T. Affolder

Measurement of the B0(s) - anti-B0(s) Oscillation Frequency

We present the first measurement of the Bs-Bsbar oscillation frequency Delta m_s. We use 1 fb^-1 of data from p-pbar collisions at sqrt{s}=1.96 TeV collected with the CDF II detector at the Fermilab Tevatron. The sample contains signals of 3,600 fully reconstructed hadronic Bs decays and 37,000 partially reconstructed semileptonic Bs decays. We measure the probability as a function of proper decay time that the Bs decays with the same, or opposite, flavor as the flavor at production, and we find a signal consistent with Bs-Bsbar oscillations. The probability that random fluctuations could produce a comparable signal is 0.2%. Under the hypothesis that the signal is due to Bs-Bsbar oscillations, we measure Delta m_s = 17.31^{+0.33}_{-0.18} (stat.) +- 0.07 (syst.) ps^-1 and determine |Vtd/Vts| = 0.208^{+0.001}_{-0.002} (exp.) ^{+0.008}_{-0.006} (theo.).

Measurement of the B(c)+ meson lifetime using B(c)+ ---> J/psi e+ nu(e)

The authors present a measurement of the B{sub c}{sup +} meson lifetime in the semileptonic decay mode B{sub c}{sup +} {yields} J/{psi}e{sup +}{nu}{sub e} using the CDF II detector at the Fermilab Tevatron Collider. From a sample of about 360 pb{sup -1} of p{bar p} collisions at {radical}s = 1.96 TeV, they reconstruct J/{psi}e{sup +} pairs with invariant mass in the kinematically allowed range 4 < M{sub J/{psi}e} < 6 GeV/c{sup 2}. A fit to the decay-length distribution of 238 signal events yields a measured B{sub c}{sup +} meson lifetime of 0.463{sub -0.065}{sup +0.073}(stat) {+-} 0.036(syst) ps.Measurement of the B-c(+) meson lifetime using the decay mode B-c(+)-> J/psi e(+)nu(e)

Search for new high-mass particles decaying to Lepton pairs in p(p)over-bar collisions at root s=1.96 TeV

A search for new particles (X) that decay to electron or muon pairs has been performed using approximately 200 pb{sup -1} of pp collision data at {radical}(s)=1.96 TeV collected by the CDF II experiment at the Fermilab Tevatron. Limits on {sigma}(pp{yields}X)BR(X{yields}ll) are presented as a function of dilepton invariant mass m{sub ll}>150 GeV/c{sup 2}, for different spin hypotheses (0, 1, or 2). The limits are approximately 25 fb for m{sub ll}>600 GeV/c{sup 2}. Lower mass bounds for X from representative models beyond the standard model including heavy neutral gauge bosons are presented.

Search for Bs0â†Î+Î- and Bd0â†Î +Î- Decays in pp Collisions with CDF II

We report on a search for Bs ->mu+mu- and Bd ->mu+mu- decays in ppbar collisions at sqrt(S) = 1.96 TeV using 364 pb-1 of data collected by the CDF II detector at the Fermilab Tevatron Collider. After applying all selection requirements, we observe no candidates inside the Bs or Bd mass windows, consistent with the background expectation. The resulting upper limits on the branching fractions are B(Bs ->mu+mu-)<1.5E10-7 and B(Bd ->mu+mu-)<3.9E-8 at 90% confidence level.

Measurement of the average time-integrated mixing probability of b-flavored hadrons produced at the Fermilab Tevatron

We have measured the number of like-sign (LS) and opposite-sign (OS) lepton pairs arising from double semileptonic decays of b and (b) over bar hadrons, pair produced at the Fermilab Tevatron collider. The data samples were collected with the Collider Detector at Fermilab during the 1992-1995 collider run by triggering on the existence of mumu or emu candidates in an event. The observed ratio of LS to OS dileptons leads to a measurement of the average time-integrated mixing probability of all produced b-flavored hadrons which decay weakly, (chi) over bar =0.152+/-0.007 (stat)+/-0.011 (syst), that is significantly larger than the world average (chi) over bar =0.118+/-0.005.

Observation of B0(s) - anti-B0(s) Oscillations

We report the observation of Bs-Bsbar oscillations from a time-dependent measurement of the Bs-Bsbar oscillation frequency Delta ms. Using a data sample of 1 fb^-1 of p-pbar collisions at sqrt{s}=1.96 TeV collected with the CDF II detector at the Fermilab Tevatron, we find signals of 5600 fully reconstructed hadronic Bs decays, 3100 partially reconstructed hadronic Bs decays, and 61500 partially reconstructed semileptonic Bs decays. We measure the probability as a function of proper decay time that the Bs decays with the same, or opposite, flavor as the flavor at production, and we find a signal for Bs-Bsbar oscillations. The probability that random fluctuations could produce a comparable signal is 8 X 10^-8, which exceeds 5 sigma significance. We measure Delta ms = 17.77 +- 0.10 (stat) +- 0.07 (syst) ps^-1 and extract |Vtd/Vts| = 0.2060 +- 0.0007 (exp) + 0.0081 - 0.0060 (theor).

Measurement of the W+W- production cross section in pp̄ collisions at s=1.96TeV using dilepton events

We present a measurement of the W(+)W(-) production cross section using 184 pb(-1) of p(p) collisions at a center-of-mass energy of 1.96 TeV collected with the Collider Detector at Fermilab. Using the dilepton decay channel W(+)W(-)-->l(+)nul(-), where the charged leptons can be either electrons or muons, we find 17 candidate events compared to an expected background of 5.0(+2.2)(-0.8) events. The resulting W(+)W(-) production cross-section measurement of sigma(pp-->W(+)W(-))=14.6(+5.8)(-5.1)(stat)(+1.8)(-3.0)(syst) +/- 0.9(lum) pb agrees well with the standard model expectation.We present a measurement of the W+W- production cross section using 184/pb of ppbar collisions at a center-of-mass energy of 1.96 TeV collected with the Collider Detector at Fermilab. Using the dilepton decay channel W+W- ->l+l-vvbar, where the charged leptons can be either electrons or muons, we find 17 candidate events compared to an expected background of 5.0+2.2-0.8 events. The resulting W+W- production cross section measurement of sigma(ppbar ->W+W-) = 14.6 +5.8 -5.1 (stat) +1.8 -3.0 (syst) +-0.9 (lum) pb agrees well with the Standard Model expectation.

Measurement of the Ratios of Branching Fractions B(B0(s) -->D(s)- pi++)/B(B0 -->D- pi++) and B(B+ -->D-bar0 pi++)/B(B0 -->D- pi++)

We report an observation of the decay B-s(0)-> D-s(-)pi(+) in p (p) over bar collisions at root s = 1.96 TeV using 115 pb(-1) of data collected by the CDF II detector at the Fermilab Tevatron. We observe 83 +/- 11(stat) B-s(0)-> D-s(-)pi(+) candidates, representing a large increase in statistics over previous measurements and the first observation of this decay at a p (p) over bar collider. We present the first measurement of the relative branching fraction B(B-s(0)-> D-s(-)pi(+))/B(B-0 -> D-pi(+))=1.32 +/- 0.18(stat)+/- 0.38(syst). We also measure B(B+->(D) over bar (0)pi(+))/B(B-0 -> D-pi(+))=1.97 +/- 0.10(stat)+/- 0.21(syst), which is consistent with previous measurements.We report an observation of the decay Bs ->Ds- pi+ in p pbar collisions at sqrt(s) = 1.96 TeV using 115 pb^(-1) of data collected by the CDF II detector at the Fermilab Tevatron. We observe 83 +/- 11 Bs ->Ds- pi+ candidates, representing a large increase in statistics over previous measurements and the first observation of this decay at a p pbar collider. We present the first measurement of the relative branching fraction B(Bs ->Ds- pi+) / B(B0 ->D- pi+) = 1.32 +/- 0.18 (stat.) +/- 0.38 (syst.). We also measure B(B+ ->D0bar pi+) / B(B0 ->D- pi+) = 1.97 +/- 0.10(stat.) +/- 0.21(syst.), which is consistent with previous measurements.

Search for new physics in lepton + photon + X events with 305 pb**-1 of p anti-p collisions at s**(1/2) = 1.96-TeV

We present results of a search for anomalous production of events containing a charged lepton (either electron or muon) and a photon, both with high transverse momentum, accompanied by additional signatures, X, including missing transverse energy (MET) and additional leptons and photons. We use the same kinematic selection criteria as in a previous CDF search, but with a substantially larger data set, 305 pb-1, a ppbar collision energy of 1.96 TeV, and the upgraded CDF II detector. We find 42 Lepton+Photon+MET events versus a standard model expectation of 37.3 +- 5.4 events. The level of excess observed in Run I, 16 events with an expectation of 7.6 +- 0.7 events (corresponding to a 2.7 sigma effect), is not supported by the new data. In the signature of Multi-Lepton+Photon+X we observe 31 events versus an expectation of 23.0 +- 2.7 events. In this sample we find no events with an extra photon or MET and so find no events like the one ee+gg+MET event observed in Run I.We present results of a search for anomalous production of events containing a charged lepton (l, either e or mu) and a photon (gamma), both with high transverse momentum, accompanied by additional signatures X, including missing transverse energy (ET) and additional leptons and photons. We use the same selection criteria as in a previous CDF search but with a substantially larger data set, 305 pb(-1), a pp collision energy of 1.96 TeV, and the CDF II detector. We find 42 lgammaET events versus an expectation of 37.3+/-5.4 events. We observe 31 llgamma+X events versus an expectation of 23.0+/-2.7 events. We find no events similar to the run I eegammagammaET event.

Measurement of the t anti-t production cross section in p anti-p collisions at s**(1/2) = 1.96-TeV using lepton plus jets events with semileptonic B decays to muons

We present a measurement of the t (t) over bar production cross section using 194 pb(-1) of CDF II data using events with a high transverse momentum electron or muon, three or more jets, and missing transverse energy. The measurement assumes 100% t -> Wb branching fraction. Events consistent with t (t) over bar decay are found by identifying jets containing heavy-flavor semileptonic decays to muons. The dominant backgrounds are evaluated directly from the data. Based on 20 candidate events and an expected background of 9.5 +/- 1.1 events, we measure a production cross section of 5.3 +/- 3.3(-1.0)(+1.3) pb, in agreement with the standard model.