of dipole cross sections fitted to inclusive $F_2$-data against the total cross section of exclusive $J/ψ$-production on the free nucleon. We then use the color-dipole formulation of Glauber-Gribov theory to calculate the diffractive amplitude on the nuclear target. The real part of the free nucleon amplitude is taken into account consistent with the rules of Glauber theory. We compare our results to recent published and preliminary data on e…
