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Measurement of the Leptonic Branching Fraction of the Dₛ Meson and Determination of Its Decay Constant


Kelsey, Michael Henderson (1996) Measurement of the Leptonic Branching Fraction of the Dₛ Meson and Determination of Its Decay Constant. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/x5qg-g497.


Between February 1992 and June 1994, the Beijing Spectrometer (BES) experiment collected 24.5 pb⁻¹ of data in e⁺e⁻ collisions at a center of mass energy of 4.03 GeV, above threshold for production of Dₛ⁺Dₛ⁻ meson pairs. In this thesis, these data are searched for Dₛ⁺Dₛ⁻ events by identifying sets of charged tracks consistent with the decay channels Dₛ → Φπ,Φ → K⁺K⁻; Dₛ → K*⁰K,K*⁰ → K⁺π⁻; or Dₛ → K⁰SK,K⁰S → π⁺π⁻. A global maximum-likelihood technique is used, which combines particle identification detector data and a kinematic fit to each decay hypothesis, for maximum sensitivity. A sample of 190 candidates is found in the mass range 1958.5-1978.5 MeV/c², of which 76.9 ± 13.8 are estimated (from a fit to 1097 combinations with 1800 < m < 2015 MeV /c²) to be true e⁺e⁻ → Dₛ⁺Dₛ⁻ events.

This event sample is searched for leptonic decays of the Dₛ meson in the channels Dₛ → µνµ and Dₛ → τντ (with τ → µν̅µντ → eν̅eντ, or τ → πντ). Five candidate decays are found. A likelihood function is formed as a product over the candidate events, where each contributes a sum over all of the leptonic decay channels, weighted according to the likelihoods of the particle identifications and the kinematics of the decay. This likelihood function is maximized with respect to the branching fraction B(Dₛ → µνµ), or the Dₛ pseudoscalar decay constant fDₛ, with the results

B(Dₛ → µνµ) = .75+1.23-.47 (stat) ± .06 (syst) %,

fDₛ = 308+164-189 (stat) ± 12 (syst) MeV.

Comparison of the measured value of fDₛ with other experimental determinations and with a variety of theoretical models is discussed, with implications for constraining those models.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:Physics
Degree Grantor:California Institute of Technology
Division:Physics, Mathematics and Astronomy
Major Option:Physics
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Hitlin, David G.
Thesis Committee:
  • Rutledge, David B. (chair)
  • Kavanagh, Ralph William
  • Porter, Frank C.
  • Wise, Mark B.
  • Hitlin, David G.
Defense Date:21 May 1996
Funding AgencyGrant Number
Department of Energy (DOE)DE-FG03-92-ER40701
Record Number:CaltechTHESIS:04202020-172701960
Persistent URL:
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:13678
Deposited By: Mel Ray
Deposited On:23 Apr 2020 21:54
Last Modified:02 Dec 2020 02:29

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