Synchrotron radiation in a chromo-magnetic field

We study the generalization of QED synchrotron radiation to the QCD case with a chromomagnetic field using the Schwinger {\it et al} source method. It is shown that the QED case can be obtained as a special limit. The comparison with the path integral approach of Zakharov has shown consistent results.Comment: Accepted for publication in Phys. Rev.

Nucleon structure studies with the PANDA experiment at FAIR

The PANDA experiment is one of the major projects in preparation at the upcoming FAIR facility in Darmstadt, Germany. A multipurpose high energy physics detector is currently under construction and will be operated at the High Energy Storage Ring of FAIR. High intensity antiproton beams will be available in the momentum range between 1.5 GeV/c and 15 GeV/c and will allow to address a broad physics program including hadron spectroscopy, study of charm and strangeness in nuclei, hypernuclear physics and other QCD topics. In addition, the PANDA experiment will offer unique possibilities to investigate the structure of the proton using different electromagnetic processes. In this contribution, the PANDA physics program related to the nucleon structure aspects is discussed. Feasibility studies of electromagnetic processes for the measurements of proton electromagnetic form factors in the time-like region and the nucleon-to-meson transition distribution amplitudes at PANDA, are reported

Baryon electromagnetic form factors at BESIII

Electromagnetic form factors are fundamental quantities which parameterize the electric and magnetic structure of hadrons. This contribution reports on the measurements of baryon electromagnetic form factors at the BESIII experiment in Beijing. The Beijing e+e− collider BEPCII is a double-ring symmetric collider running at √s between 2.0 and 4.6 GeV. Baryon electromagnetic form factors can be measured at BESIII in direct e+e−-annihilation and in initial state radiation processes. Based on the data collected by the BESIII detector at 12 center of mass energies between 2.23 and 3.67 GeV, the e+e− → p̄p cross section and the time-like proton form factor is measured. Preliminary results from the analysis of the initial state radiation process e+e− → p̄pγ using a data set of 7.408 fb−1 collected at center-of-mass energies between 3.773 and 4.6 GeV, are also presented. The cross section for ${e^ + }{e^ - } \to \bar \Lambda \Lambda$ is measured based on 40.5 pb−1 data collected at 4 energy points from the threshold up to 3.08 GeV. Preliminary results on the total cross section and the Λ effective form factor are shown. Ongoing analysis based on the high luminosity energy scan from 2015 and from radiative return at different √s are also described

Etude de la strucutre interne du proton avec l'experience PANDA à FAIR

The proton is a bound state of quarks which are held together by the strong force, mediated by gluons. The understanding of the proton structure is presently one of the central issues in hadron physics. The present work reports on phenomenological and experimental studies related to the possibilities offered by the future antiproton beam at the FAIR facility at Darmstadt, in the momentum range between 1.5 and 15 GeV/c. After a classification of the reaction channels which are accessible in antiproton-proton annihilation, the main features of the PANDA detector are described. A chapter of this thesis is dedicated to the study of the optical coupling between crystals and photodiodes in the electromagnetic calorimeter, which will be operated at low temperature (-25° C). Mechanical, thermal, optical properties and radiation hardness of two commercial glues are quantified.Feasibility studies of the reaction barp → e+e− for the Time-Like proton form factor measurements at PANDA are presented. The electromagnetic structure of the proton is parametrized in terms of electric GE and magnetic GM form factors. The electromagnetic interaction is well described by the theory of quantum electrodynamics. The traditional tool to determine proton electromagnetic form factors is polarized and unpolarized electron-proton elastic scattering, assuming that the interaction occurs through the exchange of one virtual photon. The crossed symmetry channels pbarp ↔ e+e− allowto access the Time-Like region. The background reactions are also studied, in particular the pbarp → π+π− channel. The results obtained from a realistic Monte Carlo simulation using PANDARoot show that the proton form factor ratio can be measured at PANDA with unprecedented accuracy. The effects of radiative corrections due to real and virtual photon emission are considered.Based on a model independent formalism, the calculation of the experimental observables for the pbarp → e+e− reaction is extended to the annihilation into a heavy lepton pair which carries the same physical information on the proton structure as the electrons. In this case, the lepton mass can not be neglected. The same formalism is also applied in Space-Like region to the elastic scattering of protons from electrons at rest (pe-inverse kinematics). We suggest that the elastic pe scattering can be used to polarize and/or to measure the polarization of high energy proton (antiproton) beams, and allows a precise measurement of the proton charge radius.Le proton est un état lié de quarks qui sont maintenus ensemble par l’interaction forte dont les médiateurs sont les gluons. La compréhension de la structure du proton est actuellement l’une des questions centrales de laphysique hadronique. Le présent travail rend compte des études phénoménologiques et expérimentales reliées aux possibilités offertes par le faisceau d’antiprotons qui sera disponible au futur complexe accélérateur FAIR à Darmstadt, dans la gamme d’impulsion entre 1.5 et 15 GeV/c. Après une classification des réactions qui sont accessibles dans l’annihilation proton-antiproton, les caractéristiques principales du détecteur PANDA sont décrites. Un chapitre de cette thèse est consacré à l’étude du couplage optique entre les cristaux et les photo-diodes du calorimètre électromagnétique, qui sera exploité à basse température (-25° C). Les propriétés mécaniques, thermiques, optiques et la résistance aux radiations de deux colles commerciales sont quantifiées.Des études de faisabilité de la réaction pbarp → e+e− pour la mesure des facteurs de forme du proton dans la region temps à PANDA sont présentées. La structure électromagnétique du proton est parametrisée par ses facteurs de forme électrique GE et magnétique GM. L’interaction électromagnétique est bien décrite par la théorie de l’électrodynamique quantique. L’outil usuel pour déterminer les facteurs de forme électromagnétiques du proton est la diffusion élastique électron-proton polarisée et non polarisée, sous l’hypothèse que l’interaction se produit par l’échange d’un seul photon virtuel. La reaction croisée pbarp → e+e− permet d’accéder à la region temps. Les réactions du bruit de fond sont également étudiées, en particulier la réaction pbap → π+π−. Les résultats obtenus à partir d’une simulation Monte Carlo réaliste en utilisant le logiciel PANDARoot montre que le rapport des facteurs de forme du proton peut etre mesuré à PANDA avec une précision sans précédent. Les effets des corrections radiatives dus à l’émission de photons réels et virtuels sont considérés.Basé sur un formalisme modèle indépendant, le calcul des observables expérimentales pour la reaction pbap → e+e− est étendue à l’annihilation en une paire de leptons lourds qui porte la méme information physique sur la structure du proton que les électrons. Dans ce cas, la masse du lepton ne peut pas etre négligée. Le méme formalisme est également appliqué dans la région espace à la diffusion élastique des protons par des électrons au repos (cinématique inverse). La diffusion pe-élastique puisse etre utilisée pour polariser et/ou mesurer la polarisation des faisceaux de protons (antiprotons)de haute énergie, et elle permette également de mesurer le rayon de charge du proton

BESIII results on time-like baryon form factors

This contribution reports on the recent measurements of baryon electromagnetic form factors at the BESIII experiment in Beijing. The Beijing e+e − collider BEPCII is a double-ring symmetric collider running at $\sqrt s$ between 2.0 and 4.6 GeV. Baryon electromagnetic form factors can be measured at BESIII in direct e+e−-annihilation and in initial state radiation processes. Based on the data collected by the BESIII detector at 12 center of mass energies between 2.23 and 3.67 GeV, the measured $\mathop e\nolimits^ + \mathop e\nolimits^ - \to \mathop p\limits^ - p$ cross section and the time-like proton form factor are presented. Preliminary results from the analysis of the initial state radiation process $\mathop e\nolimits^ + \mathop e\nolimits^ - \to \mathop p\limits^ - p\gamma$ using a data set of 7.408 fb−1 collected at center of mass energies between 3.773 and 4.6 GeV, are also shown. The cross sections for $\mathop e\nolimits^ + \mathop e\nolimits^ - \to \mathop {\mathop \Lambda \nolimits_c^ - }\limits^ - \mathop \Lambda \nolimits_c^ +$ and $\mathop e\nolimits^ + \mathop e\nolimits^ - \to \mathop \Lambda \limits^ - \Lambda$ are measured near threshold with unprecedented precision. Preliminary results on the first measurement of the ^c form factor ratio |GE|/|GM| are also given. Ongoing analysis based on the high luminosity energy scan from 2015 and from radiative return at different $\sqrt s$ are also described

Electromagnetic proton form factors: perspectives for PANDA

The PANDA collaboration studies fundamental aspects of the strong interaction in the transition region between non-perturbative and perturbative QCD, investigating charmonium spectroscopy, hybrids and glueballs, hypernuclei, light and heavy meson production with antiproton beams. In this contribution we focus on leptonic final channels which give access to nucleon electromagnetic form factors. The expected precision on the electric and magnetic form factors of the proton in the time-like region and the radiative corrections to be applied to the data are discussed

Time-like Proton Form Factors with Initial State Radiation Technique

Electromagnetic form factors are fundamental quantities describing the internal structure of hadrons. They can be measured with scattering processes in the space-like region and annihilation processes in the time-like region. The two regions are connected by crossing symmetry. The measurements of the proton electromagnetic form factors in the time-like region using the initial state radiation technique are reviewed. Recent experimental studies have shown that initial state radiation processes at high luminosity electron-positron colliders can be effectively used to probe the electromagnetic structure of hadrons. The BABAR experiment at the B-factory PEP-II in Stanford and the BESIII experiment at BEPCII (an electron positron collider in the τ-charm mass region) in Beijing have measured the time-like form factors of the proton using the initial state radiation process e+e−→pp¯γ. The two kinematical regions where the photon is emitted from the initial state at small and large polar angles have been investigated. In the first case, the photon is in the region not covered by the detector acceptance and is not detected. The Born cross section and the proton effective form factor have been measured over a wide and continuous range of the the momentum transfer squared q2 from the threshold up to 42 (GeV/c)2. The ratio of electric and magnetic form factors of the proton has been also determined. In this report, the theoretical aspect and the experimental studies of the initial state radiation process e+e−→pp¯γ are described. The measurements of the Born cross section and the proton form factors obtained in these analyses near the threshold region and in the relatively large q2 region are examined. The experimental results are compared to the predictions from theory and models. Their impact on our understanding of the nucleon structure is discussed

Baryon electromagnetic form factors at BESIII

Electromagnetic form factors are fundamental quantities which parameterize the electric and magnetic structure of hadrons. This contribution reports on the measurements of baryon electromagnetic form factors at the BESIII experiment in Beijing. The Beijing e+e− collider BEPCII is a double-ring symmetric collider running at √s between 2.0 and 4.6 GeV. Baryon electromagnetic form factors can be measured at BESIII in direct e+e−-annihilation and in initial state radiation processes. Based on the data collected by the BESIII detector at 12 center of mass energies between 2.23 and 3.67 GeV, the e+e− → p̄p cross section and the time-like proton form factor is measured. Preliminary results from the analysis of the initial state radiation process e+e− → p̄pγ using a data set of 7.408 fb−1 collected at center-of-mass energies between 3.773 and 4.6 GeV, are also presented. The cross section for e+e−→Λ¯Λ${e^ + }{e^ - } \to \bar \Lambda \Lambda$ is measured based on 40.5 pb−1 data collected at 4 energy points from the threshold up to 3.08 GeV. Preliminary results on the total cross section and the Λ effective form factor are shown. Ongoing analysis based on the high luminosity energy scan from 2015 and from radiative return at different √s are also described