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Hyperon and Negative K-Meson Masses

Description: The following report studies the interactions of K-mesons in nuclear track emulsions and measures range-energy.
Date: September 1957
Creator: Barkas, W. H.; Giles, P. C.; Heckman, Harry H.; Inman, Fred W.; Mason, C. J. & Smith, F. M.
Partner: UNT Libraries Government Documents Department

Search for CP violation in hyperon decays.

Description: Direct CP violation in nonleptonic hyperon decays can be established by comparing the decays of hyperons and anti-hyperons. For {Xi} decay to {Lambda} {pi} followed by {Lambda} to p{pi}, the proton distribution in the rest frame of Lambda is governed by the product of the decay parameters {alpha}{sub {Xi}} {alpha}{sub {Lambda}}. The asymmetry A{sub {Xi}{Lambda}}, proportional to the difference of {alpha}{sub {Xi}}{alpha}{sub {Lambda}} of the hyperon and anti-hyperon decays, vanishes if CP is conserved. We report on an analysis of a fraction of 1997 and 1999 data collected by the Hyper CP (E871) collaboration during the fixed-target runs at Fermilab. The preliminary measurement of the asymmetry is {Alpha}{sub {Xi}{Lambda}} = [-7 {+-} 12(stat) {+-} 6.2(sys)] x 10{sup -4}, an order of magnitude better than the present limit.
Date: October 25, 2002
Creator: Zyla, Piotr
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

Heavy baryons - Recent and very new results

Description: Recent results on observations, properties and decay modes of the charmed and beauty baryons will be reviewed. Candidates for several new high mass states which include a cleanly-identified daughter {Lambda}{sub c}{sup +} baryon are seen in data from the SELEX experiment at Fermilab. These states are candidates for doubly-charmed baryons: a {Xi}{sub cc}{sup ++} state and a {Xi}{sub cc}{sup +} state. These candidates are more than 5{sigma} signals in each case at masses of 3520 and 3460 MeV respectively.
Date: January 15, 2003
Creator: Cooper, Peter S
Partner: UNT Libraries Government Documents Department

Hyperon production asymmetries in 500 GeV/c pion nucleus Interactions

Description: We present a preliminary study from Fermilab experiment E791 of {Lambda}{sup 0}/{anti {Lambda}}{sup 0}, {Xi}{sup -}/{Xi}{sup +} and {Omega}{sup -}/{Omega}{sup +} production asymmetries from {pi}{sup -} nucleus interactions at 500 Gev/c. The production asymmetries for these particles are studied as a function of x{sub F} and p{sup 2}{sub T}. We observed an asymmetry in the target fragmentation region for {Lambda}{sup 0}`s larger than that for {Xi}`s, suggesting diquark effects. The asymmetry for {Omega}`s is significatively smaller than for the other two hyperons consistent with the fact that {Omega}`s do not share valence quarks with either the pion or the target particle. In the beam fragmentation region, the asymmetry tends to 0.1 for both {Lambda}{sup 0}`s and {Xi}`s. The asymmetries vs p{sup 2}{sub T} are approximately constant for the three strange baryons under study.
Date: October 1, 1997
Creator: Solano, J.; Magnin, J.; Simao, F.R.A. & Collaboration, E791
Partner: UNT Libraries Government Documents Department

Physics reach of BTeV

Description: BTeV is a collider program at the Fermilab Tevatron dedicated to the study of CP violation, mixing, and rare decays in beauty and charm hadrons. The detector is a forward spectrometer sited at the C-Zero interaction region.
Date: December 13, 2002
Creator: Kasper, Penelope A
Partner: UNT Libraries Government Documents Department


Description: In order to study resonances in the {Sigma}-{pi} system, we have analyzed reactions in which a {Sigma} hyperon and two or three pions are produced in K{sup -}-p interactions at 1.22 {+-} 0.040 and 1.51 {+-} 0.050 GeV/c incident K{sup -} momentum (i. e., 1895 and 2025 MeV center-of-mass energy), using the Lawrence Radiation Laboratory's 72-in. hydrogen bubble chamber.
Date: June 12, 1962
Creator: Alston, Margaret H.; Alvarez, Luis W.; Ferro-Luzzi, Massimiliano; Rosenfeld, Arthur H..; Ticho, Harold K. & Wojcicki, Stanley G.
Partner: UNT Libraries Government Documents Department


Description: The high-temperature gamma phase of U is body-centered cubic and is stable to the melting point. Molybdenum is one of the body-centered cubic elements that tend to stabilize the gamma phase. The phase diagram, structure of the gamma ' phase, colorimetric measurements, thermal dilation and mechanical properties, electric resistiviiy, and effects of neutron irradiation were studied. (L.T.W.)
Date: October 1, 1956
Creator: Bostrom, W.A. & Halteman, E.K.
Partner: UNT Libraries Government Documents Department


Description: A sample of 2500 {Xi}{sup -} and 500 {Xi}{sup 0} hyperons, produced in {Xi}K, {Xi}K{pi}, and {Xi}K{pi}{pi} final states by K{sup -} (in H{sub 2}) at incident momenta of 1.7 to 2.7 BeV/c, has been analyzed. The data are from an exposure (K-63) of 26 events/{mu}b in the 72-inch bubble chamber; approximately 85% of the {Xi}{sup -} events and 60% of the {Xi}{sup 0} events have been analyzed. For the {Xi}, they determine the spin and decay parameters a{sub {Xi}} and {Phi}{sub {Xi}} = tan{sup -1} ({beta}{sub {Xi}}/{Gamma}{sub {Xi}}). Combining their data with 900 {Xi}{sup -} and 150 {Xi}{sup 0} events from an earlier experiment (K-72), they obtain the following results: (1) {Xi} spin - J = 1/2 favored over J = 3/2 by {approx} 2.5 standard deviations; (2) {Xi} decay parameters (assuming a{sub {Lambda}} = 0.647 {+-} 0.048) - a{sub {Xi}{sup -}} = -0.398 {+-} 0.041, {Phi}{sub {Xi}{sup -}} = 9.8{sup o} {+-} 9.0{sup o}; a{sub {Xi}{sup 0}} = -0.413 {+-} 0.104. They observe {Xi}*(1530) and {Xi}*(1817); their data are insufficient for analysis of suggested {Xi}* resonances at 1705 and 1933 MeV. They measure the {Xi}*(1530) electromagnetic mass difference {Delta}m = m({Xi}*{sup -}) = m({Xi}*{sup 0}) = 2.0 {+-} 3.2 MeV. Using data, part of which has already been described, they find for {Xi}*(1530): J {ge} 3/2 favored over J = 1/2 (the J = 1/2 hypothesis is {approx} 3.5% as probable as the J = 3/2 hypothesis); J{sup P} = 3/2{sup +} favored over 3/2{sup -} by {approx} 2.8 standard deviations. For {Xi}*(1817) decaying into {Xi}*(1530) + {pi}, the hypotheses J{sup P} = 1/2{sup +}, 1/2{sup -}, 3/2{sup -}, 5/2{sup +}, 7/2{sup -}, etc. (corresponding to {ell} = 1, 2, 0 and 2, 1 and 3, and 2 and 4, respectively) are favored over other hypotheses, but results ...
Date: September 10, 1966
Creator: Merrill, Jr., Deane W.
Partner: UNT Libraries Government Documents Department

Energy and system size dependence of phi meson production in Cu+Cu and Au+Au collisions

Description: We study the beam-energy and system-size dependence of {phi} meson production (using the hadronic decay mode {phi} {yields} K{sup +}K{sup -}) by comparing the new results from Cu + Cu collisions and previously reported Au + Au collisions at {radical}s{sub NN} = 62.4 and 200 GeV measured in the STAR experiment at RHIC. Data presented are from midrapidity (|y| < 0.5) for 0.4 < p{sub T} < 5 GeV/c. At a given beam energy, the transverse momentum distributions for {phi} mesons are observed to be similar in yield and shape for Cu + Cu and Au + Au colliding systems with similar average numbers of participating nucleons. The {phi} meson yields in nucleus-nucleus collisions, normalized by the average number of participating nucleons, are found to be enhanced relative to those from p + p collisions with a different trend compared to strange baryons. The enhancement for {phi} mesons is observed to be higher at {radical}s{sub NN} = 200 GeV compared to 62.4 GeV. These observations for the produced {phi}(s{bar s}) mesons clearly suggest that, at these collision energies, the source of enhancement of strange hadrons is related to the formation of a dense partonic medium in high energy nucleus-nucleus collisions and cannot be alone due to canonical suppression of their production in smaller systems.
Date: October 28, 2008
Creator: STAR Collaboration
Partner: UNT Libraries Government Documents Department

Longitudinal Spin Transfer to Lambda and Lambda bar Hyperons in Polarized Proton-Proton Collisions at sqrt s = 200 GeV

Description: The longitudinal spin transfer, D{sub LL}, from high energy polarized protons to {Lambda} and {bar {Lambda}} hypersons has been measured for the first time in proton-proton collisions at {radical}s = 200 GeV with the STAR detector at RHIC. The measurements cover pseudorapidity, {eta}, in the range |{eta}| < 1.2 and transverse momenta, p{sub T}, up to 4 GeV/c. The longitudinal spin transfer is found to be D{sub LL} = -0.03{+-}0.13(stat){+-}0.04(syst) for inclusive {Lambda} and D{sub LL} = -0.12{+-}0.08(stat){+-}0.03(syst) for inclusive {bar {Lambda}} hyperons with <{eta}> = 0.5 and <p{sub T}> = 3.7 GeV/c. The dependence on {eta} and p{sub T} is presented.
Date: July 5, 2010
Creator: STAR Collaboration
Partner: UNT Libraries Government Documents Department

Global polarization measurement in Au+Au collisions

Description: The system created in non-central relativisticnucleus-nucleus collisions possesses large orbital angular momentum. Dueto spin-orbit coupling, particles produced in such a system could becomeglobally polarized along the direction of the system angular momentum. Wepresent the results of Lambda and anti-Lambda hyperon global polarizationmeasurements in Au+Au collisions at sqrt sNN=62.4 GeV and 200 GeVperformed with the STAR detector at RHIC. The observed globalpolarization of Lambda and anti-Lambda hyperons in the STAR acceptance isconsistent with zero within the precision of the measurements. Theobtained upper limit, lbar P Lambda, anti-Lambda rbar<= 0.02, iscompared to the theoretical values discussed recently in theliterature.
Date: August 2, 2007
Creator: Abelev, B. I.; Adams, J.; Aggarwal, M. M.; Ahammed, Z.; Amonett, J.; Anderson, B. D. et al.
Partner: UNT Libraries Government Documents Department

Measurement of Excited Hyperons in Photoproduction at CLAS

Description: Measurement results of photoproduced excited hyperon states using the CLAS detector at Jefferson Lab are shown. The invariant mass distribution of the {Lambda}(1405) has recently been shown to be different for each of the three Sigma pi channels that it decays to, showing that there is prominent interference between the isospin I=0 and I=1 isospin amplitudes. Measurements of the differential and total cross sections of the three hyperons {Lambda}(1405), {Sigma}{sup 0}(1385), and Lambda(1520) are presented and compared. Prospects of future studies using a 12 GeV beam with the GlueX detector are briefly given.
Date: January 1, 2014
Creator: Moriya, Kei & Schumacher, Reinhard A.
Partner: UNT Libraries Government Documents Department

Beauty, charm and hyperon production at fixed-target experiments

Description: Over the years fixed-target experiments have performed numerous studies of particle production in strong interactions. The experiments have been performed with different types of beam particles of varying energies, and many different target materials. Since the physics of particle production is still not understood, ongoing research of phenomena that we observe as beauty, charm and strange-particle production is crucial if we are to gain an understanding of these fundamental processes. It is in this context that recent results from fixed-target experiments on beauty, charm, and hyperon production will be reviewed.
Date: December 11, 2002
Creator: Gottschalk, Erik
Partner: UNT Libraries Government Documents Department

Hyperon static properties

Description: The static properties of the hyperons include masses, lifetimes, magnetic moments and CPT test from the asymmetries of these quantities for hyperon and anti-hyperon. The author reviews the present status of these measurements with an eye toward identifying places where new or improved measurements can have a significant physics impact. Most of these measurements are from the PDG where there have been only two new measurements quoted since 1995. He also reports two new measurements not yet published.
Date: March 24, 2000
Creator: Cooper, P.S.
Partner: UNT Libraries Government Documents Department

Hypernuclear physics at TJNAF

Description: The strangeness electroproduction experiments, just starting to take data at TJNAF, are very promising for giving very useful information to understand the nuclear and nucleonic structure and reaction mechanism. The experimental program on hypernuclei already approved concerns few body, light nuclei and heavy nuclei. It will be possible to investigate these hypernuclear systems for the first time by photo- and electro-induced reactions, allowing to obtain very useful information such as {Lambda}-N interaction and weak interaction in the nuclear medium in a complementary way with respect to what can be done with hadron probes.
Date: November 1, 1999
Creator: Cisbani, E.; Frullani, S.; Garibaldi, F.; Iodice, M.; Urciuoli, G.M.; Leo, R. De et al.
Partner: UNT Libraries Government Documents Department

Hyperons at Fermilab

Description: Magnetic moment measurement of the baryon octet and decouplet have recently been measurements illustrated the success as well as the limitations of the simpple qazrk model. Measurements of hyperon production polarizations have shown this to be a rich and complex process. It has forced us to reconsider our basic understanding of hyperon polarization processes.
Date: November 1, 1995
Creator: Lach, J.
Partner: UNT Libraries Government Documents Department

Hyperon particle physics at JHF

Description: This paper discusses the possibility of a program in hyperon decay physics at the Japan Hadron Facility. The study of hyperon decays has a history of over 40 years of experimental results. However, many of the earliest results are still the best available and there are many gaps in the data. The static properties of hyperons (masses, magnetic moments) are in relatively good shape. Much work remains to be done on the decays of hyperons and hyperon resonances. There are current experiments at the major accelerator facilities that address various hyperon decays, but no comprehensive program. This presents an excellent opportunity for such a program to be considered at JHF. The high-intensity beams of {pi}, K, and p beams will allow experiments to be designed that optimize the properties of the hyperons being studied. It is possible to envision experiments with samples of 10{sup 9} hyperon decays in 10{sup 7} sec runs.
Date: December 1, 1998
Creator: Mischke, R.E.
Partner: UNT Libraries Government Documents Department