C.C. Chang

New particle searches

Abstract PETRA, the e + e − collider, has operated at a maximum CM energy of 46.78 GeV. We update our previous results on new particle searches and set significantly better mass limits on some.

Experimental Study of Inclusive Muon Spectra at PETRA

The results of a high-statistics study of inclusive muon spectra at PETRA are reported. Improved mass limits have been obtained for heavy quarks, heavy leptons, and charged Higgs particles. It is shown that the fragmentation properties of b quarks and c quarks are different, with the mean fragmentation variables = 0.75 +- 0.03 +- 0.06, = 0.46 +- 0.02 +- 0.05 and the average semileptonic branching ratio for the B and C hadrons BR(B) = (10.5 +- 1.5 +- 1.3)%, BR(C) = (11.5 +- 1.0 +- 1.7)%.

Study of electromagnetic decay of J/ψ and ψ′ to vector and pseudoscalar

Abstract The electromagnetic decay contributions to J / ψ ( ψ ′ ) → V P , where V and P stand for vector and pseudoscalar meson, respectively, are investigated in a vector meson dominance (VMD) model. We show that J / ψ ( ψ ′ ) → γ ∗ → V P can be constrained well with the available experimental information. We find that this process has significant contributions in ψ ′ → V P and may play a key role in understanding the deviations from the so-called “12% rule” for the branching ratio fractions between ψ ′ → V P and J / ψ → V P . We also address that the “12% rule” becomes very empirical in exclusive hadronic decay channels.

Search for Charged Higgs, Scalar Taus, and a Test of Technicolor Models

Abstract We have used our measurements of final states from e+e− containing an isolated muon and a hadronic or electron shower to search for new spin 0 charged particles. We exclude (95% CL) a supersymmetric partner of the τ with a mass less than 14 GeV/c2. We obtain upper limits on the branching ratio to τvτ for charged Higgs particles or technipions with masses up to 14 GeV/c2. This disagrees with some technicolor model predictions.

Is D-S(J)+ (2632) the first radial excitation of D-S(*)(2112)?

We present a quantitative analysis of the D-sJ(+) (2632) observed by SELEX mainly focusing on the assumption that D-sJ(+) (2632) is the first radial excitation of the 1(-) ground state D-s(*)(2112). By solving the instantaneous Bethe-Salpeter equation, we obtain the mass 2658 +/- 15 MeV for the first excited state, which is about 26 MeV heavier than the experimental value 2632 +/- 1.7 MeV. By means of PCAC and low-energy theorem we calculate the transition matrix elements and obtain the decay widths: Gamma(D-sJ(+) -> D(s)(+)eta) = 4.07 +/- 0.34 MeV, Gamma(D-sJ(+), (DK+)-K-0) similar or equal to Gamma(Gamma(D-sJ(+) -> (D+K0)) = 8.9 +/- 1.2 MeV, and the ratio Gamma(D-sJ(+) -> (DK+)-K-0)/Gamma(D-sJ(+) -> D(s)(+)eta) = 2.2 +/- 0.2 as well. This ratio is quite different from the SELEX data 0.14 +/- 0.06. The summed decay width of those three channels is approximately 21.7 MeV, already larger than the observed bound for the full width (<= 17 MeV). Furthermore, assuming D-sJ(+) (2632) is 1(-) state, we also explore the possibility of S-D wave mixing to explain the SELEX observation. Based on our analysis, we suspect that it is too early to conclude that D-sJ(+)(2632) is the first radial excitation of the 1(-) ground state D-s(*)(2112). More precise measurements of the relative ratios and the total decay width are urgently required, especially for S-D wave mixing. (c) 2005 Elsevier B.V. All rights reserved.

A measurement of the strong coupling constant αs to complete second order

The strong interaction coupling constant αs has been measured with a new method, the planar triple energy correlation in the reaction e+e- → hadrons at center-of-mass energies ranging from 14 GeV to 46.78 GeV. A complete second-order perturbative QCD calculation was used. ΛMS = 110 ± 30 −55+70 MeV is found.

Search for SUSY particles γ̃, ṽ, ẽ, W̃ in electron positron annihilation at 44 GeV

We study the production of single γ, e and μ at high πt using the high energy data of the Mark-J detector at PETRA. We find good agreement with QED. We give mass limits of the SUSY particles γ, v, e and W studying the associated production of W and ẽ and radiative production of pairs of γ or v in three-body reactions.

The production and decay of tau leptons

Abstract A study of τ-lepton production in the CMS energy region from 14 to 46.8 GeV at PETRA is reported. The cross section, the decay branching ratio into μν ν , and the electroweak parameters are determined with a total integrated luminosity of 115 pb −1 .

Search for SUSY particles γ̃, ṽ, ẽ, W̃ in electron positron annihilation at 44 GeV☆

We study the production of single γ, e and μ at high πt using the high energy data of the Mark-J detector at PETRA. We find good agreement with QED. We give mass limits of the SUSY particles γ, v, e and W studying the associated production of W and ẽ and radiative production of pairs of γ or v in three-body reactions.

Search for {SUSY} Particles Photino, Sneutrino, Selectron, Wino in Electron Positron Annihilation at 44-{GeV}

We study the production of single γ, e and μ at high πt using the high energy data of the Mark-J detector at PETRA. We find good agreement with QED. We give mass limits of the SUSY particles γ, v, e and W studying the associated production of W and ẽ and radiative production of pairs of γ or v in three-body reactions.