122978749
Dynamic nuclear polarization of irradiated targets
Abstract We report studies of dynamic nuclear polarization of irradiated targets. The polarized target operated at a magnetic field of 5 T and a temperature of 1 K and was irradiated with the 20 GeV electron beam at the Stanford Linear Accelerator. Our results indicate that the temperature at which the target is irradiated is important. The maximum proton polarization attained with radiation was measured for some seven hydrogen-rich compounds. Irradiated NH3 and ND3 were polarized to high values of P p ⋍ 0.75 and P d ⋍ 0.25 with short values of polarization growth time Tp, and with radiation resistance of the polarization about a factor of 30 greater than for normal chemically-doped hydrocarbons. Hence, irradiated NH3 and ND3 appear very promising as practical polarized target materials.
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.
122659739
The BES upgrade
Abstract The Beijing Spectrometer (BES) detector is a general purpose solenoid detector at the Beijing Electron Positron Collider (BEPC) in Beijing, China, that has collected large numbers of J/ψ, ψ′, D s , D and τ events. In this paper, we describe the recent upgrade of the initial BES detector (BESI) to the improved BESII detector.
182722222
First Level Trigger in the GEM Muon System
126253177
Experimental measurement of the mass of the tau lepton at the Beijing Electron Positron Collider (BEPC)
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 .
123717372
Search for quark compositeness in dijet angular distributions from pp collisions at $ \sqrt {s} = 7{ } $ TeV
A bstractA search for quark compositeness using dijet angular distributions from pp collisions at $ \sqrt {s} = 7 $ TeV is presented. The search has been carried out using a data sample corresponding to an integrated luminosity of 2.2 fb−1, recorded by the CMS experiment at the LHC. Normalized dijet angular distributions have been measured for dijet invariant masses from 0.4 TeV to above 3 TeV and compared with a variety of contact interaction models, including those which take into account the effects of next-to-leading-order QCD corrections. The data are found to be in agreement with the predictions of perturbative QCD, and lower limits are obtained on the contact interaction scale, ranging from 7.5 up to 14.5 TeV at 95 % confidence level.
119288954
Rigidity of SU(2, 2|2)-symmetric solutions in Type IIB
We investigate the existence of half-BPS solutions in Type IIB supergravity which are invariant under the superalgebra SU(2, 2|2) realized on either AdS5 × S2 × S1 or AdS5 × S3 warped over a Riemann surface Σ with boundary. We prove that, in both cases, the only solution is AdS5 × S5 itself. We argue that this result provides evidence for the non-existence of fully back-reacted intersecting D3/D7 branes with either AdS5 × S2 × S1 × Σ or AdS5 × S3 × Σ near-horizon limits.
56287054
GAMMA-RAY FLARES FROM Mrk421 IN 2008 OBSERVED WITH THE ARGO-YBJ DETECTOR
In 2008, the blazar Markarian 421 entered a very active phase and was one of the brightest sources in the sky at TeV energies, showing frequent flaring episodes. Using the data of ARGO-YBJ, a full coverage air shower detector located at Yangbajing (4300 m a.s.l., Tibet), we monitored the source at gamma-ray energies E>0.3 TeV during the whole year. The observed flux was variable, with the strongest flares in March and June, in correlation with X-ray enhanced activity. While during specific episodes the TeV flux could be several times larger than the Crab Nebula one, the average emission from day 41 to 180 was almost twice the Crab level, with an integral flux of (3.6 ? 0.6)?? 10?11 photons cm?2 s?1 for energies E>1 TeV, and decreased afterward. This Letter concentrates on the flares that occurred in the first half of June. This period has been deeply studied from optical to 100 MeV gamma rays, and partially up to TeV energies, since the moonlight hampered the Cherenkov telescope observations during the most intense part of the emission. Our data complete these observations, with the detection of a signal with a statistical significance of 3.8 standard deviations on June 11-13, corresponding to a gamma-ray flux about 6 times larger than the Crab one above 1 TeV. The reconstructed differential spectrum, corrected for the intergalactic absorption, can be represented by a power law with an index ? = ?2.1+0.7 ?0.5 extending up to several TeV. The spectrum slope is fully consistent with previous observations reporting a correlation between the flux and the spectral index, suggesting that this property is maintained in different epochs and characterizes the source emission processes.