The interplay of multiplicity and effective energy for (multi) strange hadron production in pp collisions at the LHC

The enhanced production of strange hadrons in heavy-ion collisions relative to that in minimum-bias pp collisions is historically considered one of the first signatures of the formation of a deconfined quark-gluon plasma. At the LHC, the ALICE experiment observed that the ratio of strange to non-strange hadron yields increases with the charged-particle multiplicity at midrapidity, starting from pp collisions and evolving smoothly across interaction systems and energies, ultimately reaching Pb-Pb collisions. The understanding of the origin of this effect in small systems remains an open question. This thesis presents a comprehensive study of the production of $K^{0}_{S}$, $\Lambda$ ($\bar{\Lambda}$) and $\Xi^{-}$ ($\bar{\Xi}^{+}$) strange hadrons in pp collisions at $\sqrt{s}$ = 13 TeV collected in LHC Run 2 with ALICE. A novel approach is exploited, introducing, for the first time, the concept of effective energy in the study of strangeness production in hadronic collisions at the LHC. In this work, the ALICE Zero Degree Calorimeters are used to measure the energy carried by forward emitted baryons in pp collisions, which reduces the effective energy available for particle production with respect to the nominal centre-of-mass energy. The results presented in this thesis provide new insights into the interplay, for strangeness production, between the initial stages of the collision and the produced final hadronic state. Finally, the first Run 3 results on the production of $\Omega^{\pm}$ ($\bar{\Omega}^{+}$) multi-strange baryons are presented, measured in pp collisions at $\sqrt{s}$ = 13.6 TeV and 900 GeV, the highest and lowest collision energies reached so far at the LHC. This thesis also presents the development and validation of the ALICE Time-Of-Flight (TOF) data quality monitoring system for LHC Run 3. This work was fundamental to assess the performance of the TOF detector during the commissioning phase, in the Long Shutdown 2, and during the data taking period.

{2p_\pi}-{2p_\sigma} crossing in heavy symmetric ion-atom collisions: I. Level structure

Ab initio self-consistent DFS calculations are performed for five different symmetric atomic systems from Ar-Ar to Pb-Pb. The level structure for the {2p_\pi}-{2p_\sigma} crossing as function of the united atomic charge Z_u is studied and interpreted. Manybody effects, spin-orbit splitting, direct relativistic effects as well as indirect relativistic effects are differently important for different Z_u. For the I-I system a comparison with other calculations is given.

Evidence for an additional coupling of the innermost shells in very heavy quasi-molecular ion-atom collisions

Due to the tremendous spin-orbit splitting of quasi-molecular levels in superheavy collision systems (Z = Z_1 + Z_2 {\ge\approx} 137) bombarding energy 0.5-6 MeV N{^-1}, unusual couplings may occur around Z \simeq 165. Experimental evidence for such a theoretically predicted coupling is discussed.

Lability of heavy metal species in aquatic humic substances characterized by ion exchange with cellulose phosphate

Labile metal species in aquatic humic substances (HSs) were characterized by ion exchange on cellulose phosphate (CellPhos) by applying an optimized batch procedure. The HSs investigated were pre-extracted from humic-rich waters by ultrafiltration and a resin XAD 8 procedure. The HS-metal species studied were formed by complexation with Cd(II), Ni(II), Cu(II), Mn(II) and Pb(II) as a function of time and the ratio ions to HSs. The kinetics and reaction order of this exchange process were studied. At the beginning (<3 min), the labile metal fractions are separated relatively quickly. After 3 min, the separation of the metal ions proceeds with uniform half-lives of about 12-14 min, revealing rather slow first-order kinetics. The metal exchange between HSs and CellPhos exhibited the following order of metal lability with the studied HSs: Cu > Pb > Mn > Ni > Cd. The required metal determinations were carried out by atomic absorption spectrometry.

Adsorption of dihydrogen phosphate ion on platinum electrodes in aqueous media monitored by probe-beam deflection

Probe-beam deflection (PBD) was used to monitor concentration gradients of anions adjacent to the surface of a platinum electrode in acidic aqueous media containing H3PO4. PBD can measure the potential-dependent extent of adsorption of H2PO4- on the Pt electrode surface and permits the Langmuir isotherm to be fitted to the experimental data. The value thus obtained for the surface concentration was 1.3 × 10-11 mol mm -2, or 1.7 atoms of Pt per H2PO4-. Also, the electron transfer number obtained was 0.24, signifying an incomplete transfer of charge, and the equilibrium constant is 1.80 suggesting a reversible adsorption process. © 2005 Elsevier B.V. All rights reserved.

Desorption of heavy metals from ion exchange resin with water and carbon dioxide

Adsorption and regeneration of ion exchange resins were studied using a subcritical solution of a CO₂-H₂O mixture and a fixed bed column. The commercial Amberlite IRC-50/IRC-86 cation exchange resins and Amberlite IRA-67 anion exchange resin were tested for heavy metals (Pb, Cu, Cd) adsorption from a solution with different initial metal concentrations at different temperatures. After adsorption, the loaded resins were regenerated with water and carbon dioxide at different temperatures and a pressure of 25 MPa. The efficiency of the IRC-50 resin was lower than that of the IRC-86 resin for the adsorption of metals like Cd, Cu and Pb. Results obtained for desorption of these metals indicated that the process could be used for Cd and in principle for Cu. Sorption of metal ions depended strongly on feed concentration. Mathematical modeling of the metal desorption process was carried out successfully as an extraction process. For this purpose, the VTII Model, which is applied to extraction from solids using supercritical solvents, was used in this work.

Preparation of cold Mg + ion clouds for sympathetic cooling of highly charged ions at SPECTRAP

Die Elektronen in wasserstoff- und lithium-ähnlichen schweren Ionen sind den extrem starken elektrischen und magnetischen Feldern in der Umgebung des Kerns ausgesetzt. Die Laserspektroskopie der Hyperfeinaufspaltung im Grundzustand des Ions erlaubt daher einen sensitiven Test der Quantenelektrodynamik in starken Feldern insbesondere im magnetischen Sektor. Frühere Messungen an wasserstoffähnlichen Systemen die an einer Elektronenstrahl-Ionenfalle (EBIT) und am Experimentierspeicherring (ESR) der GSI Darmstadt durchgeführt wurden, waren in ihrer Genauigkeit durch zu geringe Statistik, einer starken Dopplerverbreiterung und der großen Unsicherheit in der Ionenenergie limitiert. Das ganze Potential des QED-Tests kann nur dann ausgeschöpft werden, wenn es gelingt sowohl wasserstoff- als auch lithium-ähnliche schwere Ionen mit einer um 2-3 Größenordnung gesteigerten Genauigkeit zu spektroskopieren. Um dies zu erreichen, wird gegenwärtig das neue Penningfallensystem SPECTRAP an der GSI aufgebaut und in Betrieb genommen. Es ist speziell für die Laserspektroskopie an gespeicherten hochgeladenen Ionen optimiert und wird in Zukunft von HITRAP mit nierderenergetischen hochgeladenen Ionen versorgt werden.rnrnSPECTRAP ist eine zylindrische Penningfalle mit axialem Zugang für die Injektion von Ionen und die Einkopplung eines Laserstrahls sowie einem radialen optischen Zugang für die Detektion der Fluoreszenz. Um letzteres zu realisieren ist der supraleitende Magnet als Helmholtz-Spulenpaar ausgelegt. Um die gewünschte Genauigkeit bei der Laserspektroskopie zu erreichen, muss ein effizienter und schneller Kühlprozess für die injizierten hochegeladenen Ionen realisiert werden. Dies kann mittels sympathetischer Kühlung in einer lasergekühlten Wolke leichter Ionen realisiert werden. Im Rahmen dieser Arbeit wurde ein Lasersystem und eine Ionenquelle für die Produktion einer solchen 24Mg+ Ionenwolke aufgebaut und erfolgreich an SPECTRAP in Betrieb genommen. Dazu wurde ein Festkörperlasersystem für die Erzeugung von Licht bei 279.6 nm entworfen und aufgebaut. Es besteht aus einem Faserlaser bei 1118 nm der in zwei aufeinanderfolgenden Frequenzverdopplungsstufen frequenzvervierfacht wird. Die Verdopplerstufen sind als aktiv stabilisierte Resonantoren mit nichtlinearen Kristallen ausgelegt. Das Lasersystem liefert unter optimalen Bedingeungen bis zu 15 mW bei der ultravioletten Wellenlänge und erwies sich während der Teststrahlzeiten an SPECTRAP als ausgesprochen zuverlässig. Desweiteren wurde eine Ionequelle für die gepulste Injektion von Mg+ Ionen in die SPECTRAP Falle entwickelt. Diese basiert auf der Elektronenstoßionisation eines thermischen Mg-Atomstrahls und liefert in der gepulsten Extraktion Ionenbündel mit einer kleinen Impuls- und Energieverteilung. Unter Nutzung des Lasersystems konnten damit an SPECTRAP erstmals Ionenwolken mit bis zu 2600 lasergekühlten Mg Ionen erzeugt werden. Der Nachweis erfolgte sowohl mittels Fluoreszenz als auch mit der FFT-ICR Technik. Aus der Analyse des Fluoreszenz-Linienprofils lässt sich sowohl die Sensitivität auf einzelne gespeicherte Ionen als auch eine erreichte Endtemperatur in der Größenordnung von ≈ 100 mK nach wenigen Sekunden Kühlzeit belegen.

Electronic damage in quartz (c-SiO2) by MeV ion irradiations: Potentiality for optical waveguiding applications

The damage induced on quartz (c-SiO2) by heavy ions (F, O, Br) at MeV energies, where electronic stopping is dominant, has been investigated by RBS/C and optical methods. The two techniques indicate the formation of amorphous layers with an isotropic refractive index (n = 1.475) at fluences around 1014 cm−2 that are associated to electronic mechanisms. The kinetics of the process can be described as the superposition of linear (possibly initial Poisson curve) and sigmoidal (Avrami-type) contributions. The coexistence of the two kinetic regimes may be associated to the differential roles of the amorphous track cores and preamorphous halos. By using ions and energies whose maximum stopping power lies inside the crystal (O at 13 MeV, F at 15 MeV and F at 30 MeV) buried amorphous layer are formed and optical waveguides at the sample surface have been generated.

Ionoluminescence induced by swift heavy ions in silica and quartz: a comparative analysis

Ionoluminescence (IL) of the two SiO2 phases, amorphous silica and crystalline quartz, has been comparatively investigated in this work, in order to learn about the structural defects generated by means of ion irradiation and the role of crystalline order on the damage processes. Irradiations have been performed with Cl at 10 MeV and Br at 15 MeV, corresponding to the electronic stopping regime (i.e., where the electronic stopping power Se is dominant) and well above the amorphization threshold. The light-emission kinetics for the two main emission bands, located at 1.9 eV (652 nm) and 2.7 eV (459 nm), has been measured under the same ion irradiation conditions as a function of fluence for both, silica and quartz. The role of electronic stopping power has been also investigated and discussed within current views for electronic damage. Our experiments provide a rich phenomenological background that should help to elucidate the mechanisms responsible for light emission and defect creation.

W-beam guiderail transition from light to heavy posts. Final report.

Federal Highway Administration, Office of Research, Development, and Technology, Washington, D.C.

A comparative study of alginate beads and an ion-exchange resin for the removal of heavy metals from a metal plating effluent

The capacity of dry protonated calcium alginate beads to sorb metals from an industrial effluent was studied and compared with a commercial ion-exchange resin (Lewatit TP 207). Both sorbents decreased zinc, nickel, iron and calcium concentrations in the effluent, and released sodium during treatment. Alginate beads removed lower amounts of heavy metals than the resin, but exhibited faster uptake kinetics. Zinc desorption from the sorbents was achieved in 30 minutes using 0.1 M HCl or 0.1 M H(2)SO(4). Desorption ratios with these acids varied between 90 and 100% for alginate, and 98 to 100% for the ion-exchange resin. Reusability tests with HCl showed that alginate beads can stand acid desorption and recover binding capacity. Overall, the comparison of dry protonated alginate beads with the resin supports the potential of the biosorbent for the treatment of industrial effluents.

Conducting polymer formed by low energy gold ion implantation

A buried conducting layer of metal/polymer nanocomposite was formed by very low energy gold ion implantation into polymethylmethacrylate. The conducting layer is similar to 3 nm deep and of width similar to 1 nm. In situ resistivity measurements were performed as the implantation proceeded, and the conductivity thus obtained as a function of buried gold concentration. The measured conductivity obeys the behavior well established for composites in the percolation regime. The critical concentration, below which the polymer remains an insulator, is attained at a dose similar to 1.0 x 10(16) atoms/cm(2) of implanted gold ions. (C) 2008 American Institute of Physics.

Heavy quark production in deep inelastic electron-nucleus scattering

Heavy quark production has been very well studied over the last years both theoretically and experimentally. Theory has been used to study heavy quark production in ep collisions at HERA, in pp collisions at Tevatron and RHIC, in pA and dA collisions at RHIC, and in AA collisions at CERN-SPS and RHIC. However, to the best of our knowledge, heavy quark production in eA has received almost no attention. With the possible construction of a high energy electron-ion collider, updated estimates of heavy quark production are needed. We address the subject from the perspective of saturation physics and compute the heavy quark production cross section with the dipole model. We isolate shadowing and nonlinear effects, showing their impact on the charm structure function and on the transverse momentum spectrum.