H. Banerjee

Currents and the anomalies in chiral gauge theories: Dynamical approach in higher dimensions

Abstract An integral representation for the fermion effective action for chiral gauge theories in d = 2 n space-time dimensions is given which is able to reproduce the mismatch, as suggested by differential geometric methods, between the covariant current and the consistent current. Both types of anomalies (i.e. covariant as well as consistent) can also be calculated without having to evaluate Feynman diagrams or to introduce any local counterterms.

Phase factors, point-splitting regularisation and chiral anomalies

A method is proposed to construct the path-independent form of phase factors pertaining to non-abelian gauge theories. It is found that the original form of the phase factor, as envisaged by Schwinger, is reproduced for a straight path. As an illustration of its use this work is applied, within the framework of point-splitting regularisation, to obtain the familiar axial anomaly in a pure vector gauge theory. Subtleties associated with the treatment of the vector gauge current are also discussed. Finally, the scheme of computations is employed to derive the covariant and consistent anomalies in a non-abelian chiral gauge theory in arbitrary even dimensions.

The role of eikonal approximation in the infrared domain

Abstract We show that the infrared limit of amplitudes for ladder diagram in spinor elecgtrodynamic is given by eikonal approximation correctly upto terms of relative O (|t| 1 2 /s 1 2 ) only if one also makes the ‘small-angle assumption”. Leading corrections to eikonal amplitude contain s -channel poles which do not have Coulomb analogue. For fixed angle scattering we obtain the leading infrared contribution of ladder diagrams.

Invariance of fermion determinant under large gauge transformations

Abstract We argue that in the perturbative framework the natural symmetry of the fermionic determinant is the perturbative gauge transformation (p.g.t.) which differs from the usual gauge transformation of the effective action through the absence of terms independent of the coupling constant. Calculated in a non-perturbative framework appropriate for large gauge function, the sum of these latter terms vanish. In three dimensions the invariance of the full fermion determinant under large gauge transformations is thus ensured due to the invariance under p.g.t. of the Chern-Simons term arising in some perturbative regularisations.

A hydrodynamic model for hadron production ine+−e− annihilation

We consider hadron production ine+-e− annihilation within the framework of a hydrodynamic model. The two key assumptions in the moddel are (i) the initial shape of a Lorentz-contracted disc for the hadronic fireball, with the jet axis providing the necessary longitudinal direction and (ii) the criterion of a critical size of hadronic dimension for the expanding fireball to break up into finalstate particles. Experimental data on charged multiplicity, inclusive distributions, dispersions and particle spectra upto the highest centre-of-mass energy, presently accessible in colliding-beam machines, are explained satisfactorily with only three energy-independent parameters. The present analysis brings out the similarity in the mechanism for hadron production inp-p collision ande+-e− annihilation and attributes the apparent differences to the presence of leading-particle effect in the former process.

Annihilation of e+−e− into hadrons in a hydrodynamic model

Abstract A hydrodynamic model with modified boundary conditions is proposed for the two-jet component of e + −e − annihilation into hadrons. Satisfactory agreement with data for charged multiplicity and inclusive distributions of hadrons is obtained with three energy-independent parameters.

A multi-Regge model for self-consistent pomeron with unit intercept

Abstract We propose a multi-Regge model with vanishing pomeron-pomeron-hadron vertex. The Regge-cut contributions from the inelastic cross section given by the model exactly cancels the contribution from the AFS-cut yielding a self-consistent factorisable pomeron pole with unit intercept. For small multiplicity the production cross sections are asymptotically independent of n and fall off as (ln s ) −2 . The correlation among the secondaries is, as usual, of short range order with the mean multiplicity growing as ln s .

Low energy pion-nucleon scattering

Abstract On the basis of dynamical assumptions implicit in recent derivations of the s-wave π-N scattering lengths we obtain sum rules for the π-N coupling constant and the subtraction constant in the π-N forward dispersion relations. Our estimates for these quantities are in excellent agreement with their recent experimental determination.

A two-component model for hadron production in high-energy pp collisions

SummaryA two-component model for low-PT hadron production in high-energy nondiffractive proton-proton collisions is proposed. The model combines together the ideas of Van Hove and Pokorski with the empirical findings of Basileet al. It consists of a nonscaling component, corresponding to a neutral-central fireball, which hadronizes according to the scheme of the hydrodynamic model, and a scaling component corresponding to two leading clusters which carry the quantum numbers of the proton and yield the leading particles. The charged-particle multiplicity predicted by the model is in good agreement with experimental data all the way up to the CERN collider energy. A comparison of the predictions for inclusive proton distributions with data in the energy range of the ISR and of the pp collider suggests energy dependence of the Van Hove parameters characterizing the recombination of the valence quarks into the observed proton.RiassuntoSi propone un modello a due componenti per produzione adronica a bassoPT in collisioni ad alta energia non diffrattive tra protoni. Il modello combina insieme le idee di Van Hove e Pokorski con le scoperte empiriche di Basileet al. Consiste di una componente non a variazione di scala, che corrisponde ad una sfera di fuoco a corrente neutra che si adronizza secondo lo schema del modello idrodinamico e una componente a variazione di scala che corrisponde a due cluster principali che portano i numeri quantici del protone e generano le particelle principali. La molteplicità di particelle cariche prevista dal modello è in buon accordo con i dati sperimentali fino all’energia del Collider del CERN. Un confronto delle previsioni per distribuzioni inclusive del protone con dati nell’intervallo d’energia dell’ISR e del Collider pp suggerisce la dipendenza d’energia dei parametri di Van Hove che caratterizzano la ricombinazione dei quark di valenza nel protone osservato.РезумеПредлагается двух-компонентная моделя роздения адронов с малыми поперечными импулясами в недифракционных рр соударениях при высоких Энергиях. Предлозенная моделя общединяет идеи ван Хова и Покорского с Эмпирическими данными Базиле и др. Моделя состоит из немасщтабнои компоненты, соответствуушеи неитраляному централяному фаирболу, которыи адронизуется согласно схеме гидродинамическои модели, и масщтабнои компоненты, соответствуушеи двум лидируушим кластерам, которые обладаут квантовыми числами протона и даут лидируушие частицы. Мнозественностя зарязенных частиц, предсказанная Этои моделяу, хорощо согласуется с Эксперименталяными данными при всех Энергиях вплотя до Энергии рр коллаидера в ЦЕРНе. Сравнение предсказании для инклузивных протонных распределении с данными в области Энергии IS R и данными рр коллаидера позволяет предполозитя Энергетическуу зависимостя параметров ван Хова, характеризууших рекомбинациу валентных кварков в наблудаемыи протон.

Transverse momentum cut-off hypothesis in high energy scattering in perturbation theory

Abstract The hypothesis that transverse components of loop momenta are limited in high energy scattering is shown to imply that enhanced contributions from singular scaling in Feynman parameter space analysis should all cancel. Cancellation of singular scaling contributions is verified at the next to the leading-log level in the sixth order for fermion-fermion scattering in a Yang-Mills theory with SU(N)-gauge symmetry.