Search

We study a nonlocal extension of the so-called Polyakov Nambu-Jona-Lasinio model at finite temperature and chemical potential, considering the impact of the presence of dynamical quarks on the scale parameter appearing in the Polyakov potential. Both real and imaginary chemical potentials are considered. The effect of varying the current quark mass is also investigated.

We used an equation of state for the cold quark matter to the study of properties of quark stars. We also discuss the absolute stability of quark matter and compute the mass-radius relation for self-bound stars.

We studied an application of nonextensive thermodynamics to describe the polarized structure function of nucleon, in a model where the usual Fermi-Dirac and Bose-Einstein energy distribution, often used in the statistical models, were replaced by the equivalent functions of the q-statistical. The parameters of the model are given by an effective temperature T, the q parameter (from Tsallis statistics), and the chemical potentials given by the corresponding up (u) and down (d) quark normalization in the nucleon and by Δu and Δd of the polarized functions.

An overview of Constituent Quark Models for baryons and their results will be presented and discussed. The emerging need for the introduction of higher Fock components, i.e. the unquenching of the quark model, will also be briefly discussed.

The successful acceleration of an unpolarized Helium-3 beam by the AGS at BNL heralds the possibility of achieving polarized He-3 ions at RHIC. Assessing the level of polarization will be a challenge at high energy as the inelastic channels associated with He-3 scattering off a carbon target in the electromagnetic hadronic interference region may dilute expectations by comparison with the successful use of this method for proton polarimetry. The large anomalous magnetic moment of He-3 is helpful however, though the greater hadronic elastic cross section reduces the optimal analyzing power. Encouragement may be drawn from measurements indicating little high energy hadronic spin dependence.

The measurement of the top quark mass and other top quark properties, such as the W boson polarization, flavor changing neutral currents (FCNC), anomalous production with large missing transverse energy (EmissT) and charge asymmetry in top quark pair (tt) production, at ATLAS are presented in this paper. The results were obtained using the data collected during the 2010 proton-proton run of the LHC at a center-of-mass energy of 7 TeV, which corresponds to an integrated luminosity of 35 pb−1. The charge asymmetry was measured with data taken during 2011 which corresponds to an integrated luminosity of 700 pb−1.

We study how a chiral tricritical point (TCP) on QCD phase diagram is affected by the imbalance of up and down quark densities (isospin density), using the generalized Ginzburg-Landau (GL) approach. The resulting phase diagram near TCP shows a rich fine structure which includes inhomogeneities of both the chiral and the charged pion condensations. It turns out that the TCP splits into multicritical points., 4 pages, 2 eps figures. Presented at QCD@Work 2012: International Workshop on QCD - Theory and Experiment, June 18-21, Lecce (Italy)

The constituent quark number scaling of elliptic flow is studied in a non‐equilibrium hadronization and freeze‐out model with rapid dynamical transition from ideal, deconfined and chirally symmetric Quark Gluon Plasma, to final non‐interacting hadrons. In this transition a Bag model of constituent quarks is considered, where the quarks gain constituent quark mass while the background Bag‐field breaks up and vanishes. The constituent quarks then recombine into simplified hadron states, while chemical, thermal and flow equilibrium break down one after the other. In this scenario the resulting temperatures and flow velocities of baryons and mesons are different. Using a simplified few source model of the elliptic flow, we are able to reproduce the constituent quark number scaling, with assumptions on the details of the non‐equilibrium processes.

A new property of QCD is displayed, that appears as one sums in a gauge invariant way all gluon interactions in a given quark/quark(anti‐quark) scattering process.

I review the dynamics in a new class of models describing the quark mass hierarchy, suggested recently by Michio Hashimoto and the author. In this class, the dynamics primarily responsible for electroweak symmetry breaking (EWSB) leads to the mass spectrum of quarks with no (or weak) isospin violation. Moreover, the values of these masses are of the order of the observed masses of the down‐type quarks. Then, strong (although subcritical) horizontal diagonal interactions for the t quark plus horizontal flavor‐changing neutral interactions between different families lead (with no fine tuning) to a realistic quark mass spectrum. In this scenario, many composite Higgs bosons occur. A concrete model with the dynamical EWSB with the fourth family is described in detail.

We consider some existing relativistic models for the nucleon structure functions, relying on statistical approaches instead of perturbative ones. These models are based on the Fermi‐Dirac distribution for the confined quarks, where a density of energy levels is obtained from an effective confining potential. In this context, it is presented some results obtained with a recent statistical quark model for the sea‐quark asymmetry in the nucleon. It is shown, within this model, that experimental available observables, such as the ratio and difference between proton and neutron structure functions, are quite well reproduced with just three parameters: two chemical potentials used to reproduce the valence up and down quark numbers in the nucleon, and a temperature that is being used to reproduce the Gottfried sum rule violation.

The magnetic moments of spin 12+ and spin 32+ charmed baryons have been calculated in chiral constituent quark model (χCQM). The effects of configuration mixing and quark masses have also been investigated. The results are not only in good agreement with existing experimental data but also show improvement over other phenomenological models.

We plan to make definitive measurements of the deuteron spin structure function g1d/F1d in the deep‐inelastic kinematics accessible with a 6 GeV beam at JLab. The principal goal is to provide the low Q2 anchor points for NLO pQCD plus higher twist fits to g1d/F1d, which is particularly sensitive to ΔG(x) (the polarized gluon density of the nucleon) and the sum of up and down quark polarizations. By spanning a factor of typically two in the Q2‐range at nine values of x, the new data will strongly constrain the higher twist contribution to the fits, with a corresponding reduction in the polarized PDF uncertainties. The proposed measurements, when combined with existing and planned world data at higher Q2, will provide the theoretically cleanest determination of ΔG(x) in the moderate to high x region, and will provide a necessary complement to the low x program of RHIC‐spin.The experiment will use both 6LiD and ND3 as a source of polarized deuterons, with approximately equal running times for both to constra...

A statistical quark model, with quark energy levels given by a central linear confining potential is used to obtain the light sea‐quark asymmetry, d/ū, and also for the ratio d/u, inside the nucleon. After adjusting a temperature parameter by the Gottfried sum rule violation, and chemical potentials by the valence up and down quark normalizations, the results are compared with experimental data available.

Parameters of the Standard Model are derived from empirical relations in particle masses and compared with stable nuclear intervals.

Covariant version of the quark model is studied. It is shown how the polarized and unpolarized structure functions depend on the quark intrinsic motion. The important role of the quark orbital momentum, by which the intrinsic motion is generated, appears as a direct consequence of the covariant description. At the same time, the procedure for obtaining 3D quark momentum distribution from the structure functions is suggested.

The top quark is the most massive elementary particle discovered thus far. Its large mass may help explain the mechanism by which fundamental particles gain mass — the Standard Model’s greatest standing mystery. Today the top quark mass, together with the W boson mass, plays an important role in constraining the Higgs boson mass. The currents status of the top quark mass measurement and a brief outline of the expectation at the Large Hadron Collider and the International Linear Collider will be covered.

This note describes some of the most recent top quark measurements produced by the D0 collaboration. At the same time it tries to give the reader an understanding of why after more that 10 years since the top quark discovery only the top quark pair production cross section and the top quark mass have been measured with relevant accuracy. The rewards that an increase in statistics will bring in the quest to completely characterize the top quark are also discussed.

We survey the predictions made by various extensions of the standard model of electroweak interactions on the decay modes of the top quark which involve the flavor‐changing neutral couplings tcV and tcH, with V = γ,g,Z.

We study the properties of isospin asymmetric quark matter under compact stars constraints using a relativistic quark model with non local interactions in the mean field approximation. We consider a Gaussian regulator, and medium coupling ratio. We present the corresponding phase diagrams and discuss, in particular, the competition between chiral symmetry restoration and the various forms of two flavor color superconductivity.

We present the formalism for a new generation of unquenched quark models for baryons in which the effects of quark‐antiquark pairs are taken into account in an explicit form via a microscopic, QCD‐inspired, quark‐antiquark creation mechanism. The present approach is an extension of the fiux‐tube breaking model of Geiger and Isgur in which now the contribution of quark‐antiquark pairs can be studied for any inital baryon, for any fiavor of the qq pair (not only ss but also uū and dd) and for arbitrary hadron wave functions. The method is illustrated with an application to the spin of the proton and the flavor asymmetry of the nucleon sea.

From the mass term for q‐deformed quark fields, we obtain effective contact interactions of the NJL type. The parameters of the model that maps a system of non‐interacting deformed fields into quarks interacting via NJL contact terms is discussed.

Strange Quark Matter is a proposed state of hadronic matter consisting of up, down and strange quarks. If this state is stable as proposed by various phenomenological models, there will most likely be an experimentally accessible component of strange quark matter particles (strangelets) in the cosmic ray flux. In GLAST the prime signature would be a Λ particle produced in hadronic interaction of the strangelet in the tracker, decaying into a proton and pion with relatively large opening angle. In this contribution we discuss the possibility for the GLAST‐LAT to measure these events and separate them from background.

The Single Transverse — Spin Asymmetry (SSA) is analysed in the framework of the Strongly Correlated Quark Model proposed by author, where the proton spin emerges from the orbital momenta of quark and qluon condensates circulating around the valence quarks. It is shown that dominating factors of appearance of SSA are the orbiting around the valence quarks sea quark and qluon condensates and spin dependent quark‐quark cross sections.

If strange quark matter is absolutely stable, some neutron stars may be strange quark stars. Strange quark stars are usually assumed to have a simple liquid surface. We show that if the surface tension of droplets of quark matter in the vacuum is sufficiently small, droplets of quark matter on the surface of a strange quark star may form a solid crust on top of the strange quark star. This solid crust can significantly modify the predictions for the photon emission for the surface in an observable way.

We present recent analyses of the top quark mass measurement in dileptonic channel. The measurements use 230–360 pb−1 of data collected by CDF and DO experiments. The future prospects are discussed as well.

We give an overview of the physics of the Top quark, from the experimental discovery to the studies of its properties. We review some of the work done on the Electroweak and Flavor Changing couplings associated with the Top quark in the Standard Model and beyond. We will focus on the specific contribution of phycisits working in Mexico and Mexican physicists working abroad.

We address the phase structure of color superconducting quark matter at high quark density. Under the electric and color neutrality conditions there appear various phases as a result of the Fermi surface mismatch among different quark flavors induced by finite strange quark mass; the color‐flavor locked (CFL) phase, the u‐quark superconducting (uSC) phase, the d‐quark superconducting (dSC) phase, the two‐flavor superconducting (2SC) phase, and the unpaired quark matter (UQM). Besides, when the Fermi surface mismatch is large enough to surpass the gap energy, the gapless superconducting phase is expected. We discuss the chromomagnetic instability problem and explore the instability regions on the phase diagram.

We review the contributions of Mexican particle physicists to the description of the properties of hadrons composed of u,d and s quarks. Due to the limitation of space, we focus on the description of strong and electromagnetic interactions.

We calculated the mass spectrum for the hadron by the Diquark Cluster Model and the Two Center Quark Model.

A particular triquark‐diquark configuration has been pointed out as the most likely for pentaquarks as a consequence of the stability of quark clusters under the color‐magnetic interactions. We estimate the masses and the magnetic moments of light pentaquarks in this configuration.

We use the flavor SU(2) NJL model to describe both nuclear and quark matter, and construct phase diagrams to illustrate the phase transitions to normal quark matter (NQM) and color superconducting quark matter (SQM). We calculate the corresponding charge neutral equations of state using the Gibbs conditions to generate the mixed phases.

Starting with a realistic quark model of nucleon structure, in which quarks are strongly correlated with one another within the nucleon, the smallest nuclei, 2He, 3H, 3He and 4He can be constructed by assuming similar correlations with the quarks in neighboring nucleons. Importance of color loops created owing to the closure of quark ends of adjacent nucleons is emphasized. Applying the model to larger nucleon systems reveals the emergence of symmetries at the nuclear level that are isomorphic with those known from the independent‐particle (shell) model.

In this contribution we present new results on electromagnetic transitions between the nucleon ground state and resonances. The calculations have been performed within a relativistic constituent quark model in the framework of Poincare‐invariant quantum mechanics.

A dynamical quark model of hadron and nucleus structure is proposed. In the framework of the model, called the Strongly Correlated Quark Model, quarks and nucleons inside nuclei are arranged in crystal‐like structure.

This is a very short review of quark spin couplings in light baryons. Most of the material comes from reference [6].

We investigate a quark‐meson coupling model of the nuclear matter with a light‐front nucleon model, where the quarks interact with flavor independent contact force. We found results comparable to the ones obtained with a confining interaction.

We use an effective chiral quark theory to describe the single nucleon, the equations of state (EOS) of nuclear matter (NM) and quark matter (QM), and the phase transition from NM to QM at high density. We pay special attention to the effects of the nucleon quark structure on the EOS of NM, and of scalar diquark condensation (color superconductivity) on the EOS of QM.

In this work we study the strange quark matter in an extented version of the Chromodielectric Model (CDM) with a BCS quark pairing implemented, and analyze the superconducting color flavor locked (CFL) phase. We compare the equation of state and the stability of the strange quark matter from QCD in the CFL phase with the superconducting version of the CDM. In the CDM there is a confining potential which originates a dynamical bag constant in the sense that its value depends on the density. Our results indicate that the inclusion in the energy density of the pairing quark interaction allows for an absolutely stable quark matter state even for large potential energies, preventing the metastability of quark matter found in the CDM at high densities.

Recently it has been pointed out that no limits can be put on the scale of fermion mass generation (M) in technicolor models, because the relation between the fermion masses (mf) and M depends on the dimensionality of the interaction responsible for generating the fermion mass. Depending on this dimensionality it may happens that mf does not depend on M at all. We show that exactly in this case mf may reach its largest value, which is almost saturated by the top quark mass. We make few comments on the question of how large can be a dynamically generated fermion mass.

We calculate the tree‐level mass matrices for the neutral and charged lepton sectors, and for the Up and Down quark sectors, in a particular model based on the local gauge group SU (3)c ⊗ SU (3)L ⊗ U (1)X which does not contain particles with exotic electric charges.

Theoretical predictions are given for the light‐flavor sea‐quark distributions in the nucleon including the strange quark ones on the basis of the flavor SU(3) version of the chiral quark soliton model. Careful account is taken of the SU(3) symmetry breaking effects due to the mass difference between the strange and nonstrange quarks, which is the only one parameter necessary for the flavor SU(3) generalization of the model. A particular emphasis of study is put on the light‐flavor sea‐quark asymmetry as well as the particle‐antiparticle asymmetry of the strange quark distributions in the nucleon.

We consider the bubbles of quark matter which survived the confinement phase transition in the universe at high temperature. With the constraint of being neutral and of conservation of baryonic number, we obtain the evolution of the density of quarks of different flavours and of pressure till their contraction stops. On the other hand we find that at low temperature and increasing pressure, a system of ordinary quarks chooses to acquire a strange component. This is what might happen in neutron stars becoming sources of strangelets.

It is shown, in the frame of the model proposed by author, that spin of the proton could be described by the orbital momentum of quark and qluon condensate circulating around valence quarks.

We propose a dynamical model to reproduce Equation of State of Nuclear matter starting from quark degrees of freedom with color at zero temperature and finite density. We solve molecular dynamics with constraint and we use as input a phenomenological potential: the Richardson’s potential. At low densities the quarks condensate into approximately color white cluster (nucleon). At high densities, for quark masses (u,d) of 0.18 GeV we find some evidence for a second order phase transition to Quark Gluon Plasma.

We consider here a Coulomb gauge quark model which includes an explicit construct for a nontrivial vacuum structure in QCD at finite density. Non‐perturbative renormalization of ultraviolet diverges is performed by adding counterterms. The equation of state for u and d quark matter at zero temperature is calculated in the Hartree‐Fock approximation.

The relationship of the quark model to the known chiral properties of QCD is a long‐standing problem in the interpretation of low energy QCD. In particular, how can the pion be viewed as both a collective Goldstone boson quasiparticle and as a valence quark antiquark bound state? A comparison of the many‐body solution of a simplified model of QCD to the constituent quark model demonstrates that the quark model is sufficiently flexible to describe meson hyperfine splitting provided proper renormalization conditions and correct degrees of freedom are employed consistently.

In this paper we breafly present the ATLAS detector potential for the studies of the rare b and t quarks decays.

This is the text of a lecture hold during the VII Mexican School on Particles and Fields. The first part of the lecture has been aimed to advance undergraduate students with little previous knowledge of deep inelastic scattering and it is quite elementary. The second part presents recent published results from the H1 Collaboration related to the structure of the proton.

Strange quark matter (SQM) is a hypothetical multi‐quark ensemble containing almost equal amount of up‐, down‐ and strange quarks. Different experimental techniques looking for the possible existence of SQM as well as its production in the laboratory have been carried out and are reviewed in this contribution. It is focused on examples of terrestrial searches and recent experiments of relativistic particle and heavy‐ion collisions, which try to produce SQM in the laboratory. An outlook on future experimental possibilities is given.