Study of charm production in Z decays

ALEPH Collaboration, The and Barate, R. and Bowdery, Christopher and Finch, Alexander and Foster, Frank and Hughes, Gareth and Jones, Roger and Williams, Mark (2000) Study of charm production in Z decays. The European Physical Journal C (EPJ C) - Particles and Fields, 16 (4). pp. 597-611. ISSN 1434-6052

Abstract

The production rates of D∗± , D∗±s , D± , D0/D¯0 , D±s , and Λ+c/Λ¯−c in Z→cc¯ decays are measured using the LEP I data sample recorded by the ALEPH detector. The fractional energy spectrum of the D∗± is well described as the sum of three contributions: charm hadronisation, b hadron decays and gluon splitting into a pair of heavy quarks. The probability for a c quark to hadronise into a D∗+ is found to be f(c→D∗+)=0.233±0.010(stat.)±0.011(syst.) . The average fraction of the beam energy carried by D∗± mesons in Z→cc¯ events is measured to be ⟨XE(D∗±)⟩cc¯=0.4878±0.0046(stat.)±0.0061(syst.). The D∗± energy and the hemisphere mass imbalance distributions are simultaneously used to measure the fraction of hadronic Z decays in which a gluon splits to a cc¯ pair: n¯g→cc¯=(3.23±0.48(stat.)±0.53(syst.))%. The ratio of the Vector/(Vector+Pseudoscalar) production rates in charmed mesons is found to be PV=0.595±0.045 . The fractional decay width of the Z into cc¯ pairs is determined from the sum of the production rates for various weakly decaying charmed states to be Rc=0.1738±0.0047(stat.)±0.0116(syst.).