Probing double parton scattering via associated open charm and bottom production in ultraperipheral pApA collisions

In this article, we propose a novel channel for phenomenological studies of the double-parton scattering (DPS) based upon associated production of charm $c\bar{c}$ and bottom $b\bar{b}$ quark pairs in well-separated rapidity intervals in ultra-peripheral high-energy proton-nucleus collisions. This process provides a direct access to the double-gluon distribution in the proton at small-$x$ and enables one to test the factorised DPS pocket formula. We have made the corresponding theoretical predictions for the DPS contribution to this process at typical LHC energies and beyond and we compute the energy-independent (but photon momentum fraction dependent) effective cross section.Comment: 15 pages, 7 figs., 1 table. One fig. added. Version accepted for publication at EPJ

Defesa de tese de Edgar Yubert Huayra Paitan

Defesa de tese de doutorado de Edgar Yubert Huayra Paitan, realizada no dia 10 de março de 2022, às 14 horas, na sala virtual da Conferência Web da Rede Nacional de Ensino e Pesquisa (RNP).Defesa de tese de doutorado de Edgar Yubert Huayra Paitan, realizada no dia 10 de março de 2022, às 14 horas, na sala virtual da Conferência Web da Rede Nacional de Ensino e Pesquisa (RNP)

O processo de duplo espalhamento de pártons em colisões ultraperiféricas

Tese (doutorado) - Universidade Federal de Santa Catarina, Centro de Ciências Físicas e Matemáticas, Programa de Pós-Graduação em Física, Florianópolis, 2022.Em colisões hadrônicas, a seção de choque pode ser estimada assumindo que a interação dominante se dá entre um párton do projétil com um párton do alvo. Este processo pode melhorar a nossa compreensão sobre e a construção da função de distribuição partônica do próton. No Grande Colisor de Hádrons, a ocorrência de processos de dupla interação partônica, dois pártons do projétil com dois pártons do alvo, torna-se significativa e deve ser considerada devido à elevada luminosidade partônica no estado inicial da colisão. A seção de choque da dupla interação partônica em uma colisão pp é dependente da seção de choque efetiva $\sigma^{pp}_{\rm eff}$, que tem informação da distribuição do momento transversal dos pártons dentro dos prótons que colidem. A descrição ingenua de $\sigma^{pp}_{\rm eff}$ difere fortemente dos dados experimentais obtidos no Grande Colisor de Hádrons, principalmente quando há interações de glúons no estado inicial. Assim, esta discrepância sugere a existência de correlações nos pártons que participam da colisão. Como complemento a colisões duras pp, nos propomos a estudar a seção de choque para a produção mista de quarks pesados e diléptons em uma colisão ultraperiférica de pp, Ap e AA. Nessa colisão no estado inicial, temos a interação de dois fótons vindos do núcleo projétil com dois glúons ou fóton-glúon vindos do próton ou núcleo alvo. A seção de choque é calculada através da convolução do fluxo de fótons reais, descrito pelo método de Weizsäcker-Williams, e a probabilidade da emissão do glúon do próton ou núcleo, descrita pela função de distribuição partônica. Distribuições calculadas em diferentes variáveis cinemáticas serão capazes de nos proporcionar informações relevantes sobre o processo de dupla interação partônica.Abstract: In hadron collisions, the cross section can be estimated assuming that the dominant interaction occurs between one parton of the projectile and one parton of the target, a process named single parton scattering. This process can improve our understanding about and the construction of the parton distribution function of the proton. At the Large Hadron Collider, the occurrence of double parton interaction process, which happens between two partons of the projectile with two partons of the target, becomes significant and should be considered due to the high parton luminosity in the initial state of the collision. The double parton interaction process cross section in pp collision is dependent on an effective cross section $\sigma^{pp}_{\rm eff}$, which has information about the transverse momentum distribution of partons inside the colliding protons. The naive description of $\sigma^{pp}_{\rm eff}$ differs strongly from the experimental data obtained at the Large Hadron Collider, mostly when there are gluon interactions in the initial state. Thus, this discrepancy suggests the existence of correlations in the partons that participate in the collision. As a complement to hard pp collisions, we propose to study the cross section for the mixed production of heavy quarks and dileptons in ultraperipheral collisions of pp, Ap and AA. In this collisions in the initial state, we have the interaction of two photons coming from the nucleus projectile with two gluons or photon-gluon coming from the target proton or nucleus. The cross section is calculated through the convolution of the real photon flux, that is described by the Weizsäcker-Williams method, and the probability of a gluon emission from the proton or nucleus, described by the parton distribution function. Distributions calculated on different kinematic variables will be able to provide us relevant information about the double parton interaction process

DPS mechanism for associated cc¯ bb¯ production in AA UPCs

We discuss the associated cc¯ and bb¯ quark pairs production in the double-parton scattering (DPS) process in ultraperipheral (UPCs) AA collisions. We derive an analogue of the inclusive DPS pocket formula and the photon-energy dependent effective cross section considering an overlap between the hard SPS scatterings. We provide numerical predictions for the DPS cross sections for the cc¯ bb¯ production process at the typical energies of AA UPCs at the LHC and FCC colliders and also characterize the A dependence of the total UPC DPS cross section

Valence and sea parton correlations in double parton scattering from data

The effective cross section of double parton scattering in proton collisions has been measured by many experiments with rather different results. Motivated by this fact, we assumed that the parton correlations in the transverse plane are different whether we have valence or sea partons. With this simple approach, we were able to fit the available data and found that sea parton pairs are more correlated in the transverse plane than valence--sea parton pairs.Comment: 7 pages, 1 figur

Valence and sea parton correlations in double parton scattering from data

Abstract The effective cross section of double parton scattering in proton collisions has been measured by many experiments with rather different results. Motivated by this fact, we assumed that the parton correlations in the transverse plane are different whether we have valence or sea partons. With this simple approach, we were able to fit the available data and found that sea parton pairs are more correlated in the transverse plane than valence-sea parton pairs

Double-parton scattering mechanism for associated c c ¯ l+l- production in AA ultraperipheral collisions as a probe for the photon density inside the nucleus

We discuss the associated cc¯ and l+l- pairs production in ultraperipheral heavy-ion collisions at high energies. Such a channel provides a novel probe for double-parton scattering (DPS) at small x enabling one to probe the photon density inside the nucleus. We have derived an analog of the standard central pp pocket formula and studied the kinematical dependence of the effective cross section. Taking into account both elastic and nonelastic contributions, we have shown predictions for the DPS cc¯l+l- production cross section differential in charm quark rapidity and dilepton invariant mass and rapidity for LHC and a future collider