31 research outputs found
Observation of the Baryonic Flavor-Changing Neutral Current Decay Lambda_b -> Lambda mu+ mu-
We report the first observation of the baryonic flavor-changing neutral
current decay Lambda_b -> Lambda mu+ mu- with 24 signal events and a
statistical significance of 5.8 Gaussian standard deviations. This measurement
uses ppbar collisions data sample corresponding to 6.8fb-1 at sqrt{s}=1.96TeV
collected by the CDF II detector at the Tevatron collider. The total and
differential branching ratios for Lambda_b -> Lambda mu+ mu- are measured. We
find B(Lambda_b -> Lambda mu+ mu-) = [1.73+-0.42(stat)+-0.55(syst)] x 10^{-6}.
We also report the first measurement of the differential branching ratio of B_s
-> phi mu+ mu- using 49 signal events. In addition, we report branching ratios
for B+ -> K+ mu+ mu-, B0 -> K0 mu+ mu-, and B -> K*(892) mu+ mu- decays.Comment: 8 pages, 2 figures, 4 tables. Submitted to Phys. Rev. Let
First model-independent determination of the relative strong phase between D0 and D0B --> K0Spi+pi- and its impact on the CKM Angle gamma/phi3 measurement
We exploit the quantum coherence between pair-produced D0 and D0B in
psi(3770) decays to make a first determination of the relative strong phase
differences between D0--> K0Spi+pi- and D0B--> K0Spi+pi-, which are of great
importance in determining the CKM angle gamma/phi3 in B- --> D0 (D0B) K-
decays. Using 818 1/pb of e+e- collision data collected with the CLEO-c
detector at Ecm = 3.77 GeV, we employ a binned Dalitz-plot analysis of K0S
pi+pi- and K0Lpi+pi- decays recoiling against flavor-tagged, CP-tagged and
K0Spi+pi- tagged events to determine these strong phase differences.Comment: submitted to Phys. Rev.
New Measurement of Exclusive Decays of the chi_c0 and chi_c2 to Two-Meson Final States
Using a sample of 2.59 times 10^7 psi(2S) decays collected by the CLEO--c
detector, we present results of a study of chi_{c0} and chi_{c2} decays into
two-meson final states. We present the world's most precise measurements of the
chi_{cJ,(J=0,2)} -> pi^+pi^-, pi^0 pi^0, K^+K^-, K^0_S K^0_S, eta eta and
eta^{prime} eta^{prime} branching fractions, and a search for chi_c decays into
eta eta^{prime}. These results shed light on the mechanism of charmonium decays
into pseudoscalar mesons.Comment: 7 pages, available through http://www.lns.cornell.edu/public/CLNS/,
submitted to Phys. Rev.
Determination of the Strong Phase in D0 -> K+pi- Using Quantum-Correlated Measurements
We exploit the quantum coherence between pair-produced D0 and D0bar in
psi(3770) decays to study charm mixing, which is characterized by the
parameters x and y, and to make a first determination of the relative strong
phase \delta between D0 -> K+pi- and D0bar -> K+pi-. Using 281 pb^-1 of e^+e^-
collision data collected with the CLEO-c detector at E_cm = 3.77 GeV, as well
as branching fraction input and time-integrated measurements of R_M =
(x^2+y^2)/2 and R_{WS} = Gamma(D0 -> K+pi-)/Gamma(D0bar -> K+pi-) from other
experiments, we find \cos\delta = 1.03 +0.31-0.17 +- 0.06, where the
uncertainties are statistical and systematic, respectively. By further
including other mixing parameter measurements, we obtain an alternate
measurement of \cos\delta = 1.10 +- 0.35 +- 0.07, as well as x\sin\delta = (4.4
+2.7-1.8 +- 2.9) x 10^-3 and \delta = 22 +11-12 +9-11 degrees.Comment: 5 pages, also available through
http://www.lns.cornell.edu/public/CLNS/2007/. Incorporated referees' comment
Combined Tevatron upper limit on gg->H->W+W- and constraints on the Higgs boson mass in fourth-generation fermion models
Report number: FERMILAB-PUB-10-125-EWe combine results from searches by the CDF and D0 collaborations for a standard model Higgs boson (H) in the process gg->H->W+W- in p=pbar collisions at the Fermilab Tevatron Collider at sqrt{s}=1.96 TeV. With 4.8 fb-1 of integrated luminosity analyzed at CDF and 5.4 fb-1 at D0, the 95% Confidence Level upper limit on \sigma(gg->H) x B(H->W+W-) is 1.75 pb at m_H=120 GeV, 0.38 pb at m_H=165 GeV, and 0.83 pb at m_H=200 GeV. Assuming the presence of a fourth sequential generation of fermions with large masses, we exclude at the 95% Confidence Level a standard-model-like Higgs boson with a mass between 131 and 204 GeV.We combine results from searches by the CDF and D0 collaborations for a standard model Higgs boson (H) in the process ggâHâW+W- in ppÌ
collisions at the Fermilab Tevatron Collider at âs=1.96ââTeV. With 4.8ââfb-1 of integrated luminosity analyzed at CDF and 5.4ââfb-1 at D0, the 95% confidence level upper limit on Ï(ggâH)ĂB(HâW+W-) is 1.75 pb at mH=120ââGeV, 0.38 pb at mH=165ââGeV, and 0.83 pb at mH=200ââGeV. Assuming the presence of a fourth sequential generation of fermions with large masses, we exclude at the 95% confidence level a standard-model-like Higgs boson with a mass between 131 and 204 GeV.Peer reviewe
Measurement of trilinear gauge boson couplings from WW plus WZ -> lvjj events in p(p)over-bar collisions at root s=1.96 TeV
Combination of t(t)over-bar cross section measurements and constraints on the mass of the top quark and its decays into charged Higgs bosons
Limits on Anomalous Trilinear Gauge Couplings in Z gamma Events from p(p)over-bar Collisions at root s=1.96 TeV
Using Z gamma candidate events collected by the CDF detector at the Tevatron Collider, we search for potential anomalous (non-standard-model) couplings between the Z boson and the photon. Z gamma couplings vanish at tree level and are heavily suppressed at higher orders; hence any evidence of couplings indicates new physics. Measurements are performed using data corresponding to an integrated luminosity of 4.9 fb(-1) in the Z -> nu(nu) over bar decay channel and 5: 1 fb(-1) in the Z -> l(+)l(-) (l - mu, e) decay channels. The combination of these measurements provides the most stringent limits to date on Z gamma trilinear gauge couplings. Using an energy scale of Lambda = 1.5 TeV to allow for a direct comparison with previous measurements, we find limits on the CP-conserving parameters that describe Z gamma couplings to be vertical bar h(3)(gamma,Z)vertical bar < 0.022 and vertical bar h(4)(gamma,Z)vertical bar < 0.0009. These results are consistent with standard model predictions