Smooth leading edge transition in hypersonic flow

The boundary layer transition along the attachment line of a smooth swept circular cylinder in hypersonic flow is investigated in a blowdown wind tunnel. A wide range of spanwise Mach numbers Me (3.28 to 6.78) is covered with the help of different models at several sweep angles (60 degrees less than or equal to Lambda less than or equal to 80 degrees). The transition is indirectly detected by means of heat flux measurements. The influence of the wall to stagnation temperature ratio is investigated by cooling the model with liquid nitrogen

Modular Invariant Gaugino Condensation in the Presence of an Anomalous U(1)

Starting from the previously constructed effective supergravity theory below the scale of U(1) breaking in orbifold compactifications of the weakly coupled heterotic string, we study the effective theory below the scale of supersymmetry breaking by gaugino and matter condensation in a hidden sector. Issues we address include vacuum stability, soft supersymmetry-breaking masses in the observable sector, and the masses of the various moduli fields, including those associated with flat directions at the U(1)-breaking scale, and of their fermionic superpartners. The consistent treatment of U(1) breaking together with condensation yields qualitatively new results.Comment: 73 pages, full postscript also available from http://phyweb.lbl.gov/theorygroup/papers/53960.p

Jet-like correlations between Forward- and Mid- rapidity in p+p, d+Au and Au+Au collisions from STAR at 200 GeV

In this proceedings we present STAR measurements of two particle azimuthal correlations between trigger particles at mid-rapidity ($|\eta|<$ 1) and associated particles at forward rapidities (2.7 $<|\eta|<$ 3.9) in p+p, d+Au and Au+Au collisions at $\sqrt{s_{NN}}$= 200 GeV. Two particle azimuthal correlations between a mid-rapidity trigger particle and forward-rapidity associated particles preferably probe large-x quarks scattered off small-x gluons in RHIC collisions. Comparison of the separate d- and Au-side measurements in d+Au collisions may potentially probe gluon saturation and the presence of Color Glass Condensate. In Au+Au collisions quark energy loss can be probed at large rapidities, which may be different from gluon energy loss measured at mid-rapidity.Comment: Quark Matter 06 Conference proceedings, submitted to Journal of Phys.

Physics with Identified Particles at STAR

New physics results with identified particles at STAR are presented. Measurements at low $p_T$ address bulk properties of the collision, while those at high $p_T$ address jet energy loss in the bulk matter produced. Between these extremes, measurements at intermediate $p_T$ address the interplay between jets and the bulk. We highlight: measurements of $v_2$ fluctuations as a new, sensitive probe of the initial conditions and the equation of state; correlations involving multi-strange particles, along with ratios of identified particles to test coalescence as a mechanism of particle production at intermediate $p_T$; three particle azimuthal correlation to search for conical emission; and the energy and particle-type dependence of hadron production at high $p_T$ to study quark and gluon jet energy loss.Comment: 9 pages, 7 figures. To appear in the proceedings of the 19th International Conference on Ultra-Relativistic Nucleus-Nucleus Collisions (Quark Matter 2006), Shanghai, China, November 14-20, 200

π,K,p\pi, K, p and pˉ\bar{p} production from Au+Au collisions at sNN=62.4\sqrt{s_{_{NN}}} = 62.4 GeV

The preliminary results of $\pi^{\pm}, K^{\pm}, p$ and $\bar{p}$ spectra are reported from Au+Au collisions at $\sqrt{s_{_{NN}}} = 62.4$ GeV. Particle identification is from the Time Projection Chamber and Time-of-Flight system at STAR. The nuclear modification factor $R_{CP}$ for mesons ($\pi^{\pm}, K^{\pm}$) and baryons ($p, \bar{p}$) will also be discussed.Comment: 5 pages, 4 figures, Contributed to 8th International Conference on Strangeness in Quark Matter (SQM 2004),to be published in Journal of Physics

Anomalous centrality variation of minijet angular correlations in Au-Au collisions at 62 and 200 GeV from STAR

We have measured 2D autocorrelations for all charged hadrons in STAR with $p_{t}$ $>$ 0.15 GeV/c and $| \eta |$ $<$ 1 from Au+Au collisions at 62 and 200 GeV. The correlation structure is dominated by a peak centered at zero relative opening angles on $\eta$ and $\phi$ which we hypothesize is caused by minimum-bias jets (minijets). We observe a large excess of minijet correlations in more-central Au-Au collisions relative to binary-collision scaling (more correlated pairs than expected from surface emission or even volume emission). We also observe a sudden increase of the minijet peak amplitude and $\eta$ width relative to binary-collision scaling of scattered partons which occurs at an energy-dependent centrality point. There is a possible scaling of the transition point with transverse particle density.Comment: Quark Matter 2008 proceedings, submitted to Journal of Physics G. v2: added STAR Collaboration to author lis

K* production in Cu+Cu and Au+Au collisions at sqrt(s_{NN}) = 62.4 GeV and 200 GeV in STAR

We report the measurements of $p_T$ spectra of $K^*$ up to intermediate $p_T$ region in mid-rapidity through its hadronic decay channel using the STAR detector in Au+Au and Cu+Cu collisions at $\sqrt{s_{\mathrm{NN}}}$= 62.4 GeV and 200 GeV. Particle ratios such as $K^{*}/K$ and $K^{*}/\phi$ is used to understand the rescattering and regeneration effect on $K^{*}$ production in the hadronic medium. The $K^*$ $v_{2}$ measurement using a high statistics Au+Au 200 GeV dataset and nuclear modification factor measurement supports the quark coalescence model of particle production in the intermediate $p_T$ range.Comment: 5 page

Centrality dependence of the N(Ω)/N(ϕ)N(\Omega)/N(\phi) ratios and ϕ\phi v2v_{2} - a test of thermalization in Au+Au collisions at RHIC

We present the centrality dependence of the $N(\Omega)/N(\phi)$ ratios and $\phi$ $v_{2}$ measured in Au+Au collisions at $\sqrt{s_{NN}}=200$ GeV by the STAR experiment at RHIC. The results are compared to measurements of other identified particles and recombination model expectations in order to gain insight into the partonic collectivity and possible thermalization of the produced medium.Comment: 4 pages, 2 figures, Quark Matter 2006 conference proceeding

How well does NLO pQCD describe strangeness in p+pp+p collisions at s\sqrt{s}= 200 GeV in STAR?

We present measurements of the transverse momentum spectra for $\mathrm{K^{0}_{S}}$, $\Lambda$, $\Xi$ and their antiparticles in p+p collisions at $\sqrt{s}=200 GeV$. The extracted mid-rapidity yields and $$ are in agreement with previous $p+\bar{p}$ experiments while they have smaller statistical errors. We compare the measured spectra for $\mathrm{K^{0}_{S}}$ and $\Lambda$ to the latest available calculations from NLO pQCD and see good agreement for the $\mathrm{K^{0}_{S}}$ above 1.5 GeV/c.Comment: conference proceedings, Strangeness in Quark Matter 2004, 5 pages, submitted to Journal Physics G, final version submitted to journal incl. modifications requested by edito

Incident-energy and system-size dependence of directed flow

We present STAR's measurements of directed flow for charged hadrons in Au+Au and Cu+Cu collisions at $\sqrt{s_\mathrm{NN}} = 200$ GeV and 62.4 GeV, as a function of pseudorapidity, transverse momentum and centrality. We find that directed flow depends on the incident energy, but not on the system size. We extend the validity of limiting fragmentation hypothesis to different collision systems.Comment: Quark Matter 2006 proceedings, 4 pages, 4 figures, submitted to J. Phys.