Charm Meson Spectra in e^+e^- Annihilation at 10.5 GeV c.m.e

TL;DR

This work measures charm-hadron momentum spectra in non-resonant $e^+e^-$ annihilation at ${\sqrt{s}}\approx 10.5$ GeV with the CLEO II.V detector, focusing on $D^+$, $D^0$, $D^{*+}$, and $D^{*0}$ while excluding $B$-decay products. It uses multiple decay channels, mass-distribution fits, and two independent Monte Carlo samples to extract raw yields, correct for detection efficiency, and form $d\sigma/dx_p$ with robust systematic checks. The $D^0$ spectrum is used to tune JETSET fragmentation parameters, achieving reasonable reproduction of the $D^{*}$ spectra and offering constraints on nonperturbative charm fragmentation at this energy scale. The results provide high-precision, shape-focused fragmentation information that informs PQCD tests, evolution equations, and Monte Carlo modeling for heavy-flavor production in both $e^+e^-$ and hadron-hadron collisions.

Abstract

Using the CLEO detector at the Cornell Electron-positron Storage Ring, we have measured the scaled momentum spectra, dsigma/dx_p, and the inclusive production cross sections of the charm mesons D+, D0, D*+, and D*0 in e+e- annihilation at about 10.5 GeV center of mass energy, excluding the decay products of B mesons. The statistical accuracy and momentum resolution are superior to previous measurements at this energy.

Figures (25)

• Figure 1: Resolution in $x_p$ for the $D^0$$\rightarrow$$K^-$$\pi^+$ channel. All momenta.
• Figure 2: Examples of $M_{cand}$ distribution for two $D^{\star+}$ decay channels and one of the $D^{\star0}$ channels analyzed. (a) $D^{\star+}$$\rightarrow$($K^-$$\pi^+$)$\pi^+$. (b) $D^{\star+}$$\rightarrow$($K^-$$\pi^+$$\pi^+$$\pi^-$)$\pi^+$. (c) $D^{\star0}$$\rightarrow$($K^-$$\pi^+$$\pi^+$$\pi^-$)$\pi^0$. They show the $M_{cand}$ distribution for $Q$ in the $D^{\star+}$ signal region and for $Q$ in the $D^{\star+}$ side bands.
• Figure 3: (a) Overlay of $D^0$ spectra (data) from double Gaussian and TAGMC shape signal fitting; (b) fractional difference of the two spectra.
• Figure 4: Buildup of the background from its components to fit the $M(K^-{$K^-$}\pi^+{$π^+$})$ distribution. The solid histogram is data. Notice the offset on the yield axis.
• Figure 5: Ratios of data spectrum after double Gaussian shape parameter smoothing to the one obtained without smoothing: (a) $D^+$$\rightarrow$$K^-$$\pi^+$$\pi^+$, (b) $D^0$$\rightarrow$$K^-$$\pi^+$, (c) $D^{\star+}$$\rightarrow$($K^-$$\pi^+$)$\pi^+$.