117939789
Magnetic shield of PMT used in DAMPE electromagnetic calorimeter
The magnetic characteristics of photomultiplier tube R5610A-01 are studied in this paper. The experimental data shows that the gain of R5610A-01 loses about 53% when the magnetic field is 3G along its +X axis. A cylinder of one-layer permalloy strip is able to reduce the effect of 3G magnetic field on the PMT's gain to less than 1%.
112553011
MULTI-GAP RESISTIVE PLATE CHAMBER- A NEW TYPE OF DETECTOR FOR TIME OF FLIGHT
118425985
Spatial anisotropy: a method to study anisotropic flow in heavy ion collisions
We introduce a method to study anisotropic flow parameter vn as a collective probe to Quark Gluon Plasma in relativistic heavy ion collisions. The emphasis is put on the use of the Fourier expansion of initial spatial azimuthal distributions of participant nucleons in the overlapped region. The coefficients n of Fourier expansion are called the spatial anisotropy parameter for the n-th harmonic. We propose that collective dynamics can be studied by vn/n. In this paper, we will discuss in particular the second (n = 2) and the fourth (n = 4) harmonics.
123771953
A high dynamic range readout unit for a calorimeter
A high dynamic range readout system, consisting of a multi-dynode readout PMT and a VA32 chip, is presented. An LED system is set up to calibrate the relative gains between the dynodes, and the ADC counts per MIPs from dynode 7 are determined under cosmic-ray calibration. A dynamic range from 0.5 MIPs to 1 x 10(5) MIPs is achieved.
118720520
Twist-4 contributions to the azimuthal asymmetry in SIDIS
We calculate the differential cross section for the unpolarized semi-inclusive deeply inelastic scattering (SIDIS) process e +N → e + q+X in leading order (LO) of perturbative QCD and up to twist-4 in power corrections and study in particular the azimuthal asymmetry 〈cos 2φ〉. The final results are expressed in terms of transverse momentum dependent (TMD) parton matrix elements of the target nucleon up to twist-4. We also apply it to e+A → e+q+X and illustrate numerically the nuclear dependence of the azimuthal asymmetry 〈cos 2φ〉 by using a Gaussian ansatz for the TMD parton matrix elements.
120471376
QGP phase transition and multiplicity fluctuations
The scaled factorial moments in QGP phase transitions are studied analytically by the extended Ginzburg-Landau model. The dependence of lnFq on phase space interval is different for the first- and second-order QGP phase transitions. When lnFq, are fitted to polynomials ofX≡δ1/3, the relative sign between the fitted coefficients ofX andbq,1 calculated theoretically can be used to judge the order of phase transitions. Two sets of experimental data are reanalysed and the phase transitions are the first order for one set of data but the second order for another.
118727848
Production of the neutral top pion at the e gamma colliders
In the framework of topcolor-assisted technicolor(TC2) model, we study a neutral toppion production process $e^{-}\gamma\to e^{-}\Pi^{0}_{t}$ in this paper. Our results show that the production cross section of $e^{-}\gamma\to e^{-}\Pi^{0}_{t}$ can reach the level of several tens fb, and over $10^{3}$ neutral toppion events can be produced in the planned $e^+e^-$ linear colliders each year. Therefore, such a toppion production process provides us a unique chance to detect toppion events and test the TC2 model. On the other hand, the cross section of $e^{-}\gamma\to e^{-}\Pi^{0}_{t}$ is about one order of magnitude larger than those of some similar processes in SM and MSSM(i.e., $e^{-}\gamma\to e^{-}H$ in SM and $e^{-}\gamma\to e^{-}H^{0}(A^0,h^0)$ in MSSM). So, we can easily distinguish the neutral toppion from other neutral Higgs bosons in SM and MSSM.
14243928
Dilepton and photon productions from a coherent pion oscillation
Abstract Since the electromagnetic current for a pion system coincides with the third component of the isovector current, the isospin angular oscillation of a coherent field can be a significant source for the electromagnetic emissions. We study the characteristic dilepton and photon emissions from the classical pion field oscillation in the QCD vacuum. The general analytical solution obtained in the nonlinear σ model is used to calculate the electromagnetic current density, which exhibits a light-front singularity and decreases rapidly as inverse square of the proper time due to a longitudinal expansion. The momentum and invariant mass spectra of the direct photon and dilepton are calculated using the space-time evolution of the chiral condensate field.
118479131
Venus transit, aureole and solar diameter
The possibility to measure the solar diameter using the transits of Mercury has been exploited to investigate the past three centuries of its evolution and to calibrate these measurements made with satellites. This measurement basically consists to compare the ephemerides of the internal contact timings with the observed timings. The transits of Venus of 2004 and 2012 gave the possibility to apply this method, involving a planet with atmosphere, with the refraction of solar light through it creating a luminous arc all around the disk of the planet. The observations of the 2012 transit made to measure the solar diameter participate to the project Venus Twilight Experiment to study the aureole appearing around it near the ingress/egress phases.