Optical switching by controlling the double-dark resonances in a N-tripod five-level atom

We have investigated the optical switching in a five-level atom in a novel configuration of electromagnetically induced transparency. This N-tripod type level scheme combines the attractive features of cross-phase modulation appearing in N-type atoms with the ability to slow light pulses associated with tripod atoms. The addition of a new driving field to the usual tripod configuration allows to control the double-dark resonances which appear in the four-level tripod system and thus enables to manipulate the probe absorption and dispersion properties. We have studied the temporal dynamics of two pulses, a probe pulse and a switch propagating pulse through the sample. In the presence of the switching field, a deep in the absorption at resonance due to one-photon electromagnetically induced transparency appears and the atomic system is transparent to the probe field, which propagates at a very small group velocity. By tuning the fields, one of the usual double-dark resonances appearing in tripod system can be controlled (Stark-shifted) and the medium, which is transparent in the absence of the control field, will become highly absorptive. The linear and cross-phase modulation susceptibilities have been calculated and we predict the possibility to realize two-photon switching and giant cross-phase modulation. Finally we address the question about the generation of an entangled coherent state and we show that the giant cross-phase modulation provided by this N-tripod atomic system can be used for realizing polarization quantum phase gates.     

Matching group velocity of bright and/or dark solitons via double-dark resonances

We propose a scheme which can generate group velocity matching bright and/or dark solitons in a four-level tripod configuration atomic system via double-dark resonances. It is shown that the linear absorption properties can be controlled by the controlling fields. For the nonlinear case, the optical soliton can form in the first and second electromagnetically induced transparency windows and their group velocities can be matched under the condition of equal half Rabi frequencies of the two controlling fields. We also show that adjusting the amplitude and group velocity of the soliton as well as the bright and dark solitons conversion can be realized.     

Photoproduction of ω-Mesons at ELSA and the role of azimuthal asymmetries

Measurements of ω photoproduction of the Crystal-Barrel/TAPS experiment at the ELSA accelerator of Bonn University are presented which used linearly polarized tagged photon beam from threshold to Eγ = 1700MeV. The azimuthal asymmetries ∑and ∑πindicate s-channel resonance contributions on top of the established t-channel exchange processes. These findings are further enhanced by a very first measurement of the G-asymmetry which, in addition to the polarized photon beam, also requires a longitudinally polarized proton target. An intuitive interpretation of the specific sensitivity of the azimuthal asymmetries to the reaction mechanisms involved is given.     

The N* physics program at Jefferson Lab

Recent measurements of nucleon resonance transition form factors with CLAS at Jefferson Lab are discussed. The new data confirm the assertion of the symmetric constituent quark model of the Roper as the first radial excitation of the nucleon. The data on high Q2 nπ＋ production better constrain the branching ratios liNK and [3Nn. For the first time, the longitudinal transition amplitude to the S11（1535） was extracted from the nπ＋ data. Also, new results on the transition amplitudes for the D13（1520） resonance are presented showing a rapid transition from helicity 3/2 dominance seen at the real photon point to helicty 1/2 dominance at higher Q2. I also discuss the status of the search for new excited nucleon states.     

Determination of Scaling Parameter and Dynamical Resonances in Complex-Rotated Hamiltonian Ⅱ： Numerical Analysis

This paper is concerned with the determination of a unique scaling parameter in complex scaling analysis and with accurate calculation of dynamics resonances. In the preceding paper we have presented a theoretical analysis and provided a formalism for dynamical resonance calculations. In this paper we present accurate numerical results for two non-trivial dynamical processes, namely, models of diatomic molecular predissociation and of barrier potential scattering for resonances. The results presented in this paper confirm our theoretical analysis, remove a theoretical ambiguity on determination of the complex scaling parameter, and provide an improved understanding for dynamical resonance calculations in rigged Hilbert space.     

Complementary studies on N＊ from e＋e-, pp and pp collisions

Complementary to the conventional experimental studies on N＊ from πN and γ（＊）N reactions, the e＋e-, pp and pp collisions can give novel insights into these N＊ resonances. While the e＋e- collisions through production and decay of vector charmonium ψ provide a nice isospin filter for a simultaneously study of N＊, △＊, ∧＊, ∑＊ and 2＊, the pp collisions should be the best place for producing those △＊＋＋ with large coupling to p＋p though pp →nA＊＋＋ reaction, and the pp collisions should be the best place for looking for those N＊ with large coupling to σN.     

Single π0electro-production in the resonance region with CLAS＊

We report the analysis status of single π0electroproduction in the resonance region to study the electromagnetic excitation of the nucleon resonances. The study is aimed at understanding of the internal structure and dynamics of the nucleon. The experiment was performed using an unpolarized cryogenic hydrogen target and 2.0 and 5.8 GeV polarized electron beam during the ele and e1-6 run periods with CLAS at Jefferson Lab. The new measurements will produce a data base with high statistics and large kinematic coverage for the hadronic invariant mass （W） up to 2.0 CeV in the momentum transfer （Q2） range of 0.3--6.0 GeV2. Preliminary results will be presented and compared with the various model calculations.     

An explanation of the△D35（1930） as a ρ△ bound state

Constituent quark models based on two-body potentials systematically overpredict the mass of △D35 （1930）. A possible solution to this problem comes out from the application of a schematic hybrid model, containing three-quark as well as meson-baryon components, to the light-quark baryon spectrum. The △D35（1930） and its partners △D33（1940） and△s31（1900） are found to contain a significant pA component. Then, through the use of the hidden gauge formalism, it is shown that these resonances can be dynamically generated from the ρ-△ interaction. In particular △D35（1930） can be interpreted as being essentially a ρ△ bound state. This interpretation suggests that the inclusion of ρ△ as an effective inelastic channel in data analyses could improve the extraction and identification of the resonance.     

Recent results on nucleon resonance electrocouplings from the studies of π＋π-p electroproduction with the CLAS detector

Recent results on nucleon resonance studies in π＋π-p electro- production off protons with the CLAS detector are presented. The analysis of CLAS data allowed us to determine all essential contributiag mechanisms, providing a credible separation between resonant and non-resonant parts of the cross sections in a wide kinematical area of invariant masses of the final hadronic system 1.3 〈 W 〈 1.8 GeV and photon virtutualities 0.2 〈 Q2 〈 1.5 GeV2. Electrocouplings of several excited proton states with masses less than 1.8 GeV were obtained for the first time from the analysis of π＋π-p exclusive electroproduction channel.     

Determination of Scaling Parameter and Dynamical Resonances in Complex-Rotated Hamiltonian Ⅰ： Theory

In this paper we present a theoretical analysis on the determination of the scaling parameter in the complex-rotated Hamiltonian, which has served as a basis for successful applications of the rigged Hilbert space theory for resonances. Based on the complex energy eigenvalue, E（θ） = ER（θ） - iГ（θ）/2, as a function of the scaling parameter θ, we find that for potential barrier scattering, the condition dГ（θI）/dθ = 0 uniquely determines the scaling parameter 8. The condition d ER （θR）/ dθ = 0 is merely a consequence of the Virial theorem and θI =θR is not a necessary condition for a resonance state. We also provide a harmonic approximation formMism for resonances in scattering over a potential barrier.     

Relativistic Continuum Random Phase Approximation and Applications I. Formalism

A fully consistent relativistic continuum random phase approximation （RCRPA） is constructed in terms of the Green＇s function technique. In this method the contribution of the continuum spectrum to nuclear excitations is treated exactly by the single particle Green＇s function, which includes also the negative states in the Dirac sea in the no sea approximation. The theoretical formalism of RCRPA and numerical details are presented. The single particle Green＇s function is calculated numerically by a proper product of regular and irregular solutions of the Dirac equation. The numerical details and the formalism of RCRPA in the momentum representation are presented.     

Strong and electromagnetic J/ψ and ψ（2S） decays into pion and kaon pairs

We discuss interference effects important for the form factors extraction in the vicinity of J/ψ and ψ（2S） resonances in combination with resonance parameters determination. The implementation to the Monte Carlo event generator PHOKHARA of the J/ψ and ψ（2S） contributions to the muon, pion and kaon pairs production associated with a photon at next-to-leading order is also described.     

Dynamically generated resonances

In this talk I report on recent work related to the dynamical generation of baryonic resonances, some made up from pseudoscalar meson-baryon, others from vector meson-baryon and a third type from two meson-one baryon systems. We can establish a correspondence with known baryonic resonances, reinforcing conclusions previously drawn and bringing new light on the nature of some baryonic resonances of higher mass.     

Dynamically generated resonances from the vector octet-baryon decuplet interaction and their radiative decays into $\gamma$-baryon decuplet

The dynarnically generated resonances from vector meson-baryon decuplet are studied using La- grangians of the hidden gauge theory for vector interactions. One shows that some of the generated states can be associated with some known baryon resonances in the PDG data, while others are predictions for new states. Furthermore, we calculate the radiative decay widths of these resonances into a photon and a baryon decuplet.     

Charmed baryon heavy-quark resonances with symmetry

We study charmed baryon resonances that are generated dynamically from a coupled-channel unitary approach that implements heavy-quark symmetry. Some states can already be identified with experimental observations, such as Ac（2595）, Ac（2660）, Ec（2902） or Ac（2941）, while others need a compilation of more experimental data as well as an extension of the model to include higher order contributions. We also compare our model to previous SU（4） schemes.     

Multi-wavelength measurements of aerosol optical absorption coefficients using a photoacoustic spectrometer

The atmospheric aerosol absorption capacity is a critical parameter determining its direct and indirect effects on cli- mate. Accurate measurement is highly desired for the study of the radiative budget of the Earth. A multi-wavelength （405 rim, 532 nm, 780 nm） aerosol absorption meter based on photoacoustic spectroscopy （PAS） invovling a single cylin- drical acoustic resonator is developed for measuring the aerosol optical absorption coefficients （OACs）. A sensitivity of 1.3 Mm-l （at 532 nm） is demonstrated. The aerosol absorption meter is successfully tested through measuring the OACs of atmospheric nigrosin and ambient aerosols in the suburbs of Hefei city. The absorption cross section and absorption Angstrom exponent （AAE） for ambient aerosol are determined for characterizing the component of the ambient aerosol.     

A proposed U.S./China theoretical/experimental collaborative effort on baryon resonance extraction

In this paper we discuss the reasons for our work towards establishing a new collaboration between Jefferson Lab （JLab） and the Institute of High Energy Physics （IHEP） in Beijing. We seek to combine experimentalists and theorists into a dedicated group focused on better understanding the current and future data from JLab and from the Beijing Electron Positron Collider （BEPC）. Recent JLab results on the extraction of single- and double-polarization observables in both the lπ- and 2π-channel show their high sensitivity to small production amplitudes and therefore their importance for the extraction of resonance parameters. The Beijing Electron Spectrometer （BES） at the BEPC has collected high statistics data on J/ψ production. Its decay into baryon-antibaryon channels offers a unique and complementary way of probing nucleon resonances. The CEBAF Large Acceptance Spectrometer, CLAS, has access to N＊ form factors at high Q2 which is advantageous for the study of dynamical properties of nucleon resonances, while the low-background BES results will be able to provide guidance for the search for less-dominant excited states at JLab. Moreover, with the recently approved experimental proposal Nucleon Resonance Studies with CLAS12 and the high-quality data streaming from BES-Ⅲand CLAS, the time has come for forging a new Trans-Pacific collaboration of theorists and experimentalists on NSTAR physics.     

Doppler-shifted cyclotron resonance in thin metal films

The velocities of electrons contained in a thin slab are quantized because the component of momentum transverse to the slab faces is quantized. For a free electron gas the transverse velocity is given by |v_H| = l(/m) (π/d) where l = 1, 2, 3, …. If a magnetic field is applied normal to the slab, the wave number and frequency dependent conductivity consists of a series of resonant terms. The resonances occur at the Doppler-shifted cyclotron resonance frequencies |ω_c| = ω ± p(/m) (π/d)² where l = 1, 2, 3, …. It is shown that these resonances in the conductivity result in an absorption in pure thin films at low temperatures which is periodic in magnetic field. The semi-classical expression for the absorption is in substantial agreement with the corresponding quantum calculation, and has the virtue that it may be readily extended to non-spherical Fermi surfaces.     

Intensity and composition-dependent sign reversal of non-linearity in TiO2/CeO2 nanocomposites

CeO2/TiO2 composite nanoparticles with different Ce/Ti molar ratios have been successfully synthesized via sol-gel method. It was found that the band gap of the nanocomposite is tunable by varying Ce/Ti content. The nonlinear response of the sample was studied by using the nanosecond laser pulses from a Q switched Nd：Yag laser employing the Z-scan method. Open aperture Z-scan experiment revealed that with the increase in the CeO2 amount in the nanocomposite, the non-linearity of the composite increases, and it was assumed that this could be due to the modification of TiO2 dipole symmetry by the addition of CeO2. Closed aperture Z-scan experiment showed that when the CeO2 amount increases, positive nonlinear refraction decreases, and this could be attributed to the increase in the two photon absorption which subsequently suppresses the nonlinear refraction.