Measurement of the top-quark mass with dilepton events selected using neuroevolution at CDF

We report a measurement of the top-quark mass Mt in the dilepton decay channel tt̄→bl′+νl′b̄l-ν̄l. Events are selected with a neural network which has been directly optimized for statistical precision in top-quark mass using neuroevolution, a technique modeled on biological evolution. The top-quark mass is extracted from per-event probability densities that are formed by the convolution of leading order matrix elements and detector resolution functions. The joint probability is the product of the probability densities from 344 candidate events in 2.0fb-1 of pp̄ collisions collected with the CDF II detector, yielding a measurement of Mt=171.2±2.7(stat)±2.9(syst)GeV/c2. © 2009 The American Physical Society

Direct Bound on the Total Decay Width of the Top Quark in p(p)over-bar Collisions at root s=1.96 TeV

We present the first direct experimental bound on the total decay width of the top quark, Gamma(t), using 955 pb(-1) of the Tevatron's p (p) over bar collisions recorded by the Collider Detector at Fermilab. We identify 253 top-antitop pair candidate events. The distribution of reconstructed top quark mass from these events is fitted to templates representing different values of the top quark width. Using a confidence interval based on likelihood-ratio ordering, we extract an upper limit at 95\% C.L. of Gamma(t) < 13.1 GeV for an assumed top quark mass of 175 GeV/c(2)

Measurement of the fraction of tt¯ production via gluon-gluon fusion in pp¯ collisions at √s = 1.96 TeV

Aaltonen, T., Adelman, J., Akimoto, T., Albrow, M.G., Álvarez González, B., Amerio, S., Amidei, D., Anastassov, A., Annovi, A., Antos, J., Apollinari, G., Apresyan, A., Arisawa, T., Artikov, A., Ashmanskas, W., Attal, A., Aurisano, A., Azfar, F., Azzurri, P., Badgett, W., Barbaro-Galtieri, A., Barnes, V.E., Barnett, B.A., Bartsch, V., Bauer, G., Beauchemin, P.-H., Bedeschi, F., Bednar, P., Beecher, D., Behari, S., Bellettini, G., Bellinger, J., Benjamin, D., Beretvas, A., Beringer, J., Bhatti, A., Binkley, M., Bisello, D., Bizjak, I., Blair, R.E., Blocker, C., Blumenfeld, B., Bocci, A., Bodek, A., Boisvert, V., Bolla, G., Bortoletto, D., Boudreau, J., Boveia, A., Brau, B., Bridgeman, A., Brigliadori, L., Bromberg, C., Brubaker, E., Budagov, J., Budd, H.S., Budd, S., Burkett, K., Busetto, G., Bussey, P., Buzatu, A., Byrum, K.L., Cabrera, S., Calancha, C., Campanelli, M., Campbell, M., Canelli, F., Canepa, A., Carlsmith, D., Carosi, R., Carrillo, S., Carron, S., Casal, B., Casarsa, M., Castro, A., Catastini, P., Cauz, D., Cavaliere, V., Cavalli-Sforza, M., Cerri, A., Cerrito, L., Chang, S.H., Chen, Y.C., Chertok, M., Chiarelli, G., Chlachidze, G., Chlebana, F., Cho, K., Chokheli, D., Chou, J.P., Choudalakis, G., Chuang, S.H., Chung, K., Chung, W.H., Chung, Y.S., Ciobanu, C.I., Ciocci, M.A., Clark, A., Clark, D., Compostella, G., Convery, M.E., Conway, J., Copic, K., Cordelli, M., Cortiana, G., Cox, D.J., Crescioli, F., Cuenca Almenar, C., Cuevas, J., Culbertson, R., Cully, J.C., Dagenhart, D., Datta, M., Davies, T., De Barbaro, P., De Cecco, S., Deisher, A., De Lorenzo, G., Dell'Orso, M., Deluca, C., Demortier, L., Deng, J., Deninno, M., Derwent, P.F., Di Giovanni, G.P., Dionisi, C., Di Ruzza, B., Dittmann, J.R., D'Onofrio, M., Donati, S., Dong, P., Donini, J., Dorigo, T., Dube, S., Efron, J., Elagin, A., Erbacher, R., Errede, D., Errede, S., Eusebi, R., Fang, H.C., Farrington, S., Fedorko, W.T., Feild, R.G., Feindt, M., Fernandez, J.P., Ferrazza, C., Field, R., Flanagan, G., Forrest, R., Franklin, M., Freeman, J.C., Furic, I., Gallinaro, M., Galyardt, J., Garberson, F., Garcia, J.E., Garfinkel, A.F., Genser, K., Gerberich, H., Gerdes, D., Gessler, A., Giagu, S., Giakoumopoulou, V., Giannetti, P., Gibson, K., Gimmell, J.L., Ginsburg, C.M., Giokaris, N., Giordani, M., Giromini, P., Giunta, M., Giurgiu, G., Glagolev, V., Glenzinski, D., Gold, M., Goldschmidt, N., Golossanov, A., Gomez, G., Gomez-Ceballos, G., Goncharov, M., González, O., Gorelov, I., Goshaw, A.T., Goulianos, K., Gresele, A., Grinstein, S., Grosso-Pilcher, C., Group, R.C., Grundler, U., Guimaraes Da Costa, J., Gunay-Unalan, Z., Haber, C., Hahn, K., Hahn, S.R., Halkiadakis, E., Han, B.-Y., Han, J.Y., Handler, R., Happacher, F., Hara, K., Hare, D., Hare, M., Harper, S., Harr, R.F., Harris, R.M., Hartz, M., Hatakeyama, K., Hauser, J., Hays, C., Heck, M., Heijboer, A., Heinemann, B., Heinrich, J., Henderson, C., Herndon, M., Heuser, J., Hewamanage, S., Hidas, D., Hill, C.S., 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Search for Supersymmetry in p (p)over-bar Collisions at root s=1.96 TeV Using the Trilepton Signature for Chargino-Neutralino Production

We use the three lepton and missing energy trilepton signature to search for chargino-neutralino production with 2.0 fb(-1) of integrated luminosity collected by the CDF II experiment at the Tevatron p (p) over bar collider. We expect an excess of approximately 11 supersymmetric events for a choice of parameters of the mSUGRA model, but our observation of 7 events is consistent with the standard model expectation of 6.4 events. We constrain the mSUGRA model of supersymmetry and rule out chargino masses up to 145 GeV/c(2) for a specific choice of parameters

Search for Standard Model Higgs Boson Production in Association with a W Boson at CDF

35 pages, 10 figuresWe present a search for standard model Higgs boson production in association with a W boson in proton-antiproton collisions ($p\bar{p}\to W^\pm H \to \ell\nu b\bar{b}$) at a center of mass energy of 1.96 TeV. The search employs data collected with the CDF II detector which correspond to an integrated luminosity of approximately 1 fb-1. We select events consistent with a signature of a single lepton ($e^\pm/\mu^\pm$), missing transverse energy, and two jets. Jets corresponding to bottom quarks are identified with a secondary vertex tagging method and a neural network filter technique. The observed number of events and the dijet mass distributions are consistent with the standard model background expectations, and we set 95% confidence level upper limits on the production cross section times branching ratio ranging from 3.9 to 1.3 pb for Higgs boson masses from 110 to 150 GeV/c2, respectively

Search for Standard Model Higgs Boson Production in Association with a W Boson at CDF

35 pages, 10 figuresWe present a search for standard model Higgs boson production in association with a W boson in proton-antiproton collisions ($p\bar{p}\to W^\pm H \to \ell\nu b\bar{b}$) at a center of mass energy of 1.96 TeV. The search employs data collected with the CDF II detector which correspond to an integrated luminosity of approximately 1 fb-1. We select events consistent with a signature of a single lepton ($e^\pm/\mu^\pm$), missing transverse energy, and two jets. Jets corresponding to bottom quarks are identified with a secondary vertex tagging method and a neural network filter technique. The observed number of events and the dijet mass distributions are consistent with the standard model background expectations, and we set 95% confidence level upper limits on the production cross section times branching ratio ranging from 3.9 to 1.3 pb for Higgs boson masses from 110 to 150 GeV/c2, respectively

Search for Standard Model Higgs Boson Production in Association with a W Boson at CDF

35 pages, 10 figuresInternational audienceWe present a search for standard model Higgs boson production in association with a W boson in proton-antiproton collisions ($p\bar{p}\to W^\pm H \to \ell\nu b\bar{b}$) at a center of mass energy of 1.96 TeV. The search employs data collected with the CDF II detector which correspond to an integrated luminosity of approximately 1 fb-1. We select events consistent with a signature of a single lepton ($e^\pm/\mu^\pm$), missing transverse energy, and two jets. Jets corresponding to bottom quarks are identified with a secondary vertex tagging method and a neural network filter technique. The observed number of events and the dijet mass distributions are consistent with the standard model background expectations, and we set 95% confidence level upper limits on the production cross section times branching ratio ranging from 3.9 to 1.3 pb for Higgs boson masses from 110 to 150 GeV/c2, respectively

First Measurement of ZZ Production in ppbar Collisions at sqrt(s)=1.96 TeV

7 pages, 1 figure. Submitted to Phys. Rev. LettWe report the first measurement of the cross section for Z boson pair production at a hadron collider. This result is based on a data sample corresponding to 1.9 fb-1 of integrated luminosity from ppbar collisions at sqrt{s} = 1.96 TeV collected with the CDF II detector at the Fermilab Tevatron. In the llll channel, we observe three ZZ candidates with an expected background of 0.096^{+0.092}_{-0.063} events. In the llnunu channel, we use a leading-order calculation of the relative ZZ and WW event probabilities to discriminate between signal and background. In the combination of llll and llnunu channels, we observe an excess of events with a probability of $5.1\times 10^{-6}$ to be due to the expected background. This corresponds to a significance of 4.4 standard deviations. The measured cross section is sigma(ppbar -> ZZ) = 1.4^{+0.7}_{-0.6} (stat.+syst.) pb, consistent with the standard model expectation

Search for the Flavor Changing Neutral Current Decay t →Zq\to Zq in ppˉp \bar{p} Collisions at s=1.96\sqrt{s}=1.96

We report a search for the flavor changing neutral current (FCNC) decay of the top quark \tZq ($q=u,c$) in \ppbar collisions at \sqrt{s} = 1.96\tev using a data sample corresponding to an integrated luminosity of 1.9\invfb collected by the CDF II detector. This decay is strongly suppressed in the standard model (SM) and a signal at the Tevatron would be an indication of physics beyond the SM. Using $Z+\ge4$ jet final state candidate events, both with and without an identified bottom quark jet, we discriminate signal from background by exploring kinematic constraints present in FCNC events and obtain an upper limit of \btZq < 3.7% at 95% C.L