X Y Z particles at BABAR

This paper intends to shortly summarize the recent results on Spectroscopy, published from the BABAR Collaboration. The BABAR experiment is a B-factory, at SLAC, where asymmetric energy beams of electron-positron are accelerated and collide at the energy in the center of mass of T（4S）. In 9 years of data taking, BABAR had collected 433 fb^-1 equivalent luminosity on-peak-data at the T（4S） energy, 30 fb^-1 data at the T（3S） energy, 15 fb^-1 data at the T（2S） energy, and a scan around T（4S） was done, collecting 25 pb^-1 every 5 MeV. Thanks to the high luminosity achieved, it is possible to perform high precision measurements, and spectroscopy studies. An update on the measurement of the state X（3872） will be given, as final result published by using the whole dataset available. Then, a new preliminary Y（4260） measurement is reported, and the study of the invariant mass J/ψπ^＋π^- in ISR events is shown, where no evidence of the state Y（4050） is highlighted. As conclusion, the results on the angular distribution analysis performed on the state Z（4430） are reported.     

X Y Z particles at BABAR

This paper intends to shortly summarize the recent results on Spectroscopy,published from the BABAR Collaboration.The BABAR experiment is a B-factory,at SLAC,where asymmetric energy beams of electron-positron are accelerated and collide at the energy in the center of mass of Υ(4S).In 9 years of data taking,BABAR had collected 433 fb-1 equivalent luminosity on-peak-data at the Υ(4S) energy,30 fb?1 data at the Υ(3S) energy,15 fb-1 data at the Υ(2S) energy,and a scan around Υ(4S) was done,collecting 25 pb-1 every 5 MeV.Thanks to the high luminosity achieved,it is possible to perform high precision measurements,and spectroscopy studies.An update on the measurement of the state X(3872) will be given,as final result published by using the whole dataset available.Then,a new preliminary Y(4260) measurement is reported,and the study of the invariant mass J/ψπ+π-in ISR events is shown,where no evidence of the state Y(4050) is highlighted.As conclusion,the results on the angular distribution analysis performed on the state Z(4430) are reported.     

Super-sensitivity measurement of tiny Doppler frequency shifts based on parametric amplification and squeezed vacuum state

The precision measurement of Doppler frequency shifts is of great significance for improving the precision of speed measurement. This paper proposes a precision measurement scheme of tiny Doppler shifts by a parametric amplification process and squeezed vacuum state. This scheme takes a parametric amplification process and squeezed vacuum state into a detection system, so that the measurement precision of tiny Doppler shifts can exceed the Cram′er–Rao bound of coherent light. Simultaneously, a simulation study is carried out on the theoretical basis, and the following results are obtained: for the signal light of Gaussian mode, when the amplification factor g = 1 and the squeezed factor r = 0.5, the measurement error of Doppler frequency shifts is 14.4% of the Cramer–Rao bound of the coherent light in our system. At the same time,when the local light mode and squeezed vacuum state mode are optimized, the measurement precision of this scheme can be further improved by ■ times, where n is the mode-order of the signal light.     

Status and accuracy of the Monte Carlo generators for luminosity measurements

The status and accuracy of the precision Monte Carlo generators used for luminosity measurements at flavour factories is reviewed. It is shown that, thanks to a considerable, long-term effort in tuned comparisons between the predictions of independent programs, as well as in the validation of the generators against the presently available calculations of the next-to-next-to-leading order QED corrections to Bhabha scattering, the theoretical accuracy reached by the most precise tools is of about one per mille. This error estimate is valid for realistic experimental cuts, appears to be quite robust and is already sufficient for very accurate luminosity measurements. However, recent progress and possible advances to further improve it are also discussed.     

Research on calibration method in lab of direct solar channels of Sun photometer

We develop a new calibration method in lab by measuring the absolute spectral irradiance responsivity of Sun photometer sun channel. The absolute power responsivity of Sun photometer is obtained when a white laser double monochromator system serve as a source, and a standard transfer detector calibrated against cryogenic absolute radiometer is assembled to measure the absolute power of laser beam. The effective area of aperture is measured through laser raster scanning method, and the relative spectral irradiance responsivity of the corresponding channel is obtained by using tungsten-halogen lamps double monoehromator system. On the basis of the above results, the top of the atmosphere responsive constants V0 （500, 675, and 870 nm） are obtained by integration with extraterrestrial solar spectral irradiance data. Comparing the calibration results with that of CIMEL, France in November 2011, the relative differences are 4.38%, 2.23%, and 2.45%, respectively. The calibration uncertainty reaches to 2.048×10^-2, which shows a remarkable consistency with the Langley plot method. Further, our scheme can overcome the limits of space and atmospheric conditions which are only available at a high-altitude calibration site in particular date. The advantages lie in not only shortening the experiment period but also being of high precision. This new scheme definitely plays an important role in supporting the current and future sun photometry calibration activities which are significant to earth observation.     

Efficient Scheme for Greenberger-Horne-Zeilinger State and Cluster State with Trapped Ions

We propose a scheme to generate the Greenberger-Horne-Zeilinger （GHZ） states and the cluster states of many trapped ions. In the scheme, the ion is illuminated by a single laser tuned to the first lower vibrational sideband. The scheme only requires resonant interactions. Thus the scheme is very simple and the quantum dynamics operation can be realized at a high speed, which is important in view of decoherence.     

Coherent structures in wall turbulence and mechanism for drag reduction control

Herein is introduced the mechanism for active control influencing the generation of the near-wall streamwise vortices,which are closely related to the production of high skin friction in wall-bounded turbulent flows.A new opposition control scheme with adjusting control amplitude is proposed and evaluated in turbulent channel flow by direct numerical simulations.The maximum drag reduction rate can be greatly enhanced by the strengthened control.Finally the effectiveness of the control to the coherent structures at high Reynolds numbers is investigated by using a linear transient growth model.     

The method to evaluate the position error in graphic positioning technology

In the measurement of automobile body-in-white, it has been widely studied to position the twodimensional (2D) visual sensors with high precision. In this paper a graphic positioning method is proposed, a hollow tetrahedron is used for a positioning target to replace all the edges of a standard automobile body. A 2D visual sensor can be positioned through adjusting two triangles to be superposed on a screen of the computer, so it is very important to evaluate the superposition precision of the two triangles. Several methods are discussed and the least square method is adopted at last, it makes the adjustment more easy and intuitive with high precision.     

Extraction of the CKM phase γ from the charmless two-body B meson decays

Using all experimentally measured charmless B → PP, PV decay modes, where P(V) denotes a light pseudoscalar(vector) meson, we extract the CKM angle γ by a global fit. All hadronic parameters are determined from the experimental data, such that the approach is least model dependent. The contributions of the various decay modes are classified by the topological weak Feynman diagram amplitudes, which are determined by the global fit.To improve the precision of the approach, we consider the flavor SU(3) breaking effects of the topological diagram amplitudes of the decay modes by including the form factors and decay constants. The fit result for the CKM angle γ is( 69.8 ± 2.1 ± 0.9)°. It is consistent with the current world average values but has a smaller uncertainty.     

An efficient chaotic source coding scheme with variable-length blocks

An efficient chaotic source coding scheme operating on variable-length blocks is proposed.With the source message represented by a trajectory in the state space of a chaotic system,data compression is achieved when the dynamical system is adapted to the probability distribution of the source symbols.For infinite-precision computation,the theoretical compression performance of this chaotic coding approach attains that of optimal entropy coding.In finite-precision implementation,it can be realized by encoding variable-length blocks using a piecewise linear chaotic map within the precision of register length.In the decoding process,the bit shift in the register can track the synchronization of the initial value and the corresponding block.Therefore,all the variable-length blocks are decoded correctly.Simulation results show that the proposed scheme performs well with high efficiency and minor compression loss when compared with traditional entropy coding.     

Camera calibration approach using circle-square-combined target

Calibrating a small field camera is a challenging task because the traditional target with visible feature points that fit the limited space is difficult and costly to manufacture.We demonstrate a novel combined target used in camera calibration.The tangent points supplied by one circle located at the center of a square are used as invisible features,and the perspective projection invariance is proved.Both visible and invisible features extracted by the proposed feature extraction algorithm are used to solve the calibration. The target supplies a sufficient number of feature points to satisfy the requirements of calibration within a limited space.Experiments show that the approach can achieve high robustness and considerable accuracy. This approach has potential for computer vision applications particularly in small fields of view.     

Research in absolute calibration of single photon detectors by means of correlated photons

There are two general methods in radiometric calibration of detectors, one is based on radiation sources and the other based on detectors. Because the two methods need to establish a primary standard of high precision and a transfer chain, precision of the standard will be reduced by extension of the chain. A new calibration method of detectors can be realized by using correlated photons generated in spontaneous parametric down-conversion (SPDC) effect of nonlinear crystal, without needing transfer chain. Using 351.1-nm output of a tunable laser to pump β-barium borate (BBO) crystal, an absolute calibration experimental system of single photon detectors based on correlated photons is performed. The quantum efficiency of photomultiplier (PMT) at 702.2 nm is measured by the setup. Advantages of this method over traditional methods are also pointed out by comparison.     

Precision Calculations of Atomic Polarizabilities: A Relevant Physical Quantity in Modern Atomic Frequency Standard

Electric dipole polarizabilities of atoms are very important in many different physical applications, such as the precision atomic frequency standard. Calculations of these properties are very important and challenging. We propose a calculation strategy to calculate the frequency dependent dipole polarizabilities with high precision variationally by using a set of high quality orbital bases where the electron correlations can be taken into account adequately. The static polarizabilitiez of the ground state of Na are calculated accurately by such a method and can be compared with precision experiment measurement directly. The calculation result is in excellent agreement with the available experimental measurements within about 0.1~, which demonstrates the validity of our strategy. Our calculation strategy has a wide usage, not only in polarizibilies, but also in other fields such as theoretical treatment of electron-atom scattering processes. Using the same orbital bases, we carry out precision calculation of Na- affinities. Our calculated affinity is in excellent agreement with precision laser spectroscopy measurements within 0. 1%.     

Quantum logic gates operation using SQUID qubits in bimodal cavity

We present a scheme to realize the basic two-qubit logic gates such as the quantum phase gate and SWAP gate using a detuned microwave cavity interacting with three-level superconducting-quantum-interference-device (SQUID) qubit(s), by placing SQUID(s) in a two-mode microwave cavity and using adiabatic passage methods. In this scheme, the two logical states of the qubit are represented by the two lowest levels of the SQUID, and the cavity fields are treated as quantized. Compared with the previous method, the complex procedures of adjusting the level spacing of the SQUID and applying the resonant microwave pulse to the SQUID to create transformation are not required. Based on superconducting device with relatively long decoherence time and simplified operation procedure, the gates operate at a high speed, which is important in view of decoherence.     

Compensation for booster leakage field in the Duke storage ring

The High Intensity Gamma-ray Source(HIGS) at Duke University is an accelerator-driven Compton gamma-ray source, providing high flux gamma-ray beam from 1 MeV to 100 MeV for photo-nuclear physics research.The HIGS facility operates three accelerators, a linac pre-injector(0.16 GeV), a booster injector(0.16—1.2 GeV),and an electron storage ring(0.24—1.2 GeV). Because of the proximity of the booster injector to the storage ring, the magnetic field of the booster dipoles close to the ring can significantly alter the closed orbit in the storage ring being operated in the low energy region. This type of orbit distortion can be a problem for certain precision experiments which demand a high degree of energy consistency of the gamma-ray beam. This energy consistency can be achieved by maintaining consistent aiming of the gamma-ray beam, and therefore a steady electron beam orbit and angle at the Compton collision point. To overcome the booster leakage field problem, we have developed an orbit compensation scheme. This scheme is developed using two fast orbit correctors and implemented as a feedforward which is operated transparently together with the slow orbit feedback system. In this paper, we will describe the development of this leakage field compensation scheme, and report the measurement results, which demonstrate the effectiveness of the scheme.     

Spatial characteristics of nanosecond pulsed micro-discharges in atmospheric pressure He/H2O mixture by optical emission spectroscopy

Atmospheric pressure micro-discharges in helium gas with a mixture of 0.5%water vapor between two pin electrodes are generated with nanosecond overvoltage pulses.The temporal and spatial characteristics of the discharges are investigated by means of time-resolved imaging and optical emission spectroscopy with respect to the discharge morphology,gas temperature,electron density,and excited species.The evolution of micro-discharges is captured by intensified CCD camera and electrical properties.The gas temperature is diagnosed by a two-temperature fit to the ro-vibrational OH(A²Σ⁺–X^П(2),0–0)emission band and is found to remain low at 425 K during the discharge pulses.The profile of electron density performed by the Stark broadening of Ha 656.1-nm and He I 667.8-nm lines is uniform across the discharge gap at the initial of discharge and reaches as high as 10²³m^-3.The excited species of He,OH,and H show different spatio-temporal behaviors from each other by the measurement of their emission intensities,which are discussed qualitatively in regard of their plasma kinetics.     

Quantum Key Distribution Scheme with High Efficiency

Based on entanglement swapping, a quantum key distribution （QKD） scheme is proposed. In this scheme, the secret keys are formed by comparing initial Bell states and outcomes of entanglement swapping. Moreover, all initial Bell states prepared by Alice and Bob are completely arbitrary. As the classical information exchanged between two parties is very little, this QKD scheme has a high efficiency. In addition, in order to prevent eavesdropping, decoy particles are used.     

Invariants-based shortcuts for fast generating Greenberger-Horne-Zeilinger state among three superconducting qubits

As one of the most promising candidates for implementing quantum computers, superconducting qubits(SQs) are adopted for fast generating the Greenberger–Horne–Zeilinger(GHZ) state by using invariants-based shortcuts. Three SQs are separated and connected by two coplanar waveguide resonators(CPWRs) capacitively. The complicated system is skillfully simplified to a three-state system, and a GHZ state among three SQs is fast generated with a very high fidelity and simple driving pulses. Numerical simulations indicate the scheme is insensitive to parameter deviations. Besides, the robustness of the scheme against decoherence is discussed in detail.     

Specific Heat of Rhombohedral Polymeric C60 in Temperature Range 300--2K

Polymerization of C60 is realized under high temperature and high pressure. X-ray diffraction reveals a rhombohedral lattice structure in the product, and solid-state ^13C nuclear magnetic resonance spectroscopy confirms the formation of sp^3 bonds between C60 molecules. Specific heat is then measured over the temperature range of 300-2 K. It is found that its specific heat values are significantly less than those in fullerite within the region of 80-2K, and this huge reduction is attributed to the suppression of intermolecular librational modes in polymerized C60. An excellent fit to the experimental data over the entire temperature range is provided by a model, which needs to include only three-dimensional and two-dimensional translational modes in various contributions at different temperatures.     

Multi-wavelength pulse generation using flattop optical frequency comb and arrayed waveguide grating

A scheme of multi-wavelength pulse generator using optical frequency comb and arrayed waveguide grating (AWG) is proposed and experimentally demonstrated. A flattop optical frequency comb is shaped into multiple narrowband Gaussian spectra by using an AWG which contains a number of Gaussian channels, and then multi-wavelength optical pulses are achieved. In the experiment, six wavelength pulses with full width at half-maximum (FWHM) of 14.6 ps at 10 GHz are obtained, and two wavelength-interleaved pulse trains at 20 GHz and four wavelength-interleaved pulse trains at 40 GHz are demonstrated by using the multi-wavelength optical pulses. This scheme has flexibility because the pulse width, the repetition rate, and time-interval can be readily controlled.