Effects of S-wave thresholds

The opening of a new S-wave threshold is frequently accompanied by an abrupt dip in the magnitude of an amplitude for an already-open channel. One familiar example is the behavior of the I=0 S-wave $\pi \pi$ scattering amplitude at $K \bar K$ threshold. Numerous other examples of this phenomenon in recent data are noted, and a unified description of the underlying dynamics is sought.Comment: 17 pages, 2 figures. Two additional references; typographic correction. To be published in Phys. Rev.

Supersymmetric contributions to B -> D K and the determination of angle \gamma

We analyze supersymmetric contributions to B^- -> D^0 K^- and B^- ->\bar{D}^0 K^- processes. We investigate the possibility that supersymmetric CP violating phases can affect our determination for the angle \gamma in the unitary triangle of Cabibbo-Kobayashi-Maskaw mixing matrix. We calculate the gluino and chargino contributions to b--> u(\bar{c}s) and b-->c(\bar{u}s) transitions in a model independent way by using the mass insertion approximation method. We also revise the D^0 - \bar{D}^0 mixing constraints on the mass insertions between the first and second generations of the up sector. We emphasize that in case of negligible D^0 -\bar{D}^0 mixing, one should consider simultaneous contributions from more than one mass insertion in order to be able to obtain the CP asymmetries of these processes within their 1\sigma experimental range. However, with a large D^0-\bar{D}^0 mixing, one finds a significant deviation between the two asymmetries and it becomes natural to have them of order the central values of their experimental measurements.Comment: 20 page

The preliminary lattice QCD calculation of κ\kappa meson decay width

We present a direct lattice QCD calculation of the $\kappa$ meson decay width with the s-wave scattering phase shift for the isospin $I=1/2$ pion-kaon ($\pi K$) system. We employ a special finite size formula, which is the extension of the Rummukainen-Gottlieb formula for the $\pi K$ system in the moving frame, to calculate the scattering phase, which indicates a resonance around $\kappa$ meson mass. Through the effective range formula, we extract the effective $\kappa \to \pi K$ coupling constant $g_{\kappa \pi K} = 4.54(76)$ GeV and decay width $\Gamma = 293 \pm 101$ MeV. Our simulations are done with the MILC gauge configurations with $N_f=2+1$ flavors of the "Asqtad" improved staggered dynamical sea quarks on a $16^3\times48$ lattice at $(m_\pi + m_K) / m_\kappa \approx 0.8$ and lattice spacing $a \approx 0.15$ fm.Comment: To make it concise. arXiv admin note: text overlap with arXiv:1110.1422, but much of v1 text overlap with articles by same and other authors remove

The UTfit Collaboration Average of D meson mixing data: Spring 2012

We derive constraints on the parameters $M_{12}$, $\Gamma_{12}$ and $\Phi_{12}$ that describe $D$ meson mixing using all available data, allowing for CP violation. We also provide posterior distributions and predictions for observable parameters appearing in $D$ physics.Comment: 5 pages, 3 figure

Search for CP Violation in the decays D+ -> K_S pi+ and D+ -> K_S K+

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: \Gamma(D+->\bar{K0}pi+)/\Gamma(D+->K-pi+pi+) = (30.60 +/- 0.46 +/- 0.32)%, \Gamma(D+->\bar{K0}K+)/\Gamma(D+->K-pi+pi+) = (6.04 +/- 0.35 +/- 0.30)% and \Gamma(D+->\bar{K0}K+)/\Gamma(D+->\bar{K0}pi+) = (19.96 +/- 1.19 +/- 0.96)%.Comment: 4 pages, 3 figure

A High Statistics Measurement of the Lambdac+ Lifetime

A high statistics measurement of the Lambdac+ lifetime from the Fermilab fixed-target FOCUS photoproduction experiment is presented. We describe the analysis technique with particular attention to the determination of the systematic uncertainty. The measured value of 204.6 +/- 3.4 (stat.) +/- 2.5 (syst.) fs from 8034 +/- 122 Lambdac -> pKpi decays represents a significant improvement over the present world average.Comment: Submitted to Physical Review Letter

Search for Λc+→pK+π−\Lambda_c^+ \to p K^+ \pi^- and Ds+→K+K+π−D_s^+ \to K^+ K^+ \pi^- Using Genetic Programming Event Selection

We apply a genetic programming technique to search for the double Cabibbo suppressed decays $\Lambda_c^+ \to p K^+ \pi^-$ and $D_s^+ \to K^+ K^+ \pi^-$. We normalize these decays to their Cabibbo favored partners and find $\text{BR}($\Lambda_c^+ \to p K^+ \pi^-$)/\text{BR}($\Lambda_c^+ \to p K^- \pi^+$) = (0.05 \pm 0.26 \pm 0.02)$ and $\text{BR}($D_s^+ \to K^+ K^+ \pi^-$)/\text{BR}($D_s^+ \to K^+ K^- \pi^+$) = (0.52\pm 0.17\pm 0.11)$ 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.Comment: 10 page

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

Measurement of the relative branching ratio BR(\Xi_c^+ \to p^+ K^-\pi^+)\BR(\Xi_c^+ \to \Xi^- \pi^+ \pi^+)

We report the observation of the Cabibbo suppressed decay \Xi_c^+ \to p K^-\pi^+ using data collected with the FOCUS spectrometer during the 1996--97 Fermilab fixed target run. We find a \Xi_c^+ signal peak of 202\pm35 events. We have measured the relative branching ratios BR(\Xi^+_c\to p K^-\pi^+)/BR(\Xi^+_c\to\Xi^-\pi^+\pi^+)= 0.234 \pm 0.047 \pm 0.022 and BR(\Xi^+_c\to p \bar{K}^*(892)^0)/BR(\Xi^+_c\to p K^-\pi^+)= 0.54 \pm 0.09 \pm 0.05 .Comment: 9 pages, 4 figure

Study of the D^0 \to pi^-pi^+pi^-pi^+ decay

Using data from the FOCUS (E831) experiment at Fermilab, we present new measurements for the Cabibbo-suppressed decay mode $D^0 \to \pi^-\pi^+\pi^-\pi^+$. We measure the branching ratio $\Gamma(D^0 \to\pi^+\pi^- \pi^+\pi^-)/\Gamma(D^0 \to K^-\pi^+\pi^-\pi^+) = 0.0914 \pm 0.0018 \pm 0.0022$. 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 $D^0 \to a_1(1260)^+ \pi^-$, accounting for 60% of the decay rate. The second most dominant contribution comes from the decay $D^0 \to \rho(770)^0\rho(770)^0$, 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 $D^0 \to \rho(770)^0\rho(770)^0$, we measure a longitudinal polarization of $P_L = (71 \pm 4\pm 2)$%.Comment: 38 pages, 8 figures. accepted for publication in Physical Review