120789012
Backward emission of protons in Au+Au collisions at 11.7 A.GeV/c
We present preliminary results for the emission of target rapidity protons in minimum bias and central 11.7 A.GeV/c Au+Au collisions. The data span the pseudo-rapidity range {vert_bar}{eta}{vert_bar} {le} 0.76 and proton kinetic energy range of 50 {le} E {le} 200 MeV. The slopes of the kinetic energy spectra and dN/d{eta} values for central and minimum bias collisions are strikingly similar. Comparison of the results to results for Si+Au and p+A shows that the shape of the dN/d{eta} distribution is independent of the reaction system or centrality suggesting that the spectator matter does not play a decisive role in determining the shape of the proton distributions at back angles for these systems at AGS energies.
1289258
Energetic electrons associated with magnetic reconnection in the magnetic cloud boundary layer.
Here is reported in situ observation of energetic electrons (∼100-500 keV) associated with magnetic reconnection in the solar wind by the ACE and Wind spacecraft. The properties of this magnetic cloud driving reconnection and the associated energetic electron acceleration problem are discussed. Further analyses indicate that the electric field acceleration and Fermi-type mechanism are two fundamental elements in the electron acceleration processes and the trapping effect of the specific magnetic field configuration maintains the acceleration status that increases the totally gained energy.
10177650
Clarification of the three-body decay of 12C (12.71 MeV).
Using beta decays of a clean source of 12N produced at the IGISOL facility, we have measured the breakup of the 12C (12.71 MeV) state into three alpha particles with a segmented particle detector setup. The high quality of the data permits solving the question of the breakup mechanism of the 12.71 MeV state, a longstanding problem in few-body nuclear physics. Among existing models, a modified sequential model fits the data best, but systematic deviations indicate that a three-body description is needed.
120316681
Experimental results of the betatron sum resonance
The experimental observations of motion near the betatron sum resonance, /spl nusub x/+2/spl nusub z/=13, are presented. A fast quadrupole (Panofsky-style ferrite picture-frame magnet with 8 pulsed power supplies) producing a betatron tune shift of the order of 0.03 at rise time of 1 /spl mu/s was used. This quadrupole was used to produce betatron tunes which jumped past and then crossed back through a betatron sum resonance line. The beam response as function of initial betatron amplitudes were recorded turn by turn. The correlated growth of the action variables, J/sub x/ and J/sub z/, was observed. The phase space plots in the resonance frame reveal the features of particle motion near the nonlinear sum resonance region.<<ETX>>
22794424
Dipole and spin-dipole resonances in charge-exchange reactions on 12C.
The [sup 12]C([ital n],[ital p])[sup 12]B reaction was studied using the white neutron source at the Los Alamos Meson Physics Facility/Weapon Neutron Research Center with a continuous incident neutron energy from 60 to 260 MeV. Double differential cross sections were measured in the angular range 11[degree][le][theta][sub lab][le]37[degree]. Using the neutron time-of-flight facility at the Indiana University Cyclotron Facility, we also studied the [sup 12]C([ital p],[ital n])[sup 12]N reaction at [ital E][sub [ital p]]=186 MeV and the [sup 12]C([ital [rvec p]],[ital [rvec n]])[sup 12]N reaction at [ital E][sub [ital [rvec p]]]=160 and 186 MeV. Double differential cross sections were measured between [theta][sub lab]=0[degree] and [theta][sub lab]=50[degree] in 5[degree] steps. Spin observables [ital D][sub [ital N][ital N]], [ital A][sub [ital Y]], and [ital P] were measured at [theta][sub lab]=5[degree],9[degree],13[degree] with [ital E][sub [ital [rvec p]]]=160 MeV and [theta][sub lab]=15[degree],20[degree] with [ital E][sub [ital [rvec p]]]=186 MeV. Angular distributions of differential cross section and spin observables for low-lying transitions in the residual nuclei are compared with disorted-wave impulse approximation (DWIA) calculations. A multipole decomposition analysis was performed to study the giant dipole and giant spin-dipole resonances. The contributions of the quasifree reaction in the giant resonance region was subtracted. The empirical results ofmore » energy distributions for dipole ([Delta][ital L]=1) transition are compared with DWIA calculations using nuclear structure information obtained with a conventional shell model and also with a random phase approximation.« less
5742840
Crystallization in the Thin and Ultrathin Films of Poly(ethylene-vinyl acetate) and Linear Low-Density Polyethylene
The crystallization of poly(ethylene−vinyl acetate) and linear low-density polyethylene (LLDPE) films spun-cast from the polymer/toluene solutions with as-cast thickness from 460 to 10 nm was studied. The lamellar thickness was measured using small-angle X-ray scattering (SAXS) and found to increase from 14 to 21 nm for films thinner than 100 nm. The morphology of LLDPE measured by scanning probe microscopy (SPM) showed an edge-on lamellae for the films thicker than 30 nm and flat-on lamellae for the films thinner than 15 nm. A pseudo-“shish-kebab” tiny crystal structure was observed in between the larger lamellae. Crystallinity was confirmed using attenuated total reflectance−Fourier transformed infrared spectroscopy (ATR-FTIR) and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. The shear modulation force microscopy technique (SMFM) was used to measure the melting point, Tm, which was found to decrease for films thinner than 100 nm. The rate of decrease was a function of the annealing pr...
53371839
Transverse momentum resummation for color sextet and antitriplet scalar production at the LHC
We study the factorization and resummation of the transverse momentum spectrum of the color sextet and antitriplet scalars produced at the LHC based on soft-collinear effective theory. Compared to $$Z$$Z boson and Higgs production, a soft function is required to account for the soft gluon emission from the final-state colored scalar. The soft function is calculated at the next-to-leading order, and the resummation is performed at the approximate next-to-next-to-leading logarithmic accuracy. The non-perturbative effects and PDF uncertainties are also discussed.
119261131
Precision of future experiments measuring primordial tensor fluctuation
Recently the second phase of Background Imaging of Cosmic Extragalactic Polarization (BICEP2) claimed a detection of the tensor-to-scalar ratio (r) of primordial fluctuation at 5ρ confidence level. If it is true, this large and measurable amplitude (r ∼- 0.2) of B-mode polarization indicates that it is possible to measure the shape of CMB B-mode polarization with future experiments. Given the current understanding of the experimental noise and foreground contamination, we forecast the precision of r and the tensor spectral index nt measurements from Planck, Spider and POLARBEAR with nt as a free parameter. We quantitatively determine the signal-to-noise of the measurement in r-nt parameter space for the three experiments. The forecasted signal-to-noise ratio of the B-mode polarization somewhat depends on nt, but strongly depends on the true value of r.
18088710
Caustics, critical curves and cross-sections for gravitational lensing by disc galaxies
We study strong gravitational lensing by spiral galaxies, modeling them as infinitely thin uniform disks embedded in singular isothermal spheres. We derive general properties of the critical curves and caustics analytically. The multiple-image cross section is a sensitive function of the inclination angle of the disk relative to the observer. We compute the inclination averaged cross section for several sets of lensing parameters. For realistic disk mass and size parameters, we find that the cross section for multiple imaging is increased by only a modest factor and no dramatic increase in the optical depth for strong lensing of QSOs would be expected. However, the cross section for high magnifications is significantly increased due to the inclusion of a disk, especially for nearly edge-on configurations; due to the strong observational selection effects favoring high magnifications, there might be significant consequences for lensing statistics.
119221593
THE INFLUENCE OF NET QUARKS ON YIELDS AND RAPIDITY SPECTRA OF IDENTIFIED HADRONS
Within a quark combination model, we study systematically the yields and rapidity spectra of various hadrons in central Au + Au collisions at $\sqrt{s_{\rm NN}} = 200\ {\rm GeV}$. We find that considering the difference in rapidity between net quarks and newborn quarks, the data of multiplicities, rapidity distributions for π±, K±, $p(\bar{p})$ and, in particular, the ratios of charged antihadron to hadron as a function of rapidity, can be well described. The effects of net quarks on various hadrons are analyzed, and the rapidity distributions for $K^{0}_{s}$, $\Lambda(\bar{\Lambda})$, $\Sigma^{+}(\bar{\Sigma}{}^{-})$, $\Xi^{-}(\bar{\Xi}^{+})$ and $\Omega^{-}(\bar{\Omega}^{+})$ are predicted. We discuss the rapidity distribution of net baryons, and find that it reflects exactly the energy loss of colliding nuclei.
15577836
CENTRALITY, SYSTEM SIZE AND ENERGY DEPENDENCE OF CHARGED PARTICLE PSEUDORAPIDITY DISTRIBUTION
Utilizing the three-fireball picture within the quark combination model, we study systematically the charged particle pseudorapidity distributions in both Au + Au and Cu + Cu collision systems as a function of collision centrality and energy, , 62.4, 130 and 200 GeV, in the full pseudorapidity range. We find that: (i) the contribution from leading particles to dNch/dη distributions increases with the decrease of the collision centrality and energy respectively; (ii) the number of leading particles is almost independent of the collision energy, but it does depend on the nucleon participants Npart; (iii) if Cu + Cu and Au + Au collisions at the same collision energy are selected to have the same Npart, the resulting charged particle dN/dη distributions are nearly identical, in both the midrapidity particle density and the width of the distribution; this is true for both 62.4 GeV and 200 GeV data; (iv) the limiting fragmentation phenomenon is reproduced. We predict the total multiplicity and pseudorapidity distribution for the charged particles in Pb + Pb collisions at . Finally, we give a qualitative analysis of Nch/〈Npart/2〉 and dNch/dη/〈Npart/2〉|η≈0 as a function of and Npart from the RHIC to the LHC.