We show that the oblique electroweak parameter S receives a small positive contribution when sterile neutrinos or vector doublet leptons mix with their sequential counterparts. For vector triplet leptons the contribution is of similar size and is positive but for a small region in parameter space. © 1992.

G BHATTACHARYYA

A RAYCHAUDHURI

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University of Calcutta (informally known as Calcutta University or CU) is a collegiate public state university located in Kolkata, West Bengal, India.&nbsp;Within India it is recognized as a &quot;Five-Star University&quot; and accredited &quot;A&quot; Grade by National Assessment and Accreditation Council.

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The University of Calcutta has secured the Fifth position among the Universities of India in the prestigious &quot;Indian University Ranking 2019&quot; list, released by the NIRF of the Ministry of Human Resource Development, Government of India.

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It was established on 24 January 1857, and was one of the first institutions in Asia to be established as a multidisciplinary and Western-style university. Its alumni and faculty include several heads of state, heads of government, social reformers, prominent artists, only academy award winner and Dirac medal winner in India, many Fellows of the Royal Society and five Nobel laureates as of 2019 which is highest in South Asia.

University Of Calcutta

Probing exotic leptons through oblique parameters

Physics Letters B

Oblique electroweak parameters S, T, and U, defined so as to be nonvanishing only for physics beyond the standard model, are determined by direct use of high-statistics data from the CERN e+e- collider LEP at different energy points around the Z peak. Additional information from related electroweak measurements are used as constraints. The results are S=-0.76±0.71, T=-0.70±0.49, and U=-0.11±1.07. The consequent restrictions on extra fermion generations and an extra neutral gauge boson are discussed. © 1992 The American Physical Society.

Physical Review D

Oblique electroweak corrections and new physics

We have studied the bounds on mixing angles of fermions with their exotic partners which may stem from different possibilities of new physics. The tree level effects of mixing have been taken care of by a modification of the effective vector and axial-vector couplings of Z to the fermions. The radiative corrections arising from new physics of exotic fermions are assumed to be negligible; as a result the rho parameter and the effective sin2 theta-w are calculated within the framework of the Standard Model. Mixing angles have been treated as free parameters during simultaneous fits to the combined data of cross-sections and lepton asymmetries from the four LEP experiments which have collected over 550,000 Z0 decays in 1990. Fitted values of mixing angles and the upper bounds at 90% C. L. are discussed.

Journal	Data powered by TypesetPhysics Letters B
Publisher	Data powered by TypesetELSEVIER SCIENCE BV
ISSN	0370-2693
Open Access	Yes