Phenomenology of single spin asymmetries in p(transv. polarized)-p -> pion + X

A phenomenological description of single transverse spin effects in hadron-hadron inclusive processes is proposed, assuming a generalized factorization scheme and pQCD hard interactions. The transverse momentum, k_T, of the quarks inside the hadrons and of the hadrons relatively to the fragmenting quark, is taken into account in distribution and fragmentation functions, and leads to possible non zero single spin asymmetries. The role of k_T and spin dependent quark fragmentations -- the so-called Collins effect -- is investigated in details in p(transv. polarized)-p -> pion + X processes: it is shown how the experimental data could be described, obtaining an explicit expression for the spin asymmetry of a polarized fragmenting quark, on which some comments are made. Predictions for other processes, possible further applications and experimental tests are discussed.Comment: 20+1 pages, LaTeX, 6 eps figures, uses epsfig.sty. Version v2: Some sentences rephrased and comments added throughout the paper; one reference added; no changes in results and figures. Final version to be published in Phys. Rev.

Accessing Transversity in Double-Spin Asymmetries at the BNL-RHIC

We give upper bounds for transverse double-spin asymmetries in polarized proton-proton collisions by saturating the positivity constraint for the transversity densities at a low hadronic resolution scale. We consider prompt photon, jet, pion, and heavy flavor production at the BNL Relativistic Heavy Ion Collider (RHIC). Estimates of the expected statistical accuracy for such measurements are presented, taking into account the acceptance of the RHIC detectors.Comment: 15 pages, LaTeX, 2 figures as eps file

Double transverse spin asymmetries in vector boson production

We investigate a helicity non-flip double transverse spin asymmetry in vector boson production in hadron-hadron scattering, which was first considered by Ralston and Soper at the tree level. It does not involve transversity functions and in principle also arises in W-boson production for which we present the expressions. The asymmetry requires observing the transverse momentum of the vector boson, but it is not suppressed by explicit inverse powers of a large energy scale. However, as we will show, inclusion of Sudakov factors causes suppression of the asymmetry, which increases with energy. Moreover, the asymmetry is shown to be approximately proportional to x_1 g_1(x_1) x_2 \bar g_1(x_2), which gives rise to additional suppression at small values of the light cone momentum fractions. This implies that it is negligible for Z or W production and is mainly of interest for \gamma^* at low energies. We also compare the asymmetry with other types of double transverse spin asymmetries and discuss how to disentangle them.Comment: 12 pages, Revtex, 2 Postscript figures, uses aps.sty, epsf.sty; figures replaced, a few minor other correction

Updated Report Acceleration of Polarized Protons to 120-150 GeV/c at Fermilab

The SPIN@FERMI collaboration has updated its 1991-95 Reports on the acceleration of polarized protons in Fermilab's Main Injector, which was commissioned by Fermilab. This Updated Report summarizes some updated Physics Goals for a 120-150 GeV/c polarized proton beam. It also contains an updated discussion of the Modifications and Hardware needed for a polarized beam in the Main Injector, along with an updated Schedule and Budget.Comment: 30 pages, 12 figure

A mechanism for the T-odd pion fragmentation function

We consider a simple rescattering mechanism to calculate a leading twist $T$-odd pion fragmentation function, a favored candidate for filtering the transversity properties of the nucleon. We evaluate the single spin azimuthal asymmetry for a transversely polarized target in semi-inclusive deep inelastic scattering (for HERMES kinematics). Additionally, we calculate the double $T$-odd $\cos2\phi$ asymmetry in this framework.Comment: 6 pages revtex, 7 eps figures, references added and updated in this published versio

Development of Nondestructive Evaluation Methods and Prediction of Effects of Flaws on the Fracture Behavior of Structural Ceramics

Work emphasized continuous-fiber ceramic matrix composites (CFCCs) with 2-D lay-ups composed of chemical-vapor-infiltrated (CVI) SiC/SiC materials, mostly made of Nicalon plain weave with 16 {times} 16 tows/in. One sample examined comprised a 3-D SiC/SiC braid made by Techniweave. Using a new 1024{times}1024{times}14 bit detector, images from 3-D X-ray CT data with pixel sizes of <140 {mu}m and 2-D fast-Fourier transform (FFT) image processing, we have shown that fiber orientations can be measured to {plus_minus}2-1/2{degree}. 3-D FFT analysis was used to determine 3-D braid/weave fiber spacing. Multinuclear ({sup l}H, {sup 13}C, and {sup 29}Si) NMR spectroscopy, is being studied. Surface chemistry of fibers and chemistry of interfacial regions in composites are being studied. We are also conducting initial studies to investigate the bulk composition of matrix materials ({alpha}, {beta}, amorphous phase, silica, and oxynitride concentration) and surface chemistry of Si{sub 3}N{sub 4} and SiC fibers. Fracture mechanics work to correlate with NDE data focused on strength distribution of as-fabricated Nicalon fibers obtained from bundle tests. Strength distribution of fractured Nicalon fibers in composites was assessed from fracture mirror radii. SEM was used to determine distribution of fiber pullout length distribution for fibers in composites, for their strength distribution. From the strength distribution plots, scale parameters were determined to be 3.45 GPa for as-fabricated fibers and 1.31 GPa for fibers in processed composites. However, the Weibull moduli for the two distributions were similar. Reduction in strength of the fibers in processed composites is believed to be due to surface flaws and defects. Effects of fiber misorientation on mechanical properties of NDE-tested CVI continuous-fiber composites are currently being investigated. 8 figs, 11 refs

Spin-flipping a stored polarized proton beam with an rf dipole

Frequent polarization reversals, or spin-flips, of a stored polarized high-energy beam may greatly reduce systematic errors of spin asymmetry measurements in a scattering asymmetry experiment. We studied the spin-flipping of a 120 MeV horizontally-polarized proton beam stored in the IUCF Cooler Ring by ramping an rf-dipole magnet’s frequency through an rf-induced depolarizing resonance in the presence of a nearly-full Siberian snake. After optimizing the frequency ramp parameters, we used multiple spin-flips to measure a spin-flip efficiency of 86.5±0.5%.86.5±0.5%. The spin-flip efficiency was apparently limited by the rf-dipole’s field strength. This result indicates that an efficient spin-flipping a stored polarized beam should be possible in high energy rings such as RHIC and HERA where Siberian snakes are certainly needed and only dipole rf-flipper-magnets are practical. © 2000 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87561/2/662_1.pd

Effects of Parton Intrinsic Transverse Momentum on Photon Production in Hard-Scattering Processes

We calculate the photon production cross section arising from the hard scattering of partons in nucleon-nucleon collisions by taking into account the intrinsic parton transverse momentum distribution and the next-to-leading-order contributions. As first pointed out by Owens, the inclusion of the intrinsic transverse momentum distribution of partons leads to an enhancement of photon production cross section in the region of photon transverse momenta of a few GeV/c for nucleon-nucleon collisions at a center-of-mass energy of a few tens of GeV. The enhancement increases as $\sqrt{s}$ decreases. Such an enhancement is an important consideration in the region of photon momenta under investigation in high-energy heavy-ion collisions.Comment: 10 pages, 9 figures, in LaTex, revised to include ananlytic evaluation of the hard-scattering integra