Search results for "Flavor-changing neutral current"
showing 10 items of 14 documents
Search for flavor changing neutral currents in decays of top quarks
2011
We present a search for flavor changing neutral currents in decays of top quarks. The analysis is based on a search for ttbar -> l'null + jets (l, l' = e, mu) final states using 4.1 fb^-1 of integrated luminosity of ppbar collisions at sqrt(s) = 1.96 TeV. We extract limits on the branching ratio B(t -> Zq) (q = u, c quarks), assuming anomalous tuZ or tcZ couplings. We do not observe any sign of such anomalous coupling and set a limit of B < 3.2% at 95% C.L.
Observation of Photon Polarization in theb→sγTransition
2014
This Letter presents a study of the flavor-changing neutral current radiative $B^{\pm} \to K^{\pm}\pi^{\mp}\pi^{\pm}\gamma$ decays performed using data collected in proton-proton collisions with the LHCb detector at $7$ and $8\,$TeV center-of-mass energies. In this sample, corresponding to an integrated luminosity of $3\,\text{fb}^{-1}$, nearly $14\,000$ signal events are reconstructed and selected, containing all possible intermediate resonances with a $K^{\pm}\pi^{\mp}\pi^{\pm}$ final state in the $[1.1, 1.9]\,$GeV/$c^{2}$ mass range. The distribution of the angle of the photon direction with respect to the plane defined by the final-state hadrons in their rest frame is studied in interva…
Search for flavor-changing neutral current and lepton-flavor violating decays of D-0 -> l(+)l(-)
2004
We report on a search for the flavor-changing neutral current decays $\Dz\to e^+e^-$ and $\Dz\to\mu^+\mu^-$, and the lepton-flavor violating decay $\Dz\to e^\pm\mu^\mp$. The measurement is based on $122 {fb}^{-1}$ of data collected by the \babar detector at the PEP-II asymmetric $e^+e^-$ collider. No evidence is found for any of the decays. The upper limits on the branching fractions, at the 90 % confidence level, are $1.2\times 10^{-6}$ for $\Dz\to e^+e^-$, $1.3\times 10^{-6}$ for $\Dz\to\mu^+\mu^-$, and $8.1\times 10^{-7}$ for $\Dz\to e^\pm\mu^\mp$.
Updated Search for the Flavor-Changing Neutral-Current Decay D^0 \to {\mu} + {\mu}-
2010
We report on a search for the flavor-changing neutral-current decay D0 \to {\mu}+ {\mu}- in pp collisions at \surd s = 1.96 TeV using 360 pb-1 of integrated luminosity collected by the CDF II detector at the Fermilab Tevatron collider. A displaced vertex trigger selects long-lived D0 candidates in the {\mu}+ {\mu}-, {\pi}+{\pi}-, and K-{\pi}+ decay modes. We use the Cabibbo-favored D0 \to K-{\pi}+ channel to optimize the selection criteria in an unbiased manner, and the kinematically similar D0 \to{\pi}+ {\pi}- channel for normalization. We set an upper limit on the branching fraction (D0 --> {\mu}+ {\mu}-) < 2.1 E-7 (3.0 E-7) at the 90% (95%) confidence level.
Search for the rare decay Bs 0→μ+μ-
2010
We present the results of a search for the flavor changing neutral current decay B-s(0) -> mu(+)mu(-) using 6.1 fb(-1) of p (p) over bar collisions at root s = 1.96 TeV collected by the D0 experiment at the Fermilab Tevatron Collider. The observed number of B-s(0) candidates is consistent with background expectations. The resulting upper limit on the branching fraction is B(B-s(0) -> mu(+)mu(-)) < 5.1 x 10(-8) at the 95% C.L. This limit is a factor of 2.4 better than that of the previous DO analysis and the best limit to date. Published by Elsevier B.V.
General flavor blind minimal supersymmetric standard model andCPviolation
2001
We study the implications on flavor changing neutral current and $\mathrm{CP}$ violating processes in the context of supersymmetric theories without a new flavor structure (flavor blind supersymmetry). The low-energy parameters are determined by the running of the soft breaking terms from the grand unified scale with supersymmetric (SUSY) phases consistent with the electric dipole moment constraints. We find that the $\mathrm{CP}$ asymmetry in $\stackrel{\ensuremath{\rightarrow}}{b}s\ensuremath{\gamma}$ can reach large values potentially measurable at B factories, especially in the low $BR(\stackrel{\ensuremath{\rightarrow}}{b}s\ensuremath{\gamma})$ region, while the contributions to electr…
Restricted flavor structure of soft SUSY breaking trilinear couplings
2000
We analyze the flavor structure of the trilinear couplings in the different theoretical models of SUSY breaking. We generically obtain A_{ij}= A^L_i + A^R_j in all the models examined. In fact, this is the rigorous form when SUSY breaking effects appear through the Kahler metric of chiral fields or through wave-function renormalization. Indeed, the low-energy phenomenological requirements from the absence of charge and color breaking minima and the measurements in flavor changing neutral current (FCNC) observables strongly favor this restricted form of the trilinear matrices. As a straightforward consequence, the number of unknown parameters associated with the trilinear couplings is decrea…
Probing Supersymmetric Grand Unification through Flavor Physics
2007
Flavor Changing Neutral Current (FCNC) and CP violating processes are a powerful tool to probe the Standard Model (SM) and, hence, to constrain or obtain indirect hints of New Physics (NP) beyond it. Within Supersymmetric Grand Unified theories it is generally possible to link processes occurring in the leptonic and hadronic sectors; thus, their correlated analysis provides a very interesting low energy test for a Grand Unified theory at high energies. Similarly to the FCNC decays, we also show that the Lepton Flavor Universality tests in low-energy systems ( K l 2 and π l 2 ) offer a unique opportunity in shedding light on physics beyond the Standard Model; the smallness of NP effects is m…
Search for the Flavor-Changing Neutral Current DecayBs0→μ+μ−inpp¯Collisions ats=1.96 TeVwith the D0 Detector
2005
We present the results of a search for the flavor-changing neutral current decay B-s(0)-->mu(+)mu(-) using a data set with integrated luminosity of 240 pb(-1) of p (p) over bar collisions at roo ...
Search for flavor-changing-neutral-current D meson decays
2008
We study the flavor-changing-neutral-current process c to u mu+ mu- using 1.3 fb^-1 of p p bar collisions at sqrt(s) = 1.96 TeV recorded by the D0 detector operating at the Fermilab Tevatron Collider. We see clear indications of the Ds+ and D+ to phi pi+ to mu+ mu- pi+ final states with significance greater than four standard deviations above background for the D+ state. We search for the continuum decay of D+ to pi+mu+mu- in the dimuon invariant mass spectrum away from the phi resonance. We see no evidence of signal above background and set a limit of B(D+ to pi+mu+mu-) < 3.9 x 10^-6 at the 90% C.L. This limit places the most stringent constraint on new phenomena in the c to u mu+ mu- t…