The PHENIX experiment at the Relativistic Heavy Ion Collider has measured low mass vector meson, \(\omega\), \(\rho\), and \(\phi\), production through the dimuon decay channel at forward rapidity ...(\(1.2<|y|<2.2\)) in $p$$+$$p\( collisions at \)\sqrt{s}=200\( GeV. The differential cross sections for these mesons are measured as a function of both \)p_T\( and rapidity. We also report the integrated differential cross sections over \)1<p_T<7\( GeV/\)c\( and \)1.2<|y|<2.2\(: \)d\sigma/dy(\omega+\rho\rightarrow\mu\mu) = 80 \pm 6 \mbox{(stat)} \pm 12 \mbox{(syst)}\( nb and \)d\sigma/dy(\phi\rightarrow\mu\mu) = 27 \pm 3 \mbox{(stat)} \pm 4 \mbox{(syst)}$ nb. These results are compared with midrapidity measurements and calculations.
Two-pion interferometry measurements in $d$$+\(Au and Au\)+\(Au collisions at \)\sqrt{s_{{NN}}}=200\( GeV are used to extract and compare the Gaussian source radii R\)_{{\rm out}}\(, R\)_{{\rm ...side}}\(, and R\)_{{\rm long}}\(, which characterize the space-time extent of the emission sources. The comparisons, which are performed as a function of collision centrality and the mean transverse momentum for pion pairs, indicate strikingly similar patterns for the \)d$$+\(Au and Au\)+\(Au systems. They also indicate a linear dependence of R\)_{{\rm side}}\( on the initial transverse geometric size \)\bar{R}\(, as well as a smaller freeze-out size for the \)d$$+\(Au system. These patterns point to the important role of final-state rescattering effects in the reaction dynamics of \)d$$+$Au collisions.
A prototype silicon-tungsten electromagnetic calorimeter for an ILC detector was tested in 2007 at the CERN SPS test beam. Data were collected with electron and hadron beams in the energy range 8 to ...80 GeV. The analysis described here focuses on the interactions of pions in the calorimeter. One of the main objectives of the CALICE program is to validate the Monte Carlo tools available for the design of a full-sized detector. The interactions of pions in the Si-W calorimeter are therefore confronted with the predictions of various physical models implemented in the GEANT4 simulation framework.
An analog hadron calorimeter (AHCAL) prototype of 5.3 nuclear interaction lengths thickness has been constructed by members of the CALICE Collaboration. The AHCAL prototype consists of a 38-layer ...sandwich structure of steel plates and highly-segmented scintillator tiles that are read out by wavelength-shifting fibers coupled to SiPMs. The signal is amplified and shaped with a custom-designed ASIC. A calibration/monitoring system based on LED light was developed to monitor the SiPM gain and to measure the full SiPM response curve in order to correct for non-linearity. Ultimately, the physics goals are the study of hadron shower shapes and testing the concept of particle flow. The technical goal consists of measuring the performance and reliability of 7608 SiPMs. The AHCAL was commissioned in test beams at DESY and CERN. The entire prototype was completed in 2007 and recorded hadron showers, electron showers and muons at different energies and incident angles in test beams at CERN and Fermilab.
Measurements of transverse-single-spin asymmetries (\(A_{N}\)) in $p$$+$$p\( collisions at \)\sqrt{s}=\(62.4 and 200 GeV with the PHENIX detector at RHIC are presented. At midrapidity, \)A_{N}\( is ...measured for neutral pion and eta mesons reconstructed from diphoton decay, and at forward rapidities, neutral pions are measured using both diphotons and electromagnetic clusters. The neutral-pion measurement of \)A_{N}\( at midrapidity is consistent with zero with uncertainties a factor of 20 smaller than previous publications, which will lead to improved constraints on the gluon Sivers function. At higher rapidities, where the valence quark distributions are probed, the data exhibit sizable asymmetries. In comparison with previous measurements in this kinematic region, the new data extend the kinematic coverage in \)\sqrt{s}\( and \)p_T\(, and it is found that the asymmetries depend only weakly on \)\sqrt{s}\(. The origin of the forward \)A_{N}\( is presently not understood quantitatively. The extended reach to higher \)p_T\( probes the transition between transverse momentum dependent effects at low \)p_T\( and multi-parton dynamics at high \)p_T$.
Nitrogen and phosphorus in 6H-SiC were investigated with electron paramagnetic resonance (EPR) at 10 GHz and at 140 GHz and with electron nuclear double resonance (ENDOR). The phosphorus defects were ...prepared by neutron transmutation of
30Si in 6H-SiC. We observed two sets of EPR spectra due to two different phosphorus-related defects. Both EPR spectra exhibit a strong temperature dependence. It is proposed, that one of these EPR spectra is due to the isolated shallow phosphorus donor on Si sites and the other due to a P-vacancy-pair defect. The electronic structures of the shallow donors P and N are discussed using effective mass theory. It is shown that the shallow P donor on the hexagonal site has not yet been observed.
