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Search for new physics in the μμ+e/μ+E T channel with a low-pT lepton threshold at the Collider Detector at Fermilab

Physical Review D - Particles, Fields, Gravitation and Cosmology 79:5 (2009)

Authors:

T Aaltonen, J Adelman, T Akimoto, MG Albrow, BA González, S Amerio, D Amidei, A Anastassov, A Annovi, J Antos, G Apollinari, A Apresyan, T Arisawa, A Artikov, W Ashmanskas, A Attal, A Aurisano, F Azfar, P Azzurri, W Badgett, A Barbaro-Galtieri, VE Barnes, BA Barnett, V Bartsch, G Bauer, PH Beauchemin, F Bedeschi, D Beecher, S Behari, G Bellettini, J Bellinger, D Benjamin, A Beretvas, J Beringer, A Bhatti, M Binkley, D Bisello, I Bizjak, RE Blair, C Blocker, B Blumenfeld, A Bocci, A Bodek, V Boisvert, G Bolla, D Bortoletto, J Boudreau, A Boveia, B Brau, A Bridgeman, L Brigliadori, C Bromberg, E Brubaker, J Budagov, HS Budd, S Budd, S Burke, K Burkett, G Busetto, P Bussey, A Buzatu, KL Byrum, S Cabrera, C Calancha, M Campanelli, M Campbell, F Canelli, A Canepa, B Carls, D Carlsmith, R Carosi, S Carrillo, S Carron, B Casal, M Casarsa, A Castro, P Catastini, D Cauz, V Cavaliere, M Cavalli-Sforza, A Cerri, L Cerrito, SH Chang, YC Chen, M Chertok, G Chiarelli, G Chlachidze, F Chlebana, K Cho, D Chokheli, JP Chou, G Choudalakis, SH Chuang, K Chung, WH Chung, YS Chung, T Chwalek, CI Ciobanu, MA Ciocci, A Clark

Abstract:

A search for new physics using three-lepton (trilepton) data collected with the CDF II detector and corresponding to an integrated luminosity of 976 pb-1 is presented. The standard model predicts a low rate of trilepton events, which makes some supersymmetric processes, such as chargino-neutralino production, measurable in this channel. The μμ+ signature is investigated, where ℓ is an electron or a muon, with the additional requirement of large missing transverse energy. In this analysis, the lepton transverse momenta with respect to the beam direction (pT) are as low as 5GeV/c, a selection that improves the sensitivity to particles that are light as well as to ones that result in leptonically decaying tau leptons. At the same time, this low-pT selection presents additional challenges due to the non-negligible heavy-quark background at low lepton momenta. This background is measured with an innovative technique using experimental data. Several dimuon and trilepton control regions are investigated, and good agreement between experimental results and standard-model predictions is observed. In the signal region, we observe one three-muon event and expect 0.4±0.1μμ+ events from standard-model processes. © 2009 The American Physical Society.
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Study of D0→π-e+νe, D+→π0e+νe, D0→K-e+νe, and D+→K̄0e+νe in tagged decays of the ψ(3770) resonance

Physical Review D - Particles, Fields, Gravitation and Cosmology 79:5 (2009)

Authors:

JY Ge, DH Miller, V Pavlunin, B Sanghi, IPJ Shipsey, B Xin, GS Adams, D Hu, B Moziak, J Napolitano, KM Ecklund, Q He, J Insler, H Muramatsu, CS Park, EH Thorndike, F Yang, YS Gao, F Liu, M Artuso, S Blusk, S Khalil, J Li, R Mountain, K Randrianarivony, N Sultana, T Skwarnicki, S Stone, JC Wang, LM Zhang, G Bonvicini, D Cinabro, M Dubrovin, A Lincoln, P Naik, J Rademacker, DM Asner, KW Edwards, J Reed, RA Briere, G Tatishvili, H Vogel, PUE Onyisi, JL Rosner, JP Alexander, DG Cassel, JE Duboscq, R Ehrlich, L Fields, L Gibbons, R Gray, SW Gray, DL Hartill, BK Heltsley, D Hertz, JM Hunt, J Kandaswamy, DL Kreinick, VE Kuznetsov, J Ledoux, H Mahlke-Krüger, D Mohapatra, JR Patterson, D Peterson, D Riley, A Ryd, AJ Sadoff, X Shi, S Stroiney, WM Sun, T Wilksen, SB Athar, J Yelton, P Rubin, S Mehrabyan, N Lowrey, M Selen, EJ White, J Wiss, RE Mitchell, MR Shepherd, D Besson, TK Pedlar, D Cronin-Hennessy, KY Gao, J Hietala, Y Kubota, T Klein, BW Lang, R Poling, AW Scott, P Zweber, S Dobbs, Z Metreveli, KK Seth, BJY Tan, A Tomaradze, J Libby, L Martin, A Powell

Abstract:

Using ψ(3770)→DD̄ events collected with the CLEO-c detector at the Cornell e+e- storage ring, tagged by fully reconstructing one D meson in a hadronic decay mode, we measure absolute branching fractions and differential decay rates for D0→π-e+νe, D+→π0e+νe, D0→K-e+νe, and D+→K̄0e+νe. The measured decay rates are used to study semileptonic form factors governing these transitions and to test unquenched Lattice QCD (LQCD) calculations. We average our results with previously published CLEO-c measurements of the same quantities using a neutrino reconstruction technique. Combining LQCD calculations of form factor absolute normalizations f+(0) and measurements of f+π(0)|Vcd| and f+K(0)|Vcs|, we find |Vcd|=0.222(8)(3)(23) and |Vcs|=1.018(10)(8)(106), where the uncertainties are statistical, experimental systematic, and from LQCD, respectively. © 2009 The American Physical Society.
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A study of bb̄ production in e+e- collisions at √ = 130-207 GeV

European Physical Journal C 60:1 (2009) 1-15

Authors:

J Abdallah, P Abreu, W Adam, P Adzic, T Albrecht, R Alemany-Fernandez, T Allmendinger, PP Allport, U Amaldi, N Amapane, S Amato, E Anashkin, A Andreazza, S Andringa, N Anjos, P Antilogus, WD Apel, Y Arnoud, S Ask, B Asman, JE Augustin, A Augustinus, P Baillon, A Ballestrero, P Bambade, R Barbier, D Bardin, GJ Barker, A Baroncelli, M Battaglia, M Baubillier, KH Becks, M Begalli, A Behrmann, E Ben-Haim, N Benekos, A Benvenuti, C Berat, M Berggren, D Bertrand, M Besancon, N Besson, D Bloch, M Blom, M Bluj, M Bonesini, M Boonekamp, PSL Booth, G Borisov, O Botner, B Bouquet, TJV Bowcock, I Boyko, M Bracko, R Brenner, E Brodet, P Bruckman, JM Brunet, B Buschbeck, P Buschmann, M Calvi, T Camporesi, V Canale, F Carena, N Castro, F Cavallo, M Chapkin, P Charpentier, P Checchia, R Chierici, P Chliapnikov, J Chudoba, SU Chung, K Cieslik, P Collins, R Contri, G Cosme, F Cossutti, MJ Costa, D Crennell, J Cuevas, J D'Hondt, T Da Silva, W Da Silva, G Della Ricca, A De Angelis, W De Boer, C De Clercq, B De Lotto, N De Maria, A De Min, L De Paula, L Di Ciaccio, A Di Simone, K Doroba, J Drees, G Eigen, T Ekelof, M Ellert, M Elsing

Abstract:

Measurements are presented of R b, the ratio of the cross-section to the cross-section in e+e- collisions, and the forward-backward asymmetry A FBb at twelve energy points in the range sqrt{s}=130-207 GeV. These results are found to be consistent with the Standard Model expectations. The measurements are used to set limits on new physics scenarios involving contact interactions. © 2009 Springer-Verlag / Società Italiana di Fisica.
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Measurement of the fraction of tt̄ production via gluon-gluon fusion in pp̄ collisions at s=1.96TeV

Physical Review D - Particles, Fields, Gravitation and Cosmology 79:3 (2009)

Authors:

T Aaltonen, J Adelman, T Akimoto, MG Albrow, B Álvarez González, S Amerio, D Amidei, A Anastassov, A Annovi, J Antos, G Apollinari, A Apresyan, T Arisawa, A Artikov, W Ashmanskas, A Attal, A Aurisano, F Azfar, P Azzurri, W Badgett, A Barbaro-Galtieri, VE Barnes, BA Barnett, V Bartsch, G Bauer, PH Beauchemin, F Bedeschi, P Bednar, D Beecher, S Behari, G Bellettini, J Bellinger, D Benjamin, A Beretvas, J Beringer, A Bhatti, M Binkley, D Bisello, I Bizjak, RE Blair, C Blocker, B Blumenfeld, A Bocci, A Bodek, V Boisvert, G Bolla, D Bortoletto, J Boudreau, A Boveia, B Brau, A Bridgeman, L Brigliadori, C Bromberg, E Brubaker, J Budagov, HS Budd, S Budd, K Burkett, G Busetto, P Bussey, A Buzatu, KL Byrum, S Cabrera, C Calancha, M Campanelli, M Campbell, F Canelli, A Canepa, D Carlsmith, R Carosi, S Carrillo, S Carron, B Casal, M Casarsa, A Castro, P Catastini, D Cauz, V Cavaliere, M Cavalli-Sforza, A Cerri, L Cerrito, SH Chang, YC Chen, M Chertok, G Chiarelli, G Chlachidze, F Chlebana, K Cho, D Chokheli, JP Chou, G Choudalakis, SH Chuang, K Chung, WH Chung, YS Chung, CI Ciobanu, MA Ciocci, A Clark, D Clark, G Compostella

Abstract:

We present a measurement of the ratio of the tt̄ production cross section via gluon-gluon fusion to the total tt̄ production cross section in pp̄ collisions at s=1.96TeV at the Tevatron. Using a data sample with an integrated luminosity of 955pb-1 recorded by the CDF II detector at Fermilab, we select events based on the tt̄ decay to lepton+jets. Using an artificial neural network technique we discriminate between tt̄ events produced via qq̄ annihilation and gg fusion, and find Gf=σ(gg→tt̄)/ σ(pp̄→tt̄)<0.33 at the 68% confidence level. This result is combined with a previous measurement to obtain the most stringent measurement of this quantity by CDF to date, Gf=0.07-0.07+0.15. © 2009 The American Physical Society.
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Observation of η′ decays to π+π-π0 and π+π-e+e-

Physical Review Letters 102:6 (2009)

Authors:

P Naik, J Rademacker, DM Asner, KW Edwards, J Reed, AN Robichaud, G Tatishvili, RA Briere, H Vogel, PUE Onyisi, JL Rosner, JP Alexander, DG Cassel, JE Duboscq, R Ehrlich, L Fields, RS Galik, L Gibbons, R Gray, SW Gray, DL Hartill, BK Heltsley, D Hertz, JM Hunt, J Kandaswamy, DL Kreinick, VE Kuznetsov, J Ledoux, H Mahlke-Krüger, D Mohapatra, JR Patterson, D Peterson, D Riley, A Ryd, AJ Sadoff, X Shi, S Stroiney, WM Sun, T Wilksen, SB Athar, J Yelton, P Rubin, S Mehrabyan, N Lowrey, M Selen, EJ White, J Wiss, RE Mitchell, MR Shepherd, D Besson, TK Pedlar, D Cronin-Hennessy, KY Gao, J Hietala, Y Kubota, T Klein, R Poling, AW Scott, P Zweber, S Dobbs, Z Metreveli, KK Seth, BJY Tan, A Tomaradze, J Libby, L Martin, A Powell, G Wilkinson, H Mendez, JY Ge, DH Miller, V Pavlunin, B Sanghi, IPJ Shipsey, B Xin, GS Adams, D Hu, B Moziak, J Napolitano, Q He, J Insler, H Muramatsu, CS Park, EH Thorndike, F Yang, M Artuso, S Blusk, S Khalil, J Li, R Mountain, K Randrianarivony, N Sultana, T Skwarnicki, S Stone, JC Wang, LM Zhang, G Bonvicini, D Cinabro, M Dubrovin, A Lincoln

Abstract:

Using ψ(2S)→π+π-J/ψ, J/ψ→γη′ events acquired with the CLEO-c detector at the CESR e+e- collider, we make the first observations of the decays η′→π+π-π0 and η′→π+π-e+e-, measuring absolute branching fractions (37-9+11±4)×10-4 and (25-9+12±5)×10-4, respectively. For η′→π+π-π0, this result probes the mechanism of isospin violation and the roles of π0/η/η′-mixing and final state rescattering in strong decays. We also set upper limits on branching fractions for η′ decays to π+π-μ+μ-, 2(π+π-), π+π-2π0, 2(π+π-)π0, 3(π+π-), and invisible final states. © 2009 The American Physical Society.
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