Jet model with exclusive parton hadron duality

We discuss a model for hadron jets in hard collisions, in which the observed hadrons originate at the end of a purely hadronic cascade. We assume that this hadronic cascade evolves according to the same laws approximately as a parton cascade in QCD. We obtain a simple relation between hadron and parton final states at an almost exclusive level, which allows in many cases to replace partons by hadrons. As application we discuss jet multiplicities at variable resolution, in particular scaling laws, α _s determination and production of axial vector mesons (A ₁ B, ...).     

Formation time of hadrons and density of matter produced in relativistic heavy-ion collisions

Density of matter produced in relativistic heavy-ion collisions depends substantially on the spacetime evolution of the collision and on the formation time of hadrons produced. Interactions of hadrons younger than their formation time are attenuated with respect to their normal values (transparency of hadronic matter for newly formed hadrons). The system of secondary hadrons produced in a heavy-ion collision thus expands as a gas of almost non interacting particles before hadrons reach their formation time. Densities of interacting hadronic matter produced in oxygen-lead and sulphur-lead collisions at 200 GeV/nucleon are estimated as a function of the formation time of hadrons. Uncertainties in our knowledge of the critical temepratureT _c and of the formation time of hadrons τ₀ permit at present three scenarios: an optimistic one (QGP has already been produced in collisions of oxygen and sulphur with heavy ions and will be copiously produced in Lead collisions), a pessimistic one (QGP cannot be produced at 200 GeV/nucleon) and an intermediate one (QGP has not been produced in oxygen and sulphur interactions with heavy ions and will be at best produced only marginally in Pb-collisions). We find the last opinion as most probable.     

New definition for the hadronic contribution to the muon anomalous magnetic moment

A new definition is proposed for the hadronic contribution to the muon anomalous magnetic moment that is based on the inclusion of the effects of vacuum polarization by leptons into the cross section for one-photon annihilation of a lepton pair into hadrons. The formula for the hadronic contribution includes the convolution of the measured cross section for annihilation into hadrons with a certain standard function. This remark concerns radiative correction to this function. A particular form has been proposed for this correction. It has been shown that the use of the new function makes it possible to reduce the uncertainty in such contributions due to radiative correctioins to δa _h/a _h ～ 10^?4.     

On the hadron-parton reciprocity relation

The possibility of an equality between the distributions of partons inside hadrons and the distributions of hadrons in parton fragmentation is studied. It is consistent with existing electroproduction data when the momentum fractions involved are not too small. Implications for current-hadron interactions, large p_T hadronic cross sections and heavy lepton pair production in hadron-hadron collisons are discussed.     

Study of the hadronic component of extensive air showers at the Carpet-2 EAS array

A method for the detection of hadrons with a muon detector at the Carpet-2 EAS array (Baksan Neutrino Observatory, Institute for Nuclear Research, Russian Academy of Sciences) has been described. Events induced by cosmic-ray hadrons have a signature that makes it possible to reliably distinguish them from muons. The characteristics of the hadronic component of extensive air showers with N _e ≥ 10⁵ have been presented.     

A new unitarity bound on e+e− annihilation

Unitarity relates σ_h the electron-positron annihilation cross-section into hadrons and σ_μ the cross-section into muon pairs. This relation provides much more restrictive bounds on σ_h than the simple unitarity bound, for the case in which the hadronic channels dominate the total annihilation cross-section.     

Direct hadron production in ultrarelativistic heavy-ion collisions

Hadrons emitted by the pre-surface layer of a quark-gluon plasma (QGP) before the phase transition into a hadronic gas are considered as possible sources of direct information about QGP. It is shown that if QGP is created in ultrarelativistic heavy-ion collisions, then these hadrons strongly contribute at soft p_t at SpS energy and dominate up to an order of magnitude at LHC energy.     

Chiral partners and their electromagnetic radiation (Ingredients for a systematic in-medium calculation)

It is argued that the chiral partners of the lowest-lying hadrons are hadronic molecules and not three-quark or quark-antiquark states, respectively. As an example the case of a₁ as the chiral partner of the ρ is discussed. Deconfinement-or as a precursor large in-medium widths for hadronic states-is proposed as a natural way to accommodate for the fact that at chiral restoration the respective in-medium spectra of chiral partners must become degenerate. Ingredients for a systematic and self-consistent in-medium calculation are presented with special emphasis on vector-meson dominance which emerges from a recently proposed systematic counting scheme for the mesonic sector including pseudoscalar and vector mesons as active degrees of freedom.     

Measurement of the fragmentation of hadronic systems of different flavour and colour selected by lepton pairs

A lepton-pair trigger was used to select a hadronic system in different flavour and colour states: properties of the transformation of this system into hadrons were measured in terms of charge flow, multiplicity distribution, and fragmentation function. It is observed that, while the effects of flavour are clearly seen, the colour degrees of freedom are not observed in the region of low p_T.     

Thermodynamics of hadrons: Delimiting the temperature

We assume an exponentially rising hadronic mass spectrum ～exp (m/T₀) and consider means for avoiding a limiting temperature at T = T₀. It is possible to do so if the single-particle potential rises at least as fast as m, or if the finite size of hadrons is taken into account, or both. Applications to heavy ion collisions, the early universe and Monte Carlo simulations of the thermodynamics of lattice QCD are mentioned.     

Transverse momentum of hadrons produced in ν and ν interactions on an isoscalar target in BEBC

The average transverse momentum squared, 〈p_⊥²〉, of hadrons is studied as a function of W² and of Q² for ν and $\text{ν}$ interactions on an isoscalar target. An increase of 〈p_⊥²〉 with W² is observed for the hadrons emitted forward in the hadronic c.m.s. The p_⊥ dependence of the fragmentation function is found to factorise from the structure function at fixed W, but does not factorise at fixed Q². Unlike the case of forward-going particles, the 〈p_⊥²〉 of hadrons going backward in the c.m.s. shows no strong dependence on W².     

A study of the nuclear-medium influence on transverse momentum of hadrons produced in deep-inelastic neutrino scattering

The influence of nuclear effects on the transverse momentum (p_T) of neutrino-produced hadrons is investigated using the data obtained with the SKAT propane-freon bubble chamber irradiated in the neutrino beam (with E _v =3–30 GeV) at the Serpukhov accelerator. It has been observed that the nuclear effects cause an enhancement of 〈p _T ² 〉 of hadrons produced in the target fragmentation region at low invariant mass of the hadronic system (2 < W < 4 GeV) and at low energies transferred to the hadrons (2 < ν < 9 GeV). At higher W and ν, no influence of nuclear effects on 〈p _T ² 〉 is observed. Measurement results are compared with predictions of a simple model, incorporating secondary intranuclear interactions of hadrons, which qualitatively reproduces the main features of the data.     

How much charm can \bar PANDA produce?

We consider the production of charmed baryons and mesons in the proton-antiproton binary reactions at the energies of the future $\bar P$ ANDA experiment. To describe these processes in terms of hadronic interaction models, one needs strong couplings of the initial nucleons with the intermediate and final charmed hadrons. Similar couplings enter the models of binary reactions with strange hadrons. For both charmed and strange hadrons we employ the strong couplings and their ratios calculated from QCD light-cone sum rules. In this method finite masses of c and s quarks are taken into account. Employing the Kaidalov??s quark-gluon string model with Regge poles and adjusting the normalization of the amplitudes in this model to the calculated strong couplings, we estimate the production cross-section of charmed hadrons. For $p\bar p \to \Lambda _c \bar \Lambda _c$ it can reach several tens of nb at p _lab = 15 GeV, whereas the cross-sections of ?? _c and D pair production are predicted to be smaller.     

Uncertainties in the hadronic contribution to the QED vacuum polarization

We describe an updated evaluation of the hadronic contribution to the QED vacuum polarization. It is obtained from a dispersion integral over the measured cross section ofe ⁺ e ^?→hadrons.     

The hadronisation of a quark-gluon plasma

We consider two scenarios for the expansion of a quark-gluon plasma. If the evolution is slow enough, the system can remain in equilibrium throughout its entire history up to the freeze-out of a hadron gas; for a very rapid expansion, it may break up into hadrons before or at the confinement transition, without ever going through an equilibrium hadron phase. We compare hadron production rates in the two approaches and show that for a hadronisation temperatureT?200 MeV and baryonic chemical potential μ _B ?500 MeV, their predictions essentially coincide. Present data on strange particle production lead to values in this range and hence cannot provide a distinction between the two scenarios. Pion, nucleon and non-strange meson production seem to require a considerably lower freeze-out temperature and baryonic chemical potential. In the hadron gas picture, this is in accord with the difference in mean free path of the different hadrons in the medium; it suggests a sequential freeze-out, in which strange hadrons stop interacting earlier than non-strange hadrons. In the quark-gluon plasma break-up, the hadronic final state fails to provide the high entropy per baryon observed in non-strange hadron production. The break-up moreover leads to a decrease of the entropy per baryon; hence it must be conceptually modified before it can be considered as a viable hadronisation mechanism.     

Hypothesis of Quark Binding by Condensation of Gluons in Hadrons

Hypothesis of quark binding through condensation of gluons inside hadrons is formulated in the context of a renormalization group procedure for effective particles (RGPEP) in the light-front (LF) Hamiltonian approach to QCD. At the momentum scales of relative motion of hadronic constituents that are comparable with Λ _QCD , the hypothetical boost-invariant constituent dynamics is identified using gauge symmetry. The resulting picture of mesons and baryons closely resembles constituent quark models with harmonic oscillator potentials, shares some features of AdS/QCD, and can be systematically studied using RGPEP in QCD.     

Strong spin-two interaction and general relativity

The concept of short range strong spin-two (f) field (mediated by massive f-mesons) and interacting directly with hadrons was introduced along with the infinite range (g) field in early seventies. In the present review of this growing area (often referred to as strong gravity) we give a general relativistic treatment in terms of Einstein-type (non-abelian gauge) field equations with a coupling constant G_f ? 10³⁸G_N (G_N being the Newtonian constant) and a cosmological term λ_f ?;_μν (?;_μν is strong gravity metric and λ_f ～ 10²⁸ cm^? is related to the f-meson mass). The solutions of field equations linearized over de Sitter (uniformly curves) background are capable of having connections with internal symmetries of hadrons and yielding mass formulae of SU(3) or SU(6) type. The hadrons emerge as de Sitter “microuniverses” intensely curved within (radius of curvature ～10^?14 cm).The study of spinor fields in the context of strong gravity has led to Heisenberg's non-linear spinor equation with a fundamental length ～2 × 10^?14 cm. Furthermore, one finds repulsive spin-spin interaction when two identical spin-$\text{1}\text{2}$ particles are in parallel configuration and a connection between weak interaction and strong gravity.Various other consequences of strong gravity embrace black hole (solitonic) solutions representing hadronic bags with possible quark confinement, Regge-like relations between spins and masses, connection with monopoles and dyons, quantum geons and friedmons, hadronic temperature, prevention of gravitational singularities, providing a physical basis for Dirac's two metric and large numbers hypothesis and projected unification with other basic interactions through extended supergravity.     

Tau reconstruction and identification algorithm

CMS has developed sophisticated tau identification algorithms for tau hadronic decay modes. Production of tau lepton decaying to hadrons are studied at 7 TeV centre-of-mass energy with 2011 collision data collected by CMS detector and has been used to measure the performance of tau identification algorithms by measuring identification efficiency and misidentification rates from electrons, muons and hadronic jets. These algorithms enable extended reach for the searches for MSSM Higgs, Z and other exotic particles.