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10h
Marie VANSTALLE
"Suivi du pic de Bragg par détection des particules secondaires émises par la fragmentation du 12C"
La détermination de la position du pic de Bragg est un sujet primordial dans le traitement des cancers par thérapie par ions légers (12C, 16O,...). En effet, il permet d’être certain de déposer la dose maximale dans la tumeur et non pas dans les tissus sains périphériques. Actuellement, seule la méthode TEP est utilisée pour vérifier cette position : les différences entre le profil d’annihilation TEP et les calculs du plan de traitement permettent d’estimer qualitativement les erreurs entre la dose effectivement délivrée et la dose prévue. La connaissance du positionnement du pic de Bragg en temps réel devrait permettre de corriger en direct le plan de traitement, et non pas a posteriori (cas actuel), ce qui améliorerait considérablement la qualité du traitement. Un des handicaps de la hadronthérapie est la fragmentation : les interactions inélastiques entre le projectile et la cible produisent des particules secondaires plus légères qui vont avoir un parcours distinct des ions incidents et, par conséquent, un dépôt de dose différent. Cependant, dans le cas du suivi temps réel de la dose absorbée, la fragmentation peut devenir un avantage. En effet, la position du pic de Bragg peut être connue via la détection des particules secondaires (protons ou gamma prompts) créées par l’interaction du faisceau avec le patient. Une expérience a été menée en mai 2012 à GSI, en collaboration avec l’Université la Sapienza de Rome et le groupe PICSEL de Strasbourg, afin de déterminer la position du pic de Bragg d’une part par le taux de production des gammas prompts en fonction de la profondeur de la cible, et d’autre part par la reconstruction des trajectoires des protons secondaires. Au cours de ce séminaire, je présenterai les résultats préliminaires de cette expérience, notamment les spectres en énergie obtenus pour les gammas prompts émis à 90° et 60° par rapport à l’axe du faisceau, et également le profil d’émission de ces gammas. Ces résultats seront confrontés à des simulations Monte Carlo effectuées avec GEANT4 et/ou FLUKA. Je présenterai aussi les derniers résultats préliminaires obtenus pour les protons secondaires (spectres en énergie, taux de production).
Imma MARTINEZ
"Towards the improvement of the therapeutic in radiotherapy"
Despite intensive research and development in radiotherapy methods, there are still some radioresistant tumours for which radical treatment is not feasible at hospitals. In the quest for ways to improve the therapeutic index for such tumours, new approaches are explored. Synchrotron radiation therapies and hadron therapy are two examples. The first part of my work is framed within the medical physics developments aimed at the preparation of forthcoming clinical trials in synchrotron radiotherapy techniques. To this end, both Monte Carlo simulations and experimental dosimetry studies were performed for an accurate dose assessment. The main part consists in the development and experimental benchmarking of a Monte Carlo-based Treatment Planning System (TPS), along with the establishment of dosimetry protocols. The second part of my work is devoted to the use Monte Carlo techniques to investigate the imaging-based therapeutic control of hadron therapy by using Position Emission Tomography (PET). With the aim of improving the accuracy of this method, the 'washout' processes, which are related to perfusion of the positron emitters, have been implemented in the Geant4/Gate code. The effect of these processes in the PET images and in the capability of providing an accurate information regarding the absolute dose and its spatial distribution after image reconstruction have been assessed.
Manuela VECCHI
14h
Dimitris VAROUCHAS
"Search for the Standard Model Higgs boson in H-> tau tau decays with the ATLAS detector"
In this seminar, a search for the Standard Model (SM) Higgs boson decaying into a pair of tau leptons will be reported. The analysis is based on data samples of p-p collisions collected by the ATLAS experiment at the LHC and corresponding to integrated luminosities of 4.6 ifb and 13.0 ifb at centre-of-mass energies of sqrt(s)=7 TeV and 8 TeV, respectively. The observed (expected) upper limit at 95% CL on the cross-section times the branching ratio for SM H→τ+τ− is found to be 1.9 (1.2) times the SM prediction for a Higgs boson with mass mH=125~GeV. For this mass, the observed (expected) deviation from the background-only hypothesis corresponds to a local significance of 1.1 (1.7) standard deviations.
George AAD
"Search for the Higgs boson decaying into a pair of b-jets and measurements of the cross sections of W bosons produced in association with heavy flavor jets with the ATLAS detector."
Establishing the presence of a Standard Model Higgs boson is one of the most interesting subjects with LHC data collected in 2012. ATLAS and CMS discovered a new boson in July 2012 with a mass around 125 GeV. The new boson is observed decaying into a pair of photons, two Z bosons (4 leptons) and two W bosons (2 leptons and missing energy). The decay into fermions (pair of b-quarks or tau-leptons) is not yet observed at the LHC. The observation of the new boson decaying into a pair of b-quarks is mandatory to establish the presence of a Standard Model Higgs boson. The H-> bb presents the largest branching ratio at mH=125 GeV and thus it is particularly important for a precise measurement of the couplings in the Higgs sector. I will present the status of the search for the Higgs boson in the VH(H->bb) channels with the ATLAS experiment. The production of W bosons in association with heavy flavor jets is one of the most important backgrounds for the WH(H->bb) channel. These process also constitute a test of pQCD. I will present ATLAS measurements for the W + heavy flavor production cross sections.
Andrea COCCARO
"The understanding of the Electroweak Symmetry Breaking after the discovery of a Higgs-like boson with the ATLAS detector"
A new era of precise measurements in particle physics undoubtedly began with the discovery of the Higgs-like particle announced by both the ATLAS and CMS collaborations on July 4th, 2012. The new discovered particle resembles in many ways the Higgs boson responsible of the Electroweak Symmetry Breaking (EWSB) in the Standard Model (SM) even if its discovery was only driven by the most sensitive channels for the low-mass region, H->gammagamma and H->ZZ->4l. Precise measurements of all the possible couplings with both SM and exotics particles and the determination of the mass, spin and parity represent the natural next steps ahead for the LHC community to deeply understand the EWSB in elementary particle physics. In this seminar, I will present my research project of probing the nature of the EWSB mechanism studying the H->bb decay mode to verify its couplings to fermions and studying an invisibly decaying Higgs boson with a branching ratio down to ~10% to explore possible new physics contributions beyond the SM. Different but complementary aspects of this project are all considered, e.g. the triggering strategies, the reconstruction techniques, the calibration of the b-tagging algorithms and the analysis techniques, since my interests spans in all these different activities.
Marie VANSTALLE
"Suivi du pic de Bragg par détection des particules secondaires émises par la fragmentation du 12C"
La détermination de la position du pic de Bragg est un sujet primordial dans le traitement des cancers par thérapie par ions légers (12C, 16O,...). En effet, il permet d’être certain de déposer la dose maximale dans la tumeur et non pas dans les tissus sains périphériques. Actuellement, seule la méthode TEP est utilisée pour vérifier cette position : les différences entre le profil d’annihilation TEP et les calculs du plan de traitement permettent d’estimer qualitativement les erreurs entre la dose effectivement délivrée et la dose prévue. La connaissance du positionnement du pic de Bragg en temps réel devrait permettre de corriger en direct le plan de traitement, et non pas a posteriori (cas actuel), ce qui améliorerait considérablement la qualité du traitement. Un des handicaps de la hadronthérapie est la fragmentation : les interactions inélastiques entre le projectile et la cible produisent des particules secondaires plus légères qui vont avoir un parcours distinct des ions incidents et, par conséquent, un dépôt de dose différent. Cependant, dans le cas du suivi temps réel de la dose absorbée, la fragmentation peut devenir un avantage. En effet, la position du pic de Bragg peut être connue via la détection des particules secondaires (protons ou gamma prompts) créées par l’interaction du faisceau avec le patient. Une expérience a été menée en mai 2012 à GSI, en collaboration avec l’Université la Sapienza de Rome et le groupe PICSEL de Strasbourg, afin de déterminer la position du pic de Bragg d’une part par le taux de production des gammas prompts en fonction de la profondeur de la cible, et d’autre part par la reconstruction des trajectoires des protons secondaires. Au cours de ce séminaire, je présenterai les résultats préliminaires de cette expérience, notamment les spectres en énergie obtenus pour les gammas prompts émis à 90° et 60° par rapport à l’axe du faisceau, et également le profil d’émission de ces gammas. Ces résultats seront confrontés à des simulations Monte Carlo effectuées avec GEANT4 et/ou FLUKA. Je présenterai aussi les derniers résultats préliminaires obtenus pour les protons secondaires (spectres en énergie, taux de production).
Imma MARTINEZ
"Towards the improvement of the therapeutic in radiotherapy"
Despite intensive research and development in radiotherapy methods, there are still some radioresistant tumours for which radical treatment is not feasible at hospitals. In the quest for ways to improve the therapeutic index for such tumours, new approaches are explored. Synchrotron radiation therapies and hadron therapy are two examples. The first part of my work is framed within the medical physics developments aimed at the preparation of forthcoming clinical trials in synchrotron radiotherapy techniques. To this end, both Monte Carlo simulations and experimental dosimetry studies were performed for an accurate dose assessment. The main part consists in the development and experimental benchmarking of a Monte Carlo-based Treatment Planning System (TPS), along with the establishment of dosimetry protocols. The second part of my work is devoted to the use Monte Carlo techniques to investigate the imaging-based therapeutic control of hadron therapy by using Position Emission Tomography (PET). With the aim of improving the accuracy of this method, the 'washout' processes, which are related to perfusion of the positron emitters, have been implemented in the Geant4/Gate code. The effect of these processes in the PET images and in the capability of providing an accurate information regarding the absolute dose and its spatial distribution after image reconstruction have been assessed.
Manuela VECCHI
"Detection of electrons and positrons with the AMS-02 detector in space."
The Alpha Magnetic Spectrometer (AMS-02) is a large acceptance particle physics detector, operating onboard the International Space Station (ISS) since May 19th 2011. The main goals of AMS-02 are the search for antimatter and dark matter, and the precise measurements of cosmic rays composition and flux. The study of the electromagnetic component of the cosmic rays, namely electrons, positrons and photons, is one of the main scientific targets of AMS, due to both the large statistics, as well as the subdetector redundancy and excellent energy resolution. The present seminary will describe the methods to identify electrons and positrons in cosmic rays in GeV to TeV region, and will describe the performances of AMS-02 in this context.
14h
Dimitris VAROUCHAS
"Search for the Standard Model Higgs boson in H-> tau tau decays with the ATLAS detector"
In this seminar, a search for the Standard Model (SM) Higgs boson decaying into a pair of tau leptons will be reported. The analysis is based on data samples of p-p collisions collected by the ATLAS experiment at the LHC and corresponding to integrated luminosities of 4.6 ifb and 13.0 ifb at centre-of-mass energies of sqrt(s)=7 TeV and 8 TeV, respectively. The observed (expected) upper limit at 95% CL on the cross-section times the branching ratio for SM H→τ+τ− is found to be 1.9 (1.2) times the SM prediction for a Higgs boson with mass mH=125~GeV. For this mass, the observed (expected) deviation from the background-only hypothesis corresponds to a local significance of 1.1 (1.7) standard deviations.
George AAD
"Search for the Higgs boson decaying into a pair of b-jets and measurements of the cross sections of W bosons produced in association with heavy flavor jets with the ATLAS detector."
Establishing the presence of a Standard Model Higgs boson is one of the most interesting subjects with LHC data collected in 2012. ATLAS and CMS discovered a new boson in July 2012 with a mass around 125 GeV. The new boson is observed decaying into a pair of photons, two Z bosons (4 leptons) and two W bosons (2 leptons and missing energy). The decay into fermions (pair of b-quarks or tau-leptons) is not yet observed at the LHC. The observation of the new boson decaying into a pair of b-quarks is mandatory to establish the presence of a Standard Model Higgs boson. The H-> bb presents the largest branching ratio at mH=125 GeV and thus it is particularly important for a precise measurement of the couplings in the Higgs sector. I will present the status of the search for the Higgs boson in the VH(H->bb) channels with the ATLAS experiment. The production of W bosons in association with heavy flavor jets is one of the most important backgrounds for the WH(H->bb) channel. These process also constitute a test of pQCD. I will present ATLAS measurements for the W + heavy flavor production cross sections.
Andrea COCCARO
"The understanding of the Electroweak Symmetry Breaking after the discovery of a Higgs-like boson with the ATLAS detector"
A new era of precise measurements in particle physics undoubtedly began with the discovery of the Higgs-like particle announced by both the ATLAS and CMS collaborations on July 4th, 2012. The new discovered particle resembles in many ways the Higgs boson responsible of the Electroweak Symmetry Breaking (EWSB) in the Standard Model (SM) even if its discovery was only driven by the most sensitive channels for the low-mass region, H->gammagamma and H->ZZ->4l. Precise measurements of all the possible couplings with both SM and exotics particles and the determination of the mass, spin and parity represent the natural next steps ahead for the LHC community to deeply understand the EWSB in elementary particle physics. In this seminar, I will present my research project of probing the nature of the EWSB mechanism studying the H->bb decay mode to verify its couplings to fermions and studying an invisibly decaying Higgs boson with a branching ratio down to ~10% to explore possible new physics contributions beyond the SM. Different but complementary aspects of this project are all considered, e.g. the triggering strategies, the reconstruction techniques, the calibration of the b-tagging algorithms and the analysis techniques, since my interests spans in all these different activities.
