Large-angle production of charged pions by 3?GeV/c–12?GeV/c protons on carbon, copper and tin targets

A measurement of the double-differential π^± production cross-section in proton–carbon, proton–copper and proton–tin collisions in the range of pion momentum 100 MeV/c≤p<800 MeV/c and angle 0.35 rad≤θ<2.15 rad is presented. The data were taken with the HARP detector in the T9 beam line of the CERN PS. The pions were produced by proton beams in a momentum range from 3 GeV/c to 12 GeV/c hitting a target with a thickness of 5% of a nuclear interaction length. The tracking and identification of the produced particles was done using a small-radius cylindrical time projection chamber (TPC) placed in a solenoidal magnet. An elaborate system of detectors in the beam line ensured the identification of the incident particles. Results are shown for the double-differential cross-sections d²σ/dpdθ at four incident proton beam momenta (3 GeV/c, 5 GeV/c, 8 GeV/c and 12 GeV/c). PACS 13.75.Cs; 13.85.Ni     

Pion cloud and the sea of the nucleon

I review recent progress in understanding the structure of the nucleon sea and the role of the nucleon’s pion cloud. In particular, I discuss the consequences of the pion cloud for the ƌ−ū asymmetry in the proton, the neutron’s electric form factor, and the proton’s electric to magnetic form factor ratio.     

Ramsauer–Townsend Effect in Solid Hydrogen

The TRIUMF E742 experiment has measured the energy dependence of the scattering cross-sections of muonic deuterium and tritium on hydrogen molecules for collisions in the energy range 0.1–45 eV. The experimental setup permits the creation of muonic atom (μd or μt) beams. The multilayered target system gives the possibility to choose the type of interactions to study and to isolate a particular interaction. The scattering of μd or μt beams on H₂ is analyzed via the muon transfer reaction to neon. The time-of-flight method is used to measure the scattering cross section as a function of the energy of the muonic atom beam. The results are compared, using Monte Carlo simulations, with theoretical calculations which have been recently performed with high accuracy. This revised version was published online in August 2006 with corrections to the Cover Date.     

Measurement of the Temperature Dependence of the ddμ-Molecule Formation Rate in Dense Deuterium at Temperatures 300–800 K

Muon catalyzed fusion in deuterium was studied by the MCF collaboration at JINR phasotron. The measurements were carried out with a high-pressure deuterium target at the JINR phasotron in the temperature range 300–800 K at densities ≃0.5 LHD. The first experimental results for ddμ-molecule formation rate λ _ddμ in the temperature range 400–800 K with deuterium density 0.5 LHD are presented. This revised version was published online in August 2006 with corrections to the Cover Date.     

The pion–nucleon scattering lengths from pionic hydrogen and deuterium

This is the final publication of the ETH Zurich–Neuchatel–PSI collaboration on the pionic hydrogen and deuterium precision X-ray experiments. We describe the recent hydrogen 3p–1s measurement, report on the determination of the Doppler effect correction to the transition line width, analyze the deuterium shift measurement and discuss implications of the combined hydrogen and deuterium results. From the pionic hydrogen 3p–1s transition experiments we obtain the strong-interaction energy level shift eV and the total decay width eV of the state. Taking into account the electromagnetic corrections we find the hadronic s-wave scattering amplitude for elastic scattering and for single charge exchange, respectively. We then combine the pionic hydrogen results with the 1s level shift measurement on pionic deuterium and test isospin symmetry of the strong interaction: our data are still compatible with isospin symmetry. The isoscalar and isovector scattering lengths (within the framework of isospin symmetry) are found to be and , respectively. Using the GMO sum rule, we obtain from a new value of the coupling constant () from which follows the Goldberger–Treiman discrepancy . The new values of and imply an increase of the nucleon sigma term by at least 9 MeV. Received: 20 April 2001 / Revised version: 6 July 2001 / Published online: 24 August 2001     

The μCF Experiments at PSI – A Conclusive Review

During 25 years pioneering μCF experiments were performed at PSI. After initial study of the Wolfenstein–Gershtein effect in H/D, an intense research program on dμd fusion led to the early discovery of resonant dμd formation at low temperature and to the first direct observation of μd spin flip. With the Gatchina ionisation chamber absolute precisions of ∼1% on the determination of dμd formation and spin flip rates were recently obtained in good agreement with the theory. In a very large effort the highly resonant dμt fusion cycle was investigated. Record cycle rates up to 2×10⁸ s⁻¹ and yields up to 124 fusions per muon were measured. By slope analysis and by direct observation, effective sticking ω _s = (0.505 ± 0.029)% is the final PSI result. Clear experimental evidence of large epithermal resonances in D/T and H/D/T mixtures was found. This revised version was published online in August 2006 with corrections to the Cover Date.     

Nuclear fusion in the mesic molecule d μ 3He

A new scheme is presented for the physical processes leading to the nuclear fusion reaction d(³He, ⁴He)p catalyzed by a negatively charged muon μ⁻. It is shown that the observable rate and yield of the nuclear reaction depend on a chain of ion-molecular reactions involving the participation of the dμ ³He molecule. New calculations of the nuclear fusion rates in the dμ³He molecule are presented. Pis’ma Zh. éksp. Teor. Fiz. 67, No. 2, 89–94 (25 January 1998) Published in English in the original Russian journal. Edited by Steve Torstveit.     

Determination of thin film refractive index and thickness by means of film phase thickness

A new approach for determination of refractive index dispersion n(λ) (the real part of the complex refractive index) and thickness d of thin films of negligible absorption and weak dispersion is proposed. The calculation procedure is based on determination of the phase thickness of the film in the spectral region of measured transmittance data. All points of measured spectra are included in the calculations. Barium titanate thin films are investigated in the spectral region 0.38–0.78 μm and their n(λ) and d are calculated. The approach is validated using Swanepoel’s method and it is found to be applicable for relatively thin films when measured transmittance spectra have one minimum and one maximum only.      

Radial distribution of hydrogen atoms in H 2 plasma

The radial intensities of the H _α and H ₂ Fulcher α (d ³Π_u − a ³Σ_g) system spectral lines were used to obtain the radial distribution of hydrogen atoms in H ₂ plasma discharge. We have obtained new equations in order to describe the distribution of atoms in molecule discharges. Abel’s integral equation has been solved by Tikhonov’s regularization procedure. Model functions have been introduced to examine the limitations in the applicability of this method. An estimation of the degree of dissociation in the radial direction has been obtained.     

Large-angle production of charged pions by 3-12.9?GeV/c protons on beryllium, aluminium and lead targets

Measurements of the double-differential π^± production cross-section in the range of momentum 100 MeV/c≤p< 800 MeV/c and angle 0.35 rad ≤θ<  2.15 rad in proton–beryllium, proton–aluminium and proton–lead collisions are presented. The data were taken with the HARP detector in the T9 beam line of the CERN PS. The pions were produced by proton beams in a momentum range from 3 GeV/c to 12.9 GeV/c hitting a target with a thickness of 5% of a nuclear interaction length. The tracking and identification of the produced particles was performed using a small-radius cylindrical time projection chamber (TPC) placed inside a solenoidal magnet. Incident particles were identified by an elaborate system of beam detectors. Results are obtained for the double-differential cross-sections d²σ/dpdθ at six incident proton beam momenta (3 GeV/c, 5 GeV/c, 8 GeV/c, 8.9 GeV/c (Be only), 12 GeV/c and 12.9 GeV/c (Al only)) and compared to previously available data.     

Chandrasekhar’s book <Emphasis Type="Italic">An Introduction to the Study of Stellar Structure</Emphasis>

For me, and for many astrophysicists of my generation, Chandrasekhar’s book An Introduction to the Study of Stellar Structure was very important. I could not have done my PhD (1962–1965) without it. Much more recently (1998) I realized that I could not have written my lecture course on thermodynamics and statistical mechanics without much of it, particularly the first chapter. I shall present anecdotal evidence that the influence of his discussion on the second law of thermodynamics has been important not just for astrophysics but for a much wider range of physics.     

Experimental study of the energy gap in the spin-wave spectrum in Co/Pd multilayer films

The energy gap appearing in the spin-wave spectrum as a result of Bragg scattering by the modulation period q=2π/(d ₁+d ₂) of a one-dimensional superlattice is observed by the method of spin-wave resonance in Co/Pd multilayer films. It is shown that this gap is asymmetric: The “positive” deviation is from two to three times greater than the “negative” deviation. Pis’ma Zh. éksp. Teor. Fiz. 63, No. 12, 938–941 (25 June 1996)     

Soft diffraction at the LHC: a partonic interpretation

We present a ‘new generation’ model for high energy proton–proton ‘soft’ interactions. It allows for a full set of multipomeron vertices as well as for including multichannel eikonal scattering. It describes the behaviour of the proton–proton total, σ_tot, and elastic, dσ_el/dt, cross sections together with those for low- and high-mass proton dissociation. Although the model contains a comprehensive set of multipomeron diagrams, it has a simple partonic interpretation. Including the more complicated multipomeron vertices reduces the absorptive effects as compared to the predictions in which only the triple-pomeron vertex is considered. Tuning the model to describe the available ‘soft’ data in the CERN ISR–tevatron energy range, we predict the total, elastic, single- and double-diffractive dissociation cross sections at the LHC energy. An inescapable consequence of including multichannel eikonal and multipomeron effects is that the total cross section is expected to be lower than before: indeed, we find σ_tot≃ 90 mb at the LHC energy. We also present differential forms of the cross sections. In addition, we calculate soft diffractive central production.     

High-Pressure Hydrogen Isotopes Sources Based on Vanadium Hydride

Equilibrium pressures of protium and deuterium desorption over a two-phase area of monohydride-vanadium dihydride were measured. Temperature measurement range was 300–635 K and the pressure range 1–500 MPa. Obtained temperature-dependences of fugacities within the given measurement range are: lgf(MPa) = −2152/T+ 6.6 and lgf(MPa) = −2575/T + 7.4 for protium and deuterium, respectively. The values of enthalpy and entropy for vanadium dihydride phase formation were calculated from obtained relations. Using expressions obtained for fugacities and literature data on hydrogen imperfection the pressures, which can be obtained with vanadium dihydride employed in thermodesorption hydrogen sources, were estimated. Taking into account that due to deterioration in strength properties of the used structural materials, the heating temperature of the load-bearing body is limited to ∼973 K, maximal calculated pressure, which can be obtained with such sources as ≈1820 MPa for protium and ≈2220 MPa for deuterium. This revised version was published online in August 2006 with corrections to the Cover Date.     

Extension of the sum rule for the transition rates between multiplets to the multiphoton case

The sum rule for the transition rates between the components of two multiplets, known for the one-photon transitions, is extended to the multiphoton transitions in hydrogen and hydrogen-like ions. As an example the transitions 3p–2p, 4p–3p and 4d–3d are considered. The numerical results are compared with previous calculations.     

Investigation of the Parameters of Muon-Catalyzed Fusion in Double D/T Mixture at High Temperature and Density

Experiments on the study of the muon catalyzed fusion (μCF) process in a double D/T mixture of hydrogen isotopes in the temperature range 300–800 K at densities 0.3–0.5 LHD are performed at the JINR phasotron. The values of the effective μCF parameters (cycling rate λ _c , neutron yield Y _n , muon losses w) are obtained. Tentative dtμ-molecule formation rates on D₂ and DT molecules (λ _dtμ−d and λ _dtμ−t ) are obtained for different mixture temperatures and densities. The results obtained show that λ _dtμ−t increases with temperature, but its value is smaller than theoretical predictions. This revised version was published online in August 2006 with corrections to the Cover Date.     

Muonic Molecule Formation in Condensed Deuterium

Resonant formation of the muonic molecule ddμ in dμ atom scattering in condensed deuterium is considered. In particular, ddμ formation in D₂ solid targets containing different ortho-D₂ concentration is discussed, and the respective time spectra of the dd fusion products are shown. The results of the first calculation of the resonant ddμ formation rate in liquid deuterium are presented. At large momentum transfers the ddμ formation rate takes the Doppler form, similar to that obtained for a dilute gas target. A condition of validity of this approximation is also discussed. This revised version was published online in August 2006 with corrections to the Cover Date.     

Development of the Chemical Oxygen-Iodine Laser (COIL) with chemical generation of atomic iodine

This article addresses the development of a Chemical Oxygen-Iodine Laser (COIL) with alternative chemical ways of generating atomic iodine. Injection of atomic iodine as opposed to molecular iodine has the potential to improve the COIL efficiency. This paper describes two chemical methods for generating iodine atoms based on the gas phase reactions of hydrogen/deuterium iodide with fluorine or chlorine atoms, which are also produced chemically. Simplified one-dimensional gas dynamic modeling that describes the stream-wise profiles of species concentrations within both reaction systems is used to gain a theoretical understanding of both reaction systems under COIL conditions. The modeling results are used for the design of an experimental device and the interpretation of experimental data. The first experimental investigation studies the production of iodine atoms produced from reactions of Cl with HI. Atomic iodine yields of 70–100% in nitrogen are obtained, and the gain on the I(² P _1/2)–I(² P _3/2) transition in a flow of singlet oxygen is measured. Received: 7 October 2002 / Accepted: 8 February 2003 / Published online: 28 May 2003 RID="*" ID="*"Corresponding author. Fax: +420-2/8689-0527, E-mail: kodym@fzu.cz     

On the phase transition d→(s±id) in high-T c superconductors

A model with an attractive potential in the s and d channels is studied. It is found that in a definite interval of the ratio of the s and d components of the potential the model undergoes a second-order phase transition from the d to the (s±id) state, with breaking of time-reversal symmetry. The transition temperature and the jump in the specific heat are calculated. Pis’ma Zh. éksp. Teor. Fiz. 64, No. 8, 570–574 (25 October 1996)     

Can microbes mediate nano-transformation?

A green low-cost and reproducible microbe (Lactobacillus) and baker’s yeast (Saccharomyces cerevisiae) mediated biosynthesis of metallic and oxide nanoparticles are reported. Silver and copper oxide nanoparticles are synthesized using Lactobacillus sp. and Saccharomyces cerevisiae. The synthesis is performed akin to room temperature in the laboratory ambience. X-ray and transmission electron microscopy analyses are performed to ascertain the formation of metallic and oxide nanoparticles. Individual nanoparticles having the dimensions of 2–6 nm (metallic) and 10–20 nm (oxide) are found. A possible mechanism involved for the synthesis of metallic and oxide nanoparticles has also been proposed in which pH as well as the partial pressure of gaseous hydrogen (r-H₂) or redox potential of the culture solution seem to play an important role in the process.