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Implications of new physics in \lambda_b \to \lambda_c \ell \nu_{\ell} decay processes

by Aishwarya Bhatta

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Submission summary

Authors (as registered SciPost users): Aishwarya Bhatta
Submission information
Preprint Link: scipost_202202_00039v1  (pdf)
Date submitted: Feb. 22, 2022, 9:22 a.m.
Submitted by: Aishwarya Bhatta
Submitted to: SciPost Physics Proceedings
Proceedings issue: 16th International Workshop on Tau Lepton Physics (TAU2021)
Ontological classification
Academic field: Physics
Specialties:
  • High-Energy Physics - Theory
  • High-Energy Physics - Phenomenology
Approaches: Theoretical, Phenomenological

Abstract

Several indications of lepton non-universality ratios, R(D*), R(J/\psi), and the measurements on hadronic and \tau longitudinal polarization in b \to c \ell \bar{\nu} processes have attracted a lot of attention. By considering the most general effective Lagrangian, we carry out a model-independent analysis of the semileptonic \lambda_b decays, to inspect the nature of new physics. We constraint the new physics parameter space by using the chi-square fitting. We study the implications of constrained new couplings on the observable such as branching fractions, forward-backward asymmetries, lepton non-universality parameter, and \lambda_c and lepton longitudinal polarization fractions of the decay modes.

Current status:
Has been resubmitted

Reports on this Submission

Report #1 by Anonymous (Referee 1) on 2022-4-11 (Invited Report)

  • Cite as: Anonymous, Report on arXiv:scipost_202202_00039v1, delivered 2022-04-11, doi: 10.21468/SciPost.Report.4903

Strengths

  • none

Weaknesses

  • if truly a proceeding, no reference to original work or any future work
  • incomplete description of the analysis (likelihood, observables)
  • incorrect treatment of hadronic uncertainties

Report

Given the lack of reference to an original work or future work, I must assume that this is an attempt to shoehorn an analysis into a conference's proceedings. The description of the analysis is incomplete, starting with the lack of chi2 and dof, both of which are needed to compute a p value. (Only their ratio is given). There is no statement on how the "SM uncertainty" is treated, which I assume is the hadronic uncertainty in the observables. The author implicitly uses a scheme for the treatment of theory uncertainties that regularly fails for LFU searches: the hadronic uncertainties are functions of the BSM parameter (here, the Wilson coefficients). This makes their treatment as part of the chi^2 ill-defined. They must be treated as nuisance parameters instead.

Requested changes

Assuming this will be resubmitted as a paper rather than a proceedings article, I recommend to - rework the treatment of the hadronic uncertainties as nuisance parameters with suitable theory constraints (e.g., gaussian priors from lattice QCD) - be clear which parameters are varied in which scenario

From that point forward, one can discuss suitability for a journal.

  • validity: poor
  • significance: low
  • originality: low
  • clarity: low
  • formatting: reasonable
  • grammar: acceptable

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