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This short paper shows that Rutherford first discussed in 1906, when he was at McGill, the possibility of determining the structure of the atom by measuring the diffusion of alpha particles in an e...

Predictions made in Albacete {\it et al} prior to the LHC $p+$Pb run at $\sqrt{s_{NN}} = 5$ TeV are compared to currently available data. Some predictions shown here have been updated by including the same experimental cuts as the data. Some additional predictions are also presented, especially for quarkonia, that were provided to the experiments before the data were made public but were too late for the original publication are also shown here., 55 pages 35 figures

Lactobacillus delbrueckii subsp. lactis R0187, Lactobacillus helveticus R0052, Lactobacillus rhamnosus R0011 and Bifidobacterium longum R0175 were examined for their ability to grow in combination with Streptococcus thermophilus cultures in milk and a laboratory soy beverage (LSB; both standardized to 4.5% protein and 2.3% fat). Strains R0011 and R0187 did not rapidly acidify the soy beverage despite good growth rates on soy carbohydrates. The S. thermophilus populations in the LSB were similar to that of milk even though milk had 30% more buffering capacity. In milk but not in soy, symbiosis with respect to acidification rate was observed between S. thermophilus and L. helveticus or B. longum. The populations of L. helveticus in the fermented products were similar in pure cultures or in the presence of the streptococci. However B. longum did not compete well in the mixed culture. Fermentation conditions varied as a function of the ability of S. thermophilus strains to acidify media to a pH of 4.65 (between 8 and 24 h). The probiotic populations in the mixed culture were influenced by the S. thermophilus strain and by the time of fermentation. Variations in growth rates of the bacteria did not appear to be linked to differences in initial redox or α-amino nitrogen levels. Strain selection enabled the preparation of a mixed starter, probiotic-fermented soy beverage containing 1.1 × 108 CFU/mL of L. helveticus R0052, which represented approximately 13% of the total final population.

Milk formulation (4% fat and 5% protein) prepared to simulate fresh cheese production was inoculated with: (1) 107 cfu mL−1 of fresh liquid starters of Lactococcus lactis ssp. lactis T1 and Lc. lactis ssp. cremoris T2, (2) a freeze-dried exopolysaccharide-producing (EPS) strain of Lactobacillus rhamnosus RW-9595M, and (3) freeze-dried Leuconostoc cremoris LM057 or Lc. lactis ssp. lactis var. diacetylactis MD089 strains. The effect of inoculation rate of the freeze-dried starters (between 106 and 107 cfu mL−1) and incubation temperature (between 23.5 and 36.5 °C) on evolution of pH and the various populations during fermentation was examined. Texture (apparent viscosity, syneresis potential) and chemical composition (diacetyl, acetaldehyde) of the fermented milks were also determined. Milk was incubated until a pH of 4.6 was obtained, which required between 6 and 10 h depending on temperature. In the range of inoculation levels used, there was no significant effect of the presence of lactobacilli, Ln. cremoris or Lc. lactis ssp. lactis var. diacetilactis on the growth of the lactococci. There was a direct correlation between the inoculation rates of the freeze-dried cultures and their final populations in the fermented milks. The growth of the cultures were also affected by temperature, Ln. cremoris growing less as incubation temperature increased, while the opposite was noted with Lb. rhamnosus. The apparent viscosity of the fermented milk was significantly affected by incubation temperature, but there was no correlation between apparent viscosity and the final population in lactobacilli. Of the three variables studied, the highest correlation with diacetyl content was obtained with the inoculation level of the Leuconostoc strain.

We present the Pad Chamber detector system in the PHENIX experiment at the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory. The three station system provides space points along each track in the spectrometer arms at mid-rapidity and covers a total area of 88 m(2). Its main functions are to provide the track coordinate along the beam and to ensure reliable pattern recognition at very high particle multiplicity. A new concept for two dimensional wire chamber readout via its finely segmented cathode was developed. The full readout system, comprising 172 800 electronic channels, is described together with the challenging design of the chambers. The electronics, mounted on the outer chamber face, together with the chamber itself amounts to 1.2% of a radiation length. Results from cosmic ray tests, showing an average efficiency better than 99.5% for all chambers are presented. The experiences from the full scale operation in the first run are reported. (C) 2002 Elsevier Science B.V. All rights reserved. (Less)

We present results for the charged-particle multiplicity distribution at midrapidity in Au-Au collisions at square root of [s(NN)] = 130 GeV measured with the PHENIX detector at RHIC. For the 5% most central collisions we find dN(ch)/d eta(vertical line eta = 0) = 622+/-1(stat)+/-41(syst). The results, analyzed as a function of centrality, show a steady rise of the particle density per participating nucleon with centrality.

The reaction cross section for the halo nucleus 6 He on hydrogen has been measured at 36 MeV/nucleon using the transmission method and a value of σ R =409±22 mb was obtained. A coherent analysis within a microscopic model of this result in conjunction with (p,p) and (p,n) angular distributions has allowed the interaction potential to be uniquely determined. This analysis also allowed the 6 He density distribution to be explored.

Mixed starters containing Lactococcus lactis, Leuconostoc cremoris and Lactobacillus rhamnosus strains were produced on commercial starter media (MB Complete, Thermolac, Marlac), as well as on milk. With the exception of Marlac, the starters were cultured under pH control. The effect of media and incubation temperature (22 or 32 degrees C) on population ratios, on specific acidifying activities (SAA) of the cultures as well as on their ability to produce aroma compounds in milk was studied. The starters had higher contents in lactobacilli when they were produced at 32 degrees C, whereas a tendency to obtain higher Leuconostoc populations was observed at 22 degrees C. With respect to the lactococci, there was a significant interaction between temperature and growth medium for both strains. Thus, Le. cremoris T2 reached higher populations at 32 degrees C if grown in MB complete and Thermolac, whereas in Marlac and skim milk, viable counts were higher at 22 degrees C. The lactococci represented 50% of the total population of the culture at the beginning of the incubation, but they composed between 80% and 99% of the total population following fermentation. The best medium for growth of Leuconostoc was milk, but populations of only 10(8) cfu/ml were reached. The lactobacilli did not grow well in MB Complete, and their development was best in the low-phosphate Marlac medium. The cultures grown on Marlac had the highest SAA values, whereas those grown on MB complete had the lowest. Overall, more ethanol and diacetyl were detected in the fermented milks when the starters used to inoculate them were produced at 22 degrees C.

A new concept for two-dimensional position readout of wire chambers is described. The basic idea is to use a cathode segmented into small pixels that are read out in specific groups (pads). The electronics is mounted on the outer face of the chamber with a chip-on-board technique, pushing the material thickness to a minimum. The system described here, containing 210 000 readout channels, will be used to read out the pad chambers in the PHENIX experiment at the Relativistic Heavy Ion Collider (RHIC).

Directed flow of deuterons, tritons, ${}^{3}\mathrm{He},$ and ${}^{4}\mathrm{He}$ is studied in Au+Au collisions at a beam momentum of $10.8A\mathrm{GeV}/c.$ Flow of all particles is analyzed as a function of transverse momentum for different centralities of the collision. The directed flow signal, ${v}_{1}{(p}_{t}),$ is found to increase with particle mass. This mass dependence is strongest in the projectile rapidity region.

In this article recent results of the E877 collaboration are presented. They include double differential multiplicities and rapidity densities of hadrons produced in Au+Au collisions at 11 AgeV/c, two-particle correlations of like and unlike particles, as well as some recent results on particle flow.

The physics emphases of the PHENIX collaboration and the design and current status of the PHENIX detector are discussed. The plan of the collaboration for making the most effective use of the available luminosity in the first years of RHIC operation is also presented., Comment: 5 pages, 1 figure. Further details of the PHENIX physics program available at http://www.rhic.bnl.gov/phenix/

The design and performance of the main time-of-flight hodoscope used in the E877 spectrometer at the BNL-AGS are presented. The hodoscope covers an area of 0.70×2.00 m 2 . It is made of 150 scintillator counters viewed by phototubes at each end. The detectors are mounted in an arc and arranged to eliminate gaps between the counters. An average time resolution of 85ps has been measured over the entire hodoscope.

Results are presented of an analysis of proton and charged pion azimuthal distributions measured with respect to the reaction plane in Au + Au collisions at a beam momentum of about 11A GeV/c. The azimuthal anisotropy is studied as a function of particle rapidity and transverse momentum for different centralities of the collisions. The triple differential (in rapidity, transverse momentum, and azimuthal angle) distributions are reconstructed. A comparison of the results with a previous analysis of charged-particle and transverse energy flow as well as with model predictions are presented. {copyright} {ital 1997} {ital The American Physical Society}

We compare measured collector current densities, cutoff frequencies (ft), and transducer gains for thermally shunted heterojunction bipolar transistors with 2–16 μm emitter dot diameters or 2–8 μm emitter bar widths with models of the emitter utilization factors. Models that do not take emitter resistance into account predict that the d.c. utilization factors are below 0.7 for collector current densities greater than 6 × 104 A cm−2 and emitter diameters or widths greater than 8 μm. However, because the current gains are compressed by the emitter resistances at those current densities, the measured utilization factors are close to 1, which agrees with models that include emitter resistance. A.c. utilization factors are evident in the transistor Y parameters. For example, Re|Y21z.sfnc drops off at high frequencies more steeply in HBTs with large emitter diameters or widths than in small ones. However, measured data shows that the HBT a.c. current gains h21 or ft values are not influenced by the a.c. utilization factor. A.c. utilization effects on HBT performance parameters such as small signal and power gains, output power, and power added efficiency are also examined.

The production of pions, protons and deuterons is studied at a laboratory angle of 144° in 28 Si+Pb collisions at 14.6 GeV/ c per nucleon. The centrality dependence of the pion yields is studied over the full impact parameter range using a zero degree calorimeter. The results are compared with the hadronic cascade model RQMD. These calculations are generally in agreement with the experimental results. According to these calculations, the pion yield in our acceptance is completely dominated by Δ-decay at freeze-out. Our measurements thus support the importance of baryon resonance production as one of the central features of relativistic heavy ion collisions at AGS energies. Although the strength of the pion spectrum is adequately described for kinetic energies above 50 MeV, an additional very soft component is observed in the pion spectra which is not predicted by RQMD. This very soft component accounts for a significant fraction of the total pion yield in this rapidity range but remains unexplained.

Experimental results and a detailed analysis are presented of the transverse energy and charged particle azimuthal distributions measured by the E877 Collaboration for different centralities of Au+Au collisions at a beam momentum of 10.8A GeV/c. The anisotropy of these distributions is studied with respect to the reaction plane reconstructed on an event-by-event basis using the transverse energy distribution measured by calorimeters. Results are corrected for the reaction plane resolution. For semicentral events we observe directed flow signals of up to 10{percent}. We observe a stronger anisotropy for slow charged particles. For both the charged particle and transverse energy distributions we observe a small but nonzero elliptic anisotropy with the major axis pointing into the reaction plane. Combining the information on transverse energy and charged particle flow we obtain information on the flow of nucleons and pions. The data are compared to event generators and the need to introduce a mean field or nucleon-nucleon potential is discussed. {copyright} {ital 1997} {ital The American Physical Society}

An investigation of MWPCs with interpolating chevron shaped cathode pad readout has been carried out as part of the R&D for the particle tracking system of the PHENIX detector at RHIC. Two prototype chambers were designed and constructed. Their response to minimum ionizing particles was tested with secondary beams from the AGS accelerator system at the Brookhaven National Laboratory. Results on resolution, differential non-linearity and overall performance for different chevron patterns and cell geometries are presented.

Effects of strong longitudinal colour electric fields (SCF), shadowing, and quenching on the open prompt charm mesons (D$^0$, D$^+$, D$^{*+}$, D${_s}{^+}$) production in central Pb + Pb collisions at $\sqrt{s_{\rm NN}}$ = 2.76 TeV are investigated within the framework of the {\small HIJING/B\=B v2.0} model. We compute the nuclear modification factor $R_{\rm PbPb}^{\rm D}$, and show that the above nuclear effects constitute important dynamical mechanisms in the description of experimental data. The strength of colour fields (as characterized by the string tension $\kappa$), partonic energy loss and jet quenching process lead to a suppression factor consistent with recent published data. Predictions for future beauty mesons measurements have been included. Ratios of strange to non-strange prompt charm mesons in central Pb + Pb and minimum bias (MB) $ p + p$ collisions at 2.76 TeV are also discussed. Minimum bias $p + p$ collisions which constitute theoretical baseline in our calculations are studied at the centre of mass energies $\sqrt{s}$ = 2.76 TeV and 7 TeV., Comment: 34 pages, 10 figures, revtex4

Two-particle correlation functions have been measured in Au+Au collisions at the AGS. The one-dimensional correlations are compared to the RQMD predictions. A multidimensional analysis of two-pion correlations allows to extract the average phase space density of pions at freeze-out and the pion source velocity.

A new room temperature wet chemical digital etching technique for GaAs is presented which uses hydrogen peroxide and an acid in a two‐step etching process to remove GaAs in approximately 15 A increments. In the first step, GaAs is oxidized by 30% hydrogen peroxide to form an oxide layer that is diffusion limited to a thickness of 14 to 17 A for time periods from 15 to 120 s. The second step removes this oxide layer with an acid that does not attack unoxidized GaAs. These steps are repeated in succession until the desired etch depth is obtained. Experimental results are presented for this digital etching technique demonstrating the etch rate and process invariability with respect to hydrogen peroxide and acid exposure times.

The elastic scattering p( 6 He, 6 He)p and charge exchange reaction p( 6 He, 6 Li)n have been measured in reverse kinematics with a secondary 6 He beam. The angular distributions for these reactions were obtained. In the case of the charge exchange reaction, the ratio of the cross section for the Gamow-Teller transition to the ground state, and for the Fermi transition to the isobaric analog state is a measure of the relative strength of the two components of the exchange interaction, V στ and V τ . This ratio is found to be compatible with existing systematics for stable T = 1 nuclei, and no clear signature of a halo structure was found in the present data.

The noise figure of the heterojunction bipolar transistor (HBT) in the microwave frequency range is studied, and an improved physical noise model is developed. Unlike the conventional high frequency noise model, which considers only the bias current dependence, the present model includes both the effects of voltage and current on the noise behavior. In addition, the frequency- and area-dependent natures of the HBT noise at very high frequencies are incorporated in the model. It is found that the voltage dependence of the high frequency noise in the HBT results from the self-heating effect, which gives rise to a higher HBT lattice temperature than the ambient temperature. Also, the free-carrier transport delay time must be considered to properly model the frequency dependence of noise since the inverse of this time is comparable with the frequency. Furthermore, the area dependence of noise is dominated by changes in the base resistance and emitter-base junction capacitance. Results for the minimum noise factor calculated from the model compare favorably with those obtained from measurements.

An investigation of the production of neutron-rich isotopes from the fragmentation of {sup 28}Si projectiles at {ital p}{sub lab}=14.6 GeV/{ital c} per nucleon was performed using the BNL-AGS-E814 spectrometer. We have measured the inclusive production cross sections of neutron-rich fragments ({sup 6}He, {sup 8}He, {sup 8}Li, {sup 9}Li, {sup 10}Be, {sup 11}Be, and {sup 13}B). We have also measured the transverse momentum distributions for {sup 6}He and {sup 9}Li, and the forward and transverse energy distributions associated with {sup 6}He production. The momentum distributions were analyzed in the context of the Goldhaber model. The question of whether the fragments are produced in the decay of the projectile following its electromagnetic excitation was also investigated.

A simple model is proposed to monitor the d.c. current gain long-term instability in the AlGaAs/GaAs heterojunction bipolar transistor (HBT). It is derived from the theory that the recombination current at the extrinsic base surface increases with time due to the surface degradation process. Furthermore, the initial 1 f noise and base leakage current characteristics have been used to provide the needed model parameters for the HBT surface recombination mechanism and surface quality, respectively. The current gain long-term variations calculated from the model for four HBTs compare favorably with those obtained from measurements. The model proposed is potentially useful to screen unreliable HBT lots without having to carry out the long-term stress test.

We have studied in detail the electromagnetic dissociation of [sup 28]Si projectiles at 14.6 GeV/([ital c] nucleon), interacting with Pb, Sn, Cu, and Al targets. Exclusive cross sections were measured for several decay channels, including final states involving the emission of protons, neutrons, and [alpha] particles. Excitation energy distributions for the 1[ital n]+[sup 27]Si and 2[ital p]+[sup 26]Mg decay channels were reconstructed with a resolution of 2 MeV, using a constrained kinematic fit. The energy distributions obtained for 1[ital n]+[sup 27]Si are in good agreement with the [sigma]([gamma],[ital n]) photoneutron cross sections multiplied by the virtual photon spectrum obtained in the Weizsaecker-Williams approximation. A search for the double photon excitation process, based on the dependence of the cross sections on the target atomic number, was performed.

We use the framework of the HIJING/BB v2.0 model to simulate high-multiplicity (HM) $p+p$ collision events at the Large Hadron Collider (LHC) to study observables sensitive to possible collective phenomena, such as strong longitudinal color fields (SLCF) modeled by an enhanced string tension ($\kappa$). We focus on the hyperon/meson yield ratios at center-of-mass (c.m.) energy $\sqrt{s}$ = 7 TeV, in the transverse momentum region, $1 < p_T < 4 $ GeV/{\it c}. For minimum bias events these ratios are well described assuming an energy dependence $\kappa = \kappa(s)= \kappa_{0} (s/s_{0})^{0.04} {\rm GeV/fm}$ ($\kappa_{0}$= 1 GeV/fm), giving a value $\kappa = 2$ GeV/fm at $\sqrt{s}$ = 7 TeV. We compare minimum bias (MB) events to simulated HM events assuming that $\kappa(MB)=2$ GeV/fm could grow to an extreme value of $\kappa(HM)=5$ GeV/fm that saturates the strangeness suppression factor. With this assumption the model predicts a very strong enhancement of (multi)strange baryon/meson ratios in HM events. If observed, such an enhancement could be also interpreted as a possible signature for formation in HM $p+p$ collision events of a deconfined but out of local thermal equilibrium {\em mini quark-gluon plasma} (mQGP).

Collinear factorized perturbative QCD model predictions are compared for $p+\mathrm{Pb}$ at 4.4$A$ TeV to test nuclear shadowing of parton distribution at the CERN Large Hadron Collider (LHC). The nuclear modification factor (NMF), ${R}_{p\mathrm{Pb}}(y=0,{p}_{T}l20\phantom{\rule{0.28em}{0ex}}\mathrm{GeV}/\mathit{c})=d{n}_{p\mathrm{Pb}}/[{N}_{\mathrm{coll}}(b)d{n}_{pp}]$, is computed with an electron-nucleus ($e+A$) global fit with different nuclear shadow distributions and compared to the fixed ${Q}^{2}$ shadow ansatz used in Monte Carlo Heavy Ion Jet Interacting Generator (HIJING)--type models. Because of the rapid Dokshitzer Gribov Lipatov Altarelli Parisi (DGLAP) reduction of shadowing with increasing ${Q}^{2}$ used in the $e+A$ global fit, our results confirm that no significant initial state suppression is expected [${R}_{p\mathrm{Pb}}({p}_{T})=1\ifmmode\pm\else\textpm\fi{}0.1$] in the ${p}_{T}$ range 5 to 20 GeV/$c$. In contrast, the fixed ${Q}^{2}$ shadowing models assumed in HIJING-type models predict in the range above ${p}_{T}$ a sizable suppression, ${R}_{p\mathrm{Pb}}({p}_{T})=0.6$--0.7, at midpseudorapidity that is similar to the color glass condensate (CGC) model predictions. For central (${N}_{\mathrm{coll}}=12$) $p+\mathrm{Pb}$ collisions and at forward pseudorapidity ($\ensuremath{\eta}=6$), the HIJING-type models predict smaller values of nuclear modification factors [${R}_{p\mathrm{Pb}}({p}_{T})$] than in minimum-bias events at midpseudorapidity ($\ensuremath{\eta}=0$). Observation of ${R}_{p\mathrm{Pb}}({p}_{T}=5\ensuremath{-}20\phantom{\rule{0.16em}{0ex}}\phantom{\rule{0.16em}{0ex}}\mathrm{GeV}/\mathit{c})\ensuremath{\lesssim}0.6$ for minimum bias $p+A$ collisions would pose a serious difficulty for separating initial-state from final-state interactions in Pb + Pb collisions at LHC energies.

The pea aphid Acyrthosiphon pisum has been established in North America for at least a century and occurs on a broad range of host plants. Despite its importance as a crop pest, there is little understanding of the genetic structure of its populations or the extent of genetic divergence associated with different host plant utilization. This study examined the extent of mitochondrial DNA (mtDNA) diversity among 35 clones of pea aphids from alfalfa. Polymorphisms were detected at only 2 of 126 restriction sites, suggesting the same impoverished level of genetic diversity found in prior allozyme studies. However, length variation was common and apparently arose as a result of tandem repeats in two regions of the mtDNA molecule. Region 1 occurred in proximity to the control region of the molecule, while region 2 was close to a cluster of tRNA genes flanking the NAD-dehydrogenase subunit 3 gene on the opposite side of the mtDNA molecule. Each of the aphid clones was homoplasmic for a single length variant in region 1, which varied with respect to the number of copies of a 120-bp repeat. By contrast, one-third of the clones were heteroplasmic at region 2, where they possessed a variable number of copies of a 210-bp repeat. Reanalysis of clones after 30 generations of parthenogenetic reproduction established the stability of length variants over this interval, suggesting their value in studies of the genetic structure of aphid populations.Key words: pea aphid, mitochondrial DNA, polymerase chain reaction, length heteroplasmy.

We have measured cross sections for the synthesis of nuclei of mass [ital A][le]4 in collisions of 14.6[ital A] GeV/[ital c] [sup 28]Si nuclei with targets of Pb, Cu, and Al. The data are measured at close to center-of-mass rapidities, and are unique in their exploration of the centrality dependence of nucleosynthesis. Simple coalescence models that were used to study nucleosynthesis at lower energies are inadequate for the description of our measurements. Our data and improved models are used to extract parameters related to the size of the interaction volume at freeze-out.

The two-pion correlation function has been measured for charged pions produced in central 14.6 A GeV/ c Si + Pb collisions at the AGS. Data for like-sign pions show a clear quantum interference effect as expected for identical bosons. The experimental correlation function agrees well with that obtained for events generated by a cascade code (RQMD). The present data are consistent with a time-averaged rms freeze-out radius of 8.3 fm and a mean duration of pion emission of 9 fm/ c . The system has expanded considerably before freeze-out.

We present the results of an analysis of two charged particle and transverse energy correlations in Si+Pb collisions at BNL AGS at 14.6 GeV/{ital c} per nucleon. The measured semi-inclusive normalized two particle pseudorapidity corrleation function exhibits short range correlations similar to the correlations observed in hadron-hadron and hadron-nucleus collisions at higher energies, although the observed correlations are smaller than the values scaled from {ital hp} and {ital hA} data. Estimates, provided by the observed correlations, of the intermittency indices as well as of the parameters of the cluster model are presented. Predictions using the FRITIOF event generator, which at this level of statistical accuracy show no pseudorapidity correlations, are not in agreement with our data. Azimuthal angle two particle correlations show nonzero back-to-back correlations in the central region (consistent with FRITIOF predictions) and are almost flat in the projectile fragmentation region. We also present results on the transverse energy azimuthal correlation function, which are similar to those from the two particle correlation function.

Inelastic scattering of 84 MeV/u 17 O projectiles has been used to excite the giant resonances (GR) in 232 Th. The deduced parameters (width, energy, EWSR) of the isoscalar giant quadrupole resonance are in agreement with the known systematics. The observed giant monopole resonance strength, 100% of the EWSR, is consistent with other recent experimental results using heavy-ion projectiles. Strength is also observed at high excitation energy. The fission probability of GR in 232 Th has been measured by detecting the fission fragments in coincidence with the inelastically scattered particles. A structure is observed in the fission coincidence spectrum around 10 MeV, which can be attributed to the fission decay of giant resonances. The measured fission probability is consistent with statistical decay of the GQR.

One of the main goals of the present heavy-ion reaction studies at the AGS and CERN is the understanding of the space-time evolution of the particle and energy density produced in such collisions. These are necessary ingredients if one wants to understand quantitatively the properties of matter at high temperature and density. In that respect, the study of inclusive global variables such as the transverse energy distribution gives valuable information on the reaction dynamics and, albeit indirectly, on the energy and baryon density reached in nucleus-nucleus collisions. In the spring of 1992, the AGS produced the first beam of very heavy ions, more specifically a beam of 11.4 GeV/c per nucleon {sup 197}Au. This is an important step for the field since it gives a first glimpse as to how the reaction dynamics evolves as the mass and volume of colliding systems reach the largest value that will be available in the future. The authors have used part of the E814 experimental set-up to study the transverse energy distribution produced in Au induced collisions. These data can be compared to similar data obtained with lighter beams and thus provide for the first time information on how the E{sub T} distributionmore » evolves with the mass of the system as one reaches very large systems.« less

In this article the authors summarize recent results from the E814 forward spectrometer on proton and pion distributions that give insight into the initial baryon (and energy) density achieved in central collisions as well as the temperature of the system at freeze-out. An independent measure for the latter, complementing the slope constants of particle spectra, is the population of nucleon excited states, in particular the {Delta}(1232) resonance. Besides its influence on the pion spectra it has also been identified directly in the experiment and first results are discussed. The first results from E814 on kaon spectra at low transverse momentum p{sub t} are presented; the spectra show an unexpected very steep rise at the lowest p{sub t}. The two pion correlation function has been studied for positive and negative pions and the authors show that it is consistent with a large source size at freeze-out. Finally, they show that the present data give a consistent picture of a system in thermal and chemical equilibrium at freeze-out.

With the HIJING/BBbar v2.0 heavy ion event generator, we explore the phenomenological consequences of several high parton density dynamical effects predicted in central Pb+Pb collisions at the Large Hadron Collider (LHC) energies. These include (1) jet quenching due to parton energy loss (dE/dx), (2) strangeness and hyperon enhancement due to strong longitudinal color field (SCF), and (3) enhancement of baryon-to-meson ratios due to baryon-anti-baryon junctions (JJbar) loops and SCF effects. The saturation/minijet cutoff scale p0(s)and effective string tension kappa(s,A) are constrained by our previous analysis of LHC p+p data and recent data on the charged multiplicity for Pb+Pb collisions reported by the ALICE collaboration. We predict the hadron flavor dependence (mesons and baryons) of the nuclear modification factor RAA(pT)$ and emphasize the possibility that the baryon anomaly could persist at the LHC up to pT=10 GeV, well beyond the range observed in central Au+Au collisions at RHIC energies., Comment: 25 pages, 8 figures, revtex4, text modifications, added references, accepted for publication Phys. Rev. C (2011)

We study the effect of strong longitudinal color fields (SCF) in $p$ + $p$ reactions up to Large Hadron Collider (LHC) energies in the framework of the hijing/B$\overline{\mathrm{B}}$ (v2.0) model that combines (collinear factorized) perturbative quantum chromodynamics multiple minijet production with soft longitudinal string excitation and hadronization. The default vacuum string tension, ${\ensuremath{\kappa}}_{0}$ = 1 GeV/fm, is replaced by an effective energy-dependent string tension, $\ensuremath{\kappa}(s)={\ensuremath{\kappa}}_{0}(s/{s}_{0}){}^{0.06}$ that increases monotonically with center-of-mass energy. The exponent $\ensuremath{\lambda}=0.06$ is found sufficient to reproduce well the energy dependence of multiparticle observables in the Relativistic Heavy Ion Collider, Tevatron, as well as recent LHC data. This exponent is half of that predicted by the color glass saturation (CGC) model, ${\ensuremath{\lambda}}_{\mathrm{CGC}}=0.115$, where gluon fusion multiparticle production mechanisms are assumed. In hijing/B$\overline{\mathrm{B}}$ (v2.0), the rapid growth of ${\mathit{dN}}_{\mathrm{ch}}/d\ensuremath{\eta}$ with energy is due to the interplay of copious minijet production with increasing SCF contributions. The large (strange) baryon-to-meson ratios measured at Tevatron energies are well described. A significant enhancement of these ratios is predicted up to the highest LHC energy (14 TeV). The effect of $\mathcal{J}\overline{\mathcal{J}}$ loops and SCF on baryon-antibaryon asymmetry, and its relation to baryon number transport, is also discussed.

We have measured distributions in transverse momentum and rapidity of protons from interactions of 14.6 GeV/nucleon28Si projectiles with targets of Al and Pb. The transverse momentum spectra exhibit a thermal shape with a rapidity dependent temperature parameter. For very central or violent collisions the proton rapidity distributions exhibit the large rapidity shifts and (for Si+Al) a peak at midrapidity as required for full stopping.

Recent results from the E814 collaboration are presented for reactions of 14.6 GeV/nucleon 28 Si projectiles with targets of Al, Cu, and Pb. This includes transverse energy distributions over the full solid angle and the distribution of charged particle multiplicity in the forward hemisphere. Furthermore we present recent results on transverse momentum spectra and rapidity distributions for protons and discuss them in terms of stopping and/or transparency. A fraction of nucleons emerges at beam rapidity, even for the most central collisions. These ‘punch-through’ distributions are shown to yield information on the in-medium nucleon-nucleon cross section. Finally, we discuss antiproton production at 0° as a function of event centrality to shed some light on possible reabsorption.

We have used the E814 apparatus to make a systematic study of antiproton production in collisions of 28 Si ions at 14.6 GeV/ c per nucleon with targets of Pb, Cu, and Al. We have measured the antiproton yield per interaction as a function of transverse energy and have found the yield to increase by a factor of ≈ 2 in going from the least to the most central collisions on the Pb target. A simple first-collision picture of antiproton production predicts the yield to increase by a factor of ≈ 11. We suggest that the discrepancy may result from the annihilation of antiprotons within the nuclear medium.

Transverse momentum distributions of light mass beam rapidity fragments 1 H, 3 He, and 4 He in reactions of 28 Si + Al , Cu and Pb are presented. The widths of the distributions are found to increase with increasing projectile-target overlap. This dependence is not consistent with the observed distributions being associated with the Fermi momentum of the nucleons in the projectile nucleus.

This study has examined the potential use of mitochondrial DNA (mtDNA) variation as a tool for identifying and managing stocks of walleye Stizostedion vitreum. Using 10 informative restriction endonucleases, we examined mtDNA variation in 847 walleyes from 68 populations across the species' range. Thirty-four mtDNA haplotypes were recognized, 21 of which were observed only in single fish. Eighty-nine percent of the walleyes sampled were members of one of three major haplotypes. These three haplotypes showed distinct geographic distributions: haplotype 1 (12% of all fish) predominated in the east, haplotype 4 (58%) in the central range, and haplotype 10 (19%) in the northwest. The other 10 haplotypes were locally distributed and were most useful for identifying stock and for detecting past transfers of fish. Walleyes from the Mississippi and Gulf Coast drainages possessed mtDNA haplotypes divergent from one another and absent from the core of the species' distribution. Widespread and often undocum...

We report a direct measurement of the final-state energy spectrum in the electromagnetic dissociation of {sup 28}Si into {ital p}+ {sup 27}Al at an energy of 14.6 GeV/nucleon. The final-state energy is obtained through a calculation of the {ital p}-{sup 27}Al invariant mass in kinematically reconstructed events. The final-state energy spectrum for all targets is peaked near the isovector giant-dipole resonance in {sup 28}Si and the dependence of the magnitude of the cross section on target charge confirms that the excitation is largely electromagnetic. By exploiting the expected scaling behavior on target {ital Z} and {ital A}, the background from nuclear interactions is evaluated and subtracted, leaving a pure electromagnetic dissociation final-state energy distribution. This distribution is well reproduced by simulated events, in which the photon spectrum calculated in the Weiszaecker-Williams approximation is combined with experimental data on the photonuclear reaction {sup 28}Si({gamma},{ital p}) {sup 27}Al, and slight differences are observed only at low final-state energy.

The production of neutral pions has been studied in the 16 O+ 27 Al, 58 Ni, 208 Pb reactions at 95 MeV/nucleon. Inclusive pion differential distributions d σ d p t , d σ d T π , and d σ d Ω have been measured by detecting the two-pion decay γ-rays in a setup of 8 lead glass Cherenkov detector telescopes. The data are discussed in the framework of a moving thermal source model. It is shown that the shape of the pion energy spectra is better described if mean field effects on the primary pion-production cross section and pion reabsorption are included in the calculation.

The Onychophora are a relic taxon which diverged early in the arthropod radiation and have shown little morphological differentiation for several hundred million years. Jamaica has the richest onychophoran fauna in the Caribbean and although only five species are known, they represent 7 per cent of the global fauna. The present study involved an analysis of allozyme and mtDNA diversity in Plicatoperipatus jamaicensis, an endemic species which is the commonest onychophoran on the island. The work showed that P. jamaicensis includes at least two different species. These taxa are largely allopatric, but co-occur at some sites without interbreeding. Allozyme and mtDNA analyses suggest their divergence in the early Pleistocene, following the Pliocene origin of the Plicatoperipatus lineage from a Macroperipatus ancestor. Allozyme variation in both species was unusually low, but sufficient to confirm that each taxon reproduces sexually. Mitochondrial DNA diversity was abundant in both species and indicated that local aggregations did not consist of kin groups. The mitochondrial genomes of both species were small enough to suggest that their organizations are unusual.