119682609
Coulomb shifts and shape changes in the mass 70 region
The technique of recoil {beta} tagging has been developed which allows prompt {gamma} decays in nuclei from excited states to be correlated with electrons from their subsequent short-lived {beta} decay. This technique is ideal for studying nuclei very far from stability and improves in sensitivity for very short-lived decays and for high decay Q-values. The method has allowed excited states in {sup 78}Y to be observed for the first time, as well as an extension in the knowledge of T=1 states in {sup 74}Rb. From this new information it has been possible to compare Coulomb energy differences (CED) between T=1 states in {sup 70}Br/{sup 70}Se, {sup 74}Rb/{sup 74}Kr, and {sup 78}Y/{sup 78}Sr. The A=70 CED exhibit an anomalous behavior which is inconsistent with all other known CED. This behavior may be accounted for qualitatively in terms of small variations in the Coulomb energy arising from shape changes.
121158687
High-K four-quasiparticle states in Gd-138
States above the known K(pi) = 8(-) 6 mu s isomer in (138)Gd have been populated with the (106)Cd((36)Ar,2p2n) reaction at a beam energy of 180 MeV at the University of Jyvaskyla, Finland. The recoil-isomer tagging technique was utilized to correlate delayed gamma-ray decays, detected in the GREAT focal plane spectrometer, with prompt decays measured in the JUROGAM II spectrometer at the target position. The lifetime of the K(pi) = 8(-) isomeric state has been remeasured as 6.2(2) mu s. Two high-lying strongly coupled bands have been established with K(pi) >= 12(-). Potential-energy surface calculations, in conjunction with g factor measurements, reveal that they are built upon four-quasiparticle structures comprising two-quasineutron plus two-quasiproton configurations. The short half-life or lack of hindrance for the decays from these four-quasiparticle band-head states is reasoned to be a consequence of increased triaxial deformation and mixing due to the high density of states relative to the lower two-quasiparticle 6-mu s isomeric state.
1861803
Gamma-ray spectroscopy at the limits: first observation of rotational bands in 255Lr.
The rotational band structure of 255Lr has been investigated using advanced in-beam gamma-ray spectroscopic techniques. To date, 255Lr is the heaviest nucleus to be studied in this manner. One rotational band has been unambiguously observed and strong evidence for a second rotational structure was found. The structures are tentatively assigned to be based on the 1/2-[521] and 7/2-[514] Nilsson states, consistent with assignments from recently obtained alpha decay data. The experimental rotational band dynamic moment of inertia is used to test self-consistent mean-field calculations using the Skyrme SLy4 interaction and a density-dependent pairing force.
117103201
alpha decay of Re159 and proton emission from Ta155
115613705
Identification of the Kpi=8- rotational band in 138Gd
120743809
Spectroscopy of Ho-144 using recoil-isomer tagging
Excited states in the proton-unbound odd-odd nucleus {sup 144}Ho have been populated using the {sup 92}Mo({sup 54}Fe,pn){sup 144}Ho reaction and studied using the recoil-isomer-tagging technique. The alignment properties and signature splitting of the rotational band above the I{sup p}i=(8{sup +}){sup 144m}Ho isomer have been analyzed and the isomer confirmed to have a pih{sub 11/2} x nuh{sub 11/2} two-quasiparticle configuration. The configuration-constrained blocking method has been used to calculate the shapes of the ground and isomeric states, which are both predicted to have triaxial nuclear shapes with |gamma|approx =24 deg.
119768694
An update from STAR—using strangeness to probe relativistic heavy ion collisions
An overview of the strangeness measurements made by the STAR collaboration at RHIC for Au-Au collisions at √s NN = 130 and 200 GeV plus p-p collisions at √s NN = 200 GeV is presented. A wealth of information has been generated on the kinematics and scale of strange particle production by this experiment. When viewed in combination a picture emerges of particles demonstrating a surprisingly high degree of collective motion, suggestive of strong internal pressure within the source which builds up rapidly. The non-resonance yields are consistent with statistical hadron formation. Although there appears to be a rapid decoupling of the source, resonance particle measurements show signs of rescattering during the hadronic phase. Meanwhile the observed suppression of high momentum probes and their large azimuthal asymmetry indicate that this hot dense matter has significant interactions with particles moving through it.
55999663
An Experimental Exploration of the QCD Phase Diagram: The Search for the Critical Point and the Onset of De-confinement
The QCD phase diagram lies at the heart of what the RHIC Physics Program is
all about. While RHIC has been operating very successfully at or close to its
maximum energy for almost a decade, it has become clear that this collider can
also be operated at lower energies down to 5 GeV without extensive upgrades. An
exploration of the full region of beam energies available at the RHIC facility
is imperative. The STAR detector, due to its large uniform acceptance and
excellent particle identification capabilities, is uniquely positioned to carry
out this program in depth and detail. The first exploratory beam energy scan
(BES) run at RHIC took place in 2010 (Run 10), since several STAR upgrades,
most importantly a full barrel Time of Flight detector, are now completed which
add new capabilities important for the interesting physics at BES energies. In
this document we discuss current proposed measurements, with estimations of the
accuracy of the measurements given an assumed event count at each beam energy.
56166630
Centrality Dependence of Charged Particle Production at Large Transverse Momentum in Pb--Pb Collisions at $\sqrt{s_{\rm{NN}}} = 2.76$ TeV
The inclusive transverse momentum ($p_{\rm T}$) distributions of primary charged particles are measured in the pseudo-rapidity range $|\eta|<0.8$ as a function of event centrality in Pb--Pb collisions at $\sqrt{s_{\rm{NN}}}=2.76$ TeV with ALICE at the LHC. The data are presented in the $p_{\rm T}$ range $0.1530$ GeV/$c$. In peripheral collisions (70--80%), the suppression is weaker with $R_{\rm{AA}} \approx 0.7$ almost independently of $p_{\rm T}$. The measured nuclear modification factors are compared to other measurements and model calculations.
123359096
Charge Independent(CI) and Charge Dependent(CD) correlations as a function of Centrality formed from Delta phi imum Delta eta Charged Pair Correlations in Minimum Bias Au+Au Collisions at s(NN)**(1/2) = 200-GeV
28395001
Transverse-momentum and collision-energy dependence of high-pT hadron suppression in Au+Au collisions at ultrarelativistic energies.
We report high statistics measurements of inclusive charged hadron production in Au+Au and p+p collisions at sqrt[s(NN)]=200 GeV. A large, approximately constant hadron suppression is observed in central Au+Au collisions for 5<p(T)<12 GeV/c. The collision energy dependence of the yields and the centrality and p(T) dependence of the suppression provide stringent constraints on theoretical models of suppression. Models incorporating initial-state gluon saturation or partonic energy loss in dense matter are largely consistent with observations. We observe no evidence of p(T)-dependent suppression, which may be expected from models incorporating jet attenuation in cold nuclear matter or scattering of fragmentation hadrons.