We present a new measurement of the branching ratio of the Cabibbo suppressed decay D0 → π−μ+ν relative to the Cabibbo favored decayD0 → K−μ+ν and an improved measurement of the ratio |f π + (0)/f K + (0)|. Our results are 0 . 74±0.008±0.007 for the branching ratio and 0 .85± 0.04± 0.04± 0.01 for the form factor ratio, respectively.  2004 Elsevier B.V.

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+ -> 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. (C) 2009 Elsevier B.V. All rights reserved.

Article history: Received 4 June 2009 Received in revised form 24 July 2009 Accepted 24 September 2009 Available online 29 September 2009 Editor: M. Doser PACS: 10. Using data from FOCUS (E831) experiment at Fermilab, we present a model independent partial-wave analysis of the K −π+ S-wave amplitude from the decay D+ → K −π+π+. The S-wave is a generic complex function to be determined directly from the data fit. The Pand 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 −π+ system. © 2009 Elsevier B.V. Open access under CC BY license.

We apply a genetic programming technique to search for the doubly Cabibbo suppressed decays Λc → pKπ− and Ds → KKπ−. We normalize these decays to their Cabibbo favored partners and find BR(Λc → pKπ)/BR(Λc → pKπ+) = (0.05 ± 0.26 ± 0.02)% and BR(Ds → KKπ)/BR(Ds → KKπ+) = (0.52 ± 0.17 ± 0.11)% where the first errors are statistical and the second are systematic. Expressed as 90% confidence levels (CL), we find < 0.46% and < 0.78% respectively. This is the first successful use of genetic programming in a high energy physics data analysis.

We present a new measurement of the branching ratio of the Cabibbo suppressed decay D0 → π−μ+ν relative to the Cabibbo favored decay D0 → K−μ+ν and an improved measurement of the ratio ∣

Using data from the FOCUS (E831) experiment at Fermilab, we present a new measurement of the weak decay-asymmetry parameter αΛc in Λc+→Λπ+ decay. Comparing particle with antiparticle decays, we obtain the first measurement of the CP violation parameter A≡αΛc+αΛ¯cαΛc−αΛ¯c. We obtain αΛc=−0.78±0.16±0.19 and A=−0.07±0.19±0.24 where errors are statistical and systematic.

Using a large sample of D+→K−π+μ+ν decays collected by the FOCUS photoproduction experiment at Fermilab, we present the first measurements of the helicity basis form factors free from the assumption of spectroscopic pole dominance. We also present the first information on the form factor that controls the s-wave interference discussed in a previous paper by the FOCUS Collaboration. We find reasonable agreement with the usual assumption of spectroscopic pole dominance and measured form factor ratios.

Using data collected by the FOCUS experiment at Fermilab, we present a new measurement of the charm semileptonic branching ratio BR(D+ -> rho0 mu+ nu)/BR(D+ -> K*0 mu+ nu). From a sample of 320+-44 and 11372+-161 D+ -> rho0 mu+ nu and D+ -> K*0 mu+ nu events respectively, we find BR(D+ -> rho0 mu+ nu)/BR(D+ -> K*0 mu+ nu)=0.041+-0.006(stat)+-0.004(syst).

Using data from the FOCUS experiment (FNAL-E831), we report on the decay of $D^0$ mesons into final states containing more than one $K^0_S$. We present evidence for two Cabibbo favored decay modes, $D^0\to K^0_SK^0_S K^- \pi^+$ and $D^0\to K^0_SK^0_S K^+ \pi^-$, and measure their combined branching fraction relative to $D^0\to \bar{K} ^0\pi^+\pi^-$ to be $\frac{\Gamma(D^0\to K^0_SK^0_SK^{\pm}\pi^{\mp})}{\Gamma(D^0\to \bar{K} ^0\pi^+\pi^-)}$ = 0.0106 $\pm$ 0.0019 $\pm$ 0.0010. Further, we report new measurements of $\frac{\Gamma(D^0\to K^0_SK^0_SK^0_S)}{\Gamma(D^0\to \bar{K} ^0\pi^+\pi^-)}$ = 0.0179 $\pm$ 0.0027 $\pm$ 0.0026, $\frac{\Gamma(D^0\to K^0\bar{K} ^0)}{\Gamma(D^0\to \bar{K} ^0\pi^+\pi^-)}$ = 0.0144 $\pm$ 0.0032 $\pm$ 0.0016, and $\frac{\Gamma(D^0\to K^0_SK^0_S\pi^+\pi^-)}{\Gamma(D^0\to \bar{K} ^0\pi^+\pi^-)}$ = 0.0208 $\pm$ 0.0035 $\pm$ 0.0021 where the first error is statistical and the second is systematic.

We present a search for a charmed pentaquark decaying strongly to D(∗)−p. Finding no evidence for such a state, we set limits on the cross-section times branching ratio relative to D∗− and D− under particular assumptions about the production mechanism.

We present a K pi mass spectrum analysis of the four-body semileptonic charm decay D+ -> K(-)pi(+)mu(+)nu in the range of 0.65 GeV/c(2) < m(K pi) < 1.5 GeV/c(2). We observe a non-resonant contribution of 5.30 +/- 0.74(-0.96)(+0.99)% with respect to the total D+ -> K(-)pi(+)mu(+)nu decay. For the K*(892)(0) resonance, we obtain a mass of 895.41 +/- 0.32(-0.43)(0.35) MeV/c(2) a width of 47.79 +/- 0.86(-1.06)(+0.32) MeV/c(2) and a Blatt-Weisskopf damping factor parameter of 3.96 +/- 0.54(-0.90)(+1.31) GeV-1. We also report 90% CL upper limits of 4% and 0.64% for the branching ratios Gamma(D+->(K) over bar*(1680)(0)mu(+)nu)/Gamma(D+-> K(-)pi(+)mu(+)nu) and Gamma(D+ -> (K) over bar*(0)(1430)(0)mu(+)nu)/Gamma(D+ -> K(-)pi(+)mu(+)nu), respectively. (c) 2005 Published by Elsevier B.V.

Using a large sample of D+ → K−π+μ+ν decays collected by the FOCUS photoproduction experiment at Fermilab, we present the first measurements of the helicity basis form factors free from the assumption of spectroscopic pole dominance. We also present the first information on the form factor that controls the s-wave interference discussed in a previous paper by the FOCUS collaboration. We find good agreement with the usual assumption of spectroscopic pole dominance and measured form factor ratios.

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.

Using data from the FOCUS experiment (FNAL–E831), we study the decay of Λc+ baryons into final states containing a Λ hyperon. The branching fractions of Λc+ into Λπ+, Λπ+π+π− and ΛK¯0K+ relative to that into pK−π+ are measured to be 0.217±0.013±0.020, 0.508±0.024±0.024 and 0.142±0.018±0.022, respectively. We also report new measurements of Γ(Λc+→Σ0π+)Γ(Λc+→Λπ+)=1.09±0.11±0.19, Γ(Λc+→Σ0π+π+π−)Γ(Λc+→Λπ+π+π−)=0.26±0.06±0.09 and Γ(Λc+→Ξ(1690)0(ΛK¯0)K+)Γ(Λc+→ΛK¯0K+)=0.32±0.10±0.04. Further, an analysis of the subresonant structure for the Λc+→Λπ+π+π− decay mode is presented.

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.

Using data from the FOCUS (E831) experiment, we have searched for T violation in charm meson decays using the four-body decay channels D0 → K−K+π−π+, D+ → K0 S K+π−π+, and D+ s → K 0 S K+π−π+. 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 ATviol(D 0) = 0.010 ± 0.057(stat.) ± 0.037(syst.), ATviol(D +) = 0.023 ± 0.062(stat.) ± 0.022(syst.), and ATviol(D + s ) = −0.036 ± 0.067(stat.)± 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.