Search for Kaluza-Klein graviton emission in pp collisions at square root[s] = 1.8 TeV using the missing energy signature

We report on a search for direct Kaluza-Klein graviton production in a data sample of 84 pb(-1) of ppmacr; collisions at sqrt[s]=1.8 TeV, recorded by the Collider Detector at Fermilab. We investigate the final state of large missing transverse energy and one or two high energy jets. We compare the data with the predictions from a (3+1+n)-dimensional Kaluza-Klein scenario in which gravity becomes strong at the TeV scale. At 95% confidence level (C.L.) for n=2, 4, and 6 we exclude an effective Planck scale below 1.0, 0.77, and 0.71 TeV, respectively.     

Pseudo-dirac neutrinos: a challenge for neutrino telescopes

Neutrinos may be pseudo-Dirac states, such that each generation is actually composed of two maximally mixed Majorana neutrinos separated by a tiny mass difference. The usual active neutrino oscillation phenomenology would be unaltered if the pseudo-Dirac splittings are deltam(2) less, similar 10(-12) eV(2); in addition, neutrinoless double beta decay would be highly suppressed. However, it may be possible to distinguish pseudo-Dirac from Dirac neutrinos using high-energy astrophysical neutrinos. By measuring flavor ratios as a function of L/E, mass-squared differences down to deltam(2) approximately 10(-18) eV(2) can be reached. We comment on the possibility of probing cosmological parameters with neutrinos.     

Centralizers in Domains of Gelfand-Kirillov Dimension 2

Given an affine domain of Gelfand–Kirillov dimension 2over an algebraically closed field, it is shown that the centralizerof any non-scalar element of this domain is a commutative domainof Gelfand–Kirillov dimension 1 whenever the domain isnot polynomial identity. It is shown that the maximal subfieldsof the quotient division ring of a finitely graded Goldie algebraof Gelfand–Kirillov dimension 2 over a field F all havetranscendence degree 1 over F. Finally, centralizers of elementsin a finitely graded Goldie domain of Gelfand–Kirillovdimension 2 over an algebraically closed field are considered.In this case, it is shown that the centralizer of a non-scalarelement is an affine commutative domain of Gelfand–Kirillovdimension 1. 2000 Mathematics Subject Classification 16P90.     

Effect of N isotopic mass on the photoluminescence and cathodoluminescence spectra of gallium nitride

GaN is a wurtzite-type semiconductor at ambient conditions whose natural composition consists of almost pure ¹⁴N (99.63% ¹⁴N and 0.37% ¹⁵N) and a mixture of 60.1% ⁶⁹Ga, and 39.9% ⁷¹Ga. We report a low-temperature photoluminescence and cathodoluminescence study of GaN thin films made from natural Ga and N, and from natural Ga and isotopically pure ¹⁵N. The contribution of the nitrogen vibrations to the bandgap renormalization by electron-phonon interaction has been estimated from the nitrogen isotopic mass coefficient of the bound exciton energy. The temperature dependence of the bandgap of GaN can be explained with the measured isotopic mass coefficients of Ga and N. We have estimated the aluminum and indium contribution to the bandgap renormalization in AlN and InN from the temperature dependence of the AlN and InN bandgap up to 300 K, assuming that the N contribution is similar to that found in GaN. The similar bandgap isotopic mass coefficients of C, N, and O, of Al, Si and P, of Zn, Ga and Ge, and of Cd and In suggests that elements of the same row of the periodic table have similar bandgap isotopic mass coefficients.Received: 5 December 2004, Published online: 20 July 2004PACS: 71.20.Nr Semiconductor compounds     

Binding energy of an electron to a three-defect-complex in CdTe

Recent measurements on halogen doped CdTe shows an unidentified electron trapping level at 0.05 eV. Using a mass action approach to self compensation involving a substitutional halogen, X_Te, and a cadmium vacancy, V_Cd, it can be shown that in addition to the two-defect complex, V_CdX_Te, the three-defect complex (V_Cd2X_Te) is present in substantial concentrations. A calculation of the binding energy of an electron to this three-defect-complex using the configurational interaction and one electron wave function, leads to a bound state with a depth about right for the unidentified level.     

Isospin bounds for energy partition in ee and NN annihilation

In reactions such as $\text{e}$e → anything, $\text{N}$N → anything, the final state (neglecting secondary isospin violating decays) is customarily supposed to have isospin zero or one. We show that for such states the average fraction (X) of the energy carried away by neutral pions is bounded by $\text{X<}\text{(9+√41)}\text{20}\text{≈0.77}$, when I₃ = 0 (e.g., for ee, pp, nn) and by $\text{X>}\text{(11?√41)}\text{40}\text{≈0.115}$, when I₃=±1 (e.g., for pn or np).     

Thermal shrinkage of oriented semicrystalline poly(ethylene terephthalate)

The shrinkage of commercial oriented poly(ethylene terephthalate) filaments was studied within the framework of the kinetic theory of rubberlike elasticity. Previous workers had found that the shrinkage and optical behavior of amorphous polymers could be satisfactorily explained in terms of this theory. Such an analysis is now applied to semicrystalline samples of moderate and high draw ratios (from 2× to 6×). It was found in this work that the thermal shrinkage force behavior as well as the optical anisotropy as a function of stretch can be explained in terms of the theory of rubberlike elasticity, if the following reasonable assumption is made: the average number of statistical segments per network chain in the noncrosslinked sample increases as a function of the draw ratio. A possible mechanism for such behavior is the relaxation of some of the chain entaglements due to the strain imposed externally on the fiber.     

The π ← n transition of formic acid

New sharp bands of formic acid have been observed in the near ultraviolet at the long wave-length end of the previously observed diffuse band system (2250–2500 Å) by considerably extending the absorption path length. Both the diffuse and sharp bands belong to the same vibrational system which is assigned to the π^* ← n electronic transition in the carbonyl group. Extensive progressions are observed in the carbonyl stretching frequency which is greatly reduced in the excited state (fundamental ν₃′ ≈ 1080 cm⁻¹) and many intervals of about 400 cm⁻¹ are assigned to the OCO bending frequency ν₇′.A band contour analysis of the 2593 Å band shows that the molecule is nonplanar in the excited state because of the magnitude and sign of the inertial defect. From this analysis, the rotational constants for the excited state are S^‘=1.8755, B^‘0.4042, C^‘=0.3378cm⁻¹ By the plausible assumption that the important changes in the molecule are in the C=0 bond length, the OCO angle, and the nonplanarity due to the formyl hydrogen, the following excited state parameters are derived.rC=0 = 1.407A.The changes in formic acid are closely analogous to the changes in formyl fluoride as a result of the π^* ← n transition.     

Development of a headspace gas chromatography method to determine residual aliphatic amines in oligonucleotides

A headspace gas chromatographic method has been developed for analysis of aliphatic amines in oligonucleotides. The linearity was improved by including ammonia in the sample vials. Also, carryover of longer chain primary amines, hexylamine and octylamine, was substantially reduced by cleaning the injection syringe with ammonia and water vapor between sample injections.