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

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

Fotoprodução exclusiva de quarkônios pesados em colisões ultraperiféricas

Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro de Ciências Físicas e Matemáticas, Programa de Pós-Graduação em Física, Florianópolis, 2020.Neste trabalho, discutimos a fotoprodução exclusiva de estados fundamentais e excitados dos mésons vetoriais J/?(1S, 2S) e ?(1S, 2S) em colisões ultraperiféricas (UPCs) entre íons e prótons. Para as funções de onda do fóton que se desdobra no par quark-antiquark utilizamos as já bem conhecidas e utilizadas na literatura funções de onda nas variáveis do cone de luz. Para a interação do dipolo de quarks com o íon, utilizamos as seções de choque obtidas fenomenologicamente GBW e KST, e discussões acerca do limite não perturbativo da QCD são desenvolvidas. Posteriormente, utilizamos os modelos de potenciais entre quarks, bem como efeitos de spin dos mesmos, para obter as funções de ondas dos mésons pesados através das equações de Schrödinger no regime não relativístico. Encontramos uma boa concordância entre os nossos cálculos e os dados obtidos dos colisores de LHC e HERA para J/?(1S, 2s) e ?(1S) em colisões ?p. Utilizando o fluxo de fótons provindo do método de Weizsäcker-Williams e a seção de choque de fotoprodução nuclear da teoria de Glauber-Gribov, somos capazes de estender a análise para o caso nuclear, e comparar os resultados obtidos com os aceleradores de partículas. Das produções nucleares, dois casos são possíveis de serem obtidos, o caso em que o núcleo alvo permanece intacto (produção coerente) e o caso em que o mesmo se excita ou quebra para um estado qualquer (produção incoerente). Dois efeitos de grande importância são apresentados no caso de colisões ultraperiféricas nucleares (AA UPCs), chamados de sombreamento de glúons e comprimento de coerência finita. Nossos resultados são comparados com os dados recentes do aceleradores LHCb, CMS e ALICE para o caso incoerente (J/?(1S) para 2.76 TeV) e para o caso coerente (J/?(1S, 2S) para 2.76 e 5.02 TeV). Também mostramos as predições para os estados que ainda não possuem dados, no aguardo que futuras medições tragam uma informação mais detalhada sobre as funções de onda dos mésons vetoriais e sobre os efeitos nucleares.Abstract: In this work, we discuss the exclusive photoproduction of ground and excited states of ?(1S, 2S) and ?(1S, 2S) in ultraperipheral collisions (UPCs) of ions and protons. For the photon wave functions that fluctuates to the pair quark antiquark we use the well known and used in literature wave functions in the light-cone variables. For the interaction of the quarks dipole with the target, it is used the dipole cross sections obtained phenomenologically GBW and KST, and discussions about the non-perturbative QCD limit are made. Furthermore, using the potential models 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/?(1S, 2S) and ?(1S) in ?p collisions. Using the photon flux from the Weizsäcker-Williams method and the Glauber-Gribov photoproduction cross section in the nuclear regime, we are able to obtain the total nuclear cross sections and compare them with the data from accelerators. For the nuclear processes, two cases are important to understand: the one where the nucleus stays intact (coherent production) and the one in which it breaks or is excited (incoherent production) after the collision. Two effects are also discussed in this work and are important in the calculations to the nuclear target case: the gluon shadowing and the finite coherence length. Our results are compared to the LHCb, CMS and ALICE data, in both incoherent (J/?(1S) at 2.76 TeV) and coherent (J/?(1S, 2S) at 2.76 and 5.02 TeV) processes. We also provide the corresponding predictions for the excited states of charmonia and bottomonia, in the expectation that future measurements could provide a more detailed information about the vector meson wave functions and the nuclear effects

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