We develop the theory of parton distributions f(_a)(π, k(^t2), μ(^2), unintegrated with respect to transverse momentum k(_t), from a phenomenological standpoint. In particular, we demonstrate a convenient approximation in which the unintegrated functions are obtained by explicitly performing the last step of parton evolution in perturbative QCD, with single-scale functions a(π, Q(^2) as input. Results are presented in the context of DGLAP and combined BFKL-DGLAP evolution, but with angular ordering imposed in the last step of the evolution. We illustrate the application of these unintegrated distributions to predict cross sections for physical processes at lepton-hadron and hadron-hadron colliders. The use of partons with incoming transverse momentum, based on k(_t)-factorisation, is intended to replace phenomenological "smearing" in the perturbative region k(_t) > k(_o) (k(_o) ≈ 1 GeV), and enables the full kinematics of a process to be included even at leading order. We apply our framework to deep inelastic scattering and the fitting of F(_2)(π, Q(^2), to the transverse momentum spectra of prompt photons in hadroproduction and in photoproduction, and to the topical problem of bb production at HERA. Finally, we address the issue of parton-parton recombination (shadowing) at very low values of π, building on recent work by Kovchegov and others to make predictions for the likely magnitude of shadowing effects at the LHC.

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We present the new framework based on BFKL and DGLAP evolution equations in which the leading in(Q(_2)) and in(l/x) terms are treated on equal footing. We introduce a pair of coupled integro-difFerential equations for the quark singlet and the unintegrated gluon distribution. The observable structure functions are calculated using high energy factorisation approach. We also include the sub-leading in (l/x) effects via consistency constraint. We argue that the use of this constraint leads to more stable solution to the Pomeron intercept than that based on the NLO calculation of the BFKL equation alone and generates resummation to all orders of the major part of the subleading in (l/x) effects. The global fit to all available deep inelastic data is performed using a simple parametrisation of the non-perturbative region. We also present the results for the longitudinal structure function and the charm component of the F(_2) structure function. Next; we extend this approach to the low Q(^2) domain. At small distances we use the perturbative approach based on the unified BFKL/DGLAP equations and for large distances we use Vector Meson Dominance Model and, for the higher mass qq states, the additive quark approach. We show the results for the total cross section and for the ratio of the longitudinal and transverse structure functions. Finally, we calculate the dijet production and consider the decorrelation effects in the azimuthal distributions caused by the diffusion in the transverse momentum k(_r) of the exchanged gluon. Using the gluon distribution which is fixed by the fit to the DIS data we are able to make absolute predictions. We show the results for the dF(_r)/dɸ, the total cross section and also the distributions in Q(^2) as well as in the longitudinal momentum fraction of the gluon. Our theoretical predictions are confronted with the measurements made using ZEUS detector at HERA.

In dieser Arbeit wird eine Messung des inklusiven tief-inelastischen Positron- Proton Wirkungsquerschnitts bei kleinen Impulsüberträgen Q2 vorgestellt. Die Messung wird zur Bestimmung der longitudinalen Protonstrukturfunktion FL benutzt. Es werden Daten analysiert, welche mit dem H1 Detektor in speziellen Perioden mit reduzierter Protonstrahlenergie im Jahre 2007 aufgezeichnet wurden. Die direkte Bestimmung der Strukturfunktion FL basiert auf der Messung des reduzierten tiefinelastischen Wirkungsquerschnitt bei drei verschiedenen Schwerpunktsenergien. Ein spezieller Rekonstruktionsalgorithmus für Elektronen wurde entwickelt, welcher die Informationen der zentralen Spurkammer CJC und des Siliziumdetektors BST kombiniert. Dieser wurde in die H1 Rekonstruktionssoftware H1REC integriert. Die Effizienz des Algorithmus wird untersucht. Die Arbeit präsentiert den Wirkungsquerschnitt und die FL Messung für Inelastizitäten im Bereich von 2.5 GeV2 < Q2 < 25 GeV2. / A measurement of the inclusive cross section for the deep-inelastic scattering of positrons on protons at low four-momentum transfer squared Q2 is presented. The measurement is used for the extraction of the longitudinal proton structure function FL. The analysis is based on data collected by the H1 experiment during special, low energy runs in the year 2007. The direct technique of the FL determination based on the extraction of the reduced DIS cross sections for three different centre-of-mass energies is used. For the purpose of the analysis a dedicated electron finder has been developed and integrated with the standard H1 reconstruction software H1REC. The algorithm employs information from two independent tracking detectors the Backward Silicon Tracker and the Central Jet Chamber. The performance of the finder is studied. The thesis presents the cross section and the FL measurements in the range of 2.5 GeV2 < Q2 < 25 GeV2.

The cross sections for neutral current (NC) deep inelastic scattering (DIS) in e+p collisions with a longitudinally polarised positron beam are measured at high momentum transfer squared (Q2 > 185 GeV2) at the ZEUS detector at HERA. The HERA accelerator provides e+-p collisions at a centre-of-mass energy of 318 GeV, which allows the weak contribution to the NC process to be studied at high Q2. The measurements are based on a data sample with an integrated luminosity of 135.5 pb-1 collected with the ZEUS detector in 2006 and 2007. The single differential NC cross sections dsigma/dQ2, dsigma/dx and dsigma/dy and the reduced cross section are measured. The structure function xF3 is determined by combining the e+p NC reduced cross sections with the previously measured e-p measurements. The interference structure function xF 3^gamma,Z is extracted at Q2 = 1500 GeV2. The cross-section asymmetry between the positive and negative polarisation of the positron beam is measured and the parity violation effects of the electroweak interaction are observed. The predictions of the Standard Model of particle physics agree well with the measurements.

No description available.

The cross sections for neutral current (NC) deep inelastic scattering (DIS) in e+p collisions with a longitudinally polarised positron beam are measured at high momentum transfer squared (Q2 > 185 GeV2) at the ZEUS detector at HERA. The HERA accelerator provides e+-p collisions at a centre-of-mass energy of 318 GeV, which allows the weak contribution to the NC process to be studied at high Q2. The measurements are based on a data sample with an integrated luminosity of 135.5 pb-1 collected with the ZEUS detector in 2006 and 2007. The single differential NC cross sections dsigma/dQ2, dsigma/dx and dsigma/dy and the reduced cross section are measured. The structure function xF3 is determined by combining the e+p NC reduced cross sections with the previously measured e-p measurements. The interference structure function xF 3^gamma,Z is extracted at Q2 = 1500 GeV2. The cross-section asymmetry between the positive and negative polarisation of the positron beam is measured and the parity violation effects of the electroweak interaction are observed. The predictions of the Standard Model of particle physics agree well with the measurements.

Les travaux effectués au cours de cette thèse au sein du groupe de structure nucléaire de l’IPN d’Orsay s’articulent autour de la production, en vue d’une étude par spectroscopie gamma, de noyaux exotiques riches en neutron de la couche fp. Dans ce cadre, nous avons mis en place, auprès de l’accélérateur Tandem d’Orsay, un multi-détecteur au germanium baptisé ORGAM, destiné à la spectroscopie gamma à haute résolution. Au cours de l’année 2008-2009, les détecteurs amenés à composer ORGAM ont été testés individuellement, ainsi que le dispositif annexe de réjection Compton, en coopération avec la division instrumentation du laboratoire. Parallèlement, le système d’alimentation automatique en azote liquide, destiné au maintien des détecteurs à basse température, a été amélioré et fiabilisé. L’ensemble du dispositif a été mis en place sur une ligne de faisceau de l’accélérateur tandem avec le concours du personnel technique de l’accélérateur.La première expérience utilisant le dispositif ORGAM a été réalisée en juillet 2009. Cette expérience, dont les données ont été analysées dans le cadre de ce travail, visait à étudier les collisions profondément inélastiques entre un faisceau de 36S accéléré à 154 MeV, et une cible de 70Zn. Un dispositif permettant la détection des particules chargées émises à grand angle a été utilisé afin d’identifier les fragments de ces collisions. Il n’a pas été possible, du fait du fond important induit par la diffusion élastique du faisceau dans la cible, d’identifier directement ces fragments. L’étude des coïncidences gamma-gamma avec le détecteur ORGAM a cependant permis de mettre en évidence de nombreuses cascades de photons désexcitant des noyaux potentiellement produits par les réactions d’intérêt.Les données recueillies au cours d’une autre expérience, réalisée auprès du tandem d’Orsay en 2005, ont été analysées dans le cadre de ce travail. Cette expérience, visant à produire par fusion évaporation entre un faisceau de 14C à 25 MeV et une cible de 48Ca, les noyaux de 59Mn et de 57Cr, a permis d’établir une partie du spectre en énergie d’excitation de ces noyaux, jusqu'à une énergie d’excitation supérieure à 3 MeV.Une étude théorique des noyaux de chrome impairs de la couche fp a été tentée à l’aide d’un modèle phénoménologique de couplage intermédiaire. Ce modèle a permis une description satisfaisante du 53Cr. Les prédictions du modèle, qui ne prend pas en compte l’interaction entre nucléons de valence, se sont avérées beaucoup moins satisfaisante pour les noyaux de 55Cr et 57Cr. / This PhD thesis was prepared within the nuclear structure group of IPN Orsay. The work presented aimed to produce neutron rich fp shell nuclei through heavy ion collisions at the tandem accelerator of IPN, and to study them using gamma spectroscopy. For this purpose, a germanium gamma array called ORGAM, and dedicated to high resolution gamma spectroscopy, was set up at the tandem accelerator. During the year 2008/2009, the individual germanium detectors were tested and repaired, as well as their ancillary anti-Compton shielding. At the same time, the liquid nitrogen auto-fill system was improved for better reliability. The array was finally set up on a beam line of the accelerator.The first experiment using the ORGAM array was performed in July 2009. This experiment aimed to study fully damped deep-inelastic collisions between a 36S beam accelerated to 154 MeV, and a 70Zn target. An additional charged particle detection system was used to detect interesting fragments emitted at backward angles. It was not possible to separate these fragments from the background induced by backscattered ions from the beam. Nevertheless, the study of gamma-gamma coincidences detected with the ORGAM array allowed to identify gamma cascades de-exciting nuclei potentially produced through the mechanism of interest. Data accumulated during another experiment performed at the tandem accelerator in 2005 were analyzed. Fusion-evaporation reaction between a 25 MeV, 14C beam focused on a 48Ca target produced the 57Cr and 59Mn nuclei, whose energy spectra were established up to 3 MeV.We attempted to study theoretically odd Chromium isotopes with a simple model based on the intermediate coupling scheme. This model, which doesn’t take into account correlation between valence nucleons, described in satisfactory way the semi-magic + 1 neutron, 53Cr, but failed to do so for mid-shell nuclei 55Cr and 57Cr.

We have measured the flavor dependence of multiplicities for $\\pi^+$ and $\\pi^-$ production in semi-inclusive deep-inelastic scattering (SIDIS) on proton and deuteron targets. We used a 10.6 GeV electron beam at Jefferson Lab, and 4 msr solid angle spectrometers (HMS for electrons, SHMS for pions), the lepton vertex spanned the kinematic range $0.3 < x < 0.6$, $2 < Q^2 < 5$ GeV$^2$, and $4 < W^2 < 11$ GeV$^2$. The pion fractional momentum range was $0.3 < z < 0.7$ and the small transverse momentum range was $0 < P_t < .25$ GeV. We used the multiplicities to form sum-and-difference ratios, testing the validity of factorization. We extracted two favored and two unfavored $W$ dependent fragmentation functions (FFs) from these multiplicities. Assuming factorization at low $P_t$, we find that the two ``favored" FFs allow for isospin breaking (charge symmetry violation) at low $W$, while converging to a common value at the highest $W$ of this experiment. The two unfavored FFs are consistent with each other within the experimental uncertainties.