Diffractive Phenomena and Shadowing in Deep-Inelastic Scattering

Shadowing effects in deep-inelastic lepton-nucleus scattering probe the mass spectrum of diffractive leptoproduction from individual nucleons. We explore this relationship using current experimental information on both processes. In recent data from the NMC and E665 collaboration, taken at small x << 0.1 and Q^2 < 1 GeV^2, shadowing is dominated by the diffractive excitation and coherent interaction of low mass vector mesons. If shadowing is explored at small x > 1 GeV^2 as discussed at HERA, the situation is different. Here dominant contributions come from the coherent interaction of diffractively produced heavy mass states. Furthermore we observe that the energy dependence of shadowing is directly related to the mass dependence of the diffractive production cross section for free nucleon targets.Comment: 12 pages Latex, 8 figure

Economic Implications of Additive Manufacturing and the Contribution of MIS

This is the author accepted manuscript. The final version is available from Springer at http://link.springer.com/article/10.1007%2Fs12599-015-0374-4

Resummation of nuclear enhanced higher twist in the Drell Yan process

We investigate higher twist contributions to the transverse momentum broadening of Drell Yan pairs in proton nucleus collisions. We revisit the contribution of matrix elements of twist-4 and generalize this to matrix elements of arbitrary twist. An estimate of the maximal nuclear broadening effect is derived. A model for nuclear enhanced matrix elements of arbitrary twist allows us to give the result of a resummation of all twists in closed form. Subleading corrections to the maximal broadening are discussed qualitatively.Comment: 10 pages, 5 figures; v2: minor changes in text, acknowledgement added; v3: mistake in fig. 1 correcte

Return of the EMC Effect: Finite Nuclei

A light front formalism for deep inelastic lepton scattering from finite nuclei is developed. In particular, the nucleon plus momentum distribution and a finite system analog of the Hugenholtz-van Hove theorem are presented. Using a relativistic mean field model, numerical results for the plus momentum distribution and ratio of bound to free nucleon structure functions for Oxygen, Calcium and Lead are given. We show that we can incorporate light front physics with excellent accuracy while using easily computed equal time wavefunctions. Assuming nucleon structure is not modified in-medium we find that the calculations are not consistent with the binding effect apparent in the data not only in the magnitude of the effect, but in the dependence on the number of nucleons.Comment: 11 pages, 6 figure

Peripheral heavy ion collisions as a probe of the nuclear gluon distribution

At high energies a quark-gluon plasma is expected to be formed in heavy ion collisions at RHIC and LHC. The theoretical description of these processes is directly associated to a complete knowledge of the details of medium effects in the nuclear gluon distribution. In this paper we analyze the possibility to constraint the behavior of this distribution considering peripheral heavy ion collisions. We reanalyze the photoproduction of heavy quarks for the deduction of the in-medium gluon distribution using three current parameterizations for this parton distribution. Moreover, we show that the elastic photoproduction of vector mesons is a potential process to probe the nuclear gluon distribution.Comment: 8 figures, accepted for publication in Physicsl review

Charmonium suppression from purely geometrical effects

The extend to which geometrical effects contribute to the production and suppression of the $J/\psi$ and $q\bar{q}$ minijet pairs in general is investigated for high energy heavy ion collisions at SPS, RHIC and LHC energies. For the energy range under investigation, the geometrical effects referred to are shadowing and anti-shadowing, respectively. Due to those effects, the parton distributions in nuclei deviate from the naive extrapolation from the free nucleon result; $f_{A}\neq A f_{N}$. The strength of the shadowing/anti-shadowing effect increases with the mass number. The consequences of gluonic shadowing effects for the $x_F$ distribution of $J/\psi$'s at $\sqrt s =20$ GeV, $\sqrt s =200$ GeV and $\sqrt s =6$ TeV are calculated for some relevant combinations of nuclei, as well as the $p_T$ distribution of minijets at midrapidity for $N_f=4$ in the final state.Comment: corrected some typos, improved shadowing ratio

Investigation of slowing down and charge-exchange of nickel and uranium ions in gases and solids in the energy range (60 - 200) MeV/u

In this thesis new slowing down and charge-state measurements will be presented in the energy range of (60 - 200) MeV/u. These measurements were done using the Fragment Separator (FRS) facility at GSI in Darmstadt. The presented data were taken during two experimental runs. The experiments were divided into two parts. In the first part a 200 MeV/u Ni27+ beam was used. The evolution of charge states as a function of the target thickness was investigated covering both the non-equilibrium and equilibrium region. This was done with various mono-atomic materials (Z2 = 6, 7, 10, 13, 18, 22) and compound materials (ethylene, polyethylene and polypropylene). From the measured charge-state distributions the one-electron ionization and capture cross sections have been extracted. A 40 % gas-solid difference is observed in the ionization cross sections for the mono-atomic materials. In the compound materials a 30 % difference is observed between ethylene and the polymers. The experimental cross sections for the mono-atomic materials have been compared with theoretical calculations [1, 2]. The theoretical ionization cross sections agree quite well with the corresponding experimental ionization cross sections. In the gaseous targets the agreement between experiment and theory is better than 3 %. For the capture cross sections the agreement between experiment and theory is also very good for the lighter target materials (Z2 <= 7). For the heavier targets large deviations up to one order of magnitude are observed. These deviations are due to the increasing importance of the non-radiative capture channel in heavier target materials which is quite difficult to calculate accurately. The results motivate for further refinement of the theory in this energy region. In the second part 3 different uranium beams were used with initial energies of 61 MeV/u (U86+ incident), 85 MeV/u (U73+ incoming) and 200 MeV/u (U81+ incident) to measure the evolution of the charge states again and the energy loss as a function of the target thickness in the same materials as used in the first part plus some additional mono-atomic materials Z2 = 29, 36, 47, 54. From the measured charge-state distributions and energy losses the mean charges and stopping forces have been extracted. At 61 MeV/u we observe a gas-solid difference in the mean charge of up to 4 charge states for the mono-atomic materials. The corresponding stopping powers (forces) at the same specific energy only show a gas-solid difference for light materials (Z2 <= 7). The stopping forces are compared with calculations done with the PASS code [3, 4], ATIMA code [5] and the Hubert et al. tables [6]. The agreement is quite good between experiment and theory. The PASS code predicts by using the experimental mean charges a gas-solid difference in the stopping force for the heavier target materials. In the data at 200 MeV/u there is a gas-solid difference in the ionization rate for U81+ ions similar to the Ni27+ results.In dieser Dissertation werden neue Ladungsverteilungen und Energieverlustmessungen präsentiert. Diese Messungen wurden am Fragment Separator (FRS) bei der GSI in Darmstadt durchgeführt. Die Daten, die hier vorgestellt werden, wurden in zwei Experimenten aufgenommen. Die Experimente bestanden aus zwei Teilen. Im ersten Teil wurde mit einem 200 MeV/u Ni27+ Strahl gemessen. Ziel dieser Messung war die Entwicklung der Ladungsverteilung als Funktion der Targetdicke vom Nichtgleichgewicht bis Gleichgewicht zu untersuchen. Dies wurde mit verschiedenen Targets gemacht (Z2 = 6, 7, 10, 13, 18, 22, Äthylen, Polyäthylen und Polypropylen). Von den gemessenen Ladungsverteilung konnten die Umladungsquerrschnitte für Elektroneneinfang und -verlust extrahiert werden. Ein Gas-Festkörper Effekt von 40 % wurde im Ionizationsquerrschnitt für die monoatomaren (reinen Elemente) Targets gemessen. Im Äthylen und den Polymeren (Polyäthylen und Polypropylen) war ein Effekt von 30 % zu sehen. Die experimentellen Umladungsquerrschnitte für die monoatomaren Targets wurden mit theoretischen Rechnungen von A. Surzhykov und S. Fritzsche [1] und V. P. Shevelko [2] verglichen. In der Ionization stimmen die theoretischen Rechnungen mit den experimentellen Werten gut überein. In den Gastargets ist die Übereinstimmung besser als 3 %. Im Elektroneneinfang gibt es gute Übereinstimmung zwischen Experiment und Theorie bei den leichten Targets (Z2 <= 7), bei den schweren Targets gibt es grosse Abweichungen bis zu einer Grössenordnung. Diese Abweichung kommt zustande, weil der nicht-radiative Querrschnitt einen grösseren Anteil hat bei den schweren Targets und dieser Teil sehr schwer theoretisch zu rechnen ist. Die Ergebnisse sind eine Motivation für Verbesserungen in der Theorie im diesen Energiebereich. Im zweiten Teil wurde ein Uranstrahl bei drei verschiedenen Energien benutzt, diese waren 61 MeV/u mit 86+ als Eingangsladungszustand, 85 MeV/u mit 73+ als Eingangsladungszustand und 200 MeV/u mit 81+ als Eingangsladungszustand. Ziel dieser Messung war es wiederum, die Entwicklung der Ladungsverteilung zu untersuchen und auch Energieverluste zu messen. Dieselben Targets wurden benutzt und zusätzlich wurden folgende Targets vermessen Z2 = 29, 36, 47, 54. Von den gemessenen Ladungsverteilungen und Energieverlusten wurde die mittlere Ladung und das Bremsvermögen bestimmt. Bei 61 MeV/u ist ein Gas-Festkörper Effekt in der mittleren Ladung bei den monoatomaren Targets zu sehen. Der Effekt hat eine Grösse von fast 4 Ladungen. Das dazu gehörige Bremsvermögen zeigt nur einen Gas-Festkörper Effekt bei den leichteren Targets (Z2 <= 7). Die experimentellen Werte wurden mit dem PASS Programm [3, 4], dem ATIMA Programm [5] und den Hubert et al. Tabellen [6] verglichen. Die theoretischen Rechnungen von den Programmen stimmen mit den experimentellen Werten gut überein. PASS sagt einen Gas-Festkörper Effekt bei den schwereren Targets voraus, weil experimentelle Ladungen als Eingangsparameter benutzt wurden. Bei der 200 MeV/u Messung wurde ein Gas-Festkörper Unterschied in der Ionizationsrate in der Entwicklung des U81+ Ladungszustand beobachtet, ähnlich wie in der Ni27+ Messung

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 $\rho$-meson mass in nuclei is suggested for a better explanation of the experimental data.Comment: 8 pages, 7 figure

Nuclear Shadowing in a Parton Recombination Model

Deep inelastic structure functions $F_2^A(x)$ are investigated in a $Q^2$ rescaling model with parton recombination effects. We find that the model can explain experimentally measured $F_2^A(x)$ structure functions reasonably well in the wide Bjorken$-x$ range ($0.005<x<0.8$). In the very small $x$ region ($x<0.02$), recombination results are very sensitive to input sea-quark and gluon distributions.Comment: preprint MKPH-T-93-04, IU/NTC 92-20, 25 pages, TEX file (without Figs. 1-14)., (address after April 1: Saga U., Japan

Photoproduction off Nuclei and Point-like Photon Interactions Part I: Cross Sections and Nuclear Shadowing

High energy photoproduction off nuclear targets is studied within the Glauber-Gribov approximation. The photon is assumed to interact as a $q\bar{q}$-system according to the Generalized Vector Dominance Model and as a ``bare photon'' in direct scattering processes with target nucleons. We calculate total cross sections for interactions of photons with nuclei taking into account coherence length effects and point-like interactions of the photon. Results are compared to data on photon-nucleus cross sections, nuclear shadowing, and quasi- elastic $\rho$-production. Extrapolations of cross sections and of the shadowing behaviour to high energies are given.Comment: 15 pages, 12 figure