New physics solutions for RDR_D and RD∗R_{D^*}

Recent measurements of $R_{D^*}$ have reduced tension with the Standard Model prediction. Taking all the present data into account, we obtain the values of the Wilson coefficients of each new physics four-fermion operator of a given Lorentz structure. We find that the combined data rule out most of the solutions based on scalar/pseudoscalar operators. By studying the inter-relations between different solutions, we find that there are only four allowed solutions, which are based on operators with $(V-A)$, linear combination of $(V-A)$ and $(V+A)$, tensor and linear combination of scalar/pseudoscalar and tensor structure. We demonstrate that the need for new physics is driven by those measurement of $R_D$ and $R_{D^*}$ where the $\tau$ lepton is not studied. Further, we show that new physics only in $b\rightarrow c\,\mu\,\bar{\nu}$ is not compatible with the full set of observables in the decays $B\rightarrow Dl\bar{\nu}$ and $B\rightarrow D^*l\bar{\nu}$.Comment: 16 pages, 1 figure (Accepted for publication in JHEP

Estimation of TFP growth:a semiparametric smooth coefficient approach

This article uses a semiparametric smooth coefficient model (SPSCM) to estimate TFP growth and its components (scale and technical change). The SPSCM is derived from a nonparametric specification of the production technology represented by an input distance function (IDF), using a growth formulation. The functional coefficients of the SPSCM come naturally from the model and are fully flexible in the sense that no functional form of the underlying production technology is used to derive them. Another advantage of the SPSCM is that it can estimate bias (input and scale) in technical change in a fully flexible manner. We also used a translog IDF framework to estimate TFP growth components. A panel of U.S. electricity generating plants for the period 1986–1998 is used for this purpose. Comparing estimated TFP growth results from both parametric and semiparametric models against the Divisia TFP growth, we conclude that the SPSCM performs the best in tracking the temporal behavior of TFP growth

Evaluating the environmental Kuznets curve

We examine the empirical evidence for an environmental Kuznets curve using a semiparametric smooth coefficient regression model that allows us to incorporate flexibility in the parameter estimates, while maintaining the basic econometric structure that is typically used to estimate the pollution-income relationship. This allows us to assess the sensitivity to parameter heterogeneity of typical parametric models used to estimate the relationship between pollution and income, as well as identify why the results from such models are seldom found to be robust. Our results confirm that the resulting relationship between pollution and income is fragile; we show that the estimated pollution-income relationship depends substantially on the heterogeneity of the slope coefficients and the parameter values at which the relationship is evaluated. Different sets of parameters obtained from the semiparametric model give rise to many different shapes for the pollution-income relationship that are commonly found in the literature

New Physics solutions for b→c τ νˉb\rightarrow c\,\tau\,\bar{\nu} anomalies after Moriond 2019

At Moriond 2019, Belle collaboration has announced new measurements on the flavour ratios $R_D - R_{D^*}$ which are consistent with their Standard Model predictions within $1.2\sigma$. After inclusion of these measurements, the global tension in $R_D - R_{D^*}$ has reduced from $4.1\sigma$ to $3.1\sigma$ which is still significant. The measurements of these ratios indicate towards the violation of lepton flavor universality in $b\rightarrow c\,l\,\bar{\nu}$ decay. Assuming new physics in $b\rightarrow c\,\tau\,\bar{\nu}$ transition, we have done a global fit to all available data in this sector to identify the allowed new physics solutions. We find that there are seven allowed new physics solutions which can account for all measurements in $b\rightarrow c\,\tau\,\bar{\nu}$ transition. We show that a simultaneous measurement of the $\tau$ polarization fraction and forward-backward asymmetry in $B\rightarrow D\,\tau\,\bar{\nu}$, the zero crossing point of forward backward asymmetry in $B\rightarrow D^*\tau\bar{\nu}$ and the branching ratio of $B_c\rightarrow \tau\,\bar{\nu}$ decay can distinguish these seven new physics solutions if they can be measured with a required precision.Comment: 6 pages, 1 figure, Contribution to proceedings of Workshop on Frontiers in High Energy Physics 2019 (FHEP 2019), 14-17 Oct 2019, Hyderabad, Telangana, India. arXiv admin note: text overlap with arXiv:1909.0284