A. C. Mignerey

Molybdenum disulfide (MoS2 ) is a promising anode for high performance sodium-ion batteries due to high specific capacity, abundance, and low cost. However, poor cycling stability, low rate capability and unclear electrochemical reaction mechanism are the main challenges for MoS2 anode in Na-ion batteries. In this study, molybdenum disulfide/carbon (MoS2 /C) nanospheres are fabricated and used for Na-ion battery anodes. MoS2 /C nanospheres deliver a reversible capacity of 520 mAh g(-1) at 0.1 C and maintain at 400 mAh g(-1) for 300 cycles at a high current density of 1 C, demonstrating the best cycling performance of MoS2 for Na-ion batteries to date. The high capacity is attributed to the short ion and electron diffusion pathway, which enables fast charge transfer and low concentration polarization. The stable cycling performance and high coulombic efficiency (∼100%) of MoS2 /C nanospheres are ascribed to (1) highly reversible conversion reaction of MoS2 during sodiation/desodiation as evidenced by ex-situ X-ray diffraction (XRD) and (2) the formation of a stable solid electrolyte interface (SEI) layer in fluoroethylene carbonate (FEC) based electrolyte as demonstrated by fourier transform infrared spectroscopy (FTIR) measurements.

Tin disulfide (SnS2) has emerged as a promising anode material for sodium ion batteries (NIBs) due to its unique layered structure, high theoretical capacity, and low cost. Conventional SnS2 nanomaterials are normally synthesized using hydrothermal method, which is time-consuming and difficult to scale up for mass production. In this study, we develop a simple solid-state reaction method, in which the carbon-coated SnS2 (SnS2/C) anode materials were synthesized by annealing metallic Sn, sulfur powder, and polyacrylonitrile in a sealed vacuum glass tube. The SnS2/C nanospheres with unique layered structure exhibit a high reversible capacity of 660 mAh g(-1) at a current density of 50 mA g(-1) and maintain at 570 mAh g(-1) for 100 cycles with a degradation rate of 0.14% per cycle, demonstrating one of the best cycling performances in all reported SnS2/C anodes for NIBs to date. The superior cycling stability of SnS2/C electrode is attributed to the stable nanosphere morphology and structural integrity during charge/discharge cycles as evidenced by ex situ characterization.

The rates and mechanisms of hydrogen peroxide (H2O2) decomposition were examined in a series of soil suspensions at H2O2 concentrations comparable to those found in rainwaters. The formation of hydroxyl radical (OH) as a possible decomposition intermediate was investigated using a new, highly sensitive method. In surface soils with higher organic matter or manganese content, H2O2 usually decayed rapidly, with disproportionation to water and dioxygen dominating the decomposition, whereas the formation of the hydroxyl radical (OH) represented <10% of the total H2O2 decomposed. In contrast, for soils with lower organic matter content, H2O2 usually decayed much more slowly, but OH was a major product of the H2O2 decomposed. The decomposition was principally associated with soil particles, not the soil supernatant. Different sterilization techniques indicated that decomposition of H2O2 was at least partly due to biological activity. Because the loss of H2O2 can largely be accommodated by the production of O2 and OH within these soils, our results suggest that disproportionation through a catalase-type mechanism and the production of OH through a Haber-Weiss mechanism represent the principal routes through which H2O2 is lost.

The PHOBOS experiment has measured the charged particle multiplicity at midrapidity in Au+Au collisions at sNN=200 GeV as a function of the collision centrality. Results on dNch/dη||η|<1 divided by the number of participating nucleon pairs 〈Npart〉/2 are presented as a function of 〈Npart〉. As was found from similar data at sNN=130 GeV, the data can be equally well described by parton saturation models and two-component fits, which include contributions that scale as Npart and the number of binary collisions Ncoll. We compare the data at the two energies by means of the ratio R200/130 of the charged particle multiplicity for the two different energies as a function of 〈Npart〉. For events with 〈Npart〉>100, we find that this ratio is consistent with a constant value of 1.14±0.01(stat)±0.05(syst). Received 10 January 2002DOI:https://doi.org/10.1103/PhysRevC.65.061901©2002 American Physical Society

We present transverse momentum distributions of charged hadrons produced in Au+Au collisions at sNN=200 GeV. The spectra were measured for transverse momenta pT from 0.25 to 4.5 GeV/c in a pseudorapidity range of 0.2<η<1.4. The evolution of the spectra is studied as a function of collision centrality, from 65 to 344 participating nucleons. The results are compared to data from proton–antiproton collisions and Au+Au collisions at lower RHIC energies. We find a significant change of the spectral shape between proton–antiproton and semi-peripheral Au+Au collisions. Comparing semi-peripheral to central Au+Au collisions, we find that the yields at high pT exhibit approximate scaling with the number of participating nucleons, rather than scaling with the number of binary collisions.

Mid-rapidity spectra and yields of K$^-$ and K$^+$ have been measured for Au+Au collisions at 4, 6, 8, and 10.7 AGeV. The K$^-$ yield increases faster with beam energy than for K$^+$ and hence the K$^-$/K$^+$ ratio increases with beam energy. This ratio is studied as a function of both $\sqrt{s}$ and $\sqrt{s}$-$\sqrt{s_{th}}$ which allows the direct comparison of the kaon yields with respect to the production threshold in p+p reactions. For equal $\sqrt{s}$ - $\sqrt{s_{th}}$ the measured ratio K$^-$/K$^+$=0.2 at energies above threshold in contrast to the K$^-$/K$^+$ ratio of near unity observed at energies below threshold. The use of the K$^-$/K$^+$ ratio to test the predicted changes of kaon properties in dense nuclear matter is discussed.

This paper describes the measurement of collective flow for charged particles in Au+Au collisions at sqrt[s(NN)]=130 GeV using the PHOBOS detector at the Relativistic Heavy Ion Collider (RHIC). The measured azimuthal hit anisotropy is presented over a wide range of pseudorapidity (-5.0<eta<5.3) for the first time at this energy. The result, averaged over momenta and particle species, is observed to reach 7% for peripheral collisions at midrapidity, falling off with centrality and increasing |eta|. These results call into question the common assumption of longitudinal boost invariance over a large region of rapidity in RHIC collisions.

We present the first measurement of the pseudorapidity density of primary charged particles in Au+Au collisions at root square[s(NN)] = 200 GeV. For the 6% most central collisions, we obtain dN(ch)/d(eta)/(/eta/<1) = 650+/-35(syst). Compared to collisions at root square[s(NN)] = 130 GeV, the highest energy studied previously, an increase by a factor of 1.14+/-0.05 at 90% confidence level, is found. The energy dependence of the pseudorapidity density is discussed in comparison with data from proton-induced collisions and theoretical predictions.

This manuscript contains a detailed description of the PHOBOS experiment as it is configured for the Year 2001 running period. It is capable of detecting charged particles over the full solid angle using a multiplicity detector and measuring identified charged particles near mid-rapidity in two spectrometer arms with opposite magnetic fields. Both of these components utilize silicon pad detectors for charged particle detection. The minimization of material between the collision vertex and the first layers of silicon detectors allows for the detection of charged particles with very low transverse momenta, which is a unique feature of the PHOBOS experiment. Additional detectors include a time-of-flight wall which extends the particle identification range for one spectrometer arm, as well as sets of scintillator paddle and Cherenkov detector arrays for event triggering and centrality selection.

A systematic study of the spectra and yields of ${K}^{+}$ and ${K}^{\ensuremath{-}}$ is reported by experiment E866 as a function of centrality in Au+Au collisions at $11.6A \mathrm{GeV}/c.$ The invariant transverse spectra for both kaon species are well described by exponentials in ${m}_{t},$ with inverse slope parameters that are largest at midrapidity and which increase with centrality. The inverse slopes of the ${K}^{+}$ spectra are slightly larger than the inverse slopes of the ${K}^{\ensuremath{-}}$ spectra. The kaon rapidity density peaks at midrapidity with the ${K}^{+}$ distribution wider in rapidity than ${K}^{\ensuremath{-}}.$ The integrated total yields of ${K}^{+}$ and ${K}^{\ensuremath{-}}$ increase nonlinearly and steadily with the number of projectile participants. The yield per participant for kaons is two to three times larger than the yield from $N\ensuremath{-}N$ collisions. This enhancement suggests that the majority of kaons in central Au+Au reactions are produced in secondary hadronic collisions. There is no evidence for an onset of additional kaon production from a possible small volume of baryon-rich quark-gluon plasma. The differences between ${K}^{+}$ and ${K}^{\ensuremath{-}}$ rapidity distributions and transverse spectra are consistent with a lower phase space for ${K}^{\ensuremath{-}}$ production due to a higher energy threshold. These differences also exclude simple thermal models that assume emission from a common equilibrated system.

Flexible and transparent electronics play a predominant role in the next-generation electrical devices. In this study, a printable aqueous graphene oxide (GO) ink that enables direct deposition of GO onto flexible glass substrates is demonstrated and its application on fabricating a transparent, conductive, and flexible glass device by solution coating process is investigated as well. A uniform GO layer is formed on the flexible glass through Meyer-rod coating followed by an annealing process to reduce GO into graphene. The obtained thermally reduced graphene oxide (RGO) flexible glass has a transmittance of over 40%, as well as a sheet resistance of ~ 5 × 103 Ω/sq. In addition, a defrosting window fabricated from the RGO coated flexible glass is demonstrated, which shows excellent defrosting performance.

We present results on two-particle angular correlations in proton-proton collisions at center-of-mass energies of 200 and 410 GeV. The PHOBOS experiment at the BNL Relativistic Heavy Ion Collider has a uniquely large coverage for charged particles, giving the opportunity to explore the correlations at both short- and long-range scales. At both energies, a complex two-dimensional correlation structure in Δη and Δϕ is observed. In the context of an independent cluster model of short-range correlations, the cluster size and its decay width are extracted from the two-particle pseudorapidity correlation function and compared with previous measurements in proton-proton and proton-antiproton collisions, as well as PYTHIA and HIJING predictions.3 MoreReceived 6 April 2007DOI:https://doi.org/10.1103/PhysRevC.75.054913©2007 American Physical Society

The impact parameter dependence of the disappearance of directed transverse flow has been investigated for $^{40}\mathrm{Ar}$+$^{45}\mathrm{Sc}$ reactions using the Michigan State University $4\ensuremath{\pi}$ Array upgraded with the High Rate Array (HRA). The energy at which collective transverse flow in the reaction plane disappears, the balance energy (${E}_{\mathrm{bal}}$), is found to increase approximately linearly as a function of impact parameter. Comparison of our measured values of ${E}_{\mathrm{bal}}(b)$ shows agreement with predictions of Quantum Molecular Dynamics (QMD) model calculations.

The extraction of source radii from heavy-ion collisions using coalescence models is explored. A new prescription is presented which considers nucleosynthesis via the coalescence of fragments which is, in particular, more appropriate for intermediate-energy collisions than the previous nucleon coalescence prescriptions. This fragment coalescence model provides an avenue for viewing the breakup stage of heavy-ion reactions that yields valuable complimentary information to two-nucleon and two-fragment correlation measurements. This model was applied to recent experimental data on central 55 and 115 MeV/nucleon $^{40}\mathrm{Ar}$${+}^{45}$Sc collisions studied at midrapidity. Source radii are presented versus the transverse velocity for six different coalescence channels leading to charge one, two, and three fragments. Particular attention is paid to the temperature input in the model, as the extracted radii depend significantly on this parameter. A means of extracting the temperature from experimental data using the present model is described. Comparisons to the two temperature-dependent nucleon coalescence models will also be discussed.

Two-pion correlation functions are analyzed at midrapidity for three systems (14.6AGeV/c Si+Al, Si+Au, and 11.6AGeV/c Au+Au), seven distinct centrality conditions, and different kT bins in the range 0.1–0.5 GeV/c. Source reference frames are determined from fits to the Yano-Koonin source parametrization. Bertsch-Pratt radius parameters are shown to scale linearly with both number of projectile and total participants as obtained from a Glauber model calculation. A finite lifetime parameter that increases linearly with system/centrality is also reported. The mT dependences of the Bertsch-Pratt radii for the central Si+Au and central Au+Au systems differ only by an overall normalization factor given by the measured system/centrality dependence.Received 2 April 2002DOI:https://doi.org/10.1103/PhysRevC.66.054906©2002 American Physical Society

The Aquia aquifer (southern Maryland) contains a remarkably smooth Cl − profile (0.46–3.23 ppm) along its flow path. This is interpreted as a record of historic changes in the deposition of Cl − in this region. Those changes have been influenced by the rise and fall of sea level, which has altered the distance of the recharge region from the coastline by ∼200 km. The 36 Cl concentration along the flow path is not as smooth as the Cl − profile. Historic variations in cosmogenic production, atmospheric transport, precipitation, and evapotranspiration all might have influenced 36 Cl concentrations. A general similarity between the 36 Cl and Cl − profiles suggests that changes in precipitation and evapotranspiration rates, which influence both tracers similarly, are particularly important. To reconcile 14 C, 36 Cl, and hydrologic data, we propose a two‐tier model for flow in the Aquia. Shallower portions of the aquifer (&lt;60 m) were subjected to hydraulic gradients and flow rates approximately 5 times larger during the Pleistocene than modern, prepumping rates. At greater depths, flow rates were much slower and less variable; water in this region may be old enough to record some 36 Cl decay.

The Aquia (Paleocene) and Magothy (Late Cretaceous) Formations of the Atlantic Coastal Plain represent two well-characterized (hydrodynamically and geochemically) aquifers in southern Maryland. 14 C measurements of the dissolved organic (DOC) and inorganic carbon (DIC) of Aquia and Magothy groundwaters have been made using accelerator mass spectrometry (AMS). Both DI 14 C and DO 14 C concentrations in the initial flow path are unexpectedly low. As the water progresses farther from the recharge area, the DI 14 C percent modern carbon (pMC) is consistently lower than the DO 14 C pMC; this difference stays constant for all samples. The 14 C-derived ages for an Aquia water sample downgradient at Site 4 are 17 ka and 12 ka for DI 14 C and DO 14 C, respectively. Radiocarbon ages have been compared to ages determined by two other independent dating methods: computer-simulated hydrodynamic modeling and age estimates based on changes in Cl − , 18 O and 2 H distributions, which are interpreted to be influenced by sea level and climate.

Procedures are described to identify simultaneously the mass and charge of projectile-like fragments produced in damped heavy-ion reactions and derived from data recorded with a ΔE−E time-of-flight telescope. Corrections for the effects of particle emission from the primary reaction products are also discussed. The average properties of the resultant charge, neutron and mass distributions can be described by six parameters obtained from a two-dimensional Gaussian fit. These parameters, which are a function of kinetic energy damping, summarize the properties of nucleon exchange in the damped process. After the effects of experimental resolution (in two dimensions, charge and mass) and the effects of binning of the data have been taken into account, most physically relevant quantities of interest and their uncertainties can be calculated with the formulas presented.

A technique is described to quickly measure the response of detectors to intermediate-energy heavy ions. An ECR source was utilized to produce ions as heavy as krypton. A series of ions with the same charge-to-mass ratio was accelerated in a cyclotron to a constant velocity of energy/nucleon. Different ion species were extracted by adjusting the resonant frequency a few kHz. Detectors were directly exposed to the extracted beams. For a charge-to-mass ratio of one-quarter, over seventeen ion species from 4He+1 to 84Kr+21 were observed in a two hour period.

The observation of new neutron-rich isotopes of $^{52\ensuremath{-}53}\mathrm{Sc}$, $^{54\ensuremath{-}55}\mathrm{Ti}$, $^{56}\mathrm{V}$, and $^{58\ensuremath{-}59}\mathrm{Cr}$ produced in damped collisions of 8.3 MeV/u $^{56}\mathrm{Fe}$ ions with $^{238}\mathrm{U}$ and $^{209}\mathrm{Bi}$ is reported. Tentative identification for $^{56}\mathrm{Ti}$, $^{57\ensuremath{-}58}\mathrm{V}$, $^{60}\mathrm{Cr}$, $^{61}\mathrm{Mn}$, and $^{63}\mathrm{Fe}$ is also presented.NUCLEAR REACTIONS $^{238}\mathrm{U}$($^{56}\mathrm{Fe}$, HI), $E=8.3$ MeV/u; nuclide identification and $\ensuremath{\sigma}$ measurement for $^{52\ensuremath{-}53}\mathrm{Sc}$, $^{54\ensuremath{-}55}\mathrm{Ti}$, $^{56}\mathrm{V}$, and $^{58\ensuremath{-}59}\mathrm{Cr}$; tentative for $^{56}\mathrm{Ti}$, $^{57\ensuremath{-}58}\mathrm{V}$, $^{60}\mathrm{Cr}$, $^{61}\mathrm{Mn}$, and $^{63}\mathrm{Fe}$.

We present results on charged particle production at very low transverse momenta in the 15% most central Au+Au collisions at sqrt(s_NN) = 200 GeV obtained with the PHOBOS detector at RHIC. The invariant yields were measured at mid-rapidity in the transverse momentum ranges from 30 to 50 MeV/c for charged pions, 90 to 130 MeV/c for charged kaons and 140 to 210 MeV/c for protons and antiprotons. No significant enhancement in low transverse momentum particle production is observed as compared to extrapolations of identified particle spectra measured at an intermediate pT range. The spectra tend to flatten at low pT, consistent with the expectations of transverse expansion of the system.

Abstract The two Zero Degree Calorimeters (ZDCs) of the CMS experiment are located at ± 140 m from the collision point and detect neutral particles in the |η| &gt; 8.3 pseudorapidity region. This paper presents a study on the performance of the ZDC in the 2016 pPb run. The response of the detectors to ultrarelativistic neutrons is studied using in-depth Monte Carlo simulations. A method of signal extraction based on template fits is presented, along with a dedicated calibration procedure. A deconvolution technique for the correction of overlapping collision events is discussed.

Particle production and correlation functions from Au+Au reactions have been measured as a function of both beam energy (2-10.7AGeV) and impact parameter. These results are used to probe the dynamics of heavy-ion reactions, confront hadronic models over a wide range of conditions and to search for the onset of new phenomena.

Monthly wet precipitation samples were collected at the Elms Environmental Education Center in St. Mary's County in southern Maryland from February 1991 to January 1993 and analyzed for 36Cl. The analyses indicate that 36Cl wet deposition undergoes seasonal variations, reaching a maximum in March/April. This pattern is well established for other stratospheric tracers such as Pu, 7,10Be and ozone, and reflects seasonal variations in stratospheric-tropospheric mixing. The mean wet deposition 36Cl flux was 3.86 ± 0.54 (× 10−3) atoms/cm2s. Bulk precipitation samples were also collected at the site during the sampling period, and these data are compared to the wet-only data. The mean bulk deposition flux was 5.85 ± 0.78 (× 10−3) atoms/cm2s. Dry deposition accounts for approximately 25% of the total 36Cl deposition. Data from this study are compared with groundwater 36Cl data from the Aquia Aquifer in southern Maryland, and it is concluded that modern deposition does not account for the relatively high 36Cl concentrations found in the Aquia.

Mass and charge distributions have been measured for damped projectile-like fragments in the reaction $^{74}\mathrm{Ge}$${+}^{165}$Ho at 8.5 MeV per nucleon bombarding energy. Coincidences were measured between Z- and A-identified projectile-like fragments and angle-correlated heavy reaction partners in order to derive the primary mass distribution for projectile-like fragments. Centroids and variances of the primary and post-evaporative Z, N, and A distributions are presented. The evolution of the primary N and Z distributions as a function of energy loss is found to deviate from predictions of the nucleon exchange transport model.

The excitation-energy distribution of projectilelike fragments formed in the E/A=8.5 MeV $^{74}\mathrm{d}$/rGe${+}^{165}$Ho reaction has been obtained by applying a statistical evaporation calculation to the difference between primary fragment mass yields derived from kinematic coincidence measurements and directly measured yields. A gradual transition from approximate equipartition of excitation energy for small energy losses to a division that favors the targetlike fragment for highly damped events is observed, in agreement with previous measurements. For a given energy loss, heat partition is found to correlate with the direction of net nucleon transfer. The variances of the excitation-energy distributions are shown to increase monotonically as a function of energy loss. The average data are compared with predictions of the nucleon exchange transport model. The results suggest that energy-loss mechanisms in addition to nucleon exchange may be important in the early stages of the collision.

The working principle of sodium-ion batteries is depicted by C. Wang and co-workers, who use molybdenum disulfide/carbon nanoflowers as an anode material and sodium metal as a counter electrode. Their devices demonstrate the best cycling performance of MoS2 for Na-ion batteries reported so far. The characteristic layered structure of MoS2 is shown in the bottom right of the main image, and the reversible conversion mechnism of MoS2 during sodiation/desodiation is confirmed on page 473.

The ratios of the yields of charged antiparticles to particles have been obtained for pions, kaons, and protons near midrapidity for $d+\mathrm{Au}$ collisions at $\sqrt{{s}_{NN}}=200\phantom{\rule{0.3em}{0ex}}\mathrm{GeV}$ as a function of centrality. The reported values represent the ratio of the yields averaged over the rapidity range of $0.1&lt;{y}_{\ensuremath{\pi}}&lt;1.3$ and $0&lt;{y}_{K,p}&lt;0.8$, where positive rapidity is in the deuteron direction, and for transverse momenta $0.1&lt;{p}_{T}^{\ensuremath{\pi},K}&lt;1\phantom{\rule{0.3em}{0ex}}\mathrm{GeV}∕c$ and $0.3&lt;{p}_{T}^{p}&lt;1\phantom{\rule{0.3em}{0ex}}\mathrm{GeV}∕c$. Within the uncertainties, a lack of centrality dependence is observed in all three ratios. The data are compared to results from other systems and model calculations.

This paper presents the analysis of the dynamic fluctuations in the inclusive charged particle multiplicity measured by PHOBOS for Au+Au collisions at √sNN = 200GeV within the pseudo-rapidity range of −3 < η < 3. First the definition of the fluctuations observables used in this analysis is presented, together with the discussion of their physics meaning. Then the procedure for the extraction of dynamic fluctuations is described. Some preliminary results are included to illustrate the correlation features of the fluctuation observable. New dynamic fluctuations results will be available in a later publication.

An array of scintillator counters (“paddle counters”) for the measurement of number and energy of charged particles in heavy-ion gold–gold collisions for the PHOBOS experiment at RHIC is described. These simple, versatile, and highly efficient detectors provide a low bias and an easily understood level zero trigger. The paddle counters can also be used to select and measure event centrality. The information from the paddle counters used for triggering and event selection included the total signal height (proportional to the number of particles), the timing information of the hits, and the number of scintillators fired. The general characteristics of the paddle counters, their design parameters, and performance during the first run at RHIC are presented in this paper.

Particle production in Au+Au collisions has been measured in the PHOBOS experiment at RHIC for a range of collision energies. Three empirical observations have emerged from this dataset which require theoretical examination. First, there is clear evidence of limiting fragmentation. Namely, particle production in central Au+Au collisions, when expressed as $dN/dη'$ ($η' \equiv η-y_{beam}$), becomes energy independent at high energy for a broad region of $η'$ around $η'=0$. This energy-independent region grows with energy, allowing only a limited region (if any) of longitudinal boost-invariance. Second, there is a striking similarity between particle production in e+e- and Au+Au collisions (scaled by the number of participating nucleon pairs). Both the total number of produced particles and the longitudinal distribution of produced particles are approximately the same in e+e- and in scaled Au+Au. This observation was not predicted and has not been explained. Finally, particle production has been found to scale approximately with the number of participating nucleon pairs for $N_{part}&gt;65$. This scaling occurs both for the total multiplicity and for high $\pT$ particles (3 $

Inclusive mass, energy, and angular distributions of all fragments with $A\ensuremath{\ge}6$ have been measured for alpha-particle-induced reactions on $^{12}\mathrm{C}$ at five energies between 49 and 159 MeV. From these data the evolution of the dominant reaction mechanisms with energy is characterized. Based on analysis of the mean value of the mass distribution, it appears that linear momentum transfer from projectile to target initially increases with beam energy and reaches a maximum at about 30-40 MeV/nucleon. The low-energy data are consistent with compound nucleus formation and simple transfer processes. At higher energies the growth of forward-peaked angular distributions, continuum energy spectra, and the disappearance of two-body states demonstrate the increasing importance of nucleon-nucleon collisions and multibody breakup mechanisms as the velocity of the projectile exceeds the Fermi velocity. The observed total reaction cross section decreases with increasing bombarding energy. Inclusion of these new data into the excitation functions for $6\ensuremath{\le}A\ensuremath{\le}11$, which are required for nucleosynthesis calculations relevant to the origin of the elements Li, Be, and B, does not significantly alter conclusions based on previously available data.

Rare earth elements such as neodymium and samarium are ideal for probing the neutron environment that spent nuclear fuels are exposed to in nuclear reactors. The large number of stable isotopes can provide distinct isotopic signatures for differentiating the source material for nuclear forensic investigations. The rare-earth elements were isolated from the high activity fuel matrix via ion exchange chromatography in a shielded cell. The individual elements were then separated using cation exchange chromatography. The neodymium and samarium aliquots were analyzed via MC–ICP–MS, resulting in isotopic compositions with a precision of 0.01–0.3%.

Abstract The Aquia Formation (Paleocene) of Southern Maryland, a marine unit consisting predominantly of quartz sands, but containing 20–40% glauconite, represents one of the many productive, heavily pumped aquifers of the Southeastern Coastal Plain. An unusually high 36 Cl activity ( ~ 15 × modem water) measured in an outcrop sample is interpreted as a result of the bomb pulse input. About 25 km downdip from the recharge area, a minimum in total chloride concentration occurs. This minimum is thought to correlate with the latest low-stand of sea-level, and thus to provide time information which is in general agreement with ages calculated from hydrodynamic data. However, significant increases in the 36 Cl concentrations are observed along the flow path which may be due to ion filtration or to leakage of modem, bomb-contaminated water into the Aquia aquifer.

The PHOBOS experiment at RHIC has measured the total multiplicity of primary charged particles as a function of collision centrality in Au+Au collisions at sqrt(s_NN) = 19.6, 130 and 200 GeV. Above sqrt(s_NN) ~ 20 GeV, the total multiplicity per participating nucleon pair ( / ) in central events scales with sqrt(s) in the same way as in e+e- data. This is suggestive of a universal mechanism of particle production in strongly-interacting systems, controlled mainly by the amount of energy available for particle production (per participant pair for heavy ion collisions). The same effect has been observed in pp/pbar-p data after correcting for the energy taken away by leading particles. An approximate independence of / on the number of participating nucleons is also observed, reminiscent of ``wounded nucleon'' scaling ( proportional to ), but with the constant of proportionality set by the multiplicity measured in e+e- data rather than by pp/pbar-p data.

This report describes a novel approach to collection and analysis of radiocarbon data due to the unique design of the Naval Research Laboratory Trace Element Accelerator Mass Spectrometry system. In this approach, targets are loaded on the cathode wheel such that samples are clustered in groups of five between standards. Each target is measured until the external error asymptotically reaches a constant value and the internal error dominates, or until a predefined time limit is reached. These measurements are repeated until the desired level of counting statistics is attained. Cycle control software saves the measured beam currents and count rate, as well as all system parameters to disc at fixed intervals throughout each measurement. Data visualization software has aided in system diagnosis by exposing relationships between the measured isotope ratios and system parameters. A filtering algorithm is employed to the data set of each target measurement in an attempt to achieve a Gaussian distribution. Final results are generated by a radiocarbon calculator that allows a user to select which target measurements to treat as samples, standards and blanks, and calculates the desired values (i.e. conventional radiocarbon age, percent modern carbon, etc.) with full error propagation. Currently, a Microsoft Access® relational database is being developed which will be integrated into the existing LabVIEW® control, filtering and calculation programs in order to streamline the process from sample submission to report generation, as well as improve quality control.

Abstract Measurement of 32 Si by accelerator mass spectrometry (AMS) at relatively low energy was undertaken at the Naval Research Laboratory. Measurement of this naturally occurring radioisotope is difficult due to the low level of production of the radioisotope and the ubiquitous nature of the stable isobaric interference, 32 S. The isobar suppression was enacted using a new chemical separation and the differential energy loss profile of the 32 Si and 32 S ions after their transmission through a thin carbon foil. Determination of the energy loss and energy straggle profiles of the transmitted ion beam were made and compared to the predictions made using TRIM code.

We present transverse momentum distributions of charged hadrons produced in Au+Au collisions at sqrt(s_NN) = 200 GeV. The evolution of the spectra for transverse momenta p_T from 0.25 to 5GeV/c is studied as a function of collision centrality over a range from 65 to 344 participating nucleons. We find a significant change of the spectral shape between proton-antiproton and peripheral Au+Au collisions. Comparing peripheral to central Au+Au collisions, we find that the yields at the highest p_T exhibit approximate scaling with the number of participating nucleons, rather than scaling with the number of binary collisions.

Some of the latest results of the PHOBOS experiment from the Au+Au data are discussed. Those relevant to strangeness production are emphasized. These observations relate to the nature of the matter created when heavy ions collide at the highest achieved energy.

A high-purity germanium detector Monte Carlo model was evaluated for its ability to predict activation product ratios in Fe, Cr, Ni, and stainless-steel foils. To evaluate the model, activation product ratios calculated from simulated gamma-ray spectra were compared against those from experiment measurements. Analysis shows that the detector model accurately predicts activation product ratios within 10% when free of interferences. Presence of a shield chamber greatly increases computation time, but does not provide any quantitative advantages. Overall, the model is useful for predicting activation product ratios and experiment planning.

Results are presented for the damped reaction $^{144}\mathrm{Sm}$ + $^{84}\mathrm{Kr}$ at laboratory energies of 470, 595, and 720 MeV, corresponding to 1.2, 1.6, and 1.9 times the Coulomb barrier energy, respectively. Correlations between angle, kinetic-energy loss, and charge of the projectile-like fragments are discussed. A probability for orbiting is observed at all bombarding energies, with fragment kinetic energies indicative of large exit-channel deformations. This study shows that energy dissipation (up to $\ensuremath{\approx}100$ MeV) and charge exchange are correlated in a manner which appears to be independent of initial relative ion velocity. The results are compared with a classical dynamical transport model.[NUCLEAR REACTIONS $^{144}\mathrm{Sm}(^{84}\mathrm{Kr},x)$, ${E}_{\mathrm{lab}}=470,595, \mathrm{and} 720$ MeV; measured $\ensuremath{\sigma}(\ensuremath{\theta},E,Z)$ damped reaction products for projectile-like fragments; compared with transport model calculations.]

The first measurements of φ meson production in AuAu collisions at AGS energies are presented via the decay to K+K−. A measurement of the centrality dependence of the yield shows an increase similar to that seen for the K− with a spectral shape consistent with a relativistic Breit-Wigner distribution within the statistical errors of the present data set. Future analysis using the full data set with 4 times the statistics will allow a more accurate determination of the yields, slopes and spectral shapes.

The Phobos experiment concluded its first year of operation at RHIC taking data in Au–Au nucleus collisions at snn=65GeV and 130GeV/nucleon pair. First preliminary results of the performances of our silicon detectors in the experiment are summarized. The Phobos experiment uses silicon pad detectors for both tracking and multiplicity measurements. The silicon sensors vary strongly in their pad geometry. In this paper, we compare the signal response, the signal uniformity and signal-to-noise performance as measured in the experiment for the different geometries. Additionally, we investigate effects of very high channel occupancy on the signal response.

Recent results from the PHOBOS experiment at RHIC are presented, both from Au+Au collisions from the 2001 run and p+p and d+Au collisions from 2003. The centrality dependence of the total charged particle multiplicity in p+p and d+Au show features, such as Npart-scaling and limiting fragmentation, similar to p+A collisions at lower energies. Multiparticle physics in Au+Au is found to be local in (pseudo)rapidity, both when observed by HBT correlations and by forward-backward pseudorapidity correlations. The shape of elliptic flow in Au+Au, measured over the full range of pseudorapidity, appears to have a very weak centrality dependence. Identified particle ratios in d+Au reactions show little difference between the shape of proton and anti-proton spectra, while the absolute yields show an approximate m_T scaling.

Theoretical activation calculations for Fe, Ni, and stainless steel foils were compared against irradiated foil measurements from a critical assembly. Calculated/experiment values spanning 0.62–1.31 showed that the restricted approach used here is insufficient for experiment planning, with the collapsed cross-section being the primary source of error. The effect of decay time on gamma-ray spectroscopy measurement reliability was investigated using a Monte Carlo HPGe detector model. Simulations showed no correlation with decay time, absent interferences. Specific interferences for Fe-59 (Ni) and Co-60 (stainless steel) activation product ratios suggested optimal measurement windows having respective decay times of 9–11 days and 4–7 days.

An array of Cherenkov radiators (“the Cherenkov counters”) for the measurement of the vertex position of heavy-ion gold–gold collisions for the PHOBOS experiment at relativistic heavy ion collider is described. These simple, versatile, and highly efficient detectors provide a low bias and easily understood hardware (on-line) vertex trigger. This trigger is ready for the data-acquisition system in about 650ns. The position resolution of the vertex distribution found by the Cherenkov counters is approx. 4cm and is very stable as function of the centrality of the collisions. The general characteristics of the Cherenkov counters, their design parameters, and performance are presented, along with the implementation of the hardware vertex trigger used for PHOBOS during the 2001 run.

The NRL Accelerator Mass Spectrometer facility was recently reconfigured to incorporate a modified Cameca IMS 6f Secondary Ion Mass Spectrometer as a high-performance ion source. The NRL accelerator facility supplants the mass spectrometer portion of the IMS 6f instrument. As part of the initial testing of the combined instrument, charge-state scans were performed under various conditions. These provided the basis for studying the effects of terminal gas pressure on the process of charge-changing during acceleration. A combined system of transmission-micro-channel plate and energy detector was found to remove ghost beams produced from Pd charge-changing events in the accelerator tube.

Projectilelike fragments were detected and characterized in terms of A, Z, and energy for the reactions $^{37}\mathrm{Cl}$ on $^{40}\mathrm{Ca}$ and $^{209}\mathrm{Bi}$ at E=7.3 MeV/nucleon, and $^{35}\mathrm{Cl}$ on $^{209}\mathrm{Bi}$ at E=15 MeV/nucleon, at angles close to the grazing angle. Mass and charge distributions were generated in the N-Z plane as a function of energy loss, and parametrized in terms of their centroids, variances, and coefficients of correlation. The results are compared to the predictions of two current models based on a stochastic nucleon exchange mechanism. The drifts of the charge and mass centroids for the system $^{37}\mathrm{Cl}$ on $^{40}\mathrm{Ca}$ are consistent with a process of mass and charge equilibration mediated by nucleon exchange between the two partners, followed by evaporation. The asymmetric systems show a strong drift toward larger asymmetry, with the production of neutron-rich nuclei. It is concluded that this is the result of a net transfer of protons from the light to the heavy partner, and a net flow of neutrons in the opposite direction. Model predictions fail to reproduce in detail the evolution of the centroids for asymmetric systems. The variances for all systems increase with energy loss, as would be expected from a nucleon exchange mechanism. However, the variances for the reaction $^{37}\mathrm{Cl}$ on $^{40}\mathrm{Ca}$ are higher than those expected from that mechanism, and the variances for the reaction $^{35}\mathrm{Cl}$ on $^{209}\mathrm{Bi}$ start decreasing after about 100 MeV of energy loss. The coefficients of correlation indicate that the transfer of nucleons between projectile and target is correlated, as expected from Q-value constraints to the valley of \ensuremath{\beta} stability.

A gas-fed negative ion source for use in an accelerator mass spectrometry system has been built at the United States Naval Research Laboratory. This ion source is a filament driven plasma ion source using a multicusp magnet arrangement for plasma confinement. Our specific design was assisted by modeling using the SIMION code to optimize beam extraction optics. In addition to the ion source modeling, preliminary characterization of the plasma behavior was performed, which showed the typical and expected order of magnitude increase in collected plasma current when a multicusp magnetic arrangement is employed versus the case with no magnets. Future work will involve implementing a Langmuir probe for more detailed characterization of the plasma, investigation of the effects of using a symmetric rather than a multicusp magnet arrangement, and ultimately the extraction and characterization of ion beams from the source.

Transverse momentum spectra of charged hadrons with p T < 6 GeV/c have been measured near mid-rapidity (0.2 < η < 1.4) by the PHOBOS experiment at RHIC in Au + Au and d + Au collisions at ${\sqrt{s_{_{NN}}}~= \rm {200~GeV}}$ . The spectra for different collision centralities are compared to ${p + \bar{p}}$ collisions at the same energy. The resulting nuclear modification factor for central Au + Au collisions shows evidence of strong suppression of charged hadrons in the high-p T region (>2 GeV/c). In contrast, the d + Au nuclear modification factor exhibits no suppression of the high-p T yields. These measurements suggest a large energy loss of the high-p T particles in the highly interacting medium created in the central Au + Au collisions. The lack of suppression in d + Au collisions suggests that it is unlikely that initial state effects can explain the suppression in the central Au + Au collisions. PACS: 25.75.-q

Abstract Several elements of interest to the analytical and environmental communities do not form sufficient quantities of negative ions or negatively charged compounds to be useful for accelerator mass spectroscopy (AMS) analysis. However, neutral injection would allow such elements to be measured by AMS, provided the elements of interest can be transported to the terminal of the tandem accelerator and stripped to positive ions with a high enough efficiency. There are four key factors which influence this transport and stripping efficiency when using neutral injection: the cross-section and accompanying scattering for neutralization, and the cross-section and scattering for ionization in the terminal. A method to examine the two neutralization factors for a favorable case was developed using an ion implantation accelerator. Singly charged positive ions were accelerated to energies of 50–200 keV and passed though a differentially pumped charge exchange cell, where a portion were neutralized. The fraction of the primary beam neutralized and the degree of scattering of the neutralized beam were measured with respect to incident ion velocity and target thickness. This paper examines the efficiency of neutralization and the accompanying scattering angles produced for one such electropositive element, argon.

high-pT trigger particle, elliptic flow fluctuations and two particle correlations. ∗the PHOBOS Collaboration: B.Alver4, B.B.Back1, M.D.Baker2, M.Ballintijn4, D.S.Barton2, R.R.Betts6, A.A.Bickley7, R.Bindel7, W.Busza4, A.Carroll2, Z.Chai2, V.Chetluru6, M.P.Decowski4, E.Garcia6, T.Gburek3, N.George2, K.Gulbrandsen4, C.Halliwell6, J.Hamblen8, I.Harnarine6, M.Hauer2, C.Henderson4, D.J.Hofman6, R.S.Hollis6, R.HoAlynski3, B.Holzman2, A.Iordanova6, E.Johnson8, J.L.Kane4, N.Khan8, P.Kulinich4, C.M.Kuo5, W.Li4, W.T.Lin5, C.Loizides4, S.Manly8, A.C.Mignerey7, R.Nouicer2, A.Olszewski3, R.Pak2, C.Reed4, E.Richardson7, C.Roland4, G.Roland4, J.Sagerer6, H.Seals2, I.Sedykh2, C.E.Smith6, M.A.Stankiewicz2, P.Steinberg2, G.S.F.Stephans4, A.Sukhanov2, A.Szostak2, M.B.Tonjes7, A.Trzupek3, C.Vale4, G.J.van Nieuwenhuizen4, S.S.Vaurynovich4, R.Verdier4, G.I.Veres4, P.Walters8, E.Wenger4, D.Willhelm7, F.L.H.Wolfs8, B.Wosiek3, K.Woźniak3, S.Wyngaardt2, B.WysAlouch4 1 Argonne National Laboratory, Argonne, IL 60439-4843, USA 2 Brookhaven National Laboratory, Upton, NY 11973-5000, USA 3 Institute of Nuclear Physics PAN, Krakow, Poland 4 Massachusetts Institute of Technology, Cambridge, MA 02139-4307, USA 5 National Central University, Chung-Li, Taiwan 6 University of Illinois at Chicago, Chicago, IL 60607-7059, USA 7 University of Maryland, College Park, MD 20742, USA 8 University of Rochester, Rochester, NY 14627, USA

The early summer of 2000 saw the start of the RHIC experimental programme. The PHOBOS collaboration used data from the beginning of the running period to extract the first physics information about this exciting new regime. This first measurement consisted of pseudorapidity densities of primary charged particles near mid-rapidity in central Au + Au collisions at beam energies which gave centre-of-mass energies per pair of colliding nucleons of √snn = 56 and 130 GeV. The observed densities are higher than those observed previously in any collisions in the laboratory. In addition, the rate of increase in density between the two energies is significantly larger than that for nucleon-nucleon collisions at comparable beam energies. This paper will briefly describe the PHOBOS experiment (including the subset of the full detector installed for the early period of the RHIC beam), discuss the results of the first physics measurement and conclude with the prospects for the future, especially in the area of strangeness production.

PHOBOS is one of the four experiments at the Relativistic Heavy Ion Collider measuringp + p, d + Au, andAu + Au collisions over a broad range of energies. PHOBOS is a silicon-pad based detector with a 4π multiplicity detector and a high resolution mid-rapidity spectrometer, along with other detectors (time-of-flight walls, proton and zero degree calorimeters). PHOBOS is able to measure particles at low transverse momentum, spectra, flow, particle ratios, and multiplicity over a large region of phase space. A comparison of results forAu + Au andd + Au collisions at√SNN = 220GeV will be discussed.

The effects of baryon stopping and its resulting energy deposition on the dynamics of Au + Au collisions at 6, 8 and 10.8 GeV/nucleon are explored with recent results from the AGS experiment E917. Current analyses of stopping, collective flow signals and HBT parameters are presented. Strangeness and anti-baryon production is examined using the yields of anti-lambdas and anti-protons.

Dating Techniques Alice C. Mignerey, Alice C. Mignerey University of Maryland, Department of Chemistry and Biochemistry, College Park, Maryland, U.S.A.Search for more papers by this author Alice C. Mignerey, Alice C. Mignerey University of Maryland, Department of Chemistry and Biochemistry, College Park, Maryland, U.S.A.Search for more papers by this author First published: 15 April 2003 https://doi.org/10.1002/3527600434.eap601 Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat digital Encyclopedia of Applied PhysicsBrowse other articles of this reference work:BROWSE BY TOPICBROWSE A-Z RelatedInformation

The charge and mass of the projectile-like fragments produced in the 15-MeV per nucleon $^{40}\mathrm{Ca}$${+}^{209}$Bi reaction were determined for products detected near the grazing angle. Neutron number-charge (N-Z) distributions were generated as a function of the total kinetic energy loss and parametrized by their centroids, variances, and correlation coefficients. Although the initial system is very asymmetric, after the interaction, a drift of the charge and mass centroids toward further asymmetry is observed. The production of projectile-like fragments is consistent with a tendency of the projectile-like fragments to retain the projectile neutron-to-proton ratio 〈N〉/〈Z〉\ensuremath{\simeq}1. The correlation coefficient remains well below 1.0 for the entire range of total kinetic energy lost. Predictions of two nucleon exchange models, Randrup's and Tassan-Got's, are compared to the experimental results. The models are not able to reproduce the evolution of the experimental distributions, especially the fact that the variances reach a maximum and then decrease as function of the energy loss. This behavior supports the hypothesis that some form of projectile-like fragmentation or cluster emission is perturbing the product distribution from that expected from a damped mechanism.

The deposition of atmospheric {sup 36}Cl is of primary importance to hydrological tracer applications. In this study, {sup 36}Cl was measured monthly in wet-only precipitation samples collected from February, 1991 to January, 1993 at the Elms Environmental Education Center in St. Mary`s County, Maryland. In addition, bulk deposition samples were collected over a 1 y period at seven sites across the Northern United States and analyzed for {sup 36}Cl. The mean wet-only {sup 36}C/Cl ratio for the 2 y sampling period at the Elms site is 68{plus_minus}19 (xl0{sup -15}), and the mean {sup 36}Cl Concentration is 1.2{plus_minus}0.1 (x 10{sup 6}) atoms/L. The {sup 36}Cl deposition flux data reveal a distinct seasonal deposition pattern, with peaks occurring in March and April. The mean wet deposition {sup 36}Cl flux is 38{plus_minus}5 atoms/m{sup 2}s. Comparison between wet only and bulk deposition samples indicates that the difference accounts for approximately 25% of the total {sup 36}Cl deposition at the Elms site.

United States. Department of Energy (Grants DE-AC02-98CH10886, DE-FG02-93ER40802, DE-FG02- 94ER40818, DE-FG02-94ER40865, DE-FG02-99ER41099, and DE-AC02-06CH11357)

A selection of experimental results from the PHOBOS Collaboration relevant for probing high-energy nuclear collisions with high transverse momentum particles is presented. The inclusive yields of charged particles and comparisons between nuclear and elementary collisions already reveal a large amount of parton energy loss in the hot and dense medium created in heavy ion collisions. Remarkable scaling and factorization features are observed, unifying the data taken at various collision energies, centralities and nuclear sizes. To further analyze the nature of the energy loss, a measurement of pseudorapidity (Δη) and azimuthal angle (Δφ) correlations between high transverse momentum charged hadrons (p T >2.5 GeV/c) and all associated charged particles is presented at both short-range (small Δη) and long-range (large Δη) over a continuous detector acceptance covering −4<Δη<2. Various near- and away-side features of the correlation structure are discussed as a function of centrality in Au + Au collisions at $\sqrt{s_{NN}}=200$ GeV. The results provide new information about the longitudinal (Δη) extent of the near-side ‘ridge’ structure, first observed by the STAR Collaboration over a narrower η range. In central Au + Au collisions the ridge structure extends to at least Δη=4, and its strength completely diminishes as collisions become more peripheral.

The PHOBOS experiment has measured the properties of particle production in heavy ion collisions between sqrt(s_NN) of 20 and 200 GeV. The dependencies of charged particle yield on energy, system size, and both longitudinal and transverse momentum have been determined over close to the full kinematic range. Identified charged particles emitted near mid-rapidity have been studied over about 2 orders of magnitude in transverse momentum. This broad data set was found to be characterized by a small number of simple scalings which factorize to a surprising degree. This study has recently been extended by the addition of new data for Cu+Cu as well as new analyses of Au+Au data, including more peripheral collisions. In addition, the exploration of global properties has been expanded with the use of new techniques, including two-particle correlations, more sensitive searches for rare events, and more detailed studies of particles emitted at very forward rapidity. The characteristics of particle production which are revealed by this extensive data set will be described along with the implications for future data from the LHC.

Retrospective characterization of a (30 MeV D, Be) neutron source was performed employing multi-foil activation and STAYSL-PNNL. Experimental reaction rates were calculated from gamma spectroscopy measurements of irradiated foils and MCNP provided the guess spectrum. Adjusted spectra were evaluated through activation calculations for a stainless-steel target using FISPACT-II. Adjusted spectra showed limited dependence on the dosimetry reactions and provided minor improvements in activation calculations. Omitting reflected neutrons in the guess spectrum generated poor activation results and the limited number of dosimetry reactions introduced doubt in the adjusted spectra. A dedicated neutron spectrometry experiment and a more detailed simulation is required.

Directed flow, v1, of charged hadrons has been measured in Au-Au collisions at RHIC for center-of-mass energies √sNN = 19.6, 130, 62.4, and 200 GeV using the PHOBOS detector. The large acceptance of PHOBOS for charged particles allows measurements over the full range of pseudorapidity |η| < 5.4. The results for a symmetric subevent method are shown at all four energies. Comparison is made to a mixed harmonic method for the highest energy, and compared to similar results from the STAR collaboration.

Recent results on identified particle production from the PHOBOS experiment at the relativistic heavy-ion collider (RHIC) are summarized. Transverse momentum spectra of pions, kaons, protons and antiprotons from Au+Au collisions at s NN = 62.4 GeV are presented close to mid-rapidity. Baryons have been found to have substantially harder transverse momentum spectra than mesons. The p/π + ratio reaches unity at high p T , which fits into a smooth trend together with measurements at lower and higher collision energies. At very low transverse momenta no significant excess of particle yield was found, compared to extrapolations from higher p T . The net proton yield at mid-rapidity appears to be proportional to the number of participant nucleons in Au+Au collisions. The PHOBOS acceptance and mass resolution for the 0 meson at low p T were studied in detail.

The distributions of charged particles from heavy ion collisions have been measured by the PHOBOS collaboration. Results from Au+Au collisions at various energies and over a broad range of centrality are presented and discussed. This data are compared to p+p, d+Au and Cu+Cu collisions at the corresponding energy and centrality.

The PHOBOS collaboration has carried out a systematic study of charged particle multiplicities in Cu+Cu and Au+Au collisions at the Relativistic Heavy-Ion Collider (RHIC) at Brookhaven National Laboratory. A unique feature of the PHOBOS detector is its ability to measure charged particles over a very wide angular range from 0.5 to 179.5 deg. corresponding to |eta|<5.4. The general features of the charged particle multiplicity distributions as a function of pseudo-rapidity, collision energy and centrality, as well as system size, are discussed.

The elliptic flow v2 is presented for the Cu+Cu collisions at sqrt{s_NN} = 62.4 and 200 GeV, as a function of pseudorapidity. Comparison to results for the Au+Au collisions at the same energies shows a reduction of about 20% in the flow observed for a centrality selection of 0-40%. The centrality dependent flow, expressed as a function of the number of participants N_part, is compared for the Cu+Cu and Au+Au systems using two definitions of eccentricity, the standard definition epsilon_standard and a participant eccentricity epsilon_part. The v2 / <epsilon_part> as a function of N_part, for the Au+Au and Cu+Cu collisions are consistent within errors, while v2 / <epsilon_standard> gives unrealistically large values for Cu+Cu, especially for central collision.

Nuclear Disassembly Mechanisms in Symmetric Entrance Channel Heavy-Ion Collisions at Intermediate Energies, B Llope Status Report of the Atlas Electron-Positron Experiment (APEX), M Rhein New Results from Au-Au Interactions AGS, S Steadman Freeze-out and Hadronization, L Csernai Strangeness in NA36 - QGP or Reinteractions?, I Sakrejda Characterizing Fragment Emission in Intermediate Energy Heavy-ion Reactions, P DeSouza The STAR Experiment at RHIC, J Marx Is There Flow at the AGS?, J Wessels Heavy-Ion Reaction Measurements with the EOS TPC, H Wieman Fragment Production and Collective Effects in Central Au on Au Collisions, T Wienold Fragmentation of Colliding Drops, A Menchaca-Rocha.

Several techniques have been developed by PHOBOS for measuring the multiplicity of charged particles produced in Au + Au collisions. We will discuss one of these techniques (the 'Tracklet' method) which utilizes two-hit tracks which intersect at the reconstructed collision vertex position. The physics that comes from these measurements can give valuable insight into the underlying mechanisms of particle production over a center of mass energy range of √SNN = 19.6 GeV to the maximum RHIC energy of √SNN = 200 GeV.

Directed flow, v1, of charged hardons has been measured in Au-Au collisions at RHIC for center-of-mass energies sqrt(sNN) = 19.6, 130, 62.4, and 200 GeV using the PHOBOS detector. The large acceptance of PHOBOS for charged particles allows measurements over the full range of pseudorapidity |eta| &lt;5.4. The results for a symmetric subevent method are shown at all four energies. Comparison is made to a mixed harmonic method for the highest energy, and compared to similar results from the STAR collaboration.

We present transverse momentum distributions of charged hadrons produced in Au+Au collisions at √SNN = 200 GeV. The evolution of the spectra for transverse momenta pT from 0.25 to 5 GeV/C is studied as a function of collision centrality. We find a significant change of the spectral shape between proton-antiproton and peripheral Au+Au collisions. When comparing peripheral to central Au+Au collisions, we find that the yields at the highest pT exhibit approximate scaling with the number of participating nucleons, rather than scaling with the number of binary collisions.

We present transverse momentum distributions of charged hadrons produced in Au+Au collisions at s N N = 200 GeV. The evolution of the spectra for transverse momenta p T from 0.25 to 5 GeV/C is studied as a function of collision centrality. We find a significant change of the spectral shape between proton-antiproton and peripheral Au+Au collisions. When comparing peripheral to central Au+Au collisions, we find that the yields at the highest p T exhibit approximate scaling with the number of participating nucleons, rather than scaling with the number of binary collisions.

This Technical Report focuses on two aspects of this project. First, the results from the calibration of the Spectator Reaction Plane Detector (SRPD) addition to the Zero Degree Calorimeter (ZDC) in the CMS experiment are presented, followed by the pre-liminary results from radiation studies of quartz being performed using the electron linac here at the University of Maryland. The data taken in the November 2018 run are being analyzed with the ultimate goal of producing a reaction plane measurement using spectator neutrons detected in the ZDC. Funds provided by this grant partially supported the graduate student who is performing these calibrations. They were also used to support radiation tests of quartz rod material being performed at the University of Maryland Radiation Facilities Electron Linear Accelerator.

Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Icon Share Twitter Facebook Reddit LinkedIn Tools Icon Tools Reprints and Permissions Cite Icon Cite Search Site Citation A. H. Wuosmaa, B. B. Back, M. D. Baker, D. S. Barton, S. Basilev, B. D. Bates, R. Baum, R. R. Betts, A. Białas, R. Bindel, W. Bogucki, A. Budzanowski, W. Busza, A. Carroll, M. Ceglia, Y.-H. Chang, A. E. Chen, T. Coghen, C. Conner, W. Czyz, B. Dabrowski, M. P. Decowski, M. Despet, P. Fita, J. Fitch, M. Friedl, K. Galuska, R. Ganz, E. Garcia, N. George, J. Godlewski, C. Gomes, E. Griesmayer, K. Gulbrandsen, S. Gushue, J. Halik, C. Halliwell, P. Haridas, A. Hayes, G. A. Heintzelman, C. Henderson, R. Hollis, R. Hołynski, B. Holzman, E. Johnson, J. Kane, J. Katzy, W. Kita, J. Kotuła, H. Kraner, W. Kucewicz, P. Kulinich, C. Law, M. Lemler, J. Ligocki, W. T. Lin, S. Manly, D. McCleod, J. Michałowski, A. Mignerey, J. Mülmenstädt, M. Neal, R. Nouicer, A. Olszewski, R. Pak, I. C. Park, M. Patel, H. Pernegger, M. Plesko, C. Reed, L. P. Remsberg, M. Reuter, C. Roland, G. Roland, D. Ross, L. Rosenberg, J. Ryan, A. Sanzgiri, P. Sarin, P. Sawicki, J. Scaduto, J. Shea, J. Sinacore, W. Skulski, S. G. Steadman, G. S. F. Stephans, P. Steinberg, A. Straczek, M. Stodulski, M. Strek, Z. Stopa, A. Sukhanov, K. Surowiecka, J.-L. Tang, R. Teng, A. Trzupek, C. Vale, G. J. van Nieuwenhuizen, R. Verdier, B. Wadsworth, F. L. H. Wolfs, B. Wosiek, K. Wozniak, A. H. Wuosmaa, B. Wysłouch, K. Zalewski, P. Zychowski; First results from the PHOBOS experiment at RHIC. AIP Conf. Proc. 12 July 2001; 576 (1): 231–234. https://doi.org/10.1063/1.1395292 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentAIP Publishing PortfolioAIP Conference Proceedings Search Advanced Search |Citation Search

PHOBOS is one of four experiments studying the Au-Au interactions at RHIC. The data collected during the first few weeks after the RHIC start-up, using the initial configuration of the PHOBOS detector, were sufficient to obtain the first physics results for the most central collisions of Au nuclei at the center of mass energy of 56 and 130 AGeV. The pseudorapidity density of charged particles near midrapidity is shown and compared with data at lower energies and from $pp$ and $p\bar{p}$ collisions. The progress of the analysis of the data is also presented.PHOBOS is one of four experiments studying the Au-Au interactions at RHIC. The data collected during the first few weeks after the RHIC start-up, using the initial configuration of the PHOBOS detector, were sufficient to obtain the first physics results for the most central collisions of Au nuclei at the center of mass energy of 56 and 130 AGeV. The pseudorapidity density of charged particles near midrapidity is shown and compared with data at lower energies and from $pp$ and $p\bar{p}$ collisions. The progress of the analysis of the data is also presented.

The PHOBOS detector is designed to study the physics of Au+Au collisions at the Relativistic Heavy Ion Collider. The detector is almost entirely made of silicon pad detectors and was fully operational during the first year of operation. The detector is described, and key performance characteristics are summarized.

The multiplicity of charged particles produced in Au+Au collisions as a function of energy, centrality, rapidity and azimuthal angle has been measured with the PHOBOS detector at RHIC. These results contribute to our understanding of the initial state of heavy ion collisions and provide a means to compare basic features of particle production in nuclear collisions with more elementary systems.