An Analysis of \pi\pi-Scattering Phase Shift and Existence of \sigma(555) particle

In most of the Nambu:Jona-Lasinio(NJL)-type models, realizing the hidden chiral symmetry, the existence of a scalar particle \sigma is needed with a mass m_\sigma=2 m_q, as a partner of the Nambu-Goldstone boson \pi. However, the results of many analyses on \pi\pi phase-shift thus far made have been negative for its existence. In this paper we re-analyze the phase-shift, applying a new method, the interfering amplitude method, which treats the T-matrix directly and describes multi-resonances in conformity with the unitarity. As a result, the existence of \sigma has been strongly suggested from the behavior of the \pi\pi-->\pi\pi phase shift between the \pi\pi- and the KK- thresholds, with mass = 553.3 +- 0.5_{st} MeV and width= 242.6 +- 1.2_{st} MeV. The most crucial point in our analysis is the introduction of a negative background phase, possibly reflecting a ``repulsive core" in \pi\pi interactions. The properties of f_0(980) are also investigated from data including those over the KK threshold. Its mass is obtained as 993.2 +- 6.5_{st} +- 6.9_{sys} MeV. Its width is about a hundred MeV, although this depends largely on the treatment of the elasticity and the \pi\pi-->KK phase shift, both of which may have large experimental uncertainties.Comment: 22 pages, Latex with Prog. Theor. Phys. format PTPTEX.sty, 4 EPS figure

pi^0 pi^0 Scattering Amplitudes and Phase Shifts Obtained by the pi^- P Charge Exchange Process

The results of the analysis of the pi^0 pi^0 scattering amplitudes obtained with pi^- P charge exchange reaction, pi^- P --> pi^0 pi^0 n, data at 9 GeV/c are presented. The pi^0 pi^0 scattering amplitudes show clear f_0(1370) and f_2(1270) signals in the S and D waves, respectively. The pi^0 pi^0 scattering phase shifts have been obtained below Kbar K threshold and been analyzed by the Interfering Amplitude method with introduction of negative background phases. The results show a S wave resonance, sigma. Its Breit-Wigner parameters are in good agreement with those of our previous analysis on the pi^+ pi^- phase shift data.Comment: 4 pages, 4 figures. Proceedings of the int. conf. Hadron'99 at Beijing, Aug. 1999. Presented for the collaboration of A.M.Ma, K.Takamatsu, M.Y.Ishida, S.Ishida, T.Ishida, T. Tsuru and H. Shimizu, and the E135 collaboration. For our activities on sigma, visit http://amaterasu.kek.jp/sigm

DETERMINATION OF BODY SEGMENT INERTIA PARAMETERS USING 3D HUMAN BODY SCANNER AND 3D CAD SOFTWARE

In the field of sports biomechanics, a human body is often treated as a linkage model to investigate various kinds of human movement. This modeling requires body segment inertia parameters (BSPs) such as masses, centers of mass, and moments of inertia. As the quality of motion capture system increases, more accurate BSPs are also needed to get accurate inverse dynamics results. Advanced technology has enabled us to obtain three-dimensional coordinates of the entire body surface. A 3D CAD software has also been able to be applied to measure the human body. It was hypothesized that BSPs with high accuracy could be determined by the combination of a 3D body scanner and a 3D CAD software. The purposes of this study are, first, to introduce a new method of measuring subject-specific BSPs and, second, to compare the BSPs from this study with those from an existing mathematical model in order to show that the proposed method can be used to produce more accurate BSPs

The Selective Serotonin Reuptake Inhibitor Paroxetine, but not Fluvoxamine, Decreases Methamphetamine Conditioned Place Preference in Mice

Monoamine transporters are the main targets of methamphetamine (METH). Recently, we showed that fluoxetine, a selective serotonin reuptake inhibitor (SSRI), decreased METH conditioned place preference (CPP), suggesting that serotonin transporter (SERT) inhibition reduces the rewarding effects of METH. To further test this hypothesis, in the present study we investigated the effects of additional SSRIs, paroxetine and fluvoxamine, on METH CPP in C57BL/6J mice. In the CPP test, pretreatment with 20 mg/kg paroxetine abolished the CPP for METH, whereas pretreatment with 100 mg/kg fluvoxamine prior to administration of METH failed to inhibit METH CPP. These results suggest that paroxetine, a medication widely used to treat depression, may be a useful tool for treating METH dependence. Further, these data suggest that molecules other than the SERT [such as G protein-activated inwardly rectifying K+ (GIRK) channels] whose activities are modulated by paroxetine and fluoxetine, but not by fluvoxamine, are involved in reducing METH CPP by paroxetine and fluoxetine

Enhanced Hyperthermia Induced by MDMA in Parkin Knockout Mice

MDMA (3,4-methylenedioxymethamphetamine) is reportedly severely toxic to both dopamine (DA) and serotonin neurons. MDMA significantly reduces the number of DA neurons in the substantia nigra, but not in the nucleus accumbens, indicating that MDMA causes selective destruction of DA neurons in the nigrostriatal pathway, sparing the mesolimbic pathway. Parkinson’s disease (PD) is a neurodegenerative disorder of multifactorial origin. The pathological hallmark of PD is the degeneration of DA neurons in the nigrostriatal pathway. Mutations in the parkin gene are frequently observed in autosomal recessive parkinsonism in humans. Parkin is hypothesized to protect against neurotoxic insult, and we attempted to clarify the role of parkin in MDMA-induced hyperthermia, one of the causal factors of neuronal damage, using parkin knockout mice. Body temperature was measured rectally before and 15, 30, 45, and 60 min after intraperitoneal injection of MDMA (30 mg/kg) at an ambient temperature of 22 ± 2°C. Significantly enhanced hyper-thermia after MDMA injection was observed in heterozygous and homozygous parkin knockout mice compared with wildtype mice, suggesting that parkin plays a protective role in MDMA neurotoxicity