Search for T Violation in Charm Meson Decays

Using data from the FOCUS (E831) experiment, we have searched for T violation in charm meson decays using the four-body decay channels $D^0 \to K^-K^+\pi^-\pi^+$, $D^+ \to K^0_SK^+\pi^-\pi^+$, and $D^+_s \to K^0_SK^+\pi^-\pi^+$. The T violation asymmetry is obtained using triple-product correlations and assuming the validity of the CPT theorem. We find the asymmetry values to be $A_Tviol (D^0) = 0.010 \pm 0.057(stat.) \pm 0.037(syst.)$, $A_Tviol (D^+) = 0.023 \pm 0.062(stat.) \pm 0.022(syst.)$, and $A_Tviol (D^+_s) = -0.036 \pm 0.067(stat.) \pm 0.023(syst.)$. Each measurement is consistent with no T violation. New measurements of the CP asymmetries for some of these decay modes are also presented.Comment: 17 pages,6 figures,submitted to Phys.Lett.

Study of Cabibbo Suppressed Decays of the Ds Charmed-Strange Meson involving a KS

We study the decay of Ds meson into final states involving a Ks and report the discovery of Cabibbo suppressed decay modes Ds -> Kspi-pi+pi+ (179 +/- 36 events) and Ds -> Kspi+ (113 +/-26 events). The branching ratios for the new modes are Gamma(Ds -> Kspi-pi+pi+)/Gamma(Ds -> KsK-pi+pi+) = 0.18 +/- 0.04 +/- 0.05 and Gamma(Ds -> Kspi+)/Gamma(Ds -> KsK+) = 0.104 +/- 0.024 +/- 0.013.Comment: 11 pages, 6 figure

Measurements of Ξc+\Xi_c^{+} Branching Ratios

Using data collected by the fixed target Fermilab experiment FOCUS, we measure the branching ratios of the Cabibbo favored decays $\Xi_c^+ \to \Sigma^+K^-\pi^+$, $\Xi_c^+ \to \Sigma^+ \bar{K}^{*}(892)^0$, and $\Xi_c^+ \to \Lambda^0K^-\pi^+\pi^+$ relative to $\Xi_c^+ \to \Xi^-\pi^+\pi^+$ to be $0.91\pm0.11\pm0.04$, $0.78\pm0.16\pm0.06$, and $0.28\pm0.06\pm0.06$, respectively. We report the first observation of the Cabibbo suppressed decay $\Xi_c^+ \to \Sigma^+K^+K^-$ and we measure the branching ratio relative to $\Xi_c^+ \to \Sigma^+K^-\pi^+$ to be $0.16\pm0.06\pm0.01$. We also set 90% confidence level upper limits for $\Xi_c^+ \to \Sigma^+ \phi$ and $\Xi_c^+ \to \Xi^*(1690)^0(\Sigma^+ K^-) K^+$ relative to $\Xi_c^+ \to \Sigma^+K^-\pi^+$ to be 0.12 and 0.05, respectively. We find an indication of the decays $\Xi_c^+ \to \Omega^-K^{+}\pi^+$ and $\Xi_c^+ \to \Sigma^{*}(1385)^+ \bar{K}^0$ and set 90% confidence level upper limits for the branching ratios with respect to $\Xi_c^+ \to \Xi^-\pi^+\pi^+$ to be 0.12 and 1.72, respectively. Finally, we determine the 90% C.L. upper limit for the resonant contribution $\Xi_c^+ \to \Xi^{*}(1530)^0 \pi^+$ relative to $\Xi_c^+ \to \Xi^-\pi^+\pi^+$ to be 0.10.Comment: 14 pages, 8 figure

Measurement of the Ratio of the Vector to Pseudoscalar Charm Semileptonic Decay Rate \Gamma(D+ > ANTI-K*0 mu+ nu)/\Gamma(D+ > ANTI-K0 mu+ nu)

Using a high statistics sample of photo-produced charm particles from the FOCUS experiment at Fermilab, we report on the measurement of the ratio of semileptonic rates \Gamma(D+ > ANTI-K pi mu+ nu)/\Gamma(D+ > ANTI-K0 mu+ nu)= 0.625 +/- 0.045 +/- 0.034. Allowing for the K pi S-wave interference measured previously by FOCUS, we extract the vector to pseudoscalar ratio \Gamma(D+ > ANTI-K*0 mu+ nu)/\Gamma(D+ > ANTI-K0 mu+ nu)= 0.594 +/- 0.043 +/- 0.033 and the ratio \Gamma(D+ > ANTI-K0 mu+ nu)/\Gamma(D+ > K- pi+ pi+)= 1.019 +/- 0.076 +/- 0.065. Our results show a lower ratio for \Gamma(D > K* \ell nu})/\Gamma(D > K \ell nu) than has been reported recently and indicate the current world average branching fractions for the decays D+ >ANTI-K0(mu+, e+) nu are low. Using the PDG world average for B(D+ > K- pi+ pi+) we extract B(D+ > ANIT-K0 mu+ nu)=(9.27 +/- 0.69 +/- 0.59 +/- 0.61)%.Comment: 15 pages, 1 figur

Study of Hadronic Five-Body Decays of Charmed Mesons Involving KS0K_S^0

We study the decay of $D^0$ and $D^+_s$ mesons into five-body final states including a $K_S^0$ and report the discovery of the decay mode $D_s^+\to K_S^0 K_S^0\pi^+\pi^+\pi^-$. The branching ratio for the new mode is {${\Gamma(D_s^+\to K_S^0K_S^0\pi^+\pi^-\pi^+)} \over {\Gamma(D_s^+\to K_S^0K^-\pi^+\pi^+)}$} = 0.102$\pm0.029\pm$0.029. We also determine the branching ratio of {${\Gamma(D^0\to K_S^0\pi^+\pi^+\pi^-\pi^-)} \over {\Gamma(D^0 \to K_S^0\pi^+\pi^-)}$} = 0.095$\pm0.005\pm$0.007 as well as an upper limit for {${\Gamma(D^0\to K_S^0K^-\pi^+\pi^+\pi^-)} \over {\Gamma(D^0\to K_S^0\pi^+\pi^+\pi^-\pi^-)}$} $<$ 0.054 (90% CL). An analysis of the resonant substructure for $D^0 \to K_S^0\pi^+\pi^+\pi^-\pi^-$ is also performed

Measurement of the branching ratio of the decay D^0 -> \pi^-\mu^+\nu relative to D^0 -> K^-\mu^+\nu

We present a new measurement of the branching ratio of the Cabibbo suppressed decay D^0\to \pi^-\mu^+\nu relative to the Cabibbo favored decay D^0\to K^-\mu^+\nu and an improved measurement of the ratio |\frac{f_+^{\pi}(0)}{f_+^{K}(0)}|. Our results are 0.074 \pm 0.008 \pm 0.007 for the branching ratio and 0.85 \pm 0.04 \pm 0.04 \pm 0.01 for the form factor ratio, respectively.Comment: 13pages, 3 figure

A Non-parametric Approach to Measuring the \kpi{} Amplitudes in \dpkkpi{} Decay

Using a large sample of \dpkkpi{} decays collected by the FOCUS photoproduction experiment at Fermilab, we present the first non-parametric analysis of the \kpi{} amplitudes in \dpkkpi{} decay. The technique is similar to the technique used for our non-parametric measurements of the \krzmndk{} form factors. Although these results are in rough agreement with those of E687, we observe a wider S-wave contribution for the \ksw{} contribution than the standard, PDG \cite{pdg} Breit-Wigner parameterization. We have some weaker evidence for the existence of a new, D-wave component at low values of the $K^- \pi^+$ mass.Comment: 13 pages 3 figure

Measurements of Six-Body Hadronic Decays of the D^0 Charmed Meson

Using data collected by the FOCUS experiment at Fermilab, we report the discovery of the decay modes D^0 --> K- pi+ pi+ pi+ pi- pi- and D^0 --> pi+ pi+ pi+ pi- pi- pi-. With a sample of 48 +/- 10 reconstructed D^0 --> K- pi+ pi+ pi+ pi- pi- decays and 149 +/- 17 reconstructed D^0 --> pi+ pi+ pi+ pi- pi- pi- decays, we measure the following relative branching ratios: ${\Gamma (D^0 \to K^- \pi^+ \pi^+ \pi^+ \pi^- \pi^-) / \Gamma (D^0 \to K^- \pi^+ \pi^+ \pi^-)} = (2.70 \pm 0.58 \pm 0.38) \times 10^{-3}$ ${\Gamma (D^0 \to \pi^+ \pi^+ \pi^+ \pi^- \pi^- \pi^-) / \Gamma (D^0 \to K^- \pi^+ \pi^+ \pi^-)} = (5.23 \pm 0.59 \pm 1.35) \times 10^{-3}$ ${\Gamma (D^0 \to \pi^+ \pi^+ \pi^+ \pi^- \pi^- \pi^-) / \Gamma (D^0 \to K^- \pi^+ \pi^+ \pi^+ \pi^- \pi^-)} = 1.93 \pm 0.47 \pm 0.48$ The first errors are statistical and the second are systematic. The branching fraction of the Cabibbo suppressed six-body decay mode is measured to be a factor of two higher than the branching fraction of the Cabibbo favored six-body decay mode.Comment: To be submitted to Phys. Lett.

Application of Genetic Programming to High Energy Physics Event Selection

We review genetic programming principles, their application to FOCUS data samples, and use the method to study the doubly Cabibbo suppressed decay D+ -> K+ pi+ pi- relative to its Cabibbo favored counterpart, D+ -> K- pi+ pi+. We find that this technique is able to improve upon more traditional analysis methods. To our knowledge, this is the first application of the genetic programming technique to High Energy Physics data.Comment: 39 page

The K−π+K^-\pi^+ S-wave from the D+→K−π+π+D^+ \to K^-\pi^+\pi^+ decay

Using data from FOCUS (E831) experiment at Fermilab, we present a model independent partial-wave analysis of the $K^-\pi^+$ S-wave amplitude from the decay $D^+ \to K^-\pi^+\pi^+$. The S-wave is a generic complex function to be determined directly from the data fit. The P- and D-waves are parameterized by a sum of Breit-Wigner amplitudes. The measurement of the S-wave amplitude covers the whole elastic range of the $K^-\pi^+$ system.Comment: 13 pages, 9 figures, submitted to Physics Letters