Waveguide-based single-pixel up-conversion infrared spectrometer

A periodically poled lithium niobate (PPLN) waveguide-based single-pixel up-conversion infrared spectrometer was demonstrated. Sum-frequency generation between a 1.5 micrometer band scanning pump laser and a 1.3 micrometer band signal generated visible radiation which was detected by a silicon single-photon detector. The noise equivalent power of the upconversion spectrometer was two-orders-of-magnitude lower than that of a commercial optical spectrum analyzer.Comment: 5 pages, 3 figure

The Bose-Einstein distribution functions and the multiparticle production at high energies

The evolution properties of propagating particles produced at high energies in a randomly distributed environment are studied. The finite size of the phase space of the multiparticle production region as well as the chaoticity can be derived.Comment: 18 pages, LaTeX, no figures, no table

X-ray analog pixel array detector for single synchrotron bunch time-resolved imaging

Dynamic x-ray studies may reach temporal resolutions limited by only the x-ray pulse duration if the detector is fast enough to segregate synchrotron pulses. An analog integrating pixel array detector with in-pixel storage and temporal resolution of around 150 ns, sufficient to isolate pulses, is presented. Analog integration minimizes count-rate limitations and in-pixel storage captures successive pulses. Fundamental tests of noise and linearity as well as high-speed laser measurements are shown. The detector resolved individual bunch trains at the Cornell High Energy Synchrotron Source (CHESS) at levels of up to 3.7x10^3 x-rays/pixel/train. When applied to turn-by-turn x-ray beam characterization single-shot intensity measurements were made with a repeatability of 0.4% and horizontal oscillations of the positron cloud were detected. This device is appropriate for time-resolved Bragg spot single crystal experiments.Comment: 9 pages, 11 figure

Simulations of Time-Resolved X-Ray Diffraction in Laue Geometry

A method of computer simulation of Time-Resolved X-ray Diffraction (TRXD) in asymmetric Laue (transmission) geometry with an arbitrary propagating strain perpendicular to the crystal surface is presented. We present two case studies for possible strain generation by short-pulse laser irradiation: (i) a thermoelastic-like analytic model; (ii) a numerical model including effects of electron-hole diffusion, Auger recombination, deformation potential and thermal diffusion. A comparison with recent experimental results is also presented.Comment: 9 pages, 11 figure

Method for Flavor Tagging in Neutral B Meson Decays

A method is proposed for tagging the flavor of neutral $B$ mesons in the study of CP-violating decay asymmetries. The method makes use of a possible difference in interactions in $B \pi$ or $B^* \pi$ systems with isospins 1/2 and 3/2, and would be particularly clean if the $I = 1/2$ systems can be detected as ``$B^{**}$'' resonances.Comment: Submitted to Phys. Rev. D. 11 pages, LaTeX, Technion-PH-92-40 / PITHA 92/39 / EFI 92-5

Like Sign Dilepton Signature for R-Parity Violating SUSY Search at the Tevatron Collider

The like sign dileptons provide the most promising signature for superparticle search in a large category of $R$-parity violating SUSY models. We estimate the like sign dilepton signals at the Tevatron collider, predicted by these models, over a wide region of the MSSM parameter space. One expects an unambiguous signal upto a gluino mass of $200 - 300$ GeV ($\geq 500$ GeV) with the present (proposed) accumulated luminosity of $\sim 0.1~(1)~{\rm fb}^{-1}$.Comment: 12 page LaTeX file; 5 figures available upon request from the autho

Collider discovery limits for supersymmetric Higgs bosons

The prospects for discovery of the five Higgs bosons of the minimal supersymmetric standard model are assessed for existing and planned future colliders, including LEP\,I, LEP\,II, LHC and SSC. As a benchmark for comparisons, we take a top-quark mass $m_t= 150\,$GeV and squark mass parameter $\tilde m= 1\,$TeV in evaluating one-loop radiative corrections; some results for other $m_t$ values are also given. Searches based on the most promising production and decay channels are taken into account. For large regions in parameter space, detectable signals are predicted for one or more of the Higgs bosons, but there remains a region for which no signals would be visible at the above colliders.Comment: 24 pages, 23 postscript figures available on request. MAD/PH/69

Picosecond laser-pump, x-ray probe spectroscopy of GaAs

A laser-pump, x-ray probe spectroscopic experiment is described, and the results are shown. The Ga KαKα x-ray fluorescence following x-ray absorption, at the Ga K absorption edge was measured, and its increase due to excitation with subpicosecond pulses of laser light at 4.6 eV photon energy was determined. The x-ray absorption, and thus the fluorescence, is increased for about 200 ps after the laser pulse because additional final states for the x-ray absorption are cleared in the valence band by the laser excitation. The technique could eventually lead to a femtosecond pump-probe spectroscopy with an absolute reference energy level and also to a femtosecond x-ray detector. This is of particular importance to future short-pulse x-ray sources, such as free-electron lasers. © 2002 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/69690/2/RSINAK-73-12-4150-1.pd

Radiative Corrections to Neutralino and Chargino Masses in the Minimal Supersymmetric Model

We determine the neutralino and chargino masses in the MSSM at one-loop. We perform a Feynman diagram calculation in the on-shell renormalization scheme, including quark/squark and lepton/slepton loops. We find generically the corrections are of order 6%. For a 20 GeV neutralino the corrections can be larger than 20%. The corrections change the region of $\mu,\ M_2,\ \tan\beta$ parameter space which is ruled out by LEP data. We demonstrate that, e.g., for a given $\mu$ and $\tan\beta$ the lower limit on the parameter $M_2$ can shift by 20 GeV.Comment: 11 pages, JHU-TIPAC-930030, PURD-TH-93-13, uses epsf.sty, 6 uuencoded postscript figures, added one sentence and a referenc