We treat the hadrons as an ensemble of quark-gluon Fock states where contributions from sea-quarks and gluons can be studied in detail for the properties of low lying baryons. Statistical model is applied to calculate individual probabilities from various scalar, vector and tensor sea components in flavor, spin and color subspaces for each quark-gluon Fock state. The mass of strange quark is imposed in terms of constraints to the availability of strange quarks in the sea and free energy of gluons in conformity with experimental indications. We calculate multiplicities for different sets of Fock states to compute the role of strange sea for cascade doublet Ξ+, and Ξ-.The low energy properties like magnetic moment, weak decay matrix elements and axial coupling constant ratios have been studied. The incorporation of strange quark gluon sea is discussed and they found to affect the results by almost 46% . The results provide deeper understanding for baryon structure thereby motivating experiments for further inspection, especially the spin distribution among the quarks and gluons.
Strangeness, charmonium and open charm yields in relativistic nucleus-nucleus collisions are considered within statistical model approach as potential signals of the quark-gluon plasma.
A calculation of thermal gluon decay shows that this process contributes significantly to strangeness production in a quark-gluon plasma. Our analysis does not support recent claims that this is the dominant process. In our calculations we take into account the resummed form of the transverse and longitudinal parts of the gluon propagator following the Braaten-Pisarski method. Our results are subject to the uncertainty concerning the estimate of the damping rate entering the effective gluon propagator.
A brief summary of strangeness mile stones is followed by a chemical non-equilibrium statistical hadronization analysis of strangeness results at SPS and RHIC. Strange particle production in AA interactions at \sqrt{s_{NN}}\ge 8.6 GeV can be understood consistently as originating from the deconfined quark--gluon plasma in a sudden hadronization process. Onset of QGP formation as function of energy is placed in the beam energy interval 10--30A GeV/c. Strangeness anomalies at LHC are described.
We apply, to the new OPAL data on V+A strange spectral functions, a suitable combination of QCD spectral sum rules directly sensitive to the combination of strange quark (m_s) and tachyonic gluon (λ^2) masses . Using the mean value of λ^2 from a sum rule analysis of different channels, we deduce the invariant strange quark mass m_s= (106 +33 -37) MeV to order α_s^3, which leads to the running mass m_s(2 GeV)= (93 +29 -32) MeV. We also obtain an interesting though less competitive estimate of the CKM angle: |V_{us}|=0.217\pm 0.019.
This contribution summarizes a presentation combining two topics in lattice QCD. Firstly, the gluon propagator in Landau gauge is calculated in quenched QCD on a large (32^3x64) lattice at beta=6.0. New structure seen in the infrared region survives conservative cuts to the lattice data, and serves to exclude a number of models that have appeared in the literature. Secondly, I report on a recent lattice QCD calculation of the strangeness magnetic moment of the nucleon. The result is G_M^s(0) =-0.36 +/- 0.20 . The strangeness Sachs electric mean-square radius was also found to be small and nega…
Statistical hadronization is presented as mechanism for (strange) particle production from a deconfined quark--gluon plasma (QGP) fireball. We first consider hadronic resonance production at RHIC as a test of the model. We present in detail how the hadrochemistry determines particle multiplicities and in case of sudden hadronization allows investigation of QGP properties. A comparative study of strange hadron production at SPS and RHIC is presented. The energy dependence of physical observables shows regularities and a potential discontinuity in the low RHIC range, when comparing these differe…
Probabilities of various Fock states with strange and nonstrange quark-gluon sea contents are calculated to probe the hadronic structure. Particularly for nucleon, we find various contributions to the low energy properties from scalar, vector and tensor sea in addition to three valence quarks. We focus on the importance of individual sea contributions to the low energy parameters of nucleon by taking the strange and non strange quark-gluon content to the hadron sea. We confirm that the extended Fock space wavefunction is capable of explaining the experimental results where vector sea plays a c…
The hadronic particle production data from relativistic nuclear Pb--Pb 158 A GeV collisions are successfully described within the chemical non-equilibrium model, provided that the analysis treats Omega and anti-Omega abundances with care. We further show that there is a subtle influence of the Coulomb potential on strange quarks in quark matter which is also seen in our data analysis, and this Coulomb effect confirms the finding made by chemical analysis in the S--Au/W/Pb 200 A GeV collisions that the hadron particle source is deconfined with respect to strange quark propagation. Physical free…
We study the gluonic sector of the three-flavor PNJL model by obtaining the adjoint Polyakov loop and the gluon distribution function in the mean-field approximation. Besides, we explore the thermal strange quark pair-production processes, $q\bar {q} \to s\bar {s}$ and $gg \to s \bar {s}$, with the aid of the three-flavor PNJL model. The results help us identify the temperature where the gluonic contribution to the production rate becomes dominant, which is an innovative phenomenon compared with the result obtained in free perturbation theory.
We review the methods and results obtained in an analysis of the experimental heavy ion collision research program at nuclear beam energy of 160-200A GeV. We study strange, and more generally, hadronic particle production experimental data. We discuss present expectations concerning how these observables will perform at other collision energies. We also present the dynamical theory of strangeness production and apply it to show that it agrees with available experimental results. We describe strange hadron production from the baryon-poor quark-gluon phase formed at much higher reaction energies…
Strangeness flavor yield s and the entropy yield S are the observables of the deconfined quark-gluon state of matter which can be studied in the entire available experimental energy range at AGS, SPS, RHIC, and, in near future, at the LHC energy range. We present here a comprehensive analysis of strange, soft hadron production as function of energy and reaction volume. We discuss the physical properties of the final state and argue how evidence about the primordial QGP emerges.
This is a short survey of signatures and characteristics of the quark-gluon plasma in the light of experimental results that have been obtained over the past three decades. In particular, we present an in-depth discussion of the strangeness observable, including a chronology of the experimental effort to detect QGP at CERN-SPS, BNL-RHIC, and CERN-LHC.
I review the foundational motivation which led us to the ultra relativistic heavy ion collision research at SPS, RHIC and now LHC: the quantum vacuum structure; the deconfined nature of quark-gluon plasma (QGP) phase filling the Universe for the first 30$μ$s after the big-bang; the origin of stable matter mass; and of the origin of flavor. The special role of strangeness enhancement and strange antibaryon signature is highlighted. It is shown how hadron production can be used to determine the properties of QGP, and how the threshold energy for QGP formation is determined.
We study the temperature dependence of the adjoint Polyakov loop and its implication for the momentum spectrum of gluons in the mean-field approximation. This allows us to calculate the contribution of the thermal (transverse) gluons to the thermodynamic pressure. As an application, we evaluate the rates for the strange quark pair-production processes $q\bar{q} \to s\bar{s}$ and $gg \to s\bar{s}$ as functions of temperature including thermal effects on quark deconfinement and chiral symmetry breaking.
We look from a theoretical perspective at the new phase of matter, quark-gluon plasma (QGP), the new form of nuclear matter created at high temperature and pressure. Here I retrace the path to QGP discovery and its exploration in terms of strangeness production and strange particle signatures. We will see the theoretical arguments that have been advanced to create interest in this determining signature of QGP. We explore the procedure used by several experimental groups making strangeness production an important tool in the search and discovery of this primordial state of matter present in the…
New results going beyond those obtained from isospin and flavor symmetry and subject to clear experimental tests are obtained for effects of FSI in $B^\pm$ decays to final states containing neutral flavor-mixed mesons like $ω$, $ϕ$, $η$ and $η'$. The most general strong-interaction diagrams containing arbitrary numbers of quarks and gluons are included with the assumptions that any $q \bar q$ pair created by gluons must be a flavor singlet, and that there are no hairpin diagrams in which a final meson contains a $q \bar q$ pair from the same gluon vertex. The smallness of $K^- η$ suggests that…
A useful inequality is obtained if charmless strange B decays are assumed to be dominated by the gluonic penguin diagram and the tree diagram contribution is small but not negligible. The penguin-tree interference contribution which is linear in the tree amplitude is included but the direct tree contribution which is quadratic is neglected.
We utilize the MIT bag model and two different versions of the Color Dielectric Model in order to study the properties of strange matter, and to discuss the stability of strangelets. We also investigate the effect of the introduction of perturbative gluons. The MIT bag model and the Double Minimum version of the Color Dielectric Model allow the existence of strangelets, while the Single Minimum version excludes this possibility.
We calculate the Meissner masses of gluons in neutral three-flavor color superconducting matter for finite strange quark mass. In the CFL phase the eissner masses are slowly varying function of the strange quark mass. For large strange quark mass, in the so called gCFL phase, the Meissner masses of gluons with colors $a=1,2,3$ and 8 become imaginary, indicating an instability.
The asymmetry of strange baryon production in Kp interactions at high energies is considered in the framework of the Quark-Gluon String Model. The contribution of the String-Junction Mechanism to the strange baryon production is analysed.
We investigate the effect of a small, gauge-invariant mass of the gluon on the anomalous chromomagnetic moment of quarks (ACM) by perturbative calculations at one loop level. The mass of the gluon is taken to have been generated via a topological mass generation mechanism, in which the gluon acquires a mass through its interaction with an antisymmetric tensor field $B_{μν}$. For a small gluon mass $(<10$ MeV), we calculate the ACM at momentum transfer $q^2=-M_Z^2$. We compare those with the ACM calculated for the gluon mass arising from a Proca mass term. We find that the ACM of up, down, stra…
We present the results of a new global analysis of DIS data characterized by an enlarged neutrino and antineutrino data set. Special emphasis is given to the strange sector. The strange sea distribution is determined independently of the non strange sea. The possibility of a charge asymmetry, s(x) different from sbar(x), is tested.
Two signatures of the quark-gluon plasma - strangeness `enhancement' and J/psi `suppression' - in nucleus-nucleus collisions are critically discussed. A recently developed statistical coalescence model for J/ψproduction is presented. The measurements at the RHIC energies are crucial for disentangling the different scenarios of J/ψformation.
A useful inequality is obtained if charmless strange B decays are assumed to be dominated by a $ΔI = 0$ transition like that from the gluonic penguin diagram and the contributions of all other diagrams including the tree, electroweak penguin and annihilation diagrams are small but not negligible. The interference contributions which are linear in these other amplitudes are included but the direct contributions which are quadratic are neglected.
We perform QCD fit of the nucleon strange and anti-strange sea distributions to the neutrino and anti-neutrino dimuon data by the CCFR and NuTeV collaborations, supplemented by the inclusive charged lepton-nucleon Deep Inelastic Scattering (DIS) and Drell-Yan data. The effective semi-leptonic charmed-hadron branching ratio is constrained from the inclusive charmed hadron measurements performed by the FNAL-E531 and CHORUS neutrino emulsion experiments as $B_μ=(8.8\pm0.5)%$. We obtain a strange sea suppression factor {$κ(20 {\rm GeV}^2)=0.62\pm0.04({\rm exp.})\pm0.03({\rm QCD})$}. An $x$-distrib…
Assuming that vector and scalar diquarks exist in the Quark-Gluon Plasma near the critical temporature $T_c$, baryons can be produced through the processes of quarks and diquarks forming $({1/2})^+$ baryon states. Ratios of different baryons can be estimated through this method, if such kind of QGP with diquarks can exists.
We investigate the relativistic equation of state of hadronic matter and quark-gluon plasma at finite temperature and baryon density in the framework of the non-extensive statistical mechanics, characterized by power-law quantum distributions. We impose the Gibbs conditions on the global conservation of baryon number, electric charge and strangeness number. For the hadronic phase, we study an extended relativistic mean-field theoretical model with the inclusion of strange particles (hyperons and mesons). For the quark sector, we employ an extended MIT-Bag model. In this context we focus on the…
We introduce the concept of ``locality" for the strange sea in the nucleon, which measures proximity of the strange and anti-strange quarks in the momentum and coordinate spaces. The CCFR data for the strange and anti-strange distributions imply a ``local" strange sea in the momentum space, which is unexpected in QCD and is at variance with the simple meson-cloud model where the strangeness is generated from the virtual transition of the nucleon to a hyperon plus a kaon. We present a simple model to interpret the CCFR data and to correlate momentum and coordinate space locality, yielding an up…
Two signatures of the quark-gluon plasma -- strangeness `enhancement' and $J/ψ$ `suppression' -- in nucleus--nucleus collisions at the SPS energies are critically discussed.
We present an analysis of the nucleon strange sea extracted from a global Parton Distribution Function fit including the neutrino and anti-neutrino dimuon data by the CCFR and NuTeV collaborations, the inclusive charged lepton-nucleon Deep Inelastic Scattering and Drell-Yan data. The (anti-)neutrino induced dimuon analysis is constrained by the semi-leptonic charmed-hadron branching ratio $B_μ=(8.8\pm0.5)%$, determined from the inclusive charmed hadron measurements performed by the FNAL-E531 and CHORUS neutrino emulsion experiments. Our analysis yields a strange sea suppression factor $κ(Q^2=2…
We consider determinations of the strange sea in the nucleon based on the QCD analyses of data collected at the LHC with focus on the recent high-statistics ATLAS measurement of the $W^\pm$- and $Z$-boson production. We study the effect of different functional forms for parameterization of the parton distribution functions and the combination of various data sets in the analysis. We compare to earlier strange sea determinations and discuss ways to improve them in the future.
We perform an analysis of the relation between the factorization scale and the masses of the quarks in the calculation of the hard gluon coefficient in polarized deep inelastic scattering. Particular attention is paid to the role of strange and charm quarks at finite momentum transfer. It is found that for the momentum transfer of the present experiments, the contribution from the charm quark is significant.
We propose new method which allows determination of the strange-sea quark spin distribution in the nucleon through measurement of various inclusive and semi-inclusive polarized deep inelastic electron- or muon-proton reactions. It is shown, that using combinations of inclusive data and semi-inclusive data containing neutral pions in the final state, it is possible to extract the strange-sea quark spin distribution. Similar result can be obtained for charged pions and some other hadrons also.
Theoretical predictions are given for the strange sea distributions in the nucleon based on the flavor SU(3) chiral quark soliton model, with emphasis upon the asymmetry of quark and antiquark distributions. We find that the quark-antiquark asymmetry of the strange sea is much larger for the longitudinally polarized distribution functions than for the unpolarized ones. A preliminary comparison with the CCFR data for the unpolarized $s$-quark distribution and with the LSS fits of the longitudinally polarized distribution functions is encouraging.
We discuss the properties of strange matter, in particular the minimum of the energy per baryon number as a function of the strangeness fraction. We utilize both the MIT bag model and the Color Dielectric Model and compare the energy per baryon with the masses of hyperons having the corresponding strangeness fraction, which are coherently calculated within both models. We also take into account the perturbative exchange of gluons. The results obtained in the two approaches allow to discuss the stability of strangelets. While the MIT bag model and the double minimum version of the Color Dielect…
A constraint between thermal fireball parameters arises from the requirement that the balance of strangeness in a fireball is (nearly) zero. We study the impact of this constraint on (multi-)strange (anti-)baryon multiplicities and compare the hadron gas and quark-gluon plasma predictions. We explore the relation between the entropy content and particle multiplicities and show that the data are compatible with the quark-gluon plasma hypothesis, but appear to be inconsistent with the picture of an equilibrated hadron gas fireball. We consider the implications of the results on the dynamics of e…
In some models, exotic baryons with strangeness and anticharm or antibeauty should exist and even be stable against strong decay. We consider the stability of such possible exotic baryons, which in the constituent quark picture are called pentaquarks (each is composed of four quarks and an antiquark). Our model is based on diquark clustering and supersymmetry in hadrons, and assumes that the spin-dependent force between quarks arises from one-gluon exchange. In the model, a pentaquark with strangeness and anticharm can decay strongly, but an analogous pentaquark with an antibeauty quark is sta…
We present a preliminary account of a new global QCD analysis of DIS data, including recent $ν, \bar ν$ DIS measurements. The model-independent cross section reanalysis by CCFR allows a new determination of the strange sea asymmetry, whose first moment is found to be small. The impact on the NuTeV measurement of $\sin^2 θ_W$ is discussed.
A previous work establishing a connection between a quark model, with relativistic kinematics and a $Y$-confinement plus one gluon exchange, and the $1/N_c$ expansion mass formula is extended to strange baryons. Both methods predict values for the SU(3)-breaking mass terms which are in good agreement with each other. Strange and nonstrange baryons are shown to exhibit Regge trajectories with an equal slope, but with an intercept depending on the strangeness. Both approaches agree on the value of the slope and of the intercept and on the existence of a single good quantum number labeling the ba…
We show that there is no real conflict between the two determinations of the strange sea density from the opposite--sign dimuon production and from the difference of the $F_2$ structure functions measured in neutrino and muon deep inelastic scattering. Once non universal sea parton densities are introduced, which take into account the effects of different mass thresholds and different longitudinal contributions, the discrepancy is shown to disappear and both sets of data are simultaneously well reproduced. No need for a large strange sea content of the nucleon emerges.
In this work we study the strange sea of the proton using a version of the Meson Cloud Model containing both, efective and perturbative degrees of freedom. We construct the $s$ and $\bar{s}$ parton distributions functions at the initial energy scale, $Q_0^2$, where QCD evolution starts. The initial $s$ and $\bar s$ pdfs depend on a number of parameters which we fix by comparison to parameterizations of the strange sea of the nucleon obtained in a recent global fit to experimental data, allowing for a $s-\bar{s}$ asymmetry. We show that the model describes well the strange sea of the proton and…
The strange sea of the proton is generally assumed to have quark - antiquark symmetry. However it has been known for some time that non-perturbative processes involving the meson cloud of the proton may break this symmetry. Recently this has been of interest as it affects the analysis of the so-called `NuTeV anomaly', and could explain the large discrepancy between the NuTeV measurement of $\sin^{2} θ_{W}$ and the currently accepted value. In this paper we re-examine strange - anti-strange asymmetry using the meson cloud model. We calculate contributions to the strange sea arising from fluctua…
Our recent theoretical analysis based on the flavor SU(3) chiral quark soliton model predicts fairly large particle-antiparticle asymmetry of the strange sea in the nucleon. We point out that the predicted magnitude of asymmetry is large enough to solely resolve the so-called NuTeV anomaly on the fundamental parameter $\sin^2 θ_W$ in the standard model.
We evaluate the medium effects in nucleon which can induce an asymmetry of the strange sea. The short-distance effects determined by the weak interaction can give rise to $δm\equiv Δm_s-Δm_{\bar s}$ where $Δm_{s(\bar s)}$ is the medium-induced mass of strange quark by a few KeV at most, but the long-distance effects by strong interaction could be sizable.
We use the method of QCD sum rules to investigate a possible hybrid baryon with the quantum numbers of the $Λ$. Using a current composed of uds quarks in a color octet and a gluon, a strange hybrid, the $Λ_H$ is found about 500 MeV above the $Λ$, and we identify it as the $Λ(1600)$. Using our sigma/glueball model we predict a large branching fraction for the $Λ_H \to Λ+ σ(ππ$ resonance), and the experimental search for this decay mode could provide a test of the hybrid nature of the $/Lambda(1600)$.
Neutrino induced deep inelastic charm production off strange sea partons in the nucleon is studied in the framework of the MSbar fixed flavor factorization scheme. The momentum (z) distributions of the produced D mesons as calculated in the next-to-leading order QCD analysis are presented and compared to their leading order counterparts. Perturbative stability within this formalism is demonstrated and the compatibility of recent next-to-leading order (NLO) strange quark distributions with available dimuon data is investigated. Our NLO (MSbar) results provide, for the first time, the tools requ…
Charm production as related to the determination of the strange sea density in deep inelastic charged current processes is studied predominantly in the framework of the $\overline{\rm{MS}}$ fixed flavor factorization scheme. Perturbative stability within this formalism is demonstrated. The compatibility of recent next-to-leading order strange quark distributions with the available dimuon and $F^{νN}_2$ data is investigated. It is shown that final conclusions concerning these distributions afford further analyses of presently available and/or forthcoming neutrino data.
The minimum energy per baryon number of strange quark matter is studied, as a function of the strangeness fraction, in the MIT bag model and in two different versions of the Color Dielectric Model: a comparison is made with the hyperon masses having the same strangeness fraction, and coherently calculated within both models. Calculations are carried out in mean field approximation, with one gluon exchange corrections. The results allow to discuss the model dependence of the stability of strangelets: they can be stable in the MIT bag model and in the double minimum version of the Color Dielectr…
We investigate the flavour and quark-antiquark structure of the polarized nucleon by calculating the parton distribution functions of the nucleon sea using the meson cloud model. We find that the SU(2) flavor symmetry in the light antiquark sea and quark-antiquark symmetry in the strange quark sea are broken, {\it i.e.} $Δ\ubar < Δ\dbar$ and $Δs < Δ\sbar$. The polarization of the strange sea is found to be positive, which is in contradiction to previous analyses. We predict a much larger quark-antiquark asymmetry in the polarized strange quark sea than that in the unpolarized strange quark sea…
We have revisited the calculation of the neutron electric dipole moment in the presence of the CP-violating operators up to dimension five based on the chiral perturbation theory. Especially, we focus on the contribution of strangeness content. In the calculation, we extract the nucleon matrix elements of scalar-type quark operators from the results of the lattice QCD simulations, while those of the dipole-type quark-gluon operators are evaluated by using the method of the QCD sum rules. As a result, it is found that although the strangeness quantity in nucleon is small, the contribution of th…
We suggest a new CPX-derived scenario for the search of strangephilic MSSM Higgs bosons at the Tevatron and the LHC, in which all neutral and charged Higgs bosons decay predominantly into pairs of strange quarks and into a strange and a charm quark, respectively. The proposed scenario is realized within a particular region of the MSSM parameter space and requires large values of tan(beta), where threshold radiative corrections are significant to render the effective strange-quark Yukawa coupling dominant. Experimental searches for neutral Higgs bosons based on the identification of b-quark jet…
The process of baryon production in K p collisions at high energies is considered in the framework of the Quark-Gluon String Model. The contribution of the string-junction mechanism to the strange baryon production is analysed. The results of numerical calculations are in reasonable agreement with the data on inclusive spectra of p, Lambda, bar{Lambda}, and on the bar{Lambda}/Lambda asymmetry. The predictions for Xi and Omega baryons are presented.
The quark/gluon content of eta(1295) and eta(1440) mesons is discussed, mesons being considered as members of the first radial excitation 2^1S_0 qqbar nonet. Recent results on eta(1295) and eta(1440) two-photon widths from L3 together with the information on radiative J/Psi decay allow one to evaluate the eta(1295)/eta(1440) mixing angle and the admixture of the glueball component. We found that eta(1440) is dominantly non-strange qqbar state, with a possible admixture of the glueball component (20 pm 20)%.
The mass modifications of the light vector mesons ($ω$, $ρ$ and $ϕ$) are investigated in asymmetric nuclear matter in the presence of strong magnetic fields, using a QCD sum rule approach. These are computed from the medium modifications of the non-strange and strange light quark condensates as well as scalar gluon condensate. The quark and gluon condensates are calculated from the medium changes of the scalar fields (non-strange and strange) and a scalar dilaton field in the magnetized nuclear matter, within a chiral SU(3) model. The scalar dilaton field within the model breaks the scale inva…
