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M. Mirazita

Publications and source records attributed to M. Mirazita.

82 records · Page 5Linked to original sources
arXiv2009

A measurement of the differential cross section for the reaction $γn \to π^{-} p$ from deuterium

We report a measurement of the differential cross section for the $γn \to π^- p$ process from the CLAS detector at Jefferson Lab in Hall B for photon energies between 1.0 and 3.5 GeV and pion center-of-mass (c.m.) angles ($θ_{c.m.}$) between 50$^\circ$ and 115$^\circ$. We confirm a previous indication of a broad enhancement around a c.m. energy ($\sqrt{s}$) of 2.2 GeV at $θ_{c.m.}=90^\circ$ in the scaled differential cross section, $s^7 {\frac{dσ}{dt}}$. Our data show the angular dependence of this enhancement as the scaling region is approached in the kinematic region from 70$^\circ$ to 105$^\circ$.

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arXiv2005

Comparative Regge analysis of $Λ, Σ^0, Λ(1520)$ and $Θ^+$ production in $γp$, $πp$ and $pp$ reactions

Using the Quark-Gluon Strings Model -- combined with Regge phenomenology -- we perform a comparative analysis of $Λ$, $Σ^0$, $Λ(1520)$ and $Θ^+$ production in binary reactions induced by photon, pion and proton beams on the nucleon. We find that the existing experimental data on the $γp \to K^+ Λ$ differential and total cross sections can be described very well by the model for photon energies $1 - 16$ GeV and $-t < 2$ GeV$^2$ assuming a dominant contribution of the $K^*$ Regge trajectory. Moreover, using the same parameters we also reproduce the total $γp \to K^+ Σ^0$ and $γp \to K^+ Λ(1520)$ cross sections suggesting a 'universality' of the Regge model. In order to check the consistency of the approach we evaluate the differential and total cross sections for the reaction $π^- p \to K^0 Λ$ which is also found to be dominated by the $K^*$ Regge trajectory. Using the apparent 'universality' of the Regge model we extend our scheme to the analysis of the binary reactions $γp \to \bar{K}^0 Θ^+$, $π^- p \to K^- Θ^+$ and $pp \to Σ^+ Θ^+$ as well as the exclusive and inclusive $Θ^+$ production in the reactions $pp \to p \bar{K}^0 Θ^+$ and $pp \to Θ^+ X$. Our detailed studies demonstrate that $Θ^+$ production does not follow the 'universality' principle thus suggesting an essentially different internal structure of the exotic baryon relative to conventional hyperons or hyperon resonances.

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arXiv2004

Complete Angular Distribution Measurements of Two-Body Deuteron Photodisintegration between 0.5 and 3 GeV

Nearly complete angular distributions of the two-body deuteron photodisintegration differential cross section have been measured using the CLAS detector and the tagged photon beam at JLab. The data cover photon energies between 0.5 and 3.0 GeV and center-of-mass proton scattering angles 10-160 degrees. The data show a persistent forward-backward angle asymmetry over the explored energy range, and are well-described by the non-perturbative Quark Gluon String Model.

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arXiv2004

The CLAS Electromagnetic Calorimeter at Large Angles

The study of the response of the two modules of the large-angle electromagnetic shower calorimeter (LAC) of the CLAS detector to charged and neutral particles is reported. The results agree very well with the Monte Carlo simulation. The procedures adopted for the energy and timing calibration are also discussed, proving that the module geometry allows for simple self-calibrating energy and timing algorithms.

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arXiv2003

Forward-backward angle asymmetry and polarization observables in high-energy deuteron photodisintegration

Deuteron two-body photodisintegration is analysed within the framework of the Quark-Gluon Strings Model. It is found that the forward-backward angle asymmetry predicted by the model is confirmed by the recent data at different photon energies from Jlab. New calculations for polarization observables, the cross section asymmetry $Σ$ and the polarization transfer $C_{z^{\prime}}$, for photon energies $(1.2\div6)$ GeV are presented and compared with the data available up to 2 GeV.

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arXiv2002

Polarization observables in high-energy deuteron photodisintegration within the Quark-Gluon Strings Model

Deuteron two-body photodisintegration is analysed within the framework of the Quark-Gluon Strings Model. The model describes fairly well the recent experimental data from TJNAF in the few GeV region. Angular distributions at different $γ$-energies are presented and the effect of a forward-backward asymmetry is discussed. New results from the QGSM for polarization observables from 1.5 -- 6 GeV are presented and compared with the available data.

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arXiv1999

Shadowing in the nuclear photoabsorption above the resonance region

A model based on the hadronic fluctuations of the real photon is developed to describe the total photonucleon and photonuclear cross sections in the energy region above the nucleon resonances. The hadronic spectral function of the photon is derived including the finite width of vector-meson resonances and the quark-antiquark continuum. The shadowing effect is evaluated considering the effective interaction of the hadronic component with the bound nucleons within a Glauber-Gribov multiple scattering theory. The low energy onset of the shadowing effect is interpreted as a possible signature of a modification of the hadronic spectral function in the nuclear medium. A decrease of the $ρ$-meson mass in nuclei is suggested for a better explanation of the experimental data.

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arXiv1998

Photoabsorption on nuclei in the shadowing threshold region

The energy and nuclear mass dependences of the total hadronic cross section in the energy range 0.5-2.6 GeV have been measured at Bonn using the SAPHIR tagged photon beam. The measurement, performed on C, Al, Cu, Sn and Pb, provides the first photoabsorption data in the region 1.2-1.7 GeV. The results show a significant reduction of the photoabsorption strength on the bound nucleon compared to the free nucleon case in the whole energy region. Above 1.2 GeV this reduction decreases with the nuclear density and can be interpreted as a signature of a low energy onset of the shadowing effect.

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arXiv1998

Determination of the forward Compton scattering amplitudes for C and Pb

The forward Compton scattering amplitude for carbon and lead have been calculated from total photoabsorption cross section data by using dispersion relations. The results show a large difference between the scattering amplitudes for nuclei and the free nucleon, above the $Δ$ region. The forward Compton scattering cross sections have been calculated and compared with the available data. The Weise sum rule is discussed together with the prediction of a recent theoretical model.

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