Exclusive photoproduction of excited quarkonia in ultraperipheral collisions

In this paper, we discuss the exclusive photoproduction of ground and excited states of $\psi(1S,2S)$ and $\Upsilon(1S,2S)$ 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 $J/\psi (1S,2S)$ and $\Upsilon(1S)$ in $\gamma p$ 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 ($J/\Psi(1S)$ at 2.76 TeV) and coherent ($J/\Psi(1S)$ 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.Comment: 21 pages, 7 figs, revised versio

Exclusive photo- and electroproduction of excited light vector mesons via holographic model

In this paper, we study total and differential observables of electro- and photoproduction of light $\rho$, $\omega$ and $\phi$ mesons as functions of the center-of-mass energy of the $\gamma p$ collision and momentum transfer squared $|t|$. The corresponding vector mesons wave functions have been computed in the framework of relativistic AdS/QCD holographic approach. A satisfactory description of all available data on ground-state $\rho(1S)$, $\omega(1S)$ and $\phi(1S)$ mesons production cross sections has been achieved in the color dipole picture. Finally, the key observables of excited $\rho(2S)$, $\omega(2S)$ and $\phi(2S)$ states production in $\gamma^{(*)} p$ collisions have been presented here using a common wave function formalism. This study reveals a large theoretical uncertainty coming from the modeling of the partial dipole amplitude in the nonperturbative kinematical domain. Hence, the latter could benefit from future measurements of photoproduction of the excited states

Exame de Qualificação de Doutorado de Cheryl Henkels de Souza – 11 de dezembro de 2020 – sexta-feira – 14 horas

Defesa de exame de qualificação de doutorado de Cheryl Henkels de Souza, realizada na data de 11 de dezembro de 2020, às 14 horas, no(a) ConferênciaWeb da Rede Nacional de PesquisaDefesa de exame de qualificação de doutorado de Cheryl Henkels de Souza, realizada na data de 11 de dezembro de 2020, às 14 horas, no(a) ConferênciaWeb da Rede Nacional de Pesquis

Exclusive photo and electroproduction of vector mesons in proton and nuclear targets within the color dipole model

Tese (doutorado) - Universidade Federal de Santa Catarina, Centro de Ciências Físicas e Matemáticas, Programa de Pós-Graduação em Física, Florianópolis, 2023.Nesse trabalho, fotoprodução e eletroprodução exclusivas dos estados fundamental e excitado dos mésons vetoriais ?, ?, ?, ? e ? são discutidas em colisões hadrônicas ultraperiféricas (UPCs) com prótons e núcleos como alvo. Como estamos interessados em espalhamentos nos quais o projétil é um fóton virtual ou quase real produzido pelo lépton ou hádron incidente, nós empregamos o modelo de dipolo de cor, o qual permite a fatorização do processo em três etapas. A primeira consiste no desdobramento do fóton no par q¯q, o qual é descrito por uma função de onda calculada perturbativamente. A segunda corresponde à interação desse par com o alvo, que é descrita por uma seção de choque de dipolo parametrizada para considerar os fenômenos não perturbativos. Nesse trabalho, usamos cinco parametrizações diferentes: duas integradas (GBW e KST) e três não integradas (bCGC, bSat e BK), estas dependentes do parâmetro de impacto. O terceiro passo é a transição do par q¯q num méson vetorial. As contribuições dessa parte para o cálculo de seções de choque totais e diferenciais em t é um dos principais objetos de estudo desse trabalho, por isso, para descrever mésons vetoriais leves e pesados, usamos dois modelos para a função de onda do méson vetorial: o modelo AdS/QCD holográfico e o modelo de potenciais (que incorpora a transformação de spin de Melosh). Com esse formalismo e com o próton como alvo, nós comparamos os nossos resultados com os dados disponíveis dos colisores HERA e LHC e obtivemos uma boa concordância tanto nos resultados diferenciais quanto nos resultados integrados. Para o caso nuclear, nós estendemos nossos cálculos a partir do uso da teoria de Glauber-Gribov e os aplicamos para a fotoprodução coerente e incoerente de mésons vetoriais em colisões ultraperiféricas com a inclusão dos efeitos de comprimento de coerência finito e sombreamento de glúons ajustado a dados. Nossos resultados independentes de t foram comparados com os dados disponibilizados pelo LHC, tanto para processos incoerentes (J/? a 2.76 TeV) quanto para processos coerentes (J/? e ?' a 2.76 e 5.02 TeV). Enquanto que no primeiro caso não conseguimos descrever o único dado disponível no momento, no segundo caso, nós obtivemos uma boa descrição dos dados coerentes, especialmente para J/?, o que mostra a eficácia do formalismo utilizado. Já no caso dependente de t, a divulgação recente de dados de fotoprodução coerente de J/? a 5.02 TeV foi uma ferramenta conveniente para medir a eficácia dos nossos resultados, os quais se mostraram muito próximos dos dados experimentais. Nós também apresentamos predições para seções de choque para produção de ?(1S) e ?(2S) em energias do LHC (s = 5.02 TeV), que podem ser úteis no futuro com novas medições nos grandes colisores de partículas.Abstract: In this work, exclusive photo and electroproduction of ground and excited states of the vector mesons ?, ?, ?, ?, and ? are discussed in ultraperipheral hadron collisions (UPCs) with proton and nucleus targets. Since we are interested in scatterings with the projectile being a virtual or quasi-real photon produced by the incoming lepton or hadron, we employ the color dipole model, which permits the factorization of the process into three steps. The first one is the splitting of the photon in a q¯q pair, which is described by a perturbatively calculated wave function. The second is the interaction of this pair with the target, which is described by a parametrized dipole cross section in order to account for the non-perturbative effects. In this work, we use five different parametrizations, two integrated (GBW and KST) and three unintegrated (bCGC, bSat, and BK), which are b-dependent. The third step is the transition of the q¯q pair into the vector meson. This part?s contributions to the evaluation of total and t-differential cross sections is one of the main objects of study of this work, thus to describe light and heavy vector mesons, we used two models for the vector meson wave function: the AdS/QCD holographic model and the potential model (which incorporates the Melosh spin transformation). With this formalism and the proton as a target, we compared our results with the available data from the HERA and the LHC colliders, and we obtained a good agreement for both the differential and integrated results. For the nuclear case, we extended our calculations by using the Glauber- Gribov theory and applied it to the coherent and incoherent photoproduction of vector mesons in UPCs with the inclusion of the finite coherence length and gluon shadowing effects fitted to data. Our t-independent results are compared to the available LHC data in both incoherent (J/? at 2.76 TeV) and coherent (J/? and ?' at 2.76 and 5.02 TeV) processes. While in the first case, we could not describe the data, in the second case, we obtained a good description of the coherent data, especially for J/?, which shows the efficiency of the formalism used. In the t-dependent case, the recent publication of coherent J/? photoproduction data at 5.02 TeV was a convenient tool to measure the efficiency of our results, which were very close to the experimental data. We also presented predictions for ?(1S) and ?(2S) cross sections at LHC energies (s = 5.02 TeV), which can be helpful in the future with new measurements on the large particle colliders

Coherent photoproduction of light vector mesons off nuclear targets in the dipole picture

We study the coherent photoproduction of light vector mesons in Pb-Pb collisions in the framework of color dipole approach. We employ the Glauber–Gribov formalism supplemented by an effective suppression factor RG accounting for the gluon shadowing correction. We adjust the latter to reproduce the deep inelastic structure function F2 (E665) and ρ meson photoproduction (ALICE) data. We achieve a good description of the available data points with RG=0.85 at scale Mρ2/4=0.15 GeV2. In addition, employing this suppression factor, we present predictions for coherent ρ(2S), ω(1S,2S) and ϕ(1S,2S) photoproduction observables using the holographic vector meson wave functions

Momentum transfer squared dependence of exclusive quarkonia photoproduction in ultraperipheral collisions

We study fully differential quarkonia photoproduction observables in ultraperipheral collisions 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 quasireal photon flux emitted by an incoming hadron. We analyze such observables for ground J/ψ, (1S) and excited ψ′, (2S) states whose light-front wave functions are obtained in the framework of an interquark potential model incorporating the Melosh spin transformation. Two different low-x saturation models, one obtained by solving the Balitsky-Kovchegov equation with the collinearly improved kernel and the other with a Gaussian impact-parameter-dependent profile, are used to estimate the underlined theoretical uncertainties of our calculations. The results for the proton target and with charmonium in the final state are in agreement with the available HERA data, while in the case of the nucleus target we make predictions for γA and AA differential cross sections at different W and at s=5.02 TeV, respectively