Hadrons carrying open heavy flavor, i.e. single charm or bottom quarks, are among the key diagnostic tools available today for the hot and dense state of strongly interacting matter which is produced ...in collisions of heavy atomic nuclei at ultra-relativistic energies. First systematic heavy-flavor measurements in nucleus–nucleus collisions and the reference proton–proton system at Brookhaven National Laboratory’s (BNL) Relativistic Heavy Ion Collider (RHIC) have led to tantalizing results. These studies are now continued and extended at RHIC and at CERN’s Large Hadron Collider (LHC), where considerably higher collision energies are available. This review focuses on experimental results on open heavy-flavor observables at RHIC and the LHC published until July 2012. Yields of heavy-flavor hadrons and their decay products, their transverse momentum and rapidity distributions, as well as their azimuthal distributions with respect to the reaction plane in heavy-ion collisions are investigated. Various theoretical approaches are confronted with the data and implications for the properties of the hot and dense medium produced in ultra-relativistic heavy-ion collisions are discussed.
We report on broadly based systematic investigations of the modeling components for open heavy-flavor diffusion and energy loss in strongly interacting matter in their application to heavy-flavor ...observables in high-energy heavy–ion collisions, conducted within an EMMI Rapid Reaction Task Force framework. Initial spectra including cold-nuclear-matter effects, a wide variety of space-time evolution models, heavy-flavor transport coefficients, and hadronization mechanisms are scrutinized in an effort to quantify pertinent uncertainties in the calculations of nuclear modification factors and elliptic flow of open heavy-flavor particles in nuclear collisions. We develop procedures for error assessments and criteria for common model components to improve quantitative estimates for the (low-momentum) heavy-flavor diffusion coefficient as a long-wavelength characteristic of QCD matter as a function of temperature, and for energy loss coefficients of high-momentum heavy-flavor particles.
We report on a precision measurement of low-mass muon pairs in 158 AGeV indium-indium collisions at the CERN SPS. A significant excess of pairs is observed above the yield expected from neutral meson ...decays. The unprecedented sample size of 360,000 dimuons and the good mass resolution of about 2% allow us to isolate the excess by subtraction of the decay sources. The shape of the resulting mass spectrum is consistent with a dominant contribution from pi+pi- -->rho -->mu+mu- annihilation. The associated space-time averaged spectral function shows a strong broadening, but essentially no shift in mass. This may rule out theoretical models linking hadron masses directly to the chiral condensate.
GaAs-based InGaAsN quantum well films grown by molecular beam epitaxy are characterized by photoluminescence spectroscopy. InGaAsN with high N concentrations of about 4% requires a low growth ...temperature of 350
°C and minimal As flux. No indications for 3D growth are detected and carrier localization is below 25
meV. Broad area lasers with InGaAsN single quantum wells of different compositions are compared. Threshold current density correlates to room temperature photoluminescence intensity. For an emission wavelength of 1400
nm a threshold current density of 690
A/cm
2 is achieved with 1200
μm long devices. At 1510
nm a value of 780
A/cm
2 sets a new record for GaAs-based lasers with any kind of active material.
MXenes are being heavily investigated in biomedical research, with applications ranging from regenerative medicine to bioelectronics. To enable the adoption and integration of MXenes into therapeutic ...platforms and devices, however, their stability under standard sterilization procedures must be established. Here, we present a comprehensive investigation of the electrical, chemical, structural, and mechanical effects of common thermal (autoclave) and chemical (ethylene oxide (EtO) and H
O
gas plasma) sterilization protocols on both thin-film Ti
C
T
MXene microelectrodes and mesoscale arrays made from Ti
C
T
-infused cellulose-elastomer composites. We also evaluate the effectiveness of the sterilization processes in eliminating all pathogens from the Ti
C
T
films and composites. Post-sterilization analysis revealed that autoclave and EtO did not alter the DC conductivity, electrochemical impedance, surface morphology, or crystallographic structure of Ti
C
T
and were both effective at eliminating
from both types of Ti
C
T
-based devices. On the other end, exposure to H
O
gas plasma sterilization for 45 min induced severe degradation of the structure and properties of Ti
C
T
films and composites. The stability of the Ti
C
T
after EtO and autoclave sterilization and the complete removal of pathogens establish the viability of both sterilization processes for Ti
C
T
-based technologies.
.
The production of K
+
, K
-
and
(1020) mesons is studied in Al+Al collisions at a beam energy of 1.9A GeV which is close to or below the production threshold in NN reactions. Inverse slopes, ...anisotropy parameters, and total emission yields of K
±
mesons are obtained. A comparison of the ratio of kinetic energy distributions of K
-
and K
+
mesons to the HSD transport model calculations suggests that the inclusion of the in-medium modifications of kaon properties is necessary to reproduce the ratio. The inverse slope and total yield of
mesons are deduced. The contribution to K
-
production from
meson decays is found to be
%. The results are in line with the previous K
±
and
data obtained for different colliding systems at similar incident beam energies.
MXenes are being heavily investigated in biomedical research, with applications ranging from regenerative medicine to bioelectronics. To enable the adoption and integration of MXenes into therapeutic ...platforms and devices, however, their stability under standard sterilization procedures must be established. Here, we present a comprehensive investigation of the electrical, chemical, structural, and mechanical effects of common thermal (autoclave) and chemical (ethylene oxide (EtO) and H2O2 gas plasma) sterilization protocols on both thin-film Ti3C2T x MXene microelectrodes and mesoscale arrays made from Ti3C2T x -infused cellulose–elastomer composites. We also evaluate the effectiveness of the sterilization processes in eliminating all pathogens from the Ti3C2T x films and composites. Post-sterilization analysis revealed that autoclave and EtO did not alter the DC conductivity, electrochemical impedance, surface morphology, or crystallographic structure of Ti3C2T x and were both effective at eliminating E. coli from both types of Ti3C2T x -based devices. On the other end, exposure to H2O2 gas plasma sterilization for 45 min induced severe degradation of the structure and properties of Ti3C2T x films and composites. The stability of the Ti3C2T x after EtO and autoclave sterilization and the complete removal of pathogens establish the viability of both sterilization processes for Ti3C2T x -based technologies.
The PHENIX experiment has measured the contribution of heavy-flavor decays to single-electron spectra in Au + Au collisions at
√s
NN = 130GeV
and 200 GeV at RHIC, providing a first measure of the ...total charm yield and its dependence on collision centrality at the se energies. In addition,
J/Ψ charmonium states were reconstructed by PHENIX in their dilepton decay channels in p+p and Au+Au collisions at
√s
NN = 200GeV
.
Four different combinations of 9644Ru and 9640Zr nuclei, both as projectile and target, were investigated at the same bombarding energy of 400A MeV using a 4pi detector. The degree of isospin mixing ...between projectile and target nucleons is mapped across a large portion of the phase space using two different isospin-tracer observables, the number of measured protons and the tritium to 3He yield ratio. The experimental results show that the global equilibrium is not reached even in the most central collisions. Quantitative measures of stopping and mixing are extracted from the data. They are found to exhibit a quite strong sensitivity to the in-medium ( n,n) cross section used in microscopic transport calculations.
The NA60 experiment at the CERN SPS has studied low-mass muon pairs in 158 A GeV In–In collisions. A strong excess of pairs is observed above the yield expected from neutral meson decays. The ...unprecedented sample size close to 400000 events and the good mass resolution of about 2% made it possible to isolate the excess by subtraction of the decay sources. The shape of the resulting mass spectrum shows some non-trivial centrality dependence, but is largely consistent with a dominant contribution from π+π-→ϱ→μ+μ- annihilation. The associated ϱ spectral function exhibits considerable broadening, but essentially no shift in mass. The pT-differential mass spectra show the excess to be much stronger at low pT than at high pT. The results are compared to theoretical model predictions; they tend to rule out models linking hadron masses directly to the chiral condensate.
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