A high-pressure hydrogen time projection chamber for the MuCap experiment

The MuCap experiment at the Paul Scherrer Institute performed a high-precision measurement of the rate of the basic electroweak process of nuclear muon capture by the proton, $\mu^- + p \rightarrow n + \nu_\mu$. The experimental approach was based on the use of a time projection chamber (TPC) that operated in pure hydrogen gas at a pressure of 10 bar and functioned as an active muon stopping target. The TPC detected the tracks of individual muon arrivals in three dimensions, while the trajectories of outgoing decay (Michel) electrons were measured by two surrounding wire chambers and a plastic scintillation hodoscope. The muon and electron detectors together enabled a precise measurement of the $\mu p$ atom's lifetime, from which the nuclear muon capture rate was deduced. The TPC was also used to monitor the purity of the hydrogen gas by detecting the nuclear recoils that follow muon capture by elemental impurities. This paper describes the TPC design and performance in detail.Comment: 15 pages, 13 figures, to be submitted to Eur. Phys. J. A; clarified section 3.1.2 and made minor stylistic corrections for Eur. Phys. J. A requirement

Measurement of the Rate of Muon Capture in Hydrogen Gas and Determination of the Proton's Pseudoscalar Coupling gPg_P

The rate of nuclear muon capture by the proton has been measured using a new experimental technique based on a time projection chamber operating in ultra-clean, deuterium-depleted hydrogen gas at 1 MPa pressure. The capture rate was obtained from the difference between the measured $\mu^-$ disappearance rate in hydrogen and the world average for the $\mu^+$ decay rate. The target's low gas density of 1% compared to liquid hydrogen is key to avoiding uncertainties that arise from the formation of muonic molecules. The capture rate from the hyperfine singlet ground state of the $\mu p$ atom is measured to be $\Lambda_S=725.0 \pm 17.4 s^{-1}$, from which the induced pseudoscalar coupling of the nucleon, $g_P(q^2=-0.88 m_\mu^2)=7.3 \pm 1.1$, is extracted. This result is consistent with theoretical predictions for $g_P$ that are based on the approximate chiral symmetry of QCD.Comment: submitted to Phys.Rev.Let

Measurement of Muon Capture on the Proton to 1% Precision and Determination of the Pseudoscalar Coupling g_P

The MuCap experiment at the Paul Scherrer Institute has measured the rate L_S of muon capture from the singlet state of the muonic hydrogen atom to a precision of 1%. A muon beam was stopped in a time projection chamber filled with 10-bar, ultra-pure hydrogen gas. Cylindrical wire chambers and a segmented scintillator barrel detected electrons from muon decay. L_S is determined from the difference between the mu- disappearance rate in hydrogen and the free muon decay rate. The result is based on the analysis of 1.2 10^10 mu- decays, from which we extract the capture rate L_S = (714.9 +- 5.4(stat) +- 5.1(syst)) s^-1 and derive the proton's pseudoscalar coupling g_P(q^2_0 = -0.88 m^2_mu) = 8.06 +- 0.55.Comment: Updated figure 1 and small changes in wording to match published versio

Influence of total low dose fractionated radiation on growth and metastasis of mice Lewis lung carcinoma

Effects of prolonged fractionated ionized radiation in low doses on the growth and metastasis intensity of mice Lewis lung carcinoma (LLC) are studied. On the background of tumor growth, stimulation induced by irradiation in the selected mode of dose fractionation inhibition of spontaneous dissemination of tumor cells into lungs is observed. On the 23-rd day after cell inoculation metastases incidence in irradiated animals was 25 % lower; the number and size of lung metastases decreased by 1.6 and 1.7 times. In the remote terms of tumor growth inhibition of functional activity of macrophages – central effectors of non-specific anti-tumor immunity was revealed

Dynamics of free-radical processes in the animals after protracted influence of exogenous nitric oxide and ionizing radiation

Aim of the investigation was to study the influence of nitric oxide (NO) and low doses of ionizing radiation (LDIR) on free radical processes that occur in various tissues of mammalian organism. Fractionated LDIR irradia-tion was shown to temporarily disrupt an oxidative metabolism. At same time protracted NO inhalation causes more significant harmful effects. This indicated that there are two pathways of oxidative metabolism disruption caused by generation of reactive oxygen or nitrogen species in tissues of mammalian organism

Modification of oxidation metabolism by biological active preparation RAPAMID in mice with different radiosensitivity

Influence of Rapamid, new biological active preparation of natural origin with antioxidant properties, on oxidation metabolism in mice with different radiosensitivity under single total irradiated, doze 1.0 Gy, was investigated. The one usage course of Rapamid before irradiation, according to oxide metabolism values, exert considerable radioprotective efficacy upon radiosensitive C3H mice, whereas on radioresistant mice (line CBA) such course result in increasing of free radicals processes. The authors pay attention to necessity of individual approach when drugs with antioxidant properties are used

Effect of mineral water of Beryezovsky deposit on hematopoietic system of the irradiated animals

Effectiveness of radiomodifying action of natural mineral water (MW) of Berezovsky deposit in comparison with MW “Naftusya” was studied. It is shown that MW Berezovsky deposits are characterized by mild radioprotective properties. With prolonged use, MW deregulates prooxidant-antioxidant ratio and inhibits the oxidative metabolism in the peripheral blood of the animals