Bags versus strings: Hadrons in type I and type II superconducting vacua

Two popular models for hadronic structure are bags and strings. Both involve analogies with superconductivity. We claim that the most appropriate analogies are type I superconductors for bags and type II superconductors for strings. The structures of hadrons is somewhat different for the two situations. In principle, and in practice in the real world, it is the similarities which are most important. These include linear confining potentials, linearly rising Regge trajectories and short-distance Coulomb potentials. These are all generic properties of bound states in a superconductor and the main distinctions between bags and strings is under what circumstances these limiting behaviors set in.     

Hadrons in nuclei

Changes of hadronic properties in dense nuclear matter as predicted by theory have usually been investigated by means of relativistic heavy-ion reactions. In this talk I show that observable consequences of such changes can also be seen in more elementary reactions on nuclei. Particular emphasis is put on a discussion of photonuclear reactions; examples are the dilepton production at ≈1 GeV and the hadron production in nuclei at 10–20 GeV photon energies. The observable effects are expected to be as large as in relativistic heavy-ion collisions and can be more directly related to the underlying hadronic changes.     

Hadrons from jets

A dynamical ansatz on the nature of the interaction that binds the constituents into physical hadrons makes it possible to compute perturbatively the spectrum and the quantum numbers of hadrons near the phase space boundary of a QCD jet. Nonperturbative effects are important for less extreme values of the momentum of the detected hadrons. They can be incorporated in the model using the algorithm of the jet calculus.     

Hadrons in medium

In these lectures I first give the motivation for investigations of in-medium properties of hadrons. I discuss the relevant symmetries of QCD and how they might affect the observed hadron properties. I then discuss at length the observable consequences of in-medium changes of hadronic properties in reactions with elementary probes, and in particular photons, on nuclei. Here I put an emphasis on new experiments on changes of the σ- and ω-mesons in medium     

Hadrons in compact stars

We discuss β-equilibrated and charge neutral matter involving hyperons and {ie817-1} condensates within relativistic models. It is observed that populations of baryons are strongly affected by the presence of antikaon condensates. Also, the equation of state including {ie817-2} condensates becomes softer resulting in a smaller maximum mass neutron star     

Hadrons yielded by plasma

We consider nonequilibrium phase transitions of a quark-gluon plasma into hadrons proceeding via deflagration and supersonic condensation. The possible existence of a third phase, i.e. plasma of constitutent quarks is taken into account. New equations of state for hadronic gas are used, which include the proper volume of particles in a thermodynamically consistent way. The yields of hadrons are calculated for various values of the baryon density of the quark-gluon plasma.     

Hadrons in dense QCD

The theoretical foundation of the in-medium hadron properties is discussed from the point of view of the QCD spectral functions. The dynamical models of in-medium hadrons proposed so far are also summarized.     

Sigma Terms of Light-Quark Hadrons

A calculation of the current-quark mass dependence of hadron masses can help in using observational data to place constraints on the variation of nature’s fundamental parameters. A hadron’s σ-term is a measure of this dependence. The connection between a hadron’s σ-term and the Feynman-Hellmann theorem is illustrated with an explicit calculation for the pion using a rainbow-ladder truncation of the Dyson-Schwinger equations: in the vicinity of the chiral limit σ_π = m_π/2. This truncation also provides a decent estimate of σ_ρ because the two dominant self-energy corrections to the ρ-meson’s mass largely cancel in their contribution to σ_ρ. The truncation is less accurate for the ω, however, because there is little to compete with an ω → ρπ self-energy contribution that magnifies the value of σ_ω by ≲25%. A Poincaré-covariant Faddeev equation, which describes baryons as composites of confined-quarks and -nonpointlike-diquarks, is solved to obtain the current-quark mass dependence of the masses of the nucleon and Δ, and thereby σ_N and σ_Δ. This “quark-core” piece is augmented by the “pion cloud” contribution, which is positive. The analysis yields σ_N ≃ 60 MeV and σ_Δ ≃ 50 MeV.     

Charm Hadrons in Dense Matter

The properties of the D and D _s charmed mesons in normal nuclear matter density are studied within a coupled channel approach using a t-channel vector-meson exchange mechanism as driving force. The in-medium scattering amplitudes are obtained by solving the Lippmann?CSchwinger equation including Pauli blocking effects and medium self-energies in a self-consistent way.     

兰州冷却储存环上可开展的强子物理研究

介绍了当前强子物理的研究现状和兰州冷却储存环的能量特点,以及国内强子物理专家的分析和建议。在兰州冷却储存环上,可利用中能轻离子束核反应产生强子激发态研究强子内部夸克态的结构和性质、强子性质随核环境的变化和手征对称破缺与部分恢复。尤其是通过兰州冷却储存环上限能区附近的P＋P反应,研究奇异夸克的不对称性和形状因子,寻找超子激发态和pentaquark的实验证据,发现双重子态的实验事例。 According to both the development on badrons physics and the aspect of Lanzhou cooling storage ring （CSR） and based on the analysis and propositions given by experts in China, we propose some hadrons physics program at CSR. The hadron spectroscopy produced in light nucleus collisions at CSR used to probe the quark and gluon structure of hadrons, to study the modification of the hadron properties in nuclear matter and to investigate the spontaneous breaking of the chiral symmetry and its partial restoration. Especially, the proton-proton collisions at beam energies per proton below 2.8 GeV at CSR should be used to measure the strangeness asymmetry and strange form lector, to probe the existence of hyperon and pentaquarks and to find the evidence for the existence of dibaryon.     

Hadrons with charm and beauty

Zeitschrift für Physik C Particles and Fields - By combining potential models and QCD spectral sum rules (QSSR), we discuss the spectroscopy of the $$(b\bar c)$$ mesons and of the (bcq), (ccq)...     

Weak Neutrino-Lepton Annihilation into Hadrons

An exploratory study of weak neutrino-lepton annihilation into hadrons, v̄_l + l → hadrons is presented. Simple cross-section estimates indicate processes of this type may be observable in a large bubble chamber. We discuss the information one could hope to obtain from such experiments. General formulas for amplitudes and cross sections are given for v̄_l + l → hadrons assuming a point-like V – A interaction. To establish tests of the V – A interaction, we recalculate the annihilation amplitudes assuming a point-like scalar-pseudoscalar or tensor-pseudotensor interaction. The extension to theories with intermediate vector bosons is sketched. We discuss the connection between v̄_l + l → hadrons and e⁺e⁻ → hadrons implied by the conserved vector current hypothesis. We note that in v̄_l + l → rH, K⋆(890), A₁, B creation (these reactions enjoy comparatively large cross sections) the leptonic as well as hadronic couplings of these J = 1 , I = 1/2 or 1 mesons could be determined. A related possibility is the direct creation of new heavy charged J = 1 mesons. The normal J = 1 resonance region could be explored with neutrino energies of the order 500–2000 GeV. For this, and for higher-energy work, a TeV proton accelerator is clearly necessary.     

Hadrons and broken symmetries with WASA-at-COSY

The WASA Detector Facility is an internal experiment at the cooler synchrotron (COSY) in Jülich, Germany. The COSY accelerator provides proton and deuteron beams with momenta up to 3.7 GeV/c giving access to hadron physics including the strange quark sector. The physics program with the WASA detector involves hadron dynamics and hadron structure. Key experiments address fundamental symmetries and symmetry violations via the study of rare and not-so-rare meson decays. From the very first production run, results on the Dalitz plot slope parameter in the isospin violating η → 3π ⁰ decay have been obtained. The 3π ⁰ final state is also used to study meson production mechanisms. Investigations of other decay modes of the η-meson address C, P, and T symmetries and combinations. Higher orders in chiral perturbation theory are probed with the η → π ⁰ decay. The status and plans for studying hadron structure with Dalitz decays of mesons are presented.     

Hadrons in dense and hot matter

Theoretical issues and perspectives of hadronic matter at high baryon density are discussed with focus on the restoration of chiral symmetry and observable consequences.Received: 30 September 2002, Published online: 22 October 2003PACS: 25.75.-q Relativistic heavy-ion collisions - 21.65. + f Nuclear matter     

Hadrons with charmed quarks in matter

We investigate the decay width of excited charmonium states at finite nuclear density with simultaneous modification of both D- and -mesons in nuclear matter. The strongest effect is found for the -meson. The medium modification can be detected by dilepton spectroscopy as substantial broadening and anomalous absorption.Received: 30 September 2002, Published online: 22 October 2003PACS: 13.25.Gv Decays of , , and other quarkonia - 14.40.Lb Charmed mesons - 14.65.Dw Charmed quarks - 24.85. + p Quarks, gluons, and QCD in nuclei and nuclear processes     

Issues and Opportunities in Exotic Hadrons

The last few years have been witness to a proliferation of new results concerning heavy exotic hadrons.Experimentally, many new signals have been discovered that could be pointing towards the existence of tetraquarks,pentaquarks, and other exotic configurations of quarks and gluons. Theoretically, advances in lattice field theory techniques place us at the cusp of understanding complex coupled-channel phenomena, modelling grows more sophisticated, and effective field theories are being applied to an ever greater range of situations. It is thus an opportune time to evaluate the status of the field. In the following, a series of high priority experimental and theoretical issues concerning heavy exotic hadrons is presented.