1,179 research outputs found
Decays of the tau lepton
No full textPrevious measurements of the branching fractions of the tau lepton result in a discrepancy between the inclusive branching fraction and the sum of the exclusive branching fractions to final states containing one charged particle. The sum of the exclusive branching fractions is significantly smaller than the inclusive branching fraction. In this analysis, the branching fractions for all the major decay modes are measured simultaneously with the sum of the branching fractions constrained to be one. The branching fractions are measured using an unbiased sample of tau decays, with little background, selected from 207 pb/sup -1/ of data accumulated with the Mark II detector at the PEP e/sup +/e/sup -/ storage ring. The sample is selected using the decay products of one member of the ..gamma../sup +/..gamma../sup -/ pair produced in e/sup +/e/sup -/ annihilation to identify the event and then including the opposite member of the pair in the sample. The sample is divided into subgroups according to charged and neutral particle multiplicity, and charged particle identification. The branching fractions are simultaneously measured using an unfold technique and a maximum likelihood fit. The results of this analysis indicate that the discrepancy found in previous experiments is possibly due to two sources. First, the leptonic branching fractions measured in this analysis are about one standard deviation higher than the world average. The measured leptonic branching fractions correspond to a tau lifetime of (3.0 +- 0.2) x 10/sup -13/ s. Secondly, the total branching fraction to one charged hadron plus at least one neutral particle is measured to be (7 +- 3)% higher than the branching fraction expected from a combination of previous measurements and theoretical predictions. It is shown that decay modes involving the eta are not expected to contribute more than 3% to this excess
Measurements of the decays B-0 -> (D)over-bar(0) p(p)over-bar, B0 -> (D)over-bar*(0) p(p)over-bar, B-0 -> D- p(p)over-bar pi(+), and B-0 -> D*(-) p(p)over-bar pi(+)
No full textWe present measurements of branching fractions of B-0 decays to multibody final states containing protons, based on 232x10(6) Upsilon(4S)-> B (B) over bar decays collected with the BABAR detector at the SLAC PEP-II asymmetric-energy B factory. We measure the branching fractions B(B-0 ->(D) over bar (0)p (p) over bar)=(1.13 +/- 0.06 +/- 0.08)x10(-4), B(B-0 ->(D) over bar (*0)p (p) over bar)=(1.01 +/- 0.10 +/- 0.09)x10(-4), B(B-0 -> D(-)p (p) over bar pi(+))=(3.38 +/- 0.14 +/- 0.29)x10(-4), and B(B-0 -> D(*-)p (p) over bar pi(+))=(4.81 +/- 0.22 +/- 0.44)x10(-4) where the first error is statistical and the second systematic. We present a search for the charmed pentaquark state, Theta(c)(3100) observed by H1 and put limits on the branching fraction B(B-0 ->Theta(c)(p) over bar pi(+))xB(Theta(c)-> D(*-)p)Theta(c)(p) over bar pi(+))xB(Theta(c)-> D(-)p)< 9x10(-6). Upon investigation of the decay structure of the above four B-0 decay modes, we see an enhancement at low p (p) over bar mass and deviations from phase-space in the (D) over bar(p) over bar and (D) over bar invariant mass spectra
Dalitz plot analyses of B-0 -> (D-DK+)-K-0 and B+-> (D)over-bar(-)D(0)K(+) decays
No full text© 2015, APS Journal
Measurement of Collins asymmetries in inclusive production of charged pion pairs in e+e− annihilation at BABAR
No full textWe present measurements of Collins asymmetries in the inclusive process e+e−→ππX, where π stands for charged pions, at a center-of-mass energy of 10.6 GeV. We use a data sample of 468 fb−1 collected by the BABAR experiment at the PEP-II B factory at SLAC, and consider pairs of charged pions produced in opposite hemispheres of hadronic events. We observe clear asymmetries in the distributions of the azimuthal angles in two distinct reference frames. We study the dependence of the asymmetry on several kinematic variables, finding that it increases with increasing pion momentum and momentum transverse to the analysis axis, and with increasing angle between the thrust and beam axis
Observation of the baryonic decay (B)over-bar(0) -> Lambda(+)(c)(p)over-barK(-)K(+)
No full textWe report the observation of the baryonic decay (B) over bar (0) -> Lambda(+)(c)(p) over barK(-)K(+) using a data sample of 471 x 10(6) B (B) over bar pairs produced in e(+)e(-) annihilations at root s = 10.58 GeV. This data sample was recorded with the BABAR detector at the PEP- II storage ring at SLAC. We find B((B) over bar (0) -> Lambda(+)(c)(p) over barK(-)K(+)) = (2.5 +/- 0.4((stat)) +/- 0.2((syst)) +/- 0.6(B(Lambda c+)) ) x 10(-5) where the uncertainties are statistical, systematic, and due to the uncertainty of the Lambda(+)(c) -> (p) over barK(-)pi(+) branching fraction, respectively. The result has a significance corresponding to 5.0 standard deviations, including all uncertainties. For the resonant decay (B) over bar (0) -> Lambda(+)(c)(p) over bar phi, we determine the upper limit B((B) over bar (0) -> Lambda(+)(c)(p) over bar phi) < 1.2 x 10(-5) at 90% confidence level
Search for Evidence of Baryogenesis and Dark Matter in B+ →ψ D+ p Decays at BABAR
No full textA new dark sector antibaryon, denoted ψD, could be produced in decays of B mesons. This Letter presents a search for B+→ψD+p (and the charge conjugate) decays in e+e- annihilations at 10.58 GeV, using data collected in the BABAR experiment. Data corresponding to an integrated luminosity of 398 fb-1 are analyzed. No evidence for a signal is observed. Branching fraction upper limits in the range from 10-7-10-5 are obtained at 90% confidence level for masses of 1.0<4.3 GeV/c2. The result is also reinterpreted to provide the first limits on a supersymmetric model with R-parity violation and a light neutralino
Search for the decay (B)over-bar(0) -> Lambda(+)(c)(p)over-barp(p)over-bar
No full textWe report a search for the decay (B) over bar (0) -> Lambda(+)(c)(p) over barp (p) over bar. Using a data sample of 471 x 10(6) B (B) over bar pairs collected with the BABAR detector at the PEP-II2 storage ring at SLAC, we find no events and set an upper limit on the branching fraction B((B) over bar (0) -> Lambda(+)(c)(p) over barp (p) over bar x B(Lambda(+)(c) -> pK(-)pi(+))/0.050 pK(-)pi(+)) to the world average value
Search for Evidence of Baryogenesis and Dark Matter in B+→ψD+p Decays at BABAR
No full textA new dark sector antibaryon, denoted psi(D), could be produced in decays of B mesons. This Letter presents a search for B+ -> psi(D) + p (and the charge conjugate) decays in e(+)e(-) annihilations at 10.58 GeV, using data collected in the BABAR experiment. Data corresponding to an integrated luminosity of 398 fb(-1) are analyzed. No evidence for a signal is observed. Branching fraction upper limits in the range from 10(-7)-10(-5) are obtained at 90% confidence level for masses of 1.0 < m(psi D) < 4.3 GeV/c(2). The result is also reinterpreted to provide the first limits on a supersymmetric model with R-parity violation and a light neutralino
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