R-3 Repository :: Browsing by Author "Corcoran, Marjorie D."

Browsing by Author "Corcoran, Marjorie D."

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A 200 MeV proton spin polarimeter
(1983) Rice, James Allen; Roberts, Jabus B.; Corcoran, Marjorie D.; Huang, Huey W.
The design, construction, and calibration of a 2 MeV proton spin polarimeter are described. This polarimeter monitors the beam at the transfer point between the linear accelerator and the Alternating Gradient Synchrotron at Brookhaven National Laboratory. The polarimeter determines the beam polarization to an accuracy of 1% in less than ten minutes real time, for the anticipated beam current and pulse repetition rate of the polarized beam, with a carbon filament target that intercepts 1% of the beam particles. Scattered beam particles are collected at 12 and 16 degrees to determine left-right and up-down asymmetries and detect beam angle deviations.
A search for the lightest supersymmetric partner of the top quark at DO
(2010) Mackin, Dennis S., Jr; Corcoran, Marjorie D.
We report the result of a search for the pair production of the light supersymmetric partner of the top quark (t˜1) in 5.4+/-0.3 fb-1 of data from the DO detector at a pp¯ center-of-mass energy of 1.96 TeV at the Fermilab Tevatron collider. The scalar top quarks are assumed to decay into a b quark, a charged lepton and a scalar neutrino ( n&d5; ), and the search is performed in the electron plus muon final state. No significant excess of events above the standard model prediction is detected and new exclusion limits at the 95% C.L. are set for a portion of the ( mt&d5;1,m n&d5; ) mass plane.
Calibration of the E683 main calorimeter (electromagnetic hadronic calorimeter)
(1993) Morrow, Gregory P.; Corcoran, Marjorie D.
The calibration of an electromagnetic-hadronic calorimeter is discussed in the larger context of the physics goals of the experiment in which it was used. Descriptions of the experimental apparatus are given. The methods employed for balancing electromagnetic response are discussed, including cuts on data integrity and fiducial cuts on energy distributions, and the reliability of the balancing algorithm. Results for energy resolution are given and are found to be in reasonable agreement with expectation. Extension of these balancing methods to hadronic response is discussed along with preliminary results. The ratio of hadronic to electromagnetic response is considered and is found to be in reasonable agreement with expectation. Methods of measuring and correcting for the calorimeter's evolution through time are briefly discussed.
Collisions involving XE(nf) Rydberg atoms: mℓ [enclosed by vertical lines]--changing and the influence of an external electric field
(1982) Slusher, Morgan Paul; Dunning, F. Barry; Stebbings, Ronald F.; Corcoran, Marjorie D.
Thermal energy collisions between xenon Rydberg atoms in n = 31, l > 3 states and CO2 are reported. The rate constant is derived for those collisions that result in a change in m^l. The value so obtained is similar to that obtained previously for Xe(nf) - CO2 collisions that result in a change in l. It is argued that these observations imply that collisions result in simultaneous changes in l and m^l. In addition, the influence of an applied electric field on state-changing in collisions between laser-excited Xe(nf) atoms and xenon target gas is described. The presence of the field- results in marked changes in both the rate constant for collisional state-changing and in the final state distribution. The changes can be accounted for by use of energy transfer arguments based on the "essentially-free" electron model, although the degree of spatial overlap between wavefunctions associated with the initial and final states may also be important.
Design and construction of a beam calorimeter for E683 at FNAL
(1990) Lincoln, Don; Corcoran, Marjorie D.
A steel-scintillator calorimeter has been designed to be used in a 250 GeV photon beam, and consists of approximately 10 nuclear absorption lengths of steel. Its sampling frequency is 1.5" and the sampling medium is 1/4" Kyowa SCSN-61T polystyrene based scintillator. Y7 Kyowa WLS was used to collect light into 8 Hamamatsu R2154 photomultipliers. A monitoring system has been built for the calorimeter. A LSI UV laser pumps a sample of SCSN-61T, which emits light that is subsequently shifted by Y7 and transported to the PM's via jacketted 1 mm acrylic fibers. It simulates the passage of a charged particle. A PIN photodiode also monitors the light output, for cross reference with the PM's. Interspersed among the steel and scintillator, there are 6 PWC's whose purpose is to discriminate between electromagnetic and hadronic showers. Some position information can be gathered. The PWC inter-wire spacing is approximately 1 cm. (Abstract shortened with permission of author.)
Design and construction of a photon shower position detector
(1993) Xu, Jianping; Corcoran, Marjorie D.
The design and tests of a photon shower position detector are discussed in this thesis. Some Monte Carlo results about this detector are also discussed. It will be used to measure the shower position of photons so that single $\gamma$ QED events can be distinguished from the other kinds of events in $\gamma$p interaction. The results are encouraging. From the Monte Carlo results, the detector should do a decent job of picking up QED events. The QED event ratio will be around 40% of all events which pass our cuts. And from the offline cosmic ray test and limited online test data, the detector will function very well.
Drift chambers for KTeV
(1995) Barnes, Julius, II; Corcoran, Marjorie D.
There is much potential for reliable operation of the four large drift chambers for KTeV. In time, the problem with the loss of sense wires will be solved. These chambers will have a resolution of 100 microns per plane and play a major role in measuring the direct CP violation parameter Re($\epsilon\sp\prime/\epsilon$).
Electrostatic Energy Exchange in Shock Acceleration
(2014-04-16) Barchas, Joseph; Baring, Matthew G.; Corcoran, Marjorie D.; Foster, Matthew
Plasma shocks are very common occurrences, and diffusive shock acceleration is a simple and efficient mechanism for generating cosmic rays. A shock's main effect is turbulent dissipation, which rapidly thermalizes the downstream plasma. Diffusive shock acceleration produces a non-thermal component to the particle distributions (quasi-power-law tails) which translates to non-thermal photon spectra, as seen in supernova remnants, jets in active galactic nuclei, and gamma-ray bursts. In supernova remnants, X-ray observations show that inferred proton temperatures are considerably cooler than standard shock heating predicts. A cross-shock electrostatic potential, akin to a double layer, is reasoned to exist in certain conditions due to the different inertial gyration scales of the plasma species. It provides a mechanism for energy exchange between species, and should result in a respective heating/cooling of the electrons/ions. It modifies the electron/ion distributions, which couple through radiative processes to the observed X-ray emission. In this thesis, the effects of cross-shock electrostatics are explored using a Monte Carlo simulation, where test particles gyrate and stochastically diffuse in a background fluid pre-defined by MHD jump conditions.A cross-shock electric field is derived from the steady-state spatial distribution of particles via a modified Poisson's equation that includes Debye screening, and the simulation is rerun with this field superimposed on the background magnetic and drift electric fields. This feedback loop continues until a self-consistent solution is obtained. Results show a significant departure of the particle distributions from the usual thermal+power-law form, and clearly demonstrates substantial energy exchange between the electron and ion populations.
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.
Experimental observation of the photon structure function at 21 GeV
(1998) Morrow, Gregory Peter; Corcoran, Marjorie D.
The triggered photon structure function at center-of-mass energy 21 GeV is measured from the interaction $\gamma$p $\to$ jets. Descriptions of the experimental apparatuses are given and the physics goals of the experiment are discussed. The methods used to calculate the photon structure function $x\sb{\gamma}$ are discussed in detail, with particular attention given to Monte Carlo simulation. The energy of the photon beam is carefully analyzed and methods of understanding and compensating for multiple bremsstrahlung photons, among other beam effects, are determined. Results from experimental data are compared with theoretical predictions from both leading-order and next-to-leading-order calculations and with the results of another experiment. Some examination of other targets and other beam energies is made. We observe substantial disagreement between data and lowest order Monte Carlo. Experimental results are more consistent with NLO calculations. No experimental separation of direct and resolved photons is observed or predicted by calculation.
KTeV E799II search for the lepton-flavor-number violating decay kaon(long) going to neutral pion charged muon charged electron
(2000) Bellavance, Angela M.; Corcoran, Marjorie D.
Experiments E799 Phase-II (E799II) and E832 of the Kaons at the TeVatron (KTeV) project at the Fermi National Accelerator Laboratory (Fermilab), are in the process of studying rare and CP-violating kaon decays. The experiment ran during 1996 and 1997, and the resulting data are being analyzed. This study focuses on the E7991I search for the decay mode KL→p0m+/- e∓ , and its accompanying background decays, in approximately 60% of the 1996--7 KTeV data.
Missing Energy Studies at the DØ Experiment
(2013-07-24) Hogan, Julie; Corcoran, Marjorie D.; Baring, Matthew G.; Geurts, Frank
Missing transverse energy is an important aspect of physics analyses at hadron collider detectors. While other particles can be identified by the energy they deposit in the detector, the presence of neutrinos and other theorized particles must be inferred by an energy imbalance. At the DØ experiment missing energy algorithms exist not only to calculate the missing energy in an event, but to distinguish between possible sources: detector measurement effects or unobserved particles. DØ scientists rely on these algorithms to produce reliable physics results. This thesis presents updates made in the past year to missing energy certification, the unclustered energy resolution, and the missing energy significance calculation. It describes a new processor which calculates missing momentum from tracks as well as development work toward an unclustered energy calibration.
Monte Carlo study of multiple hard scattering effects in proton-nucleus interactions at high transverse energies
(1985) Hage, George; Duck, Ian M.; Phillips, Gerald C.; Corcoran, Marjorie D.
All experimental data for proton-nucleus collisions at ultrarelativistic energies confirms the "Anomalous nuclear enhancement" phenomena, which gives a cross section dependence upon the atomic number A as oPA = oppA^a with a greater than 1. This power law dependence cannot be explained by QCD parton-models if only a single proton-nucleon hard collision is assumed, for then a power of 1 would emerge. The effect of multiple-hard scattering of partons inside the nucleus is studied in this thesis. E^T cross sections and other variables, such as planarity and multiplicity, are studied within the multiple scattering model using Monte Carlo techniques. The results are compared with data for two different un-biased triggers, the global trigger and the two-high trigger. Judgments on the importance of multiple scattering are made.
Multivariate search for the lightest Supersymmetric partner of the top quark
(2008) Mackin, Dennis S., Jr.; Corcoran, Marjorie D.
We apply the PDE multivariate event classifier to the search for the Supersymmetric parter of the top quark in the two muon channel at D∅ and compare the results to the results of a recently completed conventional analysis. An automated, customizable method for searching for a signal may enable searching through a much larger portion of the Supersymmetry parameter space and may also increase signal sensitivity. We show that an automated process based on the PDE method is capable of achieving signal sensitivity similar to that obtained by conventional analysis methods.
Muon spin relaxation in a random ferromagnet: PdMn
(1983) Gist, Grant Alan; Dodds, Stanley A.; Hannon, James P.; Corcoran, Marjorie D.
Muon spin relaxation (ySR) experiments have been performed in transverse, longitudinal and zero applied field on the disordered ferromagnet PdMn (2.3 at.%). Muon relaxation rates in the paramagnetic phase are in good agreement with predictions of the Walstedt-Walker formula, and appear to have no contribution from muon coupling to the giant moment polarization cloud. The transverse field relaxation rate (yT) and the width of x the zero field quasistatic field distribution (a(T)) in the ferromagnetic phase are less than calculated from a uniform mean field model. This "shortfall" is found to be qualitatively consistent with the Sherrington-Kirkpatrick disordered mean field theory. Spin-lattice relaxation rates in zero applied field give clear evidence for critical slowing down of Mn spin fluctuations over a wide temperature range, and are consistent at low temperatures with a two magnon Raman scattering mechanism.
Observation of jet photoproduction and comparison to Monte Carlo simulation
(1994) Lincoln, Donald W.; Corcoran, Marjorie D.
The photon is the carrier of the electromagnetic force. However in addition to its well known nature, the theories of QCD and quantum mechanics would indicate that the photon can also for brief periods of time split into a $q\overline{q}$ pair (an extended photon). How these constituents share energy and momentum is an interesting question and such a measurement was investigated by scattering photons off protons. The post collision kinematics should reveal pre-collision information. Unfortunately, when these constituents exit the collision point, they undergo subsequent interactions (gluon radiation, fragmentation, etc.) which scramble their kinematics. An algorithm was explored which was shown via Monte Carlo techniques to partially disentangle these post collision interactions and reveal the collision kinematics. The presence or absence of large transverse momenta internal ($k\sb\bot$) to the photon has a significant impact on the ability to reconstruct the kinematics of the leading order calculation hard scatter system. Reconstruction of the next to leading order high $E\sb\bot$ partons is more straightforward. Since the photon exhibits this unusual behavior only part of the time, many of the collisions recorded will be with a non-extended (or direct) photon. Unless a method for culling only the extended photons out can be invented, this contamination of direct photons must be accounted for. No such culling method is currently known, and so any measurement will necessarily contain both photon types. Theoretical predictions using Monte Carlo methods are compared with the data and are found to reproduce many experimentally measured distributions quite well. Overall the LUND Monte Carlo reproduces the data better than the HERWIG Monte Carlo. As expected at low jet $E\sb\bot$, the data set seems to be dominated by extended photons, with the mix becoming nearly equal at Jet $E\sb\bot$ $>$ 4 GeV. The existence of a large photon $k\sb\bot$ appears to be favored.
Occupancy Study of the CMS Pixel Subdetector for the Phase 1 Upgrade
(2013-08-15) Zabel, James; Ecklund, Karl M; Corcoran, Marjorie D.; Nevidomskyy, Andriy
The Phase 1 Upgrade for CMS includes the installation of a new pixel subdetector, complete with newly designed readout chips as well as a new geometry. This upgrade is necessary to replace the existing irradiated pixel subdetector with one designed for higher instantaneous luminosities. It also provides an opportunity to improve the resolution of track reconstruction and vertex isolation. The new geometry and higher beam energies available after the upgrade increase the flux of ionizing radiation traveling through the pixel subdetector. Results of a simulation that estimate pixel hits, and thus provide an opportunity to estimate data rates and flux, will be shown. The simulation incorporates a variety of factors affecting the estimated data rates and flux, including various luminosities, bunch spacings, and beam spot locations. The simulation determines the number of data links per module necessary to maintain data rates within design limitations.
Operation and efficiency of the DO Central Track Trigger
(2005) Cooke, Michael P.; Corcoran, Marjorie D.
The Central Track Trigger (CTT), a subsystem of the DO collider detector at Fermilab, plays a key role in selecting which of the 1.7 million proton-antiproton beam crossing events are written to permanent storage. In order to provide constant monitoring of this triggering process, a software package, the CTT Examine, was created. This monitoring program provides useful immediate feedback about the output of the CTT and allows control room operators to diagnose many problems that might otherwise compromise data quality. The performance of the CTT is also directly tested by examining Z → ee events. The global efficiency of the CTT for finding high transverse momentum (pT) tracks in the run range [151831, 178310), taken between April 20th, 2002 and June 24th, 2003, is found to be 85.1 +/- 1.0%. The efficiency of the CTT with respect to offiine reconstructed tracks is 91.3 +/- 1.0%.
Operation of the run IIB DO luminosity system and determination of the run IIB luminosity constant
(2010) Prewitt, Michelle V.; Corcoran, Marjorie D.
The luminosity system is an integral part of the DO detector that must be properly maintained to provide accurate luminosity measurements for physics analysis. After the addition of a readout layer to the silicon vertex detector in 2006, it was necessary to re-calculate the effective inelastic cross section to which the luminosity monitor is sensitive. The preliminary analysis showed that the luminosity constant did not change with the addition of the extra layer of silicon. A full study of the revised luminosity constant including a complete analysis of systematic uncertainties has been completed. The luminosity constant was determined to be sigmaeff = 48.3 +/- 1.9 +/- 0.6 mb, which reduces the DO contribution to the luminosity measurement uncertainty by almost 3%.
Production of jets from proton-nucleus collisions at 400 GeV/c
(1989) Moore, Robert Christopher; Corcoran, Marjorie D.
Jets produced in high transverse energy proton-nucleus collisions at 400 GeV/c were recorded in a calorimeter study at Fermilab. The jets were identified with two different jet-finding algorithms; the results from the two algorithms agree. For the eight nuclear targets with atomic number, A, ranging from 1 to 207 (H$\sb2$, He, Be, C, Al, Cu, Sn and Pb), the cross section increases as A$\sp{1.35\pm0.01}$ over mean jet pair transverse momentum of 4 to 8 GeV/c. The enhancement, however, depends on the class of jets selected; for example the cross section increases as A$\sp1$ for highly planar high-transverse-momentum jet events and as A$\sp{1.65}$ for non-planar high-transverse-momentum events. Jet properties were studied as a function of jet transverse momentum and A. In general as A increases, the number of particles in the jets increases while their collimation and coplanarity decrease. Also with increasing A, the proton transfers more of its energy into the target fragmentation region instead of the forward or central regions. Multiple scattering models describe nuclear enhancement, however fits to our data require negative coefficients in the higher order terms of the expansion, presenting a challenge to simple multiple scattering models.

Browsing by Author "Corcoran, Marjorie D."

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