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Production of Λ and ΛΛ correlations in the hadronic decays of the Z0

Physics Letters B 318:1 (1993) 249-262

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, 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, J Blocki, 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, L Brillault, RCA Brown, P Bruckman, JM Brunet, A Budziak, 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, MV Castillo Gimenez, A Cattai, FR Cavallo, L Cerrito, V Chabaud, A Chan, P Charpentier, L Chaussard, J Chauveau, P Checchia

Abstract:

An analysis of the production of the Λ baryon in the hadronic decays of the Z0 is presented, based on about 993K multihadronic events collected by the DELPHI detector at LEP during 1991 and 1992. The differencial cross section of the Λ and the correlations between Λ and Λ produced in the same event are compared to current models, based both on string fragmentation and on cluster decay. The predictions of the string fragmentation model are found to give satisfactory agreements with the data, clearly better than those of the cluster model. © 1993.
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Measurement of the proton structure function F2 in ep scattering at HERA

Physics Letters B 316:2-3 (1993) 412-426

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 Romero, 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, O Lin, B Losowski, G Maccarrone, A Margotti, T Massam, D Monaldi, R Nania, C Nemoz, F Palmonari, G Sartorelli, R Timellini, Y Zamora Garcia, A Zichini, 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 Jacob, S Kramaczyk, M Kückes, A Mass, S Mengel, J Mollen, H Müsch, E Paul, R Schattevoy, JL Schneider, D Schramm, R Wedemeyer, A Cassidy, DG Cussans, N Dyce, B Foster, S George, R Gilmore, GP Heath, HF Heath, M Lancaster, TJ Llwellyn, CJS Morgado, JA O'Mara, 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

Abstract:

This paper presents our first measurement of the F2 structure function in neutral-current, deep inelastic scattering using the ZEUS detector at HERA, the ep colliding beam facility at DESY. The data correspond to an integrated luminosity of 24.7 nb-1. Results are presented for data in range of Q2 from 10 GeV2 to 4700 GeV2 and Bjorken x down to 3.0 × 10-4. The F2 structure function increases rapidly as x decreases. © 1993.
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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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