Constituent quark model for nuclear stopping in high energy nuclear collisions

We study the nuclear stopping in high energy nuclear collisions using the constituent quark model. It is assumed that wounded nucleons with different number of interacted quarks hadronize in different ways. The probabilities of having such wounded nucleons are evaluated for proton-proton, proton-nucleus and nucleus-nucleus collisions. After examining our model in proton-proton and proton-nucleus collisions and fixing the hadronization functions, it is extended to nucleus-nucleus collisions. It is used to calculate the rapidity distribution and the rapidity shift of final state protons in nucleus-nucleus collisions. The computed results are in good agreement with the experimental data on ^{32}\mbox{S} +\ ^{32}\mbox{S} at $E_{lab} = 200$ AGeV and ^{208}\mbox{Pb} +\ ^{208}\mbox{Pb} at $E_{lab} = 160$ AGeV. Theoretical predictions are also given for proton rapidity distribution in ^{197}\mbox{Au} +\ ^{197}\mbox{Au} at $\sqrt{s} = 200$ AGeV (BNL-RHIC). We predict that the nearly baryon free region will appear in the midrapidity region and the rapidity shift is $\langle \Delta y \rangle = 2.22$.Comment: 40 pages, 16 Postscript figures, submitted to Phys. Rev.

Control of critical coupling in a ring resonator fiber configuration: application to wavelength-selective switching, modulation, amplification, and oscillation

By controlling the internal loss of a ring resonator near critical coupling, we demonstrate control of the transmitted power in a fiber that is coupled to the resonator. We also demonstrate wavelength-selective optical amplification and oscillation

Sparticle masses in deflected mirage mediation

We discuss the sparticle mass patterns that can be realized in deflected mirage mediation scenario of supersymmetry breaking, in which the moduli, anomaly, and gauge mediations all contribute to the MSSM soft parameters. Analytic expression of low energy soft parameters and also the sfermion mass sum rules are derived, which can be used to interpret the experimentally measured sparticle masses within the framework of the most general mixed moduli-gauge-anomaly mediation. Phenomenological aspects of some specific examples are also discussed.Comment: 43 pages, 17 figures, references adde

The Gaugino Code

Gauginos might play a crucial role in the search for supersymmetry at the Large Hadron Collider (LHC). Mass predictions for gauginos are rather robust and often related to the values of the gauge couplings. We analyse the ratios of gaugino masses in the LHC energy range for various schemes of supersymmetry breakdown and mediation. Three distinct mass patterns emerge.Comment: 42 pages, Latex; a discussion of deflected anomaly mediation added, references adde

Two-Electron Linear Intersubband Light Absorption in a Biased Quantum Well

We point out a novel manifestation of many-body correlations in the linear optical response of electrons confined in a quantum well. Namely, we demonstrate that along with conventional absorption peak at frequency close to intersubband energy, there exists an additional peak at double frequency. This new peak is solely due to electron-electron interactions, and can be understood as excitation of two electrons by a single photon. The actual peak lineshape is comprised of a sharp feature, due to excitation of pairs of intersubband plasmons, on top of a broader band due to absorption by two single-particle excitations. The two-plasmon contribution allows to infer intersubband plasmon dispersion from linear absorption experiments.Comment: 4 pages, 3 figures; published versio

A method to find quantum noiseless subsystems

We develop a structure theory for decoherence-free subspaces and noiseless subsystems that applies to arbitrary (not necessarily unital) quantum operations. The theory can be alternatively phrased in terms of the superoperator perspective, or the algebraic noise commutant formalism. As an application, we propose a method for finding all such subspaces and subsystems for arbitrary quantum operations. We suggest that this work brings the fundamental passive technique for error correction in quantum computing an important step closer to practical realization.Comment: 5 pages, to appear in Physical Review Letter

Affine maps of density matrices

For quantum systems described by finite matrices, linear and affine maps of matrices are shown to provide equivalent descriptions of evolution of density matrices for a subsystem caused by unitary Hamiltonian evolution in a larger system; an affine map can be replaced by a linear map, and a linear map can be replaced by an affine map. There may be significant advantage in using an affine map. The linear map is generally not completely positive, but the linear part of an equivalent affine map can be chosen to be completely positive and related in the simplest possible way to the unitary Hamiltonian evolution in the larger system.Comment: 4 pages, title changed, sentence added, reference update

Current responses and voltage fluctuations in Josephson-junction systems

We consider arrays of Josephson junctions as well as single junctions in both the classical and quantum-mechanical regimes, and examine the generalized (frequency-dependent) resistance, which describes the dynamic responses of such Josephson-junction systems to external currents. It is shown that the generalized resistance and the power spectrum of voltage fluctuations are related via the fluctuation-dissipation theorem. Implications of the obtained relations are also discussed in various experimental situations.Comment: 4 pages, To appear in Europhys. Let