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Search for excited electrons using the ZEUS detector

Physics Letters B 316:1 (1993) 207-218

Authors:

M Derrick, D Krakauer, S Magill, B Musgrave, J Repond, S Repond, R Stanek, RL Talaga, J Thron, F Arzarello, R Ayad, G Bari, M Basile, L Bellagamba, D Boscherini, A Bruni, G Bruni, P Bruni, G Cara Romeo, G Castellini, M Chiarini, L Cifarelli, F Cindolo, F Ciralli, A Contin, S D'Auria, C Del Papa, F Frasconi, P Giusti, G Iacobucci, G Laurenti, G Levi, Q Lin, B Lisowski, G Maccarrone, A Margotti, T Massam, R Nania, C Memoz, F Palmonari, G Sartorelli, R Timellini, Y Zamora Garcia, A Zichichi, A Bargende, J Crittenden, H Dabbous, K Desch, B Diekmann, T Doeker, M Geerts, G Geitz, H Hartmann, D Haun, K Heinloth, E Hilger, HP Jakob, S Kramarczyk, M Kückes, A Mass, S Mengel, J Mollen, D Monaldi, H Müsch, E Paul, R Schattevoy, JL Schneider, D Schramm, R Wedemeyer, A Cassidy, DG Cussans, N Dyce, B Foster, R Gilmore, GP Heath, HF Heath, M Lancaster, TJ Llewellyn, J Malos, CJS Morgado, RJ Tapper, SS Wilson, R Yoshida, RR Rau, M Arneodo, T Barillari, M Schioppa, G Susinno, A Bernstein, A Caldwell, I Gialas, JA Parsons, S Ritz, F Sciulli, PB Straub, L Wai, S Yang, J Chwastowski, A Dwuraźny, A Eskreys

Abstract:

This paper reports a search for excited electrons at the HERA electron-proton collider. In a sample corresponding to an integrated luminosity of 26 nb-, no evidence was found for any resonant state decaying into e-γ, νW- or e-Z0. Limits on the coupling strength of an excited electron have been determined for masses between 45 and 225 GeV. This study also reports the observation of the wide-angle eγ Compton scattering process. © 1993.
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Observation of events with a large rapidity gap in deep inelastic scattering at HERA

Physics Letters B 315:3-4 (1993) 481-493

Authors:

M Derrick, D Krakauer, S Magill, B Musgrave, J Repond, S Repond, R Stanek, RL Talaga, J Thron, F Arzarello, R Ayad, G Bari, M Basile, L Bellagamba, D Boscherini, A Bruni, G Bruni, P Bruni, G Cara Romeo, G Castellini, M Chiarini, L Cifarelli, F Cindolo, F Ciralli, A Contin, S D'Auria, C Del Papa, F Frasconi, P Giusti, G Iacobucci, G Laurenti, G Levi, Q Lin, B Lisowski, G Maccarrone, A Margotti, T Massam, R Nania, C Nemoz, F Palmonari, G Sartorelli, R Timellini, Y Zamora Garcia, A Zichichi, A Bargende, J Crittenden, K Desch, B Diekmann, T Doeker, A Frey, M Geerts, G Geitz, H Hartmann, D Haun, K Heinloth, E Hilger, HP Jakob, S Kramarczyk, M Kückes, A Mass, S Mengel, J Mollen, D Monaldi, H Müsch, E Paul, R Schattevoy, JL Schneider, D Schramm, R Wedemeyer, A Cassidy, DG Cussans, N Dyce, B Foster, R Gilmore, GP Heath, HF Heath, M Lancaster, TJ Llewellyn, J Malos, CJS Morgado, RJ Tapper, SS Wilson, R Yoshida, RR Rau, M Arneodo, M Schioppa, G Susinno, A Bernstein, A Caldwell, I Gialas, JA Parsons, S Ritz, F Sciulli, PB Straub, L Wai, S Yang, P Borzemski, J Chwastowski, A Dwuraźny, A Eskreys

Abstract:

In deep inelastic, neutral current scattering of electrons and protons at s=296 GeV, we observe in the ZEUS detector events with a large rapidity gap in the hadronic final state. They occur in the region of small Bjorken x and are observed up to Q2 of 100 GeV2. They account for about 5% of the events with Q2≥10 GeV2. Their general properties are inconsistent with the dominant mechanism of deep inelastic scattering, where color is transferred between the scattered quark and the proton remnant, and suggest that the underlying production mechanism is the diffractive dissociation of the virtual photon. © 1993.
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Measurement of the triple-gluon vertex from 4-jet events at LEP

Zeitschrift für Physik C Particles and Fields 59:3 (1993) 357-368

Authors:

P Abreu, W Adam, T Adye, E Agasi, R Aleksan, GD Alekseev, A Algeri, P Allen, S Almehed, SJ Alsvaag, U Amaldi, A Andreazza, P Antilogus, WD Apel, RJ Apsimon, Y Arnoud, B Åsman, JE Augustin, A Augustinus, P Baillon, P Bambade, F Barao, R Barate, G Barbiellini, DY Bardin, GJ Barker, A Baroncelli, O Barring, JA Barrio, W Bartl, MJ Bates, M Battaglia, M Baubillier, KH Becks, CJ Beeston, M Begalli, P Beilliere, Y Belokopytov, P Beltran, D Benedic, AC Benvenuti, M Berggren, D Bertrand, F Bianchi, MS Bilenky, P Billoir, J Bjarne, D Bloch, S Blyth, V Bocci, PN Bogolubov, T Bolognese, M Bonesini, W Bonivento, PSL Booth, G Borisov, H Borner, C Bosio, B Bostiancic, S Bosworth, O Botner, B Bouquet, C Bourdarios, TJV Bowcock, M Bozzo, S Braibant, P Branchini, KD Brand, RA Brenner, H Briand, C Bricman, RCA Brown, N Brummer, JM Brunet, L Bugge, T Buran, H Burmeister, JAMA Buytaert, M Caccia, M Calvi, AJ Camacho Rozas, R Campion, T Camporesi, V Canale, F Cao, F Carena, L Carroll, C Caso, MV Castillo Gimenez, A Cattai, FR Cavallo, L Cerrito, V Chabaud, A Chan, M Chapkin, P Charpentier, L Chaussard, J Chauveau, P Checchia, GA Chelkov

Abstract:

From the combined data of 1990 and 1991 of the DELPHI experiment at LEP, 13057 4-jet events are obtained and used for determining the contribution of the triple-gluon vertex. The relevant variables are the generalized Nachtmann Reiter angle θNR* and the opening angle of the two least energetic jets. A fit to their two-dimensional distribution yields {Mathematical expression} where CA/CF is the ratio of the coupling strength of the triple-gluon vertex to that of gluon bremsstrahlung from quarks, and NC/NA, the ratio of the number of quark colours to the number of gluons. This constitutes a convincing model-independent proof of the existence of the triple-gluon vertex, since its contribution is directly proportional to CA/CF. The results are in agreement with the values expected from QCD:CA/CF=2.25, and NC/NA=3/8. © 1993 Springer-Verlag.
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Search for Z0 decays to two leptons and a charged particle-antiparticle pair

Nuclear Physics, Section B 403:1-2 (1993) 3-24

Authors:

P Abreu, W Adam, T Adye, E Agasi, R Aleksan, GD Alekseev, A Algeri, P Allen, S Almehed, SJ Alvsvaag, U Amaldi, A Andreazza, P Antilogus, WD Apel, RJ Apsimon, Y Arnoud, B Åsman, JE Augustin, A Augustinus, P Baillon, P Bambade, F Barao, R Barate, G Barbiellini, DY Bardin, GJ Barker, A Baroncelli, O Barring, JA Barrio, W Bartl, MJ Bates, M Battaglia, M Baubillier, KH Becks, CJ Beeston, M Begalli, P Beilliere, Y Belokopytov, P Beltran, D Benedic, AC Benvenuti, M Berggren, D Bertrand, F Bianchi, MS Bilenky, P Billoir, J Bjarne, D Bloch, S Blyth, V Bocci, PN Bogolubov, T Bolognese, M Bonesini, W Bonivento, PSL Booth, G Borisov, H Borner, C Bosio, B Bostjancic, S Bosworth, O Botner, E Boudinov, B Bouquet, C Bourdarios, TJV Bowcock, M Bozzo, S Braibant, P Branchini, KD Brand, RA Brenner, H Briand, C Bricman, RCA Brown, N Brummer, JM Brunet, L Bugge, T Buran, H Burmeister, JAMA Buytaert, M Caccia, M Calvi, AJ Camacho Rozas, R Campion, T Camporesi, V Canale, F Cao, F Carena, L Carroll, C Caso, MV Castillo Gimenez, A Cattai, FR Cavallo, L Cerrito, V Chabaud, A Chan, P Charpentier, L Chaussard, J Chauveau, P Checchia, GA Chelkov

Abstract:

Based on a sample equivalent to 365 000 hadronic Z0 decays, the search in DELPHI data for pairs of leptons accompanied by a pair of charged particles is described. A total of 11 events were found in the electron channel, 9 in the muon channel and 7 in the tau channel. Results on lepton pairs with a radiated photon are also presented. The data from all channels are compatible with the expectations from standard processes. However, one event was found in the tau channel with an unusually high mass of the charged particle pair. © 1993.
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A measurement of the mean lifetimes of charged and neutral B-hadrons

Physics Letters B 312:1-2 (1993) 253-266

Authors:

P Abreu, W Adam, T Adye, E Agasi, I Ajinenko, R Aleksan, GD Alekseev, A Algeri, P Allen, S Almehed, SJ Alvsvaag, U Amaldi, A Andreazza, P Antilogus, WD Apel, RJ Apsimon, Y Arnoud, B Åsman, JE Augustin, A Augustinus, P Baillon, P Bambade, F Barao, R Barate, G Barbiellini, DY Bardin, GJ Barker, A Baroncelli, O Barring, JA Barrio, W Bartl, MJ Bates, M Battaglia, M Baubillier, KH Becks, CJ Beeston, M Begalli, P Beilliere, Y Belokopytov, P Beltran, D Benedic, AC Benvenuti, M Berggren, D Bertrand, F Bianchi, MS Bilenky, P Billoir, J Bjarne, D Bloch, S Blyth, V Bocci, PN Bogolubov, T Bolognese, M Bonesini, W Bonivento, PSL Booth, G Borisov, H Borner, C Bosio, B Bostjancic, S Bosworth, O Botner, B Bouquet, C Bourdarios, TJV Bowcock, M Bozzo, S Braibant, P Branchini, KD Brand, RA Brenner, H Briand, C Bricman, RCA Brown, N Brummer, JM Brunet, L Bugge, T Buran, H Burmeister, JAMA Buytaert, M Caccia, M Calvi, AJC Rozas, R Campion, T Camporesi, V Canale, F Cao, F Carena, L Carroll, C Caso, MVC Gimenez, A Cattai, FR Cavallo, L Cerrito, V Chabaud, A Chan, P Charpentier, L Chaussard, J Chauveau, P Checchia, GA Chelkov

Abstract:

The decays of B-hadrons have been reconstructed using the charged particles recorded in the DELPHI silicon microstrip detector. The sum of the charges of the secondaries determines the charge of the B-hadron parent. Some 232 114 multihadronic Z0 decays recorded during the 1991 run of LEP at centre-of-mass energies between 88.2 GeV and 94.2 GeV yield 253 B-hadron candidates with well-measured charge. From these the mean lifetimes of neutral and charged B-hadrons are found to be 1.44±0.21 (stat.)±0.14(syst.) ps and 1.56±0.19(stat.)±0.13(syst.) ps respectively. The ratio of their lifetimes is 1.09-0.23+0.28 (stat.) ± 0.11(syst.). Under some assumptions on the abundance and lifetime of the Λb0 and Bs0 states, the B0 and B+ lifetimes are inferred. © 1993.
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