Measurements of Transverse Spin Effects with the Forward Pion Detector of STAR

Measurements by the STAR collaboration of neutral pion production at large Feynman x (x_F) in the first polarized proton collisions at $\sqrt{s}=200$ GeV were reported previously. Cross sections measured at $\eta=3.3$, 3.8 and 4.0 are found to be consistent with next-to-leading order perturbative QCD calculations. The analyzing power is consistent with zero at negative x_F and at positive x_F up to ~0.3, then grows more positive with increasing x_F. This behavior can be described by phenomenological models including the Sivers effect, the Collins effect or higher twist contributions in the initial and final states. Forward calorimetry at STAR has been extended, and there are plans for further expansion. An integrated luminosity of 6.8 pb^${-1}$ with average beam polarization of 60% from online polarimetry measurements was sampled with the upgraded FPD in the 2006 RHIC run. This data sample will allow for a detailed map of the \pi^0 analyzing power over kinematic variables bounded by 0.3 < x_F < 0.6 and 1.2 < p_T < 5.0 GeV/c at $\sqrt{s}=200$ GeV. The expanded FPD has observed multi-photon final states expected to have "jet-like" characteristics. The transverse spin dependence of jet-like events can discriminate between the Collins and Sivers effects and lead to further progress in understanding the origin of single spin asymmetries in forward particle production. Data were also obtained at $\sqrt{s}=62.4$ GeV for x_F -> 1 to test predictions based on phenomenological fits to earlier STAR results. Recent results, the status of the analysis of 2006 run data and near-term plans will be discussed.Comment: 4 pages, 3 figures, to be published in the proceedings of the 17th International Spin Physics Symposium (SPIN2006), October 2-7, 2006, Kyoto, Japa

Recent results from the STAR spin program at RHIC

The STAR experiment uses polarized p+p collisions at RHIC to determine the contributions to the spin of the proton from gluon spin and from orbital angular momentum of the quarks and gluons. Selective STAR measurements of the longitudinal double spin asymmetry for inclusive jet and inclusive hadron production are presented here. In addition, we report measurements of the transverse spin asymmetry for di-jet production at mid-rapidity and the transverse single-spin asymmetry for forward pi0 productionComment: 4 pages, 5 figures, presented at GHP06 conferenc

Development of a Momentum Determined Electron Beam in the 1 -45 GeV Range

A beam line for electrons with energies in the range of 1 to 45 GeV, low contamination of hadrons and muons and high intensity up to 10^6 per accelerator spill at 27 GeV was setup at U70 accelerator in Protvino, Russia. A beam tagging system based on drift chambers with 160 micron resolution was able to measure relative electron beam momentum precisely. The resolution sigma_p p was 0.13% at 45 GeV where multiple scattering is negligible. This test beam setup provided the possibility to study properties of lead tungstate crystals (PbWO_4) for the BTeV experiment at Fermilab.Comment: 12 pages, 8 figures; work done by the BTeV Electromagnetic Calorimeter grou

Comparison of Radiation Damage in Lead Tungstate Crystals under Pion and Gamma Irradiation

Studies of the radiation hardness of lead tungstate crystals produced by the Bogoroditsk Techno-Chemical Plant in Russia and the Shanghai Institute of Ceramics in China have been carried out at IHEP, Protvino. The crystals were irradiated by a 40-GeV pion beam. After full recovery, the same crystals were irradiated using a $^{137}Cs$ $\gamma$-ray source. The dose rate profiles along the crystal length were observed to be quite similar. We compare the effects of the two types of radiation on the crystals light output.Comment: 10 pages, 8 figures, Latex 2e, 28.04.04 - minor grammatical change

Correlation of Beam Electron and LED Signal Losses under Irradiation and Long-term Recovery of Lead Tungstate Crystals

Radiation damage in lead tungstate crystals reduces their transparency. The calibration that relates the amount of light detected in such crystals to incident energy of photons or electrons is of paramount importance to maintaining the energy resolution the detection system. We report on tests of lead tungstate crystals, read out by photomultiplier tubes, exposed to irradiation by monoenergetic electron or pion beams. The beam electrons themselves were used to measure the scintillation light output, and a blue light emitting diode (LED) was used to track variations of crystals transparency. We report on the correlation of the LED measurement with radiation damage by the beams and also show that it can accurately monitor the crystals recovery from such damage.Comment: 9 pages, 6 figures, LaTeX2