Accelerator Neutrinos

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Measurement of the decay rate and the parameter αK* of the decay KL → μμγ

Zeitschrift fur Physik C-Particles and Fields 76:4 (1997) 653-657

Authors:

V Fanti, A Lai, L Musa, A Nappi, MG Setzu, RW Moore, DJ Munday, MA Parker, SF Takach, TO White, G Barr, G Bocquet, J Bremer, A Ceccucci, J Cogan, D Cundy, N Doble, G Fischer, W Funk, L Gatignon, A Gianoli, A Gonidec, P Grafstrom, W Kubischta, V Marzulli, G Kesseler, JP Matheys, A Norton, S Palestini, B Panzer-Steindel, H Taureg, M Velasco, O Vossnack, H Wahl, V Kekelidze, I Kojevnikov, I Potrebenikov, G Tatichvili, A Tkatchev, L Bertolotto, O Boyle, B Hay, NE Mc Kay, G Oakland, H Parsons, KJ Peach, C Talamonti, A Walker, P Dalpiaz, J Duclos, A Formica, PL Frabetti, M Martini, F Petrucci, M Porcu, F Rossi, M Savrie, C Simani, A Bizzeti, M Calvetti, M Lenti, A Michetti, HG Becker, T Beier, H Blümer, P Buchholz, D Coward, C Ebersberger, A Kalter, K Kleinknecht, U Koch, L Köpke, F Leber, S Luitz, B Renk, J Scheidt, J Schmidt, V Schönharting, R Wilhelm, O Zeitnitz, JC Chollet, S Crépé, L Fayard, J Ocariz, G Unal, G Anzivino, P Cenci, P Lubrano, M Pepe, P Calafiura, R Carosi, R Casali, C Cerri, F Costantini, R Fantechi, S Giudici, B Gorini, I Mannelli, G Pierazzini, M Sozzi

Abstract:

The rate of the decay of the neutral K meson into KL0 → μμγ has been measured with the NA48 detector at the CERN SPS. A total of 59 events has been observed with an estimated background of 14 events. The overall Kaon flux was determined to be 1.2 × 109. This observation corresponds to a branching ratio of (3.4 ± 0.6stat ± 0.4sys) × 10-7. Using this branching ratio the parameter αK* describing the relative strength of the two contributing amplitudes to this decay, through intermediate pseudoscalar or vector-like mesons, was measured to be αK*= -0.04-0.21+0.24. © Springer-Verlag 1997.
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Measurement of the top quark pair production cross section in p¯p collisions

Physical Review Letters 79:7 (1997) 1203-1208

Authors:

S Abachi, B Abbott, M Abolins, BS Acharya, I Adam, DL Adams, M Adams, S Ahn, H Aihara, GA Alves, E Amidi, N Amos, EW Anderson, R Astur, MM Baarmand, A Baden, V Balamurali, J Balderston, B Baldin, S Banerjee, J Bantly, JF Bartlett, K Bazizi, A Belyaev, SB Beri, I Bertram, VA Bezzubov, PC Bhat, V Bhatnagar, M Bhattacharjee, N Biswas, G Blazey, S Blessing, P Bloom, A Boehnlein, NI Bojko, F Borcherding, J Borders, C Boswell, A Brandt, R Brock, A Bross, D Buchholz, VS Burtovoi, JM Butler, W Carvalho, D Casey, Z Casilum, H Castilla-Valdez, D Chakraborty, SM Chang, SV Chekulaev, LP Chen, W Chen, S Choi, S Chopra, BC Choudhary, JH Christenson, M Chung, D Claes, AR Clark, WG Cobau, J Cochran, WE Cooper, C Cretsinger, D Cullen-Vidal, MAC Cumings, D Cutts, OI Dahl, K Davis, K De, K Del Signore, M Demarteau, D Denisov, SP Denisov, HT Diehl, M Diesburg, G Di Loreto, P Draper, J Drinkard, Y Ducros, LV Dudko, SR Dugad, D Edmunds, J Ellison, VD Elvira, R Engelmann, S Eno, G Eppley, P Ermolov, OV Eroshin, VN Evdokimov, T Fahland, M Fatyga, MK Fatyga, J Featherly, S Feher, D Fein, T Ferbel, G Finocchiaro

Abstract:

We present a measurement of the t¯t production cross section in p¯p collisions at √s=1.8TeV by the D0 experiment at the Fermilab Tevatron. The measurement is based on data from an integrated luminosity of approximately 125pb−1 accumulated during the 1992–1996 collider run. We observe 39 t¯t candidate events in the dilepton and lepton+jets decay channels with an expected background of 13.7 ± 2.2 events. For a top quark mass of 173.3 GeV/c2, we measure the t¯t production cross section to be 5.5 ± 1.8 pb. © 1997 The American Physical Society.
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Search for a Fourth Generation Charge -1/3 Quark via Flavor Changing Neutral Current Decay

Physical Review Letters 78:20 (1997) 3818-3823

Authors:

S Abachi, B Abbott, M Abolins, BS Acharya, I Adam, DL Adams, M Adams, S Ahn, H Aihara, GA Alves, E Amidi, N Amos, EW Anderson, R Astur, MM Baarmand, A Baden, V Balamurali, J Balderston, B Baldin, S Banerjee, J Bantly, JF Bartlett, K Bazizi, A Belyaev, SB Beri, I Bertram, VA Bezzubov, PC Bhat, V Bhatnagar, M Bhattacharjee, N Biswas, G Blazey, S Blessing, P Bloom, A Boehnlein, NI Bojko, F Borcherding, J Borders, C Boswell, R Brock, A Bross, D Buchholz, VS Burtovoi, JM Butler, W Carvalho, D Casey, H Castilla-Valdez, D Chakraborty, SM Chang, SV Chekulaev, LP Chen, W Chen, S Choi, S Chopra, BC Choudhary, JH Christenson, M Chung, D Claes, AR Clark, WG Cobau, J Cochran, WE Cooper, C Cretsinger, D Cullen-Vidal, MAC Cummings, D Cutts, OI Dahl, K De, K Del Signore, M Demarteau, D Denisov, SP Denisov, HT Diehl, M Diesburg, G Di Loreto, P Draper, J Drinkard, J Alitti, LV Dudko, SR Dugad, D Edmunds, J Ellison, VD Elvira, R Engelmann, S Eno, G Eppley, P Ermolov, OV Eroshin, VN Evdokimov, T Fahland, M Fatyga, MK Fatyga, J Featherly, S Feher, D Fein, T Ferbel, G Finocchiaro, HE Fisk, Y Fisyak

Abstract:

We report on a search for pair production of a fourth generation charge -1/3 quark (b’) in pp collisions at s = 1.8 TeV by the DØ experiment at the Fermilab Tevatron using an integrated luminosity of 93 pb-1. Both b’ quarks are assumed to decay via flavor changing neutral currents (FCNC). The search uses the signatures γ + 3 jets + μ-tag and 2γ + 2 jets. We see no significant excess of events over the expected background. We place an upper limit on the production cross section times branching fraction that is well below theoretical expectations for a b’ decaying exclusively via FCNC for b’ masses up to mz + mb. © 1996 American Physical Society.
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Search for diphoton events with large missing transverse energy in pp collisions at = 1.8 TeV

Physical Review Letters 78:11 (1997) 2070-2074

Authors:

S Abachi, B Abbott, M Abolins, BS Acharya, I Adam, DL Adams, M Adams, S Ahn, H Aihara, G Álvarez, GA Alves, E Amidi, N Amos, EW Anderson, SH Aronson, R Astur, MM Baarmand, A Baden, V Balamurali, J Balderston, B Baldin, S Banerjee, J Bantly, JF Bartlett, K Bazizi, A Belyaev, J Bendich, SB Beri, I Bertram, VA Bezzubov, PC Bhat, V Bhatnagar, M Bhattacharjee, A Bischoff, N Biswas, G Blazey, S Blessing, P Bloom, A Boehnlein, NI Bojko, F Borcherding, J Borders, C Boswell, A Brandt, R Brock, A Bross, D Buchholz, VS Burtovoi, JM Butler, W Carvalho, D Casey, H Castilla-Valdez, D Chakraborty, SM Chang, SV Chekulaev, LP Chen, W Chen, S Choi, S Chopra, BC Choudhary, JH Christenson, M Chung, D Claes, AR Clark, WG Cobau, J Cochran, WE Cooper, C Cretsinger, D Cullen-Vidal, MAC Cummings, D Cutts, OI Dahl, K De, K Del-Signore, M Demarteau, D Denisov, SP Denisov, HT Diehl, M Diesburg, G Di Loreto, P Draper, J Drinkard, Y Ducros, LV Dudko, SR Dugad, D Edmunds, J Ellison, VD Elvira, R Engelmann, S Eno, G Eppley, P Ermolov, OV Eroshin, VN Evdokimov, S Fahey, T Fahland, M Fatyga, MK Fatyga, J Featherly, S Feher

Abstract:

A search for new physics has been carried out in the channel pp → γγ + ET, as expected in various supersymmetric models. We require two photons with transverse energy EγT > 12 GeV and pseudorapidity |ηγ < 1.1. The distribution of missing transverse energy (ET) is consistent with background and no events have ET > 25 GeV. We set limits on production cross sections for selectron, sneutrino, and neutralino pairs, decaying into photons, which range from about 400 fb to 1 pb depending on the sparticle masses. A general limit of 185 fb (95% C.L.) is set on σ(pp → γγET + X), where eγT > 12 GeV, |ηγ| < 1.1, and ET > 25 GeV. © 1997 The American Physical Society.
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Search for scalar leptoquark pairs decaying to electrons and jets in p®p collisions

Physical Review Letters 79:22 (1997) 4321-4326

Authors:

B Abbott, M Abolins, BS Acharya, I Adam, DL Adams, M Adams, S Ahn, H Aihara, GA Alves, E Amidi, N Amos, EW Anderson, R Astur, MM Baarmand, A Baden, V Balamurali, J Balderston, B Baldin, S Banerjee, J Bantly, JF Bartlett, K Bazizi, A Belyaev, SB Beri, I Bertram, VA Bezzubov, PC Bhat, V Bhatnagar, M Bhattacharjee, N Biswas, G Blazey, S Blessing, P Bloom, A Boehnlein, NI Bojko, F Borcherding, C Boswell, A Brandt, R Brock, A Bross, D Buchholz, VS Burtovoi, JM Butler, W Carvalho, D Casey, Z Casilum, H Castilla-Valdez, D Chakraborty, SM Chang, SV Chekulaev, LP Chen, W Chen, S Choi, S Chopra, BC Choudhary, JH Christenson, M Chung, D Claes, AR Clark, WG Cobau, J Cochran, WE Cooper, C Cretsinger, D Cullen-Vidal, MAC Cummings, D Cutts, OI Dahl, K Davis, K De, K Del Signore, M Demarteau, D Denisov, SP Denisov, HT Diehl, M Diesburg, G Di Loreto, P Draper, Y Ducros, LV Dudko, SR Dugad, D Edmunds, J Ellison, VD Elvira, R Engelmann, S Eno, G Eppley, P Ermolov, OV Eroshin, VN Evdokimov, T Fahland, M Fatyga, MK Fatyga, J Featherly, S Feher, D Fein, T Ferbel, G Finocchiaro, HE Fisk, Y Fisyak, E Flattum

Abstract:

We have searched for the pair production of first generation scalar leptoquarks in the eejj channel using the full data set (123pb−1) collected with the D0 detector at the Fermilab Tevatron during 1992-1996. We observe no candidates with an expected background of approximately 0.4 events. Comparing the experimental 95% confidence level upper limit to theoretical calculations of the cross section with the assumption of a 100% branching fraction of eq, we set a lower limit on the mass of a first generation scalar leptoquark of 225 GeV/c2. The results of this analysis rule out the interpretation of the excess of high Q2 events at DESY HERA as leptoquarks which decay exclusively to eq. © 1997 The American Physical Society.
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