2007 Vol. 31, No. 4
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Abstract:
Recently many theoretical calculations have been made for the cross section of e+e－→τ+τ－ near the threshold, the accuracy of which is up to 10－4. Based on one of the calculations, the e μ-contained final state data are refitted by utilizing the technique once adopted by BES collaboration for τ mass measurement. The systematic uncertainties are analyzed again and the final result of τ mass is 1776.98+0.44+0.12－0.51－0.13MeV.
Recently many theoretical calculations have been made for the cross section of e+e－→τ+τ－ near the threshold, the accuracy of which is up to 10－4. Based on one of the calculations, the e μ-contained final state data are refitted by utilizing the technique once adopted by BES collaboration for τ mass measurement. The systematic uncertainties are analyzed again and the final result of τ mass is 1776.98+0.44+0.12－0.51－0.13MeV.
Abstract:
The recent measurements of the Bs mass difference Δ Ms by the CDF and DO collaborations are roughly consistent with the Standard Model predictions, therefore, these measurements will afford an opportunity to constrain new physics scenarios beyond the Standard Model. We consider the impact of the R-parity violating supersymmetry in the B0s—B0s mixing, and use the latest experimental results of ΔMs to constrain the size of the R-parity violating tree level couplings in the B0s—B0s mixing. Then, using the constrained RPV parameter space from ΔMs, we show the R-parity violating effects on the Bs width difference ΔΓs.
The recent measurements of the Bs mass difference Δ Ms by the CDF and DO collaborations are roughly consistent with the Standard Model predictions, therefore, these measurements will afford an opportunity to constrain new physics scenarios beyond the Standard Model. We consider the impact of the R-parity violating supersymmetry in the B0s—B0s mixing, and use the latest experimental results of ΔMs to constrain the size of the R-parity violating tree level couplings in the B0s—B0s mixing. Then, using the constrained RPV parameter space from ΔMs, we show the R-parity violating effects on the Bs width difference ΔΓs.
Abstract:
A nonlinear theoretical model of interaction between q-deformed light field and a cascade three-level atom has been constructed. The formal solution of Schr\"{o}dinger equation in the interactive epresentation and the expectation value of the interaction on such a state are obtained. Then, the influence of q deformation on photon antibunching effects is studied by numerical calculation. The results show that the more q deviates from 1, the stronger controllability to antibunching effects the q deformation has. It reflects the effect of the nonlinear behavior of q deformation on quantum coherence and quantum properties. When q→1, the theory reduces to the normal linear theory.
A nonlinear theoretical model of interaction between q-deformed light field and a cascade three-level atom has been constructed. The formal solution of Schr\"{o}dinger equation in the interactive epresentation and the expectation value of the interaction on such a state are obtained. Then, the influence of q deformation on photon antibunching effects is studied by numerical calculation. The results show that the more q deviates from 1, the stronger controllability to antibunching effects the q deformation has. It reflects the effect of the nonlinear behavior of q deformation on quantum coherence and quantum properties. When q→1, the theory reduces to the normal linear theory.
Abstract:
A solar cosmic rays Ground Level Enhancement(GLE) event associated with a X7.1/2b solar flare in 2005 January 20 was observed by the Yangbajing solar neutron telescope(SNT) and neutron monitor(NM), located at Yangbajing Tibet(90.53°E, 30.11°N, 4310m a.s.l) with the highest vertical geomagnetic cut-off rigidity of 14.1GV in NM network. The statistical significance of the counting rate enhancement recorded by solar neutron telescope in >40MeV channel was 3.7σ in the time window of 07:00—07:05UT and 6.0σ in the time window of 07:00—07:20UT, respectively. The onset time of 06:51—06:52UT for this GLE event was clearly observed by the Yangbajing NM. Our observation indicates that solar protons have been accelerated up to energies of >10GeV during this solar event.
A solar cosmic rays Ground Level Enhancement(GLE) event associated with a X7.1/2b solar flare in 2005 January 20 was observed by the Yangbajing solar neutron telescope(SNT) and neutron monitor(NM), located at Yangbajing Tibet(90.53°E, 30.11°N, 4310m a.s.l) with the highest vertical geomagnetic cut-off rigidity of 14.1GV in NM network. The statistical significance of the counting rate enhancement recorded by solar neutron telescope in >40MeV channel was 3.7σ in the time window of 07:00—07:05UT and 6.0σ in the time window of 07:00—07:20UT, respectively. The onset time of 06:51—06:52UT for this GLE event was clearly observed by the Yangbajing NM. Our observation indicates that solar protons have been accelerated up to energies of >10GeV during this solar event.
Abstract:
In the RMF approach, considering the contributions of the σ* and φ mesons and the hyperons in the baryon octet {N,P,Λ,∑－,∑0,∑+,Ξ－,Ξ0}, the properties of neutron star matter have been investigated. It is found that with the contributions of the σ* and φ mesons, the critical baryon density of hyperon appearance decreases, the number of hyperons increases, the transition density ρ0H of hyperon stars decreases, the equation of state turns soft, the maximum mass of neutron star decreases and the corresponding radius increases, the central density, the central energy density and the central pressure are all reduced.
In the RMF approach, considering the contributions of the σ* and φ mesons and the hyperons in the baryon octet {N,P,Λ,∑－,∑0,∑+,Ξ－,Ξ0}, the properties of neutron star matter have been investigated. It is found that with the contributions of the σ* and φ mesons, the critical baryon density of hyperon appearance decreases, the number of hyperons increases, the transition density ρ0H of hyperon stars decreases, the equation of state turns soft, the maximum mass of neutron star decreases and the corresponding radius increases, the central density, the central energy density and the central pressure are all reduced.
Abstract:
The reduced velocity correlation functions of the Intermediate Mass Fragments (IMFs) were measured in the reactions of 36Ar+112,124Sn at 35MeV/u. The anti-correlation at small reduced velocities is more pronounced in 36Ar+124Sn system than that in 36Ar+112Sn system. The difference of the correlation functions between the two reactions is mainly contributed by the particle pairs with high momenta. A three-body Coulomb repulsive trajectory code (MENEKA) is employed to calculate the emission time scale of IMFs for the both systems. The time scale is 150fm/c in the 36Ar+112Sn system and 120fm/c in the 36Ar+124Sn system, respectively. A calculation based on an Isospin dependence Quantum Molecular Dynamics code (IQMD) reveals that the emission time spectrum of IMFs is shifted slightly leftwards in 36Ar+124Sn compared with that in the 36Ar+112Sn system, indicating a shorter emission time scale. Correspondingly, the central density of the hot nuclei decreases faster in 36Ar+124Sn than in 36Ar+112Sn.
The reduced velocity correlation functions of the Intermediate Mass Fragments (IMFs) were measured in the reactions of 36Ar+112,124Sn at 35MeV/u. The anti-correlation at small reduced velocities is more pronounced in 36Ar+124Sn system than that in 36Ar+112Sn system. The difference of the correlation functions between the two reactions is mainly contributed by the particle pairs with high momenta. A three-body Coulomb repulsive trajectory code (MENEKA) is employed to calculate the emission time scale of IMFs for the both systems. The time scale is 150fm/c in the 36Ar+112Sn system and 120fm/c in the 36Ar+124Sn system, respectively. A calculation based on an Isospin dependence Quantum Molecular Dynamics code (IQMD) reveals that the emission time spectrum of IMFs is shifted slightly leftwards in 36Ar+124Sn compared with that in the 36Ar+112Sn system, indicating a shorter emission time scale. Correspondingly, the central density of the hot nuclei decreases faster in 36Ar+124Sn than in 36Ar+112Sn.
Abstract:
High-spin states in 139Ce have been populated using the 130Te(12C,3n) reaction at beam energy of 50MeV. The level scheme of 139Ce has been revised and extended greatly up to E=5765.0keV. The level structure of 139Ce shows typical characteristics of spherical nucleus, and the high-spin states were formed by the excitations of valence nucleons. Energies of the yrast and near yrast high-spin states in 139Ce have been calculated by the empirical shell model, and the multi-quasiparticle nature of high-spin excited states has been discussed.
High-spin states in 139Ce have been populated using the 130Te(12C,3n) reaction at beam energy of 50MeV. The level scheme of 139Ce has been revised and extended greatly up to E=5765.0keV. The level structure of 139Ce shows typical characteristics of spherical nucleus, and the high-spin states were formed by the excitations of valence nucleons. Energies of the yrast and near yrast high-spin states in 139Ce have been calculated by the empirical shell model, and the multi-quasiparticle nature of high-spin excited states has been discussed.
Abstract:
The ground-state properties of N=8 and N=9 isotones are investigated in the framework of the single-particle shell model. The isospin effect on the average nuclear potential is taken into account by introducing an isospin-dependent term in the depth of the Woods-Saxon potential. The theoretical results of RMS radii and spin-parity values are in agreement with the experimental data. Especially, the level inversion between neutron levels 2s1/2 and 1d5/2 in N=9 isotones is reproduced. A detailed discussion on numerical results is given and one-neutron halos in the ground states of 14B and 15C are presented.
The ground-state properties of N=8 and N=9 isotones are investigated in the framework of the single-particle shell model. The isospin effect on the average nuclear potential is taken into account by introducing an isospin-dependent term in the depth of the Woods-Saxon potential. The theoretical results of RMS radii and spin-parity values are in agreement with the experimental data. Especially, the level inversion between neutron levels 2s1/2 and 1d5/2 in N=9 isotones is reproduced. A detailed discussion on numerical results is given and one-neutron halos in the ground states of 14B and 15C are presented.
Abstract:
The dinuclear system model has been further developed by introducing the barrier distribution function method in the process of heavy-ion capture and fusion to synthesize superheavy nuclei. The capture of two colliding nuclei, formation and de-excitation process of compound nucleus are decribed by using empirical coupled channel model, solving master equation numerically and statistical evaporation model, respectively. Within the framework of the di-nuclear system model, the fusion-evaporation excitation functions of the systems 48Ca(243Am, 3n—5n)288—286115 and 48Ca(248Cm, 3n—5n)293—291116 are calculated, which are used for synthesizing new superheavy nuclei at Dubna in recent years. Isotopic dependence of production cross sections with double magic nucleus 48Ca bombarding actinide targets U,Np,Pu,Am,Cm to synthesize superheavy nuclei with charged numbers Z=112—116 is analyzed systematically. Based on these analysis, the optimal projectile-target combination and the optimal excitation energy are proposed. It is shown that shell correction energy and neutron separation energy will play an important role on the isotopic dependence of production cross sections of superheavy nuclei.
The dinuclear system model has been further developed by introducing the barrier distribution function method in the process of heavy-ion capture and fusion to synthesize superheavy nuclei. The capture of two colliding nuclei, formation and de-excitation process of compound nucleus are decribed by using empirical coupled channel model, solving master equation numerically and statistical evaporation model, respectively. Within the framework of the di-nuclear system model, the fusion-evaporation excitation functions of the systems 48Ca(243Am, 3n—5n)288—286115 and 48Ca(248Cm, 3n—5n)293—291116 are calculated, which are used for synthesizing new superheavy nuclei at Dubna in recent years. Isotopic dependence of production cross sections with double magic nucleus 48Ca bombarding actinide targets U,Np,Pu,Am,Cm to synthesize superheavy nuclei with charged numbers Z=112—116 is analyzed systematically. Based on these analysis, the optimal projectile-target combination and the optimal excitation energy are proposed. It is shown that shell correction energy and neutron separation energy will play an important role on the isotopic dependence of production cross sections of superheavy nuclei.
Abstract:
A full-length prototype of the BESⅢ drift chamber was built. The experience gained on gas sealing, high voltage supply and front-end electronics installation should be greatly beneficial to the successful construction of the BESⅢ drift chamber. An on-detector test of the BESⅢ drift chamber electronics was carried out with the constructed prototype chamber. The noise performance, drift time and charge measurements, and electronics gains were examined specifically. The final test results indicate that the electronics have a good performance and can satisfy their design requirements.
A full-length prototype of the BESⅢ drift chamber was built. The experience gained on gas sealing, high voltage supply and front-end electronics installation should be greatly beneficial to the successful construction of the BESⅢ drift chamber. An on-detector test of the BESⅢ drift chamber electronics was carried out with the constructed prototype chamber. The noise performance, drift time and charge measurements, and electronics gains were examined specifically. The final test results indicate that the electronics have a good performance and can satisfy their design requirements.
Abstract:
Based on analysis of STAR-TOFr data from RHIC 62.4GeV Au+Au experiments, correlation between the MRPC signal amplitude (ADC) and the ionization energy loss (dE/dx) in working gas, for different particles (Pion, Kaon, Proton), are studied. Experimental results on characteristics of particle ionization and avalanche process in MRPC are presented. In order to further understand the working mechanism of MRPC, a Monte Carlo simulation procedure is carried out. Possible factors contributing to the performance of MRPC are discussed.
Based on analysis of STAR-TOFr data from RHIC 62.4GeV Au+Au experiments, correlation between the MRPC signal amplitude (ADC) and the ionization energy loss (dE/dx) in working gas, for different particles (Pion, Kaon, Proton), are studied. Experimental results on characteristics of particle ionization and avalanche process in MRPC are presented. In order to further understand the working mechanism of MRPC, a Monte Carlo simulation procedure is carried out. Possible factors contributing to the performance of MRPC are discussed.
Abstract:
A transverse field gas ionization chamber as ΔE detector at the Radioactive Ion Beam Line in Lanzhou (RIBLL) is described. A high detection efficiency and long plateau are achieved with the mixed gas Ar(80%)+CO2(20%). The energy resolution is 3.25% for 4.94MeV α particle. This ionization chamber has been tested in the experiment with 50MeV/u 58Ni bombarding Ta at RIBLL. All the fragments can be identified clearly by the ionization chamber.
A transverse field gas ionization chamber as ΔE detector at the Radioactive Ion Beam Line in Lanzhou (RIBLL) is described. A high detection efficiency and long plateau are achieved with the mixed gas Ar(80%)+CO2(20%). The energy resolution is 3.25% for 4.94MeV α particle. This ionization chamber has been tested in the experiment with 50MeV/u 58Ni bombarding Ta at RIBLL. All the fragments can be identified clearly by the ionization chamber.
Abstract:
The total dose response characteristics of the buried oxides (BOX) in separation by implanted oxygen (SIMOX) silicon-on-insulator (SOI) wafers have been improved by implanting silicon ion into the BOX layers. NMOS/SOI transistors with enclosed-gate structure fabricated in SIMOX wafers were exposed to 60Co γ-ray radiation. The total-dose radiation hardness of the BOX layers is characterized by the current voltage (I-V) measurements. The experimental results show that the implantation of silicon ion into the BOX layers can greatly reduce back channel threshold voltage shifts (ΔVth), which increase the BOX layer hardness to total-dose irradiation.
The total dose response characteristics of the buried oxides (BOX) in separation by implanted oxygen (SIMOX) silicon-on-insulator (SOI) wafers have been improved by implanting silicon ion into the BOX layers. NMOS/SOI transistors with enclosed-gate structure fabricated in SIMOX wafers were exposed to 60Co γ-ray radiation. The total-dose radiation hardness of the BOX layers is characterized by the current voltage (I-V) measurements. The experimental results show that the implantation of silicon ion into the BOX layers can greatly reduce back channel threshold voltage shifts (ΔVth), which increase the BOX layer hardness to total-dose irradiation.
Abstract:
In order to get high beam quality, a RF distribution system is required, with minimal phase drifts and errors in the BEPCⅡ linac. The additional installation of phase reference cables and monitoring equipments and stable RF distribution for BEPC linac are finished. The master oscillator is chosen to offer RF signal with low phase noise and a stable phase distribution system is built to deliver RF signal to each klystron. A phase and amplitude detector is constructed to measure the phase precisely and an IΦA unit is used for a phase shifter. Control software based on EPICS is used to connect all the units of the system, and a phasing method based on BPM is adopted to optimize the phase of each klystron. Now the phasing system is installed and tested in the klystron gallery of the BEPCⅡ linac.
In order to get high beam quality, a RF distribution system is required, with minimal phase drifts and errors in the BEPCⅡ linac. The additional installation of phase reference cables and monitoring equipments and stable RF distribution for BEPC linac are finished. The master oscillator is chosen to offer RF signal with low phase noise and a stable phase distribution system is built to deliver RF signal to each klystron. A phase and amplitude detector is constructed to measure the phase precisely and an IΦA unit is used for a phase shifter. Control software based on EPICS is used to connect all the units of the system, and a phasing method based on BPM is adopted to optimize the phase of each klystron. Now the phasing system is installed and tested in the klystron gallery of the BEPCⅡ linac.
Abstract:
The development of beam transport system of “Dragon-Ⅰ” linear induction accelerator(LIA) and the achievements are introduced in this paper. Along with the designs of many key elements such as solenoid coil, dipole steering coils, and multi-functional cavity, several research items including measurement of magnetic axis, alignment, layout and beam tuning are also described respectively. The experimental results indicated that the design of whole beam transport system is successful. In the end of the paper, some suggestions are given for the future work.
The development of beam transport system of “Dragon-Ⅰ” linear induction accelerator(LIA) and the achievements are introduced in this paper. Along with the designs of many key elements such as solenoid coil, dipole steering coils, and multi-functional cavity, several research items including measurement of magnetic axis, alignment, layout and beam tuning are also described respectively. The experimental results indicated that the design of whole beam transport system is successful. In the end of the paper, some suggestions are given for the future work.
Abstract:
Using the home-made synchrotron radiation soft X-ray polarimeter based on multilayer elements, the polarization characteristics of the Beamline 3W1B have been measured at Beijing Synchrotron Radiation Facility (BSRF). This paper compares the measuring results of using polarizer with the results without the polarizer at 206eV. The degree of linear polarization without the polarizer is 0.585. However, the degree of linear polarization is up to 0.995 when the beam is polarized by multilayer optical elements.
Using the home-made synchrotron radiation soft X-ray polarimeter based on multilayer elements, the polarization characteristics of the Beamline 3W1B have been measured at Beijing Synchrotron Radiation Facility (BSRF). This paper compares the measuring results of using polarizer with the results without the polarizer at 206eV. The degree of linear polarization without the polarizer is 0.585. However, the degree of linear polarization is up to 0.995 when the beam is polarized by multilayer optical elements.
Abstract:
The cavity mirrors of the storage-ring free-electron laser (SR-FEL) at 355nm and 248nm central wavelengths have been developed with the technologies of electron-beam evaporation deposition and ion-beam sputter deposition. The mirror coatings consists of “HfO2/SiO2+Al2O3/SiO2+M-SiO2”.The absolute reflectance and frequency-tunable range at 355nm are R=99.45% and Δλ(R≥99.00%)=75nm, respectively, for the broadband resonator mirror. For the mirror with the dual-central wavelengths, R=99.69% and Δλ(R≥99.00%)=59nm for the first band at 355nm; For the second band at 248nm, R=98.21%, Δλ(R≥99.00%)=9nm and Δλ(R≥98.00%)=51nm.
The cavity mirrors of the storage-ring free-electron laser (SR-FEL) at 355nm and 248nm central wavelengths have been developed with the technologies of electron-beam evaporation deposition and ion-beam sputter deposition. The mirror coatings consists of “HfO2/SiO2+Al2O3/SiO2+M-SiO2”.The absolute reflectance and frequency-tunable range at 355nm are R=99.45% and Δλ(R≥99.00%)=75nm, respectively, for the broadband resonator mirror. For the mirror with the dual-central wavelengths, R=99.69% and Δλ(R≥99.00%)=59nm for the first band at 355nm; For the second band at 248nm, R=98.21%, Δλ(R≥99.00%)=9nm and Δλ(R≥98.00%)=51nm.
Abstract:
Synchrotron Radiation based X-ray Fluorescent Microtomography (SR-XFMT) is a nondestructive technique for detecting elemental composition and distribution inside a specimen with high spatial resolution and sensitivity. In this paper, computer simulation of SR-XFMT experiment is performed. The influence of the sampling interval and the number of projections on the quality of SR-XFMT image reconstruction is analyzed. It is found that the sampling interval has greater effect on the quality of reconstruction than the number of projections.
Synchrotron Radiation based X-ray Fluorescent Microtomography (SR-XFMT) is a nondestructive technique for detecting elemental composition and distribution inside a specimen with high spatial resolution and sensitivity. In this paper, computer simulation of SR-XFMT experiment is performed. The influence of the sampling interval and the number of projections on the quality of SR-XFMT image reconstruction is analyzed. It is found that the sampling interval has greater effect on the quality of reconstruction than the number of projections.
Abstract:
Phase matching between different undulator segments is a key condition for high gain Free Electron Laser facilities to gain saturation laser output. This paper develops theoretical study on phase matching, provides the scheme to realize it and gives the parameters of terminations structure. According to the simulation result, ±100°phase adjustment range can be achieved when the pole height can be adjusted in the range of ±0.5mm.
Phase matching between different undulator segments is a key condition for high gain Free Electron Laser facilities to gain saturation laser output. This paper develops theoretical study on phase matching, provides the scheme to realize it and gives the parameters of terminations structure. According to the simulation result, ±100°phase adjustment range can be achieved when the pole height can be adjusted in the range of ±0.5mm.
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