M. Murray

We review the main results obtained by the BRAHMS collaboration on the properties of hot and dense hadronic and partonic matter produced in ultrarelativistic heavy ion collisions at RHIC. A particular focus of this paper is to discuss to what extent the results collected so far by BRAHMS, and by the other three experiments at RHIC, can be taken as evidence for the formation of a state of deconfined partonic matter, the so called quark-gluon-plasma (QGP). We also discuss evidence for a possible precursor state to the QGP, i.e. the proposed Color Glass Condensate.

We report on a study of the transverse momentum dependence of nuclear modification factors R(dAu) for charged hadrons produced in deuteron + gold collisions at sqrt[s(NN)]=200 GeV, as a function of collision centrality and of the pseudorapidity (eta=0, 1, 2.2, 3.2) of the produced hadrons. We find a significant and systematic decrease of R(dAu) with increasing rapidity. The midrapidity enhancement and the forward rapidity suppression are more pronounced in central collisions relative to peripheral collisions. These results are relevant to the study of the possible onset of gluon saturation at energies reached at BNL RHIC.

This White Paper aims at highlighting the important benefits in the science reach of the EIC. High luminosity operation is generally desirable, as it enables producing and harvesting scientific results in a shorter time period. It becomes crucial for programs that would require many months or even years of operation at lower luminosity.

We present spectra of charged hadrons from Au+Au and d+Au collisions at √sNN=200 GeV measured with the BRAHMS experiment at RHIC. The spectra for different collision centralities are compared to spectra from p+¯p collisions at the same energy scaled by the number of binary collisions. The resulting ratios (nuclear modification factors) for central Au+Au collisions at η=0 and η=2.2 evidence a strong suppression in the high pT region (>2 GeV/c). In contrast, the d+Au nuclear modification factor (at η=0) exhibits an enhancement of the high pT yields. These measurements indicate a high energy loss of the high pT particles in the medium created in the central Au+Au collisions. The lack of suppression in d+Au collisions makes it unlikely that initial state effects can explain the suppression in the central Au+Au collisions.Received 3 July 2003DOI:https://doi.org/10.1103/PhysRevLett.91.072305©2003 American Physical Society

Data from a number of different experimental measurements are used to construct caloric curves for five different regions of nuclear mass. These curves are qualitatively similar, and exhibit plateaus at the higher excitation energies. The limiting temperatures represented by the plateaus decrease with increasing nuclear mass, and are in very good agreement with results of recent calculations employing either a chiral symmetry model or the Gogny interaction. This agreement strongly favors a soft equation of state. Evidence is presented which suggests that critical excitation energies and critical temperatures might be determined from caloric curve measurements when the mass variations inherent in such measurements are taken into account.

We present charged-particle multiplicities as a function of pseudorapidity and collision centrality for the 197 Au 1 197 Au reaction at p s NN 200 GeV.For the 5% most central events we obtain dN ch ͞dhj h0 625 6 55 and N ch j 24.7#h#4.7 4630 6 370, i.e., 14% and 21% increases, respectively, relative to p s NN 130 GeV collisions.Charged-particle production per pair of participant nucleons is found to increase from peripheral to central collisions around midrapidity.These results constrain current models of particle production at the highest RHIC energy.

We have measured rapidity densities dN/dy of pi+/- and K+/- over a broad rapidity range (-0.1 < y < 3.5) for central Au + Au collisions at square root(sNN) = 200 GeV. These data have significant implications for the chemistry and dynamics of the dense system that is initially created in the collisions. The full phase-space yields are 1660 +/- 15 +/- 133 (pi+), 1683 +/- 16 +/- 135 (pi-), 286 +/- 5 +/- 23 (K+), and 242 +/- 4 +/- 19 (K-). The systematics of the strange to nonstrange meson ratios are found to track the variation of the baryochemical potential with rapidity and energy. Landau-Carruthers hydrodynamics is found to describe the bulk transport of the pions in the longitudinal direction.

Transverse mass spectra of pions, kaons, and protons from the symmetric heavy-ion collisions 200A GeV S 1 S and 158A GeV Pb 1 Pb, measured in the NA44 focusing spectrometer at CERN, are presented.The mass dependence of the slope parameters provides evidence of collective transverse flow from expansion of the system in heavy-ion induced central collisions.[S0031-9007(97)02697-5

Transverse momentum spectra and rapidity densities, dN/dy, of protons, antiprotons, and net protons (p−p¯) from central (0%–5%) Au+Au collisions at sNN=200 GeV were measured with the BRAHMS experiment within the rapidity range 0≤y≤3. The proton and antiproton dN/dy decrease from midrapidity to y=3. The net-proton yield is roughly constant for y<1 at dN/dy∼7, and increases to dN/dy∼12 at y∼3. The data show that collisions at this energy exhibit a high degree of transparency and that the linear scaling of rapidity loss with rapidity observed at lower energies is broken. The energy loss per participant nucleon is estimated to be 73±6 GeV.Received 31 December 2003DOI:https://doi.org/10.1103/PhysRevLett.93.102301©2004 American Physical Society

High Energy collisions of nuclei usually lead to the emission of evaporation neutrons from both ``beam'' and ``target'' nuclei. At the RHIC heavy ion collider with 100GeV/u beam energy, evaporation neutrons diverge by less than $~2$ milliradians from the beam axis Neutral beam fragments can be detected downstream of RHIC ion collisions (and a large aperture Accelerator dipole magnet) if $\theta\leq$ 4 mr but charged fragments in the same angular range are usually too close to the beam trajectory. In this 'zero degree' region produced particles and other secondaries deposit negligible energy when compared with that of beam fragmentation neutrons. The purpose of the RHIC zero degree calorimeters (ZDC's) is to detect neutrons emitted within this cone along both beam directions and measure their total energy (from which we calculate multiplicity). The ZDC coincidence of the 2 beam directions is a minimal bias selection of heavy ion collisions. This makes it useful as an event trigger and a luminosity monitor\cite{baltz} and for this reason we built identical detectors for all 4 RHIC experiments. The neutron multiplicity is also known to be correlated with event geometry \cite{appel} and will be used to measure collision centrality in mutual beam int eractions.

We present charged particle densities as a function of pseudorapidity and collision centrality for the 197Au+197Au reaction at sqrt{s_{NN}}=130 GeV. An integral charged particle multiplicity of 3860+/-300 is found for the 5% most central events within the pseudorapidity range -4.7 <= eta <= 4.7. At mid-rapidity an enhancement in the particle yields per participant nucleon pair is observed for central events. Near to the beam rapidity, a scaling of the particle yields consistent with the ``limiting fragmentation'' picture is observed. Our results are compared to other recent experimental and theoretical discussions of charged particle densities in ultra-relativistic heavy-ion collisions.

From experimental observations of limiting temperatures in heavy ion collisions we derive the critical temperature of infinite nuclear matter Tc=16.6+/-0.86. Theoretical model correlations between Tc, the compressibility modulus K, the effective mass m*, and the saturation density rho s are then exploited to derive the quantity (K/m*)1/2 rho -1/3 s. This quantity together with calculations employing Skyrme and Gogny interactions indicates a value of K in moderately excited nuclei that is in excellent agreement with the value determined from giant monopole resonance data.

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTEffect of Silver Ion Coördination upon the Raman Spectra of Some Unsaturated Compounds1Harvey J. Taufen, M. J. Murray, and Forrest F. ClevelandCite this: J. Am. Chem. Soc. 1941, 63, 12, 3500–3503Publication Date (Print):December 1, 1941Publication History Published online1 May 2002Published inissue 1 December 1941https://doi.org/10.1021/ja01857a070RIGHTS & PERMISSIONSArticle Views116Altmetric-Citations40LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (408 KB) Get e-Alertsclose Get e-Alerts

The infra-red absorption spectrum in the region 700–4000 cm−1, both for the liquid and for the gas at various pressures, and precise values for the depolarization factors of the Raman lines of spiropentane are reported. Infra-red and Raman frequencies, estimated relative intensities, and qualitative depolarization data are reported also for 1,1-dimethylcyclopropane. Selection rules for the two hydrocarbons are discussed, and it is shown that the observed numbers of Raman frequencies are not inconsistent with the structures D2d and C2v for the spiropentane and 1,1-dimethylcyclopropane, respectively. In addition, Raman and infra-red data are included for the isomers, 1-methylcyclobutene and methylenecyclobutane. Tentative assignments of the fundamentals are made for each of the four hydrocarbons.

First Page

An extensive experimental survey of the features of the disassembly of a small quasiprojectile system with A~36, produced in the reactions of 47 MeV/nucleon 40Ar+27Al, 48Ti, and 58Ni, has been carried out. Nuclei in the excitation energy range of 1–9 MeV/nucleon have been investigated employing a new method to reconstruct the quasiprojectile source. At an excitation energy ∼5.6 MeV/nucleon many observables indicate the presence of maximal fluctuations in the deexcitation processes. These include the normalized second moments of the Campi plot and normalized variances of the distributions of order parameters such as the atomic number of the heaviest fragment Zmax and the total kinetic energy. The evolution of the correlation of the atomic number of the heaviest fragment with that of the second heaviest fragment and a bimodality test are also consistent with a transition in the same excitation energy region. The related phase separation parameter, Sp, shows a significant change of slope at the same excitation energy. In the same region a Δ-scaling analysis for of the heaviest fragments exhibits a transition to Δ = 1 scaling, which is predicted to characterize a disordered phase. The fragment topological structure shows that the rank-sorted fragments obey Zipf's law at the point of largest fluctuations, providing another indication of a liquid gas phase transition. The Fisher droplet model critical exponent τ ∼ 2.3 obtained from the charge distribution at the same excitation energy is close to the critical exponent of the liquid gas phase transition universality class. The caloric curve for this system shows a monotonic increase of temperature with excitation energy and no apparent plateau. The temperature at the point of maximal fluctuations is 8.3±0.5MeV. Taking this temperature as the critical temperature and employing the caloric curve information we have extracted the critical exponents β,γ, and σ from the data. Their values are also consistent with the values of the universality class of the liquid gas phase transition. Taken together, this body of evidence strongly suggests a phase change in an equilibrated mesoscopic system at, or extremely close to, the critical point.25 MoreReceived 14 October 2004DOI:https://doi.org/10.1103/PhysRevC.71.054606©2005 American Physical Society

We present ratios of the numbers of charged antiparticles to particles (pions, kaons and protons) in Au + Au collisions at √ sNN = 200 GeV as a function of rapidity in the range y=0-3.While the particle ratios at midrapidity are approaching unity, the K -/K + and p/p ratios decrease significantly at forward rapidities.An interpretation of the results within the statistical model indicates a reduction of the baryon chemical potential from µB ≈ 130MeV at y=3 to µB ≈ 25MeV at y=0.

We present particle spectra for charged hadrons π±, K±, p, and p¯ from pp collisions at s=200 GeV measured for the first time at forward rapidities (2.95 and 3.3). The kinematics of these measurements are skewed in a way that probes the small momentum fraction in one of the protons and large fractions in the other. Large proton to pion ratios are observed at values of transverse momentum that extend up to 4 GeV/c, where protons have momenta up to 35 GeV. Next-to-leading order perturbative QCD calculations describe the production of pions and kaons well at these rapidities, but fail to account for the large proton yields and small p¯/p ratios.Received 22 January 2007DOI:https://doi.org/10.1103/PhysRevLett.98.252001©2007 American Physical Society

Transverse momentum spectra of protons and anti-protons measured in the rapidity range 0<y<3.1 from 0-10% central Au+Au collisions at sqrt{s_{NN}}=62.4 GeV are presented. The rapidity densities, dN/dy, of protons, anti-protons and net-protons N()p-N(pbar) have been deduced from the spectra over a rapidity range wide enough to observe the expected maximum net-baryon density. From mid-rapidity to y=1 the net-proton yield is roughly constant (dN/dy ~ 10),but rises to dN/dy ~25 at 2.3<y<3.1. The mean rapidity loss is 2.01 +-0.16 units from beam rapidity. The measured rapidity distributions are compared to model predictions. Systematics of net-baryon distributions and rapidity loss vs. collision energy are discussed.

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTTotal Phenols in Gasolines and in Cresylic AcidsM. J. MurrayCite this: Anal. Chem. 1949, 21, 8, 941–945Publication Date (Print):August 13, 1949Publication History Published online1 May 2002Published inissue 13 August 1949https://doi.org/10.1021/ac60032a016Request reuse permissionsArticle Views149Altmetric-Citations31LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (643 KB) Get e-Alertsclose Get e-Alerts

Raman frequencies, relative intensities, and depolarization factors are listed for 1-iodo-1-propyne, 1-bromo-1-propyne, 1-chloro-1-propyne, and 3,3-dimethyl-1-butyne. The relative intensities and depolarization factors were obtained by use of a Gaertner microdensitometer. Assignments of the frequencies to the different vibration types and calculated values of the heat capacities for the ideal gaseous state at 1 atmos. pressure are given for 1-iodo-1-propyne and 1-bromo-1-propyne. Examination of the results in the 2200-cm−1 region leads to the suggestion that the resonance splitting of the triple bond fundamental for disubstituted acetylenes may frequently be due to the combination frequencies (2900–700) and (1375+700); and that the doubling of the 2100-cm−1 fundamental for the monosubstituted acetylenes, 3-methyl-1-butyn-3-ol and 3,3-dimethyl-1-butyne, may be due to the second overtones of the highly polarized, ``breathing'' frequencies near 700 cm−1 of the groups O |C−C− | Cand C |C−C− | C, respectively.

Particle production of identified charged hadrons, $\pi^{\pm}$, $K^{\pm}$, $p$, and $\bar{p}$ in Au+Au collisions at $\sqrt(snn) =$ 200 GeV has been studied as a function of transverse momentum and collision centrality at $y=0$ and $y\sim1$ by the BRAHMS experiment at RHIC. Significant collective transverse flow at kinetic freeze-out has been observed in the collisions. The magnitude of the flow rises with the collision centrality. Proton and kaon yields relative to the pion production increase strongly as the transverse momentum increases and also increase with centrality. Particle yields per participant nucleon show a weak dependence on the centrality for all particle species. Hadron production remains relatively constant within one unit around midrapidity in Au+Au collisions at $\sqrt(snn) =$ 200 GeV.

The reaction systems, 64 Zn + 58 Ni, 64 Zn + 92 Mo, 64 Zn + 197 Au, at 26A, 35A and 47A MeV, have been studied both in experiments with a 4π detector array, NIMROD, and with Antisymmetrized Molecular Dynamics model calculations employing effective interactions corresponding to soft and stiff equations of state (EOS).Direct experimental observables, such as multiplicity distributions, charge distributions, energy spectra and velocity spectra, have been compared in detail with those of the calculations and a reasonable agreement is obtained.The velocity distributions of α particles and fragments with Z ≥ 3 show distinct differences in calculations with the soft EOS and the stiff EOS.The velocity distributions of α particle and Intermediate Mass Fragments (IMF's) are best described by the stiff EOS.Neither of the above direct observables nor the strength of the elliptic flow are sensitive to changes in the in-medium nucleon-nucleon (NN) cross sections.A detailed analysis of the central collision events calculated with the stiff EOS revealed that multifragmentation with cold fragment emission is a common feature predicted for all reactions studied here.A possible multifragmentation scenario is presented; after the preequilibrium emission ceases in the composite system, cold light fragments are formed in a hotter gas of nucleons and stay cold until the composite system underdoes multifragmentation.For reaction with 197 Au at 47A MeV a significant radial expansion takes place.For reactions with 58 Ni and 92 Mo at 47A MeV semi-transparency becomes prominent.The differing reaction dynamics drastically change the kinematic characteristics of emitted fragments.This scenario gives consistent explanations for many existing experimental results in the Fermi energy domain.

Proton distributions at midrapidity have been measured for 158A·GeV Pb+Pb collisions in the focusing spectrometer experiment NA44 at CERN. A high degree of nuclear stopping is found in the truly heavy ion collisions. Systematic results of single particle transverse momentum distributions of pions, kaons, and protons, of 200A·GeV S+S and 158A·GeV Pb+Pb central collisions will be addressed within the context of thermalization. By comparing these data with thermal and transport models, freeze-out parameters such as the temperature parameter Tfo and mean collective flow velocity 〈β〉 are extracted. Preliminary results of the particle ratios of K−K+ and pp are discussed in the context of cascade models of RQMD and VENUS.

First results of the mT dependence of π+π+ and K+K+ correlations from S+Pb collisions at 200 GeV /c per nucleon measured by the focusing spectrometer of the NA44 experiment at CERN are presented. Multidimensional fits characterize the pion and kaon emission volume. The pion radius parameter decreases with increasing pT. Furthermore, the pion and kaon radii show a common 1/√mT dependence. This behavior can be interpreted as a result of a strong momentum-position correlation arising from collective flow.Received 20 July 1994DOI:https://doi.org/10.1103/PhysRevLett.74.3340©1995 American Physical Society

Two-pion correlations from Pb+Pb collisions at 158 $\mathrm{GeV}/c$ per nucleon are measured by the NA44 experiment at CERN. Multidimensional fits characterize the emission volume, which is found to be larger than in S-induced collisions. Comparison to the RQMD model is used to relate the fit parameters to the actual emission volume.

The reactions ${}^{12}\mathrm{C}{+}^{116}\mathrm{Sn},$ ${}^{22}\mathrm{N}\mathrm{e}+\mathrm{A}\mathrm{g},$ ${}^{40}\mathrm{Ar}{+}^{100}\mathrm{Mo},$ and ${}^{64}\mathrm{Zn}{+}^{89}\mathrm{Y}$ have been studied at $47A \mathrm{MeV}$ projectile energy. For these reactions the most violent collisions lead to increasing amounts of fragment and light particle emission as the projectile mass increases. This is consistent with quantum molecular dynamics (QMD) model simulations of the collisions. Moving source fits to the light charged particle data have been used to gain a global view of the evolution of the particle emission. Comparisons of the multiplicities and spectra of light charged particles emitted in the reactions with the four different projectiles indicate a common emission mechanism for early emitted ejectiles even though the deposited excitation energies differ greatly. The spectra for such ejectiles can be characterized as emission in the nucleon-nucleon frame. Evidence that the ${}^{3}\mathrm{He}$ yield is dominated by this type of emission and the role of the collision dynamics in determining the ${}^{3}\mathrm{H}{/}^{3}\mathrm{He}$ yield ratio are discussed. Self-consistent coalescence model analyses are applied to the light cluster yields, in an attempt to probe emitter source sizes and to follow the evolution of the temperatures and densities from the time of first particle emission to equilibration. These analyses exploit correlations between ejectile energy and emission time, suggested by the QMD calculations. In this analysis the degree of expansion of the emitting system is found to increase with increasing projectile mass. The double isotope yield ratio temperature drops as the system expands. Average densities as low as $0.36{\ensuremath{\rho}}_{0}$ are reached at a time near $100 \mathrm{fm}/c$ after contact. Calorimetric methods were used to derive the mass and excitation energy of the excited nuclei which are present after preequilibrium emission. The derived masses range from 102 to 116 u and the derived excitation energies increase from 2.6 to 6.9 MeV/nucleon with increasing projectile mass. A caloric curve is derived for these expanded $A\ensuremath{\sim}110$ nuclei. This caloric curve exhibits a plateau at temperatures near 7 MeV. The plateau extends from $\ensuremath{\sim}3.5$ to 6.9 MeV/nucleon excitation energy.

π+π+ correlations from S + Pb collisions at 200 GeV/c per nucleon, measured by the focusing spectrometer of the NA44 experiment at CERN, are presented. The large data set, particularly at small values of Qinv, allows determination of the detailed shape of the correlation function. We construct the background by event mixing, and correct for resolution, Coulomb interaction, and distortion of single-particle spectra which produce effects large compared to the statistical errors at small Qinv. An exponential, rather than gaussian, source distribution is slightly favoured, but both are statistically acceptable.

Charged-particle pseudorapidity densities are presented for the d+Au reaction at √sNN=200 GeV with −4.2≤η≤4.2. The results, from the BRAHMS experiment at BNL Relativistic Heavy-Ion Collider, are shown for minimum-bias events and 0%–30%, 30%–60%, and 60%–80% centrality classes. Models incorporating both soft physics and hard, perturbative QCD-based scattering physics agree well with the experimental results. The data do not support predictions based on strong-coupling, semiclassical QCD. In the deuteron-fragmentation region the central 200 GeV data show behavior similar to full-overlap d+Au results at √sNN=19.4 GeV.Received 21 January 2004DOI:https://doi.org/10.1103/PhysRevLett.94.032301©2005 American Physical Society

Displacements, estimated intensities and depolarization factors have been measured for acetone, 2,6-dimethyl-4-heptanone, 5-nonanone, 7-tridecanone, 8-pentadecanone and 5-tetradecanone. The results for acetone are compared with the previous data: Eight lines previously reported by one or more investigators are believed to be non-existent. A new weak line was observed at 1676 cm−1. The depolarization factors obtained agree well with those reported by Simons, except that the 1356 line was found to be considerably less polarized and data for five additional lines were obtained.

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTRaman Spectra Evidence for Hindrance of Resonance by Ortho SubstitutionRobert H. Saunders, M. J. Murray, and Forrest F. ClevelandCite this: J. Am. Chem. Soc. 1941, 63, 11, 3121–3123Publication Date (Print):November 1, 1941Publication History Published online1 May 2002Published inissue 1 November 1941https://doi.org/10.1021/ja01856a066RIGHTS & PERMISSIONSArticle Views45Altmetric-Citations13LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (324 KB) Get e-Alerts Get e-Alerts

The depolarization factors of Raman lines are determined by a method in which a Polaroid disk, so oriented that it passes light whose electric vector is horizontal, is placed between the Raman tube and the lens which condenses the scattered light on the slit of the spectrograph. Two exposures of equal duration are made, one with the arc below, the other with it at the side, of the horizontal Raman tube. The ratio of the intensities in the two exposures (depolarization factor) is determined by comparison with the lines of seven argon spectra produced by argon light of known intensity ratios. Important advantages of the method are the comparatively short exposure times and the elimination of errors due to the polarization characteristics of the spectrograph. Results for the depolarization factors of Raman lines obtained from a mixture of benzene and carbon tetrachloride are given and comparison with previous data for these compounds is made.

Raman displacements, estimated intensities and depolarization factors have been obtained for CH3CH2C≡CH, CH3(CH2)2C≡CH, CH3(CH2)3C≡CH, CH3CH2C≡CCH2CH3, CH3(CH2)2C≡C(CH2)2CH3, and CH3(CH2)4C≡CCl. The data obtained in the 2200 cm−1 region were [2068(1)P], 2118(10)0.5, 2158(3)0.5; [2064(0)], 2118(10)0.5; 2071(0), 2094(0), 2118(10)0.4; 2200(1)P, 2231(9)0.4, 2247(8)0.4, 2301(6)0.4; 2234(10)0.5, 2292(6)0.5; 2148(1)P, 2194(1)P, and 2243(10)0.4, respectively. Unusual features are the appearance of the second strong line at 2158 cm−1 in the spectrum of 1-butyne and the absence of the line near 2245 cm−1 in the spectrum of 4-octyne. Introduction of the Cl atom in the last compound radically modifies the spectrum in this region.

Displacements, estimated intensities, and depolarization factors are listed for the main lines of diethyl ether, di-n-propyl ether, di-isopropyl ether, di-n-butyl ether, di-isobutyl ether, di-n-amyl ether, and di-isoamyl ether. All the frequencies in the 2900 cm—1 region are polarized, except the one near 2970 cm—1 which is, without exception, highly depolarized.

Measurements, with the BRAHMS detector, of the antiproton-to-proton ratio at midrapidities and forward rapidities, are presented for Au+Au reactions at square root of [s(NN)] = 130 GeV, and for three different collision centralities. For collisions in the 0%-40% centrality range, we find N(&pmacr;)/N(p) = 0.64+/-0.04((stat))+/-0.06((syst)) at y approximately 0, 0.66+/-0.03+/-0.06 at y approximately 0.7, and 0.41+/-0.04+/-0.06 at y approximately 2. The ratios are found to be nearly independent of collision centrality and transverse momentum. The antiproton and proton rapidity densities vary differently with rapidity, and indicate a significant degree of collision transparency, although a net-baryon free midrapidity plateau (Bjorken limit) is not yet reached.

The NA44 experiment has measured single-particle inclusive spectra for charged pions, kaons, and protons as a function of transverse mass near midrapidity in 158A GeV/c PbϩPb collisions.From the particle mass dependence of the observed m T distributions, we are able to deduce a value of about 120 MeV for the temperature at thermal freeze-out.From the observed ratios of the rapidity densities, we find values of the chemical potentials for light and strange quarks and a chemical freeze-out temperature of approximately 140 MeV.

The HELIOS experiment has measured inclusivep ⊥ spectra of negative particles in the rapidity region 1.0<y<1.9. The general shape of thep ⊥ spectra in p +W, O+W and S+W is similar, but cannot be described by a single exponential. Compared to p+p collisions, an excess is observed for low and highp ⊥. This effect increases with the projectile mass. Except for very lowE ⊥, the average transverse momentum <p ⊥> is found to be approximately constant up to the highest accessible values ofE ⊥.

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTThe Structure of Ketene Dimer1Harvey J. Taufen and M. J. MurrayCite this: J. Am. Chem. Soc. 1945, 67, 5, 754–757Publication Date (Print):May 1, 1945Publication History Published online1 May 2002Published inissue 1 May 1945https://doi.org/10.1021/ja01221a017RIGHTS & PERMISSIONSArticle Views89Altmetric-Citations12LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (466 KB) Get e-Alerts Get e-Alerts

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTRaman Spectra of Acetylenes. III. Five Monosubstituted and Four Disubstituted AcetylenesForrest F. Cleveland and M. J. MurrayCite this: J. Am. Chem. Soc. 1940, 62, 11, 3185–3188Publication Date (Print):November 1, 1940Publication History Published online1 May 2002Published inissue 1 November 1940https://doi.org/10.1021/ja01868a082RIGHTS & PERMISSIONSArticle Views40Altmetric-Citations10LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (422 KB) Get e-Alerts Get e-Alerts

The RHIC zero-degree calorimeters provide common event characterization in the four heavy ion experiments which recently completed their first data taking run. Here, we describe simulations which lead to the design of these devices, teastbeam performance and initial experience at RHIC.

The RHIC zero-degree calorimeters provide common event characterization in the four heavy ion experiments which recently completed their first data taking run. Here, we describe simulations which lead to the design of these devices, teastbeam performance and initial experience at RHIC.

BRAHMS has the ability to study relativistic heavy ion collisions from the final freeze-out of hadrons all the way back to the initial wavefunction of the gold nuclei. This is accomplished by studying hadrons with a very wide range of momenta and angles. In doing so we can scan various phases of QCD, from a hadron gas, to a quark gluon plasma and perhaps to a colour glass condensate.

The kinetic energy variation of emitted light clusters has been employed as a clock to explore the time evolution of the temperature for thermalizing composite systems produced in the reactions of 26A, 35A and 47A MeV 64 Zn with 58 Ni, 92 Mo and 197 Au.For each system investigated, the double isotope ratio temperature curve exhibits a high maximum apparent temperature, in the range of 10-25 MeV, at high ejectile velocity.These maximum values increase with increasing projectile energy and decrease with increasing target mass.The time at which the maximum in the temperature curve is reached ranges from 80 to 130 fm/c after contact.For each different target, the subsequent cooling curves for all three projectile energies are quite similar.Temperatures comparable to those of limiting temperature systematics are reached 30 to 40 fm/c after the times corresponding to the maxima, at a time when AMD-V transport model calculations predict entry into the final evaporative or fragmentation stage of de-excitation of the hot composite systems.Evidence for the establishment of thermal and chemical equilibrium is discussed.

Abstract A 13 C‐NMR investigation was carried out in aid of direct detection of crosslinks in hydrocarbons with the future objective of studying radiation‐induced crosslinking in polyethylene by a direct method. The resonance signal due to a tertiary carbon atom appropriate to a crosslink far remote from molecular ends has been identified in a definitive manner with the aid of the H‐shaped model compound 1,1,2,2‐tetra(tridecyl)ethane synthetized in Part I of this study. This identification was then put to use in the examination of the irradiated linear paraffins n ‐hexadecane and n ‐eicosane, where it enabled the detection of radiation‐induced crosslinks. This crosslinking could then be associated with corresponding changes in molecular weight (dimer, trimer formation) as revealed by discrete peaks in the gel‐permeation chromatograms of the same samples and randomness of the crosslinking process in the liquid state of these compounds being inferred.

Invariant pT spectra and rapidity densities covering a large rapidity range (−0.1<y<3.5) are presented for π± and K± mesons from central Au + Au collisions at sNN=62.4 GeV. The mid-rapidity yields of meson particles relative to their anti-particles are found to be close to unity (π−/π+∼1, K−/K+∼0.85) while the anti-proton to proton ratio is p¯/p∼0.49. The rapidity dependence of the π−/π+ ratio is consistent with a small increase towards forward rapidities while the K−/K+ and p¯/p ratios show a steep decrease to ∼0.3 for kaons and 0.022 for protons at y∼3. It is observed that the kaon production relative to its own anti-particle as well as to pion production in wide rapidity and energy ranges shows an apparent universal behavior consistent with the baryo-chemical potential, as deduced from the p¯/p ratio, being the driving parameter.

Raman frequencies, estimated intensities and depolarization factors are listed for n-propylphenyl, n-butylphenyl, ethylbenzyl, n-butylbenzyl and dibenzyl ethers. Intense frequencies characteristic of monosubstituted benzenes whose values were constant in the five ethers are 618(5)0.8, 1001(10)0.1, 1029(7)0.3, 1156(4)0.8, 1176(4)0.8, 1588 and 1604 (6)0.7, 3058(9)0.3. Frequencies characteristic of the C–O–C bond may be those near 440, 900 and 1125 cm—1.

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTIsomerization of Certain Olefins by Silica Gel at Room TemperatureW. S. Gallaway and M. J. MurrayCite this: J. Am. Chem. Soc. 1948, 70, 7, 2584–2586Publication Date (Print):July 1, 1948Publication History Published online1 May 2002Published inissue 1 July 1948https://doi.org/10.1021/ja01187a086Request reuse permissions Article Views125Altmetric-Citations11LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (287 KB) Get e-Alertsclose Get e-Alerts

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTRaman Spectra of Four Pairs of meso and dl Disubstituted ButanesHarvey J. Taufen, M. J. Murray, and Forrest F. ClevelandCite this: J. Am. Chem. Soc. 1943, 65, 6, 1130–1134Publication Date (Print):June 1, 1943Publication History Published online1 May 2002Published inissue 1 June 1943https://doi.org/10.1021/ja01246a033RIGHTS & PERMISSIONSArticle Views35Altmetric-Citations11LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (462 KB) Get e-Alerts Get e-Alerts

π+π+π+ correlations from sulphur-lead collisions at 200 GeV/c per nucleon are presented as measured by the focusing spectrometer of experiment NA44 at CERN. We have investigated the three-pion correlation function at mid-rapidity and found that a genuine three-body correlation is suppressed. A possible interpretation of this result is that the emission of particles is partially coherent.

Proton distributions at mid-rapidity (2 ≤ y ≤ 3) have been measured for 158A·GeV Pb+Pb collisions in the focusing spectrometer experiment NA44 at CERN. From baryon number conservation and by comparing the experimentally measured dNdy distribution with the transport model RQMD, we conclude that a rather high degree of nuclear stopping has been reached for the truly heavy-ion collisions at these energies. Transverse mass distributions exhibit characteristically thermal shapes and the slope parameters increase with the mass of the colliding system.

Reaction mechanisms and multifragmentation processes have been studied for 64Zn+58Ni collisions at intermediate energies with the help of antisymmetrized molecular dynamics (AMD-V) model calculations. Experimental energy spectra, angular distributions, charge distributions, and isotope distributions, classified by their associated charged particle multiplicities, are compared with the results of the AMD-V calculations. In general the experimental results are reasonably well reproduced by the calculations. The multifragmentation observed experimentally at all incident energies is also reproduced by the AMD-V calculations. A detailed study of AMD-V events reveals that, in nucleon transport, the reaction shows some transparency, whereas in energy transport the reaction is much less transparent at all incident energies studied here. The transparency in the nucleon transport indicates that, even for central collisions, about 75% of the projectile nucleons appear in the forward direction. In energy transport about 80% of the initial kinetic energy of the projectile in the center- of-mass frame is dissipated. The detailed study of AMD-V events also elucidates the dynamics of the multifragmentation process. The study suggests that, at 35A MeV, the semitransparency and thermal expansion are the dominant mechanisms for the multifragmentation process, whereas at 49A MeV and higher incident energies a nuclear compression occurs at an early stage of the reaction and plays an important role in the multifragmentation process in addition to that of the thermal expansion and the semitransparency.Received 4 February 2000DOI:https://doi.org/10.1103/PhysRevC.62.034601©2000 American Physical Society

We report on the production of low-mass electron pairs and muon pairs in p-Be collisions at 450 GeV/c at the CERN SPS. For both electron and muon pairs the low-mass spectrum can be explained satisfactorily by lepton pairs from hadronic decays, and there is no need to invoke any "unconventional" source. The normalisation of the major hadronic sources is set by the data. The upper limit, at 90% confidence level, on any new source of lepton pairs is ∼20% of the hadronic decay contribution for muons, and ∼40% for electrons.

Nuclear caloric curves have been analyzed using an expanding Fermi gas hypothesis to extract average nuclear densities. In this approach the observed flattening of the caloric curves reflects progressively increasing expansion with increasing excitation energy. This expansion results in a corresponding decrease in the density and Fermi energy of the excited system. For nuclei of medium to heavy mass apparent densities $\ensuremath{\sim}0.4{\ensuremath{\rho}}_{0}$ are reached at the higher excitation energies.

We report on the first measurement of mutual Coulomb dissociation in heavy-ion collisions. We employ forward calorimeters to measure neutron multiplicity at beam rapidity. The cross section for simultaneous electromagnetic breakup of Au nuclei at a nucleon-nucleon center of mass energy $\sqrt{{s}_{\mathrm{NN}}}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}130\mathrm{GeV}$ is ${\ensuremath{\sigma}}_{\mathrm{MCD}}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}3.67\ifmmode\pm\else\textpm\fi{}0.26$ barns, which is comparable to the geometrical cross section. The ratio of the electromagnetic to the total cross section is in good agreement with calculations, as is the neutron multiplicity distribution.

Neutrons and isotopically resolved light charged particles have been detected in coincidence with evaporation residues produced in the reaction $E/A=11 \mathrm{MeV}$ ${}^{60}\mathrm{Ni}{+}^{100}\mathrm{Mo}.$ Multiplicities of evaporated particle-unstable clusters have been determined from correlations in the emission of these light particles. The decay of the short-lived ${}^{5}\mathrm{He}$ and ${}^{8}\mathrm{Be}$ ${(E}^{*}=3.04 \mathrm{MeV})$ states was found to be affected by the Coulomb field of the compound nucleus in accordance with theoretical estimates. The contributions to the measured kinetic-energy distributions of stable fragments from the sequential decay of the unstable clusters was examined. Overall, the contributions from secondary fragments do not greatly influence the spectral shapes and specifically the location of the spectral peaks are not significantly shifted down in energy due to the presence of these secondary fragments. Therefore contrary to the suggestion of Charity et al. [Phys. Rev. C 56, 873 (1997)], the lower peak energy of the experimental $\ensuremath{\alpha}$-particle spectrum as compared to standard statistical-model calculations cannot be attributed to sequential $\ensuremath{\alpha}$ particles from ${}^{5}\mathrm{He}$ and other clusters. Only for the extreme ``subbarrier'' regions of the $\ensuremath{\alpha}$-particle, deuteron, ${}^{6,7}\mathrm{Li},$ and ${}^{8}\mathrm{Be}$ spectra was the sequential contribution found to be dominant. Statistical-model calculations incorporating large initial deformations are shown to provide enhancements in the yield of low-energy fragments which are roughly appropriate for all the detected isotopes. This suggests that the origin of the sub-barrier enhancements may be a result of evaporation from highly deformed systems which are either produced dynamically during the fusion process or by thermal shape fluctuations.

A search for non-statistical fluctuations was performed in 200 GeV per nucleon oxygen and sulphur ion-emulsion interactions selected by a high transverse energy trigger. No clear signal of dynamical correlations or of unusual fluctuations was found.

A wide variety of observables indicate that maximal fluctuations in the disassembly of hot nuclei with $A\ensuremath{\sim}36$ occur at an excitation energy of $5.6\ifmmode\pm\else\textpm\fi{}0.5\phantom{\rule{0.3em}{0ex}}\text{MeV}∕\text{nucleon}$ and temperature of $8.3\ifmmode\pm\else\textpm\fi{}0.5\phantom{\rule{0.3em}{0ex}}\text{MeV}$. Associated with this point of maximal fluctuations are a number of quantitative indicators of apparent critical behavior. The associated caloric curve does not appear to show a flattening such as that seen for heavier systems. This suggests that, in contrast to similar signals seen for liquid-gas transitions in heavier nuclei, the observed behavior in these very light nuclei is associated with a transition much closer to the critical point.

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTRaman Spectra of Acetylenes. II. Displacements and Depolarization Factors for Phenylacetylene and Derivatives of the Type C6H5C≡CRM. J. Murray and Forrest F. ClevelandCite this: J. Am. Chem. Soc. 1939, 61, 12, 3546–3549Publication Date (Print):December 1, 1939Publication History Published online1 May 2002Published inissue 1 December 1939https://doi.org/10.1021/ja01267a093RIGHTS & PERMISSIONSArticle Views50Altmetric-Citations8LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (459 KB) Get e-Alerts Get e-Alerts

The problem of benign overfitting asks whether it is possible for a model to perfectly fit noisy training data and still generalize well. We study benign overfitting in two-layer leaky ReLU networks trained with the hinge loss on a binary classification task. We consider input data which can be decomposed into the sum of a common signal and a random noise component, which lie on subspaces orthogonal to one another. We characterize conditions on the signal to noise ratio (SNR) of the model parameters giving rise to benign versus non-benign, or harmful, overfitting: in particular, if the SNR is high then benign overfitting occurs, conversely if the SNR is low then harmful overfitting occurs. We attribute both benign and non-benign overfitting to an approximate margin maximization property and show that leaky ReLU networks trained on hinge loss with Gradient Descent (GD) satisfy this property. In contrast to prior work we do not require near orthogonality conditions on the training data: notably, for input dimension $d$ and training sample size $n$, while prior work shows asymptotically optimal error when $d = \Omega(n^2 \log n)$, here we require only $d = \Omega\left(n \log \frac{1}{\epsilon}\right)$ to obtain error within $\epsilon$ of optimal.

Premature peripheral artery disease (PAD), defined by lower extremity revascularization (LER) at age ≤ 50 years, is associated with poor major adverse limb events. The early onset of disease is thought to be influenced by genetic factors that regulate homeostasis of the vascular wall and coagulation. The aim of this study is to investigate the effect of anticoagulation as an adjunct to antiplatelet therapy on the outcomes of LER in patients with premature PAD.There were 8,804 patients with premature PAD on pre- and post-operative antiplatelet therapy only and 1,236 patients on pre- and post-operative anticoagulation plus antiplatelet therapy in the Vascular Quality Initiative (VQI) peripheral vascular intervention, infra-, and suprainguinal files. Propensity score matching (2:1) was performed between patients with premature PAD who were on antiplatelet therapy and those on anticoagulation plus antiplatelet therapy. Perioperative and one-year outcomes were analyzed including reintervention, major amputation, and mortality.Patients on anticoagulation were more likely to have coronary artery disease (48.7% vs 41.2%, P<.001), congestive heart failure (20.2% vs 13.1%, P<.001), and have undergone prior LER (73.9% vs 49.2%, P<.001) compared to patients on antiplatelet therapy only. They were also less likely to be independently ambulatory (74.2% vs 81.8%, P<.001) and be on a statin medication (66.8% vs 74.3%, P<.001) compared to patients on antiplatelet therapy only. Patients on anticoagulation were also less likely to be treated for claudication (38.1% vs 48.6%, P<.001), and less likely to be treated with an endovascular procedure (64.8% vs 73.8%, P<.001). After matching for baseline characteristics, there were 1,256 patients on antiplatelet therapy only and 628 patients on anticoagulation. Patients on anticoagulation were more likely to require a return to the operating room (3.7% vs 1.6%, P<.001) and had higher perioperatively mortality (1.1% vs 0.3%, P=.032), but major amputation was not significantly different (1.8% vs 1.6%, P=.798) compared to patients on antiplatelet therapy alone. At one-year, amputation-free survival was higher in patients on antiplatelets only compared to patients on anticoagulation and antiplatelet medications (87.5% vs 80.9%, log-rank P=.001).Anticoagulation in addition to antiplatelet therapy in patients with premature PAD undergoing lower extremity revascularization is associated with increased reintervention and mortality at one year.

Self-consistent coalescence model analyses of light particle emission have been used to follow the evolution of the temperatures and densities of A≈110 nuclei produced in violent collisions induced by four different 47 AMeV projectiles. The degree of expansion of the emitting system increases with increasing projectile mass. The caloric curve derived for these expanding A≈110 nuclei plateaus near T=7 MeV. The plateau extends from 3.5 to 6.9 MeV/u excitation energy.

K+K+ and K−K− correlations from S+Pb collisions at 200 GeV/c per nucleon and K+K+ correlations from p+Pb collisions at 450 GeV/c per nucleon, are presented as measured by the focusing spectrometer of the NA44 experiment at CERN. Multidimensional fits are performed in order to characterize the kaon-emission volume, which is found to be smaller than the pion-emission volume.

Two-particle interferometry of positive kaons is studied in Pb+Pb collisions at mean transverse momenta <p(T)> approximately 0.25 and 0.91 GeV/c. A three-dimensional analysis was applied to the lower p(T) data, while a two-dimensional analysis was used for the higher p(T) data. We find that the source-size parameters are consistent with the m(T) scaling curve observed in pion-correlation measurements in the same collisions, and that the duration time of kaon emission is consistent with zero within the experimental sensitivity.

Transverse-energy distributions have been measured for the collisions of the 32S nucleus with Al, Ag, W, Pt, Pb, and U target nuclei, at an incident energy of 200 GeV per nucleon. The shapes of these distribution reflect the geometry of the collisions, including the deformation effects. For central collisions, the transverse-energy production in the region −0.1<ηlab<2.9 increases approximately as A0.5, where A is the atomic mass number of the target. This increase is accompanied by a relative depletion in the forward region ηlab > 2.9. These results are compared with those obtained under similar conditions with incident 16O nuclei. A comparison is also made with the predictions of a Monte Carlo generator based on the dual parton model. Finally, we give estimates of the energy density reached and its dependence on the atomic mass number of the projectile.

Raman spectra are listed for series of acetylenic bromides, iodides, and ketones, and for ascaridole, 1,3-dioxane, ethyl-p-toluenesulfonate, and for the cis- and trans−1,2-diacetoxycyclohexanes. Depolarization factors (when obtained) and relative intensities were measured by use of a Gaertner microdensitometer.

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTRaman Spectra of Acetylenes. V. Alkyl AcetylenesM. J. Murray and Forrest F. ClevelandCite this: J. Am. Chem. Soc. 1941, 63, 6, 1718–1721Publication Date (Print):June 1, 1941Publication History Published online1 May 2002Published inissue 1 June 1941https://doi.org/10.1021/ja01851a063RIGHTS & PERMISSIONSArticle Views46Altmetric-Citations8LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (371 KB) Get e-Alerts Get e-Alerts

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTThe Aldol Condensation. II. The Reaction of Isobutyraldehyde with its Aldol1Robert H. Saunders, M. J. Murray, and Forrest F. ClevelandCite this: J. Am. Chem. Soc. 1943, 65, 9, 1714–1717Publication Date (Print):September 1, 1943Publication History Published online1 May 2002Published inissue 1 September 1943https://doi.org/10.1021/ja01249a018RIGHTS & PERMISSIONSArticle Views586Altmetric-Citations7LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (413 KB) Get e-Alerts Get e-Alerts

Single particle distributions from heavy-ion collisions show the effect of Coulomb interactions on the final state. While a rather strong effect is seen in the ratio π−π+ from central 158A·GeV/c Pb+Pb collisions, at most a small enhancement is found in the ratios from S+S and S+Pb collisions at 200A·GeV/c.

The purpose of BRAHMS is to survey the dynamics of relativistic heavy ion (as well as pp and d-A) collisions over a very wide range of rapidity and transverse momentum. The sum of these data may give us a glimpse of the initial state of the system, its transverse and longitudinal evolution and how the nature of the system changes with time. Here I will concentrate on the origin and dynamics of the light flavors, i.e. the creation and transport of the up, down and strange quarks. The results presented here are certainly not the end of the story. It is my hope that in a few years new detectors will reveal the rapidity dependence of the charm and bottom quarks.

The combined zero degree calorimeter (ZDC) is a combination of sampling quartz/tungsten electromagnetic and hadronic calorimeters. Two identical combined calorimeters are located in the LHC tunnel at CERN at the straight section ∼140 m on each side of the CMS interaction vertex and between the two beam pipes. They will detect very forward |η| ≥ 8.5 photons and neutrons. ZDC information can be used for a variety of physics measurements as well as improving the collision centrality determination in heavy-ion collisions. Results are presented for ZDC performance studies with the CERN SPS H2 test beam.

Possible structures for radicals formed from sulphur and sulphur nitrides in sulphuric acid, oleum, and antimony pentafluoride are deduced from their electron spin resonance spectra in the fluid and solid state. The form of the 33S hyperfine tensor leads to the postulate that the sulphur radical is σ*, possibly of the form X2S–SX2+, where X is derived from the medium. The 14N tensor for the sulphur nitride radical is in accord with the formulation S2N2+, having a square-planar structure with an in-plane distortion.

We have measured the distributions of protons and deuterons produced in the 20% most central Au+Au collisions at RHIC ( √ s NN = 200 GeV) over a very wide range of transverse and longitudinal momentum.Near midrapidity we have also measured the distribution of antiprotons and antideuterons.We present our results in the context of coalescence models.In particular we extract the "homogeneity volume" and the average phase-space density for protons and antiprotons.Near central rapidity the coalescence parameter B2(pT ) and the space-averaged phase-space density f (pT ) are very similar for both protons and antiprotons.For protons we see little variation of either B2(pT ) or the space-averaged phase-space density as the rapidity increases from 0 to 3.However, these quantities depend strongly on pT at all rapidities.These results are in contrast to data from lower energy collisions where the proton and antiproton phase-space densities are different at y=0 and both B2 and f depend strongly on rapidity.

The carbon isotope shift in the frequency near 2200 cm—1 has been calculated for H–C13≡C12–H, CH3–C12≡C13–H, CH3–C13≡C12–H and CH3–C13≡C12–CH3 from the valence force equations, assuming a four-mass, linear oscillator. The results were —27, —26, —50 and —33.5 cm—1, respectively. Weak lines which may correspond to isotope shifts were observed for the monosubstituted acetylenes, 1-heptyne (—21 and —53 cm—1), 4-methoxy-1-butyne (—24 and —53) and phenylethyne (—24 and —54), and for the disubstituted acetylenes, 1-phenyl-1-butyn-3-one (—37), 1-phenyl-1-butynol-3 (—33), 1-phenyl-1-butyne (—29), 3-hexyne (—26), 3-octyne (—36) and 5-decyne (—38 cm—1). Shifts of —27 and —33 cm—1 for acetylene and dimethylacetylene, respectively, have been reported by Glockler and Renfrew.

The infra-red spectrum of methylphenylacetylene between 500 and 2300 cm—1 has been measured with the aid of a prism spectrometer. The results are compared with the Raman spectrum of this compound, previously measured by the authors. The results are inconclusive as regards the assignment of the fundamental whose overtone, according to Badger's hypothesis, is responsible for the resonance splitting of the frequency near 2230 cm—1.

The NA44 Collaboration has measured yields and differential distributions of K+, K−, π+, π− in transverse kinetic energy and rapidity, around the center-of-mass rapidity in 158 A GeV/c Pb+Pb collisions at the CERN SPS. A considerable enhancement of K+ production per π is observed, as compared to p+p collisions at this energy. To illustrate the importance of secondary hadron rescattering as an enhancement mechanism, we compare strangeness production at the SPS and AGS with predictions of the transport model RQMD.

3pi- correlations from Pb+Pb collisions at 158 GeV/c per nucleon are presented as measured by the focusing spectrometer of the NA44 experiment at CERN. The three-body effect is found to be stronger for PbPb than for SPb. The two-dimensional three-particle correlation function is also measured and the longitudinal extension of the source is larger than the transverse extension.

Experiment NA44 has measured proton and antiproton distributions at midrapidity in sulphur and proton collisions with nuclear targets at 200 and 450GeV/c per nucleon respectively. The inverse slopes of transverse mass distributions increase with system size for both protons and antiprotons but are slightly lower for antiprotons. This could happen if antiprotons are annihilated in the nuclear medium. The antiproton yield increases with system size and centrality and is largest at midrapidity. The proton yield also increases with system size and centrality, but decreases from backward rapidity to midrapidity. The stopping of protons at these energies lies between the full stopping and nuclear transparency scenarios. The data are in reasonable agreement with RQMD predictions except for the antiproton yields from sulphur-nucleus collisions.Received 25 August 1997DOI:https://doi.org/10.1103/PhysRevC.57.837©1998 American Physical Society

The abundances of light nuclei probe the later stages of the evolution of a system formed in a relativistic heavy-ion collision. After the system has cooled and expanded, nucleons in close proximity and moving with small relative momenta coalesce to form nuclei. Light nuclei production enables the study of several topics, including the mechanism of composite particle production, freeze-out temperature, size of the interaction region, and entropy of the system. NA44 is the only relativistic heavy-ion experiment to have both deuteron and antideuteron results in both pA and AA collisions and the first CERN experiment to study the physics topics addressed by d and d production.

The transverse energy distributions have been measured for interactions of 32S nuclei with Al, Ag, W, Pt, Pb, and U targets, at an incident energy of 200 GeV per nucleon in the pseudorapidity region −0.1 < νlab < 5.5. These distributions are compared with those for 16OW interactions in the same pseudorapidity region and with earlier measurements performed with 16O and 32S projectiles in the region −0.1 < νlab < 2.9. These comparisons provide both a better understanding of the dynamics involved and improved estimates of stopping power and energy density.

The Zero Degree Calorimeter (ZDC) is integral part of the CMS experiment, especially, for heavy ion studies. The design of the ZDC includes two independent calorimeter sections: an electromagnetic section and a hadronic section. Sampling calorimeters using tungsten and quartz fibers have been chosen for the energy measurements. An overview of the ZDC is presented along with a current status of calorimeter’s preparation for Day 1 of LHC.

It has been suggested that galactic shock asymmetry induced by our galaxy's infall toward the Virgo Cluster may be a source of periodicity in cosmic ray exposure as the solar system oscillates perpendicular to the galactic plane, thereby, inducing an observed terrestrial periodicity in biodiversity. There are a number of plausible mechanisms by which cosmic rays might affect terrestrial biodiversity. Here we investigate one of these mechanisms, the consequent ionization and dissociation in the atmosphere, resulting in changes in atmospheric chemistry that culminate in the depletion of ozone and a resulting increase in the dangerous solar UVB flux on the ground. We use a heuristic model of the cosmic ray intensity enhancement originally suggested by Medvedev and Melott (2007) to compute steady state atmospheric effects. This paper is a reexamination of an issue we have studied before with a simplified approximation for the distribution of incidence angles. The new results are based on an improved ionization background computation averaged over a massive ensemble (about 7 × 10 5 ) shower simulations at various energies and incidence angles. We adopt a range with a minimal model and a fit to full exposure to the postulated extragalactic background. The atmospheric effects are greater than they were with our earlier, simplified ionization model. At the lower end of the intensity range, we find that the effects are too small to be of serious consequence. At the upper end of this range, ∼6% global average loss of ozone column density exceeds that currently experienced due to anthropogenic effects such as accumulated chlorofluorocarbons. We discuss some of the possible effects. The intensity of the atmospheric effects is less than those of a nearby supernova or galactic γ ray burst, but the duration of the effects would be about 10 6 times longer. Present UVB enhancement from current ozone depletion ∼3% is a documented stress on the biosphere, but a depletion of the magnitude found at the upper end of our range would approximately double the global average UVB flux. We conclude that for estimates at the upper end of the reasonable range of the cosmic ray variability over geologic time, the mechanism of atmospheric ozone depletion may provide a major biological stress, which could easily bring about major loss of biodiversity. It is possible that future high‐energy astrophysical observations will resolve the question of whether such depletion is likely.

The BRAHMS collaboration has measured transverse momentum spectra of pions, kaons, protons, and antiprotons at rapidities 0 and 3 for Cu+Cu collisions at $\sqrt{{s}_{\mathit{\text{NN}}}}=200$ GeV. As the collisions become more central the collective radial flow increases while the temperature of kinetic freeze-out decreases. The temperature is lower and the radial flow weaker at forward rapidity. Pion and kaon yields with transverse momenta between 1.5 and $2.5 \mathrm{GeV}/c$ are suppressed for central collisions relative to scaled $p+p$ collisions. This suppression, which increases as the collisions become more central, is consistent with jet quenching models and is also present with comparable magnitude at forward rapidity. At such rapidities, initial state effects may also be present and persistence of the meson suppression to high rapidity may reflect a combination of jet quenching and nuclear shadowing. The ratio of protons to mesons increases as the collisions become more central and is largest at forward rapidities.

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.

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTRaman Spectra of Some Aromatic Carbonyl and Nitro CompoundsM. J. Murray, Forrest F. Cleveland, and Robert H. SaundersCite this: J. Am. Chem. Soc. 1942, 64, 5, 1181–1184Publication Date (Print):May 1, 1942Publication History Published online1 May 2002Published inissue 1 May 1942https://doi.org/10.1021/ja01257a051RIGHTS & PERMISSIONSArticle Views444Altmetric-Citations6LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (351 KB) Get e-Alerts Get e-Alerts

The invariant cross section as a function of transverse momentum for antideuterons produced in $158A\mathrm{GeV}/c$ per nucleon $\mathrm{Pb}+\mathrm{Pb}$ central collisions has been measured by the NA44 experiment at CERN. This measurement, together with a measurement of antiprotons, allows for the determination of the antideuteron coalescence parameter. The extracted coalescence radius is found to agree with the deuteron coalescence radius and radii determined from two particle correlations.

Diffractive dissociation of nuclei (Be, Al, W) in collisions with 450 GeV/c protons,pA→pX, has been measured with the HELIOS spectrometer at the CERN Super Proton synchrotron. The dependence of the single-diffraction cross-section on the nuclear massA can be parametrized as σSD mb×A 0.35±0.02, showing the peripheral nature of the process. The differential cross-section dσSD=(3.8±0.3)mb ×A 0.35±0.02, is exponential with the slope parameter, increasing from 6.2±0.4 (GeV/c)−2 for beryllium to 7.9±0.5 (GeV/c)−2 for tungsten. The slope parameter also increases with increasing massM X of the diffractively produced state. The rapidity, multiplicity, and transverse-momentum distributions of the particles of the diffractively produced stateX show a longitudinal phase-space population and are remarkably insensitive to the nuclear mass. This, together with theA 1/3 dependence of σSD, suggests that the dominant process of nuclear diffractive excitation is the dissociation of single nucleons.

Proton and deuteron production has been observed in S+S and S+Pb collisions at 200 A $\cdot$ GeV and in Pb+Pb reactions at 158 A $\cdot$ GeV at the CERN SPS accelerator. For Pb+Pb triton production was also measured. The p and d spectra as well as the p and t spectra were observed in similar rapidity ranges and over similar ranges of transverse momenta per nucleon, making it possible to interpret the cross sections of the composite particles in terms of coalescence mechanisms. Volumes of homogeneity were extracted and compared to pion-pair HBT interferometry results. Special attention is given to the dependence on transverse mass, centrality and rapidity.

We present spectra of charged pions and protons in 0–10% central Au + Au collisions at sNN=200GeV at mid-rapidity (y=0) and forward pseudorapidity (η=2.2) measured with the BRAHMS experiment at RHIC. The spectra are compared to spectra from p+p collisions at the same energy scaled by the number of binary collisions. The resulting nuclear modification factors for central Au + Au collisions at both y=0 and η=2.2 exhibit suppression for charged pions but not for (anti-) protons at intermediate pT. The p¯/π− ratios have been measured up to pT∼3GeV/c at the two rapidities and the results indicate that a significant fraction of the charged hadrons produced at intermediate pT range are (anti-) protons at both mid-rapidity and η=2.2.

We propose a measurement of leading neutrons spectra at LHC in order to extract inclusive $\pi^+ p$ and $\pi^+\pi^+$ cross-sections with high $p_T$ jets production. The cross-sections for these processes are simulated with the use of parton distributions in hadrons. In this work we estimate the possibility to extract parton distributions in the pion from the data on these cross-sections and also search for signatures of fundamental differences in the pion and proton structure.

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTRaman Spectra of Acetylenes. I. Derivatives of Phenylacetylene, C6H5C≡CRM. J. Murray and Forrest F. ClevelandCite this: J. Am. Chem. Soc. 1938, 60, 11, 2664–2666Publication Date (Print):November 1, 1938Publication History Published online1 May 2002Published inissue 1 November 1938https://doi.org/10.1021/ja01278a036RIGHTS & PERMISSIONSArticle Views41Altmetric-Citations5LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (358 KB) Get e-Alerts Get e-Alerts

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTThe Aldol Condensation. III. Aldol-aldehyde Addition Products and their DerivativesRobert H. Saunders and M. J. MurrayCite this: J. Am. Chem. Soc. 1944, 66, 2, 206–208Publication Date (Print):February 1, 1944Publication History Published online1 May 2002Published inissue 1 February 1944https://doi.org/10.1021/ja01230a014RIGHTS & PERMISSIONSArticle Views263Altmetric-Citations4LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (368 KB) Get e-Alerts Get e-Alerts

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTAtmospheric Oxidation of 6-Dodecyne*M. J. Murray and Forrest F. ClevelandCite this: J. Am. Chem. Soc. 1941, 63, 5, 1363–1364Publication Date (Print):May 1, 1941Publication History Published online1 May 2002Published inissue 1 May 1941https://doi.org/10.1021/ja01850a064RIGHTS & PERMISSIONSArticle Views24Altmetric-Citations5LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (226 KB) Get e-Alerts Get e-Alerts

Raman displacements, estimated intensities and depolarization factors have been measured for 1-bromo-dodecane in the liquid state. The strong, polarized frequencies 563 and 647, characteristic of the —CH2Br group, have the same constant values as do other members of the series from n-propyl to n-heptyl bromide inclusive. The weak, depolarized frequency 3009 is also probably associated with this group. Five of the observed frequencies agree rather well with values of infra-red active chain and end frequencies recently calculated by Whitcomb, Nielsen and Thomas for undecane, the mean deviation being 30 cm—1. The intense, highly polarized frequencies 2850 and 2930 and the less intense, depolarized frequency 2961 appear in the bromide spectrum as well as in the spectra of many other compounds containing alkyl radicals.

Premature peripheral artery disease (PAD), defined as ≤ 50 years of age, is associated with poor outcomes following lower extremity revascularization (LER). However, the specific characteristics and outcomes of this group of patients compared to those at the common age undergoing revascularization have not been examined. The aim of this study is to compare patients with early versus late onset premature PAD undergoing LER focusing on major adverse limb events (MALEs).All LER procedures (open and endovascular) in the Vascular Quality Initiative (VQI) were reviewed. A histogram of patient age at the time of initial LER (no prior LER) was used to define the common age, which included all patients within one standard deviation of the mean. Characteristics and outcomes of patients with premature PAD were compared to patients treated at the common age of presentation undergoing LER.A histogram of all patients undergoing LER was used to define 60 to 80 years as the common age. Patients with premature PAD were more likely to be female, African American, and Hispanic compared to patients at the common age. Patients with premature PAD were also more likely to have insulin-dependent diabetes, be current smokers, on dialysis, and be treated for claudication. Patients with premature PAD were less likely to have Transatlantic Intersociety Consensus (TASC II) C or D disease and were less likely to be on antiplatelets and statins. These differences were more pronounced in patients with chronic limb-threatening ischemia (CLTI). Cox proportional hazards regression demonstrated that premature PAD was independently associated with major adverse limb events (MALEs) at 1-year for patients with claudication (HR:1.7, 95% CI:1.4-2.0) and CLTI (HR:1.3, 95% CI:1.2-1.5) compared to patients 60 to 80 years of age.Patients with premature PAD have significant differences in characteristics compared to patients treated at the common age. Vascular providers should emphasize medical therapy prior to LER given the lower rates of medical optimization and worse 1-year MALEs in patients with premature PAD.

The NA44 Collaboration has measured charged kaon and pion distributions at midrapidity in sulphur and proton collisions with nuclear targets at 200 and $450 \mathrm{GeV}/c$ per nucleon, respectively. The inverse slopes of kaons, are larger than those of pions. The difference in the inverse slopes of pions, kaons, and protons, all measured in our spectrometer, increases with system size and is consistent with the buildup of collective flow for larger systems. The target dependence of both the yields and inverse slopes is stronger for the sulphur beam, suggesting the increased importance of secondary rescattering for $\mathrm{S}A$ reactions. The rapidity density $dN/dy$ of both ${K}^{+}$ and ${K}^{\ensuremath{-}}$ increases more rapidly with system size than for ${\ensuremath{\pi}}^{+}$ in a similar rapidity region. This trend continues with increasing centrality, and according to RQMD, it is caused by secondary reactions between mesons and baryons. The ${K}^{\ensuremath{-}}{/K}^{+}$ ratio falls with increasing system size but more slowly than the $\overline{p}/p$ ratio. The ${\ensuremath{\pi}}^{\ensuremath{-}}/{\ensuremath{\pi}}^{+}$ ratio is close to unity for all systems. From $p\mathrm{Be}$ to $\mathrm{SPb}$ the ${K}^{+}/p$ ratio decreases while ${K}^{\ensuremath{-}}/\overline{p}$ increases and $\sqrt{{(K}^{+}\ensuremath{\cdot}{K}^{\ensuremath{-}})/(p\ensuremath{\cdot}\overline{p})}$ stays constant. These data suggest that as larger nuclei collide, the resulting system has a larger transverse expansion and baryon density and an increasing fraction of strange quarks.

High energy heavy ion collisions provide the opportunity to create hadronic matter at high energy density and study its properties. In order to do this, one must characterize the collisions, ascertain the size and density of the hot system in the central region of the nucleus-nucleus system, and determine the energy density achieved. Furthermore, one needs to determine whether or not the system approaches equilibrium so thermodynamic descriptions may be used. One of the experimental tools available is the study of two-particle correlations to map the space-time extent of the system when the hadrons decouple. Other observables include the flow of energy and charged particles transverse to the beam and the rapidity distribution of protons to indicate the amount of stopping and randomization of the incoming energy. The transverse mass distributions of hadrons reflect the temperature of the system at freezeout and effects of radial expansion. The production ratios of different particles are related to the extent of chemical equilibrium reached in the collision and subsequent evolution of the hadron gas. The NA44 Experiment at CERN can address all of these observables, though here the author focus mainly on correlation measurements. Kaons and pions are emitted rather late in the evolution of a heavy ion collision, at the time of {open_quotes}freezeout{close_quotes} when the hadrons cease to interact. Their correlations reflect the space-time evolution of the later part of the collision. In addition to characterizing the collision, correlations can signal a phase transition as they measure the duration of hadronization and particle emission, which should be long in both a first- or second-order phase transition. Furthermore, correlation measurements offer an important tool to help disentangle effects of expansion from the freezeout temperature reflected in the single particle spectra.