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Measurement of multiplicity and momentum spectra in the current and target regions of the Breit frame in deep inelastic scattering at HERA

European Physical Journal C 11:2 (1999) 251-270

Authors:

J Breitweg, S Chekanov, M Derrick, D Krakauer, S Magill, B Musgrave, J Repond, R Stanek, R Yoshida, MCK Mattingly, G Abbiendi, F Anselmo, P Antonioli, G Bari, M Basile, L Bellagamba, D Boscherini, A Bruni, G Bruni, G Cara Romeo, G Castellini, L Cifarelli, F Cindolo, A Contin, N Coppola, M Corradi, S de Pasquale, P Giusti, G Iacobucci, G Laurenti, G Levi, A Margotti, T Massam, R Nania, F Palmonari, A Pesci, A Polini, G Sartorelli, Y Zamora Garcia, A Zichichi, C Amelung, A Bornheim, I Brock, K Coböken, J Crittenden, R Deffner, M Eckert, H Hartmann, K Heinloth, L Heinz, E Hilger, HP Jakob, A Kappes, UF Katz, R Kerger, E Paul, M Pfeiffer, J Rautenberg, H Schnurbusch, A Stifutkin, J Tandler, A Weber, H Wieber, DS Bailey, O Barret, WN Cottingham, B Foster, GP Heath, HF Heath, JD McFall, D Piccioni, J Scott, RJ Tapper, M Capua, A Mastroberardino, M Schioppa, G Susinno, HY Jeoung, JY Kim, JH Lee, IT Lim, KJ Ma, MY Pac, A Caldwell, N Cartiglia, Z Jing, W Liu, B Mellado, JA Parsons, S Ritz, R Sacchi, S Sampson, F Sciulli, Q Zhu, P Borzemski, J Chwastowski, A Eskreys, J Figiel, K Klimek, K Olkiewicz

Abstract:

Charged particle production in neutral current deep inelastic scattering (DIS) has been studied using the ZEUS detector. The evolution of the mean multiplicities, scaled momenta and transverse momenta in Q2 and cursive Greek chi for 10 < Q2 < 5120 GeV2 and cursive Greek chi > 6 × 10-4 has been investigated in the current and target fragmentation regions of the Breit frame. Distributions in the target region, using HERA data for the first time, are compared to distributions in the current region. Predictions based on MLLA and LPHD are inconsistent with the data.
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Measurement of the diffractive cross section in deep inelastic scattering using ZEUS 1994 data

European Physical Journal C 6:1 (1999) 43-66

Authors:

J Breitweg, M Derrick, D Krakauer, S Magill, D Mikunas, B Musgrave, J Repond, R Stanek, RL Talaga, R Yoshida, H Zhang, MCK Mattingly, F Anselmo, P Antonioli, G Bari, M Basile, L Bellagamba, D Boscherini, A Bruni, G Bruni, G Cara Romeo, G Castellini, L Cifarelli, F Cindolo, A Contin, N Coppola, M Corradi, S de Pasquale, P Giusti, G Iacobucci, G Laurenti, G Levi, A Margotti, T Massam, R Nania, F Palmonari, A Pesci, A Polini, G Sartorelli, Y Zamora Garcia, A Zichichi, C Amelung, A Bornheim, I Brock, K Coböken, J Crittenden, R Deffner, M Eckert, M Grothe, H Hartmann, K Heinloth, L Heinz, E Hilger, HP Jakob, A Kappes, UF Katz, R Kerger, E Paul, M Pfeiffer, H Schnurbusch, H Wieber, DS Bailey, S Campbell-Robson, WN Cottingham, B Foster, R Hall-Wilton, GP Heath, HF Heath, JD McFall, D Piccioni, DG Roff, RJ Tapper, M Capua, L Iannotti, A Mastroberardino, M Schioppa, G Susinno, JY Kim, JH Lee, IT Lim, MY Pac, A Caldwell, N Cartiglia, Z Jing, W Liu, B Mellado, JA Parsons, S Ritz, S Sampson, F Sciulli, PB Straub, Q Zhu, P Borzemski, J Chwastowski, A Eskreys, J Figiel, K Klimek, MB Przybycień, L Zawiejski, L Adamczyk

Abstract:

The DIS diffractive cross section, dσdiffγ*p→XN/dMx, has been measured in the mass range Mx < 15 GeV for γ*p c.m. energies 60 < W < 200 GeV and photon virtualities Q2 = 7 to 140 GeV2. For fixed Q2 and Mx, the diffractive cross section rises rapidly with W, dσdiffγ*p→X N (Mx, W, Q2)/dMx ∝ Wadiff with adiff = 0.507 ± 0.034 (stat) +0.155-0.046 (syst) corresponding to a t-averaged pomeron trajectory of ̄αℙ = 1.127 ± 0.009 (stat) +0.039-0.012 (syst) which is larger than ̄αℙ observed in hadron-hadron scattering. The W dependence of the diffractive cross section is found to be the same as that of the total cross section for scattering of virtual photons on protons. The data are consistent with the assumption that the diffractive structure function FD(3)2 factorizes according to cursive greek chiℙFD(3)2(cursive greek chiℙ, β, Q2) = (cursive greek chi0//cursive greek chiℙ)nFD(2)2(β, Q2). They are also consistent with QCD based models which incorporate factorization breaking. The rise of cursive greek chiℙFD(3)2 with decreasing cursive greek chiℙ and the weak dependence of FD(2)2 on Q2 suggest a substantial contribution from partonic interactions.
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Measurement of the forward backward asymmetry of c and b quarks at the Z pole using reconstructed D mesons

European Physical Journal C 10:2 (1999) 219-237

Authors:

P Abreu, T Adye, P Adzic, Z Albrecht, T Alderweireld, GD Alekseev, R Alemany, T Allmendinger, PP Allport, S Almehed, U Amaldi, S Amato, EG Anassontzis, P Andersson, A Andreazza, S Andringa, P Antilogus, WD Apel, Y Arnoud, B Åsman, JE Augustin, A Augustinus, P Baillon, P Bambade, F Barao, G Barbiellini, R Barbier, DY Bardin, G Barker, A Baroncelli, M Battaglia, M Baubillier, KH Becks, M Begalli, P Beilliere, Y Belokopytov, K Belous, AC Benvenuti, C Berat, M Berggren, D Bertini, D Bertrand, M Besancon, F Bianchi, M Bigi, MS Bilenky, MA Bizouard, D Bloch, HM Blom, M Bonesini, W Bonivento, M Boonekamp, PSL Booth, AW Borgland, G Borisov, C Bosio, O Botner, E Boudinov, B Bouquet, C Bourdarios, TJV Bowcock, I Boyko, I Bozovic, M Bozzo, P Branchini, T Brenke, RA Brenner, P Bruckman, JM Brunet, L Bugge, T Buran, T Burgsmueller, P Buschmann, S Cabrera, M Caccia, M Calvi, T Camporesi, V Canale, F Carena, L Carroll, C Caso, MV Castillo Gimenez, A Cattai, FR Cavallo, V Chabaud, M Chapkin, P Charpentier, L Chaussard, P Checchia, GA Chelkov, R Chierici, P Chliapnikov, P Chochula, V Chorowicz, J Chudoba, K Cieslik, P Collins, R Contri, E Cortina, G Cosme

Abstract:

A measurement of the forward-backward asymmetry of e+e- → cc̄ and e+e- → bb̄ on the Z resonance is performed using about 3.5 million hadronic Z decays collected by the DELPHI detector at LEP in the years 1992 to 1995. The heavy quark is tagged by the exclusive reconstruction of several D meson decay modes. The forward-backward asymmetries for c and b quarks at the Z resonance are determined to be: AcFB(√s = 91.235GeV) = 0.0659 ± 0.0094 (stat) ± 0.0035 (syst) AbFB(√s = 91.235 GeV) = 0.0762 ± 0.0194 (stat) ± 0.0085 (syst) AcFB(√s = 89.434 GeV) = -0.0496 ± 0.0368 (stat) ± 0.0053 (syst) AbFB(√s = 89.434 GeV) = 0.0567 ± 0.0756 (stat) ± 0.0117 (syst) AcFB(√s = 92.990 GeV) = 0.1180 ± 0.0318 (stat) ± 0.0062 (syst) AbFB(√s = 92.990 GeV) = 0.0882 ± 0.0633 (stat) ± 0.0122 (syst) The combination of these results leads to an effective electroweak mixing angle of: sin2 θlepteff = 0.2332 ± 0.0016.
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Measurement of the lifetime of b-baryons

European Physical Journal C 10:2 (1999) 185-199

Authors:

P Abreu, W Adam, T Adye, P Adzic, Z Albrecht, T Alderweireld, GD Alekseev, R Alemany, T Allmendinger, PP Allport, S Almehed, U Amaldi, S Amato, EG Anassontzis, P Andersson, A Andreazza, S Andringa, P Antilogus, WD Apel, Y Arnoud, B Åsman, JE Augustin, A Augustinus, P Baillon, P Bambade, F Barao, G Barbiellini, R Barbier, DY Bardin, G Barker, A Baroncelli, M Battaglia, M Baubillier, KH Becks, M Begalli, P Beilliere, Y Belokopytov, K Belous, AC Benvenuti, C Berat, M Berggren, D Bertini, D Bertrand, M Besancon, F Bianchi, M Bigi, MS Bilenky, MA Bizouard, D Bloch, HM Blom, M Bonesini, W Bonivento, M Boonekamp, PSL Booth, AW Borgland, G Borisov, C Bosio, O Botner, E Boudinov, B Bouquet, C Bourdarios, TJV Bowcock, I Boyko, I Bozovic, M Bozzo, P Branchini, T Brenke, RA Brenner, P Bruckman, JM Brunet, L Bugge, T Buran, T Burgsmueller, P Buschmann, S Cabrera, M Caccia, M Calvi, T Camporesi, V Canale, F Carena, L Carroll, C Caso, MV Castillo Gimenez, A Cattai, FR Cavallo, V Chabaud, M Chapkin, P Charpentier, L Chaussard, P Checchia, GA Chelkov, R Chierici, P Chliapnikov, P Chochula, V Chorowicz, J Chudoba, K Cieslik, P Collins, R Contri, E Cortina

Abstract:

The average lifetime of weakly decaying b-baryons was studied using 3.6 million Z0 hadronic decays collected by the DELPHI detector at LEP. The measurement of the proper decay time distribution of secondary vertices was used on three complementary samples. The first sample consisted of events with a fully reconstructed Λ+c and an opposite charge lepton, or an oppositely charged lepton pair accompanied by a Λ0. The other two samples were more inclusive, where b-baryon semileptonic decays were recognized by the presence of either a proton identified by the RICH detector or a Λ0 and a lepton of charge opposite to that of the proton. The combined result was: τ(b-baryon) = 1.14 ± 0.08 (stat) ± 0.04 (syst) ps.
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Measurement of the mass of the W boson using direct reconstruction at √s = 183 GeV

Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics 462:3-4 (1999) 410-424

Authors:

P Abreu, T Adye, P Adzic, Z Albrecht, T Alderweireld, GD Alekseev, R Alemany, T Allmendinger, PP Allport, S Almehed, U Amaldi, N Amapane, S Amato, EG Anassontzis, P Andersson, A Andreazza, S Andringa, P Antilogus, WD Apel, Y Arnoud, B Åsman, JE Augustin, A Augustinus, P Baillon, P Bambade, F Barao, G Barbiellini, R Barbier, DY Bardin, G Barker, A Baroncelli, M Battaglia, M Baubillier, KH Becks, M Begalli, A Behrmann, P Beilliere, Y Belokopytov, K Belous, NC Benekos, AC Benvenuti, C Berat, M Berggren, D Bertini, D Bertrand, M Besancon, M Bigi, MS Bilenky, MA Bizouard, D Bloch, HM Blom, M Bonesini, W Bonivento, M Boonekamp, PSL Booth, AW Borgland, G Borisov, C Bosio, O Botner, E Boudinov, B Bouquet, C Bourdarios, TJV Bowcock, I Boyko, I Bozovic, M Bozzo, P Branchini, T Brenke, RA Brenner, P Bruckman, JM Brunet, L Bugge, T Buran, T Burgsmueller, B Buschbeck, P Buschmann, S Cabrera, M Caccia, M Calvi, T Camporesi, V Canale, F Carena, L Carroll, C Caso, MV Castillo Gimenez, A Cattai, FR Cavallo, V Chabaud, M Chapkin, P Charpentier, L Chaussard, P Checchia, GA Chelkov, R Chierici, P Chliapnikov, P Chochula, V Chorowicz, J Chudoba, K Cieslik, P Collins

Abstract:

From data corresponding to an integrated luminosity of 53.5 pb-1 taken during the 183 GeV run in 1997, DELPHI has measured the W mass from direct reconstruction of WW → ℓv̄qq̄ and WW → qq̄qq̄ events. Combining these channels, a value of mw = 80.238 ± 0.154(stat) ± 0.035(syst) ± 0.035(fsi) + 0.021(LEP)GeV/c2 is obtained, where fsi denotes final state interaction. Combined with the W mass obtained by DELPHI from the WW production cross-section and with the direct measurement at 172 GeV this leads to a measured value of mw = 80.270 ± 0.137(stat) ± 0.031(syst) ± 0.030(fsi) ± 0.021(LEP)GeV/c2, in good agreement with the Standard Model expectation. The width of the W boson is also measured, giving the value Γw= 2.48 ± 0.40(stat) ± 0.10(syst)GeV/c2. © 1999 Elsevier Science B.V. All rights reserved.
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