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H{sub 0} candidates from the decays {Sigma}{sup {minus}}p and {Lambda}p{pi}{sup {minus}}, produced in heavy ion collisions Si beam on Pb target

Description: There is considerable interest in searching for strange quark matter (strangelets). The lowest strangelet state is thought to be a six quark dibaryon singlet spin zero state called the H{sub 0} predicted by R.L. Jaffe. The authors present H{sub 0} candidate events, where H{sub 0}(2210) is observed through the weak decay modes {Sigma}{sup {minus}}p and {Lambda}p{pi}{sup {minus}}, produced in central heavy ion collisions with 14.6 x A Gev/c Si beam on Pb target. The lifetime is consistent with {approximately}4 cm cr in both channels approximately 1/3 of an H{sub 0}(2210) which decays into {Sigma}{sup {minus}} p is produced per central Si Pb collision. The branching ratio between {Lambda}p{pi}{sup {minus}} and {Sigma}{sup {minus}}p is around 11% {+-} 3%.
Date: December 1, 1997
Creator: Longacre, R.S.
Partner: UNT Libraries Government Documents Department

Strange particle production in hadronic Z{sup 0} decays

Description: A study has been made of neutral strange baryons and pseudoscalar mesons produced in hadronic decays of the weak gauge boson V. The experiment was performed at the Stanford Linear Accelerator Center, which has the unique capability of colliding highly polarized electrons with unpolarized positrons. Overall production rates and spectra of the K{sup 0} and the {Lambda}{sup 0} (+{Lambda}{sup 0}) were measured and compared with other experiments as well as with Quantum Chromodynamics calculations. The combination of the small, stable beam spots produced by the SLAC Linear Collider (SLC) and the precision vertexing capabilities of the SLC Large Detector (SLD) permitted the separation of the hadronic events into three quark flavor-enriched samples. An unfolding was performed to obtain flavor-pure samples, and for the first time measurements were made of K{sup 0} and {Lambda}{sup 0} (+{Lambda}{sup 0}) production rates and spectra in uds, c, and b quark events at the Z{sup 0} pole. This measurement revealed significant production differences. Utilizing the large quark production asymmetry due to the polarized electron beam, high-purity quark and antiquark jet samples were obtained. The first measurement of production differences of the {Lambda}{sup 0} baryon in quark and antiquark jets was performed, which provided clear evidence for a leading particle effect at high momenta.
Date: April 1, 1996
Creator: Baird, K.G. III
Partner: UNT Libraries Government Documents Department

The Structure of the Weak Interaction $lambda$ + N $Yields$ N + N

Description: Empirical evidence on the nonmesic decay of LAMBDA hypernuclei is analyzed in terms of the spin and isospin dependence of the weak interactions A + p yields n + p and LAMBDA + n yields n + n. The nonmesic decay rates for / sub LAMBDA /He/sup 4/ and /sub LAMBDA /H/sup 4/ were obtained by treating the A de-excitation by different nucleons as incoherent and assuming the validity of the DELTA I = 1/2 selection rule for these interactions. The ratios of nonmesic to pi /sup -/ decay modes and of the first reaction to the second were calculated as 1.68 plus or minus 0.36 and 0.5, respectively, for He/sup 6/ decay. The later ratio for H/sup 4/ was predicted to be 1/(8.8 plus or minus 3.2). Interpretation of the rates is discussed, and it is concluded that if the LAMBDA I = 1/2 rule holds for the LAMBDA -N yields N-N weak interaction and if present ideas about the current-current nature of weak interactions are valid, then the higher-order mesonic corrections to this primary four-fermion interaction must mask the simplicity of their primary form. (D.C.W.)
Date: May 1, 1963
Creator: Block, M. M. & Dalitz, R. H.
Partner: UNT Libraries Government Documents Department

The Strong and Weak Interactions of Bound a-Particles

Description: Calculations on the S-wave LAMBDA -N and LAMBDA - LAMBDA interactions, binding energies for the p-shell hypernuclei, and the mesic decay and nonmesonic de-excitation of the A-particle are discussed. The theory behind the calculations, as well as the results and their interpretation, are considered. (D.C.W.)
Date: January 1, 1963
Creator: Dalitz, R. H.
Partner: UNT Libraries Government Documents Department

Lambda production in electron-positron annihilation at 29 GeV

Description: The inclusive cross-secton for the production of the singly-strange baryons lambda and anti lambda, along with the differential cross-sections in momentum and energy, are measured by e/sup +/e/sup -/ annihilation at a center-of-mass energy of 29GeV. The charged decay mode lambda ..-->.. p..pi.. is used in a search for polarization. Such a polarization may be used as a check of CP invariance in lambda production. The sample of events with two detected decays is analyzed for correlations in production angle. 43 refs., 44 figs.
Date: August 1, 1986
Creator: Baden, A.R.
Partner: UNT Libraries Government Documents Department

High energy physics at Tufts University. Progress report. [Summaries of research activities at Tufts University]

Description: During the year a final paper was produced on XI* production from 2.9 GeV/c K/sup -/p interactions, and a paper on the ..sigma../sup -/..pi../sup -/..pi../sup +/ (..pi../sup 0/) final state from 2.9 GeV/c K/sup -/d interactions is on the verge of completion. From our 14.75 GeV/c anti pp experiment results have been prepared for publication on three topics: the charm search, V/sup 0/ inclusive production, and ..pi../sup 0/ production. Further analysis of data is continuing. In the 300 GeV/c pp experiment, investigations are completed or underway in three areas: neutral and charged pion correlations, inclusive ..gamma.. and V/sup 0/ production, and inclusive resonance production. Further data on inclusive V/sup 0/ distributions from 6.5 GeV/c K/sup -/p interactions has been obtained and analysis is nearing completion. A good deal of effort went into the development of proposals for new physics. These new directions may be represented by three approved experiments at three different laboratories: Neutrino-deuterium interactions at Fermilab (an approved and a proposed experiment); Search for new states decaying into anti ..lambda lambda.. and K/sup 0//sub s/K/sup 0//sub s/ using the Multiparticle Spectrometer at B.N.L. (approved in May, 1977); Search for baryonium using the SLAC hybrid bubble chamber system, which won approval in September with a recommendation for prompt running from the Program Advisory Committee. A list of publications is included.
Date: September 1, 1977
Partner: UNT Libraries Government Documents Department

K/sub L/$sup 0$p interactions at 550 MeV/c

Description: Differential and channel cross sections and hyperon polarizations are presented for the reactions K$sup 0$/sub L/p $Yields$ K$sup 0$/sub S/p, $pi$$sup +$ A$sup 0$, and $pi$$sup +$ $Sigma$$sup 0$ at an average beam momentum of 550 MeV/c. These data provide constraints on KN and anti KN amplitudes obtained from charged kaon reactions and reject one of the S = +1, I = 0 and one of the S equals -1, I = 1 phase shift solutions. (auth)
Date: January 1, 1975
Creator: Cho, Y.; Derrick, M.; Miller, R.J.; Smith, R.P.; Engler, A.; Keyes, G. et al.
Partner: UNT Libraries Government Documents Department

Experimental investigation of the production of glueballs and meson resonance states

Description: We have made striking and considerable progress in our AGS program which is searching for a Quark-Gluon Plasma or other new phenomena at the AGS. We are employing a TCP Tracking Magnetic Spectrometer that has handled up to {approx}100 tracks, the maximum observed in 14.5 GeV/c {times} A Si ions incident on Au and Cu. In essence the TPC covers more than the forward half hemisphere in the nucleon-nucleon cms (i.e. {ge} 2{pi}) and thus allows tracking, momentum and angular analysis of the charged particles emitted in these heavy ion collisions. Particle identification for negative pions can be made approximately by assuming negative particles are pions. Then by subtraction of negatives from positives in a suitable manner the proton characteristics can be determined. {Lambda} and K{sub s}{sup 0} V particles have been identified singly in events and {approx}50 double {Lambda} and 2 triple {Lambda} events have been observed in the relatively small data sample we have obtained and analyzed this year. Further discussion of these topics are contained in this report.
Date: December 19, 1990
Creator: Lindenbaum, S.J.
Partner: UNT Libraries Government Documents Department

Charmed baryon decays observed in e/sup +/e/sup -/ annihilation at SPEAR

Description: Various weak decays of the charmed baryon ..lambda../sub c/ are observed in the Mark II detector at the SLAC e/sup +/e/sup -/ storage ring SPEAR. Hadronic decays ..lambda../sub c//sup +/ ..-->.. pK/sup -/..pi../sup +/ and ..lambda../sub c//sup +/ ..-->.. pK/sub s//sup 0/ and their conjugates are observed as peaks in invariant mass spectra at m(..lambda../sub c/) = (2286 +- 6) MeV/c/sup 2/. An estimate of the charmed baryon production cross section, sigma(..lambda../sub c/) + sigma (anti ..lambda../sub c/) = (1.7 +- 0.4) nb, derived from Mark II measurements of the inclusive baryon cross sections R/sub p/ and R/sub ..lambda../ as functions of center-of-mass energy, is used to calculate branching ratios for these hadronic decays: BR (..lambda../sub c//sup +/ ..-->.. p K/sup -/ ..pi../sup +/) = (2.0 +- 0.8)%; BR (..lambda../sub c//sup +/ ..-->.. p k/sub s//sup 0/)/BR (..lambda../sub c//sup +/ ..-->.. p K/sup -/ ..pi../sup +/) = (36 +- 16)%. An attempt is also made to observe higher mass charmed baryons by reconstructing cascade decays ..sigma../sub c/ ..-->.. ..lambda../sub c/..pi... Evidence for the observation of semileptonic decays of the charmed baryon is presented. Direct electrons are observed in events containing antiprotons, lambdas and antilambdas. The number of electrons per baryon event, after background subtraction and efficiency correction, is used, together with an estimate of the charmed baryon content of proton and lambda events, to calculate inclusive and semi-inclusive semileptonic branching ratios of the ..lambda../sub c/.
Date: December 1, 1981
Creator: Vella, E.N.
Partner: UNT Libraries Government Documents Department

Strangeness-exchange and strange nuclei

Description: The nuclear strangeness exchange reaction (K/sup -/,..pi../sup -/) is discussed. Possible reaction mechanisms are reviewed, and the spectroscopic ..lambda..-hypernuclear information derived from observation of strangeness exchange is discussed. The more general question of multiply-strange nuclei is introduced. 10 figures, 1 table, 32 references.
Date: January 1, 1978
Creator: Gal, A
Partner: UNT Libraries Government Documents Department

Studies of particle interactions in bubble chamber, spark chambers and counter experiments. Annual progress report

Description: During the past six years we have carried out and planned experiments which predominantly studied the production and decay of particles containing charmed quarks. A series of photoproduction and neutron production experiments started with the very early observation of the production of J/psi by neutrons and by photons at Fermilab. From subsequent experiments using these neutral beams and the basic detecting system, we have reported results on the photoproduction of the ..lambda../sub c/ charmed baryon and the D and D* charmed mesons. More recent runs are studying the high energy photoproduction of vector mesons including the psi'. The present experiment in this sequence is using neutrons to produce a large number of D mesons. Another series of experiments at Fermilab set out to study the hadronic production of charmed mesons. The Chicago Cyclotron facility was modified with a detector sensitive to various possible production mechanisms. The experiments were a success; clean signals of D mesons were observed to be produced by pions, and also the production of chi/sub c/ with the subsequent decay via a ..gamma..-ray to psi was observed. The charmonium experiments run this year have better photon resolution for measuring the decays of chi/sub c/ to psi. We are part of a collaboration which is working on the Collider Detector Facility for Fermilab. The CDF at Fermilab is a possible source of (weak) intermediate vector bosons from the collisions of protons and anti-protons. Our responsibilities in the CDF include both the construction of the muon detector and the designing, planning, and testing of the FASTBUS electronics. The second part of our weak interaction program is the Neutrino Oscillation experiment which is now under construction at Brookhaven.
Date: July 1, 1983
Creator: Holloway, L.E.; O'Halloran, T.A. Jr. & Simmons, R.O.
Partner: UNT Libraries Government Documents Department

Annual progress report

Description: Elementary particle physics research at the University of Illinois and at high energy particle accelerator laboratories operated by DOE is described. Major accomplishments in 1980 include: determination of the diffractive cross section for production of charmed D mesons in ..pi../sup -/p collisions at 215 GeV/c to be 20 ..mu..b; data acquisition for ..pi../sup -/ beryllium at 215 GeV/c; construction and testing of prototype muon drift tubes for the p anti p detector facility; Monte Carlo studies of the muon trigger rates, background levels and resolutions were done; results of photoproduction for 70 to 200 GeV photons gave cross-sections of 160 +- 70 nb and 390 +- 190 nb per nucleon respectively; the cross-section for photoproduction of the charmed ..lambda../sub c/ baryon was measured; and development of the FASTBUS system. (GHT)
Date: May 1, 1981
Creator: Wattenberg, A. & Simmons, R. O.
Partner: UNT Libraries Government Documents Department

Studies of the Rapid Beam Ejector at the Cosmotron

Description: Extraction of the external beam of the cosmotron with maximum efficiency and minimum duration for measurements of the magnetic moment of the lambda hyperon requires addition of a rapid beam ejector (RBE). Early experiments with the RBE give lower ejection efficiency than the standard ejection system. Reconstruction of the RBE with lengthening of the rise time of the system gives improved values. Computer studies that involve solving the equation of motion for the radial betatron oscillation with time increasing perturbation in one section yield information on particle distributions and result in increases of the turn spacings in RBE to prevent betatron oscillation distribution distortions. Ejection efficiency is now the same with and without the RBE. (D.C.W.)
Date: January 16, 1963
Creator: Barton, M. Q.; Kernan, W.; Novey, T.; Warshaw, S. & Wattenberg, A.
Partner: UNT Libraries Government Documents Department

Method of measuring the polarization of high momentum proton beams. [Primakoff effect, asymmetries]

Description: A method of measuring the polarization of high momentum proton beams is proposed. This method utilizes the Primakoff effect and relates asymmetries at high energy to large asymmetries already measured at low energy. Such a new method is essential for the success of future experiments at energies where present methods are no longer feasible.
Date: January 1, 1976
Creator: Underwood, D.G.
Partner: UNT Libraries Government Documents Department

Observation of. lambda. -hypernuclei in the reaction /sup 12/C(. pi. /sup +/,K/sup +/)/sub. lambda. //sup 12/C

Description: The observation of ..lambda..-hypernuclear levels in /sub ..lambda..//sup 12/C by associated production through the (..pi../sup +/,K/sup +/) reaction is reported. Spectrometers used in the measurements are discussed. The /sub ..lambda..//sup 12/C excitation energy spectra were recorded at laboratory scattering angles of 5.6/sup 0/, 10.3/sup 0/, and 15.2/sup 0/. The spectra show two major peaks - one attributed to the ground state, and one about 11 MeV higher in excitation. The peak near 11 MeV excitation energy is believed to be almost entirely composed of a multiplet of three J/sup ..pi../ = 2/sup +/ states. Relativistic DWBA calculations imply support for the expectation that higher spin states are preferentially populated in the (..pi../sup +/,K/sup +/) reaction, compared to the (K/sup -/,..pi../sup -/) reaction in which lower spin states are excited. 29 refs., 40 figs.
Date: December 1, 1985
Creator: Milner, E.C.
Partner: UNT Libraries Government Documents Department

Neutral kaon and lambda production in electron-positron annihilation at 29 GeV and the Z boson resonance

Description: The production of K{sup 0} and {Lambda} in the hadronization of q{bar q} events from e{sup +}e{sup {minus}} collisions at 29 GeV and the Z{sup 0} resonance is studied using the Mark II detector as upgraded for running at the Stanford Linear Collider. Hadronization processes cannot presently be calculated with Quantum Chromodynamics; instead, hadronization models must be used in comparisons with data. In these models, hadronization occurs at local energy scales of a few GeV, a level at which small differences in quark and diquark mass significantly affect the production of particles such as K{sup 0} and {Lambda}, the lightest neutral meson and baryon containing strange quarks. Their production and behavior in hadronic events is a test for the accuracy of our understanding of hadronization. Two-charged- particle decays of the K{sup 0} and {Lambda} are isolated within the hadronic event sample. The resulting distribution of K{sup 0} and {Lambda} are corrected for inefficiencies and generalized to include all K{sup 0} and {Lambda}. Various kinematic distributions of the strange particles are examined. These distributions include the momentum and scaled momentum of the particles. The kinematics of the particles with respect to the original quark direction are examined through the distributions of rapidity and momentum transverse to the thrust both in and out of the event plane. The dependence of K{sup 0} and {Lambda} production on the sphericity of the hadronic events is also examined. All these distributions show that the behavior of K{sup 0} and {Lambda} in hadronic events is consistent with the hadronization models.
Date: October 1, 1990
Creator: Fordham, C.S.
Partner: UNT Libraries Government Documents Department


Description: Information on the properties of the nuclear interactions of hyperons, weak interactions of the hyperon ( LAMBDA ), and properties of nuclei that could be obtained by studying hypernuclei is discussed. Experiments that should be able to give relevant information in the near future are considered. (D.C.W.)
Date: January 1, 1963
Creator: Dalitz, R H
Partner: UNT Libraries Government Documents Department

Proposal to study some rare pion and kaon induced reactions using the 40'' rapid cycling system

Description: The 40'' hydrogen bubble chamber is used in a triggered mode to obtain a ten to thirty times increase over current data in a few specific reactions with incident pi /sup +/ and K/sup -/ mesons. These reactions are pi /sup +/p yields DELTA /sup ++/K/sup +/K/sup -/, DELTA /sup ++/pp, ppn, p K/sup +/K/sup o/, Y/sup */K/sup +/ pi /sup o/, /0 yields Search for the 0(1820) yields Yg yields Y/sup */ pi /sup -/. This will allow a study of the mre decay modes of meson resonances which one can combine with the high statistics study of pion decays. There will be many quasi two-body channels where production characteristics and joint decay correlations will give further insights into the dynamics of strong interactions. (auth)
Date: February 18, 1974
Partner: UNT Libraries Government Documents Department