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 study the decay of Ds+ mesons into final states involving a KS0 and report the discovery of Cabibbo suppressed decay modes Ds+→KS0π−π+π+ (179±36 events) and Ds+→KS0π+ (113±26 events). The branching fraction ratios for the new modes are Γ(Ds+→KS0π−π+π+)Γ(Ds+→KS0K−π+π+)=0.18±0.04±0.05 and Γ(Ds+→KS0π+)Γ(Ds+→KS0K+)=0.104±0.024±0.014.

The narrow dip observed at 1.9 GeV/c2 by the Fermilab experiment E687 in diffractive photoproduction of 3π+3π− is examined. The E687 data are refitted, a mechanism is proposed to explain why this resonance appears as a dip, and possible interpretations are dis-

Using a large sample of photoproduced charm mesons from the FOCUS experiment at Fermilab (FNAL-E831), we observe the decay D → Kπ with a signal yield of 149±31 events compared to a similarly cut sample consisting of 36 760±195 D →Kπ events. We use the observed ratio of D→Kπ to D→Kπ (0.404± 0.085± 0.025)% to obtain a relationship between the D mixing and doubly Cabibbo suppressed decay parameters. 13.25.Ft, 12.15.Ff, 14.40.Lb Typeset using REVTEX 2 The decay D → Kπ [1] may occur either via a doubly Cabibbo suppressed (DCS) decay or through the mixing of the D into D 0 followed by the Cabibbo favored (CF) decay D 0 →Kπ. The näıve expectation for the ratio of DCS to CF branching fractions, RDCS, is tan θC ≃ 0.25%, which may be modified by final state interactions. Contributions from nonperturbative long range interactions make exact calculations of Standard Model charm mixing difficult, but the rate is expected to be less than 10 [2,3]. On the other hand, new physics may enhance mixing [4]. Since Standard Model charm sector CP violation is expected to be small, and current searches report negative results [5], we ignore CP violation in this study. Conversely, recent charm sector mixing searches hint at an effect with a rate of order 10 [6,7]; hence possible mixing effects must be considered. Four groups [7–10] have studied the decay D→Kπ and measured its branching ratio with respect to D→Kπ, but only the most recent result [7] by CLEO II.V is statistically significant. In addition, there is a variation of a factor of five among the measurements with the most recent yielding the most events and the lowest value. We present a high statistics measurement of the branching ratio with more events than any previous experiment and different systematic uncertainties. The data were collected by the FOCUS Collaboration during the 1996-97 Fermilab fixed target run in the Wideband Photon beamline using an upgraded version of the E687 spectrometer [11]. Charm particles are produced in the interaction of high energy photons (〈E〉≈180 GeV) with a segmented BeO target. In the target region, charged particles are tracked by 16 layers of silicon microstrip detectors which provide excellent vertex resolution. The momentum of the charged particles is determined by measuring their deflection in two oppositely polarized, large aperture dipole magnets with five stations of multiwire proportional chambers. Particle identification is determined by three multicell threshold Čerenkov detectors, electromagnetic calorimeters, and muon counters.

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.

Using a large sample of D+→K−K+π+ decays collected by the FOCUS photoproduction experiment at Fermilab, we present the first non-parametric analysis of the K−π+ amplitudes in D+→K−K+π+ decay. The technique is similar to the technique used for our non-parametric measurements of the D+→K¯∗0e+ν form factors. Although these results are in rough agreement with those of E687, we observe a wider S-wave contribution for the K¯0∗0(1430) contribution than the PDG [W.-M. Yao, et al., J. Phys. G 33 (2006) 1], world average mass and width. We have some weaker evidence for the existence of a new, D-wave component at low values of the K−π+ mass.

Using data from the FOCUS (E831) experiment at Fermilab, we present new measurements for the Cabibbo-suppressed decay mode D-0 ->pi(-)pi(+)pi(-)pi(+). We measure the branching ratio Gamma(D-0 ->pi(+)pi(-)pi(+)pi(-))/Gamma(D-0 -> K-pi(+)pi(-)pi(+))=0.0914 +/- 0.0018 +/- 0.0022. An amplitude analysis has been performed, a first for this channel, in order to determine the resonant substructure of this decay mode. The dominant component is the decay D-0 -> a(1)(1260)(+)pi(-), accounting for 60% of the decay rate. The second most dominant contribution comes from the decay D-0 ->rho(770)(0)rho(770)(0), with a fraction of 25%. We also study the a(1)(1260) line shape and resonant substructure. Using the helicity formalism for the angular distribution of the decay D-0 ->rho(770)(0)rho(770)(0), we measure a longitudinal polarization of P-L=(71 +/- 4 +/- 2)%.

Using data collected by the high-energy photoproduction experiment FOCUS at Fermilab we performed a Dalitz plot analysis of the Cabibbo favored decay D+→K−π+π+. This study uses 53653 Dalitz-plot events with a signal fraction of ∼97%, and represents the highest statistics, most complete Dalitz plot analysis for this channel. Results are presented and discussed using two different formalisms. The first is a simple sum of Breit–Wigner functions with freely fitted masses and widths. It is the model traditionally adopted and serves as comparison with the already published analyses. The second uses a K-matrix approach for the dominant S-wave, in which the parameters are fixed by first fitting Kπ scattering data and continued to threshold by Chiral Perturbation Theory. We show that the Dalitz plot distribution for this decay is consistent with the assumption of two-body dominance of the final state interactions and the description of these interactions is in agreement with other data on the Kπ final state.

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 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.

We present a search for a pentaquark decaying strongly to pKS0 in γN collisions at a center-of-mass energy up to 25 GeV. Finding no evidence for such a state in the mass range of 1470MeV/c2 to 2200MeV/c2, we set limits on the yield and on the cross section times branching ratio relative to Σ∗(1385)± and K∗(892)+.

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.

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.