109766852
Improvement of the storage ring UHV system of NSRL
NSRL storage-ring has been operated for fourteen years, The typical life time is 600 mins at 200 mA and 800 MeV. The new injection ceramic chamber, bend chamber, undulator and NEG pumps were installed, new vacuum measure and control system was debugged in 2002 summer, as part of NSRL phase II project to enhance the quality, stability and long-term reliability. The average pressure of storage ring is better than 2E-8 Pascal after 48 hour large current direct backout and 48 hour ion pumps operation, this better vacuum can benefit the phase II project's object, beam lifetime 600 mins at 300 mA and 800 MeV.
32668015
A Method to Calibrate Beam Position Monitor at HLS 200 MeV Linac
In order to improve injection efficiency of HLS 200Mev LINAC, we redesign a new strip line beam position monitor system, which is consisted of a strip line structure and a signal processing system. We decide on an online calibration method based on beam to find out the geometry centre displacement and relative gain offset. Before the BPM testing bench has been prepared, we make a simulation based on the model accounted for all factors influencing signal amplitudes and get the calibrating results. At last, we analyze the nonlinearity effect on the calibration results.
42202614
Status of the NSRL Storage Ring UHV System after Project-II
The NSRL project-II has been finished in December 2004. The UHV system of storage ring has undergone improvement and now provide long beam lifetime and stable operations, the average pressure of ring is better than 2×10-8 Pascal without beam and 1×10-7 Pascal with beam, The typical beam lifetime is 12 hours at 300 mA and 800 MeV without wiggler and 8 hours at 300 mA and 800 MeV with wiggler on. The improvements and status of NSRL storage ring are described in this paper.
59428259
The upgrade of HLS linac control system
The linac control system of Hefei Light Source (HLS) was initially build in late 1980's, and a concerted effort has been put forth to upgrade it to a new, distributed one based on EPICS. Industrial PC based hardware is widely used as not only IOC but also front-end controller. Besides industrial PC, PLC and single-chip microcomputer are also used as front-end controllers in some subsystems. The software for industrial PC based front-end controller is developed based on vxWorks real-time operating system. The software for PLC and single-chip microcomputer are written with ladder software package and assemble language respectively. PC with Linux operating system and SUN workstation with Solaris operating system are used as operator interfaces. High level control is made up of some EPICS tools and Tcl/Tk scripts.
14513092
Determination of the number of light neutrino species from single photon production at LEP
A determination of the number of light neutrino families performed by measuring the cross section of single photon production in \ee\ collision near the \Zo\ resonance is reported. From an integrated luminosity of $100~\mathrm{pb^{-1}}$, collected during the years 1991--94, we have observed 2091 single photon candidates with an energy above 1~\GeV\ in the polar angular region $45^\circ \theta_\gamma 135^\circ$. From a maximum likelihood fit to the single photon cross section, the \Zo\ decay width into invisible particles is measured to be $\Ginv = 498 \pm 12 \mathrm{(stat)} \pm 12 \mathrm{(sys)~MeV}$. Using the Standard Model couplings of neutrinos to the \Zo, the number of light neutrino species is determined to be $N_\nu = 2.98 \pm 0.07 (\mathrm{stat}) \pm 0.07 (\mathrm{sys}).$
113240014
HLS bunch current measurement system
Bunch current is an important parameter for studying the injection fill-pattern in the storage ring and the instability threshold of the bunch, and the bunch current monitor also is an indispensable tool for the top-up injection. A bunch current measurement (BCM) system has been developed to meet the needs of the upgrade project of Hefei Light Source (HLS). This paper presents the layout of the BCM system. The system based on a high-speed digital oscilloscope can be used to measure the bunch current and synchronous phase shift. To obtain the absolute value of bunch-by-bunch current, the calibration coefficient is measured and analyzed. Error analysis shows that the RMS of bunch current is less than 0.01 mA when bunch current is about 5 mA, which can meet project requirement.
56077124
A closed orbit measurement with the NSRL BPM system
The beam position monitor system (BPM) of NSRL electron storage ring have a resolution of 10 microns with an accuracy of 50 microns, which is adequate fix beam position measurement and the closed orbit correction. The paper describes both of the BPM system and the closed orbit measurement.
119852910
Measurement of the mass difference between top and anti-top quarks in pp collisions at √s = 7 TeV using the ATLAS detector
A measurement of the mass difference between top and anti-top quarks is presented. In a 4.7 fb(-1) data sample of proton-proton collisions at root s = 7 TeV recorded with the ATLAS detector at the ...
118444339
Threshold resummation effects in Higgs boson pair production at the LHC
A bstractWe investigate the resummation effects in the Standard Model Higgs boson pair production through gluon-gluon fusion at the LHC with soft-collinear effective theory. We calculate the total cross section and the invariant mass distribution at Next-to-Next-to-Leading-Logarithmic level with π2-enhanced terms resummed, which are matched to the QCD Next-to-Leading Order results. In the high order QCD predictions exact top quark mass effects are included in full form factors. Our results show that the resummation effects increase the Next-to-Leading Order results by about 20% ~ 30%, and the scale uncertainty is reduced to 8%, which leads to increased confidence on the theoretical predictions. The PDF+αs uncertainties are almost not changed after including resummation effects. We also study the sensitivities of the total cross section and the invariant mass distribution to the Higgs boson self-coupling. We find that the total cross section and the invariant mass distribution shape depend strongly on the Higgs boson self-coupling, and therefore it is possible to extract Higgs boson self-coupling from the total cross section and invariant mass distribution when the measurement precision increases at the LHC.