23 research outputs found
Studies of the Decay B+- -> D_CP K+-
We report studies of the decay B+- -> D_CP K+-, where D_CP denotes neutral D
mesons that decay to CP eigenstates. The analysis is based on a 29.1/fb data
sample of collected at the \Upsilon(4S) resonance with the Belle detector at
the KEKB asymmetric e+ e- storage ring. Ratios of branching fractions of
Cabibbo-suppressed to Cabibbo-favored processes involving D_CP are determined
to be B(B- -> D_1 K-)/B(B- -> D_1 pi-)=0.125 +- 0.036 +- 0.010 and B(B- -> D_2
K-)/B(B- -> D_2 pi-)=0.119 +- 0.028 +- 0.006, where indices 1 and 2 represent
the CP=+1 and CP=-1 eigenstates of the D0 - anti D0 system, respectively. We
also extract the partial rate asymmetries for B+- -> D_CP K+-, finding A_1 =
0.29 +- 0.26 +- 0.05 and A_2 = -0.22 +- 0.24 +- 0.04.Comment: 10 pages, 2 figures, submitted to Physical Review Letter
Observation of Ds+K- and evidence for D-s(+)pi(-) final states in neutral B decays
We report the first observation of a B meson decay that is not accessible by a direct spectator process. The channel (B) over bar (0)-->Ds+K- is found in a sample of 85x10(6) B (B) over bar events, collected with the Belle detector at KEKB, with a branching fraction B((B) over bar (0)-->Ds+K-)=(4.6(-1.1)(+1.2)+/-1.3)x10(-5). We also obtain evidence for the B-0-->D(s)(+)pi(-) decay with branching fraction B(B-0-->D(s)(+)pi(-))=(2.4(-0.8)(+1.0)+/-0.7)x10(-5). This value may be used to extract a model-dependent value of \V-ub\
Neutrinos
229 pages229 pages229 pagesThe Proceedings of the 2011 workshop on Fundamental Physics at the Intensity Frontier. Science opportunities at the intensity frontier are identified and described in the areas of heavy quarks, charged leptons, neutrinos, proton decay, new light weakly-coupled particles, and nucleons, nuclei, and atoms
Observation of radiative B -> phi K gamma decays
The radiative decay B-->phiKgamma is observed for the first time. The branching fraction for the charged B--->phiK(-)gamma decay mode is measured to be B(B--->phiK(-)gamma)=(3.4+/-0.9+/-0.4)x10(-6). The photon energy distribution for the B--->phiK(-)gamma decay is presented. The signal for the neutral (B) over bar (0)-->phi(K) over bar (0)gamma decay mode is not statistically significant and an upper limit, B((B) over bar (0)-->phi(K) over bar (0)gamma)<8.3x10(-6) at 90% C.L., is set. The analysis is based on a data set of 90 fb(-1) collected by the Belle experiment at the e(+)e(-) asymmetric collider KEKB
Observation of B--/+->rho(-/+)rho(0) decays
We report the first observation of the charmless vector-vector decay process B-/+-->rho(-/+)rho(0). The measurement uses a 78 fb(-1) data sample collected with the Belle detector at the KEKB asymmetric e(+)e(-) collider operating at the Y(4S) resonance. We obtain a branching fraction of B(B-/+-->rho(-/+)rho(0))=[31.7+/-7.1(stat)(-6.7)(+3.8)(syst)]x10(-6). An analysis of the rho helicity-angle distributions gives a longitudinal polarization fraction of Gamma(L)/Gamma=0.95+/-0.11(stat)+/-0.02(syst). We also measure the direct-CP-violating asymmetry A(CP)(B-/+-->rho(-/+)rho(0))=0.00+/-0.22(stat)+/-0.03(syst)
Evidence for B -> phi phi K
We report evidence for the decay mode B-->phiphiK based on an analysis of 78 fb(-1) of data collected with the Belle detector at KEKB. This is the first example of a b-->s (s) over bars (s) over bars transition. The branching fraction for this decay is measured to be B(B+/--->phiphiK(+/-))=(2.6(-0.9)(+1.1)+/-0.3)x10(-6) for a phiphi invariant mass below 2.85 GeV/c(2). Results for other related charmonium decay modes are also reported
Measurement of the B-0-(B)over-bar(0) mixing parameter Delta m(d) using semileptonic B-0 decays
We present a measurement of the B-0-(B-0) over bar mixing parameter Deltam(d) using neutral B meson pairs in a 29.1 fb(-1) data sample collected at the Y(4S) resonance with the Belle detector at the KEKB asymmetric-energy e(+)e(-) collider. We exclusively reconstruct one neutral B meson in the semileptonic B-0-->D*-.(+)nu decay mode and identify the flavor of the accompanying B meson from its decay products. From the distribution of the time intervals between the two flavor-tagged B meson decay points, we obtain Deltam(d)=(0.494+/-0.012+/-0.015) ps(-1), where the first error is statistical and the second error is systematic
Measurement of branching fractions for B ->eta K-c((*)) decays
We report measurements of branching fractions for charged and neutral B-->eta(c)K decays where the eta(c) meson is reconstructed in the K(S)(0)K(+/-)pi(-/+), K(+)K(-)pi(0), K(*0)K(-)pi(+), and p (p) over bar decay channels. The neutral B-0 channel is a CP eigenstate and can be used to measure the CP violation parameter sin2phi(1). We also report the first observation of the B-0-->eta(c)K(*0) mode. The results are based on an analysis of 29.1 fb(-1) of data collected by the Belle detector at KEKB
Observation of the decay (B)over-bar(0)->Lambda(+)(c)(p)over-bar
We report the measurement of the charmed baryonic decay (B) over bar (0) --> Lambda(c)(+) (p) over bar with a branching fraction of (2.19(-0.49)(+0.56) +/- 0.32 +/- 0.57) x 10(-5) and a statistical significance of 5.8 sigma. The errors are statistical, systematic, and the error of the Lambda(c)(+) --> pK(-)pi(+) decay branching fraction. This is the first observation of a two-body baryonic B decay. The analysis is based on 78.2 fb(-1) of data accumulated at the Y(4S) resonance with the Belle detector at the KEKB asymmetric e(+)e(-) collider
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Real-space investigation of short-range magnetic correlations in fluoride pyrochlores NaCaCo 2 F7 and NaSrCo 2 F7 with magnetic pair distribution function analysis
We present time-of-flight neutron total scattering and polarized neutron scattering measurements of the magnetically frustrated compounds NaCaCo2F7 and NaSrCo2F7, which belong to a class of recently discovered pyrochlore compounds based on transition metals and fluorine. The magnetic pair distribution function (mPDF) technique is used to analyze and model the total scattering data in real space. We find that a previously proposed model of short-range XY-like correlations with a length scale of 10-15 Å, combined with nearest-neighbor collinear antiferromagnetic correlations, accurately describes the mPDF data at low temperature, confirming the magnetic ground state in these materials. This model is further verified by the polarized neutron scattering data. From an analysis of the temperature dependence of the mPDF and polarized neutron scattering data, we find that short-range correlations persist on the nearest-neighbor length scale up to 200 K, approximately two orders of magnitude higher than the spin freezing temperatures of these compounds. These results highlight the opportunity presented by these new pyrochlore compounds to study the effects of geometric frustration at relatively high temperatures, while also advancing the mPDF technique and providing an opportunity to investigate a genuinely short-range-ordered magnetic ground state directly in real space