120435997
High-pT hadronic trigger using electromagnetic calorimeter with the STAR detector
Abstract We derive a new method to improve the statistics of identified particles at high transverse momentum ( p T ) using online-triggered events by the STAR Barrel electro-magnetic-calorimeter (BEMC) detector. The BEMC is used to select charged hadrons ( π ± , K ± , and p ( p ¯ ) ) via hadronic shower energy deposited in the BEMC. With this trigger, the statistics of the high p T particles are significantly enhanced (by a factor of up to ∼ 100 for STAR) with trigger efficiency up to 20%. In addition, weak-decay V0s ( K S 0 and Λ ( Λ ¯ ) ) can be reconstructed by selecting the BEMC-trigger hadron as one of the decay daughters. We also show that the trigger efficiency can be obtained reliably in simulation and data-driven approaches, and final results from new method are compared with previous published results.
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.
112553011
MULTI-GAP RESISTIVE PLATE CHAMBER- A NEW TYPE OF DETECTOR FOR TIME OF FLIGHT
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%.
119185233
Study on the temperature dependence of BGO light yield
The temperature dependence of BGO coupled with photomultiplier tube R5610A-01 was studied in the range of −30–30°C. The temperature coefficient of the BGO and R5610A as a whole was tested to be −1.82%/°C. And the temperature coefficient of the gain of the R5610A is −0.44%/°C which was tested in the same situation using a blue LED. Thus the temperature coefficient of BGO’s light yield can be evaluated as −1.38%/°C.
121159892
Production of the charged top-pions from TC2 model at the TeV energy e-γ colliders
The top-pions (Πt0,±) and the top-Higgs (ht0) are the typical particles predicted by the topcolor-assisted technicolor (TC2) model and the observation of these particles can be regarded as direct evidence of the TC2 model. In this paper, we study three pair production processes of these new particles at the next generation eγ colliders, i.e., e-γ→e-Πt+Πt-, e-γ→νeΠt-Πt0 and e-γ→νeΠt-ht0. The results show that the production rates can reach the level 100–101 fb with reasonable parameter values. So one can expect that enough signals could be produced in future high- energy linear collider experiments. Furthermore, the flavor-changing (FC) decay modes Πt-→bc̄, Πt0(ht0)→tc̄ can provide us with the typical signal to detect these new particles.
116958429
Derivation of Maxwell's Equations Based on a Continuum Mechanical Model of Vacuum and a Singularity Model of Electric Charges
We speculate that the universe may be filled with a visco-elastic continuum which may be called aether. Thus, the Maxwell's equations in vacuum are derived by methods of continuum mechanics based on a continuum mechanical model of vacuum and a singularity model of electric charges.
53490794
Probability distributions in nuclear fragmentation
Recent studies of heavy ion fragmentation led to the conjecture that the hot and dense compound nuclei formed in the reaction do not decay into just any possible mass partition, but that some decay channels tend to be selected during breakup. We verify this conjecture by means of an extensive analysis of several distributions of decay probabilities. This simplifies the study of nuclear fragmentation tremendously.
119510990
High pT hadron spectra in high-energy heavy-ion collisions
Abstract We calculate the hadron spectra in high-energy pp , pA and AA collisions within a pQCD parton model. Analyses of experimental data show that the modification of the spectra in pA and AA as compared to that in pp collisions is consistent with multiple parton scattering scenario and is dictated by the transition from absorptive soft interaction at low p T to incoherent hard parton scattering at high p T . This analysis not only sheds new light on the limits to the physics analysis based on thermal fire-ball models but also provides a more quantitative baseline results on which one can study the effects of parton energy loss in the hadron spectra at high p T .
10358981
Fluctuations of rare particles as a measure of chemical equilibration
LBL-47721 Mc-Gill-preprint-01-09 GSI-Preprint/2001-10 Fluctuations of rare particles as a measure of chemical equilibration Nuclear Science Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720 GSI, D-64291 Darmstadt, Germany and Institute of Theoretical Physics, University of Wroclaw, PL-50204 Wroclaw, Poland †Department of Physics, McGill University, 3600 University Street, Montreal, QC H3A-2T8, Canada ∗RIKEN-BNL Research Center, Brookhaven National Laboratory, Upton, NY 11973 (August 17, 2001) We calculate the time evolution of ﬂuctuations for rare particles such as e.g. kaons in 1 AGeV or charmonium in 200 AGeV heavy ion collisions. We ﬁnd that these ﬂuctuations are a very sensitive probe of the degree of chemical equilibration reached in these collisions. Furthermore, measuring the second factorial moment the size of the initial population can be determined. a S. Jeon a †∗ , V. Koch a , K. Redlich a,c , and X.-N. Wang a c arXiv:nucl-th/0105035 v1 15 May 2001 I. INTRODUCTION Statistical models have long been used as a tool to de- scribe particle production in heavy ion and in high energy particle collisions [1–3]. Recent analysis have shown that these models can indeed give a satisfactory description of the multiplicities of most hadrons measured in A-A collisions for bombarding energies ranging from 1 AGeV (SIS) to 160 AGeV (SPS) [4,5]. Especially at the low energies (SIS) and for the rare particles such as kaons, the success of the statistical description has been a puz- zle and could not be understood within the state-of-the- art transport models [6]. For instance a recent analy- sis for chemical equilibration within a transport model [6] gives chemical equilibration time of the order of 300 fm/c for a situation relevant to 1 AGeV heavy ion col- lisions, considerably larger than the typical duration of such reaction, which is of the order of 30-50 fm/c. On the other hand the success of the statistical model cannot be disputed. Not only are the particle ratios reproduced for central collision over a wide range of bombarding en- ergy, but also the centrality dependence at low energies is consistent with the predictions of the statistical mod- els. In particular the almost quadratic dependence of the kaon multiplicity on the number of participating nucleon at SIS follows directly from the statistical model, once strangeness conservation is taken into account exactly [7]. Transport models on the other hand fail to reproduce the observed centrality dependence and particularly energy dependence of the K/π-ratio [8]. In a recent paper [9] some of us have shown, that the chemical equilibration time is considerably shortened if the strangeness conservation is taken into account ex- plicitly. However, using the new rate equations derived in this work combined with the cross sections as given in [14] one still arrives at equilibration time substantially exceeding the lifetime of the system. Does this mean that the success of the statistical model is a pure coincidence? This is very unlikely as statistical model naturally explains most of the basic features of experimental data in a very broad energy range from SIS up to SPS. It is conceivable that there are additional processes at work, like e.g. many particle collisions [15] or in medium modiﬁcations of hadron properties [16], which are not yet taken into account in transport models. Thus, a direct experimental determination of the rate of equilibration in heavy ion collisions is called for as it would possibly provide evidence for new physics. In this paper we will demonstrate that the ﬂuctuations of rare particles is a very sensitive probe of the degree of equili- bration reached in these collisions. Such a measurement, though certainly diﬃcult, could for the ﬁrst time provide a direct experimental evidence for chemical equilibration in heavy ion reactions. This paper is organized as follows. In the following sec- tion we set up the formalism. Then we present the results for the time dependence of the second factorial moment for several initial conditions. Before we turn to observa- tional issues we also will discuss the case when no con- straints from any U (1) charge conservation are present. II. FORMALISM In Ref. [9] the rate equation for particles which are sub- ject to an explicit U (1) “charge” conservation has been derived. Considering a binary process a 1 a 2 → b 1 b 2 with a = b one arrives at the following master equation for the probabilities P n to ﬁnd n particles dP n = [P n−1 − P n ] dτ