188 Matching Results

Search Results

Advanced search parameters have been applied.

The dijet mass spectrum at D-Zero

Description: We present preliminary results from an analysis of jet data collected during the 1994-95 Tevatron Collider run with an integrated luminosity of 93 pb{sup -1}. Measurements of dijet mass spectra in {anti p}p collisions at {radical}s = 1.8 TeV are compared to next-to-leading order QCD calculations.
Date: November 1, 1997
Creator: Abbott, B.
Partner: UNT Libraries Government Documents Department

Single top production and M{subscriptT Tbar}

Description: Single top production provides opportunities for studying the charged-current weak interaction of the top quark. The t{anti t} invariant mass spectrum M{sub t{anti t}} enables the search for non-standard model t{anti t} resonance states. These two topics have motivated new developments in top quark related analyses at Fermilab Tevatron. This presenta- tion reports the current single top and M{sub t{anti t}} analysis methods and the corresponding results from the collider Run I data collected by the CDF and D#31; experiment. We conclude with the prospects for these studies in the upcoming collider Run II.
Date: May 11, 1999
Creator: Liu, Yi-Cheng
Partner: UNT Libraries Government Documents Department

The experimental investigation of supersymmetry breaking

Description: If Nature is supersymmetric at the weak interaction scale, what can we hope to learn from experiments on supersymmetric particles? The most mysterious aspect of phenomenological supersymmetry is the mechanism of spontaneous supersymmetry breaking. This mechanism ties the observable pattern of supersymmetric particle masses to aspects of the underlying unified theory at very small distance scales. In this article, I will discuss a systematic experimental program to determine the mechanism of supersymmetry breaking. Both pp and e{sup +}e{sup -} colliders of the next generation play an essential role.
Date: April 1, 1996
Creator: Peskin, M.E.
Partner: UNT Libraries Government Documents Department

b {r_arrow} sl{sup +}l{sup {minus}} in the left-right symmetric model

Description: We begin to analyze and contrast the predictions for the decay b {r_arrow} sl{sup +}l{sup {minus}} in the Left-Right Symmetric Model (LMR) with those of the Standard Model (SM). In particular, we show that the forward-backward asymmetry of the lepton spectrum can be used to distinguish the SM from the simplest manifestation of the LRM.
Date: May 1, 1997
Creator: Rizzo, T.G.
Partner: UNT Libraries Government Documents Department

Measurement of the top quark mass and kinematic properties with the D0 detector

Description: We review D0`s analysis of the top quark mass based on approximately 50 pb{sup -1} of lepton + jets data. Preliminary results are presented on kinematic properties of these events, including a study of the two-dimensional distributions of reconstructed top mass vs. dijet mass. In addition, a preliminary mass analysis in the dilepton channels is presented.
Date: October 1, 1995
Creator: Snyder, S.
Partner: UNT Libraries Government Documents Department

The dijet mass cross section at the Tevatron

Description: We present recent results on dijet production in p{anti p} collisions at {radical}s = 1.8 TeV at the Fermilab Tevatron. Data from both CDF and D0 experiments are shown. Dijet measurements complement prior inclusive jet measurements, which have shown a possible excess above expectations at high transverse energy. The same trend is seen in the dijet mass spectra.
Date: May 11, 1999
Creator: Hauser, J.
Partner: UNT Libraries Government Documents Department

LSND, SN1987A, and CPT violation

Description: We point out that neutrino events observed at Kamiokande andIMB from SN1987A disfavor the neutrino oscillation parameters preferredby the LSND experiment. For Delta m2>0 (the light side), theelectron neutrinos from the neutronization burst would be lost, while thefirst event at Kamiokande is quite likely to be due to an electronneutrino. For Delta m2<0 (the dark side), the average energy of thedominantly bar nu e events is already lower than the theoreticalexpectations, which would get aggravated by a complete conversion frombar nu mu to bar nu e. If taken seriously, the LSND data are disfavoredindependent of the existence of a sterile neutrino. A possible remedy isCPT violation, which allows different mass spectra for neutrinos andanti-neutrinos and hence can accommodate atmospheric, solar and LSND datawithout a sterile neutrino. If this is the case, Mini-BooNE must run inbar nu rather than the planned nu mode to test the LSND signal. Wespeculate on a possible origin of CPT violation.
Date: October 17, 2000
Creator: Murayama, Hitoshi & Yanagida, T.
Partner: UNT Libraries Government Documents Department

PREPARATION OF OXOPORPHINATOMANGANESE (IV) COMPLEX

Description: Oxo-manganese-tetraphenylporphyrin (O=Mn{sup IV}-TPP) has been prepared by an oxygen-transfer reaction from iodosylbenzene to MnIITPP and characterized by its i.r. and field desorption mass spectra, which are identical to those of the product obtained by direct oxidation of Mn{sup III}(TPP) in an aqueous medium; it transfers oxygen to triphenylphosphine to produce triphenylphosphine oxide, and it is suggested that similar intermediates are important in oxygen activation by cytochrome P-450 as well as in the photosynthetic evolution of oxygen.
Date: July 1, 1980
Creator: Willner, I.; Otvos, J. & Calvin, M.
Partner: UNT Libraries Government Documents Department

Complete chemical analysis of aerosol particles in real-time

Description: Real-time mass spectrometry of individual aerosol particles using an ion trap mass spectrometer is described. The microparticles are sampled directly from the air by a particle inlet system into the vacuum chamber. An incoming particle is detected as it passes through two CW laser beams and a pulsed laser is triggered to intercept the particle for laser ablation ionization at the center of the ion trap. The produced ions are analyzed by the ion trap mass spectrometer. Ions of interest are selected and dissociated through collision with buffer gas atoms for further fragmentation analysis. Real-time chemical analyses of inorganic, organic, and bacterial aerosol articles have been demonstrated. It has been confirmed that the velocity and the size of the incoming particles highly correlate to each other. The performance of the inlet system, particle detection, and preliminary results are discussed.
Date: December 31, 1996
Creator: Yang, Mo; Reilly, P.T.A.; Gieray, R.A.; Whitten, W.B. & Ramsey, J.M.
Partner: UNT Libraries Government Documents Department

B {r_arrow} X{sub u} {ell} {bar {nu}}{sub {ell}} decay distributions to order {alpha}{sub s}

Description: An analytic result for the O({alpha}{sub s}) corrections to the triple differential B {r_arrow} X{sub u} {ell} {bar {nu}}{sub {ell}} decay rate is presented, to leading order in the heavy-quark expansion. This is relevant for computing partially integrated decay distributions with arbitrary cuts on kinematic variables. Several double and single differential distributions are derived, most of which generalize known results. In particular, an analytic result for the O({alpha}{sub s}) corrections to the hadronic invariant mass spectrum is presented. The effects of Fermi motion, which are important for the description of decay spectra close to infrared sensitive regions, are included. The behavior of perturbation theory in the region of time-like momenta is also investigated.
Date: May 17, 1999
Creator: Neubert, Matthias
Partner: UNT Libraries Government Documents Department

Masses of orbitally excited baryons in large N{sub c} QCD

Description: The authors present the first phenomenological study of the masses of orbitally excited baryons in large N{sub c} QCD. Restricting here to the nonstrange sector of the L=1 baryons, the 1/N{sub c} expansion is used to order and select a basis of effective operators that spans the nine observables (seven masses and two mixing angles). Fits are performed using subsets of the complete set of nine operators, including corrections up to O(1/N{sub c}) where leading order is N{sub c}{sup 1}. This study shows that the 1/N{sub c} expansion provides an excellent framework for analyzing the mass spectrum, and uncovers a new hierarchy of operator contributions.
Date: July 1, 1998
Creator: Carlson, Carl E.; Carone, Christopher D.; Goity, Jose' L. & Lebed, Richard F.
Partner: UNT Libraries Government Documents Department

Are partons confined tachyons?

Description: The author notes that if hadrons are gravitationally stabilized ``black holes``, as discrete physics suggests, it is possible that partons, and in particular quarks, could be modeled as tachyons, i.e. particles having v{sup 2} > c{sup 2}, without conflict with the observational fact that neither quarks nor tachyons have appeared as ``free particles``. Some consequences of this model are explored.
Date: March 1, 1996
Creator: Noyes, H.P.
Partner: UNT Libraries Government Documents Department

Excited charmed mesons

Description: The experimental status of excited charmed mesons is reviewed and is compared to theoretical expectations. Six states have been observed and their properties are consistent with those predicted for excited charmed states with orbital angular momentum equal to one.
Date: May 1, 1995
Creator: Butler, J.N. & Shukla, S.
Partner: UNT Libraries Government Documents Department

Recent top quark physics results at the Tevatron

Description: The evidence of top quark pair production in pp collisions has been firmly established by both the CDF and the D{O} collaborations at Fermilab. In this paper the latest top quark physics results from both experiments at the Tevatron Collider are presented. The experimental analyses have concentrated in improving the accuracy of top quark production and decay measurements like cross sections, mass and, branching fractions. The results shown correspond to the final data set collected with both detectors during the complete Tevatron Run L. This represents a total recorded integrated luminosity of {approximately}110 pb{sup -1} for CDF and {approximately}100 pb{sup -1} for D{O}.
Date: July 1, 1996
Creator: Valls, J.A.
Partner: UNT Libraries Government Documents Department

D0 top analyses: Recent results on the properties of the sixth quark

Description: The D0 collaboration updates measurements of the Standard Model top quark in pp collisions at {radical}s = 1.8 TeV at the Fermilab Tevatron, with a new data sample of approximately twice the integrated luminosity used for the discovery measurements ({approximately}100 pb{sup -1}). We observe 37 t{bar t} candidate events from seven decay modes with an expected background of 13.4 {+-} 3.0 events. We present a preliminary new top mass measurement of 170 {+-} 15 (stat.) {+-}10 (syst.) GeV/c{sup 2} using the single-lepton + jets decay modes. For the central value of our measured mass we calculate the production cross section to be 5.2 {+-} 1.8 pb. D{O} is also analyzing additional decay modes and we report preliminary results from two new channels.
Date: June 1, 1996
Creator: Hall, R. E.
Partner: UNT Libraries Government Documents Department

Multi-strange baryon production in Au+Au collisions at {radical}s{sub NN} = 130 GeV

Description: The transverse mass spectra and mid-rapidity yields for {Xi}s and {Omega}s plus their anti-particles are presented. The 10% most central collision yields suggest that the amount of multi-strange particles produced per produced charged hadron increases from SPS to RHIC energies. A hydrodynamically inspired model fit to the spectra, which assumes a thermalized source, seems to indicate that these multi-strange particles experience a significant transverse flow effect, but are emitted when the system is hotter and the flow is smaller than values obtained from a combined fit to {pi}, K, p and {lambda}s.
Date: July 30, 2003
Creator: Adams, J.; Adler, C.; Aggarwal, M.M.; Ahammed, Z.; Amonett, J.; Anderson, B.D. et al.
Partner: UNT Libraries Government Documents Department

A production in Au-Au collisions at the AGS

Description: The results of a measurement of production in Au-Au collisions at 11.6 A GeV/c by Experiment 891 at the Brookhaven AGS are presented. The measurements cover the rapidity region of 2.0 to 3.2 and transverse momenta of 0.0 to 1.4 GeV/c. The results are compared with similar measurements of Si-Si interactions and the predictions of ARC and RQMD models.
Date: December 31, 1996
Creator: Saulys, A.C.; Eiseman, S.E. & Foley, K.J.
Partner: UNT Libraries Government Documents Department

Quasi-degenerate neutrinos from an abelian family symmetry

Description: The authors show that models with an abelian family symmetry which accounts for the observed hierarchies of masses and mixings in the quark sector may also accommodate quasi-degeneracies in the neutrino mass spectrum. Such approximate degeneracies are, in this context, associated with large mixing angles. The parameters of this class of models are constrained. The authors discuss their phenomenological implications for present and foreseen neutrino experiments.
Date: December 31, 1996
Creator: Binetruy, P.; Lavignac, S.; Petcov, S. & Ramond, P.
Partner: UNT Libraries Government Documents Department

Search for the decay B{sup 0} {yields} {mu}{sup +}{mu}{sup {minus}}

Description: The authors present a search for the decays B{sub d}{sup 0} {yields} {mu}{sup +}{mu}{sup {minus}} and B{sub s}{sup 0} {yields} {mu}{sup +}{mu}{sup {minus}} using 17.8 pb{sup {minus}1} of data collected with the Collider Detector at Fermilab (CDF) during 1992--1993 data taking period. They find no B{sub d}{sup 0} candidates in a mass window of [5.205, 5.355] GeV/c{sup 2} and 1 B{sub s}{sup 0} candidate in a mass window of [5.300, 5.450] GeV/c{sup 2}. Normalizing to the measured cross-section {sigma} (B{sup +}) = 2.39 {+-} 0.54 {micro}b for p{sub t}(B) > 6 GeV/c and {vert_bar}y(B){vert_bar} < 1 and assuming {sigma}(B{sup +}) = {sigma}(B{sub d}{sup 0}) = 3{sigma}(B{sub s}{sup 0}), they find Br(B{sub d}{sup 0} {yields} {mu}{sup +}{mu}{sup {minus}}) < 1.6 {times} 10{sup {minus}6} and Br(B{sub s}{sup 0} {yields} {mu}{sup +}{mu}{sup {minus}}) < 8.4 {times} 10{sup {minus}6} at 90% confidence level. These limits are significant improvements of previous measurements.
Date: July 1, 1995
Creator: Abe, F.
Partner: UNT Libraries Government Documents Department

Multi-strange baryon production in Au-Au collisions at sqrt(sNN) = 130 GeV

Description: The transverse mass spectra and mid-rapidity yields for {Xi}s and {Omega}s plus their anti-particles are presented. The 10% most central collision yields suggest that the amount of multi-strange particles produced per produced charged hadron increases from SPS to RHIC energies. A hydrodynamically inspired model fit to the spectra, which assumes a thermalized source, seems to indicate that these multi-strange particles experience a significant transverse flow effect, but are emitted when the system is hotter and the flow is smaller than values obtained from a combined fit to {pi}, K, p and {Lambda}s.
Date: July 31, 2003
Creator: Adams, J.; Adler, C.; Aggarwal, M.M.; Ahammed, Z.; Amonett, J.; Anderson, B.D. et al.
Partner: UNT Libraries Government Documents Department

Hadronic spectra from collisions of heavy nuclei

Description: Hadronic spectra from collisions of heavy ions at ultrarelativistic energies are discussed, concentrating on recent measurements at the SPS of central Pb+Pb collisions at 158 GeV/nucleon, which are compared to collisions of lighter ions and at lower beam energies. Baryon stopping is seen to be larger for heavier systems and lower energies. Total yields of pions and kaons scale with the number of participants in central collisions at the SPS; in particular, the K/{pi} ratio is constant between central S+S and Pb+Pb at the SPS. Transverse mass spectra indicate significantly larger radial flow for the heavier systems. At midrapidity, an enhancement of <{pi}{sup {minus}}>/<{pi}{sup +}> and <K{sup {minus}}>/<K{sup +}> at low P{sub T} are best explained by final state Coulomb interaction with the residual charge of the fireball.
Date: March 1, 1997
Creator: Jacobs, P.
Partner: UNT Libraries Government Documents Department

D{O} top quark mass analysis

Description: Based on (44-48 pb{sup -1}) of lepton + jets data, we review D0`s initial analysis of the top quark mass. The result, M{sub top} = 199 {+-} 19/21 (stat.) {+-} 22 (syst.) GeV/c{sup 2}, is insensitive to background normalization. The errors are based on ISAJET top Monte Carlo, with its more severe gluon radiation, and allow for ISAJET/HERWIG differences. Good progress is being made in reducing the systematic error. We present a new study based on two-dimensional distributions of reconstructed top quark vs. dijet mass. With 98.7% confidence we observe a peak in the top mass - dijet mass plane. The peak and its projections are similar both in shape and magnitude to expectations based on the decay sequence 1 {yields} bW, W {yields} jj.
Date: July 1, 1995
Creator: Strovink, M.
Partner: UNT Libraries Government Documents Department