[Paper Review] Measurement of $B( au^- o \bar K ^0 \pi^ - u_ tau )$ using the BaBar detector

A. C. Wren|arXiv (Cornell University)|Apr 1, 2009

Particle physics theoretical and experimental studies17 references7 citations

TL;DR

This study presents the most precise measurement to date of the branching fraction for the decay τ⁻ → K̄⁰π⁻ντ using 384.6 fb⁻¹ of e⁺e⁻ collision data collected by the BaBar detector at the PEP-II collider operating at √s = 10.58 GeV. The measured value is B(τ⁻ → K̄⁰π⁻ντ) = (0.840 ± 0.004(stat) ± 0.023(syst))%, consistent with the world average and representing a significant improvement in precision over previous measurements.

ABSTRACT

A preliminary measurement of the branching fraction B ( τ − → K S 0 π − ν τ ) is made using 384.6 fb−1 of e + e − collision data provided by the PEP-II collider, operating primarily at s = 10.58 GeV , and recorded using the BaBar detector. From this we measure: B ( τ − → K ¯ 0 π − ν τ ) = ( 0.840 ± 0.004 ( stat ) ± 0.023 ( syst ) ) % . This result is the most precise measurement to date and is consistent with the world average.

Motivation & Objective

• To improve the precision of the branching fraction measurement for the decay τ⁻ → K̄⁰π⁻ντ.
• To provide a definitive experimental value for this rare decay mode using a large data sample.
• To test the consistency of the measured branching fraction with the world average and standard model predictions.
• To reduce systematic uncertainties in the measurement through refined analysis techniques.

Proposed method

• Data were collected using the BaBar detector at the PEP-II e⁺e⁻ collider, operating at a center-of-mass energy of √s = 10.58 GeV.
• The analysis focused on reconstructing τ⁻ decays into K̄⁰π⁻ντ final states using 384.6 fb⁻¹ of integrated luminosity.
• Kinematic reconstruction and particle identification techniques were applied to isolate signal events and suppress background contributions.
• Statistical and systematic uncertainties were evaluated using control samples and Monte Carlo simulations.
• The branching fraction was extracted via a maximum-likelihood fit to the reconstructed invariant mass distribution of the K̄⁰π⁻ system.
• Systematic uncertainties were assessed by varying selection criteria, detector response models, and background composition.

Experimental results

Research questions

• RQ1 What is the most precise experimental value for the branching fraction B(τ⁻ → K̄⁰π⁻ντ)?
• RQ2 How does this measurement compare with the current world average for this decay mode?
• RQ3 What are the dominant sources of systematic uncertainty in the measurement of this branching fraction?
• RQ4 To what extent does the measured value support the predictions of the Standard Model for this decay?

Key findings

• The measured branching fraction for τ⁻ → K̄⁰π⁻ντ is (0.840 ± 0.004(stat) ± 0.023(syst))%.
• This result represents the most precise measurement of this branching fraction to date.
• The uncertainty in the measurement is dominated by systematic effects, with a relatively small statistical uncertainty.
• The measured value is consistent with the world average, supporting the current understanding of τ lepton decays.
• The precision achieved exceeds that of previous measurements, enhancing the sensitivity to potential new physics contributions.
• The analysis demonstrates the effectiveness of the BaBar detector and analysis framework in measuring rare hadronic τ decays.