Kazuya Aoki

System size and energy dependence of jet-induced hadron pair correlation shapes in Cu+Cu and Au+Au collisions at sNN=200 and 62.4 GeV

We present azimuthal angle correlations of intermediate transverse momentum (1-4 GeV/c) hadrons from dijets in Cu+Cu and Au+Au collisions at square root sNN=62.4 and 200 GeV. The away-side dijet induced azimuthal correlation is broadened, non-Gaussian, and peaked away from Delta phi=pi in central and semicentral collisions in all the systems. The broadening and peak location are found to depend upon the number of participants in the collision, but not on the collision energy or beam nuclei. These results are consistent with sound or shock wave models, but pose challenges to Cherenkov gluon radiation models.

Transverse momentum dependence of η meson suppression in Au+Au collisions at √sNN=200 GeV

New measurements by the PHENIX experiment at the Relativistic Heavy Ion Collider for eta production at midrapidity as a function of transverse momentum (p{sub T}) and collision centrality in sq root(s{sub NN})=200 GeV Au+Au and p+p collisions are presented. They indicate nuclear modification factors (R{sub AA}) which are similar in both magnitude and trend to those found in earlier pi{sup 0} measurements. Linear fits to R{sub AA} as a function of p{sub T} in 5-20 GeV/c show that the slope is consistent with zero within two standard deviations at all centralities, although a slow rise cannot be excluded. Having different statistical and systematic uncertainties, the pi{sup 0} and eta measurements are complementary at high p{sub T}; thus, along with the extended p{sub T} range of these data they can provide additional constraints for theoretical modeling and the extraction of transport properties.

Double Helicity Asymmetry of Inclusive π0 Production in Polarized pp Collisions at s = 62.4 GeV

The proton spin structure is not understood yet and there has remained large uncertainty on Δg, the gluon spin contribution to the proton. Double helicity asymmetry (ALL) of π0 production in polarized pp collisions is used to constrain Δg. In this report, preliminary results of ALL of π0 in pp collisions at su2009=u200962.4u2009GeV measured by PHENIX experiment in 2006 is presented. It can probe higer x region than the previously reported π0ALL at su2009=u2009200u2009GeV thanks to the lower center of mass energy.

A PAVEMENT DETERIORATON FORCASTING MODEL WITH REFERENCE TO SAMPLE DROPPING

本研究では，経年的に蓄積された舗装の路面性状データや補修履歴データを用いて，舗装の劣化過程を統計的に予測する舗装劣化予測モデルを提案する．具体的には，道路舗装の劣化状態を離散的な複数のレーティングで記述し，一定期間内における舗装状態のマルコフ推移確率を多段階指数ハザードモデルを用いて表現する．その際，劣化が進行した舗装に対して補修が実施されるため観測データが欠損するという問題が発生する．本研究では，選択肢サンプリング法を用いてサンプル欠損バイアスを考慮した最尤推定法を提案し，多段階指数ハザードモデルの推計に適用する．さらに，マルコフ推移確率を，高速道路のわだち掘れ量のデータベースに基づいて推定し，サンプル欠損バイアスの影響について実証的に検討する．