Soft photon production in 450 GeV/cp-Be collisions

We have measured the inclusivep _T spectra of soft photons produced at central and backward rapidities in 450 GeV/cp-Be collisions down to 1 MeV/c in transverse momentum. In the region 1<p _T <20 MeV/c an excess of photons over those expected from hadronic decays is observed. This excess is comparable, within systematic errors, with estimates of direct photons produced via hadronic bremsstrahlung. An upper limit is derived on the presence of additional sources of direct photons at small transverse momentum.     

Interpretation of ESI(+)-MS-MS spectra—Towards the identification of “unknowns”

We report a systematic empirical investigation of ESI(+)-MS-MS dissociation pathways of over 1000 spectra of small organic compounds, containing more than 30 chemical functional groups. The dissociation processes of the protonated molecular ions were explored and interpretated. We derived typical basic fragmentation channels for individual functional groups and established a unified set of fragmentation rules. Multiple bond cleavages of molecules containing single and multiple functional groups were explored as well and the corresponding fragmentation rules were derived. Applying these rules enabled to match between proposed chemical structures and an ESI(+)-MS-MS spectrum of an “unknown”. Comparison to EI fragmentation routes was also carried out. Despite the general dissimilarity between ESI(+)-MS-MS and EI-MS spectra, we exploit the minor similarities between the spectra, and utilizing NIST-EI database and search option, can be successfully reduced the number of proposed structures. The two step methodology developed here is demonstrated and evaluated in the identification of various “unknowns”.     

Identification of G‐nerve agents at picogram levels from complex organic samples containing hydrocarbon interferences by aqueous extraction,followed by derivatization and liquid chromatography‐mass spectrometry analysis

The chromatograms obtained from the gas chromatography‐electron ionization mass spectrometric (GC‐EI‐MS) analysis of extracts containing G‐nerve agents in the presence of diesel, gasoline, etc., are dominated by hydrocarbon backgrounds that “mask” the G‐nerve agents, leading to severe difficulties in identification. This paper presents a practical solution for this challenge by transferring the G‐nerve agents from the organic phase into the aqueous phase using liquid‐liquid extraction (LLE), followed by derivatization with 2‐[(dimethylamino)methyl]phenol (2‐DMAMP), allowing ultrasensitive LC‐ESI‐MS/MS analysis of the G‐derivatives. The proposed approach enables rapid identification of trace amounts of G‐nerve agents with limits of identification (LOIs) at the pg/mL scale.     

Study of quasi two-body final states in K−n reactions at 8.25 GeV/c

Cross sections for various channels in 3 prong + V₀ final states of K^?n interactions are obtained at 8.25 GeV/c. An energy dependence study of the quasi two-body reactions Σ^?(1385) + vector meson and ΛB^? seem to imply the presence of cuts in the Regge exchange formalism, whereas the reaction Δ(1236) $\text{K}$¹ (890) does not require such cuts. Upper limits of 1 and 2 μb are found for the reactions K^?n → ΛA₁ and K^?n → ΛA₂.     

An amplitude analysis of ππ scattering from new data on the reaction π−p→π+π−n

We have carried out a partial-wave analysis of ππ scattering in the mass range 1.0 to 2.08 GeV/c². We find solutions similar to those obtained in previous analyses below 1.8 GeV/c² but, in addition, we obtain a new solution which does not suffer from violations of unitarity and is compatible with data from other channels. This solution, when continued to 2.08 GeV/c², shows a g meson with mass and width of 1.734± 0.010 GeV/c²and 0.322±0.035 GeV/c² respectively, and an h meson with mass 1.935±0.013 GeV/c²and width 0.263±0.057 GeV/c². The L = 2 partial wave contains the f meson and an additional resonance with parameters m = 1.502±0.025 Gev/c², Γ = 0.165±0.042 GeV/c²and x = 0.19±0.03. If we associate this state with the f′(1514), our ππ branching fraction is considerably higher than previous determinations. An SU(3) fit to the 2⁺ nonet yields a mixing angle of 38.4± 1.3°.     

Evidence for a quantum phase transition in Pr2-xCe(x)CuO4-delta from transport measurements

The doping and temperature dependences of the Hall coefficient, R(H), and ab-plane resistivity in the normal state down to 350 mK is reported for oriented films of the electron-doped high-T(c) superconductor Pr(2-x)Ce(x)CuO(4-delta). The doping dependences of beta (rho=rho(0)+ATbeta) and R(H) (at 350 mK) suggest a quantum phase transition at a critical doping near x=0.165.