arXiv subjects

B. Ananthanarayan

Publications and source records attributed to B. Ananthanarayan.

134 records · Page 8Linked to original sources

arXiv1995

Testing the $ΔS=ΔQ$ Rule with Exclusive Semi-Leptonic Kaon Decays

We consider the possibility of violations of the selection rule $ΔS=ΔQ$ at an appreciable level in {\it exclusive} semi-leptonic decays of Kaons. At $Φ$-Factories, intense Kaon beams will be available and will probe among others, the semi-leptonic decays $K_{l4}$ and $K_{l3γ}$ in addition to $K_{l3}$ and could provide novel testing grounds for the $ΔS=ΔQ$ rule. In particular, the branching ratio of $K_{l3γ}$ is non-negligible and could be used to probe new phenomena associated with the violation of this selection rule. Furthermore, we modify certain di-lepton event rate ratios and asymmetries and time asymmetries that have been constructed by Dass and Sarma for di-lepton events from Beon decays to test the $ΔB=ΔQ$ at the $Υ(4S)$, to the Kaon system at the $ϕ(1020)$. We find that the large width of the $K_S$ relative to that of $K_L$ plays an important role in enhancing some of the time asymmetries.

hep-ph↗

arXiv1995

The Non-Minimal Supersymmetric Standard Model with $\tanβ\simeq m_t/m_b$

We consider the supersymmetric extension of the standard model with an additional singlet $S$, the Non-Minimal Supersymmetric Standard Model (NMSSM), in the limit $\tanβ\simeq m_t/m_b$. We embed this model in a supergravity framework with universal boundary conditions and analyze the renormalization group improved tree-level potential. We examine the relationship between this model and the minimial supersymmetric standard model (MSSM), and discuss the novel connections between the two when $\tanβ$ is large. Strong correlations between the free parameters of the nonminimal model are found and the reasons for these discussed. The singlet vacuum expectation value is forced to be large, of the order of $10 TeV$. The radiatively corrected mass of the lightest Higgs boson is found to be $\stackrel{_<}{_\sim} 140 GeV$.

hep-ph↗

arXiv1994

Measurement of the $τ$ electric dipole moment using longitudinal polarization of $e^+e^-$ beams

Certain CP-odd momentum correlations in the production and subsequent decay of $τ$ pairs in $e^+ e^-$ collisions are enhanced significantly when the $e^+$ and $e^-$ beams are longitudinally polarized. These may be used to probe the real and imaginary parts of $d_τ^γ$, the electric dipole moment of the $τ$. Closed-form expressions for these ``vector correlations'' and the standard deviation of the operators defining them due to standard model interactions are presented for the two-body final states of $τ$ decays. If 42\% average polarization of each beam is achieved, as proposed for the tau-charm factories, with equal integrated luminosities for each sign of polarization and a total yield of $2\cdot 10^7$ $τ^+ τ^-$ pairs, it is possible to attain sensitivities for $\vertδ{\rm Re} d_τ^γ\vert$ of $8\cdot 10^{-19}$, $1\cdot 10^{-19}$, $1\cdot 10^{-19}$ $e$ cm respectively and for $\vertδ{\rm Im} d_τ^γ\vert$ of $4\cdot 10^{-14}$, $6\cdot 10^{-15}$, $5\cdot 10^{-16}$ $e$ cm respectively at the three operating center-of-mass energies of 3.67, 4.25 and 10.58 GeV. These bounds emerge when the effects of a posible weak dipole form factor $d_τ^Z$ are negligible as is the case when it is of the same order of magnitude as $d_τ^γ$. Furthermore, in such a polarization experiment where different polarizations are possible, a model-independent disentangling of their individual effects is possible, and a technique to achieve this is described. A strong longitudinal polarization physics programme at the tau-charm factory appears warranted.

hep-ph↗

arXiv1994

Consistency of the Chiral Pion-Pion Scattering Amplitudes with Axiomatic Constraints

The pion-pion scattering amplitudes provided by second-order chiral perturbation theory are confronted with known rigorous constraints derived from the axioms of quantum field theory. We mainly test constraints restricting the $π^0$-$π^0$ $S$- and $D$-wave amplitudes in the unphysical interval $0\leq s\leq 4m_π^2$. These constraints impose significant lower bounds for a linear combination of coupling constants specifying the second order chiral Lagrangian. The accepted value of this combination is consistent with these bounds. The $π^0$-$π^0$ $S$- and $D$-waves are strongly correlated by a set of constraints.

hep-ph↗

arXiv1994

Effect of longitudinal electron polarization in the measurement of the $τ$ weak dipole moment in $e^+e^-$ collisions

We show that certain CP-odd momentum correlations in the production and subsequent decay of tau pairs in $e^+e^-$ collisions get enhanced when the electron beam is longitudinally polarized. Analytic expressions for these correlations are obtained when $τ^+τ^-$ have a ``weak" dipole form factor (WDFF) coupling to $Z$ in the case of two-body decay modes of the $τ$. Expressions of the variance of these correlations due to the standard model interactions are also presented. For $e^+e^-$ collisions at the $Z$ peak, a sensitivity of about $10^{-17} e$ cm for the real part of the $τ$ WDFF and $3\times 10^{-17} e$ cm for the imaginary part of the $τ$ WDFF can be reached using $π$ and $ρ$ channels (which are the most sensitive channels) in $τ$ decay, with $10^6\, Z$'s likely to be available at the SLC at Stanford with $e^-$ polarization of 62\%-75\%.

hep-ph↗

arXiv1994

Weak dipole moment of $τ$ in $e^+e^-$ collisions with longitudinally polarized electrons

It is pointed out that certain CP-odd momentum correlations in the production and subsequent decay of tau pairs in $e^+e^-$ collisions get enhanced when the $e^-$ is longitudinally polarized. Analytic expressions for these correlations are obtained for the single-pion decay mode of $τ$ when $τ^+τ^-$ have a ``weak" dipole form factor (WDFF) coupling to $Z$ . For $e^+e^-$ collisions at the $Z$ peak, a sensitivity of about 1-5$\times 10^{-17}$\mbox{$e$ cm} for the $τ$ WDFF can be reached using a {\em single} $τ^+τ^-$ decay channel, with $10^6\, Z$'s likely to be available at the SLC at Stanford with $e^-$ polarization of 62\%-75\%.

hep-ph↗

arXiv1994

Supersymmetric Models With Tan(beta) Close to Unity

Within the framework of supersymmetric grand unification, estimates of the $b$ quark mass based on the asymptotic relation $m_b \simeq m_τ$ single out the region with $\tanβ$ close to unity, particularly if $m_t(m_t) \stackrel{_<}{_\sim} 170\ GeV$. We explore the radiative breaking of the electroweak symmetry and the associated sparticle and higgs spectroscopy in models with $1 < \tanβ\stackrel{_<}{_\sim} 1.6$. The lightest scalar higgs is expected to have a mass below $100\ GeV$, while the remaining four higgs masses exceed $300\ GeV$. The lower bounds on some of the sparticle masses are within the range of LEP 200.

hep-ph↗

arXiv1993

Zeroing In On the Top Quark, LSP and Scalar Higgs Masses

We estimate the top quark, lightest sparticle (LSP) and scalar higgs masses within a supersymmetric grand unified framework in which $\tanβ\simeq m_t/m_b$ and the electroweak symmetry is radiatively broken. The requirement that the calculated $b$ quark mass lie close to its measured value, together with the cosmological constraint $Ω_{LSP} \approx 1$, fixes the top quark mass to be $m_t(m_t) \approx 170 \pm 15\ GeV$. The LSP (of bino purity $\stackrel{_>}{_\sim} 98\%)$ has mass $\sim 200 - 350\ GeV$. In the scalar higgs sector the CP-odd scalar mass $m_A \stackrel{_<}{_\sim} 220\ GeV$. With $m_A \stackrel{_>}{_\sim} M_Z$, as suggested by the decay $b \rightarrow sγ$, we find $M_Z \stackrel{_<}{_\sim} m_{h^0} (m_{H^0}) \stackrel{_<}{_\sim} 140 (220)\ GeV$ and $120\ GeV \stackrel{_<}{_\sim} m_{H^\pm} \stackrel{_<}{_\sim} 240\ GeV$.

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