Showing papers in "Physical Review in 2003"

Global nature of dilute-to-dense transition of granular flows in a 2D channel

Abstract: The dilute-to-dense transition of granular flow of particle size d(0) is studied experimentally in a two-dimensional channel (width D) with confined exit (width d). Our results show that with fixed d and D there is a maximum inflow rate Q(c) above which the flow changes from dilute to dense and the outflow rate drops abruptly from Q(c) to a dense rate Q(d). A rescaled critical rate q(c) is found to be a function of a scaling variable lambda only: q(c)similar toF(lambda), where lambdaequivalent tod/d(0) d/D-d. This form of lambda suggests that the dilute-to-dense transition is a global property of the flow, unlike the jamming transition which depends only on d/d(0). Furthermore, the transition is found to occur when the area fraction of particles near the exit exceeds a critical value which is close to 0.65+/-0.03.

Guided simulated annealing method for optimization problems

Abstract: Incorporating the concept of order parameter of the mean-field theory into the simulated annealing method, we present an optimization algorithm, the guided simulated annealing method. In this method mean-field order parameters are calculated to guide the configuration search for the global minimum. Allowing fluctuations and improvement of mean-field values iteratively, this method successfully identifies global minima for several difficult optimization problems. Application of this method to the HP lattice-protein model has found another lowest-energy state for an $N=100$ sequence that was not found by other methods before. Results for spin glass models are also presented which show improvement over the previous results.

Search for neutrino-induced cascades with the AMANDA detector

Abstract: J. Ahrens, X. Bai, G. Barouch, S.W. Barwick, R.C. Bay, T. Becka, K.-H. Becker, D. Bertrand, F. Binon, A. Biron, S. Böser, J. Booth, O. Botner, A. Bouchta, a O. Bouhali, M.M. Boyce, T. Burgess, S. Carius, A. Chen, D. Chirkin, J. Conrad, J. Cooley, C.G.S. Costa, D.F. Cowen, A. Davour, C. De Clercq, T. DeYoung, b P. Desiati, J.-P. Dewulf, P. Doksus, P. Ekström, T. Feser, J.-M. Frère, T.K. Gaisser, M. Gaug, A. Goldschmidt, A. Hallgren, F. Halzen, K. Hanson, R. Hardtke, T. Hauschildt, M. Hellwig, G.C. Hill, P.O. Hulth, K. Hultqvist, S. Hundertmark, J. Jacobsen, A. Karle, J. Kim, B. Koci, L. Köpke, M. Kowalski, J.I. Lamoureux, H. Leich, M. Leuthold, P. Lindahl, I. Liubarsky, D.M. Lowder, c J. Madsen, P. Marciniewski, H.S. Matis, C.P. McParland, T.C. Miller, d Y. Minaeva, P. Miočinović, P.C. Mock, e R. Morse, T. Neunhöffer, P. Niessen, D.R. Nygren, H. Ogelman, Ph. Olbrechts, C. Pérez de los Heros, A.C. Pohl, R. Porrata, f P.B. Price, G.T. Przybylski, K. Rawlins, C. Reed, g E. Resconi, W. Rhode, M. Ribordy, S. Richter, J. Rodŕıguez Martino, P. Romenesko, D. Ross, H.-G. Sander, T. Schmidt, D. Schneider, R. Schwarz, A. Silvestri, M. Solarz, G.M. Spiczak, C. Spiering, N. Starinsky, h D. Steele, P. Steffen, R.G. Stokstad, K.-H. Sulanke, I. Taboada, i L. Thollander, S. Tilav, M. Vander Donckt, C. Walck, C. Weinheimer, C.H. Wiebusch, a C. Widemann, R. Wischnewski, H. Wissing, K. Woschnagg, W. Wu, G. Yodh, and S. Young

Including Systematic Uncertainties in Confidence Interval Construction for Poisson Statistics

Abstract: Including Systematic Uncertainties in Confidence Interval Construction for Poisson Statistics

A direct simulation Monte Carlo method for the Uehling-Uhlenbeck-Boltzmann equation

Abstract: In this paper we describe a DSMC algorithm for the Uehling-Uhlenbeck-Boltzmann equation in terms of Markov processes. This provides a unifying framework for both the classical Boltzmann case as well as the Fermi-Dirac and Bose-Einstein cases. We establish the foundation of the algorithm by demonstrating its link to the kinetic equation. By numerical experiments we study its sensitivity to the number of simulation particles and to the discretization of the velocity space, when approximating the steady state distribution. ∗Permanent address: Dept. Physics, San Jose State Univ., San Jose CA, USA

Scaling proporties of saddle-node bifurcations on fractal basin boundaries

Abstract: We analyze situations where a saddle-node bifurcation occurs on a fractal basin boundary. Specifically, we are interested in what happens when a system parameter is slowly swept in time through the bifurcation. Such situations are known to be indeterminate in the sense that it is difficult to predict the eventual fate of an orbit that tracks the prebifurcation node attractor as the system parameter is swept through the bifurcation. In this paper we investigate the scaling of (1) the fractal basin boundary of the static (i.e., unswept) system near the saddle-node bifurcation, (2) the dependence of the orbit's final destination on the sweeping rate, (3) the dependence of the time it takes for an attractor to capture a swept orbit on the sweeping rate, and (4) the dependence of the final attractor capture probability on the noise level. With respect to noise, our main result is that the effect of noise scales with the 5/6 power of the parameter drift rate. Our approach is to first investigate all these issues using one-dimensional map models. The simplification of treatment inherent in one dimension greatly facilitates analysis and numerical experiment, aiding us in obtaining the new results listed above. Following our one-dimensional investigations, we explain that these results can be applied to two-dimensional systems. We show, through numerical experiments on a periodically forced second-order differential equation example, that the scalings we have found also apply to systems that result in two-dimensional maps.

Experimental limits on the width of the reportedTheta(1540)

Abstract: LBNL-54065 Ep erimental Limits on the Width of the Reported ©(ISO) Robert N. Cahn and George H. Trilling Lawrence Berkeley National Laboratory 1 Cyclotron Rd., Berkeley, GA 94720) (Dated: November 19, 2003) Using data on K collisions on xenon and deuterium we derive values and limits on the width of the reported 0(154O) exotic baryon resonance. The xenon experiment gives a width of 0.9 ± 0.3 MeV. The other experiments give upper limits in the range 1-4 MeV. PACS numbers: 14.20.-c, 13.75.-n I. INTRODUCTION where we have taken the values for K n collisions at a resonant mass mo of 1540 MeV and assumed that the res- onance has J = 1/2. As we shall see, the mass resolution of the experiments is always broader than the natural width of the resonance so that the observable quantity is the integral of the resonant cross section: The general features of the spectroscopy of mesons and baryons can be understood from the simple rules that a meson is made of a quark and an antiquark, while a baryon is made from three quarks. These rules are consistent with the principles of quantum chromodynam- ics, which show that physical particles are neutral under color-SI/(3). However, QCD does not preclude the ex- istence of other colorless configurations, including glu- ons or additional quarks and antiquarks. Recent results from a diverse collection of experiments [1-6] show evi- dence for a state @(1540) , whose quantum numbers are those of the combination uudds and which thus cannot be composed simply of three quarks. Such states have been predicted [7] in a Skyrmion model. t _(m^m ) Bi Bf II. AT + T /4 TTT —^-(To (107 mb) x The @(1540) has not been detected in data from a number of early experiments in which one might expect it to appear. However, definitive negative conclusions cannot be drawn in the absence of reliable predictions for production cross sections. r /4 dm B Bf ao BiBfT K°p IN XENON In situations where the @(1540) is or ought to be formed resonantly, 3S 3X1 intermediate state in a scatter- ing experiment, it is possible to draw conclusions about its width from existing data. Such results can provide guidance to the structure of the resonance, or more im- portant, to the likelihood that there truly is a such reso- nance. The resonant cross section is determined entirely by F, the width of the resonance and its branching ratios B and Bf into the initial and final channels according to the Breit-Wigner form: t a(m) r /4 = Bi Bf CT _(m^m ) +r /4. With k as the CM momentum, si and s the incident spins and J the spin of the resonance, we have 2J+ 1 4TT (2si + l)(2s + l) k 68 mb In the DIANA experiment [2], in which a K beam with momentum 750 MeV entered a xenon bubble cham- ber, the signal for the @(1540) was observed by measur- ing the pKs invariant mass spectrum in the final state. If we treat the scattering as simply a two-body process, K n —¥ K°p, resonance occurs when the combination of the incident momentum of the K and the Fermi mo- mentum of the neutron give the invariant mass of the @(1540) . Without the Fermi momentum, this would occur for a K momentum of 440 MeV, to which the incident beam is reduced by ionization losses after pen- etrating a sufficient distance through the xenon. By ob- serving the final-state invariant mass, reconstructed from the pKs, the effects of Fermi motion and incident beam degradation are removed, provided that we can ignore rescattering within the nucleus. The signal in this experiment emerges only after mak- ing cuts that are believed to reduce the effect of rescat- tering. We make the assumption that, in the mass region near the resonance, it is the charge-exchange process on a single nucleon that is observed and that the cuts reduce the resonant and non-resonant charge-exchange processes by the same factor. The apparent resonant signal is con- tained within two 5-MeV bins. The background varies smoothly in this region at a value near 22 events per

Predicting proton-nucleus total reaction cross sections up to 300 MeV using a simple functional form

Abstract: Total reaction cross sections are predicted for proton scattering from various nuclei. A simple functional form has been used that reproduces them for the scattering from (15) nuclei spanning the mass range from 9Be to 238U and for proton energies 10-300 MeV.

Hadronic charmed meson decays involving axial vector mesons

Abstract: Cabibbo-allowed charmed meson decays into a pseudoscalar meson and an axial-vector meson are studied. The charm to axial-vector meson transition form factors are evaluated in the Isgur-Scora-Grinstein-Wise quark model. The dipole momentum dependence of the $\stackrel{\ensuremath{\rightarrow}}{D}K$ transition form factor and the presence of a sizable long-distance W exchange are the two key ingredients for understanding the data of $\stackrel{\ensuremath{\rightarrow}}{D}\overline{K}{a}_{1}.$ The ${K}_{1A}\ensuremath{-}{K}_{1B}$ mixing angle of the strange axial-vector mesons is found to be $\ensuremath{\approx}\ifmmode\pm\else\textpm\fi{}37\ifmmode^\circ\else\textdegree\fi{}$ or $\ifmmode\pm\else\textpm\fi{}58\ifmmode^\circ\else\textdegree\fi{}$ from $\stackrel{\ensuremath{\rightarrow}}{\ensuremath{\tau}}{K}_{1}{\ensuremath{ u}}_{\ensuremath{\tau}}$ decays. The study of $\stackrel{\ensuremath{\rightarrow}}{D}{K}_{1}(1270)\ensuremath{\pi},$ ${K}_{1}(1400)\ensuremath{\pi}$ decays excludes the positive mixing-angle solutions. It is pointed out that an observation of the decay ${D}^{0}\ensuremath{\rightarrow}{K}_{1}^{\ensuremath{-}}(1400){\ensuremath{\pi}}^{+}$ at the level of $5\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}$ will rule out $\ensuremath{\theta}\ensuremath{\approx}\ensuremath{-}37\ifmmode^\circ\else\textdegree\fi{}$ and favor the solution $\ensuremath{\theta}\ensuremath{\approx}\ensuremath{-}58\ifmmode^\circ\else\textdegree\fi{}.$ Though the decays ${D}^{0}\ensuremath{\rightarrow}{K}_{1}^{0}{\ensuremath{\pi}}^{0}$ are color suppressed, they are comparable to and even larger than the color-allowed counterparts ${K}_{1}^{0}(1270){\ensuremath{\pi}}^{0}\ensuremath{\sim}{K}_{1}^{\ensuremath{-}}(1270){\ensuremath{\pi}}^{+}$ and ${K}_{1}^{0}(1400){\ensuremath{\pi}}^{0}g{K}_{1}^{\ensuremath{-}}(1400){\ensuremath{\pi}}^{+}.$ The finite width effect of the axial-vector resonance is examined. It becomes important for ${a}_{1}(1260)$ in particular when its width is near 600 MeV.

Vertical friedel oscillations in interface-induced surface charge modulations of ultrathin quantum islands

Abstract: Two-dimensional Pb islands of a few atomic layers are grown on the incommensurate Si(111)-Pb surface at low temperatures. Among them, two types of islands having different stacking with the substrate are observed. These islands, respectively, display an alternating image contrast with their thickness. Besides, the contrasts of the islands of different types are complementary to each other layer by layer. These intriguing behaviors do not show significant bias dependence throughout the range from -3 to +3 V and can be explained by the vertical charge oscillation with the growth of a new layer. The charge oscillation in the out-of-plane direction originates from electron scattering by the in-plane potential variation at the Pb/Si interface.

Transition from Kardar-Parisi-Zhang to tilted interface critical behavior in a solvable asymmetric avalanche model

Abstract: 255701-1 We use a discrete-time formulation of the asymmetric avalanche process (ASAP) [Phys. Rev. Lett. 87, 084301 (2001)] of p particles on a finite ring of N sites to obtain an exact expression for the average avalanche size as a function of toppling probabilities and particle density p=N. By mapping the model onto driven interface problems, we find that the ASAP incorporates the annealed Kardar-PariziZhang and quenched tilted interface dynamics for c, respectively, with c being the critical density for given toppling probabilities and N ! 1. We analyze the crossover between two regimes and show which parameters are relevant near the transition point.