19719907
Trigger System of BESIII
The trigger system of Beijing Spectrometer III, part of the upgrade of Beijing Electron Positron Collider, has been designed and implemented, and is ready for installation. This paper describes briefly the system components, its characteristics, and some technical issues. The system consists mainly of four parts: MDC (drift chamber) tracking subsystem, EMC (electromagnetic calorimeter) subsystem, TOF (time of flight) subsystem and global trigger. Some highlights in designing of this system includes: trigger scheme optimization with software simulation; optical transmission between trigger and FEEs to realize isolation with FEEs to avoid ground loop current interference; designed with most latest FPGA (Xilinx Spartan 3, VirtexII Pro...) for simplicity, high reliability and easy maintenance and hence smaller system; FPGA in-system programming or firmware online downloadable via onboard, panel connector and/or VME bus for modification flexibility during commissioning. Different from the usual fix delay data transmission from FEE to trigger, the RocketIO has been used as SEDES.
123610392
SEARCH FOR NEW MASSIVE PARTICLES IN COSMIC RAYS
In this paper, some unusual cosmic ray events are reviewed. They are the Yunnan event recorded in 1972 using a cloud chamber at Yunnan Cosmic Ray Station (YCRS) near Kunming, the south-west of China; the six exotic events (Kolar events) collected during 1965 to 1975 in the Kolar Gold Mine Field (KGF) in south India; and a double-core event obtained also in KGF in 1979 at a depth different from that where the other six were obtained, In addition, some interesting phenomena were also noticed: the abnormal upward muon flux observed by the MINI collaboration, and several intriguing signals seen in the proton detector in KGF, A careful kinematics analysis has shown that all these exotic events are likely to be related to a kind of heavy and slow-moving (i.e. with a Lorentz factor gamma approximate to 2-5) particles produced from cosmic ray interactions. Besides, the rough flux estimates in these experiments seem to indicate that the event rate does not depend on the depth. Thus a natural hypothesis is that there is a heavy and neutral component in the cosmic rays which might be related with the long-sought weakly interacting massive particle (WIMP) - one of the most promising candidates of the dark matter of our Universe. Moreover, from the tracks seen in these events, there is also a signal of the possible existence of a kind of heavy and charged particles with a relatively long lifetime (say, longer than 10(-9) s) which might be the interacting products of the unknown cosmic ray particles mentioned above. We then turn to the question of how to search for these exotic particles in cosmic rays, and propose to build a dedicated magnetic spectrometer for identifying them.
33607009
Direct measurement of the Ds branching fraction to phi pi.
The Beijing Spectrometer (BES) Collaboration has observed exclusive pair production of {ital D}{sub {ital s}} mesons at the Beijing Electron-Positron Collider (BEPC) at a center-of-mass energy of 4.03 GeV. The {ital D}{sub {ital s}} mesons are detected in the {phi}{pi}{sup +}, {ital {bar K}} {sup *0}{ital K}{sup +}, and {ital {bar K}} {sup 0}{ital K}{sup +} decay modes; two fully reconstructed events yield the value (3.9{sub {minus}1.9{minus}1.1}{sup +5.1+1.8})% for the {ital D}{sub {ital s}} branching fraction to {phi}{pi}. This is the first direct, model-independent measurement of this quantity.
126124755
Measurement of the internal spin structure of the proton
Our final results of measurements at SLAC of the spin dependent asymmetry in the deep inelastic scattering of longitudinally polarized electrons by longitudinally polarized protons are presented. Data were obtained at a scattering angle of 10° and for incident energies of 16.2 and 22.7 GeV, which cover the kinematic range 0.18<x<0.70 and 3.5<Q2<10.0 (GeV/c)2. We compare our results with various models of proton spin structure and with the Bjorken and Ellis‐Jaffe sum rules.
120632182
Direct measurements of the branching fractions for inclusive K± and inclusive semileptonic decays of D+ and D0 mesons
Abstract With singly-tagged D ¯ samples selected from the data collected at and around 3.773 GeV with the BESII detector at the BEPC collider, we have measured the branching fractions for the inclusive K ± decays of D + and D 0 mesons, which are BF ( D + → K − X ) = ( 24.7 ± 1.3 ± 1.2 ) % , BF ( D + → K + X ) = ( 6.1 ± 0.9 ± 0.4 ) % , BF ( D 0 → K − X ) = ( 57.8 ± 1.6 ± 3.2 ) % and BF ( D 0 → K + X ) = ( 3.5 ± 0.7 ± 0.3 ) % , respectively. We have also measured the branching fractions for the inclusive semileptonic decays of D + and D 0 mesons to be BF ( D + → e + X ) = ( 15.2 ± 0.9 ± 0.8 ) % and BF ( D 0 → e + X ) = ( 6.3 ± 0.7 ± 0.4 ) % . These yield the ratio of their partial widths to be Γ ( D + → e + X ) / Γ ( D 0 → e + X ) = 0.95 ± 0.12 ± 0.07 .
125302092
Measurements of the line shapes of D anti-D production and the ratio of the production rates of D+ D- and D0 anti-D0 in e+ e- annihilation at psi(3770) resonance
Abstract We report measurements of the line shapes of D + D − , D 0 D ¯ 0 and D D ¯ production as well as the line shape of the ratio of the production rates of D + D − and D 0 D ¯ 0 in e + e − annihilation at ψ ( 3770 ) resonance. We find that the line shapes of D + D − , D 0 D ¯ 0 and D D ¯ production are similar to an anomalous line shape of cross sections for e + e − → hadrons observed in the center-of-mass energy range from 3.70 to 3.87 GeV.
52266731
Measurement of the cosmic ray antiproton/proton flux ratio at TeV energies with the ARGO-YBJ detector
B. Bartoli, 2 P. Bernardini, 4 X.J. Bi, C. Bleve, 4 I. Bolognino, 7 P. Branchini, A. Budano, A.K. Calabrese Melcarne, P. Camarri, 11 Z. Cao, R. Cardarelli, S. Catalanotti, 2 C. Cattaneo, S.Z. Chen, T.L. Chen, Y. Chen, P. Creti, S.W. Cui, B.Z. Dai, G. D’Aĺı Staiti, 16 Danzengluobu, I. De Mitri, 4 B. D’Ettorre Piazzoli, 2 T. Di Girolamo, 2 X.H. Ding, G. Di Sciascio, ∗ C.F. Feng, Zhaoyang Feng, Zhenyong Feng, E. Giroletti, 7 Q.B. Gou, Y.Q. Guo, H.H. He, Haibing Hu, Hongbo Hu, Q. Huang, M. Iacovacci, 2 R. Iuppa, 11, † I. James, 19 H.Y. Jia, Labaciren, H.J. Li, J.Y. Li, X.X. Li, G. Liguori, 7 C. Liu, C.Q. Liu, J. Liu, M.Y. Liu, H. Lu, X.H. Ma, G. Mancarella, 4 S.M. Mari, 19 G. Marsella, 20 D. Martello, 4 S. Mastroianni, P. Montini, 19 C.C. Ning, A. Pagliaro, M. Panareo, B. Panico, 11 L. Perrone, P. Pistilli, 19 X.B. Qu, F. Ruggieri, P. Salvini, R. Santonico, 11 P.R. Shen, X.D. Sheng, F. Shi, C. Stanescu, A. Surdo, Y.H. Tan, P. Vallania, 23 S. Vernetto, 23 C. Vigorito, 24 B. Wang, H. Wang, C.Y. Wu, H.R. Wu, B. Xu, L. Xue, Y.X. Yan, Q.Y. Yang, X.C. Yang, Z.G. Yao, A.F. Yuan, M. Zha, H.M. Zhang, Jilong Zhang, Jianli Zhang, L. Zhang, P. Zhang, X.Y. Zhang, Y. Zhang, Zhaxiciren, Zhaxisangzhu, X.X. Zhou, F.R. Zhu, Q.Q. Zhu, and G. Zizzi
145909018
Highlights from the ARGO-YBJ experiment
— The ARGO-YBJ experiment is a multipurpose detector exploiting the full coverage approach at very high altitude. The apparatus, in stable data taking since November 2007 with an energy threshold of a few hundreds of GeV and a duty-cycle > 85%, is located at the YangBaJing Cosmic Ray Laboratory (Tibet, P.R. China, 4300 m a.s.l., 606 g/cm). A number of interesting results are available in cosmic ray physics and in gamma-ray astronomy after the first 3 years of stable data taking. In this paper gamma-ray astronomy results are summarized.
117145668
Attenuation study for Tibet Water Cherenkov Muon Detector Array-A
This work aims at online calibrating the signal attenuation of the long cable used in Tibet Water Cherenkov Muon detector array-A (Tibet MD-A) under the 37 000 m2 Tibet air shower array. Based on the waterproof connection of the PMT (R3600_06) with the signal cable, and the characters of the high voltage divider, terminal reflection method is explored and used for measuring the signal attenuation with a practical way to eliminate the contribution of the pulse baseline (pedestal). Comparison measurement between it and QDC (Charge-to-Digital Conversion) data taking method are carried out by using open-ended cables, confirming that terminal reflection method is a fast and convenient method, and suitable to online calibrate the signal attenuation for Tibet MD-A. At 26\degree C, the measured attenuation coefficient with the 250-m cable, permanently connected to the PMT, is ~13.9%. Also, the cable frequency response is measured by using the sinusoidal signals, which could be used to study the time dispersion of the real signal produced with Tibet MD-A detector via Fourier analysis.
52249775
Medium scale anisotropy in the TeV cosmic ray flux observed by ARGO-YBJ
B. Bartoli, P. Bernardini, X. J. Bi, I. Bolognino, P. Branchini, A. Budano, A.K. Calabrese Melcarne, P. Camarri, Z. Cao, R. Cardarelli, S. Catalanotti, S. Z. Chen, T. L. Chen, P. Creti, S.W. Cui, B. Z. Dai, A. D’Amone, Danzengluobu, I. De Mitri, B. D’Ettorre Piazzoli, T. Di Girolamo, G. Di Sciascio,* C. F. Feng, Zhaoyang Feng, Zhenyong Feng, Q. B. Gou, Y.Q. Guo, H. H. He, Haibing Hu, Hongbo Hu, M. Iacovacci, R. Iuppa, H.Y. Jia, Labaciren, H. J. Li, G. Liguori, C. Liu, J. Liu, M.Y. Liu, H. Lu, X. H. Ma, G. Mancarella, S.M. Mari, G. Marsella, D. Martello, S. Mastroianni, P. Montini, C. C. Ning, M. Panareo, B. Panico, L. Perrone, P. Pistilli, F. Ruggieri, P. Salvini, R. Santonico, S. N. Sbano, P. R. Shen, X.D. Sheng, F. Shi, A. Surdo, Y. H. Tan, P. Vallania, S. Vernetto, C. Vigorito, H. Wang, C. Y. Wu, H. R. Wu, L. Xue, Y.X. Yan, Q.Y. Yang, X. C. Yang, Z. G. Yao, A. F. Yuan, M. Zha, H.M. Zhang, L. Zhang, X.Y. Zhang, Y. Zhang, Zhaxiciren, Zhaxisangzhu, X.X. Zhou, F. R. Zhu, Q.Q. Zhu, and G. Zizzi
124567745
Observation of the 2005 January 20 GLE event using Yangbajing. solar neutron telescope & neutron monitor
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 degrees E, 30.11 degrees 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 3.7 sigma in the time window of 07:00-07:05UT and 6.0 sigma 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.