Publications (29)29.93 Total impact
-
Article: Limits on a muon flux from neutralino annihilations in the sun with the IceCube 22-string detector.
[show abstract] [hide abstract]
ABSTRACT: A search for muon neutrinos from neutralino annihilations in the Sun has been performed with the IceCube 22-string neutrino detector using data collected in 104.3 days of live time in 2007. No excess over the expected atmospheric background has been observed. Upper limits have been obtained on the annihilation rate of captured neutralinos in the Sun and converted to limits on the weakly interacting massive particle (WIMP) proton cross sections for WIMP masses in the range 250-5000 GeV. These results are the most stringent limits to date on neutralino annihilation in the Sun.Physical Review Letters 06/2009; 102(20):201302. · 7.37 Impact Factor -
Article: Search for point sources of high energy neutrinos with final data from AMANDA-II
Physical Review D 03/2009; 79:062001. · 4.56 Impact Factor -
Article: Multifragmentation and the phase transition: A systematic study of the multifragmentation of 1AGeV Au, La, and Kr
[show abstract] [hide abstract]
ABSTRACT: A systematic analysis of multifragmentation (MF) in fully reconstructed events from 1AGeV Au, La, and Kr collisions with C has been performed. These data are used to provide a definitive test of the variable volume version of the statistical multifragmentation model (SMM). A single set of SMM parameters directly determined by the data and the semi-empirical mass formula are used after the adjustable inverse level density parameter ε0 is determined by the fragment distributions. The results from SMM for second stage multiplicity, size of the biggest fragment, and the intermediate mass fragments are in excellent agreement with the data. Multifragmentation thresholds have been obtained for all three systems using SMM prior to secondary decay. The data indicate that both thermal excitation energy Eth* and the isotope ratio temperature THe-DT decrease with increase in system size at the critical point. The breakup temperature obtained from SMM also shows the same trend as seen in the data. The SMM model is used to study the nature of the MF phase transition. The caloric curve for Kr exhibits back-bending (finite latent heat) while the caloric curves for Au and La are consistent with a continuous phase transition (nearly zero latent heat) and the values of the critical exponents τ, β, and γ, both from data and SMM, are close to those for a “liquid-gas” system for Au and La. We conclude that the larger Coulomb expansion energy in Au and La reduces the latent heat required for MF and changes the nature of the phase transition. Thus the Coulomb energy plays a major role in nuclear MF.Phys. Rev. C. 05/2002; 65(5). -
Article: Comparison of 1AGeV 197Au+C data with thermodynamics: The nature of the phase transition in nuclear multifragmentation
[show abstract] [hide abstract]
ABSTRACT: Multifragmentation MF results from 1AGeV Au on C have been compared with the Copenhagen statistical multifragmentation model (SMM). The complete charge, mass, and momentum reconstruction of the Au projectile was used to identify high momentum ejectiles leaving an excited remnant of mass A, charge Z, and excitation energy E* which subsequently multifragments. Measurement of the magnitude and multiplicity (energy) dependence of the initial free volume and the breakup volume determines the variable volume parametrization of SMM. Very good agreement is obtained using SMM with the standard values of the SMM parameters. A large number of observables, including the fragment charge yield distributions, fragment multiplicity distributions, caloric curve, critical exponents, and the critical scaling function are explored in this comparison. The two stage structure of SMM is used to determine the effect of cooling of the primary hot fragments. Average fragment yields with Z>~3 are essentially unaffected when the excitation energy is ⩽7 MeV/nucleon. SMM studies suggest that the experimental critical exponents are largely unaffected by cooling and event mixing. The nature of the phase transition in SMM is studied as a function of the remnant mass and charge using the microcanonical equation of state. For light remnants A<~100, backbending is observed indicating negative specific heat, while for A>~170 the effective latent heat approaches zero. Thus for heavier systems this transition can be identified as a continuous thermal phase transition where a large nucleus breaks up into a number of smaller nuclei with only a minimal release of constituent nucleons. Z<~2 particles are primarily emitted in the initial collision and after MF in the fragment deexcitation process.Phys. Rev. C. 09/2001; 64(5). -
Article: Mass dependence of the transverse momenta of Au projectile fragments at 1.0A GeV
[show abstract] [hide abstract]
ABSTRACT: The transverse momenta (px,py) of projectile fragments produced by 1.0A GeV 197Au nuclei incident on Au and C targets have been measured. The medium and heavy fragments have px and py distributions, which are wider than predicted by models. For the Au target the widths of the distributions are significantly larger than those for C, particularly for the heavy fragments. The C distributions show a different gross structure, which may be due to the target-projectile size difference.Phys. Rev. C. 06/2001; 64(1). -
Article: Elliptic flow in Au+Au collisions at square root(S)NN = 130 GeV.
[show abstract] [hide abstract]
ABSTRACT: Elliptic flow from nuclear collisions is a hadronic observable sensitive to the early stages of system evolution. We report first results on elliptic flow of charged particles at midrapidity in Au+Au collisions at square root(S)NN = 130 GeV using the STAR Time Projection Chamber at the Relativistic Heavy Ion Collider. The elliptic flow signal, v2, averaged over transverse momentum, reaches values of about 6% for relatively peripheral collisions and decreases for the more central collisions. This can be interpreted as the observation of a higher degree of thermalization than at lower collision energies. Pseudorapidity and transverse momentum dependence of elliptic flow are also presented.Physical Review Letters 02/2001; 86(3):402-7. · 7.37 Impact Factor -
Article: Two-stage multifragmentation of 1A GeV Kr, La, and Au
[show abstract] [hide abstract]
ABSTRACT: Multifragmentation in fully reconstructed events from 1A GeV Kr and La collisions with C has been studied. Results are compared with similar data for 1A GeV Au+C. The emitted charged particles and fragments are identified with emission from either a prompt first stage or a second stage in which the remnant resulting from the first stage breaks up. The nuclear charge, mass, and excitation energy distributions of the remnant are determined. The total charged multiplicity, as well as those of the first and second stages are obtained. Freeze-out temperatures and thermal excitation energy permit the determination of the caloric curve. The fragment charge distribution as well as the IMF multiplicity distribution and those of individual fragments are obtained. The various results are examined as to the extent of universal behavior when scaled for varying system size. Comparisons are made with intranuclear cascade and statistical multifragmentation model calculations.Phys. Rev. C. 07/2000; 62(2). -
Article: Hardware controls for the STAR experiment at RHIC
[show abstract] [hide abstract]
ABSTRACT: A hardware controls system has been implemented for the STAR experiment at RHIC. Approximately 10000 parameters governing experiment operation are currently controlled and monitored. The system is based on the Experimental Physics and Industrial Control System (EPICS). The architecture of STAR hardware controls is presented as well as the results of operation of the integrated baseline system. Novel features of the system include a specialized field bus (High-level Data Link Control-HDLC), new EPICS record support, Control DEVice (CDEV) interfaces to accelerator and magnet control systems, and C++ based communication between STAR online and Hardware Controls and their associated databasesIEEE Transactions on Nuclear Science 05/2000; · 1.45 Impact Factor -
Article: Universality in fragment inclusive yields from Au + Au collisions
[show abstract] [hide abstract]
ABSTRACT: The inclusive light fragment (Z<~7) yield data in Au+Au reactions, measured by the EOS Collaboration at the LBNL Bevalac, are presented as a function of multiplicity. Moving from central to peripheral collisions the measured charge distributions develop progressively according to a power law which can be fitted, within errors, by a single τ exponent independently of the bombarding energy except for the data at 250A MeV. In addition, the location of the maximum in the individual yields of different charged fragments, for a given beam energy, shifts towards lower multiplicity as the fragment charge increases from Z=3 to Z=7. This trend is common to all six measured beam energies. Moments of charge distribution are also reported. The universal features observed in the present Au + Au data are consistent with previous experimental findings in the Au + C multifragmentation reaction at 1A GeV.Phys. Rev. C. 03/2000; 61(4). -
Article: Comparison of the 1A GeV197Au+C interaction with first-stage transport codes
[show abstract] [hide abstract]
ABSTRACT: The properties of the remnant resulting from the emission of prompt particles in the interaction of 1A GeV 197Au+C interactions have been compared with intranuclear cascade and Boltzmann-Uehling-Uhlenback transport calculations. The number of first-stage particles and the energy spectra of first-stage protons are also compared. Both models can fit the general but not the detailed features of the data.Physical Review C 11/1999; 60(6):64606. · 3.31 Impact Factor -
Conference Proceeding: Hardware controls for the STAR experiment at RHIC
[show abstract] [hide abstract]
ABSTRACT: A hardware controls system has been implemented for the STAR experiment at RHIC. Approximately 10000 parameters governing experiment operation are currently controlled and monitored. The system is based on the Experimental Physics and Industrial Control System (EPICS). The architecture of STAR hardware controls are presented as well as the results of operation of the integrated baseline system. Novel features of the system include a specialized field bus (High-level Data Link Control-HDLC), new EPICS record support, control DEVice (CDEV) interfaces to accelerator and magnet control systems, and C++ based communication between STAR online and hardware controls and their associated databasesReal Time Conference, 1999. Santa Fe 1999. 11th IEEE NPSS; 02/1999 -
Article: Lambda Hyperons in 2 A*GeV Ni + Cu Collisions
[show abstract] [hide abstract]
ABSTRACT: A sample of Lambda's produced in 2 A*GeV Ni + Cu collisions has been obtained with the EOS Time Projection Chamber at the Bevalac. Low background in the invariant mass distribution allows for the unambiguous demonstration of Lambda directed flow. The transverse mass spectrum at mid-rapidity has the characteristic shoulder-arm shape of particles undergoing radial transverse expansion. A linear dependence of Lambda multiplicity on impact parameter is observed, from which a total Lambda + Sigma^0 production cross section of $112 +/- 24 mb is deduced. Detailed comparisons with the ARC and RVUU models are made.08/1997; -
Article: Results from the STAR TPC system test
[show abstract] [hide abstract]
ABSTRACT: A system test of various components of the Solenoidal Tracker at RHIC (STAR) detector, operating in concert, has recently come on-line. Communication between a major sub-detector, a sector of the time projection chamber (TPC), and the trigger, data acquisition and slow controls systems has been established, enabling data from cosmic ray muons to be collected. First results from an analysis of the TPC data are presented. These include measurements of system noise, electronic parameters such as amplifier gains and pedestal values, and tracking resolution for cosmic ray muons and laser induced ionization tracks. A discussion on the experience gained in integrating the different components for the system test is also givenIEEE Transactions on Nuclear Science 07/1997; · 1.45 Impact Factor -
Conference Proceeding: Results from the STAR TPC system test
[show abstract] [hide abstract]
ABSTRACT: A system test of various components of the Solenoidal Tracker at RHIC (STAR) detector, operating in concert, has recently come on-line. Communication between a major sub-detector, a sector of the Time Projection Chamber (TPC), and the trigger, data acquisition and slow controls systems has been established, enabling data from cosmic ray muons to be collected. First results from an analysis of the TPC data are presented. These include measurements of system noise, electronic parameters such as amplifies gains and pedestal values, and tracking resolution for cosmic ray muons and laser induced ionization tracks. A discussion on the experience gained in integrating the different components for the system test is also givenNuclear Science Symposium, 1996. Conference Record., 1996 IEEE; 12/1996 -
Article: Front end electronics for the STAR TPC
[show abstract] [hide abstract]
ABSTRACT: The Solenoidal Tracker at RHIC (STAR) is a large acceptance detector now being built to study high energy heavy ion collisions. It detects charged particles with a large time projection chamber. The 136,600 TPC pads are instrumented with waveform digitizers, implemented in custom low noise preamplifier/shaper and switched capacitor array/ADCs ICs. The system is highly integrated with all analog functions mounted on small cards that plug into the TPC. Detector mounted readout boards multiplex data from 1152 channels onto a 1.5 Gbit/sec fiber optic link to the data acquisition systemIEEE Transactions on Nuclear Science 07/1996; · 1.45 Impact Factor -
Article: Observation of Collective Effects in Lambda Production at 2 GeV/nucleon
Nuclear Physics A 06/1995; 590:549-552. · 1.54 Impact Factor -
Article: Radial Flow in Au+Au Collisions at E=0.25-1.15 A GeV
[show abstract] [hide abstract]
ABSTRACT: A systematic study of energy spectra for light particles emitted at midrapidity from Au+Au collisions at E=0.25-1.15 A GeV reveals a significant non-thermal component consistent with a collective radial flow. This component is evaluated as a function of bombarding energy and event centrality. Comparisons to Quantum Molecular Dynamics (QMD) and Boltzmann-Uehling-Uhlenbeck (BUU) models are made for different equations of state. Comment: 10 pages of text and 4 figures (all ps files in a uuencoded package).02/1995; -
Conference Proceeding: Data Links For The EOS TPC
[show abstract] [hide abstract]
ABSTRACT: Not AvailableNuclear Science Symposium, 1990. Conference record : Including Sessions on Nuclear Power Systems and Medical Imaging Conference, 1990 IEEE; 11/1990 -
Article: A TPC detector for the study of high multiplicity heavy ion collisions
[show abstract] [hide abstract]
ABSTRACT: The design of a time projection chamber (TPC) detector with complete pad coverage is presented. The TPC allows the measurements of high multiplicity (~200 tracks) relativistic nucleus-nucleus collisions initiated with the heaviest, most energetic projectiles available at the LBL (Lawrence Berkeley Laboratory) BEVALAC accelerator facility. The front-end electronics, composed of over 15000 time sampling channels, is located on the chamber. The highly integrated, custom-designed electronics and the VME-based data acquisition system are describedIEEE Transactions on Nuclear Science 05/1990; · 1.45 Impact Factor -
Conference Proceeding: The HISS TPC
[show abstract] [hide abstract]
ABSTRACT: This paper discusses the design, development and application of the HISS time projection chambers. (LSP)07/1989
Top co-authors
Top Journals
Institutions
-
1990–2002
-
Lawrence Berkeley National Laboratory
- Nuclear Science Division
Berkeley, CA, USA
-
-
2000
-
University of California, Berkeley
Berkeley, CA, USA
-
-
1999–2000
-
Creighton University
- Department of Physics
Omaha, NE, USA -
Purdue University
West Lafayette, IN, USA
-
