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B* production in Z decays

Zeitschrift für Physik C Particles and Fields 68:3 (1995) 353-362

Authors:

P Abreu, W Adam, T Adye, E Agasi, I Ajinenko, R Aleksan, GD Alekseev, PP Allport, S Almehed, SJ Alvsvaag, U Amaldi, S Amato, A Andreazza, ML Andrieux, P Antilogus, WD Apel, Y Arnoud, B Åsman, JE Augustin, A Augustinus, P Baillon, P Bambade, F Barao, R Barate, DY Bardin, GJ Barker, A Baroncelli, O Barring, JA Barrio, W Bartl, MJ Bates, M Battaglia, M Baubillier, J Baudot, KH Becks, M Begalli, P Beilliere, Y Belokopytov, AC Benvenuti, M Berggren, D Bertrand, F Bianchi, M Bigi, MS Bilenky, P Billoir, D Bloch, M Blume, S Blyth, V Bocci, T Bolognese, M Bonesini, W Bonivento, PSL Booth, G Borisov, C Bosio, S Bosworth, O Botner, B Bouquet, C Bourdarios, TJV Bowcock, M Bozzo, P Branchini, KD Brand, RA Brenner, C Bricman, L Brillault, RCA Brown, P Bruckman, JM Brunet, L Bugge, T Buran, A Buys, M Caccia, M Calvi, AJC Rozas, T Camporesi, V Canale, M Canepa, K Cankocak, F Cao, F Carena, P Carrilho, L Carroll, C Caso, MVC Gimenez, A Cattai, FR Cavallo, L Cerrito, V Chabaud, P Charpentier, L Chaussard, J Chauveau, P Checchia, GA Chelkov, R Chierici, P Chliapnikov, P Chochula, V Chorowicz, V Cindro, P Collins

Abstract:

The decay B*→Bγ has been observed with the DELPHI detector at LEP, where the B* meson is produced in Z boson decays. The combination of inclusively reconstructed B mesons with well-measured converted photons yields a measurement of the flavour-averaged B*-B mass difference of 45.5±0.3 (stat.) ±0.8 (syst.) MeV/c2. 95% confidence level upper limits at 6 MeV/c2 are placed on both the isospin (i.e. B+-B0) and the Bs-Bud splitting of the mass difference. The production ratio of B* to B mesons in Z decays is measured to be 0.72±0.03 (stat.) ±0.06 (syst.). Limits on the production cross-section of other hypothetical excited B hadron states decaying radiatively are established. The differential B* cross section has been measured to be in good agreement with the average b fragmentation, yielding an average fractional B* energy of 〈xE〉=0.695±0.009 (stat.) ±0.013 (syst.). From the decay angular distribution the relative contribution of longitudinal B* polarisation states is measured to be σL/(σL + σT) = 0.32 ± 0.04 (stat.) ±0.03 (syst.). © 1995 Springer-Verlag.
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Lifetime and production rate of beauty baryons from Z decays

Zeitschrift Fur Physik C Particles and Fields 68:3 (1995) 375-390

Authors:

P Abreu, W Adam, T Adye, E Agasi, I Ajinenko, R Aleksan, GD Alekseev, PP Allport, S Almehed, SJ Alvsvaag, U Amaldi, S Amato, A Andreazza, ML Andrieux, P Antilogus, WD Apel, 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, J Baudot, KH Becks, M Begalli, P Beilliere, Y Belokopytov, AC Benvenuti, M Berggren, D Bertrand, F Bianchi, M Bigi, MS Bilenky, P Billoir, D Bloch, M Blume, S Blyth, V Bocci, T Bolognese, M Bonesini, W Bonivento, PSL Booth, G Borisov, C Bosio, S Bosworth, O Botner, B Bouquet, C Bourdarios, TJV Bowcock, M Bozzo, P Branchini, KD Brand, RA Brenner, C Bricman, L Brillault, RCA Brown, P Bruckman, JM Brunet, L Bugge, T Buran, A Buys, M Caccia, M Calvi, AJ Camacho Rozas, T Camporesi, V Canale, M Canepa, K Cankocak, F Cao, F Carena, P Carrilho, L Carroll, C Caso, MV Castillo Gimenez, A Cattai, FR Cavallo, L Cerrito, V Chabaud, M Chapkin, P Charpentier, L Chaussard, J Chauveau, P Checchia, GA Chelkov, R Chierici, P Chliapnikov, P Chochula, V Chorowicz

Abstract:

The production and decay of beauty baryons (b-baryons) have been studied using 1.7×106 Z hadronic decays collected by the DELPHI detector at LEP. Three different techniques were used to identify the b-baryons. The first method used pairs of a Λ and a lepton to tag the b-baryon decay. The second method associated fully reconstructed ΛC baryons with leptons. The third analysis reconstructed the b-baryon decay points by forming secondary vertices from identified protons and muons of opposite sign. Using these methods the following production rates were measured:[Figure not available: see fulltext.] The average b-baryon lifetime was determined to be:[Figure not available: see fulltext.] © 1995 Springer-Verlag.
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Lifetime of charged and neutral B hadrons using event topology

Zeitschrift für Physik C Particles and Fields 68:3 (1995) 363-374

Authors:

W Adam, T Adye, E Agasi, I Ajinenko, R Aleksan, GD Alekseev, PP Allport, S Almehed, SJ Alvsvaag, U Amaldi, S Amato, A Andreazza, ML Andrieux, P Antilogus, V Anykeyev, WD Apel, Y Arnoud, B Åsman, JE Augustin, A Augustinus, P Baillon, P Bambade, F Barao, R Barate, DY Bardin, GJ Barker, A Baroncelli, O Barring, JA Barrio, W Bartl, MJ Bates, M Battaglia, M Baubillier, J Baudot, KH Becks, M Begalli, P Beilliere, Y Belokopytov, AC Benvenuti, M Berggren, D Bertrand, F Bianchi, M Bigi, MS Bilenky, P Billoir, D Bloch, M Blume, S Blyth, V Bocci, T Bolognese, M Bonesini, W Bonivento, PSL Booth, G Borisov, C Bosio, S Bosworth, O Botner, B Bouquet, C Bourdarios, TJV Bowcock, M Bozzo, P Branchini, KD Brand, RA Brenner, C Bricman, L Brillault, RCA Brown, P Bruckman, JM Brunet, L Bugge, T Buran, A Buys, M Caccia, M Calvi, AJ Camacho Rozas, T Camporesi, V Canale, M Canepa, K Cankocak, F Cao, F Carena, P Carrilho, L Carroll, C Caso, MV Castillo Gimenez, A Cattai, FR Cavallo, L Cerrito, V Chabaud, P Charpentier, L Chaussard, J Chauveau, P Checchia, GA Chelkov, R Chierici, P Chliapnikov, P Chochula, V Chorowicz, V Cindro, P Collins

Abstract:

The lifetimes of charged and neutral B hadrons have been measured using data collected by the DELPHI experiment at LEP between 1991 and 1993. B hadrons are tagged as jets with a secondary vertex and the charge of the B candidate is taken to be the sum of the charges of the particles in the secondary vertex. Approximately 1,434,000 multihadronic Z0 decays yielded 1817 B hadron candidates. The B purity was estimated to be around 99.1±0.3%, and 83% (70%) of the events measured as neutral (charged) came from neutral (charged) B's. The mean lifetimes of charged and neutral B hadrons were found to be 1.72±0.08 (stat.) ±0.06 (syst.) ps and 1.58±0.11 (stat.)±0.09 (syst.) ps respectively. The ratio of their lifertimes, τcharged/τneutral, was 1.09-0.10+0.11 (stat.)±0.08 (syst.). By making assumptions about the Bs0 and Λb0 states, the B+ and B0 meson lifetimes were determined to be τB+ = 1.72 ± 0.08 (stat.) ±0.06 (syst.) ps and τB+ = 1.63 ± 0.14 (stat.)±0.13 (syst.) ps and the ratio of their lifetimes was: τB+/τB0 = 1.06-0.11+0.13 ±0.10. The mean B lifetime was also deduced to be < τ > = 1.64 ±0.06 (stat.)±0.04 (syst.) ps. © 1995 Springer-Verlag.
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Measurement of the proton structure function F2 from the 1993 HERA data

Zeitschrift Fur Physik C Particles and Fields 65:3 (1995) 379-398

Authors:

M Derrick, D Krakauer, S Magill, B Musgrave, J Repond, J Schlereth, 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, F Frasconi, P Giusti, G Iacobucci, G Laurenti, G Levi, A Margotti, T Massam, R Nania, C Nemoz, F Palmonari, A Polini, G Sartorelli, R Timellini, Y Zamora Garcia, A Zichichi, A Bargende, J Crittenden, K Desch, B Diekmann, T Doeker, L Feld, A Frey, M Geerts, G Geitz, M Grothe, H Hartmann, D Haun, K Heinloth, E Hilger, HP Jakob, UF Katz, SM Mari, A Mass, S Mengel, J Mollen, E Paul, C Rembser, R Schattevoy, JL Schneider, D Schramm, J Stamm, R Wedemeyer, S Campbell-Robson, A Cassidy, N Dyce, B Foster, S George, R Gilmore, GP Heath, HF Heath, TJ Llewellyn, CJS Morgado, DJP Norman, JA O'Mara, RJ Tapper, SS Wilson, R Yoshida, RR Rau, M Arneodo, L Iannotti, 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 Eskreys

Abstract:

The ZEUS detector has been used to measure the proton structure function F2. During 1993 HERA collided 26.7 GeV electrons on 820 GeV protons. The data sample corresponds to an integrated luminosity of 0.54 pb-1, representing a twenty fold increase in statistics compared to that of 1992. Results are presented for 72<104 GeV2 and x values as low as 3×10-4. The rapid rise in F2 as x decreases observed previously is now studied in greater detail and persists for Q2 values up to 500 GeV2. © 1995 Springer-Verlag.
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Measurement of {Mathematical expression} using impact parameter measurements and lepton identification

Zeitschrift für Physik C Particles and Fields 66:3 (1995) 323-339

Authors:

P Abreu, W Adam, T Adye, E Agasi, I Ajinenko, R Aleksan, GD Alekseev, PP Allport, S Almehed, FML Almeida, SJ Alvsvaag, U Amaldi, S Amato, A Andreazza, ML Andrieux, P Antilogus, WD Apel, Y Arnoud, B Åsman, JE Augustin, A Augustinus, P Baillon, P Bambade, F Barao, R Barate, DY Bardin, GJ Barker, A Baroncelli, O Barring, JA Barrio, W Bartl, MJ Bates, M Battaglia, M Baubillier, J Baudot, KH Becks, M Begalli, P Beilliere, Y Belokopytov, P Beltran, AC Benvenuti, M Berggren, D Bertrand, F Bianchi, M Bigi, MS Bilenky, P Billoir, J Bjarne, D Bloch, M Blume, S Blyth, V Bocci, T Bolognese, M bonesini, W Bonivento, PSL Booth, G Borisov, C Bosio, B Bostjancic, S Bosworth, O Botner, E Boudinov, B Bouquet, C Bourdarios, TJV Bowcock, M Bozzo, P Branchini, KD Brand, RA Brenner, H Briand, C Bricman, L Brillault, RCA Brown, P Bruckman, JM Brunet, L Bugge, T Buran, A Buys, M Caccia, M Calvi, AJC Rozas, T Camporesi, V Canale, M Canepa, K Cankocak, F Cao, F Carena, P Carrilho, L Carroll, C Caso, V Cassio, MVC Gimenez, A Cattai, FR Cavallo, L Cerrito, V Chabaud, A Chan, P Charpentier, L Chaussard, J Chauveau

Abstract:

The partial decay width of the Z to {Mathematical expression} quark pairs has been measured by the DELPHI detector at LEP. b-hadrons, containing b-quarks, were tagged by leptons with high transverse momentum relative to the hadron or by tracks with large impact parameters to the primary vertex. The ratio of the numbers of events with a single such tag to those with two tags was used to estimate the efficiency of the method and to reduce the systematic uncertainty. Combining all methods, the value: {Mathematical expression} was found, where the third error corresponds to a±8% uncertainty on the {Mathematical expression} production width. A maximum likelihood in to the single and di-lepton distributions gave the branching fraction of the decays of b-quarks to leptons as: {Mathematical expression} © 1995 Springer-Verlag.
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