Infrared heterodyne radiometer for airborne atmospheric transmittance measurements

An infrared heterodyne radiometer (IHR) was used to measure atmospheric transmittance at selected hydrogen fluoride (2.7 micrometer) and deuterium fluoride (3.8 micrometer) laser transitions. The IHR was installed aboard a KC-135 aircraft for an airborne atmospheric measurements program that used the sun as a backlighting source for the transmission measurements. The critical components are: a wideband indium antimonide (1nSb) photomixer, a CW HF/DF laser L0, a radiometric processor, and a 1900 K blackbody reference source. The measured heterodyne receiver sensitivity (NEP) is 1.3 x 10 to the -19th power W/Hz, which yields a calculated IHR temperature resolution accuracy of delta I sub S/-3 sub S = 0.005 for a source temperature of 1000 K and a total transmittance of 0.5. Measured atmospheric transmittance at several wavelengths and aircraft altitudes from 9.14 km (30,000 ft) to 13.72 km (45,000 ft) were obtained during the measurements program and have been compared with values predicted by the AFGL Atmospheric Line Parameter Compilation

A leed analysis of the (2×1)H-Ni(110) structure

A monolayer of H atoms adsorbed on Ni(110) below 180 K forms a (2×1) structure. The unit cell exhibits a glide symmetry plane and contains two adsorbed atoms. Based on a quantitative comparison between experimental and calculated LEED I/V spectra using standard R-factors the following structure was derived: On the clean Ni(110) surface the separation between the first two atomic layers, d12, is contracted by 8.5%±1.5% with respect to the bulk value; those between the second and third and the third and fourth layer, d23 and d34, are expanded by 3.5%±1.5% and 1%±1.5%, respectively—in agreement with recent other results. In the presence of the H adlayer the contraction of d12 is reduced to 4.5%±1.5%, while the expansion of d23 is not affected within the limits of accuracy. The third interlayer spacing d34 returns to its bulk value. The H atoms occupy threefold-coordinated sites formed by two Ni atoms from the first layer and one Ni atom from the second layer which confirms previous more qualitative conclusions based on He diffraction and vibrational spectroscopy. The bond lengths between H and its neighbouring Ni atoms were determined to be equal, namely 1.72±0.1 Å

Search for the standard model Higgs boson in the H to ZZ to 2l 2nu channel in pp collisions at sqrt(s) = 7 TeV

A search for the standard model Higgs boson in the H to ZZ to 2l 2nu decay channel, where l = e or mu, in pp collisions at a center-of-mass energy of 7 TeV is presented. The data were collected at the LHC, with the CMS detector, and correspond to an integrated luminosity of 4.6 inverse femtobarns. No significant excess is observed above the background expectation, and upper limits are set on the Higgs boson production cross section. The presence of the standard model Higgs boson with a mass in the 270-440 GeV range is excluded at 95% confidence level.Comment: Submitted to JHE

Combined search for the quarks of a sequential fourth generation

Results are presented from a search for a fourth generation of quarks produced singly or in pairs in a data set corresponding to an integrated luminosity of 5 inverse femtobarns recorded by the CMS experiment at the LHC in 2011. A novel strategy has been developed for a combined search for quarks of the up and down type in decay channels with at least one isolated muon or electron. Limits on the mass of the fourth-generation quarks and the relevant Cabibbo-Kobayashi-Maskawa matrix elements are derived in the context of a simple extension of the standard model with a sequential fourth generation of fermions. The existence of mass-degenerate fourth-generation quarks with masses below 685 GeV is excluded at 95% confidence level for minimal off-diagonal mixing between the third- and the fourth-generation quarks. With a mass difference of 25 GeV between the quark masses, the obtained limit on the masses of the fourth-generation quarks shifts by about +/- 20 GeV. These results significantly reduce the allowed parameter space for a fourth generation of fermions.Comment: Replaced with published version. Added journal reference and DO