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LSST/Rubin Dome Bridge Installation
Credit: Rubin Obs/NSF/AURA

Dr Farrukh Azfar

Lecturer

Research theme

  • Particle astrophysics & cosmology
  • Fundamental particles and interactions

Sub department

  • Particle Physics

Research groups

  • Accelerator Neutrinos
  • Rubin-LSST
Farrukh.Azfar@physics.ox.ac.uk
Telephone: 01865 (2)73327
Denys Wilkinson Building, room 669
  • About
  • Publications

Analysis of the quantum numbers J(PC) of the X(3872) particle.

Phys Rev Lett 98:13 (2007) 132002

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, J-F 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, M Ciljak, CI Ciobanu, MA Ciocci, A Clark, D Clark, M Coca, G Compostella, ME Convery, J Conway, B Cooper, K Copic, M Cordelli, G Cortiana, F Crescioli, C Cuenca Almenar, J Cuevas, R Culbertson, JC Cully, D Cyr, S Daronco, M Datta, S D'Auria, T Davies, M D'Onofrio, D Dagenhart, P de Barbaro, S De Cecco, A Deisher, G De Lentdecker, M Dell'Orso, F Delli Paoli, L Demortier, J Deng, M Deninno, D De Pedis, PF Derwent, GP Di Giovanni, C Dionisi, B Di Ruzza, JR Dittmann, P DiTuro, C Dörr, S Donati, M Donega, P Dong, J Donini, T Dorigo, S Dube, J Efron, R Erbacher, D Errede, S Errede, R Eusebi, HC Fang, S Farrington, I Fedorko, WT Fedorko, RG Feild, M Feindt, JP Fernandez, R Field, G Flanagan, A Foland, S Forrester, GW Foster, M Franklin, JC Freeman, I Furic, M Gallinaro, J Galyardt, JE Garcia, F Garberson, AF Garfinkel, C Gay, H Gerberich, D Gerdes, S Giagu, P Giannetti, A Gibson, K Gibson, JL Gimmell, C Ginsburg, N Giokaris, M Giordani, P Giromini, M Giunta, G Giurgiu, V Glagolev, D Glenzinski, M Gold, N Goldschmidt, J Goldstein, A Golossanov, G Gomez, G Gomez-Ceballos, M Goncharov, O González, I Gorelov, AT Goshaw, K Goulianos, A Gresele, M Griffiths, S Grinstein, C Grosso-Pilcher, U Grundler, J Guimaraes da Costa, Z Gunay-Unalan, C Haber, K Hahn, SR Hahn, E Halkiadakis, A Hamilton, B-Y Han, JY Han, R Handler, F Happacher, K Hara, M Hare, S Harper, RF Harr, RM Harris, M Hartz, K Hatakeyama, J Hauser, A Heijboer, B Heinemann, J Heinrich, C Henderson, M Herndon, J Heuser, D Hidas, CS Hill, D Hirschbuehl, A Hocker, A Holloway, S Hou, M Houlden, S-C Hsu, BT Huffman, RE Hughes, U Husemann, J Huston, J Incandela, G Introzzi, M Iori, Y Ishizawa, A Ivanov, B Iyutin, E James, D Jang, B Jayatilaka, D Jeans, H Jensen, EJ Jeon, S Jindariani, M Jones, KK Joo, SY Jun, JE Jung, TR Junk, T Kamon, PE Karchin, Y Kato, Y Kemp, R Kephart, U Kerzel, V Khotilovich, B Kilminster, DH Kim, HS Kim, JE Kim, MJ Kim, SB Kim, SH Kim, YK Kim, N Kimura, L Kirsch, S Klimenko, M Klute, B Knuteson, BR Ko, K Kondo, DJ Kong, J Konigsberg, A Korytov, AV Kotwal, A Kovalev, AC Kraan, J Kraus, I Kravchenko, M Kreps, J Kroll, N Krumnack, M Kruse, V Krutelyov, T Kubo, SE Kuhlmann, T Kuhr, Y Kusakabe, S Kwang, AT Laasanen, S Lai, S Lami, S Lammel, M Lancaster, RL Lander, K Lannon, A Lath, G Latino, I Lazzizzera, T LeCompte, J Lee, J Lee, YJ Lee, SW Lee, R Lefèvre, N Leonardo, S Leone, S Levy, JD Lewis, C Lin, CS Lin, M Lindgren, E Lipeles, A Lister, DO Litvintsev, T Liu, NS Lockyer, A Loginov, M Loreti, P Loverre, R-S Lu, D Lucchesi, P Lujan, P Lukens, G Lungu, L Lyons, J Lys, R Lysak, E Lytken, P Mack, D MacQueen, R Madrak, K Maeshima, K Makhoul, T Maki, P Maksimovic, S Malde, G Manca, F Margaroli, R Marginean, C Marino, CP Marino, A Martin, M Martin, V Martin, M Martínez, T Maruyama, P Mastrandrea, T Masubuchi, H Matsunaga, ME Mattson, R Mazini, P Mazzanti, KS McFarland, P McIntyre, R McNulty, A Mehta, P Mehtala, S Menzemer, A Menzione, P Merkel, C Mesropian, A Messina, T Miao, N Miladinovic, J Miles, R Miller, C Mills, M Milnik, A Mitra, G Mitselmakher, A Miyamoto, S Moed, N Moggi, B Mohr, R Moore, M Morello, P Movilla Fernandez, J Mülmenstädt, A Mukherjee, Th Muller, R Mumford, P Murat, J Nachtman, A Nagano, J Naganoma, I Nakano, A Napier, V Necula, C Neu, MS Neubauer, J Nielsen, T Nigmanov, L Nodulman, O Norniella, E Nurse, SH Oh, YD Oh, I Oksuzian, T Okusawa, R Oldeman, R Orava, K Osterberg, C Pagliarone, E Palencia, V Papadimitriou, AA Paramonov, B Parks, S Pashapour, J Patrick, G Pauletta, M Paulini, C Paus, DE Pellett, A Penzo, TJ Phillips, G Piacentino, J Piedra, L Pinera, K Pitts, C Plager, L Pondrom, X Portell, O Poukhov, N Pounder, F Prakoshyn, A Pronko, J Proudfoot, F Ptohos, G Punzi, J Pursley, J Rademacker, A Rahaman, N Ranjan, S Rappoccio, B Reisert, V Rekovic, P Renton, M Rescigno, S Richter, F Rimondi, L Ristori, A Robson, T Rodrigo, E Rogers, S Rolli, R Roser, M Rossi, R Rossin, A Ruiz, J Russ, V Rusu, H Saarikko, S Sabik, A Safonov, WK Sakumoto, G Salamanna, O Saltó, D Saltzberg, C Sánchez, L Santi, S Sarkar, L Sartori, K Sato, P Savard, A Savoy-Navarro, T Scheidle, P Schlabach, EE Schmidt, MP Schmidt, M Schmitt, T Schwarz, L Scodellaro, AL Scott, A Scribano, F Scuri, A Sedov, S Seidel, Y Seiya, A Semenov, L Sexton-Kennedy, A Sfyrla, MD Shapiro, T Shears, PF Shepard, D Sherman, M Shimojima, M Shochet, Y Shon, I Shreyber, A Sidoti, P Sinervo, A Sisakyan, J Sjolin, AJ Slaughter, J Slaunwhite, K Sliwa, JR Smith, FD Snider, R Snihur, M Soderberg, A Soha, S Somalwar, V Sorin, J Spalding, F Spinella, T Spreitzer, P Squillacioti, M Stanitzki, A Staveris-Polykalas, R St Denis, B Stelzer, O Stelzer-Chilton, D Stentz, J Strologas, D Stuart, JS Suh, A Sukhanov, H Sun, T Suzuki, A Taffard, R Takashima, Y Takeuchi, K Takikawa, M Tanaka, R Tanaka, M Tecchio, PK Teng, K Terashi, J Thom, AS Thompson, E Thomson, P Tipton, V Tiwari, S Tkaczyk, D Toback, S Tokar, K Tollefson, T Tomura, D Tonelli, S Torre, D Torretta, S Tourneur, W Trischuk, R Tsuchiya, S Tsuno, N Turini, F Ukegawa, T Unverhau, S Uozumi, D Usynin, S Vallecorsa, N van Remortel, A Varganov, E Vataga, F Vázquez, G Velev, G Veramendi, V Veszpremi, R Vidal, I Vila, R Vilar, T Vine, I Vollrath, I Volobouev, G Volpi, F Würthwein, P Wagner, RG Wagner, RL Wagner, J Wagner, W Wagner, R Wallny, SM Wang, A Warburton, S Waschke, D Waters, WC Wester, B Whitehouse, D Whiteson, AB Wicklund, E Wicklund, G Williams, HH Williams, P Wilson, BL Winer, P Wittich, S Wolbers, C Wolfe, T Wright, X Wu, SM Wynne, A Yagil, K Yamamoto, J Yamaoka, T Yamashita, C Yang, UK Yang, YC Yang, WM Yao, GP Yeh, J Yoh, K Yorita, T Yoshida, GB Yu, I Yu, SS Yu, JC Yun, L Zanello, A Zanetti, I Zaw, X Zhang, J Zhou, S Zucchelli, CDF Collaboration

Abstract:

We present an analysis of angular distributions and correlations of the X(3872) particle in the exclusive decay mode X(3872)-->J/psipi+ pi- with J/psi-->mu+ mu-. We use 780 pb-1 of data from pp[over ] collisions at sqrt[s]=1.96 TeV collected with the CDF II detector at the Fermilab Tevatron. We derive constraints on spin, parity, and charge conjugation parity of the X(3872) particle by comparing measured angular distributions of the decay products with predictions for different J(PC) hypotheses. The assignments J(PC)=1++ and 2-+ are the only ones consistent with the data.
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Measurement of the Λb0 Lifetime in Λb0→J/ψΛ0 in pp̄ Collisions at s=1.96TeV

Physical Review Letters 98:12 (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 Carrillo, 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 Λb0 lifetime in the exclusive decay Λb0→J/ψΛ0 in pp̄ collisions at s=1.96TeV using an integrated luminosity of 1.0fb-1 of data collected by the CDF II detector at the Fermilab Tevatron. Using fully reconstructed decays, we measure τ(Λb0)=1.593-0.078+0.083(stat)±0.033(syst)ps. This is the single most precise measurement of τ(Λb0) and is 3.2σ higher than the current world average. © 2007 The American Physical Society.
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Measurement of σΛb0/ σB̄0×B(Λb0→Λc+π-)/B(B̄0→D+π- ) in pp̄ Collisions at s=1.96TeV

Physical Review Letters 98:12 (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, M Ciljak, CI Ciobanu, MA Ciocci, A Clark

Abstract:

We present the first observation of the baryon decay Λb0→ Λc+π- followed by Λc+→pK-π+ in 106pb-1 pp̄ collisions at s=1.96TeV in the CDF experiment. In order to reduce systematic error, the measured rate for Λb0 decay is normalized to the kinematically similar meson decay B̄0→D+π- followed by D+→π+K-π+. We report the ratio of production cross sections (σ) times the ratio of branching fractions (B) for the momentum region integrated above pT>6GeV/c and pseudorapidity range |η|<1.3: σ(pp̄→Λb0X)/ σ(pp̄→B̄0X)×B(Λb0→Λc+π-)/ B(B̄0→D+π-)=0.82±0.08(stat)±0.11(syst)±0. 22[B(Λc+→pK-π+)]. © 2007 The American Physical Society.
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Observation of exclusive electron-positron production in hadron-hadron collisions.

Phys Rev Lett 98:11 (2007) 112001

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, J-F 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, A Clark, D Clark, M Coca, G Compostella, ME Convery, J Conway, B Cooper, K Copic, M Cordelli, G Cortiana, F Crescioli, C Cuenca Almenar, J Cuevas, R Culbertson, JC Cully, D Cyr, S Daronco, S D'Auria, T Davies, M D'Onofrio, D Dagenhart, P de Barbaro, S De Cecco, A Deisher, G De Lentdecker, M Dell'orso, F Delli Paoli, L Demortier, J Deng, M Deninno, D De Pedis, PF Derwent, GP Di Giovanni, C Dionisi, B Di Ruzza, JR Dittmann, P Dituro, C Dörr, S Donati, M Donega, P Dong, J Donini, T Dorigo, S Dube, J Efron, R Erbacher, D Errede, S Errede, R Eusebi, HC Fang, S Farrington, I Fedorko, WT Fedorko, RG Feild, M Feindt, JP Fernandez, R Field, G Flanagan, A Foland, S Forrester, GW Foster, M Franklin, JC Freeman, I Furic, M Gallinaro, J Galyardt, JE Garcia, F Garberson, AF Garfinkel, C Gay, H Gerberich, D Gerdes, S Giagu, P Giannetti, A Gibson, K Gibson, JL Gimmell, C Ginsburg, N Giokaris, M Giordani, P Giromini, M Giunta, G Giurgiu, V Glagolev, D Glenzinski, M Gold, N Goldschmidt, J Goldstein, G Gomez, G Gomez-Ceballos, M Goncharov, O González, I Gorelov, AT Goshaw, K Goulianos, A Gresele, M Griffiths, S Grinstein, C Grosso-Pilcher, U Grundler, J Guimaraes da Costa, Z Gunay-Unalan, C Haber, K Hahn, SR Hahn, E Halkiadakis, A Hamilton, B-Y Han, JY Han, R Handler, F Happacher, K Hara, M Hare, S Harper, RF Harr, RM Harris, M Hartz, K Hatakeyama, J Hauser, A Heijboer, B Heinemann, J Heinrich, C Henderson, M Herndon, J Heuser, D Hidas, CS Hill, D Hirschbuehl, A Hocker, A Holloway, S Hou, M Houlden, S-C Hsu, BT Huffman, RE Hughes, U Husemann, J Huston, J Incandela, G Introzzi, M Iori, Y Ishizawa, A Ivanov, B Iyutin, E James, D Jang, B Jayatilaka, D Jeans, H Jensen, EJ Jeon, S Jindariani, M Jones, KK Joo, SY Jun, JE Jung, TR Junk, T Kamon, PE Karchin, Y Kato, Y Kemp, R Kephart, U Kerzel, V Khotilovich, B Kilminster, DH Kim, HS Kim, JE Kim, MJ Kim, SB Kim, SH Kim, YK Kim, N Kimura, L Kirsch, S Klimenko, M Klute, B Knuteson, BR Ko, K Kondo, DJ Kong, J Konigsberg, A Korytov, AV Kotwal, A Kovalev, AC Kraan, J Kraus, I Kravchenko, M Kreps, J Kroll, N Krumnack, M Kruse, V Krutelyov, T Kubo, SE Kuhlmann, T Kuhr, Y Kusakabe, S Kwang, AT Laasanen, S Lai, S Lami, S Lammel, M Lancaster, RL Lander, K Lannon, A Lath, G Latino, I Lazzizzera, T Lecompte, J Lee, J Lee, YJ Lee, SW Lee, R Lefèvre, N Leonardo, S Leone, S Levy, JD Lewis, C Lin, CS Lin, M Lindgren, E Lipeles, A Lister, DO Litvintsev, T Liu, NS Lockyer, A Loginov, M Loreti, P Loverre, R-S Lu, D Lucchesi, P Lujan, P Lukens, G Lungu, L Lyons, J Lys, R Lysak, E Lytken, P Mack, D Macqueen, R Madrak, K Maeshima, K Makhoul, T Maki, P Maksimovic, S Malde, G Manca, F Margaroli, R Marginean, C Marino, CP Marino, A Martin, M Martin, V Martin, M Martínez, T Maruyama, P Mastrandrea, T Masubuchi, H Matsunaga, ME Mattson, R Mazini, P Mazzanti, KS McFarland, P McIntyre, R McNulty, A Mehta, P Mehtala, S Menzemer, A Menzione, P Merkel, C Mesropian, A Messina, T Miao, N Miladinovic, J Miles, R Miller, C Mills, M Milnik, A Mitra, G Mitselmakher, A Miyamoto, S Moed, N Moggi, B Mohr, R Moore, M Morello, P Movilla Fernandez, J Mülmenstädt, A Mukherjee, Th Muller, R Mumford, P Murat, J Nachtman, A Nagano, J Naganoma, I Nakano, A Napier, V Necula, C Neu, MS Neubauer, J Nielsen, T Nigmanov, L Nodulman, O Norniella, E Nurse, SH Oh, YD Oh, I Oksuzian, T Okusawa, R Oldeman, R Orava, K Osterberg, C Pagliarone, E Palencia, V Papadimitriou, AA Paramonov, B Parks, S Pashapour, J Patrick, G Pauletta, M Paulini, C Paus, DE Pellett, A Penzo, TJ Phillips, G Piacentino, J Piedra, L Pinera, J Pinfold, K Pitts, C Plager, L Pondrom, X Portell, O Poukhov, N Pounder, F Prakoshyn, A Pronko, J Proudfoot, F Ptohos, G Punzi, J Pursley, J Rademacker, A Rahaman, N Ranjan, S Rappoccio, B Reisert, V Rekovic, P Renton, M Rescigno, S Richter, F Rimondi, L Ristori, A Robson, T Rodrigo, E Rogers, S Rolli, R Roser, M Rossi, R Rossin, A Ruiz, J Russ, V Rusu, H Saarikko, S Sabik, A Safonov, WK Sakumoto, G Salamanna, O Saltó, D Saltzberg, C Sánchez, L Santi, S Sarkar, L Sartori, K Sato, P Savard, A Savoy-Navarro, T Scheidle, P Schlabach, EE Schmidt, MP Schmidt, M Schmitt, T Schwarz, L Scodellaro, AL Scott, A Scribano, F Scuri, A Sedov, S Seidel, Y Seiya, A Semenov, L Sexton-Kennedy, A Sfyrla, MD Shapiro, T Shears, PF Shepard, D Sherman, M Shimojima, M Shochet, Y Shon, I Shreyber, A Sidoti, P Sinervo, A Sisakyan, J Sjolin, AJ Slaughter, J Slaunwhite, K Sliwa, JR Smith, FD Snider, R Snihur, M Soderberg, A Soha, S Somalwar, V Sorin, J Spalding, F Spinella, T Spreitzer, P Squillacioti, M Stanitzki, A Staveris-Polykalas, R St Denis, B Stelzer, O Stelzer-Chilton, D Stentz, J Strologas, D Stuart, JS Suh, A Sukhanov, H Sun, T Suzuki, A Taffard, R Takashima, Y Takeuchi, K Takikawa, M Tanaka, R Tanaka, M Tecchio, PK Teng, K Terashi, J Thom, AS Thompson, E Thomson, P Tipton, V Tiwari, S Tkaczyk, D Toback, S Tokar, K Tollefson, T Tomura, D Tonelli, S Torre, D Torretta, S Tourneur, W Trischuk, R Tsuchiya, S Tsuno, N Turini, F Ukegawa, T Unverhau, S Uozumi, D Usynin, S Vallecorsa, N van Remortel, A Varganov, E Vataga, F Vázquez, G Velev, G Veramendi, V Veszpremi, R Vidal, I Vila, R Vilar, T Vine, I Vollrath, I Volobouev, G Volpi, F Würthwein, P Wagner, RG Wagner, RL Wagner, J Wagner, W Wagner, R Wallny, SM Wang, A Warburton, S Waschke, D Waters, WC Wester, B Whitehouse, D Whiteson, AB Wicklund, E Wicklund, G Williams, HH Williams, P Wilson, BL Winer, P Wittich, S Wolbers, C Wolfe, T Wright, X Wu, SM Wynne, A Yagil, K Yamamoto, J Yamaoka, T Yamashita, C Yang, UK Yang, YC Yang, WM Yao, GP Yeh, J Yoh, K Yorita, T Yoshida, GB Yu, I Yu, SS Yu, JC Yun, L Zanello, A Zanetti, I Zaw, X Zhang, J Zhou, S Zucchelli

Abstract:

We present the first observation of exclusive e(+)e(-) production in hadron-hadron collisions, using pp[over] collision data at (square root) s = 1.96 TeV taken by the run II Collider Detector at Fermilab, and corresponding to an integrated luminosity of 532 pb(-1). We require the absence of any particle signatures in the detector except for an electron and a positron candidate, each with transverse energy E(T) > 5 GeV and pseudorapidity |eta| < 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 pp[over] --> p + e(+)e(-) + p[over] 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+/-0.01 pb.
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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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