H. F. Chen

Perspectives of a mid-rapidity dimuon program at the RHIC: a novel and compact muon telescope detector

Perspectives of a mid-rapidity dimuon program at the RHIC: a novel and compact muon telescope detector L Ruan 1 , G Lin 2 , Z Xu 1 , K Asselta 1 , H F Chen 3 , W Christie 1 , H J Crawford 4 , J Engelage 4 , G Eppley 5 , T J Hallman 1 , C Li 3 , J Liu 5 , W J Llope 5 , R Majka 2 , T Nussbaum 5 , J Scheblein 1 , M Shao 3 , R Soja 1 , Y Sun 3 , Z Tang 3 , X Wang 6 and Y Wang 6 July 17, 2009 This work was supported by the Director, Office of Science, Office of Nuclear Science of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.

A single Time-of-Flight tray based on multigap resistive plate chambers for the STAR experiment at RHIC

Abstract The STAR experiment at RHIC plans to implement a 60 m 2 Time-of-Flight (TOF) system. The Multigap Resistive Plate Chamber (MRPC) is a suitable candidate for the STAR TOF system due to its time resolution of order of 60 ps with efficiencies in excess of 97%. We obtained this result with modules composed of 6 gas gaps of 220 μm and pad area of 20 cm 2 . In this paper, we report on the performance of this MRPC module and present the current status of the construction and installation into STAR of a prototype tray.

Beam test results of two kinds of multi-gap resistive plate chambers

Abstract Beam test results of 6- and 10-gap Multi-gap Resistive Plate Chambers (MPRCs) are reported in detail. The corresponding experimental setup at CERN PS-T10 area is explained. The time resolution and detection efficiency of the 6-gap MRPC is around 65 ps , which is good enough for the TOF detector of STAR experiment, while the 10-gap MRPC has a time resolution below 55 ps .

K(892)* resonance production in Au+Au and p+p collisions at sqrt(sNN) = 200 GeV at RHIC

Author(s): Adams, J.; Aggarwal, M.M.; Ahammed, Z.; Amonett, J.; Anderson, B.D.; Arkhipkin, D.; Averichev, G.S.; Badyal, S.K.; Bai, Y.; Balewski, J.; Barannikova, O.; Barnby, L.S.; Baudot, J.; Bekele, S.; Belaga, V.V.; Bellwied, R.; Berger, J.; Bezverkhny, B.I.; Bharadwaj, S.; Bhasin, A.; Bhati, A.K.; Bhatia, V.S.; Bichsel, H.; Billmeier, A.; Bland, L.C.; Blyth, C.O.; Bonner, B.E.; Botje, M.; Boucham, A.; Brandin, A.V.; Bravar, A.; Bystersky, M.; Cadman, R.V.; Cai, X.Z.; Caines, H.; Calderon de la Barca Sanchez, M.; Castillo, J.; Cebra, D.; Chajecki, Z.; Chaloupka, P.; Chattopadhyay, S.; Chen, H.F.; Chen, Y.; Cheng, J.; Cherney, M.; Chikanian, A.; Christie, W.; Coffin, J.P.; Cormier, T.M.; Cramer, J.G.; Crawford, H.J.; Das, D.; Das, S.; de Moura, M.M.; Derevschikov, A.A.; Didenko, L.; Dietel, T.; Dogra, S.M.; Dong, W.J.; Dong, X.; Draper, J.E.; Du, F.; Dubey, A.K.; Dunin, V.B.; Dunlop, J.C.; Dutta Mazumdar, M.R.; Eckardt, V.; Edwards, W.R.; Efimov, L.G.; Emelianov, V.; Engelage, J.; Eppley, G.; Erazmus, B.; Estienne, M.; Fachini, P.; Faivre, J.; Fatemi, R.; Fedorisin, J.; Filimonov, K.; Filip, P.; Finch, E.; Fine, V.; Fisyak, Y.; Fomenko, K.; Fu, J.The short-lived K(892)* resonance provides an efficient tool to probe properties of the hot and dense medium produced in relativistic heavy-ion collisions. We report measurements of K* in root s(NN)=200 GeV Au+Au and p+p collisions reconstructed via its hadronic decay channels K(892)*(0)-> K pi and K(892)*(+/-)-> K(S)(0)pi(+/-) using the STAR detector at the Relativistic Heavy Ion Collider at Brookhaven National Laboratory. The K*(0) mass has been studied as a function of p(T) in minimum bias p+p and central Au+Au collisions. The K(*) p(T) spectra for minimum bias p+p interactions and for Au+Au collisions in different centralities are presented. The K*/K yield ratios for all centralities in Au+Au collisions are found to be significantly lower than the ratio in minimum bias p+p collisions, indicating the importance of hadronic interactions between chemical and kinetic freeze-outs. A significant nonzero K*(0) elliptic flow (v(2)) is observed in Au+Au collisions and is compared to the K(S)(0) and Lambda v(2). The nuclear modification factor of K* at intermediate p(T) is similar to that of K(S)(0) but different from Lambda. This establishes a baryon-meson effect over a mass effect in the particle production at intermediate p(T) (2 < p(T)<= 4 GeV/c).

New prototype multi-gap resistive plate chambers with long strips

A new kind of Multi-gap Resistive Plate Chamber (MRPC) has been built for the large-area Muon Telescope Detector (MTD) for the STAR experiment at the Relativistic Heavy Ion Collider (RHIC). These long read-out strip Multi-gap Resistive Plate Chambers (LMRPCs) have an active area of 87.0 � 17.0 cm 2 and ten 250mm-thick gas gaps arranged as a double stack. Each read-out strip is 2.5 cm wide and 90 cm long. The signals are read-out at both ends of each strip. Cosmic ray tests indicate a time resolution of � 70 ps and a detection efficiency of greater than 95%. Beam tests performed at T963 at Fermilab indicate a time resolution of 60–70 ps and a spatial resolution of � 1 cm along the strip direction. & 2008 Elsevier B.V. All rights reserved.

Testing the time resolution of the BESIII end-cap TOF detectors

Modules of the end-cap time-of-flight detector (ETOF) for the Beijing spectrometer upgrade (BESIII) using different types of scintillators, BC408, BC404 and EJ204, were tested with an 800 MeV electron beam. Different wrapping materials were also tested to improve the light collection efficiency and time resolution. The enhanced specular reflector (ESR) film was found to be the best wrapping material. A time resolution of better than 80 ps over the full length of the ETOF module was achieved.

Muon-pair and tau-pair production in two-photon collisions at LEP

The QED processes e^+ e^- ->e^+ e^- \mu^+ \mu^- and e^+ e^- ->e^+ e^- \tau^+ \tau^- are studied with the L3 detector at LEP using an untagged data sample collected at centre-of-mass energies 161 GeV<sqrt{s}<209 GeV. The tau-pairs are observed through the associated decay of one tau into e\nu\nu and the other into \pi\pi\nu . The cross sections are measured as a function of sqrt{s}. For muon pairs, the cross section of the \gamma\gamma ->\mu^+\mu^- process is also measured as a function of the two-photon centre-of-mass energy for 3 GeV<W_{\gamma\gamma}<40 GeV. Good agreement is found between these measurements and the O(\alpha^4) QED expectations. In addition, limits on the anomalous magnetic and electric dipole moments of the tau lepton are extracted.

Measurement of the Z-boson mass using e+e- →Zγ events at centre-of-mass energies above the Z pole

Events from the e + e − → Zγ process with hard initial-state radiation collected with the L3 detector at centre-of-mass energies between 183 GeV and 209 GeV are used to measure the mass of the Z boson. Decays of the Z boson into hadrons or muon pairs are considered and the Z mass is determined to be 91.272±0.032 (stat.)± 0.033 (syst.) GeV, in agreement with the value measured at the Z resonance. Alternatively , assuming this measured value of the Z mass, the method determines the LEP centre-of-mass energy, found to be 175 ± 68 (stat.) ± 68 (syst.) MeV lower than the nominal value.

Calibration and performance of the STAR Muon Telescope Detector using cosmic rays

We report the timing and spatial resolution from the Muon Telescope Detector (MTD) installed in the STAR experiment at RHIC. Cosmic ray muons traversing the STAR detector have an average transverse momentum of 6 GeV/c. Due to their very small multiple scattering, these cosmic muons provide an ideal tool to calibrate the detectors and measure their timing and spatial resolution. The values obtained were ∼100 ps and ∼1-2 cm, respectively. These values are comparable to those obtained from cosmic-ray bench tests and test beams.

Test of high time resolution MRPC with different readout modes for the BESIII upgrade

In order to further enhance the particle identification capability of the Beijing Spectrometer (BESIII), it is proposed to upgrade the current end-cap time-of-flight (eTOF) detector with multi-gap resistive plate chamber (MRPC). The prototypes, together with the front end electronics (FEE) and time digitizer (TDIG) module have been tested at the E3 line of Beijing Electron Positron Collider (BEPCII) to study the difference between the single and double-end readout MRPC designs. The time resolutions (sigma) of the single-end readout MRPC are 47/53 ps obtained by 600 MeV/c proton/pion beam, while that of the double-end readout MRPC is 40 Ps (proton beam). The efficiencies of three MRPC modules tested by both proton and pion beam are better than 98%. For the double-end readout MRPC, no incident position dependence is observed