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Strangeness production in minimum-bias events at CDF

Description: In a recently published paper 1 are emphasized, for the soft subsample extracted from the minimum-bias (MB) dataset of p{bar p} collisions, interesting invariances with the c.m. energy of the charged multiplicity and p{sub T} distributions. We present an analogous study on V{sup 0} production.
Date: January 15, 2003
Creator: Moggi, N.
Partner: UNT Libraries Government Documents Department

A PERSPECTIVE FROM THE AGS.

Description: A working model for the proposed JHF project is the AGS facility at BNL. Research that is being planned at the JHF represent extensions of present AGS experiments. The AGS presently holds the record for beam intensity from a synchrotron. Experience gained and lessons learned over the years from operation of the AGS is invaluable to a new facility like JHF. Presented here is a brief description of the AGS facility with emphasis on the separated particle beam lines that are presently being used for studying strangeness -1 and -2 systems.
Date: March 4, 1998
Creator: PILE,P.H.
Partner: UNT Libraries Government Documents Department

FREEEZE-OUT DYNAMICS AT RHIC.

Description: Investigation of the final hadronic state properties of ultra-relativistics pp and Au+Au collisions supplies information on freeze-out conditions at RHIC and possible insights into early stages of these collisions. A variety of particle spectra measured by STAR are studied within the framework of chemical and local kinetic equilibrium models. Here we present the extracted chemical and final kinetic freeze-out temperatures, strangeness saturation factor, final collective flow velocity, and the inferred flow velocity at chemical freeze-out. In light of those measurements we discuss dynamical evolution of the collision system.
Date: March 15, 2004
Creator: BARANNIKOVA,O. & COLLABORATION), (FOR THE STAR
Partner: UNT Libraries Government Documents Department

Probing the strange nature of the nucleon with phi photoproduction

Description: The presence inside the nucleon of a significant component of strange-antistrange quark pairs has been invoked to explain a number of current puzzles in the low energy realm of QCD. The {sigma} term in {pi}N scattering is a venerable conundrum which can be explained with a 10%--20% admixture. The spin crisis brought on by the EMC result and follow on experiments was first interpreted as requiring a large strange content of s quarks whose spin helped cancel the contribution of the u and d quarks to the nucleon spin, again of order 10%. Excess phi meson production in p{anti p} annihilation at LEAR has also been explained in terms of up to a 19% admixture of s{anti s} pairs. Charm production in deep-inelastic neutrino scattering would appear to provide evidence for a 3% strange sea. It is clear that a definite probe of the strange quark content would be an invaluable tool in unraveling a number of mysteries. The longitudinal beam target asymmetry in {psi} photoproduction is a particularly sensitive probe of that content. It is explored here.
Date: March 6, 1997
Creator: Lowry, M.M.
Partner: UNT Libraries Government Documents Department

Baryon-baryon mixing in hypernuclei

Description: Implications of few-body hypernuclei for the understanding of the baryon-baryon interaction are examined. Octet-octet coupling effects not present in conventional, non strange nuclei are the focus. The need to identify strangeness {minus}2 hypernuclei to test model predictions is emphasized.
Date: May 1998
Creator: Gibson, B. F.
Partner: UNT Libraries Government Documents Department

S = {minus}1 and S = {minus}2 few-body hypernuclei

Description: The S = {minus}1 and S = {minus}2 few-body bound states are the focus of this discussion. Implications for the understanding of the baryon-baryon interaction are examined. Octet-octet coupling effects not found in conventional, non-strange nuclei are highlighted. TJNAF wave function tests for the S = {minus}1 sector are noted. The need to identify S = {minus}2 hypernuclei to explore the S = {minus}2 strong interaction and to test model predictions is emphasized.
Date: November 1997
Creator: Gibson, B. F.
Partner: UNT Libraries Government Documents Department

Strangeness in the Nucleon or the quark model beyond the valence approximation

Description: Simple arguments based on unitarity indicate that meson loops diagrams, induced by an underlying qq pair creation process, should badly disturb the phenomenologically successful spectroscopy and dynamics of the valence quark model, including such simple but mysterious regularities as the OZI rule. The author discusses some recent progress in adding pair creation to the valence quark model in a way which provides rationale for the quark model's success.
Date: January 1, 1999
Creator: Isgur, Nathan
Partner: UNT Libraries Government Documents Department

Probing nucleon strangeness with parity violating electron scattering

Description: The electromagnetic and weak neutral currents display different sensitivities to various strange quark matrix elements of the nucleon. Measurements of the parity-violating electron-proton and electron-nucleus asymmetries at intermediate energies could allow one to extract limits on the nucleon's strange-quark form factors. The prospects for deriving such constraints from present and approved experiments at MIT-Bates and CEBAF, as well as the implications of such measurements for models of nucleon strangeness, are discussed.
Date: June 1, 1993
Creator: Musolf, M.
Partner: UNT Libraries Government Documents Department

A first look at Pb on Pb collisions at 160 GeV/c at CERN SPS

Description: Last year marked a major milestone in the field of relativistic nuclear collisions. Lead beams were successfully accelerated at CERN SPS to an energy of about 160 GeV per nucleon in the projectile (i.e. to about 32 TeV total energy) and the first preliminary results of the analysis of Pb on Pb interactions are already available and discussed. Before going on to the discussion of these results, it would be helpful to stand back for a moment and try to recapitulate what we have learned from light {open_quotes}heavy{close_quotes} ion experiments at CERN SPS with oxygen and sulphur beams. In the first part of this overview we shall shortly summarize the results of the experimental program with {sup 16}O and {sup 32}S beams at CERN SPS. Next, we shall describe the concept of an event-by-event (e-b-e) analysis proposed for study of individual Pb+Pb collisions with several thousand identified hadrons in the final state. The main section of this paper will be focused on the results (very preliminary) of the analysis of the first run with the lead projectiles. To conclude, we will present plans for the future (as we understand them now).
Date: February 1, 1996
Creator: Odyniec, G.J.
Partner: UNT Libraries Government Documents Department

Stability of strange quark stars with nuclear crusts against radial oscillations

Description: This paper investigates the stability of the complete sequence of strange-matter stars with nuclear crusts against radial pulsations (acoustical modes). It is found that a broad class of white dwarf- like strange stars is stable against such pulsations. The same holds for the much denser strange stars, which are the strange counter-parts of neutron stars. All stars possessing still higher central densities (e.g., charm stars) turn out to be unstable.
Date: December 5, 1994
Creator: Kettner, Ch.; Weigel, M.K.; Weber, F. & Glendenning, N.K.
Partner: UNT Libraries Government Documents Department

Aspects of strangeness

Description: We review various aspects of strangeness production in relativistic heavy ion collisions from AGS to CERN energies. The experimental data are briefly summarized and various possible theoretical interpretations of these data are evaluated, such as quark-gluon- plasma (QGP), hadron gas (HG) thermal models, or event generators (cascade models). Some comments on the production of strange clusters are offered.
Date: March 1, 1995
Creator: Dover, C.B.
Partner: UNT Libraries Government Documents Department

Electroproduction of strangeness above the resonance region

Description: A simple and elegant model, based on Reggeized t-channel exchanges, is successful in reproducing the main features of all existing data of the reactions ep-->e'K{sup +}Sigma{sup 0}. In particular, the original way in which gauge invariance is taken into account is found to be essential to describe the ration between the Coulomb and the transverse cross sections at large Q{sup 2} that has been measured recently at Jefferson Laboratory.
Date: April 1, 1999
Creator: Guidal, Michel; Laget, Jean-Marc & Vanderhaeghen, M.
Partner: UNT Libraries Government Documents Department

Puzzles in hyperon, charm and beauty physics.

Description: Puzzles awaiting better experiments and better theory include: (1) the contradiction between good and bad SU(3) baryon wave functions in fitting Cabibbo theory for hyperon decays, strangeness suppression in the sea and the violation of the Gottfried Sum rule--no model fits all; (2) Anomalously enhanced Cabibbo-suppressed D{sup +} {yields} K*{sup +} (s{bar d}) decays; (3) anomalously enhanced and suppressed B {yields} {eta}{prime} X decays; (4) the OZI rule in weak decays; (5) Vector dominance (W {yields} {pi}, {rho}, a{sub 1}, D{sub s}, D*{sub s}) in weak decays; (6) puzzles in doubly-cabibbo-suppressed charm decays; and (7) problems in obtaining {Lambda} spin structure from polarization measurements of produced {Lambda}'s.
Date: October 21, 2002
Creator: Lipkin, H. J.
Partner: UNT Libraries Government Documents Department

Strangeness at SIS energies

Description: In this contribution the authors discuss the physics of strange hadrons in low energy ({approx_equal} 1-2 AGeV) heavy ion collision. In this energy range the relevant strange particle are the kaons and anti-kaons. The most interesting aspect concerning these particles are so called in-medium modifications. They will attempt to review the current status of understanding of these in medium modifications. In addition they briefly discuss other issues related with kaon production, such as the nuclear equation of state and chemical equilibrium.
Date: September 28, 2005
Creator: Koch, Volker
Partner: UNT Libraries Government Documents Department

Meson-Exchange Currents and the Strangeness Radius Of <sup>4</sup>He

Description: Meson-exchange current contributions to the strangeness radius of <sup>4</sup>He are computed in the one-boson exchange approximation.It is found that these contributions introduce a <(approx)10% correction to the one-body contribution.They should not, therefore, hamper the extraction of the nucleon strangeness radius from the parity-violating electron-<sup>4</sup>He asymmetry.
Date: September 1, 1993
Creator: Ramsey-Musolf, Michael & Ramsey-Musolf, Michael
Partner: UNT Libraries Government Documents Department

Charged and strange hadron elliptic flow in Cu+Cu collisions at sqrt sNN = 62.4 and 200 GeV

Description: We present the results of an elliptic flow, v{sub 2}, analysis of Cu+Cu collisions recorded with the STAR detector at RHIC at {radical}s{sub NN} = 62.4 and 200 GeV. Elliptic flow as a function of transverse momentum, v{sub 2}(p{sub T}), is reported for different collision centralities for charged hadrons h{sup {+-}}, and strangeness containing hadrons K{sub S}{sup 0}, {Lambda}, {Xi}, {phi} in the midrapidity region |{eta}| &lt; 1.0. Significant reduction in systematic uncertainty of the measurement due to non-flow effects has been achieved by correlating particles at midrapidity, |{eta}| &lt; 1.0, with those at forward rapidity, 2.5 &lt; |{eta}| &lt; 4.0. We also present azimuthal correlations in p+p collisions at {radical}s = 200 GeV to help estimating non-flow effects. To study the system-size dependence of elliptic flow, we present a detailed comparison with previously published results from Au+Au collisions at {radical}s{sub NN} = 200 GeV. We observe that v{sub 2}(p{sub T}) of strange hadrons has similar scaling properties as were first observed in Au+Au collisions, i.e.: (i) at low transverse momenta, p{sub T} &lt; 2 GeV/c, v{sub 2} scales with transverse kinetic energy, m{sub T} - m, and (ii) at intermediate p{sub T}, 2 &lt; p{sub T} &lt; 4 GeV/c, it scales with the number of constituent quarks, n{sub q}. We have found that ideal hydrodynamic calculations fail to reproduce the centrality dependence of v{sub 2}(p{sub T}) for K{sub S}{sup 0} and {Lambda}. Eccentricity scaled v{sub 2} values, v{sub 2}/{var_epsilon}, are larger in more central collisions, suggesting stronger collective flow develops in more central collisions. The comparison with Au+Au collisions which go further in density shows v{sub 2}/{var_epsilon} depend on the system size, number of participants N{sub part}. This indicates that the ideal hydrodynamic limit is not reached in Cu+Cu collisions, presumably because the assumption of thermalization is not attained.
Date: July 5, 2010
Creator: Collaboration, STAR & Abelev, Betty
Partner: UNT Libraries Government Documents Department

H particle searches at Brookhaven

Description: Following the suggestion by R.L. Jaffe twenty years ago, researchers have been trying to establish the existence of a six-quark object, termed the H dibaryon, predicted by the phenomenological quark bag model. This object quickly became the focus of experimental searches at several locations, including the AGS. This search still continues, with perhaps the most active program being carried out at the 2.0 GeV/c beam line at the BNL-AGS. The research was considerably enhanced by the writing of two notable papers at BNL by Aerts and Dover, which gave quantitative predictions for H-production cross sections in two very different reaction mechanisms. One of these, the formation of cascade atomic deuterium to form the H by fusion, had been first suggested by P.D. Barnes. The 2.0 GeV/c line at the AGS was specifically designed to provide an adequate kaon flux for double strangeness and charge exchange reactions. It has been used for two H searches, E813 and E836, as well as for several {Lambda}{Lambda} searches, E885 and E906. These four experiments are setting significant limits on H-production. The results of these experiments are discussed, and descriptions of related H searches at Brookhaven are given.
Date: September 1, 1997
Creator: Chrien, R.E.
Partner: UNT Libraries Government Documents Department

Probing Proton Strangeness with Time-Like Virtual Compton Scattering

Description: We document that p(gamma,e+e-)p measurements will yield new, important information about the off-shell time-like nucleon form factors, especially in the phi meson region (q{sup 2} = M{sup 2}{sub {phi}}) governing the phi N couplings g{sup V,T}{sub {phi}NN}. Calculations for p(gamma,e+e-)p, utilizing vector meson dominance, predict measurable phi enhancements at high |t| compared to the expected phi background production from pi, eta and Pomeron exchange. The phi form factor contribution generates a novel experimental signature for OZI violation and the proton strangeness content. The phi N couplings are determined independently from a combined analysis of the neutron electric form factor and recent high |t| phi photoproduction. The pi, eta and Pomeron transition form factors are also predicted and the observed pi and eta transition moments are reproduced.
Date: May 1, 2002
Creator: Cotanch, Stephen R. & Williams, Robert A.
Partner: UNT Libraries Government Documents Department

Hyperon-nucleon bound states and electroproduction of strangeness on light nuclei.

Description: The A(e,e{prime}K{sup +})Y X reaction has been investigated in Hall C at Jefferson Lab. Data were taken for Q{sup 2} {approx} 0.35 and 0.5 GeV{sup 2} at a beam energy of 3.245 GeV for {sup 1}H, {sup 2}H, {sup 3}He and {sup 4}He, C and Al targets. The missing mass spectra are fitted with Monte Carlo simulations including {Lambda}, {Sigma}{sup 0}, {Sigma}{sup -} hyperon production. Models for quasifree production are compared to the data, excess yields close to threshold are attributed to FSI. Evidence for {Lambda}-hypernuclear bound states is seen for {sup 3,4}He targets.
Date: June 25, 2002
Creator: Dohrmann, F.; Abbott, D.; Ahmidouch, A.; Ambrozewicz, P.; Armstrong, C. S.; Arrington, J. et al.
Partner: UNT Libraries Government Documents Department

A perspective from the AGS

Description: A working model for the proposed SHF project is the AGS facility at BNL. Research that is being planned at the JHF represent extensions of present AGS experiments. The AGS presently holds the record for beam intensity from a synchrotron. Experience gained and lessons learned over the years from operation of the AGS is invaluable to a new facility like JHF. Presented here is a brief description of the AGS facility with emphasis on the separated particle beam lines that are presently being used for studying strangeness {minus}1 and {minus}2 systems.
Date: March 4, 1998
Creator: Pile, P.H.
Partner: UNT Libraries Government Documents Department

Asymmetric quarks in the proton

Description: Asymmetries in the quark momentum distributions in the proton reveal fundamental aspects of strong interaction physics. Differences between {anti u} and {anti d} quarks in the proton sea provide insight into the dynamics of the pion cloud around the nucleon and the nature of chiral symmetry breaking. Polarized flavor asymmetries allow the effects of pion clouds to be disentangled from those of antisymmetrization. Asymmetries between s and {anti s} quark distributions in the nucleon are also predicted from the chiral properties of QCD.
Date: March 1, 2000
Creator: Melnitchouk, W.
Partner: UNT Libraries Government Documents Department

Strange vector currents and the OZI-rule

Description: The authors investigate the role of correlated {pi}{rho} exchange in the extraction of matrix elements of the strange vector current in the proton. They show that a realistic isoscalar spectral function including this effect leads to sizably reduced strange vector form factors based on the dispersion--theoretical analysis of the nucleons' electromagnetic form factors.
Date: January 1, 1997
Creator: Meisner, U.; Mull, V.; Speth, J. & Orden, J. Van
Partner: UNT Libraries Government Documents Department