arXiv subjects

E. R. Cazaroto

Publications and source records attributed to E. R. Cazaroto.

12 recordsLinked to original sources

arXiv2018

Heavy quark production in $pA$ collisions: the double parton scattering contribution

In this paper we estimate the double parton scattering (DPS) contribution for the heavy quark production in $pA$ collisions at the LHC. The cross sections for the charm and bottom production are estimated using the dipole approach and taking into account the saturation effects, which are important for high energies and for the scattering with a large nucleus. We compare the DPS contribution with the single parton scattering one and demonstrate that in the case of charm production both are similar in the kinematical range probed by the LHC. Predictions for the rapidity range analysed by the LHCb Collaboration are also presented. Our results indicate that the study of the DPS contribution for the heavy quark production in $pPb$ collisions at the LHC is feasible and can be useful to probe the main assumptions of the approach.

hep-ph↗

arXiv2015

Tetraquark Production in Double Parton Scattering

We develop a model to study tetraquark production in hadronic collisions. We focus on double parton scattering and formulate a version of the color evaporation model for the production of the $X(3872)$ and of the $T_{4c}$ tetraquark, a state composed by the $c \bar{c} c \bar{c}$ quarks. We find that the production cross section grows rapidly with the collision energy $\sqrt{s}$ and make predictions for the forthcoming higher energy data of the LHC.

hep-ph↗

arXiv2013

Charm production in double parton scattering at the LHC

We calculate $c\bar{c}c\bar{c}$ and $b\bar{b}b\bar{b}$ production cross section in Double Parton Scattering (DPS) processes at the energies of LHC. In our calculation we include saturation effects in the gluon distribution. For charm production, our results confirm the prediction of a previous work in which saturation effects were neglected, namely that at the energies of LHC charm production in DPS processes becomes comparable with charm production in SPS. We also estimate the production of $c\bar{c}b\bar{b}$ in DPS. Our results indicate that at $\sqrt{s}=14$ TeV half of the total amount of bottom produced in proton-proton collisions comes from this process.

hep-ph↗

arXiv2013

A quantum mechanical interpretation for the relativity of the space-time

In special relativity theory the physical quantities are generally expressed as function of the velocity. In the particular case of an extended object, the factor 1/gamma of Lorentz contraction of its length in the direction of motion is written as a function of the velocity of the extended object. The same happens with the Lorentz factor gamma of time interval dilation of a moving clock. In this paper we show that when gamma is written as a function of the relativistic energy of the considered object the resulting expressions for the length and for the time interval suggest that the contraction of length as well as the dilation of the time interval are manifestations of the wave behavior of matter.

physics.gen-ph↗

arXiv2013

On the energy dependence of the D^+/D^- production asymmetry

In this paper we discuss the origin of the asymmetry present in D meson production and its energy dependence. In particular, we have applied the meson cloud model to calculate the asymmetries in D^-/D^+ meson production in high energy p-p collisions and find a good agreement with recent LHCb data. Although small, this non-vanishing asymmetry may shed light on the role played by the charm meson cloud of the proton.

hep-ph↗

arXiv2013

What kind of energy is the mass?

In 1905, Einstein discovered the famous equation: E=mc^2, which means that the rest mass of a particle is some kind of energy. This energy is generally referred to as "rest energy", since the particle is believed to be at rest. This paper proposes a new interpretation to the term mc^2. Observing the similarity between the term mc^2 and the kinetic energy term mv^2/2, we propose to interpret mc^2 as being one term of kinetic energy. In other words we propose that, in the called "rest frame", the massive particles are not really at rest, but they are doing a special kind of motion at the light speed c. In this interpretation the "mass" is not an intrinsic property of the particle. The "mass" is simply the kinetic energy associated with this special kind of motion. The more important consequence of this hypothesis is that the term mc^2, present in the relativistic Hamiltonian, must be rewritten as: mc^2 => p_0 c, where p_0 = mc is the modulus of the instantaneous linear moment \vec{p}_0 associated with the special motion. We analyse a physical scenario in which this special motion is a Microscopic Orbital Circular Motion (MOCM). The characteristic length scale of the MOCM is of the order of the Compton wavelength of the particle.

physics.gen-ph↗

arXiv2013

Heavy quark production and gluon saturation in double parton scattering at LHC

The production of $c\bar{c}c\bar{c}$, $b\bar{b}b\bar{b}$ and $c\bar{c}b\bar{b}$ pairs considering double parton scattering at LHC energies is investigated. We estimate the contribution of saturation effects to the different final states and predict the energy dependence of the cross sections. Moreover, we estimate the ratio between the double and single parton scattering cross sections for the full rapidity range of the LHC and for the rapidity range of the LHCb experiment. For the full rapidity range we confirm a previous prediction, namely that for charm production the double parton scattering contribution becomes comparable with the single parton scattering one at LHC energies. We also demonstrate that this result remains valid when one introduces saturation effects in the calculations. Finally we show that the production of $c\bar{c}b\bar{b}$ contributes significantly to bottom production. For the LHCb kinematical range the ratio is strongly reduced.

hep-ph↗

arXiv2011

Non-linear QCD dynamics in two-photon interactions at high energies

Perturbative QCD predicts that the growth of the gluon density at high energies should saturate, forming a Color Glass Condensate (CGC), which is described in mean field approximation by the Balitsky-Kovchegov (BK) equation. In this paper we study the $γγ$ interactions at high energies and estimate the main observables which will be probed at future linear colliders using the color dipole picture. We discuss in detail the dipole - dipole cross section and propose a new relation between this quantity and the dipole scattering amplitude. The total $γγ$, $γ^{*} γ^{*}$ cross-sections and the real photon structure function $F_2^γ(x,Q^2)$ are calculated using the recent solution of the BK equation with running coupling constant and the predictions are compared with those obtained using phenomenological models for the dipole-dipole cross section and scattering amplitude. We demonstrate that these models are able to describe the LEP data at high energies, but predict a very different behavior for the observables at higher energies. Therefore we conclude that the study of $γγ$ interactions can be useful to constrain the QCD dynamics.

hep-ph↗

arXiv2011

Heavy quark production at LHC in the color dipole formalism

In this work we estimate the heavy quark production in proton-proton and proton-nucleus collisions at LHC energies using the color dipole formalism and the solution of the running coupling Balitsky-Kovchegov equation. Nuclear effects are considered in the computation of the total cross sections and rapidity distributions for scattering on protons and nuclei.

hep-ph↗

arXiv2010

Exclusive processes in electron - ion collisions

The exclusive processes in electron-ion ($eA$) interactions are an important tool to investigate the QCD dynamics at high energies as they are in general driven by the gluon content of the target, which is strongly subject to parton saturation effects. In this paper we compute the cross sections for the exclusive vector meson production as well as the deeply virtual Compton scattering (DVCS) relying on the color dipole approach and considering the numerical solution of the Balitsky-Kovchegov equation including running coupling corrections (rcBK). The production cross sections obtained with the rcBK solution and bCGC parametrization are very similar, the former being slightly larger.

hep-ph↗

arXiv2008

Could saturation effects be visible in a future electron-ion collider?

We expect to observe parton saturation in a future electron - ion collider. In this letter we discuss this expectation in more detail considering two different models which are in good agreement with the existing experimental data on nuclear structure functions. In particular, we study the predictions of saturation effects in electron - ion collisions at high energies, using a generalization for nuclear targets of the b-CGC model, which describes the $ep$ HERA quite well. We estimate the total, longitudinal and charm structure functions in the dipole picture and compare them with the predictions obtained using collinear factorization and modern sets of nuclear parton distributions. Our results show that inclusive observables are not very useful in the search for saturation effects. In the small $x$ region they are very difficult to disentangle from the predictions of the collinear approaches . This happens mainly because of the large uncertainties in the latter. On the other hand, our results indicate that the contribution of diffractive processes to the total cross section is about 20 % at large A and small Q^2, allowing for a detailed study of diffractive observables. The study of diffractive processes becomes essential to observe parton saturation.

hep-ph↗

arXiv2008

Constraining the nuclear gluon distribution in $eA$ processes at RHIC

A systematic determination of the gluon distribution is of fundamental interest in understanding the parton structure of nuclei and the QCD dynamics. Currently, the behavior of this distribution at small $x$ (high energy) is completely undefined. In this paper we analyze the possibility of constraining the nuclear effects present in $xg^A$ using the inclusive observables which would be measured in the future electron-nucleus collider at RHIC. We demonstrate that the study of nuclear longitudinal and charm structure functions allows to estimate the magnitude of shadowing and antishadowing effects in the nuclear gluon distribution.

hep-ph↗