Observation of the decay Bc+/--->J/psipi+/- and measurement of the Bc+/- mass

The Bc+/- meson is observed through the decay Bc+/--->J/psipi+/-, in data corresponding to an integrated luminosity of 2.4 fb(-1) recorded by the Collider Detector at Fermilab II detector at the Fermilab Tevatron. A signal of 108+/-15 candidates is observed, with a significance that exceeds 8sigma. The mass of the Bc+/- meson is measured to be 6275.6+/-2.9(stat)+/-2.5(syst) MeV/c2.

First flavor-tagged determination of bounds on mixing-induced CP violation in Bs0 --> J/psiphi decays

This Letter describes the first determination of bounds on the CP-violation parameter 2beta(s) using B(s)(0) decays in which the flavor of the bottom meson at production is identified. The result is based on approximately 2000 B(s)(0)-->J/psiphi decays reconstructed in a 1.35 fb(-1) data sample collected with the CDF II detector using pp collisions produced at the Fermilab Tevatron. We report confidence regions in the two-dimensional space of 2beta(s) and the decay-width difference DeltaGamma. Assuming the standard model predictions of 2beta(s) and DeltaGamma, the probability of a deviation as large as the level of the observed data is 15%, corresponding to 1.5 Gaussian standard deviations.

Search for heavy toplike quarks using lepton plus jets events in 1.96 TeV pp collisions

We present the results of a search for pair production of a new heavy toplike quark t' decaying to a W boson and another quark using the Collider Detector at Fermilab II detector in run II of the Tevatron pp collider. Using a data sample corresponding to 760 pb(-1) of integrated luminosity, we fit the observed spectrum of total transverse energy and reconstructed t' quark mass to a combination of standard model processes and t' pair production. We see no evidence for t't' production, and we infer a lower limit of 256 GeV/c(2) on the mass of the t' at 95% C.L. assuming standard strong couplings for the t'.

Measurement of Lifetime and Decay-Width Difference in B_{s};{0}-->J/psivarphi Decays

We measure the mean lifetime tau=2/(Gamma_{L}+Gamma_{H}) and the decay-width difference DeltaGamma=Gamma_{L}-Gamma_{H} of the light and heavy mass eigenstates of the B_{s}{0} meson, B_{sL}{0} and B_{sH}{0}, in B_{s}{0}-->J/psivarphi decays using 1.7 fb;{-1} of data collected with the CDF II detector at the Fermilab Tevatron pp[over ] collider. Assuming CP conservation, a good approximation for the B_{s}{0} system in the standard model, we obtain DeltaGamma=0.076_{-0.063}{+0.059}(stat)+/-0.006(syst) ps{-1} and tau=1.52+/-0.04(stat)+/-0.02(syst) ps, the most precise measurements to date. Our constraints on the weak phase and DeltaGamma are consistent with CP conservation.

Evidence for D0-D(0) mixing using the CDF II detector

We measure the time dependence of the ratio of decay rates for the rare decay D{0}-->K{+}pi{-} to the Cabibbo-favored decay D{0}-->K{-}pi;{+}. A signal of 12.7x10;{3} D{0}-->K{+}pi{-} decays was obtained using the Collider Detector at Fermilab II detector at the Fermilab Tevatron with an integrated luminosity of 1.5 fb;{-1}. We measure the D0-D[over ]{0} mixing parameters (R_{D},y{'},x{'2}), and find that the data are inconsistent with the no-mixing hypothesis with a probability equivalent to 3.8 Gaussian standard deviations.

Search for Bs0 --> micro+ micro- and B0 --> micro+ micro- decays with 2 fb-1 of pp collisions

We have performed a search for B(s)(0) --> micro(+) micro(-) and B(0) --> micro(+) micro(-) decays in pp collisions at square root s = 1.96 TeV using 2 fb(-1) of integrated luminosity collected by the CDF II detector at the Fermilab Tevatron Collider. The observed number of B(s)(0) and B0 candidates is consistent with background expectations. The resulting upper limits on the branching fractions are B(B(s)0) --> micro(+) micro(-)) <5.8 x 10(-8) and B(B(0) --> micro(+) micro(-))<1.8 x 10(-8) at 95% C.L.

Measurement of inclusive jet cross sections in Z/gamma*(-->e+e-) + jets production in pp[over ] collisions at square root s = 1.96 TeV

Inclusive jet cross sections in Z/gamma* events, with Z/gamma* decaying into an electron-positron pair, are measured as a function of jet transverse momentum and jet multiplicity in pp[over ] collisions at square root s = 1.96 TeV with the upgraded Collider Detector at Fermilab in run II, based on an integrated luminosity of 1.7 fb(-1). The measurements cover the rapidity region |y(jet)|<2.1 and the transverse momentum range p(T)(jet)>30 GeV/c. Next-to-leading order perturbative QCD predictions are in good agreement with the measured cross sections.

First measurement of W boson production in association with a single Charm quark in pp collisions at sqrt(s)=1.96 TeV

We present the first measurement of the production cross section of a W boson with a single charm quark (c) in pp collisions at sqrt(s)=1.96 TeV, using soft muon tagging of c jets. In a data sample of approximately 1.8 fb(-1), recorded with the Collider Detector at Fermilab II detector at the Fermilab Tevatron, we select events with W+1 or 2 jets. We use the charge correlation between the W and the muon from the semileptonic decay of a charm hadron to extract the Wc signal. We measure sigma Wc(PTc >20 GeV/c,|eta c|<1.5) x BR(W-->l nu)=9.8+/-3.2 pb, in agreement with theoretical expectations.

Observation of orbitally excited B(s) mesons

We report the observation of two narrow resonances consistent with states of orbitally excited (L=1) B_(s) mesons using 1 fb;(-1) of pp[over ] collisions at sqrt[s]=1.96 TeV collected with the Collider Detector at Fermilab II detector at the Fermilab Tevatron. We use two-body decays into K- and B+ mesons reconstructed as B(+)-->J/psiK(+), J/psi-->mu(+)mu(-) or B(+)-->D[over ](0)pi(+), D[over ](0)-->K(+)pi(-). We deduce the masses of the two states to be m(B_(s1))=5829.4+/-0.7 MeV/c(2) and m(B_(s2);(*))=5839.6+/-0.7 MeV/c;(2).

Direct measurement of the W Boson width in ppover collisions at square roots = 1.96 TeV

A direct measurement of the total decay width of the W boson Gamma(W) is presented using 350 pb(-1) of data from pp[over ] collisions at square root s = 1.96 TeV collected with the CDF II detector at the Fermilab Tevatron. The width is determined by normalizing predicted signal and background distributions to 230 185 W candidates decaying to enu and micronu in the transverse-mass region 50<M(T)<90 GeV and then fitting the predicted shape to 6055 events in the high-M(T) region, 90<M(T)<200 GeV. The result is Gamma(W)=2032 +/- 45(stat)+/-57(syst) MeV, consistent with the standard model expectation.

Cross-section-constrained top-quark mass measurement from dilepton events at the Tevatron

We report the first top-quark mass measurement that uses a cross-section constraint to improve the mass determination. This measurement is made with a dilepton tt event candidate sample collected with the Collider Detector II at Fermilab. From a data sample corresponding to an integrated luminosity of 1.2 fb(-1), we measure a top-quark mass of 170.7(-3.9)(+4.2)(stat)+/-2.6(syst)+/-2.4(theory) GeV/c(2). The measurement without the cross-section constraint is 169.7(-4.9)(+5.2)(stat)+/-3.1(syst) GeV/c(2).

A neurocomputational model of figure-ground discrimination and target tracking

A neurocomputational model is presented for figureground discrimination and target tracking. In the model, the elementary motion detectors of the correlation type, the computational modules of saccadic and smooth pursuit eye movement, an oscillatory neural-network motion perception module and a selective attention module are involved. It is shown that through the oscillatory amplitude and frequency encoding, and selective synchronization of phase oscillators, the figure and the ground can be successfully discriminated from each other. The receptive fields developed by hidden units of the networks were surprisingly similar to the actual receptive fields and columnar organization found in the primate visual cortex. It is suggested that equivalent mechanisms may exist in the primate visual cortex to discriminate figure-ground in both temporal and spatial domains.

Search for standard model Higgs bosons produced in association with W bosons

We report on the results of a search for standard model Higgs bosons produced in association with W bosons from pp[over] collisions at sqrt[s]=1.96 TeV. The search uses a data sample corresponding to approximately 1 fb(-1) of integrated luminosity. Events consistent with the W-->lnu and H-->bb[over] signature are selected by triggering on a high-p(T) electron or muon candidate and tagging one or two of the jet candidates as having originated from b quarks. A neural network filter rejects a fraction of tagged charm and light-flavor jets, increasing the b-jet purity in the sample. We observe no excess lnubb[over] production beyond the background expectation, and we set 95% confidence level upper limits on the production cross section times branching fraction sigma(pp[over]-->WH)Br(H-->bb[over]) ranging from 3.9 to 1.3 pb, for specific Higgs boson mass hypotheses in the range 110 to 150 GeV/c2, respectively.

First observation of the decay Bs0-->Ds-Ds+ and measurement of its branching ratio

We report the observation of the exclusive decay Bs0-->Ds-Ds+ at the 7.5 standard deviation level using 355 pb(-1) of data collected by the CDF II detector in pp collisions at sqrt[s]=1.96 TeV at the Fermilab Tevatron. We measure the relative branching ratio B(Bs0-->Ds-Ds+)/B(B0-->D-Ds+)=1.44(-0.44)(+0.48). Using the world average value for B(B0-->D-Ds+), we find B(Bs0-->Ds-Ds+)=(9.4(-4.2)(+4.4))x10(-3). This provides a lower bound DeltaGammasCP/Gammas>or=2B(Bs0-->Ds-Ds+)>1.2x10(-2) at 95% C.L.

Crosstalk between the SUMO and ubiquitin pathways

Several ways in which the SUMO and ubiquitin pathways can intersect and communicate have recently been discovered. This review discusses the principles of crosstalk between SUMOylation and ubiquitination, focusing on the RNF4 family of RING finger E3 ubiquitin ligases, which specifically recognize SUMOylated proteins via their SUMO moiety for ubiquitination.

Search for exclusive gammagamma production in Hadron-Hadron collisions

We have searched for exclusive gammagamma production in proton-antiproton collisions at sqrt[s]=1.96 TeV, using 532 pb(-1) of integrated luminosity taken by the run II Collider Detector at Fermilab. The event signature requires two electromagnetic showers, each with transverse energy E(T)>5 GeV and pseudorapidity |eta|<1.0, with no other particles detected in the event. Three candidate events are observed. We discuss the consistency of the three events with gammagamma, pi(0)pi(0), or eta eta production. The probability that other processes fluctuate to >or=3 events is 1.7x10(-4). An upper limit on the cross section of pp-->p + gammagamma + p production is set at 410 fb with 95% confidence level.

Modification of membrane excitability of neurons in the rat's dorsal cortex of the inferior colliculus by preceding hyperpolarization

The inferior colliculus (IC) is among the largest nuclei in the central auditory system and is considered to be a major integration center in the auditory pathway. To understand how IC contributes to auditory processing, we investigated the effects of preceding hyperpolarization on membrane excitability and firing behavior of neurons located in the dorsal cortex of the inferior colliculus (ICD). We made whole-cell patch clamp recordings from ICD neurons (n=96) in rat brain slices. We classified ICD neurons into three types, i.e. sustained-regular, sustained-adapting and buildup, according to their responses to depolarizing current injection. Nearly 91% of the neurons had sustained firing throughout the period of current injection, showing either regular or adapting pattern. About 9% of the neurons exhibited a buildup pattern, in which sustained firing started after a long delay. Rebound depolarization and spikes after hyperpolarization were seen in 51.7% of the sustained neurons, but were not seen in buildup neurons. When depolarizing current was preceded by a hyperpolarizing current, various forms of the modification on membrane excitability were observed. For non-rebound neurons, the membrane excitability was either suppressed or unchanged after pre-hyperpolarization. The first spike latency lengthened in neurons whose firing changed to a buildup pattern, shortened in those whose firing changed to a pauser pattern, and remained unchanged in those whose discharge pattern remained sustained. For rebound neurons, the firing rate decreased in neurons whose firing pattern was changed to onset or pauser, increased in neurons whose firing was changed to adapting, or remained unchanged in neurons whose firing became irregular. The first spike latency was shortened in all the rebound cells. The results suggest that intrinsic membrane properties can play an important role in integration of excitatory and inhibitory inputs and thereby in determination of the output of ICD neurons.

Observation of the Heavy Baryons Sigma b and Sigma b*

We report an observation of new bottom baryons produced in pp collisions at the Tevatron. Using 1.1 fb(-1) of data collected by the CDF II detector, we observe four Lambda b 0 pi+/- resonances in the fully reconstructed decay mode Lambda b 0-->Lambda c + pi-, where Lambda c+-->pK* pi+. We interpret these states as the Sigma b(*)+/- baryons and measure the following masses: m Sigma b+=5807.8 -2.2 +2.0(stat.)+/-1.7(syst.) MeV/c2, m Sigma b- =5815.2+/-1.0(stat.)+/-1.7(syst.) MeV/c2, and m(Sigma b*)-m(Sigma b)=21.2-1.9 +2.0(stat.)-0.3+0.4(syst.) MeV/c2.

Search for chargino-neutralino production in pp collisions at sq rt[s] = 1.96 TeV

We present a search for associated production of the chargino and neutralino supersymmetric particles using up to 1.1 fb{-1} of integrated luminosity collected by the CDF II experiment at the Tevatron pp collider at sq rt[s]=1.96 TeV. We analyze events with a large transverse momentum imbalance and either three charged leptons or two charged leptons of the same electric charge. The numbers of observed events are consistent with standard model expectations. Upper limits on the production cross section are derived in different theoretical models.

Precise measurement of the top-quark mass in the lepton+jets topology at CDF II

We present a measurement of the mass of the top quark from proton-antiproton collisions recorded at the CDF experiment in Run II of the Fermilab Tevatron. We analyze events from the single lepton plus jets final state (tt-->W(+)bW(-)b-->lnubqq'b). The top-quark mass is extracted using a direct calculation of the probability density that each event corresponds to the tt final state. The probability is a function of both the mass of the top quark and the energy scale of the calorimeter jets, which is constrained in situ by the hadronic W boson mass. Using 167 events observed in 955 pb(-1) of integrated luminosity, we achieve the single most precise measurement of the top-quark mass, 170.8+/-2.2(stat.)+/-1.4(syst.) GeV/c(2).