Accelerator Neutrinos

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Searches for scalar top and scalar bottom quarks in e+e- interactions at 161 GeV ≤ √s ≤ 183 GeV

Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics 445:3-4 (1999) 428-438

Authors:

M Acciarri, O Adriani, M Aguilar-Benitez, S Ahlen, J Alcaraz, G Alemanni, J Allaby, A Aloisio, MG Alviggi, G Ambrosi, H Anderhub, VP Andreev, T Angelescu, F Anselmo, A Arefiev, T Azemoon, T Aziz, P Bagnaia, L Baksay, S Banerjee, SW Banerjee, K Banicz, A Barczyk, R Barillère, L Barone, P Bartalini, A Baschirotto, M Basile, R Battiston, A Bay, F Becattini, U Becker, F Behner, J Berdugo, P Berges, B Bertucci, BL Betev, S Bhattacharya, M Biasini, A Biland, GM Bilei, JJ Blaising, SC Blyth, GJ Bobbink, R Bock, A Böhm, L Boldizsar, B Borgia, D Bourilkov, M Bourquin, S Braccini, JG Branson, V Brigljevic, IC Brock, A Buffini, A Buijs, JD Burger, WJ Burger, J Busenitz, A Button, XD Cai, M Campanelli, M Capell, G Cara Romeo, G Carlino, AM Cartacci, J Casaus, G Castellini, F Cavallari, N Cavallo, C Cecchi, M Cerrada, F Cesaroni, M Chamizo, YH Chang, UK Chaturvedi, M Chemarin, A Chen, G Chen, GM Chen, HF Chen, HS Chen, X Chereau, G Chiefari, CY Chien, L Cifarelli, F Cindolo, C Civinini, I Clare, R Clare, G Coignet, AP Colijn, N Colino, S Costantini, F Cotorobai, B de la Cruz, A Csilling, TS Dai, R D'Alessandro, R de Asmundis

Abstract:

Searches for scalar top and scalar bottom quarks have been performed at center-of-mass energies between 161 GeV and 183 GeV using the L3 detector at LEP. No signal is observed. Model-independent limits on production cross sections are determined for the two decay channels t̃1 → cχ̃01 and b̃1 → b χ̃01. Within the framework of the Minimal Supersymmetric extension of the Standard Model mass limits are derived. For mass differences between t̃1 and χ̃01 greater than 10 GeV a 95% C.L. limit of 81.5 GeV is set on the mass of the Supersymmetric partner of the left-handed top. A supersymmetric partner of the left-handed bottom with a mass below 80 GeV is excluded at 95% C.L. if the mass difference between b̃1 and χ̃1 is greater than 20 GeV. © 1999 Published by Elsevier Science B.V. All rights reserved.
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Dijet mass spectrum and a search for quark compositeness in (p)p collisions at sqrt(s) = 1.8 TeV

Physical Review Letters 82:12 (1999) 2457-2462

Authors:

B Abbott, M Abolins, V Abramov, BS Acharya, I Adam, DL Adams, M Adams, S Ahn, H Aihara, GA Alves, N Amos, EW Anderson, R Astur, MM Baarmand, VV Babintsev, L Babukhadia, A Baden, V Balamurali, B Baldin, S Banerjee, J Bantly, E Barberis, P Baringer, JF Bartlett, 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 Breedon, 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, L Coney, 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, A Dyshkant, D Edmunds, J Ellison, VD Elvira, R Engelmann, S Eno, G Eppley, P Ermolov, OV Eroshin, VN Evdokimov, T Fahland, MK Fatyga, S Feher, D Fein, T Ferbel, G Finocchiaro

Abstract:

Using the DZero detector at the 1.8 TeV pbarp Fermilab Tevatron collider, we have measured the inclusive dijet mass spectrum in the central pseudorapidity region |eta_jet| < 1.0 for dijet masses greater than 200 Gev/c^2. We have also measured the ratio of spectra sigma(|eta_jet| < 0.5)/sigma(0.5 < |eta_jet| < 1.0). The order alpha_s^3 QCD predictions are in good agreement with the data and we rule out models of quark compositeness with a contact interaction scale < 2.4 TeV at the 95% confidence level. © 1999 The American Physical Society.
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Direct search for light gluinos

Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics 446:2 (1999) 117-124

Authors:

V Fanti, A Lai, L Musa, D Marras, A Nappi, B Hay, RW Moore, KN Moore, DJ Munday, MD Needham, MA Parker, TO White, SA Wotton, J Andersen, G Barr, G Bocquet, J Bremer, A Ceccucci, D Cundy, N Doble, G Fischer, W Funk, L Gatignon, A Gianoli, A Gonidec, G Govi, P Grafström, W Kubischta, S Luitz, G Kesseler, JP Matheys, A Norton, S Palestini, B Panzer-Steindel, D Schinzel, H Taureg, M Velasco, O Vossnack, H Wahl, G Wirrer, V Kekelidze, A Mestvirishvili, I Potrebenikov, G Tatichvili, A Tkatchev, A Zinchenko, O Boyle, VJ Martin, IG Knowles, HLC Parsons, P Dalpiaz, J Duclos, PL Frabetti, M Martini, F Petrucci, M Porcu, M Savrie, A Bizzeti, M Calvetti, G Graziani, E Iacopini, M Lenti, A Michetti, HG Becker, H Blümer, P Buchholz, D Coward, C Ebersberger, H Fox, A Kalter, K Kleinknecht, U Koch, L Köpke, B Renk, J Scheidt, J Schmidt, V Schönharting, I Schue, R Wilhelm, A Winharting, M Wittgen, JC Chollet, S Crépé, L Iconomidou-Fayard, L Fayard, J Ocariz, G Unal, D Vattolo, I Wingerter, G Anzivino, P Cenci, P Lubrano, M Pepe, B Gorini, P Calafiura, R Carosi, C Cerri, M Cirilli, F Costantini, R Fantechi

Abstract:

We present the results for a direct search for light gluinos through the appearance of η→3π0 with high transverse momentum in the vacuum tank of the NA48 experiment at CERN. We find one event within a lifetime range of 10-9-10-3 s and another one between 10-10-10-9 s. Both events are consistent with the expected background from neutrons in the beam, produced by 450 GeV protons impinging on the Be targets, which interact with the residual air in the tank. From these data we give limits on the production of the hypothetical gg̃ bound state, the R0 hadron, and its R0→ηγ + ̃ decay in the R0 mass range between 1 and 5 GeV. © 1999 Elsevier Science B.V. All rights reserved.
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Evaluation of the LEP centre-of-mass energy above the W-pair production threshold

European Physical Journal C 11:4 (1999) 573-585

Authors:

A Blondel, M Bœge, E Bravin, P Bright-Thomas, T Camporesi, B Dehning, M Heemskerk, M Hildreth, M Koratzinos, E Lançon, G Mugnai, A Müller, E Peschardt, M Placidi, N Qi, G Quast, P Renton, F Sonnemann, E Torrence, A Weber, PS Wells, J Wenninger, G Wilkinson

Abstract:

Knowledge of the centre-of-mass energy at LEP2 is of primary importance to set the absolute energy scale for the measurement of the W-boson mass. The beam energy above 80 GeV is derived from continuous measurements of the magnetic bending field by 16 NMR probes situated in a number of the LEP dipoles. The relationship between the fields measured by the probes and the beam energy is calibrated against precise measurements of the average beam energy between 41 and 55GeV made using the resonant depolarisation technique. The linearity of the relationship is tested by comparing the fields measured by the probes with the total bending field measured by a flux loop. This test results in the largest contribution to the systematic uncertainty. Several further corrections are applied to derive the centre-of-mass energies at each interaction point. In addition, the centre-of-mass energy spread is evaluated. The beam energy has been determined with a precision of 25 MeV for the data taken in 1997, corresponding to a relative precision of 2.7 × 10-4. This is small in comparison to the present uncertainty on the W mass measurement at LEP. However, the ultimate statistical precision on the W mass with the full LEP2 data sample should be around 25 MeV, and a smaller uncertainty on the beam energy is desirable. Prospects for improvements are outlined.
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Evidence of color coherence effects in W + jets events from pp collisions at √s = 1.8 TeV

Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics 464:1-2 (1999) 145-155

Authors:

B Abbott, M Abolins, V Abramov, BS Acharya, I Adam, DL Adams, M Adams, S Ahn, V Akimov, GA Alves, N Amos, EW Anderson, MM Baarmand, VV Babintsev, L Babukhadia, A Baden, B Baldin, S Banerjee, J Bantly, E Barberis, P Baringer, JF Bartlett, A Belyaev, SB Beri, I Bertram, VA Bezzubov, PC Bhat, V Bhatnagar, M Bhattacharjee, G Blazey, S Blessing, P Bloom, A Boehnlein, NI Bojko, F Borcherding, C Boswell, A Brandt, R Breedon, G Briskin, R Brock, A Bross, D Buchholz, VS Burtovoi, JM Butler, W Carvalho, D Casey, Z Casilum, H Castilla-Valdez, D Chakraborty, KM Chan, SV Chekulaev, W Chen, DK Cho, S Choi, S Chopra, BC Choudhary, JH Christenson, M Chung, D Claes, AR Clark, WG Cobau, J Cochran, L Coney, WE Cooper, D Coppage, 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, A Dyshkant, D Edmunds, J Ellison, VD Elvira, R Engelmann, S Eno, G Eppley, P Ermolov, OV Eroshin, J Estrada, H Evans, VN Evdokimov, T Fahland, MK Fatyga, S Feher, D Fein, T Ferbel

Abstract:

We report the results of a study of color coherence effects in pp collisions based on data collected by the DØ detector during the 1994-1995 run of the Fermilab Tevatron Collider, at a center of mass energy √s = 1.8 TeV. Initial-to-final state color interference effects are observed by examining particle distribution patterns in events with a W boson and at least one jet. The data are compared to Monte Carlo simulations with different color coherence implementations and to an analytic modified-leading-logarithm perturbative calculation based on the local parton-hadron duality hypothesis. © 1999 Published by Elsevier Science B.V. All rights reserved.
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