Photon and dilepton production in heavy ion collisions at LHC

We review various production mechanisms of photons and small mass dileptons at large transverse momentum in heavy ion collisions at the LHC. Their relevance as a signal for quark-gluon plasma formation is discussed.Comment: 7 page

Matter in extremis: ultrarelativistic nuclear collisions at RHIC

We review the physics of nuclear matter at high energy density and the experimental search for the Quark-Gluon Plasma at the Relativistic Heavy Ion Collider (RHIC). The data obtained in the first three years of the RHIC physics program provide several lines of evidence that a novel state of matter has been created in the most violent, head-on collisions of $Au$ nuclei at $\sqrt{s}=200$ GeV. Jet quenching and global measurements show that the initial energy density of the strongly interacting medium generated in the collision is about two orders of magnitude larger than that of cold nuclear matter, well above the critical density for the deconfinement phase transition predicted by lattice QCD. The observed collective flow patterns imply that the system thermalizes early in its evolution, with the dynamics of its expansion consistent with ideal hydrodynamic flow based on a Quark-Gluon Plasma equation of state.Comment: 93 pages, 46 figures; final version for journal incorporating minor changes and correction

High-spin triaxial strongly deformed structures and quasiparticle alignments in 168Hf

This dissertation research consists of two parts: (i) investigation of quasiparticle alignments at high-spins and (ii) identification of triaxial strongly deformed structures in 168Hf. A γ-ray spectroscopy study was carried out, as well as lifetime measurements using the Doppler-shift Attenuation Method (DSAM). The two data sets used for this research were obtained from experiments at Argonne National Laboratory employing the reaction 96Zr(76Ge, 4n). The decay γ-rays were measured with the Gammasphere Compton-suppressed Ge spectrometer array. A self-supporting 96Zr foil ( thin target ) was used in the first experiment, while in the second experiment the 96Zr target material was evaporated onto a thick Au backing ( backed target or thick target ) to stop the recoiling nuclei for lifetime measurements. All previously known rotational bands have been extended to higher spins. Seven new normal-deformed bands, of which three are high-K bands, have been discovered. Neutron alignments were observed in all bands, and the proton alignments observed in several bands at the highest spin region (rotational frequency 0.55 - 0.6 MeV). The results are interpreted within the framework of the cranked shell model (CSM). Intrinsic configurations for the new bands, up to six quasiparticles, are proposed. The co-existing coupling schemes, deformation and rotation alignment, involving identical orbitals at high spin are discussed for the high-K bands. Possible decay pathways associated with three previously proposed candidates for triaxial strongly deformed (TSD) structures in 168Hf have been investigated. The spin and excitation energy of the bandhead for the strongest band, TSD1, were determined approximately based on γ-ray coincidence relationships. Discrete links were established for the second band. The overall agreement between the observed properties of the bands and cranking calculations using the Ultimate Cranker code provides strong support for an interpretation where band TSD1 is associated with a TSD minimum, (ε2, γ) ~ (0.43, 20°), involving the π(i13/2)2 and the ν(j15/2) high-j orbitals. This constitutes the first identification of a TSD band in Hf isotopes, long-predicted by theoretical studies. The second band is understood as being associated with a near-prolate shape and a deformation enhanced with respect to the normal deformed bands. It is proposed to be built on the π(i13/2 h9/2)ν(i13/2)2 configuration. The Doppler-shift attenuation method was used to measure lifetimes of yrast states. The deformation extracted from this measurement fits well with predictions from theoretical calculations

Standard Model tests with trapped radioactive atoms

We review the use of laser cooling and trapping for Standard Model tests, focusing on trapping of radioactive isotopes. Experiments with neutral atoms trapped with modern laser cooling techniques are testing several basic predictions of electroweak unification. For nuclear $\beta$ decay, demonstrated trap techniques include neutrino momentum measurements from beta-recoil coincidences, along with methods to produce highly polarized samples. These techniques have set the best general constraints on non-Standard Model scalar interactions in the first generation of particles. They also have the promise to test whether parity symmetry is maximally violated, to search for tensor interactions, and to search for new sources of time reversal violation. There are also possibilites for exotic particle searches. Measurements of the strength of the weak neutral current can be assisted by precision atomic experiments using traps of small numbers of radioactive atoms, and sensitivity to possible time-reversal violating electric dipole moments can be improved.Comment: 45 pages, 17 figures, v3 includes clarifying referee comments, especially in beta decay section, and updated figure

Nuclear structure and reaction studies at SPIRAL

The SPIRAL facility at GANIL, operational since 2001, is described briefly. The diverse physics program using the re-accelerated (1.2 to 25 MeV/u) beams ranging from He to Kr and the instrumentation specially developed for their exploitation are presented. Results of these studies, using both direct and compound processes, addressing various questions related to the existence of exotic states of nuclear matter, evolution of new "magic numbers", tunnelling of exotic nuclei, neutron correlations, exotic pathways in astrophysical sites and characterization of the continuum are discussed. The future prospects for the facility and the path towards SPIRAL2, a next generation ISOL facility, are also briefly presented.Comment: 48 pages, 27 figures. Accepted for publication in Journal of Physics

High-spin triaxial strongly deformed structures and quasiparticle alignments in 168Hf

This dissertation research consists of two parts: (i) investigation of quasiparticle alignments at high-spins and (ii) identification of triaxial strongly deformed structures in 168Hf. A γ-ray spectroscopy study was carried out, as well as lifetime measurements using the Doppler-shift Attenuation Method (DSAM). The two data sets used for this research were obtained from experiments at Argonne National Laboratory employing the reaction 96Zr(76Ge, 4n). The decay γ-rays were measured with the Gammasphere Compton-suppressed Ge spectrometer array. A self-supporting 96Zr foil ( thin target ) was used in the first experiment, while in the second experiment the 96Zr target material was evaporated onto a thick Au backing ( backed target or thick target ) to stop the recoiling nuclei for lifetime measurements. All previously known rotational bands have been extended to higher spins. Seven new normal-deformed bands, of which three are high-K bands, have been discovered. Neutron alignments were observed in all bands, and the proton alignments observed in several bands at the highest spin region (rotational frequency 0.55 - 0.6 MeV). The results are interpreted within the framework of the cranked shell model (CSM). Intrinsic configurations for the new bands, up to six quasiparticles, are proposed. The co-existing coupling schemes, deformation and rotation alignment, involving identical orbitals at high spin are discussed for the high-K bands. Possible decay pathways associated with three previously proposed candidates for triaxial strongly deformed (TSD) structures in 168Hf have been investigated. The spin and excitation energy of the bandhead for the strongest band, TSD1, were determined approximately based on γ-ray coincidence relationships. Discrete links were established for the second band. The overall agreement between the observed properties of the bands and cranking calculations using the Ultimate Cranker code provides strong support for an interpretation where band TSD1 is associated with a TSD minimum, (ε2, γ) ~ (0.43, 20°), involving the π(i13/2)2 and the ν(j15/2) high-j orbitals. This constitutes the first identification of a TSD band in Hf isotopes, long-predicted by theoretical studies. The second band is understood as being associated with a near-prolate shape and a deformation enhanced with respect to the normal deformed bands. It is proposed to be built on the π(i13/2 h9/2)ν(i13/2)2 configuration. The Doppler-shift attenuation method was used to measure lifetimes of yrast states. The deformation extracted from this measurement fits well with predictions from theoretical calculations