Solution of Orthopositronium lifetime Puzzle

The intrinsic decay rate of orthopositronium formed in ${\rm SiO_2}$ powder is measured using the direct $2\gamma$ correction method such that the time dependence of the pick-off annihilation rate is precisely determined. The decay rate of orthopositronium is found to be $7.0396\pm0.0012 (stat.)\pm0.0011 (sys.)\mu s^{-1}$, which is consistent with our previous measurements with about twice the accuracy. Results agree well with the $O(\alpha^2)$ QED prediction, and also with a result reported very recently using nanoporous film

Longitudinal spin transfer of Lambda and anti-Lambda in polarized pp collisions at \sqrt s=200 GeV at STAR

We report our measurement on longitudinal spin transfer, D_LL, from high energy polarized protons to $\Lambda$ and $\bar{\Lambda}$ hyperons in proton-proton collisions at $\sqrt{s} = 200 GeV$ with the STAR detector at RHIC. The current measurements cover $\Lambda$, $\bar\Lambda$ pseudorapidity $|\eta| < 1.2$ and transverse momenta $p_T$ up to $4GeV/c$ using the data taken in 2005. The longitudinal spin transfer is found to be D_LL= -0.03\pm 0.13 (stat) \pm 0.04(syst)$for inclusive$\Lambda$and$D_{LL} = -0.12 \pm 0.08(stat) \pm 0.03(syst)$for inclusive$\bar{\Lambda}$hyperons with$ = 0.5$and$ = 3.7 GeV/c$. The prospects with 2009 data and the future measurements are also given.Comment: 6 pages, 3 figures, presentation at the SPIN2010 International Symposium, Juelich (Germany), Sep. 27-Oct. 2, 201

Measurement of the analyzing power of proton-carbon elastic scattering in the CNI region at RHIC

The single transverse spin asymmetry, A_N, of the p-carbon elastic scattering process in the Coulomb Nuclear Interference (CNI) region was measured using an ultra thin carbon target and polarized proton beam in the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory (BNL). In 2004, data were collected to calibrate the p-carbon process at two RHIC energies (24 GeV, 100 GeV). A_N was obtained as a function of momentum transfer -t. The results were fit with theoretical models which allow us to assess the contribution from a hadronic spin flip amplitude.Comment: Contribution to the proceedings of the 16th International Spin Physics Symposium, spin2004 (Trieste

Results From The RHIC PC CNI Polarimeter for 2003

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Precise measurement of positronium hyperfine splitting using the Zeeman effect

Positronium is an ideal system for the research of the quantum electrodynamics (QED) in bound state. The hyperfine splitting (HFS) of positronium, $\Delta_{\mathrm{HFS}}$, gives a good test of the bound state calculations and probes new physics beyond the Standard Model. A new method of QED calculations has revealed the discrepancy by 15\,ppm (3.9$\sigma$) of $\Delta_{\mathrm{HFS}}$ between the QED prediction and the experimental average. There would be possibility of new physics or common systematic uncertainties in the previous all experiments. We describe a new experiment to reduce possible systematic uncertainties and will provide an independent check of the discrepancy. We are now taking data and the current result of $\Delta_{\mathrm{HFS}} = 203.395\,1 \pm 0.002\,4 (\mathrm{stat.}, 12\,\mathrm{ppm}) \pm 0.001\,9 (\mathrm{sys.}, 9.5\,\mathrm{ppm})\,\mathrm{GHz}$ has been obtained so far. A measurement with a precision of $O$(ppm) is expected within a year.Comment: 8 pages, 8 figures, 2 tables, proceeding of LEAP2011, accepted by Hyperfine Interaction

SUSY physics with early data Understanding ATLAS detector and backgrounds

With the imminent start of the ATLAS data taking in 2007, the well considered strategy is necessary for the good understanding of the detector performance from in situ calibration and the realistic estimation of the Standard Model background. These are urgent issue for the new physics discovery channels especially for the SUSY searches in the early data taking of LHC run. The talk starts with the breif overview of the ATLAS detector and the calibration commissioning, then the realistic background estimation using real data and the matrix element calculation continues. Finally the newly obtained SUSY discovery potential with newly estimated backgrounds is presented

High-pT pi^zero Production with Respect to the Reaction Plane in Au + Au Collisions at sqrt(s_NN) = 200 GeV

Measurements of the azimuthal anisotropy of high-\pT neutral pion neutral pion production in Au+Au collisions at sqrt(s_NN) = 200 GeV by the PHENIX experiment are presented. The data included in this paper were collected during the 2004 RHIC running period and represent approximately an order of magnitude increase in the number of analyzed events relative to previously published results. Azimuthal angle distributions of pi^0s detected in the PHENIX electromagnetic calorimeters are measured relative to the reaction plane determined event-by-event using the forward and backward beam-beam counters. Amplitudes of the second Fourier component (v_2) of the angular distributions are presented as a function of pi^0 transverse momentum p_T for different bins in collision centrality. Measured reaction plane dependent pi^0 yields are used to determine the azimuthal dependence of the pi^0 suppression as a function of p_T, R_AA (Delta phi,p_T). A jet-quenching motivated geometric analysis is presented that attempts to simultaneously describe the centrality dependence and reaction plane angle dependence of the pi^0 suppression in terms of the path lengths of hypothetical parent partons in the medium. This set of results allows for a detailed examination of the influence of geometry in the collision region, and of the interplay between collective flow and jet-quenching effects along the azimuthal axis.Comment: 344 authors, 35 pages text, RevTeX-4, 24 figures, 8 tables. Submitted to Physical Review