2008 Vol. 32, No. 1
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2008, 32(1): 1-8. doi: 10.1088/1674-1137/32/1/001
Abstract:
A multilayered perceptrons neural network technique has been applied in the particle identification at BESIII. The networks are trained in each sub-detector level. The NN output of sub-detectors can be sent to a sequential network or be constructed as PDFs for a likelihood. Good muon-ID, electron-ID and hadron-ID are obtained from the networks by using the simulated Monte Carlo samples.
A multilayered perceptrons neural network technique has been applied in the particle identification at BESIII. The networks are trained in each sub-detector level. The NN output of sub-detectors can be sent to a sequential network or be constructed as PDFs for a likelihood. Good muon-ID, electron-ID and hadron-ID are obtained from the networks by using the simulated Monte Carlo samples.
2008, 32(1): 9-12. doi: 10.1088/1674-1137/32/1/002
Abstract:
Using the improved lattice Hamiltonian with massive Wilson quarks and the variational method, we study the quark mass m and the Wilson parameter r dependence of the vector meson mass MV in the two-dimensional SU(NC) lattice gauge theory. The numerical results show that for NC = 2，3，4，5，6，7，…，in the scaling window , MV/g is approximatively linear with m, but MV/g isn’t obviously dependent on r (this differs from the quark condensate). Particularly, when ，our numerical results agree very well with Bhattacharya’s analytical strong coupling result in the continuum, and the value of in two-dimensional SU(NC) lattice gauge theory is very close to that in Schwinger model．
Using the improved lattice Hamiltonian with massive Wilson quarks and the variational method, we study the quark mass m and the Wilson parameter r dependence of the vector meson mass MV in the two-dimensional SU(NC) lattice gauge theory. The numerical results show that for NC = 2，3，4，5，6，7，…，in the scaling window , MV/g is approximatively linear with m, but MV/g isn’t obviously dependent on r (this differs from the quark condensate). Particularly, when ，our numerical results agree very well with Bhattacharya’s analytical strong coupling result in the continuum, and the value of in two-dimensional SU(NC) lattice gauge theory is very close to that in Schwinger model．
2008, 32(1): 13-17. doi: 10.1088/1674-1137/32/1/003
Abstract:
The scaling and additivity properties of R\'enyi entropy in rapidity space of the instanton final state (IFS) and current jet identified by the $r$-sorting method from the QCDINS Monte Carlo event sample are studied. Asymptotic scaling of R\'enyi entropy $H_2$ is observed for the IFS while the $H_2$ for current jet tends to saturation with the decreasing of phase space scale. Furthermore, it is found that the additivity of $H_2$ holds well for IFS in narrow rapidity window at different positions. These results indicate that the IFS produced in the instanton-induced process of deep inelastic scattering has reached local equilibrium.
The scaling and additivity properties of R\'enyi entropy in rapidity space of the instanton final state (IFS) and current jet identified by the $r$-sorting method from the QCDINS Monte Carlo event sample are studied. Asymptotic scaling of R\'enyi entropy $H_2$ is observed for the IFS while the $H_2$ for current jet tends to saturation with the decreasing of phase space scale. Furthermore, it is found that the additivity of $H_2$ holds well for IFS in narrow rapidity window at different positions. These results indicate that the IFS produced in the instanton-induced process of deep inelastic scattering has reached local equilibrium.
2008, 32(1): 18-23. doi: 10.1088/1674-1137/32/1/004
Abstract:
With the high energy and luminosity, the planned ILC has the considerable capability to probe the new heavy particles predicted by the new physics models. In this paper, we study the potential to discover the lightest new gauge boson B_H of the littlest Higgs model via the processes e^+e^- ->r(Z)B_H at the ILC. The results show that the production rates of these two processes are large enough to detect B_H in a wide range of the parameter space, specially for the process e^+e^-->rB_H. Furthermore, there exist some decay modes for B_H which can provide the typical signal and clean background. Therefore, the new gauge boson B_H should be observable via these production processes with the running of the ILC if it exists indeed.
With the high energy and luminosity, the planned ILC has the considerable capability to probe the new heavy particles predicted by the new physics models. In this paper, we study the potential to discover the lightest new gauge boson B_H of the littlest Higgs model via the processes e^+e^- ->r(Z)B_H at the ILC. The results show that the production rates of these two processes are large enough to detect B_H in a wide range of the parameter space, specially for the process e^+e^-->rB_H. Furthermore, there exist some decay modes for B_H which can provide the typical signal and clean background. Therefore, the new gauge boson B_H should be observable via these production processes with the running of the ILC if it exists indeed.
2008, 32(1): 24-27. doi: 10.1088/1674-1137/32/1/005
Abstract:
As the nearest celestial body to the earth, the moon has become a hot spot in astronomy researches again recently [1-3], while the resource exploration is of much importance for lunar project. For the quasi-vacuum atmosphere in the moon, X-ray quantitative analysis is a effective way to determine concentration of the element on lunar surface, especially for determination of Mg, Al and Si[1,4]. As one of the ChangE-1’s payloads, the X-ray spectrometer is aiming to map the global elements distribution on the lunar surface. The X-ray Spectro-graph is examined on ground for its usage for quantitative analysis in deep space mission, and the results are in accord with the certified values.
As the nearest celestial body to the earth, the moon has become a hot spot in astronomy researches again recently [1-3], while the resource exploration is of much importance for lunar project. For the quasi-vacuum atmosphere in the moon, X-ray quantitative analysis is a effective way to determine concentration of the element on lunar surface, especially for determination of Mg, Al and Si[1,4]. As one of the ChangE-1’s payloads, the X-ray spectrometer is aiming to map the global elements distribution on the lunar surface. The X-ray Spectro-graph is examined on ground for its usage for quantitative analysis in deep space mission, and the results are in accord with the certified values.
2008, 32(1): 28-30. doi: 10.1088/1674-1137/32/1/006
Abstract:
Cross-sections for (n,2n) reactions have been measured on stannum isotopes at the neutron energies of 13.5 to 14.6 MeV using the activation technique. Data are reported for the following reactions: 112Sn(n,2n)111Sn, 118Sn(n,2n)117Sn and 124Sn(n,2n)123mSn. The neutron fluences were determined using the monitor reaction 93Nb(n, 2n)92mNb or 27Al(n,α)24Na. The results of present work were compared with data published previously.
Cross-sections for (n,2n) reactions have been measured on stannum isotopes at the neutron energies of 13.5 to 14.6 MeV using the activation technique. Data are reported for the following reactions: 112Sn(n,2n)111Sn, 118Sn(n,2n)117Sn and 124Sn(n,2n)123mSn. The neutron fluences were determined using the monitor reaction 93Nb(n, 2n)92mNb or 27Al(n,α)24Na. The results of present work were compared with data published previously.
2008, 32(1): 31-33. doi: 10.1088/1674-1137/32/1/007
Abstract:
The level structure of 190Pt has been studied experimentally using the 176Yb (18O, 4n) reaction at beam energies of 88 and 95MeV. γ-γ-t coincidence measurements were carried out. Based on the analysis of γ-γ coincidence relationships, the level scheme of 190Pt has been extended to high-spin states. A new structure built on the 3413.6keV 14+ state has been observed, and the pi13/2(-2) *nh9/2(-1)nj (j=p3/2 or f5/2) configuration has been tentatively assigned to it.
The level structure of 190Pt has been studied experimentally using the 176Yb (18O, 4n) reaction at beam energies of 88 and 95MeV. γ-γ-t coincidence measurements were carried out. Based on the analysis of γ-γ coincidence relationships, the level scheme of 190Pt has been extended to high-spin states. A new structure built on the 3413.6keV 14+ state has been observed, and the pi13/2(-2) *nh9/2(-1)nj (j=p3/2 or f5/2) configuration has been tentatively assigned to it.
2008, 32(1): 34-39. doi: 10.1088/1674-1137/32/1/008
Abstract:
The strongly damped collisions of very heavy nuclei 232Th+250Cf at energy range of 800-2000 MeV have been studied within the improved quantum molecular dynamics model. The production probability of primary superheavy fragments with Z greater than and equal to 114 for the asymmetric reaction 232Th+250Cf is higher than that for the symmetric reaction 244Pu+244Pu and 238U+238U. The calculated results show that the mass and charge distributions of primary fragments, the excitation energy distribution of SHFs depend on incident energies strongly. Two stages of the decay process of composite systems are distinguished by very different decay slopes , which imply different decay mechanism of the composite system. The first stage is for the decay of giant composite systems and the second one is corresponding to the decay of fragments of giant composite systems including SHFs through emitting neutron, proton or other charged particles, and also through fission or fragmentation. The slow reduction of SHFs in the second stage seems to be helpful for the survival of primary superheavy fragments
The strongly damped collisions of very heavy nuclei 232Th+250Cf at energy range of 800-2000 MeV have been studied within the improved quantum molecular dynamics model. The production probability of primary superheavy fragments with Z greater than and equal to 114 for the asymmetric reaction 232Th+250Cf is higher than that for the symmetric reaction 244Pu+244Pu and 238U+238U. The calculated results show that the mass and charge distributions of primary fragments, the excitation energy distribution of SHFs depend on incident energies strongly. Two stages of the decay process of composite systems are distinguished by very different decay slopes , which imply different decay mechanism of the composite system. The first stage is for the decay of giant composite systems and the second one is corresponding to the decay of fragments of giant composite systems including SHFs through emitting neutron, proton or other charged particles, and also through fission or fragmentation. The slow reduction of SHFs in the second stage seems to be helpful for the survival of primary superheavy fragments
2008, 32(1): 40-43. doi: 10.1088/1674-1137/32/1/009
Abstract:
We investigate the ground state properties of some superheavy nuclei, which may be synthesized in future experiments. Special emphases are placed on the alpha decay energies and half-lives. The alpha decay eergies and half-lives from different theoretical models are compared and discussed comprehensively. Through these calculations and comparisons, the optimal superheavy elements to be synthesized in future experiments are proposed theoretically.
We investigate the ground state properties of some superheavy nuclei, which may be synthesized in future experiments. Special emphases are placed on the alpha decay energies and half-lives. The alpha decay eergies and half-lives from different theoretical models are compared and discussed comprehensively. Through these calculations and comparisons, the optimal superheavy elements to be synthesized in future experiments are proposed theoretically.
2008, 32(1): 44-48. doi: 10.1088/1674-1137/32/1/010
Abstract:
The short-range correlations between nucleons in finite nuclei are investigated in the framework of Glauber multiple scattering theory without any free parameters. The effects on proton-nucleus and nucleus - nucleus interactions such as p - {4}He$ and {4}He- {12}C elastic scattering, and in particular the proton elastic scattering off hallo-like nuclei, {6,8}He, are estimated. Our calculations show that the short-range correlations play an important role in reproducing experimental data and could be also thought of as being the origin and nature of halo-like phenomena in the nuclear structure. More accurate calculations along this line are needed.
The short-range correlations between nucleons in finite nuclei are investigated in the framework of Glauber multiple scattering theory without any free parameters. The effects on proton-nucleus and nucleus - nucleus interactions such as p - {4}He$ and {4}He- {12}C elastic scattering, and in particular the proton elastic scattering off hallo-like nuclei, {6,8}He, are estimated. Our calculations show that the short-range correlations play an important role in reproducing experimental data and could be also thought of as being the origin and nature of halo-like phenomena in the nuclear structure. More accurate calculations along this line are needed.
2008, 32(1): 49-51. doi: 10.1088/1674-1137/32/1/011
Abstract:
The excitation function of evaporation residues formation probability of three heavy nuclei 194Pb, 200Pb and 206Pb is calculated using Langevin equation coupled with a statistical decay model. The results show that the ratio of neutron-to-proton (N/Z) of compound nuclei has an effect on survival probability and that a higher N/Z leads to a larger survival probability. This is due to the dependence of the fission barrier and pre-saddle particle emission on the N/Z of the systems.
The excitation function of evaporation residues formation probability of three heavy nuclei 194Pb, 200Pb and 206Pb is calculated using Langevin equation coupled with a statistical decay model. The results show that the ratio of neutron-to-proton (N/Z) of compound nuclei has an effect on survival probability and that a higher N/Z leads to a larger survival probability. This is due to the dependence of the fission barrier and pre-saddle particle emission on the N/Z of the systems.
2008, 32(1): 52-55. doi: 10.1088/1674-1137/32/1/012
Abstract:
A time projection chamber (TPC) readout by gas electron multipliers(GEM) detector is a very promising candidate for the central tracking system of ILC (International Linear Collider). A prototype was designed and setup in our lab and introduced here. Based on the tests during and after the assembly, we can conclude that the prototype TPC has been constructed uccessfully, it is ready for further study.
A time projection chamber (TPC) readout by gas electron multipliers(GEM) detector is a very promising candidate for the central tracking system of ILC (International Linear Collider). A prototype was designed and setup in our lab and introduced here. Based on the tests during and after the assembly, we can conclude that the prototype TPC has been constructed uccessfully, it is ready for further study.
2008, 32(1): 56-59. doi: 10.1088/1674-1137/32/1/013
Abstract:
To study the new RF control methods, a mathematic model of the RF system for the normal conducting Linac is built and implemented with the software of Matlab. The model contains of some typical units of the RF system, such as the klystron, the SLED and the traveling wave accelerating tube. Finally, the model is used to study the working point of the SLED and the adaptive feed forward algorithm for the RF control system. Simulation shows that the model works well as expected.
To study the new RF control methods, a mathematic model of the RF system for the normal conducting Linac is built and implemented with the software of Matlab. The model contains of some typical units of the RF system, such as the klystron, the SLED and the traveling wave accelerating tube. Finally, the model is used to study the working point of the SLED and the adaptive feed forward algorithm for the RF control system. Simulation shows that the model works well as expected.
2008, 32(1): 60-66. doi: 10.1088/1674-1137/32/1/014
Abstract:
The storage of long bunches for long time intervals needs flattened stationary buckets with large bucket height. In the case of small energy spread with a cooled beam, the Coulomb interaction cannot be ignored. The properties of the dual harmonic RF systems are discussed for the emittance dominated long bunches below transition. The external voltage has to be increased to compensate the Coulomb interaction to keep bunch length unchanged. The longitudinal motion of the initially mismatched beam has been studied for both single and dual harmonic RF system. Bucket height of the single harmonic system is too small even for 20 % mismatch. Halo formation and debunching can be seen after a few synchrotron periods for single particles with large amplitude. The simulation results by using ORBIT code for the FAIR-HESR synchrotron has been given together with theoretical analysis.
The storage of long bunches for long time intervals needs flattened stationary buckets with large bucket height. In the case of small energy spread with a cooled beam, the Coulomb interaction cannot be ignored. The properties of the dual harmonic RF systems are discussed for the emittance dominated long bunches below transition. The external voltage has to be increased to compensate the Coulomb interaction to keep bunch length unchanged. The longitudinal motion of the initially mismatched beam has been studied for both single and dual harmonic RF system. Bucket height of the single harmonic system is too small even for 20 % mismatch. Halo formation and debunching can be seen after a few synchrotron periods for single particles with large amplitude. The simulation results by using ORBIT code for the FAIR-HESR synchrotron has been given together with theoretical analysis.
2008, 32(1): 67-71. doi: 10.1088/1674-1137/32/1/015
Abstract:
In this paper, A new CCD camera system used in the OTR beam measurement is presented, the basic principle of OTR beam measurement and the CCD chips --ICX208CL and AD9929 which are used in the king position of camera system designing are introduced in details.
In this paper, A new CCD camera system used in the OTR beam measurement is presented, the basic principle of OTR beam measurement and the CCD chips --ICX208CL and AD9929 which are used in the king position of camera system designing are introduced in details.
2008, 32(1): 72-74. doi: 10.1088/1674-1137/32/1/016
Abstract:
It is very important to predict the coupling between the cavity and the high power input source in the coupler design. In this paper, the time domain method is used to calculate the external quality factor for the BEPCII superconducting cavity. A comparison between the simulation results and the experimental results is presented for the different antenna penetration depths of the coupler. The results of simulation and measurement of have a good agreement, and the error is about 10%. The geometry parameters related with are also studied.
It is very important to predict the coupling between the cavity and the high power input source in the coupler design. In this paper, the time domain method is used to calculate the external quality factor for the BEPCII superconducting cavity. A comparison between the simulation results and the experimental results is presented for the different antenna penetration depths of the coupler. The results of simulation and measurement of have a good agreement, and the error is about 10%. The geometry parameters related with are also studied.
2008, 32(1): 75-79. doi: 10.1088/1674-1137/32/1/017
Abstract:
The X-ray source based on Thomson scattering of ultrashort laser pulse with a relativistic electron beam is a means of generating tunable, narrow bandwidth, ultrashort pulse of hard X-rays. Such a sub-picosecond hard X-ray source is proposed at Tsinghua University, and a preliminary experiment with a 16MeV Backward Traveling electron linac and a 1.5J, 6ns Q-switched Nd:YAG laser is carried out first. A 6 ns pulse X-ray with a peak energy of 4.6 keV and an intensity of 1.7$\times 10^4$ per pulse was generated successfully in the experiment. The experimental setup, result and discussion are reported in this paper.
The X-ray source based on Thomson scattering of ultrashort laser pulse with a relativistic electron beam is a means of generating tunable, narrow bandwidth, ultrashort pulse of hard X-rays. Such a sub-picosecond hard X-ray source is proposed at Tsinghua University, and a preliminary experiment with a 16MeV Backward Traveling electron linac and a 1.5J, 6ns Q-switched Nd:YAG laser is carried out first. A 6 ns pulse X-ray with a peak energy of 4.6 keV and an intensity of 1.7$\times 10^4$ per pulse was generated successfully in the experiment. The experimental setup, result and discussion are reported in this paper.
2008, 32(1): 80-82. doi: 10.1088/1674-1137/32/1/018
Abstract:
Since the Coded Aperture technique has been successfully applied on X-ray imaging space telescopes, most attention of its development has turned to its application in medical imaging, for it has a very tempting quality to greatly inhance the detect sensitivity without gravely lower the spacial resolution. Now the artifacts of the coded aperture to image a radioactive object nearby comes up as an problem, and among types of coded apertures the MURA[1] is one of the most discussed. Roberto Arrcosi came up with the solution to remove the artifacts utilising mask and antimask. In this article we present two ways to eliminate the second order aberration based on his works.
Since the Coded Aperture technique has been successfully applied on X-ray imaging space telescopes, most attention of its development has turned to its application in medical imaging, for it has a very tempting quality to greatly inhance the detect sensitivity without gravely lower the spacial resolution. Now the artifacts of the coded aperture to image a radioactive object nearby comes up as an problem, and among types of coded apertures the MURA[1] is one of the most discussed. Roberto Arrcosi came up with the solution to remove the artifacts utilising mask and antimask. In this article we present two ways to eliminate the second order aberration based on his works.
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