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Measurement of the helicity fractions of W bosons from top quark decays using fully reconstructed tt̄ events with CDF II

Physical Review D - Particles, Fields, Gravitation and Cosmology 75:5 (2007)

Authors:

A Abulencia, J Adelman, T Affolder, T Akimoto, MG Albrow, D Ambrose, S Amerio, D Amidei, A Anastassov, K Anikeev, A Annovi, J Antos, M Aoki, G Apollinari, JF Arguin, T Arisawa, A Artikov, W Ashmanskas, A Attal, F Azfar, P Azzi-Bacchetta, P Azzurri, N Bacchetta, W Badgett, A Barbaro-Galtieri, VE Barnes, BA Barnett, S Baroiant, V Bartsch, G Bauer, F Bedeschi, S Behari, S Belforte, G Bellettini, J Bellinger, A Belloni, D Benjamin, A Beretvas, J Beringer, T Berry, A Bhatti, M Binkley, D Bisello, RE Blair, C Blocker, B Blumenfeld, A Bocci, A Bodek, V Boisvert, G Bolla, A Bolshov, D Bortoletto, J Boudreau, A Boveia, B Brau, L Brigliadori, C Bromberg, E Brubaker, J Budagov, HS Budd, S Budd, S Budroni, K Burkett, G Busetto, P Bussey, KL Byrum, S Cabrera, M Campanelli, M Campbell, F Canelli, A Canepa, S Carillo, D Carlsmith, R Carosi, M Casarsa, A Castro, P Catastini, D Cauz, M Cavalli-Sforza, A Cerri, L Cerrito, SH Chang, YC Chen, M Chertok, G Chiarelli, G Chlachidze, F Chlebana, I Cho, K Cho, D Chokheli, JP Chou, G Choudalakis, SH Chuang, K Chung, WH Chung, YS Chung, T Chwalek, M Ciljak, CI Ciobanu, MA Ciocci

Abstract:

We present a measurement of the fractions F0 and F+ of longitudinally polarized and right-handed W bosons in top-quark decays using data collected with the CDF II detector. The data set used in the analysis corresponds to an integrated luminosity of approximately 318pb-1. We select tt̄ candidate events with one lepton, at least four jets, and missing transverse energy. Our helicity measurement uses the decay angle θ*, which is defined as the angle between the momentum of the charged lepton in the W boson rest frame and the W momentum in the top-quark rest frame. The cos θ* distribution in the data is determined by full kinematic reconstruction of the tt̄ candidates. We find F0=0.85-0.22+0.15(stat)±0.06(syst) and F+=0.05-0.05+0.11(stat)±0.03(syst), which is consistent with the standard model prediction. We set an upper limit on the fraction of right-handed W bosons of F+<0.26 at the 95% confidence level. © 2007 The American Physical Society.
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Observation of exclusive electron-positron production in hadron-hadron collisions

Physical Review Letters 98:11 (2007)

Authors:

A Abulencia, J Adelman, T Affolder, T Akimoto, MG Albrow, D Ambrose, S Amerio, D Amidei, A Anastassov, K Anikeev, A Annovi, J Antos, M Aoki, G Apollinari, JF Arguin, T Arisawa, A Artikov, W Ashmanskas, A Attal, F Azfar, P Azzi-Bacchetta, P Azzurri, N Bacchetta, W Badgett, A Barbaro-Galtieri, VE Barnes, BA Barnett, S Baroiant, V Bartsch, G Bauer, F Bedeschi, S Behari, S Belforte, G Bellettini, J Bellinger, A Belloni, D Benjamin, A Beretvas, J Beringer, T Berry, A Bhatti, M Binkley, D Bisello, RE Blair, C Blocker, B Blumenfeld, A Bocci, A Bodek, V Boisvert, G Bolla, A Bolshov, D Bortoletto, J Boudreau, A Boveia, B Brau, L Brigliadori, C Bromberg, E Brubaker, J Budagov, HS Budd, S Budd, S Budroni, K Burkett, G Busetto, P Bussey, KL Byrum, S Cabrera, M Campanelli, M Campbell, F Canelli, A Canepa, S Carillo, D Carlsmith, B Caron, R Carosi, M Casarsa, A Castro, P Catastini, D Cauz, M Cavalli-Sforza, A Cerri, L Cerrito, SH Chang, YC Chen, M Chertok, G Chiarelli, G Chlachidze, F Chlebana, I Cho, K Cho, D Chokheli, JP Chou, G Choudalakis, SH Chuang, K Chung, WH Chung, YS Chung, M Ciljak, CI Ciobanu, MA Ciocci

Abstract:

We present the first observation of exclusive e+e- production in hadron-hadron collisions, using pp̄ collision data at s=1.96TeV taken by the run II Collider Detector at Fermilab, and corresponding to an integrated luminosity of 532pb-1. We require the absence of any particle signatures in the detector except for an electron and a positron candidate, each with transverse energy ET>5GeV and pseudorapidity |η|<2. With these criteria, 16 events are observed compared to a background expectation of 1.9±0.3 events. These events are consistent in cross section and properties with the QED process pp̄→p+e+e-+p̄ through two-photon exchange. The measured cross section is 1.6-0.3+0.5(stat)±0.3(syst)pb. This agrees with the theoretical prediction of 1.71±0.01pb. © 2007 The American Physical Society.
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The front-end (Level-0) electronics interface module for the LHCb RICH detectors

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 572 (2007) 689-697

Authors:

N Harnew, M. Adinolfi, J. H. Bibby, J. Libby
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Precision measurement of the top-quark mass from dilepton events at CDF II

Physical Review D - Particles, Fields, Gravitation and Cosmology 75:3 (2007)

Authors:

A Abulencia, J Adelman, T Affolder, T Akimoto, MG Albrow, D Ambrose, S Amerio, D Amidei, A Anastassov, K Anikeev, A Annovi, J Antos, M Aoki, G Apollinari, JF Arguin, T Arisawa, A Artikov, W Ashmanskas, A Attal, F Azfar, P Azzi-Bacchetta, P Azzurri, N Bacchetta, W Badgett, A Barbaro-Galtieri, VE Barnes, BA Barnett, S Baroiant, V Bartsch, G Bauer, F Bedeschi, S Behari, S Belforte, G Bellettini, J Bellinger, A Belloni, D Benjamin, A Beretvas, J Beringer, T Berry, A Bhatti, M Binkley, D Bisello, RE Blair, C Blocker, B Blumenfeld, A Bocci, A Bodek, V Boisvert, G Bolla, A Bolshov, D Bortoletto, J Boudreau, A Boveia, B Brau, L Brigliadori, C Bromberg, E Brubaker, J Budagov, HS Budd, S Budd, S Budroni, K Burkett, G Busetto, P Bussey, KL Byrum, S Cabrera, M Campanelli, M Campbell, F Canelli, A Canepa, S Carillo, D Carlsmith, R Carosi, S Carron, M Casarsa, A Castro, P Catastini, D Cauz, M Cavalli-Sforza, A Cerri, L Cerrito, SH Chang, YC Chen, M Chertok, G Chiarelli, G Chlachidze, F Chlebana, I Cho, K Cho, D Chokheli, JP Chou, G Choudalakis, SH Chuang, K Chung, WH Chung, YS Chung, M Ciljak, CI Ciobanu, MA Ciocci

Abstract:

We report a measurement of the top-quark mass, Mt, in the dilepton decay channel of tt̄→b ′+ν ′b̄ -ν̄ using an integrated luminosity of 1.0fb-1 of pp̄ collisions collected with the CDF II detector. We apply a method that convolutes a leading-order matrix element with detector resolution functions to form event-by-event likelihoods; we have enhanced the leading-order description to describe the effects of initial-state radiation. The joint likelihood is the product of the likelihoods from 78 candidate events in this sample, which yields a measurement of Mt=164.5±3.9(stat.)±3.9(syst.)GeV/c2, the most precise measurement of Mt in the dilepton channel. © 2007 The American Physical Society.
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Observation of decays B0→Ds(*)+π- and B0→Ds(*)-K+

Physical Review Letters 98:8 (2007)

Authors:

B Aubert, R Barate, M Bona, D Boutigny, F Couderc, Y Karyotakis, JP Lees, V Poireau, V Tisserand, A Zghiche, E Grauges, A Palano, JC Chen, ND Qi, G Rong, P Wang, YS Zhu, G Eigen, I Ofte, B Stugu, GS Abrams, M Battaglia, DN Brown, J Button-Shafer, RN Cahn, E Charles, MS Gill, Y Groysman, RG Jacobsen, JA Kadyk, LT Kerth, YG Kolomensky, G Kukartsev, G Lynch, LM Mir, PJ Oddone, TJ Orimoto, M Pripstein, NA Roe, MT Ronan, A Suzuki, D Troost, WA Wenzel, M Barrett, KE Ford, TJ Harrison, AJ Hart, CM Hawkes, SE Morgan, AT Watson, K Goetzen, T Held, H Koch, B Lewandowski, M Pelizaeus, K Peters, T Schroeder, M Steinke, JT Boyd, JP Burke, WN Cottingham, D Walker, T Cuhadar-Donszelmann, BG Fulsom, C Hearty, NS Knecht, TS Mattison, JA McKenna, A Khan, P Kyberd, M Saleem, L Teodorescu, VE Blinov, AD Bukin, VP Druzhinin, VB Golubev, AP Onuchin, SI Serednyakov, YI Skovpen, EP Solodov, KY Todyshev, DS Best, M Bondioli, M Bruinsma, M Chao, S Curry, I Eschrich, D Kirkby, AJ Lankford, P Lund, M Mandelkern, RK Mommsen, W Roethel, DP Stoker, S Abachi, C Buchanan, SD Foulkes, JW Gary, O Long, BC Shen

Abstract:

We report the observation of decays B0→Ds(*)+π- and B0→Ds(*)-K+ in a sample of 230×106 Υ(4S)→BB̄ events recorded with the BABAR detector at the SLAC PEP-II asymmetric-energy e+e- storage ring. We measure the branching fractions B(B0→Ds+π-)=(1. 3±0.3(stat)±0.2(syst))×10-5, B(B0→Ds-K+)=(2.5±0. 4(stat)±0.4(syst))×10-5, B(B0→Ds*+π-)=(2.8±0. 6(stat)±0.5(syst))×10-5, and B(B0→Ds*-K+)=(2.0±0. 5(stat)±0.4(syst))×10-5. The significances of the measurements to differ from zero are 5, 9, 6, and 5 standard deviations, respectively. This is the first observation of B0→Ds+π-, B0→Ds*+π-, and B0→Ds*-K+ decays. © 2007 The American Physical Society.
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