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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; Chan, A.; Chen, Y.C.; Ho, C.; Teng, P.K.; Choong, W.S. et al.
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

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


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

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| &lt; 0.5) for 0.4 &lt; p{sub T} &lt; 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: Coll, STAR
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

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}| &lt; 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 &lt;{eta}&gt; = 0.5 and &lt;p{sub T}&gt; = 3.7 GeV/c. The dependence on {eta} and p{sub T} is presented.
Date: July 5, 2010
Creator: Collaboration, STAR & Abelev, Betty
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

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

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

Hyperon Polarization in Unpolarized Scattering Processes

Description: Transverse polarization in the Hyperon (\Lambda) production in the unpolarizeddeep inelastic scattering and pp collisions is studied in the twist-three approach, considering the contribution from the quark-gluon-antiquark correlation distribution in nucleon. We further compare our results for deep inelastic scattering to a transverse momentum dependent factorization approach, and find consistency between the two approaches in the intermediate transverse momentum region. We also find that in pp collisions, there are only derivative terms contributions, and the non-derivative terms vanish.
Date: August 27, 2008
Creator: Zhou, Jian; Yuan, Feng & Liang, Zuo-Tang
Partner: UNT Libraries Government Documents Department

Production of a Theta Degree Particle Without an AssociatedHyperon in a Pi-P Collision

Description: An event is described that is interpreted as evidence for the simultaneous production of a {theta}{sup 0} and a {bar {theta}}{sup 0} according to the scheme of Gell-Mann and Pais. This interpretation assumes the production of a normal {theta}{sup 0} and a K{sup 0} with no associated hyperon, where the {theta}{sup 0} is observed and the K{sup 0} is inferred from the rule of associated production of heavy unstable particles. The event was obtained by exposing a high-pressure diffusion cloud chamber to a 4. 5-Bev/c {pi}{sup -} meson beam from the Bevatron.
Date: February 29, 1956
Creator: Fowler, William B.; Maenchen, George; Wilson, Powell M.; Saphir,George & Wright, Robert W.
Partner: UNT Libraries Government Documents Department

Test of the Universality of Naive-time-reversal-odd Fragmentation Functions

Description: We investigate the&quot;spontaneous'' hyperon transverse polarization in e+e- annihilation and semi-inclusive deep inelastic scattering processes as a test of the universality of the naive-time-reversal-odd transverse momentum dependent fragmentation functions. We find that universality implies definite sign relations among various observables. This provides a unique opportunity to study initial/final state interaction effects in the fragmentation process and test the associated factorization.
Date: August 23, 2010
Creator: Boer, Daniel; Kang, Zhong-Bo; Vogelsang, Werner & Yuan, Feng
Partner: UNT Libraries Government Documents Department