Study of $\ep\en$ Collisions in the 1.5-3 Gev C.M. Energy Region Using Isr at \babar

TL;DR

This paper presents a preliminary analysis of low-energy electron-positron collision data using ISR at BaBar, demonstrating competitive results and potential for precise measurements relevant to muon g-2 studies.

Contribution

It introduces a novel analysis of ISR data at BaBar for low-energy collisions, enabling improved cross section measurements with reduced normalization uncertainties.

Findings

Results are competitive with previous experiments in the 1.4-3.0 GeV range.

Data can be used to measure the energy dependence of R, impacting muon g-2 calculations.

The analysis reduces normalization uncertainties compared to earlier measurements.

Abstract

A preliminary analysis of low-energy $\ep\en$ collision data produced via initial state radiation (ISR) has been performed using 22 $fb^{-1}$ of \babar \~data. The selection of data samples corresponding to the $\mumu$, $\pipi$, $\kk$, $p \bar p$, $\kk\pi^0$, 3$\pi$, 4$\pi$, 5$\pi$, 6$\pi$, 7$\pi$ final states accompanied by the emitted ISR hard photon has been demonstrated. The invariant mass of the hadronic final state defines the effective collision c.m. energy, and so \babar ISR data can be compared to the relevant direct $\ep\en$ measurements. The resulting distributions are already competitive with DCI and ADONE data in the 1.4-3.0 GeV energy range. In particular, they do not suffer from the relative normalization uncertainties observed for certain reactions when results from different experiments are combined. Eventually, such data may be used to measure the energy dependence of R, the ratio of the $\ep\en\to hadrons$ and $\ep\en\to\mumu$ cross sections, in the low-energy regime where precise measurements will have an impact on the interpretation of the new $(g-2)_{\mu}$ measurements.