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Articles 31 - 49 of 49
Full-Text Articles in Nuclear
Utilizing (P,D) And (P,T) Reactions To Obtain (N,F) Cross Sections In Uranium Nuclei Via The Surrogate-Ratio Method, R. O. Hughes, C. W. Beausang, T. J. Ross, J. T. Burke, N. D. Scielzo, M. S. Basunia, C. M. Campbell, R. J. Casperson, H. L. Crawford, J. Escher, J. Munson, L. Phair, J. J. Ressler
Utilizing (P,D) And (P,T) Reactions To Obtain (N,F) Cross Sections In Uranium Nuclei Via The Surrogate-Ratio Method, R. O. Hughes, C. W. Beausang, T. J. Ross, J. T. Burke, N. D. Scielzo, M. S. Basunia, C. M. Campbell, R. J. Casperson, H. L. Crawford, J. Escher, J. Munson, L. Phair, J. J. Ressler
Physics Faculty Publications
The surrogate ratio method has been tested for (p,d) and (p,t) reactions on uranium nuclei. 236U and 238U targets were bombarded with 28-MeV protons and the light ion recoils and fission fragments were detected using the Silicon Telescope Array for Reaction Studies detector array at the 88-Inch Cyclotron at Lawrence Berkeley National Laboratory. The (p,df) reaction channels on 236U and 238U targets were used as a surrogate to determine the σ[236U(n,f)]/σ[234U(n, …
Upper Limits For The Photoproduction Cross Section For The Φ−−(1860) Pentaquark State Off The Deuteron, H. Egiyan, Gerard P. Gilfoyle, Et. Al.
Upper Limits For The Photoproduction Cross Section For The Φ−−(1860) Pentaquark State Off The Deuteron, H. Egiyan, Gerard P. Gilfoyle, Et. Al.
Physics Faculty Publications
We searched for the Φ--(1860) pentaquark in the photoproduction process off the deuteron in the Ξ-π--decay channel using CLAS. The invariant-mass spectrum of the Ξ-π- system does not indicate any statistically significant enhancement near the reported mass M = 1.860 GeV. The statistical analysis of the sideband-subtracted mass spectrum yields a 90%-confidence-level upper limit of 0.7 nb for the photoproduction cross section of Φ--(1860) with a consecutive decay into Ξ-π- in the photon-energy range 4.5 GeV < Eγ < 5.5 GeV.
Boost-Invariant (2+1)-Dimensional Anisotropic Hydrodynamics, Mauricio Martinez, Radoslaw Ryblewski, Michael T. Strickland
Boost-Invariant (2+1)-Dimensional Anisotropic Hydrodynamics, Mauricio Martinez, Radoslaw Ryblewski, Michael T. Strickland
Physics and Astronomy Faculty Publications
We present results of the application of the anisotropic hydrodynamics (aHydro) framework to (2+1)-dimensional boost-invariant systems. The necessary aHydro dynamical equations are derived by taking moments of the Boltzmann equation using a momentum-space anisotropic one-particle distribution function. We present a derivation of the necessary equations and then proceed to numerical solutions of the resulting partial differential equations using both realistic smooth Glauber initial conditions and fluctuating Monte Carlo Glauber initial conditions. For this purpose we have developed two numerical implementations: one that is based on straightforward integration of the resulting partial differential equations supplemented by a two-dimensional weighted Lax-Friedrichs smoothing …
A Shell Model Study Of The High Spin States Of 88Y, M. Bunce, P. H. Regan, V. Werner, A. Anagnostatou, C. W. Beausang, M. Bowry, R. J. Casperson, D. Chen, N. Cooper, P. Goddard, R. O. Hughes, G. Ilie, P.J.R. Mason, B. Pauerstein, M. W. Reed
A Shell Model Study Of The High Spin States Of 88Y, M. Bunce, P. H. Regan, V. Werner, A. Anagnostatou, C. W. Beausang, M. Bowry, R. J. Casperson, D. Chen, N. Cooper, P. Goddard, R. O. Hughes, G. Ilie, P.J.R. Mason, B. Pauerstein, M. W. Reed
Physics Faculty Publications
Experiments were carried out at the Wright Nuclear Structure Laboratory at Yale University using the 21MV ESTU Tandem Van de Graaff accelerator with the purpose of studying 88Y. A beam of 18O impinged at laboratory energies of 60, 65 and 70 MeV on a 600 μg/cm 2 74Ge target with a thick (10mg/cm 2) 197Au backing. This experiment was performed with the specific aim of accessing medium spin states of the nucleus of interest. A second experiment was undertaken to populate the nucleus of interest in higher spin states by impinging the same 18 …
To The Continuum And Beyond: Structure Of U Nuclei, R. O. Hughes, C. W. Beausang, T. J. Ross, J. T. Burke, N. D. Scielzo, M. S. Basunia, C. M. Campbell, R. J. Casperson, H. L. Crawford, J. Munson, L. Phair, J. J. Ressler
To The Continuum And Beyond: Structure Of U Nuclei, R. O. Hughes, C. W. Beausang, T. J. Ross, J. T. Burke, N. D. Scielzo, M. S. Basunia, C. M. Campbell, R. J. Casperson, H. L. Crawford, J. Munson, L. Phair, J. J. Ressler
Physics Faculty Publications
An experiment was performed at the 88-inch cyclotron at LBNL to investigate the structure of uranium isotopes and concurrently test the so-called surrogate ratio method. A 28 MeV proton beam was used to bombard 236U and 238U targets and the outgoing light ions were detected using the STARS silicon telescope allowing isotopic assignments and the excitation energy of the compound nucleus to be measured. A fission detector was placed at backward angles to give particle-fission coincidences, while the six clover germanium detectors of the LIBERACE array were used for particle-γ coincidences. The (p,d) reaction channels on 236U …
Observation Of A Narrow Structure In 1H(Ykso)X Via Interference With Φ-Meson Production, M. J. Amaryan, G. Gavalian, C. Nepali, M. V. Polyakov, W. J. Briscoe, G. E. Dodge, C. E. Hyde, F. Klein, V. Kuznetsov, I. Strakovsky, J. Zhang
Observation Of A Narrow Structure In 1H(Ykso)X Via Interference With Φ-Meson Production, M. J. Amaryan, G. Gavalian, C. Nepali, M. V. Polyakov, W. J. Briscoe, G. E. Dodge, C. E. Hyde, F. Klein, V. Kuznetsov, I. Strakovsky, J. Zhang
Physics Faculty Publications
We report observation of a narrow peak structure at ~1.54 GeV with a Gaussian width σ = 6 MeV in the missing mass of KS in the reaction γ+p → pKSKL. The observed structure may be due to the interference between a strange (or antistrange) baryon resonance in the pKL system and the φ(KSKL) photoproduction leading to the same final state. The statistical significance of the observed excess of events estimated as the log-likelihood ratio of the resonant signal + background hypothesis and the φ-production-based background-only hypothesis …
Comparison Of Forward And Backward Pp Pair Knockout In 3He(E,E'Pp)N, H. Baghdasaryan, L. B. Weinstein, J. M. Laget, K. P. Adhikari, M. Aghasyan, M. J. Amaryan, M. Anghinolfi, J. Ball, M. Battaglieri, A. S. Biselli, G. Dodge, C. E. Hyde, S. E. Kuhn, H. Seraydaryan
Comparison Of Forward And Backward Pp Pair Knockout In 3He(E,E'Pp)N, H. Baghdasaryan, L. B. Weinstein, J. M. Laget, K. P. Adhikari, M. Aghasyan, M. J. Amaryan, M. Anghinolfi, J. Ball, M. Battaglieri, A. S. Biselli, G. Dodge, C. E. Hyde, S. E. Kuhn, H. Seraydaryan
Physics Faculty Publications
Measuring nucleon-nucleon short range correlations (SRCs) has been a goal of the nuclear physics community for many years. They are an important part of the nuclear wave function, accounting for almost all of the high-momentum strength. They are closely related to the EMC effect. While their overall probability has been measured, measuring their momentum distributions is more difficult. In order to determine the best configuration for studying SRC momentum distributions, we measured the 3He(e,e'pp)n reaction, looking at events with high-momentum protons (pp > 0.35 GeV/c) and a low-momentum neutron (p …
Evidence For The Onset Of Color Transparency In Ρ0 Electroproduction Off Nuclei, L. El Fassi, L. Zana, H. Hafidi, M. Holtrop, B. Mustapha, W. K. Brooks, H. Hakobyan, Z. Zheng, K. P. Adhikari, D. Adikaram, M. J. Amaryan, H. Baghdasaryan, S. Bültmann, G. E. Dodge, C. E. Hyde, A. Klein, S. E. Kuhn, M. Mayer, H. Seraydaryan, L. B. Weinstein
Evidence For The Onset Of Color Transparency In Ρ0 Electroproduction Off Nuclei, L. El Fassi, L. Zana, H. Hafidi, M. Holtrop, B. Mustapha, W. K. Brooks, H. Hakobyan, Z. Zheng, K. P. Adhikari, D. Adikaram, M. J. Amaryan, H. Baghdasaryan, S. Bültmann, G. E. Dodge, C. E. Hyde, A. Klein, S. E. Kuhn, M. Mayer, H. Seraydaryan, L. B. Weinstein
Physics Faculty Publications
We have measured the nuclear transparency of the incoherent diffractive A( e , e ′ ρ0 ) process in 12C and 56Fe targets relative to 2H using a 5 GeV electron beam. The nuclear transparency, the ratio of the produced ρ0 ʼs on a nucleus relative to deuterium, which is sensitive to ρA interaction, was studied as function of the coherence length (lc), a lifetime of the hadronic fluctuation of the virtual photon, and the four-momentum transfer squared (Q2). While the transparency for both 12C and 56Fe …
Anomalous Centrality Evolution Of Two-Particle Angular Correlations From Au-Au Collisions At √ˢᴺᴺ = 62 And 200 Gev, G. Agakishiev, M. M. Aggarwal, S. Bueltmann, I. Koralt, D. Plyku, Star Collaboration
Anomalous Centrality Evolution Of Two-Particle Angular Correlations From Au-Au Collisions At √ˢᴺᴺ = 62 And 200 Gev, G. Agakishiev, M. M. Aggarwal, S. Bueltmann, I. Koralt, D. Plyku, Star Collaboration
Physics Faculty Publications
We present two-dimensional (2D) two-particle angular correlations measured with the STAR detector on relative pseudorapidity η and ϕ for charged particles from Au-Au collisions at √ˢᴺᴺ = 62 and 200 GeV with transverse momentum pt ≥ 0.15 GeV/c, │η│ ≤ 1, and 2 π in azimuth. Observed correlations include a same-side (relative azimuth <π/2) 2D peak, a closely related away-side azimuth dipole, and an azimuth quadrupole conventionally associated with elliptic flow. The same-side 2D peak and away-side dipole are explained by semihard parton scattering and fragmentation (minijets) in proton-proton and peripheral nucleus-nucleus collisions. Those structures follow N-N binary-collision scaling in Au-Au collisions until midcentrality, where a transition to a qualitatively different centrality trend occurs within one 10% centrality bin. Above the transition point the number of same-side and away-side correlated pairs increases rapidly relative to binary-collision scaling, the η width of the same-side 2D peak also increases rapidly (η elongation), and the ϕ width actually decreases significantly. Those centrality trends are in marked contrast with conventional expectations for jet quenching in a dense medium. The observed centrality trends are compared to perturbative QCD predictions computed in HIJING, which serve as a theoretical baseline, and to the expected trends for semihard parton scattering and fragmentation in a thermalized opaque medium predicted by theoretical calculations and phenomenological models. We are unable to reconcile a semihard parton scattering and fragmentation origin for the observed correlation structure and centrality trends with heavy-ion collision scenarios that invoke rapid parton thermalization. If the collision system turns out to be effectively opaque to few-GeV partons the present observations would be inconsistent with the minijet picture discussed here.
Energy And System Size Dependence Of Two- And Four-Particle Ν2 Measurements In Heavy-Ion Collisions At √ˢᴺᴺ = 62.4 And 200 Gev And Their Implications On Flow Fluctuations And Nonflow, G. Agakishiev, M. M. Aggarwal, Z. Ahammed, A. V. Alakhverdyants, M. Bueltmann, Star Collaboration
Energy And System Size Dependence Of Two- And Four-Particle Ν2 Measurements In Heavy-Ion Collisions At √ˢᴺᴺ = 62.4 And 200 Gev And Their Implications On Flow Fluctuations And Nonflow, G. Agakishiev, M. M. Aggarwal, Z. Ahammed, A. V. Alakhverdyants, M. Bueltmann, Star Collaboration
Physics Faculty Publications
We present STAR measurements of azimuthal anisotropy by means of the two- and four-particle cumulants ν2 ν2{2} and ν2{4}) for Au + Au and Cu + Cu collisions at center-of-mass energies √ˢᴺᴺ = 62.4 and 200 GeV. The difference between ν2{2}2 and ν2{4}2 is related to ν2fluctuations (σν2) and nonflow (δ2). We present an upper limit to σν2/ν2. Following the assumption that eccentricity fluctuations σε dominate ν2 fluctuations σν2/ν2 ≈ σε/ε we …
Directed And Elliptic Flow Of Charged Particles In Cu + Cu Collisions At √ˢᶰᶰ =22.4 Gev, G. Agakishiev, M. M. Aggarwal, S. Bueltmann, I. Koralt, X. Zhu, Star Collaboration
Directed And Elliptic Flow Of Charged Particles In Cu + Cu Collisions At √ˢᶰᶰ =22.4 Gev, G. Agakishiev, M. M. Aggarwal, S. Bueltmann, I. Koralt, X. Zhu, Star Collaboration
Physics Faculty Publications
This paper reports results for directed flow v1 and elliptic flow v2 of charged particles in Cu + Cu collisions at √ˢᶰᶰ = 22.4 GeV at the Relativistic Heavy Ion Collider. The measurements are for the 0-60% most central collisions, using charged particles observed in the STAR detector. Our measurements extend to 22.4-GeV Cu + Cu collisions the prior observation that v1 is independent of the system size at 62.4 and 200 GeV and also extend the scaling of v1 with η/ybeam to this system. The measured v2pT in Cu + Cu …
Di-Electron Spectrum At Mid-Rapidity In P+P Collisions At √S=200 Gev, L. Adamczyk, S. Bueltmann, I. Koralt, D. Plyku, Y. Zoulkarneeva, Star Collaboration
Di-Electron Spectrum At Mid-Rapidity In P+P Collisions At √S=200 Gev, L. Adamczyk, S. Bueltmann, I. Koralt, D. Plyku, Y. Zoulkarneeva, Star Collaboration
Physics Faculty Publications
We report on the mid-rapidity mass spectrum of di-electrons and cross sections of pseudoscalar and vector mesons via e+e- decays, from √s = 200 GeV p + p collisions, measured by the large-acceptance experiment STAR at the Relativistic Heavy Ion Collider. The ratio of the di-electron continuum to the combinatorial background is larger than 10% over the entire mass range. Simulations of di-electrons from light-meson decays and heavy-flavor decays (charmonium and open charm correlation) are found to describe the data. The extracted ω → e+e- invariant yields are consistent with previous measurements. The mid-rapidity …
Virtual Compton Scattering And The Generalized Polarizabilities Of The Proton At Q2 = 0.92 And 1.76 Gev2, H. Fonvielle, G. Laveissiere, N. Degrande, C. Jutier, L. Todor, G. E. Dodge, C. E. Hyde, K. Mccormick, P. E. Ulmer, L. B. Weinstein
Virtual Compton Scattering And The Generalized Polarizabilities Of The Proton At Q2 = 0.92 And 1.76 Gev2, H. Fonvielle, G. Laveissiere, N. Degrande, C. Jutier, L. Todor, G. E. Dodge, C. E. Hyde, K. Mccormick, P. E. Ulmer, L. B. Weinstein
Physics Faculty Publications
Virtual Compton scattering (VCS) on the proton has been studied at the Jefferson Laboratory using the exclusive photon electroproduction reaction ep → epγ. This paper gives a detailed account of the analysis which has led to the determination of the structure functions PLL − PTT/ε and PLT and the electric and magnetic generalized polarizabilities (GPs) αE(Q2)and βM(Q2) at values of the four-momentum transfer squared Q2 = 0.92 and 1.76 GeV2. These data, together with the results of VCS experiments at lower momenta, help building a …
System Size And Energy Dependence Of Near-Side Dihadron Correlations, G. Agakishiev, M. M. Aggarwal, Z. Ahammed, A. V. Alakhverdyants, I. Alekseev, J. Alford, B. D. Anderson, C. D. Anson, S. Bueltmann, I. Koralt, D. Plyku
System Size And Energy Dependence Of Near-Side Dihadron Correlations, G. Agakishiev, M. M. Aggarwal, Z. Ahammed, A. V. Alakhverdyants, I. Alekseev, J. Alford, B. D. Anderson, C. D. Anson, S. Bueltmann, I. Koralt, D. Plyku
Physics Faculty Publications
Two-particle azimuthal (Δφ) and pseudorapidity (Δη) correlations using a trigger particle with large transverse momentum (PT)in d+Au, Cu+Cu, and Au+Au collisions at √ sNN = 62.4 GeV and 200 GeV from the STAR experiment at the Relativistic Heavy Ion Collider are presented. The near-side correlation is separated into a jet-like component, narrow in both Δφ and Δη, and the ridge, narrow in Δφ but broad in Δη. Both components are studied as a function of collision centrality, and the jet-like correlation is studied as a function of the trigger and associated PT. The behavior of the …
Measurement Of Exclusive Πº Electroproduction Structure Functions And Their Relationship To Transverse Generalized Parton Distributions, Clas Collaboration, K. P. Adhikari, M. J. Amaryan, R. P. Bennett, S. Koirala, S. E. Kuhn, M. Mayer, L. B. Weinstein, I. Bedlinsky, V. Kubarovsky
Measurement Of Exclusive Πº Electroproduction Structure Functions And Their Relationship To Transverse Generalized Parton Distributions, Clas Collaboration, K. P. Adhikari, M. J. Amaryan, R. P. Bennett, S. Koirala, S. E. Kuhn, M. Mayer, L. B. Weinstein, I. Bedlinsky, V. Kubarovsky
Physics Faculty Publications
Exclusive π0 electroproduction at a beam energy of 5.75 GeV has been measured with the Jefferson Lab CLAS spectrometer. Differential cross sections were measured at more than 1800 kinematic values in Q2, xB , t , and ϕπ , in the Q2 range from 1.0 to 4.6 GeV2 , −t up to 2 GeV2 , and xB from 0.1 to 0.58. Structure functions σT+ϵσL , σTT , and σLT were extracted as functions of t for each of 17 combinations of Q2 and xB . …
Comment On “Observation Of A Narrow Structure In 1H(Γ,KS0)X Via Interference With Φ-Meson Production”, M. Anghinolfi, Gerard P. Gilfoyle, Et. Al.
Comment On “Observation Of A Narrow Structure In 1H(Γ,KS0)X Via Interference With Φ-Meson Production”, M. Anghinolfi, Gerard P. Gilfoyle, Et. Al.
Physics Faculty Publications
In Ref. [1], the authors claim to observe a narrow structure in the mass spectrum constructed from the (pKL) system using data from the CLAS detector. The interpretation of this narrow structure given in Ref. [1] is as follows: “It may be due to the photoproduction of the Θ+pentaquark or some unknown Σ* resonance.” The authors go on to say that “it is unlikely for the observed structure to be due to a Σ* resonance.”
Hrc Enews — 2012 Winter, Megan M. Iudice
Hrc Enews — 2012 Winter, Megan M. Iudice
Publications (HRC)
This issue contains staff accomplishments and announcements, event listings, and a "new faces" listing for new staff, affiliates, and researchers.
Inclusive Charged Hadron Elliptic Flow In Au + Au Collisions At √ˢᴺᴺ = 7.7-39 Gev, L. Adamczyk, G. Agakishiev, S. Bültmann, I Koralt, D. Plyku, Star Collaboration
Inclusive Charged Hadron Elliptic Flow In Au + Au Collisions At √ˢᴺᴺ = 7.7-39 Gev, L. Adamczyk, G. Agakishiev, S. Bültmann, I Koralt, D. Plyku, Star Collaboration
Physics Faculty Publications
A systematic study is presented for centrality, transverse momentum pT, and pseudorapidity (η) dependence of the inclusive charged hadron elliptic flow v2 at midrapidity (|η| < 1.0) in Au + Au collisions at √ˢᴺᴺ = 7.7, 11.5, 19.6, 27, and 39 GeV. The results obtained with different methods, including correlations with the event plane reconstructed in a region separated by a large pseudorapidity gap and four-particle cumulants (v2{4}), are presented to investigate nonflow correlations and v2 fluctuations. We observe that the difference between v2{2} and v2{4} is smaller at the lower collision energies. Values of v2, scaled by the initial coordinate space eccentricity, v2/ϵ, as a function of pT are larger in more central collisions, suggesting stronger collective flow develops in more central collisions, similar to the results …
Ρ0 Photoproduction In Auau Collisions At √ Snn = 62.4 Gev Measured With The Star Detector, G. Agakishiev, M. M. Aggarwal, Z. Ahammed, A. V. Alakhverdyants, I. Alekseev, J. Alford, B. D. Anderson, C. D. Anson, D. Arkhipkin, S. Bueltmann, I. Koralt, D. Plyku
Ρ0 Photoproduction In Auau Collisions At √ Snn = 62.4 Gev Measured With The Star Detector, G. Agakishiev, M. M. Aggarwal, Z. Ahammed, A. V. Alakhverdyants, I. Alekseev, J. Alford, B. D. Anderson, C. D. Anson, D. Arkhipkin, S. Bueltmann, I. Koralt, D. Plyku
Physics Faculty Publications
Vector mesons may be photoproduced in relativistic heavy-ion collisions when a virtual photon emitted by one nucleus scatters from the other nucleus, emerging as a vector meson. The STAR Collaboration has previously presented measurements of coherent ρ0 photoproduction at center of mass energies of 130 GeV and 200 GeV in AuAu collisions. Here, we present a measurement of the cross section at 62.4 GeV; we find that the cross section for coherent ρ0 photoproduction with nuclear breakup is 10.5 ± 1.5 ± 1.6mb at 62.4 GeV. The cross-section ratio between 200 GeV and 62.4 GeV is 4.4 ± 0.6, …