Y. AKIBA, D. BEAVIS, P. BEERY, H.C. BRITT, B. BUDICK, C. CHASMAN, Z. CHEN, C.Y. CHI, Y.Y. CHU, V. CIANCIOLO, B.A. COLE, J.B. COSTALES, H.J. CRAWFORD, J.B. CUMMING R. DEBBE, J. ENGELAGE, S.Y. FUNG, M. GONIN, S. GUSHUE, H. HAMAGAKI, O. HANSEN, R.S. HAYANO, S. HAYASHI, S. HOMMA, H.HUANG,H. KANEKO, J. KANG, S. KAUFMAN, W. KEHOE, K. KURITA, R.J. LEDOUX, MJ. LEVINE, Y. MIAKE, D. MORRISON, R.J. MORSE, B. MOSKOWITZ, S. NAGAMIYA, M.N. NAMBOODIRI, T. NAYAK, J. OLNESS, C.G. PARSONS, L.P. REMSBERG, D. ROEHRICH, P. ROTHSCHILD, H. SAKURAI, T.C. SANGSTER, R. SETO, R. SOLTZ, S.G. STEADMAN, G.S.F. STEPHANS, T. SUNG, S. TANAKA, Y. TANAKA, M.J. TANNENBAUM, J. THOMAS, J.H. VAN DIJK, F. VIDEB^K, O. VOSSNACK, V. VUTSADAKIS, F.Q. WANG, Y. WANG, H.E. WEGNER, D.S. WOODRUFF, Y.D. WU, AND W. ZAJC

In a previous publication [T. Abbott , E802 Collaboration, Phys. Rev. C 63, 064602 (2001); 64, 029901(E) (2001)], measurements of the A dependence and pseudorapidity interval (deltaeta) dependence of midrapidity E-T distributions in a half-azimuth (Deltaphi=pi) electromagnetic calorimeter were presented for p+Be, p+Au, O+Cu, Si+Au, and Au+Au collisions at the BNL-AGS. The validity of the "nuclear geometry" characterization versus deltaeta was illustrated by plots of the E-T(deltaeta) distribution in each deltaeta interval in units of the measured (p+Au) in the same deltaeta interval for p+Au collisions. These plots, with aperture corrected scale in the physically meaningful units of number of average observed p+Au collisions, were nearly universal as a function of deltaeta, confirming that the reaction dynamics for E-T production at midrapidity at AGS energies is governed by the number of projectile participants and can be well characterized by measurements in apertures as small as Deltaphi=pi,deltaeta=0.3. A key ingredient in these analyses is the probability p(0) for no signal to be detected in a given aperture deltaeta for the fundamental p+Au collision. In fact the measured (p+Au) is biased and the true (true)(p+Au) for the detector aperture is the measured value times 1-p(0). The issues and merits of measuring the E-T(deltaeta) distribution in units of (p+Au) or (true)(p+Au) in the same deltaeta interval are presented and discussed. This method has application at RHIC, where p-p data could be used as the reference distribution for two participants. The E-T distributions for B+A collisions, with E-T(deltaeta) scale normalized by (true)(p-p) in the same aperture for p-p collisions, would then be given directly in the popular unit "per participant-pair" [K. Adcox , PHENIX Collaboration, Phys. Rev. Lett. 86, 3500 (2001); I. G. Bearden , BRAHMS Collaboration, Phys. Lett. B523, 227 (2001); B. B. Back , PHOBOS Collaboration, Phys. Rev. C 65, 031901(R) (2002); C. Adler , STAR Collaboration, Phys. Rev. Lett. 89, 202301 (2002)].

We studied the transport properties of spin-polarized conduction electrons in GaAs by time-resolved photoinjection and photoluminescence polarization measurements. Under an electric field of a few kV/cm, the degree of the spin polarization considerably decreases during drift transport over the distance shorter than 4 μm. Spin relaxation by D'yakonov–Perel' mechanism is suggested to be the cause of such a rapid spin depolarization for hot electrons under a moderate electric field at low temperatures.

We report the magneto-optical studies on the EuTe epilayer grown by molecular beam epitaxy. Huge Zeeman shift of the excitonic photoluminescence is observed. The circular polarization property of the photoluminescence is investigated. An evident hysteresis behavior of the circular polarization for the excitonic photoluminescence is resolved, indicating the existence of the initial magnetization due to the formation of dense bound magnetic polaron.

Two-pion correlation functions are analyzed at mid-rapidity for three systems (14.6 A-GeV Si+Al, Si+Au, and 11.6 A-GeV Au+Au), seven distinct centrality conditions, and different kT bins in the range 0.1--0.5 GeV/c. Source reference frames are determined from fits to the Yano-Koonin source parameterization. Bertsch-Pratt radius parameters are shown to scale linearly with both number of projectile and total participants as obtained from a Glauber model calculation. A finite emission duration that increases linearly with system/centrality is also reported. The mT dependence of the Bertsch-Pratt radii is measured for the central Si+Au and Au+Au systems. The system/centrality dependence is investigated separately for both high and low mT regions.

We present a novel way of synthesising highly ordered arrays of Cd 1-x Mn x S and Cd 1-x Mn x Se quantum wires with lateral dimensions of 3 nm separated by 2 nm SiO 2 barriers by incorporating the (II,Mn)VI semiconductor with 0 ≤ x ≤ 1 into the pore system of mesoporous MCM-41 SiO 2 matrices. The electronic and excitonic properties were studied using photoluminescence and photoluminescence excitation spectroscopy at low temperatures and in magnetic fields up to 7.5 T. Due to the quantum confinement of the excitons in the wires an increase of the direct band gap by about 200 meV for (Cd, Mn)S and by about 350 meV for (Cd, Mn)Se is observed. In addition, we observe a much stronger, p-d hybridisation related band gap bowing as a function of Mn-concentration in the wires compared to bulk. This effect is related to the increase of the band gap due to the quantum confinement which shifts the p-like valence band edge closer to the Mn-3d-related states in the valence band. Surprisingly, the s,p-d exchange induced giant Zeeman splitting of the excitons in the (Cd,Mn)Se wires compared to those in bulk material appears to be very small. The magnetic properties of the samples were studied by SQUID and electron paramagnetic resonance measurements in the temperature range from 2 to 300 K. Compared to the bulk (II, Mn)VI compounds, a reduced antiferromagnetic coupling between the magnetic moments of the Mn 2+ ions is found. For x > 0.8, a suppression of the paramagnetic to antiferromagnetic phase transition of the Mn-system is observed because the lateral dimensions of the wires are smaller than the magnetic length scale of the antiferromagnetic ordering.

The utility of ICRF heating in the LHD was demonstrated in the third campaign carried out in 1999. This paper summarizes the investigations made in 2000 with a focus on the optimization of ICRF heating. The flexibility of the LHD magnetic configuration was fully utilized as a key factor in the investigations. The experiments include (a) scan of magnetic field intensity, (b) scan of aspect ratio, (c) scan of magnetic axis shift, (d) scan of quadrupole magnetic field, and (e) cancellation of magnetic island. The performance of the ICRF heating was thus optimized with respect to magnetic parameters, while optimization was achieved mainly with respect to heating regime and wall conditioning in the third campaign. Some of these parameters are directly related to the orbit of trapped particles. Therefore, the relation between particle orbits and the performance of ICRF heating is also addressed in this paper based on analyses of the high-energy tail of ions.

We studied the transport of photoinjected spins in GaAs by time-resolved photoluminescence measurements. At low temperatures, the spin polarization after drift transport of 4 μm is found to decrease as the applied electric field E increases to a few kV/cm, and it disappears when E exceeds 3 kV/cm. The origin of the field-dependent spin relaxation is discussed.

Spin injection processes of excitons were studied by time-resolved photoluminescence in double quantum wells consisting of Cd0.95Mn0.05Te and CdTe layers. Selective excitation of the magnetic and non-magnetic wells confirms the dominant spin injection process from the magnetic well to the non-magnetic well. The exciton spin injection from the magnetic quantum well of Cd0.95Mn0.05Te arises with an injection time of 10 ps and induces a transient spin polarization with the degree of 0.20 in the non-magnetic well of CdTe. The exciton spin relaxation time in the CdTe well was found to be sufficiently longer than the exciton lifetime of 38 ps.

Measurements of the A dependence and pseudorapidity interval (delta eta) dependence of midrapidity E-T distributions in a half-azimuth (Delta phi = pi) electromagnetic calorimeter are presented for p + Be, p + Au, O + Cu, Si + Au, and Au + Au collisions at the BNL-AGS (Alternating-Gradient Synchrotron). The shapes of the upper edges of midrapidity E-T distributions as a function of the pseudorapidity interval delta eta in the range 0.3 to 1.3, roughly centered at midrapidity, are observed to vary with delta eta. like multiplicity-the upper edges of the distributions flatten as delta eta is reduced. At the typical fixed upper percentiles of E-T distributions used for nuclear geometry characterization by centrality definition-7 percentile, 4 percentile, 2 percentile, I percentile, 0.5 percentile-the effect of this variation in shape on the measured projectile A(p) dependence for O-16, Si-28, Au-197 projectiles on an Au target is small for the ranges of delta eta and percentile examined. The E-T distributions for p + Au and p + Be change in shape with delta eta; but in each delta eta interval the shapes of the p + Au and p + Be distributions remain indentical with each other-a striking confirmation of the absence of multiple-collision effects at midrapidity at AGS energies. The validity of the nuclear geometry characterization versus delta eta is illustrated by plots of the E-T(delta eta) distribution in each delta eta interval in units of the measured (p + Au) same delta eta interval for p + Au collisions. These plots, in the physically meaningful units of "number of average p + Au collisions," are nearly universal as a function of delta eta confirming that the reaction dynamics for E-T production at midrapidity at AGS energies is governed by the number of projectile participants and can be well characterized by measurements in apertures as small as Delta phi = pi, delta eta = 0.3.

Proton and deuteron distributions from 11.6A GeV/c Au + Au collisions measured by the E802 Collaboration in experiment E-866 are presented. The invariant yield of protons and deuterons is studied as a function of the transverse mass for different cuts of rapidity and centrality. At low m(t)-m(0) the proton and deuteron invariant spectra deviate from a single exponential shape. The average m(t) as function of centrality and rapidity is used to explore the effect of collective transverse flow in the reaction. The ratio of the deuteron to squared proton yield as a function of transverse momentum, rapidity, and centrality is used to probe the coalescence model of deuteron production. This ratio is constant as a function of rapidity only for the most central cuts and decreases with the centrality for every rapidity cut. The ratio of the differential cross section of the deuteron to the squared differential cross section of the proton, for the most central cut, is not constant as a function of m(t)-m(0). [S0556-2813(99)04911-0].