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Marcia Begalli

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Somayeh Gholami

Tehran University of Medical Sciences

Hosein Poorbaygi

Said ELBOUKHARI

Anatoly Rozenfeld(Rosenfeld)

University of Wollongong

Brigitte Reniers

Christos Antypas

Angelos Angelopoulos

National & Kapodistrian University of Athens

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Papers by Marcia Begalli

Monte Carlo simulation of an Ir-192 brachytherapy source spectra, geometry and anysotropy factors using GEANT4 code

2008 IEEE Nuclear Science Symposium Conference Record, 2008

In brachytherapy cancer treatments, methods of calculation of dose delivered to tumours and organ... more In brachytherapy cancer treatments, methods of calculation of dose delivered to tumours and organs have been continuously improved. The goal of calculations is the maximization of dose deposition in the target volume, while minimizing the deposition in the healthy tissues. The use of interstitial brachytherapy sources follows the recommendations of AAPM REPORT Nº 51. The present work is based on Monte Carlo simulations with GEANT4 code for the transport of subatomic particles in matter. This code incorporates a number of physical processes, presenting many important characteristics for medical applications, due to its precision in the treatment of geometries, materials, particle trajectories inside the volumes, particle fields, energy range, visualization of events, etc. Iridium-192 MicroSelectron HDR source was simulated and the geometry of dose deposition in media and primary spectra were obtained. Calculations also include photon-fluence distributions at two radial distances and accumulated air Kerma. A matrix of radial and angular coordinates was constructed, obtaining the Geometry Factor G(r,θ), the Anisotropy Function F(r,θ) and the Radial Dose Function g(r,θ) needed for dosimetry calculations, adopting the AAPM REPORT Nº 51 recommendations.

Universidade do Estado do Rio de Janeiro (Brazil)

We study the possible direct single production of a double-charged Higgs boson in e e collisions ... more

A determination of the centre-of-mass energy at LEP2 using radiative two-fermion events

The European Physical Journal C, 2006

Using e + e − → µ + µ − (γ) and e + e − → qq(γ) events radiative to the Z pole, Delphi has determ... more Using e + e − → µ + µ − (γ) and e + e − → qq(γ) events radiative to the Z pole, Delphi has determined the centre-of-mass energy, √ s, using energy and momentum constraint methods. The results are expressed as deviations from the nominal Lep centre-of-mass energy, measured using other techniques. The results are found to be compatible with the Lep Energy Working Group estimates for a combination of the 1997 to 2000 data sets.

Measurement of the forward backward asymmetry of c andb quarks at the Z pole using reconstructed D mesons

The European Physical Journal C, 1999

A measurement of the forward-backward asymmetry of e + e − → cc and e + e − → bb on the Z resonan... more A measurement of the forward-backward asymmetry of e + e − → cc and e + e − → bb on the Z resonance is performed using about 3.5 million hadronic Z decays collected by the DELPHI detector at LEP in the years 1992 to 1995. The heavy quark is tagged by the exclusive reconstruction of several D meson decay modes. The forward-backward asymmetries for c and b quarks at the Z resonance are determined to be: iii

Observation of the muon inner bremsstrahlung at LEP1

The European Physical Journal C, 2008

Object oriented design of anthropomorphic phantoms and GEANT4-based implementations

… Methods and Reactor …

Various models of anthropomorphic phantoms have been developed in the past decades for usage in M... more Various models of anthropomorphic phantoms have been developed in the past decades for usage in Monte Carlo simulation for radiation protection and other medical physics applications; they adopt two alternative approaches, either modelling the body components through analytical geometrical representations or through voxelized geometries. An original system has been developed associated with the use of the Geant4 simulation toolkit. It exploits Geant4 advanced capabilities to model geometrical components, and the object oriented technology to provide a variety of models of the human body usable in a simulation application. The flexible software design allows the creation of both analytical and voxel phantoms. The system allows the creation of phantoms of different sex and age; phantoms based on established models are provided, as well as the option for the user to assemble customized phantoms.

Quantifying the Unknown: Issues in Simulation Validation and Their Experimental Impact

Astroparticle, Particle, Space Physics, Radiation Interaction, Detectors and Medical Physics Applications, 2012

The assessment of the reliability of Monte Carlo simulations is discussed, with emphasis on uncer... more The assessment of the reliability of Monte Carlo simulations is discussed, with emphasis on uncertainty quantification and the related impact on experimental results. Methods and techniques to account for epistemic uncertainties, i.e. for intrinsic knowledge gaps in physics modeling, are discussed with the support of applications to concrete experimental scenarios. Ongoing projects regarding the investigation of epistemic uncertainties in the Geant4 simulation toolkit are reported.

$Research paper thumbnail of W pair production cross-section and W branching fractions in e+ e− interactions at 189 GeV$

W pair production cross-section and W branching fractions in e+ e− interactions at 189 GeV

Physics Letters B, 2000

The cross-section for the doubly resonant production of W bosons has been measured with the data ... more

Observation of the muon inner bremsstrahlung at LEP1

European Physical Journal C, 2008

$Research paper thumbnail of Search for supersymmetric particles assuming R-parity non-conservation in e + e- collisions at $\sqrt{s} = 192$ to 208 GeV$

Search for supersymmetric particles assuming R-parity non-conservation in e + e- collisions at $\sqrt{s} = 192$ to 208 GeV

The European Physical Journal C, 2004

Searches for pair-production of supersymmetric particles under the assumption of non-conservation... more Searches for pair-production of supersymmetric particles under the assumption of non-conservation of R-parity with a dominant LLĒ orŪDD term have been performed using the data collected by the DELPHI experiment at LEP in e + e − collisions at centre-of-mass energies from 192 up to 208 GeV. No excess of data above Standard Model expectations was observed. The results were used to constrain the MSSM parameter space and to derive limits on the masses of supersymmetric particles.

A determination of the centre-of-mass energy at LEP2 using radiative two-fermion events

Using e + e − → µ + µ − (γ) and e + e − → qq(γ) events radiative to the Z pole, Delphi has determ... more Using e + e − → µ + µ − (γ) and e + e − → qq(γ) events radiative to the Z pole, Delphi has determined the centre-of-mass energy, √ s, using energy and momentum constraint methods. The results are expressed as deviations from the nominal Lep centre-of-mass energy, measured using other techniques. The results are found to be compatible with the Lep Energy Working Group estimates for a combination of the 1997 to 2000 data sets.

Validation of Geant4 Electron Pair Production by Photons

The first results of a project in progress for the validation of the simulation of electron-posit... more The first results of a project in progress for the validation of the simulation of electron-positron pair production are presented. They concern the pair production cross section in a low energy range close to the production threshold. The results hint to effects due to the granularity of tabulated cross sections.

Measurements of CP-conserving Trilinear Gauge Boson Couplings WWV (V …

Measurements

The data taken by Delphi at centre-of-mass energies between 189 and 209 GeV are used to place lim... more

Particles and fields. Proceedings of the X Jorge André Swieca summer school, São Paulo, Brazil, February 6–12, 1999

Validation of Geant4 Electron Pair Production by Photons

The first results of a project in progress for the validation of the simulation of electron-posit... more The first results of a project in progress for the validation of the simulation of electron-positron pair production are presented. They concern the pair production cross section in a low energy range close to the production threshold. The results hint to effects due to the granularity of tabulated cross sections.

Search for Heavy Neutral Higgs Bosons in 2-DOUBLET Models

Zeitschrift für Physik C

A search for pair production of neutral heavy Higgs bosons decaying into <b(b)over bar> has... more A search for pair production of neutral heavy Higgs bosons decaying into <b(b)over bar> has been carried out in a study of hadronic decays of the Z boson into four jet final states using data taken by DELPHI in 1991 and 1992. The two production mechanisms present in the two Higgs doublets scheme, bremsstrahlung production of hZ* and associated production of hA, may lead to four beauty jets well recognizable using the precise microvertex detector measurements. No evidence for a signal was found, leading to limits on BR(Z -->, hA --> 4b) from 3.5 to 5.5 x 10(-4) at 95% confidence level, depending on the mass of the ligthest Higgs. When combined with the results of the recent DELPHI standard Higgs search, this result allows the kinematical limit to be reached for the masses of h and A in the minimal supersymmetric extension of the Standard Model (MSSM) scheme. It also allows the tan beta less than or equal to 1 domain to be explored, and a region above the kinematic limit f...

$Research paper thumbnail of Measurement of the $e^+ e^- \to \gamma\gamma (\gamma)$ cross section at the LEP energies$

Measurement of the $e^+ e^- \to \gamma\gamma (\gamma)$ cross section at the LEP energies

The total and the differential cross-sections for the reaction $e^+e^-\rightarrow \gamma\gamma(\g... more The total and the differential cross-sections for the reaction $e^+e^-\rightarrow \gamma\gamma(\gamma)$ have been measured with the DELPHI detector at LEP % with at centre-of-mass energies from 1 30 %, 136, 161, 172 and to 183 GeV for an integrated luminosity of 78.19.~pb$^{-1}$. %CR An agreement with the QED predictions was found and consequently The results agree with the QED prediction s. The lower limits (obtained including previously published results at the $\Zzero$ energies) on the QED cutoff parameters are $\Lambda_{+} > 253$~GeV and $\Lambda_{-} > 225$~GeV and the lower bo und on the mass of an excited electron with an effective coupling constant $\lambda_{\gamma} = 1$ is 231~GeV/$c^2$. %Upper limits on the branching ratios for the decays ${\rm Z}^0\rightarrow %\gam ma\gamma$, ${\rm Z}^0\rightarrow \pi^0\gamma$, % ${\rm Z}^0\rightarrow \eta\gamma$ %and ${\rm Z}^0\rightarrow \gamma\gamma\gamma$ have been determined to be 2.5 % $\times$ $10^{-5}$, 2.5 $\times$ $ 10^{-5}...

B-asterisk production in Z-Decays

ABSTRACT The decay B* --&gt; B gamma has been observed with the DELPHI detector at LEP, where... more ABSTRACT The decay B* --&gt; B gamma has been observed with the DELPHI detector at LEP, where the B* meson is produced in Z boson decays, The combination of inclusively reconstructed B mesons with well-measured converted photons yields a measurement of the flavour-averaged B* - B mass difference of 45.5 +/- 0.3 (stat.) +/- 0.8 (syst.) MeV/c(2). 95% confidence level upper limits at 6 MeV/c(2) are placed on both the isospin (i.e, B+-B-0) and the B-s-B-ud splitting of the mass difference, The production ratio of B* to B mesons in Z decays is measured to be 0.72 +/- 0.03 (stat.) +/- 0.06 (syst.). Limits on the production cross-section of other hypothetical excited B hadron states decaying radiatively are established. The differential B* cross section has been measured to be in good agreement with the average b fragmentation, yielding an average fractional B* energy of [x(E)] = 0.695 +/- 0.009 (stat.) +/- 0.013 (syst.). From the decay angular distribution the relative contribution of longitudinal B* polarisation states is measured to be sigma(L)/(sigma(L) + sigma(T)) = 0.32 +/- 0.04 (stat.) +/- 0.03 (syst.).

Rapidity-rank structure of p

Physics Letters B

The rapidity-rank structure of pp¯ pairs is used to analyze the mechanism of baryon production in... more The rapidity-rank structure of pp¯ pairs is used to analyze the mechanism of baryon production in hadronic Z0 decay. The relative occurrence of the rapidity-ordered configuration pMp¯, where /M is a meson, and that of pp¯ adjacent pairs is compared. The data are found to be consistent with predictions from a mechanism producing adjacent-rank pp¯ pairs, without requiring `string-ordered' pMp¯ configurations. An upper limit of 15% at 90% confidence is determined for the pMp¯ contribution.

$Research paper thumbnail of Measurement of the partial width of the Z0 into b$\overline{b}$ final states using their semi-leptonic decays$

Measurement of the partial width of the Z0 into b$\overline{b}$ final states using their semi-leptonic decays

Monte Carlo simulation of an Ir-192 brachytherapy source spectra, geometry and anysotropy factors using GEANT4 code

2008 IEEE Nuclear Science Symposium Conference Record, 2008

In brachytherapy cancer treatments, methods of calculation of dose delivered to tumours and organ... more In brachytherapy cancer treatments, methods of calculation of dose delivered to tumours and organs have been continuously improved. The goal of calculations is the maximization of dose deposition in the target volume, while minimizing the deposition in the healthy tissues. The use of interstitial brachytherapy sources follows the recommendations of AAPM REPORT Nº 51. The present work is based on Monte Carlo simulations with GEANT4 code for the transport of subatomic particles in matter. This code incorporates a number of physical processes, presenting many important characteristics for medical applications, due to its precision in the treatment of geometries, materials, particle trajectories inside the volumes, particle fields, energy range, visualization of events, etc. Iridium-192 MicroSelectron HDR source was simulated and the geometry of dose deposition in media and primary spectra were obtained. Calculations also include photon-fluence distributions at two radial distances and accumulated air Kerma. A matrix of radial and angular coordinates was constructed, obtaining the Geometry Factor G(r,θ), the Anisotropy Function F(r,θ) and the Radial Dose Function g(r,θ) needed for dosimetry calculations, adopting the AAPM REPORT Nº 51 recommendations.

Universidade do Estado do Rio de Janeiro (Brazil)

We study the possible direct single production of a double-charged Higgs boson in e e collisions ... more

A determination of the centre-of-mass energy at LEP2 using radiative two-fermion events

The European Physical Journal C, 2006

Using e + e − → µ + µ − (γ) and e + e − → qq(γ) events radiative to the Z pole, Delphi has determ... more Using e + e − → µ + µ − (γ) and e + e − → qq(γ) events radiative to the Z pole, Delphi has determined the centre-of-mass energy, √ s, using energy and momentum constraint methods. The results are expressed as deviations from the nominal Lep centre-of-mass energy, measured using other techniques. The results are found to be compatible with the Lep Energy Working Group estimates for a combination of the 1997 to 2000 data sets.

Measurement of the forward backward asymmetry of c andb quarks at the Z pole using reconstructed D mesons

The European Physical Journal C, 1999

A measurement of the forward-backward asymmetry of e + e − → cc and e + e − → bb on the Z resonan... more A measurement of the forward-backward asymmetry of e + e − → cc and e + e − → bb on the Z resonance is performed using about 3.5 million hadronic Z decays collected by the DELPHI detector at LEP in the years 1992 to 1995. The heavy quark is tagged by the exclusive reconstruction of several D meson decay modes. The forward-backward asymmetries for c and b quarks at the Z resonance are determined to be: iii

Observation of the muon inner bremsstrahlung at LEP1

The European Physical Journal C, 2008

Object oriented design of anthropomorphic phantoms and GEANT4-based implementations

… Methods and Reactor …

Various models of anthropomorphic phantoms have been developed in the past decades for usage in M... more Various models of anthropomorphic phantoms have been developed in the past decades for usage in Monte Carlo simulation for radiation protection and other medical physics applications; they adopt two alternative approaches, either modelling the body components through analytical geometrical representations or through voxelized geometries. An original system has been developed associated with the use of the Geant4 simulation toolkit. It exploits Geant4 advanced capabilities to model geometrical components, and the object oriented technology to provide a variety of models of the human body usable in a simulation application. The flexible software design allows the creation of both analytical and voxel phantoms. The system allows the creation of phantoms of different sex and age; phantoms based on established models are provided, as well as the option for the user to assemble customized phantoms.

Quantifying the Unknown: Issues in Simulation Validation and Their Experimental Impact

Astroparticle, Particle, Space Physics, Radiation Interaction, Detectors and Medical Physics Applications, 2012

The assessment of the reliability of Monte Carlo simulations is discussed, with emphasis on uncer... more The assessment of the reliability of Monte Carlo simulations is discussed, with emphasis on uncertainty quantification and the related impact on experimental results. Methods and techniques to account for epistemic uncertainties, i.e. for intrinsic knowledge gaps in physics modeling, are discussed with the support of applications to concrete experimental scenarios. Ongoing projects regarding the investigation of epistemic uncertainties in the Geant4 simulation toolkit are reported.

$Research paper thumbnail of W pair production cross-section and W branching fractions in e+ e− interactions at 189 GeV$

W pair production cross-section and W branching fractions in e+ e− interactions at 189 GeV

Physics Letters B, 2000

The cross-section for the doubly resonant production of W bosons has been measured with the data ... more

Observation of the muon inner bremsstrahlung at LEP1

European Physical Journal C, 2008

$Research paper thumbnail of Search for supersymmetric particles assuming R-parity non-conservation in e + e- collisions at $\sqrt{s} = 192$ to 208 GeV$

Search for supersymmetric particles assuming R-parity non-conservation in e + e- collisions at $\sqrt{s} = 192$ to 208 GeV

The European Physical Journal C, 2004

Searches for pair-production of supersymmetric particles under the assumption of non-conservation... more Searches for pair-production of supersymmetric particles under the assumption of non-conservation of R-parity with a dominant LLĒ orŪDD term have been performed using the data collected by the DELPHI experiment at LEP in e + e − collisions at centre-of-mass energies from 192 up to 208 GeV. No excess of data above Standard Model expectations was observed. The results were used to constrain the MSSM parameter space and to derive limits on the masses of supersymmetric particles.

A determination of the centre-of-mass energy at LEP2 using radiative two-fermion events

Using e + e − → µ + µ − (γ) and e + e − → qq(γ) events radiative to the Z pole, Delphi has determ... more Using e + e − → µ + µ − (γ) and e + e − → qq(γ) events radiative to the Z pole, Delphi has determined the centre-of-mass energy, √ s, using energy and momentum constraint methods. The results are expressed as deviations from the nominal Lep centre-of-mass energy, measured using other techniques. The results are found to be compatible with the Lep Energy Working Group estimates for a combination of the 1997 to 2000 data sets.

Validation of Geant4 Electron Pair Production by Photons

The first results of a project in progress for the validation of the simulation of electron-posit... more The first results of a project in progress for the validation of the simulation of electron-positron pair production are presented. They concern the pair production cross section in a low energy range close to the production threshold. The results hint to effects due to the granularity of tabulated cross sections.

Measurements of CP-conserving Trilinear Gauge Boson Couplings WWV (V …

Measurements

The data taken by Delphi at centre-of-mass energies between 189 and 209 GeV are used to place lim... more

Particles and fields. Proceedings of the X Jorge André Swieca summer school, São Paulo, Brazil, February 6–12, 1999

Validation of Geant4 Electron Pair Production by Photons

The first results of a project in progress for the validation of the simulation of electron-posit... more The first results of a project in progress for the validation of the simulation of electron-positron pair production are presented. They concern the pair production cross section in a low energy range close to the production threshold. The results hint to effects due to the granularity of tabulated cross sections.

Search for Heavy Neutral Higgs Bosons in 2-DOUBLET Models

Zeitschrift für Physik C

A search for pair production of neutral heavy Higgs bosons decaying into <b(b)over bar> has... more A search for pair production of neutral heavy Higgs bosons decaying into <b(b)over bar> has been carried out in a study of hadronic decays of the Z boson into four jet final states using data taken by DELPHI in 1991 and 1992. The two production mechanisms present in the two Higgs doublets scheme, bremsstrahlung production of hZ* and associated production of hA, may lead to four beauty jets well recognizable using the precise microvertex detector measurements. No evidence for a signal was found, leading to limits on BR(Z -->, hA --> 4b) from 3.5 to 5.5 x 10(-4) at 95% confidence level, depending on the mass of the ligthest Higgs. When combined with the results of the recent DELPHI standard Higgs search, this result allows the kinematical limit to be reached for the masses of h and A in the minimal supersymmetric extension of the Standard Model (MSSM) scheme. It also allows the tan beta less than or equal to 1 domain to be explored, and a region above the kinematic limit f...

$Research paper thumbnail of Measurement of the $e^+ e^- \to \gamma\gamma (\gamma)$ cross section at the LEP energies$

Measurement of the $e^+ e^- \to \gamma\gamma (\gamma)$ cross section at the LEP energies

The total and the differential cross-sections for the reaction $e^+e^-\rightarrow \gamma\gamma(\g... more The total and the differential cross-sections for the reaction $e^+e^-\rightarrow \gamma\gamma(\gamma)$ have been measured with the DELPHI detector at LEP % with at centre-of-mass energies from 1 30 %, 136, 161, 172 and to 183 GeV for an integrated luminosity of 78.19.~pb$^{-1}$. %CR An agreement with the QED predictions was found and consequently The results agree with the QED prediction s. The lower limits (obtained including previously published results at the $\Zzero$ energies) on the QED cutoff parameters are $\Lambda_{+} > 253$~GeV and $\Lambda_{-} > 225$~GeV and the lower bo und on the mass of an excited electron with an effective coupling constant $\lambda_{\gamma} = 1$ is 231~GeV/$c^2$. %Upper limits on the branching ratios for the decays ${\rm Z}^0\rightarrow %\gam ma\gamma$, ${\rm Z}^0\rightarrow \pi^0\gamma$, % ${\rm Z}^0\rightarrow \eta\gamma$ %and ${\rm Z}^0\rightarrow \gamma\gamma\gamma$ have been determined to be 2.5 % $\times$ $10^{-5}$, 2.5 $\times$ $ 10^{-5}...

B-asterisk production in Z-Decays

ABSTRACT The decay B* --&gt; B gamma has been observed with the DELPHI detector at LEP, where... more ABSTRACT The decay B* --&gt; B gamma has been observed with the DELPHI detector at LEP, where the B* meson is produced in Z boson decays, The combination of inclusively reconstructed B mesons with well-measured converted photons yields a measurement of the flavour-averaged B* - B mass difference of 45.5 +/- 0.3 (stat.) +/- 0.8 (syst.) MeV/c(2). 95% confidence level upper limits at 6 MeV/c(2) are placed on both the isospin (i.e, B+-B-0) and the B-s-B-ud splitting of the mass difference, The production ratio of B* to B mesons in Z decays is measured to be 0.72 +/- 0.03 (stat.) +/- 0.06 (syst.). Limits on the production cross-section of other hypothetical excited B hadron states decaying radiatively are established. The differential B* cross section has been measured to be in good agreement with the average b fragmentation, yielding an average fractional B* energy of [x(E)] = 0.695 +/- 0.009 (stat.) +/- 0.013 (syst.). From the decay angular distribution the relative contribution of longitudinal B* polarisation states is measured to be sigma(L)/(sigma(L) + sigma(T)) = 0.32 +/- 0.04 (stat.) +/- 0.03 (syst.).

Rapidity-rank structure of p

Physics Letters B

The rapidity-rank structure of pp¯ pairs is used to analyze the mechanism of baryon production in... more The rapidity-rank structure of pp¯ pairs is used to analyze the mechanism of baryon production in hadronic Z0 decay. The relative occurrence of the rapidity-ordered configuration pMp¯, where /M is a meson, and that of pp¯ adjacent pairs is compared. The data are found to be consistent with predictions from a mechanism producing adjacent-rank pp¯ pairs, without requiring `string-ordered' pMp¯ configurations. An upper limit of 15% at 90% confidence is determined for the pMp¯ contribution.

$Research paper thumbnail of Measurement of the partial width of the Z0 into b$\overline{b}$ final states using their semi-leptonic decays$

Measurement of the partial width of the Z0 into b$\overline{b}$ final states using their semi-leptonic decays