arXiv subjects

R. Terra

Publications and source records attributed to R. Terra.

4 recordsLinked to original sources

arXiv2026

Effects of the initial-state geometry on D-meson production in pp and pPb collisions

Going from lower to higher multiplicity events in proton-proton and proton-lead collisions, the data show a stronger than linear growth of the D-meson normalized yields. In this contribution we try to understand this behavior using a Monte Carlo event generator which implements the $k_T$-factorization formalism. We use different spatial distribution of matter in the proton and in the lead nucleus at the initial stage of these collisions. We find that, with all the tested spatial distributions, the model reproduces well the behavior seen in the data. We conclude that this observable is not appropriate for a detailed study of the spatial distribution of matter in the proton.

hep-ph↗

arXiv2025

Initial-state geometry and multiplicity distributions in pp and pPb collisions

This work investigates the possibility of accessing the initial geometric shape of the proton in proton-proton and proton-nucleus collisions at the LHC. In particular, we look for manifestations of the configuration in which the proton is made of three quarks linked by a Y-shape gluon string, called baryon junction. This initial state spatial configuration has been used in the past to describe data on baryon rapidity distributions, diffractive $J/\psi$ production and multiplicity distributions in pp collisions. In spite of its success in explaining the data, the evidence of the baryon junction still needs confirmation. Further studies will be undertaken at the electron-ion collider. In this work we study multiplicity distributions measured in pp and pPb collisions. Different initial state geometries are used as input in a Monte Carlo event generator which implements the $k_T$-factorization formalism of the CGC with KLN unintegrated gluon distributions. The results show that the data on multiplicity distributions are good enough to discriminate between different initial state geometries. Moreover, they indicate that it is crucial to take into account the intrinsic fluctuations of the saturation scale.

hep-ph↗

arXiv2024

Baryon junction effects on charmonium production in pp and pPb collisions

In this work we study the effects of the proton and $Pb$ internal structure on charmonium production at high multiplicities. To do this, we assume that the nucleon has an Y shape, which means that the effective quarks (quarks + antiquarks + gluons) are in the extremities of the Y, connected by gluon lines. Since the quarks are in the periphery and the gluons are in the center, as $pp$ collisions go from peripheral to more central and then to ultra-central collisions, the interactions change from quark-quark to gluon-gluon. The enhanced growth of $J/ψ$ occurs because $σ( g + g \to c + \bar{c}) \gg σ( q + \bar{q} \to c + \bar{c})$. In the $p-Pb$ collisions the enhancement is caused by the high concentration of partons in the center of the nuclei. These effects can explain the growth seen in the data and give support to the Y picture of the proton.

hep-ph↗

arXiv2023

Charmonium production in high multiplicity p p collisions and the structure of the proton

In this work we study charmonium production in high multiplicity proton-proton collisions. We investigate the role of the spatial distribution of partons in the protons and assume that the proton has a Y shape. In this configuration quarks are more at the surface and gluons in the inner part of the proton. Going from peripheral to more central and then to ultra-central proton-proton collisions, we go from quark-quark collisions to gluon-gluon collisions. Since gluons are much more abundant, the cross sections grow. In the case of charm production this growth is enhanced by the fact that, $σ( g + g \to c + \bar{c}) >> σ( q + \bar{q} \to c + \bar{c})$. These effects can explain the growth seen in the data.

hep-ph↗