Showing papers on "Strangeness published in 1991"
TL;DR: In this article, the chiral logarithmic corrections to the axial current for semileptonic hyperon decay and for the analysis of the strangeness content of the proton are computed as examples.
811 citations
TL;DR: In this paper, the authors presented an estimate of the inclusive photon energy and hadron mass-spectrum in rare B decays B→Xs+gg, based on perturbative QCD and a phenomenological model for the B-meson wave function.
102 citations
CERN1
TL;DR: In this article, the authors show that uncertainties in the strength of interactions of hyperons among themselves and with nucleons lead to a large uncertainty in the maximum allowed neutron star mass, even if the properties of nuclear and neutron matter are known with infinite precision around normal nuclear matter density and below.
90 citations
TL;DR: A model describing the hadronization of the QGP through particle emission, which is based solely on thermodynamical arguments, and two rather unexpected results are obtained when this model is applied to the investigation of strangelet production.
Abstract: Recently it has been suggested that rather cold droplets of absolutely stable or metastable strange-quark matter may be distilled in heavy-ion collisions during the phase transition from a baryon-rich quark-gluon plasma (QGP) to hadron matter. Here we present a model describing the hadronization of the QGP through particle emission, which is based solely on thermodynamical arguments. Pions and ${\mathit{K}}^{+}$'s and ${\mathit{K}}^{0}$'s carry away entropy and antistrangeness from the system, thus facilitating the cooling process and the strangelet formation. Our results are supported by revised more sophisticated rate calculations. Two rather unexpected results are obtained when this model is applied to the investigation of strangelet production. The strangeness separation mechanism and the formation process works well even for higher initial entropies per baryon, tantamount to higher bombarding energies. The surviving strangelets have a rather high strangeness content, ${\mathit{f}}_{\mathit{s}}$\ensuremath{\sim}1.2--2 [i.e., Z/A\ensuremath{\sim}(-0.1)--(-0.5)]. Hence droplets of strange-quark matter with a baryon number of \ensuremath{\sim}10--30 and with a negative charge may be produced. They may serve as a unique signature for the transient formation of a quark-gluon plasma in heavy-ion collisions.
85 citations
TL;DR: In this paper, the decay rate for the rare radiative decays of the b quark hadrons was calculated in the standard theory of electroweak interactions, using theb quark decay model, in the framework of an effective low energy Lagrangian based on the gauge invariant operators of dimension 6.
Abstract: Inclusive photon energy spectrum and decay rate for the rare radiative decays of theB hadrons,B → γ+X
s
(hereX
s
denotes hadrons with total strangeness quantum numberS=−1), are calculated in the standard theory of electroweak interactions, using theb quark decay model. The calculations have been done in the framework of an effective low-energy Lagrangian based on the gauge invariant operators of dimension 6. The large QCD effects, contained in the Wilson coefficients of these operators, are included in our approach. The shape of the photon energy spectrum and the branching ratio BR (B→γ+X
s
) are sensitive to the top quark mass.
84 citations
TL;DR: In this paper, the production of particles in terms of a statistical formalism requiring strangeness to be exactly conserved while baryon number is treated grand canonically using a chemical potential.
Abstract: We study the production of particles in terms of a statistical formalism requiring strangeness to be exactly conserved while baryon number is treated grand canonically using a chemical potential. A complete treatment is presented for the case where the overall strangeness of the gas is zero and particles having strangeness up to ±3 are present. As an illustration we have applied the above formalism to the description of particle production in proton-proton, proton-nucleus and nucleus-nucleus collisions. In particular theK/π ratio shows a strong dependence on the interaction volume of the system while, in contrast, the ratio
$$\bar \Lambda /\Lambda $$
is almost independent of the volume. These results are in qualitative agreement with experimental data.
77 citations
TL;DR: In this article, the p + p, p + n, and n + n interactions are derived from charge symmetry and charge, baryon and strangeness conservation, and used to yield nucleon-nucleon interaction results.
68 citations
TL;DR: Strangeness production at the CERN Super Proton Synchrotron energies is studied within the quark-gluon string model and model predictions for coming experiments with the Pb beam at CERN are given.
Abstract: Strangeness production at the CERN Super Proton Synchrotron energies is studied within the quark-gluon string model. The observed shape of rapidity and transverse mass distributions are reproduced fairly well for both peripheral and central heavy ion collisions. However, for central collisions the model underpredicts strange particle abundances by a factor of about 2:2:4 for ${\mathit{K}}_{\mathit{S}}^{0}$, \ensuremath{\Lambda}, and \ensuremath{\Lambda}\ifmmode\bar\else\textasciimacron\fi{}, respectively. This discrepancy can be considered as a possible manifestation of collective string-string interactions similar to the formation of a color rope. Model predictions for coming experiments with the Pb beam at CERN are given.
58 citations
TL;DR: Recently, the authors reviewed aspects of the production of strange hadrons in relativistic nuclear collisions and their relevance as a signature of quark-gluon plasma formation, and showed that these hadrons can be used as signatures of the formation of quarks.
52 citations
TL;DR: In this paper, a high statistics study of the inclusive decay properties of the charmed D0 and D+ mesons is presented. But the authors focus on the Ds+ meson.
50 citations
TL;DR: In this paper, the relativistic molecular dynamics approach (RQMD) was used to study pion and kaon production in the reactions p + Be, p + Au and Si + Au at a beam energy of 14.5 A GeV.
TL;DR: In this paper, the authors extended the analysis by taking into account effects of additional mesons includingρ, Ω, σ, K, and K*, with the coupling constants fixed by the low-energy nucleon-nucleon and hyperon nucleon scattering data.
Abstract: As stimulated by earlier attempts for obtaining theπNN andπNδ form factors from the deep inelastic lepton scattering data, we extend the analysis by taking into account effects of additional mesons includingρ, Ω, σ,K, andK*, with the coupling constants fixed by the lowenergy nucleon-nucleon and hyperon-nucleon scattering data. Contrary to an earlier claim that theπ NN andπNδ form factor must be very soft (e.g., with the cutoff mass less than 500 MeV in the monopole form), we find, for example, that with all form factors parametrized in the dipole form, a universal cutoff mass of 1150 MeV in theδ/N sector and 1400 MeV in theλ/σ sector yields predictions in excellent agreement with recently published neutrino data on the momentum fractions carried by thes, Ū, and¯d quarks, as well as consistent with the sea-to-valence ratio extracted from the CDHS data and the Femilab E615 experiment. Similar results can also be obtained by using exponential cutoffs for all couplings, or by using monopole forms for some vertices while retaining dipole forms for the rest. The success of the mesonexchange picture in generating the strangeness content in a proton suggests an alternative understanding of the origin of sea quarks in the proton.
TL;DR: In this paper, a Monte Carlo version of the dual parton model for the description of particle production in hadron-nucleus and nucleus nucleus collisions with a complete formation zone intranuclear cascade is presented.
Abstract: We present a Monte Carlo version of the dual parton model for the description of particle production in hadron-nucleus and nucleus-nucleus collisions with a complete formation zone intranuclear cascade. All generations of secondary interactions are considered. Furthermore, Fermi motion and Pauli's principle are introduced to control the generation of low-energy nucleons. The model is compared with rapidity distributions and grey-particle production in hadron-nucleus interactions as well as with results from nucleus-nucleus collisions. Within the DPM the number of chains with sea-quarks at their ends grows with the complexity of the target and/or projectile nuclei as well as with the collision energy. We discuss this increase of chain-end sea-quarks as a mechanism for strangeness enhancement within the model. Furthermore we study the properties of the model at the energies of future heavy ion colliders.
TL;DR: In this paper, the low energy effective hamiltonian for isovector ( ΔI = 1) nuclear parity violation, including the effects of heavy quarks s, c and b, was calculated.
TL;DR: A survey of the current understanding of the strange particle signature of quark gluon plasma is presented in this paper, with emphasis on the theory of strangeness production in the plasma and recent pertinent experimental results.
Abstract: A survey of our current understanding of the strange particle signature of quark gluon plasma is presented. Emphasis is placed on the theory of strangeness production in the plasma and recent pertinent experimental results. Useful results on spectra of thermal particles are given.
TL;DR: In this paper, the exclusive semi-leptonic charm baryon decays of the lowest lying charm states into the ground state strangeness baryons using the covariant spectator quark model approach.
Abstract: We calculate the exclusive semi-leptonic charm baryon decays of the lowest lying charm baryon states into the ground state strangeness baryons using the covariant spectator quark model approach. We present results on rates,q
2- andE
l
-spectra as well as on the angular decay distribution in the cascade decay
$$\Omega _c \to \Omega ( \to \Xi \pi ,\Lambda {\rm K})$$
.
TL;DR: In this article, the present status of our knowledge of hypernuclei is reviewed from an experimental point of view, especially the existence of the H dibaryon is related to the ground state of nuclear matter with S = -2.
TL;DR: In this article, the strange-quark mass was determined from finite energy and Laplace transform QCD sum rules for the two-point function involving strangeness changing vector currents and their divergences.
TL;DR: In this article, experiments are proposed to measure various strangeness matrix elements of the nucleon, such as electro-and neutrino-production of φ mesons and the difference between neutrinos and antineutrinos scattering from isospin zero targets, e.g., deuterons.
TL;DR: In this paper, the role of zero mode quantum corrections to the energy of baryonic systems with exotic quantum numbers (strangeness) is discussed and a simple expression for the contribution depending on strange inertia is obtained in the SU (3)-collective coordinate quantization approach.
TL;DR: In this paper, the authors consider stability requirements with respect to the quark−hadron phase transition in old and newly born hot neutron stars and show that the existence of neutron stars imposes constraints on the phenomenological parameters of quark matter and gives limits for binding energy of strange matter.
Abstract: Some of the observed pulsars can be identified quite reliably with ordinary neutron stars. If strange matter is stable, the central density in such neutron stars should be lower than the critical density of the quark−hadron phase transition occurring due to the strong interactions only with conservation of fractional concentration of strangeness. The quark matter being formed turns to more stable strange matter on a weak interaction time scale, converting neutron stars into strange stars or black holes. The existence of neutron stars therefore imposes constraints on the phenomenological parameters of the quark matter and gives limits for binding energy of strange matter. We consider stability requirements with respect to the quark−hadron phase transition in old and newly born hot neutron stars
01 Jan 1991
TL;DR: In this paper, the effect of strange quarks on the neutral weak form factor of the nucleon matrix was investigated and it was shown that these effects can contribute to the electroweak form factors and can be isolated through measurement of vector and axial vector neutral weak factor.
Abstract: Recent studies of strange quark matrix elements of the nucleon suggest that the effect of strange quarks on nucleon structure is not small. These effects can contribute to the electroweak form factors of the nucleon and can be isolated through measurement of vector and axial vector neutral weak form factors. We evaluate several past and future lepton scattering experiments in terms of their sensitivity to the strange contributions to the neutral weak form factors.
TL;DR: In this paper, it was shown that the unusual large-x B behavior required for such avoidance is entirely incompatible with that displayed by the existing deep-inelastic neutrino data, ∼ (1 − x ) 10.
TL;DR: In this paper, the axial form factor of the deuteron in the hamiltonian form of the light-front dynamics was derived and the parity-violating assymmetry in the elastic cross sections for electrons initially polarized in the beam direction and for polarized recoil deuterons was calculated.
TL;DR: In this article, the authors briefly give some perspectives on double beta decays and related subjects, including charge nonconservation and electron decays, and show that URANUS is an important detector frontier of non-accelerator nuclear physics in 1990's.
TL;DR: In this article, the multiplicity distribution of strange particles in a hadronic gas constrained by exact strangeness conservation was studied and the results obtained might be useful in determining the thermodynamic parameters (volume, temperature, and baryon density) of a Hadronic gas possibly formed in relativistic nuclear collisions.
Abstract: We study the multiplicity distribution of strange particles in a hadronic gas constrained by exact strangeness conservation. The multiplicity distribution obtained is narrower than both the Poisson and negative binomial distributions. Correlations among strange particles are also discussed. The results presented might be useful in determining the thermodynamic parameters (volume, temperature and baryon density) of a hadronic gas possibly formed in relativistic nuclear collisions.
TL;DR: In this paper, the vector and axial-vector coupling constants of the semileptonic weak decay of hyperons are calculated with the bound kaon approach to strangeness in the Skyrme model proposed by Callan and Klebanov.
01 Aug 1991
TL;DR: In this paper, a strong violation of the Quark Line Rule is observed if we allow the pion nucleon σ term to attain the present experimental value, which indicates the possibility of a large strangeness content in the proton.
Abstract: A strong violation of the Quark Line Rule is observed if we allow the pion nucleon σ term to attain the present experimental value. This in turn indicates the possibility of a large strangeness content in the proton. In this work we have shown that the value of the σ term is seen to be raised from what is expected from the GMOR scheme of chiral symmetry breaking through a sum rule which shows that the ratio of the meson wave function renormalization constants ZK12/Zπ12 may deviate considerably from unity by using the recent QCD estimate on the quark vacuum condensate ratio O/ O
TL;DR: This paper shows one may also measure G^(S)(sub)E(q^2) at finite q^2 in a separate experiment, and within certain models, it should be possible to extract the strange quark vector form factors.
Abstract: Parity violation in elastic ep scattering determines the elastic weak neutral current form factors G^Z(sub)E(q^2) and G^Z(sub)M(q^2) which are directly analogous to the familiar electromagnetic elastic form factors.By using the Standard Model of electroweak interactions and invoking strong isospin for the nucleon, the weak neutral current form factors may be expressed in terms of their electromagnetic counterparts and the strange quark vector form factors G^(S)(sub)E(q^2) and G^(S)(sub)M(q^2).Previous authors have argued that it is feasible to measure G^(S)(sub)E(q^2=0) in this way.In this paper, we show one may also measure G^(S)(sub)E(q^2) at finite q^2 in a separate experiment.Within certain models, it should be possible to extract the