arXiv subjects
Publications and source records attributed to The FOCUS Collaboration.
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 $D^+ \to K^-π^+π^+$. 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 $K^-π^+$ system.
We present a search for a pentaquark decaying strongly to $Ξ^-π^-$ in $γN$ collisions at a center-of-mass energy up to 25 GeV/c^2. Finding no evidence for such a state in the mass range of 1480 MeV/c^2 to 2400 MeV/c^2, we set limits on the yield and on the cross section times branching ratio relative to $Ξ^*(1530)^0$.
Using data collected by the high energy photoproduction experiment FOCUS at Fermilab we performed a Dalitz plot analysis of the Cabibbo favored decay D+ to K-pi+ pi+. 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 Kpi 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 Kpi final state.
We present a search for a pentaquark decaying strongly to $pK_S^0$ in $γN$ collisions at a center-of-mass energy up to 25 GeV/$c^2$. Finding no evidence for such a state in the mass range of 1470 MeV/$c^2$ to 2200 MeV/$c^2$, we set limits on the yield and on the cross section times branching ratio relative to $Σ^*(1385)^\pm$ and $K^*(892)^+$.
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, $D^0\to K^0_SK^0_S K^- π^+$ and $D^0\to K^0_SK^0_S K^+ π^-$, and measure their combined branching fraction relative to $D^0\to \bar{K} ^0π^+π^-$ to be $\frac{Γ(D^0\to K^0_SK^0_SK^{\pm}π^{\mp})}{Γ(D^0\to \bar{K} ^0π^+π^-)}$ = 0.0106 $\pm$ 0.0019 $\pm$ 0.0010. Further, we report new measurements of $\frac{Γ(D^0\to K^0_SK^0_SK^0_S)}{Γ(D^0\to \bar{K} ^0π^+π^-)}$ = 0.0179 $\pm$ 0.0027 $\pm$ 0.0026, $\frac{Γ(D^0\to K^0\bar{K} ^0)}{Γ(D^0\to \bar{K} ^0π^+π^-)}$ = 0.0144 $\pm$ 0.0032 $\pm$ 0.0016, and $\frac{Γ(D^0\to K^0_SK^0_Sπ^+π^-)}{Γ(D^0\to \bar{K} ^0π^+π^-)}$ = 0.0208 $\pm$ 0.0035 $\pm$ 0.0021 where the first error is statistical and the second is systematic.
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 a large sample of D0 to K mu nu and pi mu nu decays collected by the FOCUS photoproduction experiment at Fermilab, we present new measurements of the q^2 dependence for the f+(q^2) form factor. These measured f+(q^2) form factors are fit to common parameterizations such as the pole dominance form and compared to recent unquenched Lattice QCD calculations. We find m_pole = 1.93+-0.05+-0.03 GeV/c^2 for D0 to K mu nu and m_pole = 1.91+0.30-0.15+-0.07 GeV/c^2 for D0 to pi mu nu and f-^{K}(0)/f+^{K}(0) = -1.7+1.5-1.4+-0.3.
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 Γ(D+ > ANTI-K pi mu+ nu)/Γ(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 Γ(D+ > ANTI-K*0 mu+ nu)/Γ(D+ > ANTI-K0 mu+ nu)= 0.594 +/- 0.043 +/- 0.033 and the ratio Γ(D+ > ANTI-K0 mu+ nu)/Γ(D+ > K- pi+ pi+)= 1.019 +/- 0.076 +/- 0.065. Our results show a lower ratio for Γ(D > K* \ell nu})/Γ(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)%.
Using a large sample of Ds to Phi mu nu decays collected by the FOCUS photoproduction experiment at Fermilab, we present new measurements of two semileptonic form factor ratios: rV and r2. We find rV = 1.549 \pm 0.250 \pm 0.145 and r2 = 0.713 \pm 0.202 \pm 0.266. These values are consistent with the rV and r2 form factors measured for the process D+ to K*bar mu nu.
Using a large sample of D+ to K- pi+ mu+ nu decays collected by the FOCUS photoproduction experiment at Fermilab, we present new measurements of two semileptonic form factor ratios: rv and r2. We find rv = 1.504 \pm 0.057 \pm 0.039 and r2 = 0.875 \pm 0.049 \pm 0.064. Our form factor results include the effects of the s-wave interference discussed in a previous paper.
We present the first clear observation of the doubly Cabibbo suppressed decay D+ --> K-K+K+ and the first observation of the singly Cabibbo suppressed decay Ds+ --> K-K+K+. These signals have been obtained by analyzing the high statistics sample of photoproduced charm particles of the FOCUS(E831) experiment at Fermilab. We measure the following relative branching ratios: Gamma(D+ --> K-K+K+)/Gamma(D+ --> K-pi+pi+) = (9.49 +/- 2.17(statistical) +/- 0.22(systematic))x10^-4 and Gamma(Ds+ --> K-K+K+)/Gamma(Ds+ --> K-K+pi+) = (8.95 +/- 2.12(statistical) +2.24(syst.) -2.31(syst.))x10^-3.
We describe a silicon microstrip detector interleaved with segments of a beryllium oxide target which was used in the FOCUS photoproduction experiment at Fermilab. The detector was designed to improve the vertex resolution and to enhance the reconstruction efficiency of short-lived charm particles.
Using a large sample of charm semileptonic decays collected by the FOCUS photoproduction experiment at Fermilab, we present evidence for a small, even spin K- π+ amplitude that interferes with the dominant K*0 component in the K-pi+ mu- nu final state. Although this interference significantly distorts the decay angular distributions, the new amplitude creates only a very small distortion to the observed kaon pion mass distribution when integrated over the other kinematic variables describing the decay. Our data can be described by K*0 interference with either a constant amplitude or broad spin zero resonance.
We describe the various techniques developed in the Fermilab Wideband Experiments, E687 and FOCUS, to reconstruct long-lived states. The techniques all involve modifications to standard tracking techniques and are useful to report for future experiments.
A high statistics sample of photo-produced charm from the FOCUS(E831) experiment at Fermilab has been used to search for direct CP violation in the decays D+->K_S pi+ and D+ -> K_S K+. We have measured the following asymmetry parameters relative to D+->K-pi+pi+: A_CP(K_S pi+) = (-1.6 +/- 1.5 +/- 0.9)%, A_CP(K_S K+) = (+6.9 +/- 6.0 +/- 1.5)% and A_CP(K_S K+) = (+7.1 +/- 6.1 +/- 1.2)% relative to D+->K_S pi+. The first errors quoted are statistical and the second are systematic. We also measure the relative branching ratios: Γ(D+->\bar{K0}pi+)/Γ(D+->K-pi+pi+) = (30.60 +/- 0.46 +/- 0.32)%, Γ(D+->\bar{K0}K+)/Γ(D+->K-pi+pi+) = (6.04 +/- 0.35 +/- 0.30)% and Γ(D+->\bar{K0}K+)/Γ(D+->\bar{K0}pi+) = (19.96 +/- 1.19 +/- 0.96)%.
We describe the algorithm used to identify charged tracks in the fixed-target charm-photoproduction experiment FOCUS.
Using a high statistics sample of photoproduced charm particles from the FOCUS experiment at Fermilab, we compare the lifetimes of neutral D mesons decaying via D0 to K- pi+ and K- K+ to measure the lifetime differences between CP even and CP odd final states. These measurements bear on the phenomenology of D0 - D0bar mixing. If the D0 to K-pi+ is an equal mixture of CP even and CP odd eigenstates, we measure yCP = 0.0342 \pm 0.0139 \pm 0.0074.
Using a high statistics sample of photoproduced charmed particles from the FOCUS experiment at Fermilab (FNAL-E831), we measure the mass splittings of the charmed baryons Sigma_c^0 and Sigma_c^{++}. We find M(Sigma_c^0 - Lambda_c^+) = 167.38 +/- 0.21 +/- 0.13 MeV/c^2 and M(Sigma_c^++ - Lambda_c^+) = 167.35 +/- 0.19 +/- 0.12 MeV/c^2 with samples of 362 +/- 36 and 461 +/- 39 events, respectively. We measure the isospin mass splitting M(Sigma_c^++ - Sigma_c^0) to be -0.03 +/- 0.28 +/- 0.11 Mev/c^2. The first errors are statistical and the second are systematic.