Browsing by Author "Mutchler, Gordon S."
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Item 100-microsecond-resolved exafs technique for studying photolyzed hemoproteins(1984) Teng, Tsu-Yi; Huang, Huey W.; Rorschach, Harold E.; Mutchler, Gordon S.This thesis describes a 1-jus-resolved extended x-ray absorption fine structre (EXAFS) technique for studying protein dynamics. Both the time-resolved EXAFS spectrometer and the protein samples are described in detail. About ten years ago synchrotron radiation from electron storage rings began to be used for research in condensed matter. As a result a new technique for studying local structures in non-crystalline system was developed i.e. the extended x-ray absorption fine structure. This technique has now become an important tool for the structural studies of biological systems, particularly metalloproteins. In recent years the development of wiggler and undulator magnets has increased the radiation intensity to a level that, according to photon statistics, it should be possible to measure the EXAFS of hemoproteins in their transient states. Such measurements would provide structural insight to the very difficult but important problem of protein dynamics. However the conventional method of EXAFS measurement is inefficient for time-resolved measurement. We have developed a new spectrometer to take full advantage of the intense radiation. The time resolution of our spectrometer is about 1 us; below that the measurement time would be too long. Myoglobin was chosen as our sample for its importance in protein biophysics. The complex of myoglobin and carbon monoxide (CO) can be dissociated by light (flash photolysis). Its recombination time ranges from microseconds to infinity depending on temperature. The time resolved EXAFS measurement of photolyzed carboxymyoglobin will reveal the structural changes of protein around the CO binding site during the recombination process. We made our sample in the form of a thin film so that it can meet different requirments of x-ray absorption and optical photolysis. A special procedure of sample making was developed, and a transient optical absorption spectrometer was built for testing the samples. All optical absorption properties of our samples are in agreement with known results. An actual time-resolved EXAFS experiment was performed in February, 1983. The result showed no change in EXAFS with time. This might be due to a failure in photolysis (we lacked an on-line transient optical absorption spectrometer). However, these results demonstrated the feasibility and reliability of our spectrometer.Item An ionization chamber technique for the measurement of the transverse spin dependence of the proton-proton total cross-section(1981) Madigan, William Paul; Phillips, Gerald C.; Mutchler, Gordon S.; Baker, Stephen D.High precision ionization chambers were designed end built to measure the transverse spin dependence of the proton-proton total cross-section difference in the 318 MeV to 8 MeV energy region. Severe microphonic noise was minimized by mounting one of the chambers on pneumatic vibration isolators. Consideration of large fluctuations of the ionization produced in the thin gas layers of the chambers and the measured electronics noise accounts for about 6% of the resolution width of the measurement. Additional effects such as the beam intermittently scraping the target cavity, secondary emission of electrons, and beam-related RF pickup are postulated to account for the remaining width. Designing, constructing, and operation the high-precision ionization chambers has greatly improved our understanding of high-accuracy applications of ionization chambers and analog electronics.Item Analysing power of inclusively produced pions using high energy polarized protons(1988) Moss, Robert Michael; Mutchler, Gordon S.The analysing power A$\sb{\rm N}$ of inclusively produced charged pions is measured using 13.3 and 18.5 GeV/c polarized protons from the Brookhaven AGS. The measurement was performed at the Multiparticle Spectrometer in early 1986, in conjunction with a measurement of inclusively produced $\Lambda$ particles. There are two possible theoretical explanations for the data. A baryon exchange model is discussed in light of the previous measurements of the pion analysing power. This model is dependent on the scanty backward $\pi$p elastic data that is available at lower energies. A more modern quark recombination model which uses SU(6) symmetry and the idea that the spin of the quarks is preserved in the scattering and recombination process is used to make specific predictions concerning the analysing power of inclusively produced particles. The quark model predicts that A$\sb{\rm N}$ should be positive for $\pi\sp{+}$ and negative for $\pi\sp{-}$ in the beam fragmentation region. The data analysis consists of pattern recognition and track reconstruction of the tracks in the spectrometer, and identification of the pions. The background consists of particles that did not originate in the target, and particles which may have passed through the edges of drift chamber frames. Minimal cuts are applied to the data, requiring that the pions come from the target and pass through the drift chamber active areas. The acceptance of the apparatus was verified by Monte Carlo calculation. The measured vertical component of the beam polarization P$\sb{\rm N}$ was 0.379 $\pm$ 0.020 at 18.5 GeV/c. At 13.3 GeV/c, P$\sb{\rm N}$ was measured to be 0.5900 $\pm$ 0.0130. The analysing power for $\pi\sp{-}$ over the range of 0.1 $\leq$ X$\sb{\rm F}$ $\leq$ 0.7 was found to be almost negligible, with a value of 0.0037 $\pm$ 0.0036 at 13 GeV/c when calculated for all transverse momenta. A$\sb{\rm N}$ for $\pi\sp{-}$ is observed to be negative in the highest X$\sb{\rm F}$-P$\sb{\rm T}$ bin measured. The $\pi\sp{+}$ analysing power is found to be positive, increasing approximately linearly with increasing X$\sb{\rm F}$, and is observed to have a flat dependence upon P$\sb{\rm T}$, with a value of 0.047 $\pm$ 0.0034 when averaged over all P$\sb{\rm T}$ and X$\sb{\rm F}$. Our measurement is found to be in qualitative agreement with the predictions of the quark recombination model.Item Calibration of a high energy neutron detector(1975) Felder, Richard Douglas; Mutchler, Gordon S.The detection efficiency of a large cylindrical block of NE-12 scintillator was measured for neutrons with energies from 2 to 5 MeV. The experimental technique employed quasi-free p-n and p-p scattering from p-d breakup at 8 MeV and relied on the spectator model description of these processes. The measured efficiencies are 15% to 4% larger than the best calculated efficiencies and show an increasing deviation with neutron energy. The observed discrepancies are explained in terms of nuclear in-scattering and possible deficiencies in the spectator model. Several changes in the experimental apparatus and technique are suggested to improve the efficiency measurement.Item Construction of the E-683 hodoscope and preliminary calibration of the E-683 main calorimeter(1990) Traynor, Michael; Mutchler, Gordon S.I have designed and constructed a muon hodoscope/veto counter for E-683 at Fermilab. Preliminary tests indicate that the efficiency of each scintillator is $\approx$99.9%, allowing the hodoscope layers to be used in coincidence mode. The calibration of the modules in the E-683 main calorimeter has been studied using muons from the 1987-88 parasitic run. Preliminary calibration reveals that the calorimeter's response is within the parameters observed in E-609. Further, new information reveals the response of calorimeter modules to different physical triggers. The response of the calorimeter modules to different voltage thresholds, neighbor cuts, and gate timings has been analyzed. Results from the 1990 parasitic run indicate that the gate timing should precede the signal by 80 ns. After developing a new program to analyze the data from the entire calorimeter, I have begun muon balancing of all the modules. (Abstract shortened with permission of author.)Item [Delta]+ production in the PP --> PP[pi] [omicron] reaction at 800 MeV(1980) Pepin, Gregory Paul; Mutchler, Gordon S.; Phillips, Gerald C.; Baker, Stephen D.Fifth order differential cross sections have been measured for the reaction during two experiments using the 8 MeV External Proton Beam at the Los Alamos Meson Physics Facility (LAMPF). The kinematically complete data were obtained at seven angular settings covering a range of four-momentum transfers. The protons were detected by MWPC counters on two arms which measured the reaction angles for both charged particles. A magnetic spectrometer measured the momentum of one of the protons. The measured cross sections were compared to calculations using a peripheral model of pion production. Results indicate that the data can be fit with a single value of the pion form factor parameter whose value is much larger than that predicted using optical model calculations.Item Development of a computer controlled Fizeau wavemeter(1985) Gray, Damien Francis; Dunning, F. Barry; Jeys, Thomas H.; Mutchler, Gordon S.A Fizeau wavemeter bas been developed that has demonstrated an accuracy of 1 part in 1^6 across the visible spectrum and 5 parts in 1^7 across any 1 A interval. The present design is a modified version of that initially proposed by Gardner. The design was optimized by developing a computer model of the instrument. This model suggests that the theoretical accuracy limit for this type of wavemeter is on the order of 1 part in 1^8.Item Differential cross sections for neutral-neutral and charge-transfer collisions(1985) Schafer, David Allen; Stebbings, Ronald F.; Dunning, F. Barry; Mutchler, Gordon S.Absolute differential cross sections for neutral-neutral and charge—transfer collisions involving fast oxygen are presented. Neutral-neutral collisions are measured over the energy range 5-5eV, and between angles of .1 degrees and 5. degrees, while charge transfer measurements are presented for 15eV oxygen ions over the same angular range. A position sensitive detector is used to detect both the primary and scattered particles, yielding absolute differential cross sections. Target chambers with small ratios of length to exit aperture diameter are used and the end effects due to gas streaming out of the aperture are estimated by a Monte Carlo computer simulation. The excited state composition of the oxygen ion beam is considered, and differential cross sections for charge transfer are presented for both ground and excited-state oxygen ions.Item Energy dependent electron polarization studies of penning ionization channels(1985) Ratliff, John Martin; Walters, G. King; Dunning, F. Barry; Mutchler, Gordon S.Penning ionization reactions have been studied in a flowing afterglow apparatus to explore the contributions of autoionizing channels in reactions of spin-polarized He(23S) with alkali atoms. Spin polarization analysis of the Penning electrons has allowed us to identify a significant autoionizing channel for rubidium, and no such contribution for cesium and potassium. Using the results of this study, a model of the reaction process was constructed to predict the Penning electron polarization produced in He(23S) -- polarized rubidium reactions. An attempt to measure this polarization was made, but it became clear in the course of the experiment that success is possible only with a substantially upgraded apparatus. A simultaneous energy and polarization measurement of the electrons produced in reactions of polarized He(23S) with 2 has also been attempted. This initial experiment was unsuccessful but indicates that results can be obtained, again given an improved apparatus.Item Event reconstruction using the linear correlation probability for fixed targets at 400 GEV(1985) Moore, Robert Christopher; Corcoran, Marjorie D.; Miettinen, Hannu E.; Mutchler, Gordon S.Adaptations of the Fermilab E69 event reconstruction program were made to increase its speed and versatility. An attempt to increase the number of chambers utilized per track prompted the examination of a new track selection criterion, the linear correlation probability. A comparative study of the merits of the probability of linear correlation, as opposed to the reduced chi square, for determination of tracks shows that, for a limited set of track parameters, the linear correlation probability works better than the x2/v. For optimized parameters the x2/v selection criterion has a slightly finer resolution. However, the linear correlation can achieve nearly the same resolution involving less computer time. In general the x2/v should remain the preferred choice for accurate tracking while the linear correlation probability should be used for rapid track reconstruction suffering a 1% loss in resolution.Item Global variables of the Lambda hyperon and pi- meson production in central Au-197 + Au-197 collisions at AGS(1997) Efremov, Sergey Valentinovich; Mutchler, Gordon S.According to Quantum Chromodynamics Theory, highly compressed and heated nuclear matter should undergo a phase transition to a new state, called the Quark Gluon Plasma. These extreme conditions can probably be created in the collisions of relativistic heavy ions. We are looking for signatures of the phase transition to QGP such as enhancement of the strangeness production rates and reduction of the collective nuclear flow. The results of the invariant differential cross sections measurements for $\Lambda$ hyperon and $\pi\sp-$ meson production via track reconstruction in the Time Projection Chambers experiment BNL-AGS-E891 are presented. Comparison of our experimental data on the differential particle multiplicities for $\Lambda$ and $\pi\sp-$ with the cascade models ARC and RQMD is given. The shapes of the particles spectra indicate the strong collective expansion of nuclear matter. We employ the three dimensional expansion picture in order to parametrize the observed particle spectra and extract the flow parameters together with the mean temperature of the particle gas after the nuclear fluid freeze-out.Item Kinematic fitting of detached vertices(2007) Mattione, Paul; Mutchler, Gordon S.The eg3 experiment at the Jefferson Lab CLAS detector aims to determine the existence of the &Xgr;5 pentaquarks and investigate the excited &Xgr; states. Specifically, the exotic X--5 pentaquark will be sought by first reconstructing the X- particle through its weak decays, X- → pi- and &Lgr; → ppi -. A kinematic fitting routine was developed to reconstruct the detached vertices of these decays, where confidence level cuts on the fits are used to remove background events. Prior to fitting these decays, the exclusive reaction gammaD→ pppi- was studied in order to correct the track measurements and covariance matrices of the charged particles. The &Lgr; → ppi- and xi- → pi -&Lgr; decays were then investigated to demonstrate that the kinematic fitting routine reconstructs the decaying particles and their detached vertices correctly.Item Laser optical pumping of atomic beams(1985) Hammond, Mark Stuart; Dunning, F. Barry; Walters, G. King; Mutchler, Gordon S.Beams of heavy rare gas metastable atoms with a high degree of polarization have been produced by optical pumping using a variety of dye laser systems. Argon (Pa) metastable atoms were efficiently polarized. but frequency instabilities in the output of the simple, multimode Ozazine 75 dye laser used prevented stable, long-term polarizations from being achieved. Stable optical pumping of a Ne (P3) beam was achieved using a similar DCM dye laser. Frequency jitter due to low dye viscosity essentially broadened the narrow spectral components of the laser lineshape. allowing a large degree of polarization to be obtained for long periods of time. In order to insure controllable and reliable performance in the optical pumping of rare gas metastable atom beams, a frequency modulation technique has been developed. By creating sidebands between laser cavity modes. frequency modulation creates a broad qua si-continuous frequency spectrum. The negative effects of frequency drifts are thus eliminated by spreading radiation across the overall laser linewidth. A frequency modulated LD 7 dye laser was used to successfully polarize an argon metastable atom beam. High polarizations were routinely obtained for periods of several hours. The technique is suitable for use in optically pumping a wide variety of atomic species for the study of electron spin and orbital orientation dependencies in many collision processes.Item Metastable atom de-excitation spectroscopy: a new probe of surface magnetism(1985) Hart, Mark Whitney; Dunning, F. Barry; Walters, G. King; Mutchler, Gordon S.Item Particle identification by TOF for heavy ion interactions(1990) Chiou, Chengnan; Mutchler, Gordon S.The purpose of the relativistic heavy-ion experiment E810 at the Brookhaven National Laboratory Alternating Gradient Synchrotron(BNL AGS) is to look for indications of a phase transition from hadronic to quark matter: the Quark-Gluon Plasma(QGP). The experiment was performed using a 14.5 $\times$ A Gev/c silicon beam from the BNL AGS to bombard targets of Si, Cu, Sn, Au, and Pb. The experimental apparatus used in the June 1989 run were the BNL Multi-Particle Spectrometer(MPS), the Time Projection Chamber(TPC) system, and the Time-of-Flight(TOF) hodoscope. With a 15m flight path, to separate $\pi\sp-$ from p up to 5-6 Gev/c and $\pi\sp-$ from $k\sp-$ up to 2.5-3 Gev/c, we require that the Root-Mean-Square(RMS) time resolution of the TOF hodoscope be about 150 picoseconds. From the analysis of the TOF beta distribution of fast $\pi\sp-$, a RMS time resolution range of 150-160 ps can be achieved after the time-walk correction.Item Radiative decays of low-lying excited-state hyperons(2000) Taylor, Simon John; Mutchler, Gordon S.The quark wave-functions of the lower-lying excited-state hyperons Λ(1405), Λ(1385), and Λ(1520) are not well understood. For example, the Λ(1405) may not be a regular three-quark state but K¯N molecule. Several competing models have been proposed, but none have been convincingly eliminated. Measuring radiative decays provides a means of discriminating between the models. The radiative branching ratios are predicted to be small (∼1%), but the radiative widths vary by factors of 2--10 from model to model. The existing experimental data is sparse and inconsistent; moreover, the radiative decay of the Sigma(1385) has never been observed before (except for one event). These lower-lying excited-state hyperons were produced in a tagged photon-beam experiment in the CLAS detector at TJNAF in the reaction gammap → K+Y* for photon energies from threshold to 2.4 GeV. The radiative branching ratio for the Sigma0(1385) relative to the Sigma0(1385) → Sigmapi0 channel was measured to be 0.021 +/- 0.008+0.004-0.007 corresponding to a partial width of 640 +/- 270+130-220 keV.Item Scintillation detector development for the solenoidal tracker at RHIC (STAR) and the CEBAF large acceptance spectrometer (CLAS)(1996) Taylor, Simon John; Mutchler, Gordon S.After a brief introduction describing some of the physics and mechanics of scintillation detection, results of the development for the Central Trigger Barrel (CTB) for STAR and the Start Counter for CLAS are discussed. For the CTB development, 1 cm x 20 cm x 100 cm scintillators were studied with light guides of various geometries and materials attached to one end in order to optimize the uniformity and overall gain. The best results were obtained using a 61$\sp\circ$ OP-1 light guide attached to a BC 408 scintillator. An alternate approach using a wavelength shifter produces much lower pulse heights than the other method. The CEBAF scintillators are intended to enclose the target area in order to identify the beam bucket for a particular event with timing resolution of 350 ps or less. Single paddle and coupled-paddle approaches are discussed. The coupled-paddle approach meets the design goals.Item Search for evidence of photoproduction of higher-twist QCD events at Experiment 683 at Fermi National Accelerator Laboratory(1996) Traynor, Michael; Mutchler, Gordon S.Experiment 683 at Fermilab Wide Band Photon Laboratory observed events via $\gamma\rm p\to$ jets during the 1991-1992 fixed target run. The present analysis attempted to observe the higher-twist subprocess in QCD using that data to measure the p$\sb{\perp}$ spectrum via a clustering algorithm tuned to optimize the distinctive topology of higher-twist events. Results indicate a substantial k$\sb{\perp}$ promotion effect at lower p$\sb{\perp}$ and a significant NLO contribution to the photoproduction.Item State-changing in Rb(Ns, Np, Nd)-Xenon collisions(1984) Goeller, Lawrence Nelson; Stebbings, Ronald F.; Dunning, F. Barry; Mutchler, Gordon S.A crossed atomic beam/pulsed laser technique and electric field ionization are used to study Rb(nS,nP,nD)-Xe collisions for 27 =< n =< 7. Parent nS, nP, nD atoms are most often destroyed by mixing to the states of high-1 that lie nearest in energy to the parent level. The 1-mixed population is monitored at several specific times after laser fire and the data are fit to a. rate equation to determine the rate constants for state changing. At higher values of n, the data approach agreement with theoretical models involving the Born Approximation and information determined from free-electron scattering cross-sections. Discrepancies between theory and experiment at lower n can be partially explained by considering the relatively large energy separations between the initial and final states, although it may be necessary to consider the relation of initial- and final-state wavefunctions as well. Present results are compared to other experimental data.Item Theory of single pion production in nucleon-nucleon scattering(1981) Umland, Eric Alexander; Duck, Ian M.; Baker, Stephen D.; Mutchler, Gordon S.We have developed a phenomenological theory for the reaction NN+NNir based on the peripheral model and the formation and decay of dibaryon resonances. The peripheral graphs include one pion exchange with a monopole form factor at the TTNN vertex and the full TTN elastic scattering amplitude obtained from phase shift analyses and including off-shell corrections. Interfering with the one pion exchange graphs are one rho exchange graphs. Similiar monopole form factors are included at the pNN and pNA vertices. All form factors possess one adjustable parameter. We also study effects due to the still speculative J = 3~ and 2+ dibaryon resonances. The highly inelastic nature of these objects suggests that a single pion production reaction of the form NN+R+NA+NNTr presents the best opportunity for observing dibaryon manifestations. We calculated the fifth order spin dependent differential cross sections d+ (beam polarized up) and cr (beam polarized down) and the asymmetry (c+-c)/(a +). The peripheral model alone gives generally poor agreement with the kinematically-complete, beam polarized data of Hancock. Inclusion of the diproton amplitudes results in a general improvement in the fits, supporting the notion of such resonances in the 3 and 1D2 partial waves of the NN channel.