Plasma Wakefield Acceleration with a Modulated Proton Bunch

The plasma wakefield amplitudes which could be achieved via the modulation of a long proton bunch are investigated. We find that in the limit of long bunches compared to the plasma wavelength, the strength of the accelerating fields is directly proportional to the number of particles in the drive bunch and inversely proportional to the square of the transverse bunch size. The scaling laws were tested and verified in detailed simulations using parameters of existing proton accelerators, and large electric fields were achieved, reaching 1 GV/m for LHC bunches. Energy gains for test electrons beyond 6 TeV were found in this case.Comment: 9 pages, 7 figure

The energy dependence of ptp_t angular correlations inferred from mean-ptp_{t} fluctuation scale dependence in heavy ion collisions at the SPS and RHIC

We present the first study of the energy dependence of $p_t$ angular correlations inferred from event-wise mean transverse momentum fluctuations in heavy ion collisions. We compare our large-acceptance measurements at CM energies $\sqrt{s_{NN}} =$ 19.6, 62.4, 130 and 200 GeV to SPS measurements at 12.3 and 17.3 GeV. $p_t$ angular correlation structure suggests that the principal source of $p_t$ correlations and fluctuations is minijets (minimum-bias parton fragments). We observe a dramatic increase in correlations and fluctuations from SPS to RHIC energies, increasing linearly with $\ln \sqrt{s_{NN}}$ from the onset of observable jet-related fluctuations near 10 GeV.Comment: 10 pages, 4 figure

Lingual kinematic strategies used to increase speech rate: Comparisons between younger and older adults

The primary objective of this study was to assess the lingual kinematic strategies used by younger and older adults to increase rate of speech. It was hypothesised that the strategies used by the older adults would differ from the young adults either as a direct result of, or in response to a need to compensate for, age-related changes in the tongue. Electromagnetic articulography was used to examine the tongue movements of eight young (M526.7 years) and eight older (M567.1 years) females during repetitions of /ta/ and /ka/ at a controlled moderate rate and then as fast as possible. The younger and older adults were found to significantly reduce consonant durations and increase syllable repetition rate by similar proportions. To achieve these reduced durations both groups appeared to use the same strategy, that of reducing the distances travelled by the tongue. Further comparisons at each rate, however, suggested a speed-accuracy trade-off and increased speech monitoring in the older adults. The results may assist in differentiating articulatory changes associated with normal aging from pathological changes found in disorders that affect the older population

Longitudinal Double-Spin Asymmetry and Cross Section for Inclusive Jet Production in Polarized Proton Collisions at √s = 200 GeV

We report a measurement of the longitudinal double-spin asymmetry ALL and the differential cross section for inclusive midrapidity jet production in polarized proton collisions at √s=200  GeV. The cross section data cover transverse momenta

Two-particle correlations on transverse momentum and momentum dissipation in Au-Au collisions at sqrt(sNN) = 130 GeV

Measurements of two-particle correlations on transverse momentum pt for Au–Au collisions at GeV are presented. Significant large-momentum-scale correlations are observed for charged primary hadrons with 0.15 ≤ pt ≤ 2 GeV/c and pseudorapidity |η| ≤ 1.3. Such correlations were not observed in a similar study at lower energy and are not predicted by theoretical collision models. Their direct relation to mean-pt fluctuations measured in the same angular acceptance is demonstrated. Positive correlations are observed for pairs of particles which have large pt values while negative correlations occur for pairs in which one particle has large pt and the other has much lower pt. The correlation amplitudes per final state particle increase with collision centrality. The observed correlations are consistent with a scenario in which the transverse momentum of hadrons associated with initial-stage semi-hard parton scattering is dissipated by the medium to lower pt

The energy dependence of p\u3csub\u3et\u3c/sub\u3e angular correlations inferred from mean-p\u3csub\u3et\u3c/sub\u3e fluctuation scale dependence in heavy ion collisions at the SPS and RHIC

We present the first study of the energy dependence of pt angular correlations inferred from event-wise mean transverse momentum pt fluctuations in heavy ion collisions. We compare our large-acceptance measurements at CM energies , 62.4, 130 and 200 GeV to SPS measurements at 12.3 and 17.3 GeV. pt angular correlation structure suggests that the principal source of pt correlations and fluctuations is minijets (minimum-bias parton fragments). We observe a dramatic increase in correlations and fluctuations from SPS to RHIC energies, increasing linearly with from the onset of observable jet-related pt fluctuations near 10 GeV

Scaling Properties of Hyperon Production in Au + Au Collisions at √sNN = 200 GeV

We present the scaling properties of Λ, Ξ, and Ω in midrapidity Au+Au collisions at the Brookhaven National Laboratory Relativistic Heavy Ion Collider at sNN−−−−√=200  GeV. The yield of multistrange baryons per participant nucleon increases from peripheral to central collisions more rapidly than that of Λ, indicating an increase of the strange-quark density of the matter produced. The strange phase-space occupancy factor γs approaches unity for the most central collisions. Moreover, the nuclear modification factors of p, Λ, and Ξ are consistent with each other for

Direct Observation of Dijets in Central Au+Au Collisions at √sNN=200 GeV

The STAR Collaboration at the Relativistic Heavy Ion Collider reports measurements of azimuthal correlations of high transverse momentum (pT) charged hadrons in Au+Au collisions at higher pT than reported previously. As pT is increased, a narrow, back-to-back peak emerges above the decreasing background, providing a clear dijet signal for all collision centralities studied. Using these correlations, we perform a systematic study of dijet production and suppression in nuclear collisions, providing new constraints on the mechanisms underlying partonic energy loss in dense matter