arXiv subjects

J. Pasupathy

Publications and source records attributed to J. Pasupathy.

8 recordsLinked to original sources

arXiv2025

Resolution of spin crisis, and notes on the Bjorken sum rule, anomaly and constituent quark

It is shown that the widely used parton model expression for $ g_1$ in polarized proton-lepton scattering is incorrect as it ignores gluon-quark spin entanglement. Therefore, there is no spin crisis. A brief summary of results of the theoretical evaluation of non-octet axial vector current renormalization constants and anomaly -anomaly vacuum correlator is given. It suggests that anomaly plays an important role in the transformation of current quarks to constituent quarks and chiral symmetry breaking.

hep-ph↗

arXiv2009

Axial and pseudoscalar current correlators and their couplings to eta and etaprime mesons

Correlators of singlet and octet axial currents, as well as anomaly and pseudoscalar densities have been studied using QCD sum rules. Several of these sum rules are used to determine the couplings f^8_eta, f^0_eta, f^8_etaprime and f^0_etaprime. We find mutually consistent values which are also in agreement with phenomenological values obtained from data on various decay and production rates. While most of the sum rules studied by us are independent of the contributions of direct instantons and screening correction, the singlet-singlet current correlator and the anomaly-anomaly correlator improve by their inclusion.

hep-ph↗

arXiv2005

The derivative of the topological susceptibility at zero momentum and an estimate of $η'$ mass in the chiral limit

The anomaly-anomaly correlator is studied using QCD sum rules. Using the matrix elements of anomaly between vacuum and pseudoscalars $π, eta$ and $η'$, the derivative of correlator $chi'(0)$ is evaluated and found to be $\approx 1.82 \times 10^{-3}$ GeV$^2$. Assuming that $χ'(0)$ has no significant dependence on quark masses, the mass of $η'$ in the chiral limit is found to be $\approx$723 MeV. The same calculation also yields for the singlet pseudoscalar decay constant in the chiral limit a value of $\approx 178$ MeV.

hep-ph↗

arXiv2003

Axial Vector Current Matrix Elements and QCD Sum Rules

The matrix element of the isoscalar axial vector current, $\bar{u}γ_μγ_5u + \bar{d}γ_μγ_5d $, between nucleon states is computed using the external field QCD sum rule method. The external field induced correlator, $<0|\bar{q}γ_μγ_5q|0>$, is calculated from the spectrum of the isoscalar axial vector meson states. Since it is difficult to ascertain, from QCD sum rule for hyperons, the accuracy of validity of flavour SU(3) symmetry in hyperon decays when strange quark mass is taken into account, we rely on the empirical validity of Cabbibo theory to dertermine the matrix element $\bar{u}γ_μγ_5 u + \bar{d}γ_μγ_5 d - 2 \bar{s}γ_μγ_5 s$ between nucleon states. Combining with our calculation of $\bar{u}γ_μγ_5 u + \bar{d}γ_μγ_5 d$ and the well known nucleon $β$-decay constant allows us to determine $< p,s| {4/9}\bar{u}γ_μγ_5 u + {1/9}\bar{d}γ_μγ_5 d + {1/9}\bar{s}γ_μγ_5 s |p, s>$ occuring in the Bjorken sum rule. The result is in reasonable agreement with experiment. We also discuss the role of the anomaly in maintaining flavour symmetry and validity of OZI rule.

hep-ph↗

arXiv2001

Higgs Mass in the Standard Model from Coupling Constant Reduction

Plausible interrelations between parameters of the standard model are studied. The empirical value of the top quark mass, when used in the renormalization group equations, suggests that the ratio of the colour SU(3) gauge coupling $g_3$, and the top coupling $g_t$ is independent of the renormalization scale. On the other hand, variety of top-condensate models suggest that the Higgs self-coupling $λ$ is proportional to $g_t^2$. Invoking the requirement that the ratio $λ(t)/g_t^2(t)$ is independent of the renormalization scale $t$, fixes the Higgs mass. The pole mass of the Higgs [which differs from the renormalization group mass by a few percent] is found to be $\sim 154$ GeV for the one-loop equations and $\sim 148$ GeV for the two-loop equations.

hep-ph↗

arXiv2000

A Calculation of Higgs Mass in the Standard Model

The assumption that the ratio of the Higgs self-coupling to the square of its yukawa coupling to the top is (almost) independent of the renormalization scale fixes the Higgs mass within narrow limits at m=160 GeV using only the values of gauge couplings and top mass.

hep-ph↗

arXiv1997

PCAC in Nuclear Medium and the Lovelace-Shapiro-Veneziano formula

A simple way to enforce the Adler zero condition for pion amplitudes in the nuclear medium is to use the Lovelace quantization condition but with modified Regge Slope $α'$ This latter is related to change in the gluon condensate. Increasing nuclear density leads to a relative increase in the Regge Slope $α'$ Denoting this increase by a scale factor $λ$, the drop in the $ρ$-mass, $Δ-N$ mass difference, increase in $ππ$ scattering length, decrease of pion decay constant etc. are simply related to $λ$.

nucl-th↗

arXiv1994

Calculation of $ $ from QCD sum rule and the neutron-proton mass difference

The proton matrix element of the isovector-scalar density, $ /2M_p$, is calculated by evaluating the nucleon current correlation function in an external isovector-scalar field using the QCD sum-rule method. In addition to the usual chiral and gluon condensates of the QCD vacuum, the response of the chiral condensates to the external isovector field enters the calculation. The latter is determined by two independent methods. One relates it to the difference between the up and down quark chiral condensates and the other uses the chiral perturbation theory. To first order in the quark mass difference $δm=m_d-m_u$, the non-electromagnetic part of the neutron-proton mass difference is given by the product $δm /2M_p$; the resulting value is in reasonable agreement with the experimental value.

hep-ph↗