Determination of sin2 θeff w using jet charge measurements in hadronic Z decays

The electroweak mixing angle is determined with high precision from measurements of the mean difference between forward and backward hemisphere charges in hadronic decays of the Z. A data sample of 2.5 million hadronic Z decays recorded over the period 1990 to 1994 in the ALEPH detector at LEP is used. The mean charge separation between event hemispheres containing the original quark and antiquark is measured for bb̄ and cc̄ events in subsamples selected by their long lifetimes or using fast D*'s. The corresponding average charge separation for light quarks is measured in an inclusive sample from the anticorrelation between charges of opposite hemispheres and agrees with predictions of hadronisation models with a precision of 2%. It is shown that differences between light quark charge separations and the measured average can be determined using hadronisation models, with systematic uncertainties constrained by measurements of inclusive production of kaons, protons and A's. The separations are used to measure the electroweak mixing angle precisely as sin2 θeff w = 0.2322 ± 0.0008(exp. stat.) ±0.0007(exp. syst.) ± 0.0008(sep.). The first two errors are due to purely experimental sources whereas the third stems from uncertainties in the quark charge separations

Measurement of the W mass by direct reconstruction in e+e−e^+ e^- collisions at 172 GeV

The mass of the W boson is obtained from reconstructed invariant mass distributions in W-pair events. The sample of W pairs is selected from 10.65~pb$^{-1}$ collected with the ALEPH detector at a mean centre-of-mass energy of 172.09 \GEV. The invariant mass distribution of simulated events are fitted to the experimental distributions and the following W masses are obtained: $WW \to q\overline{q}q\overline{q } m_W = 81.30 +- 0.47(stat.) +- 0.11(syst.) GeV/c^2$, $WW \to l\nu q\overline{q}(l=e,\mu) m_W = 80.54 +- 0.47(stat.) +- 0.11(syst.) GeV/c^2$, $WW \to \tau\nu q\overline{q} m_W = 79.56 +- 1.08(stat.) +- 0.23(syst.) GeV/C62$. The statistical errors are the expected errors for Monte Carlo samples of the same integrated luminosity as the data. The combination of these measurements gives: $m_W = 80.80 +- 0.11(syst.) +- 0.03(LEP energy) GeV/^2$

Study of muon-pair production at centre-of-mass energies from 20 to 136 GeV with the Aleph detector

The total cross section and the forward-backward asymmetry for the process $e^+ e^- \rightarrow \mu^+ \mu^- (n \gamma)$ are measured in the energy range 20-136 GeV by reconstructing the effective centre-of-mass energy after initial state radiation. The analysis is based on the data recorded with the ALEPH detector at LEP between 1990 and 1995, corresponding to a total integrated luminosity of 143.5 $\mathrm{pb}^{-1}$. Two different approaches are used: in the first one an exclusive selection of events with hard initial state radiation in the energy range 20-88 GeV is directly compared with the Standard Model predictions showing good agreement. In the second one, all events are used to obtain a precise measurement of the energy dependence of $\sigma^0$ and $A_{\mathrm{FB}}^0$ from a model independent fit, enabling constraints to be placed on models with extra Z bosons

Measurement of the axial-vector ? spectral functions and determination of ?s(M2?) from hadronic ? decays

An analysis based on 124 000 selected τ pairs recorded by the ALEPH detector at LEP provides the vector (V) and axial-vector (A) spectral functions of hadronic τ decays together with their total widths. This allows the evaluation of finite energy chiral sum rules that are weighted integrals over the (V−A) spectral functions. In addition, a precise measurement of αs along with a determination of nonperturbative contributions at the τ mass scale is performed. The experimentally and theoretically most robust determination of αs(M2τ) is obtained from the (V+A) fit that yields αs(M2τ)=0.334±0.022 giving αs(M2Z)=0.1202±0.0027 after the extrapolation to the mass of the Z boson. The approach of the Operator Product Expansion (OPE) is tested experimentally studying the evolution of the τ hadronic widths to masses smaller than the τ mass

Search for supersymmetry with a dominant R-parity violating L L anti-E coupling in e+ e- collisions at center-of-mass energies of 130-GeV to 172-GeV

A search for pair-production of supersymmetric particles under the assumption that R-parity is violated via a dominant LLE coupling has been performed using the data collected by ALEPH at centre-of-mass energies of 130-172 GeV. The observed candidate events in the data are in agreement with the Standard Model expectation. This is translated into lower limits on the mass of charginos, neutralinos, sleptons, sneutrinos and squarks. For instance, charginos with masses less than 73 GeV and neutralinos with masses less than 23 GeV are excluded at 95% confidence level for any generation structure of the LLE coupling, and for neutralino, slepton or sneutrino LSPs.Comment: 31 pages, 12 figures, 6 tables; submitted to Zeitschrift fuer Physik

K0(S) production in tau decays

From a sample of about 160k Z→τ+τ− candidates collected with the ALEPH detector at LEP between 1991 and 1995, τ lepton decays involving K0S→π+π− are studied. The K0SK0L associated production in τ decays is also investigated. The branching ratios are measured for the inclusive decay B(τ−→K0SX−ντ)=(9.70\pm0.58±0.62)×10−3 , where X− can be anything, and for the exclusive decays B(τ−→K¯¯¯0π−ντ)=(8.55±1.17±0.66)×10−3, B(τ−→K¯¯¯0π−π0ντ)=(2.94±0.73±0.37)×10−3, B(τ−→K¯¯¯0K−ντ)=(1.58±0.42±0.17)×10−3, B(τ−→K¯¯¯0K−π0ντ)=(1.52\pm0.76±0.21)×10−3. The decay τ−→K0SK0Lπ−ντ is studied for the first time, giving a branching ratio B(τ−→K0SK0Lπ−ντ)=(1.01±0.23±0.13)×10−3. The channels τ−→K0SK0Sπ−ντ , τ−→K0SK0Sπ−π0ντ , τ−→K0SK0Lπ−π0ντ , τ−→K¯¯¯0π−π0π0ντ , τ−→K0K−π0π0ντ and τ−→K0h+h−h−ντ are also investigated. In addition, mass spectra in the K0Sh− and K0Sh−π0 final states are analysed to provide information on the intermediate states produced in the decays

Study of B0(s) oscillations and lifetime using fully reconstructed D(s)- decays

A search for B0s oscillations is performed using approximately 4 million Z→qq¯ events collected by the ALEPH experiment during 1991–1995. B0s candidates are partially reconstructed by combining tracks with fully reconstructed D−s candidates. The B0s production flavour is estimated from the sign of the opposite hemisphere charge, a fragmentation kaon in the same hemisphere, or a lepton in the opposite hemisphere. From a total sample of 1620 candidates, with a B0s purity estimated to be 22%, all values of Δms below 3.9 ps −1 and between 6.5 and 8.8 ps −1 are excluded at 95% CL. From the same sample, the B0s lifetime is measured to be τs=1.47±0.14(stat)±0.08(syst) ps. This analysis selects mainly hadronic B0s decays and is statistically independent of a previous ALEPH analysis selecting B0s→D(∗)−sℓ+ν candidates. Combining these two analyses yields Δms>7.9 ps −1 at 95% CL and τs=1.51±0.11 ps

Three prong tau decays with charged kaons

Final states with charged kaons in three-prong τ decays are studied by exploiting the particle identification from the dE/dx measurement. The results are based on a sample of about 1.6 × 105 detected τ pairs collected with the ALEPH detector between 1991 and 1995 around the Z peak. The following branching ratios have been measured: B(τ- → K−K+π−ντ) = (1.63 ± 0.21 ± 0.17) × 10−3, B(τ− → K−π+π−ντ) = (2.14 ± 0.37 ± 0.29) × 10−3, B(τ− → K−K+π−π0ντ) = (0.75 ± 0.29 ± 0.15) × 10−3, and B(τ− → K−π+π−π0ντ) = (0.61 ± 0.39 ± 0.18) × 10−3. The first two measurements are more precise than the current world averages, while the last two channels are investigated for the first time. The 95% C.L. upper limit on the branching ratio for the decay τ− → K−K+K−ντ is 0.19 × 10−3. A study of intermediate states occurring in the K−K+π−ντ and K−π+π−ντ decays is also presented

Searches for charginos and neutralinos in e+ e- collisions at s**(1/2) = 161-GeV and 172-GeV

The data recorded by the ALEPH detector at centre-of-mass energies of 161, 170, and 172 GeV are analysed for signals of chargino and neutralino production. No evidence of a signal is found, although candidate events consistent with the expectations from Standard Model processes are observed. Limits at 95% C.L. on the production cross sections are derived and bounds on the parameters of the Minimal Supersymmetric Standard Model are set. The lower limit on the mass of the lightest chargino is 85.5 GeV/c^2 for gaugino-like charginos (mu = -500 GeV/c^2), and 85.0 GeV/c^2 for Higgsino-like charginos (M_2 = 500 GeV/c^2), for heavy sneutrinos (M(snu) > 200 GeV/c^2) and tanb = sqrt(2). The effect of light sleptons on chargino and neutralino limits is investigated. The assumptions of a universal slepton mass and a universal gaugino mass are relaxed, allowing less model-dependent limits to be obtained.Comment: 39 pages, 12 figures. Submitted to Zeit. f. Physi

Measurement of the D*± cross section in two photon collisions at LEP

complete author list: Buskulic D.; Casper D.; De Bonis I.; Decamp D.; Ghez P.; Goy C.; Lees J.; Minard M.; Odier P.; Pietrzyk B.; Ariztizabal F.; Chmeissani M.; Crespo J.; Efthymiopoulos I.; Fernandez E.; Fernandez-Bosman M.; Gaitan V.; Garrido L.; Martinez M.; Orteu S.; Pacheco A.; Padilla C.; Palla F.; Pascual A.; Perlas J.; Sanchez F.; Teubert F.; Creanza D.; de Palma M.; Farilla A.; Iaselli G.; Maggi G.; Marinelli N.; Natali S.; Nuzzo S.; Ranieri A.; Raso G.; Romano F.; Ruggieri F.; Selvaggi G.; Silvestris L.; Tempesta P.; Zito G.; Huang X.; Lin J.; Ouyang Q.; Wang T.; Xie Y.; Xu R.; Xue S.; Zhang J.; Zhang L.; Zhao W.; Bonvicini G.; Cattaneo M.; Comas P.; Coyle P.; Drevermann H.; Engelhardt A.; Forty R.; Frank M.; Girone M.; Hagelberg R.; Harvey J.; Jacobsen R.; Janot P.; Jost B.; Knobloch J.; Lehraus I.; Maggi M.; Markou C.; Martin E.; Mato P.; Meinhard H.; Minten A.; Miquel R.; Oest T.; Palazzi P.; Pater J.; Perrodo P.; Pusztaszeri J.; Ranjard F.; Rensing P.; Rolandi L.; Schlatter D.; Schmelling M.; Schneider O.; Tejessy W.; Tomalin I.; Venturi A.; Wachsmuth H.; Wiedenmann W.; Wildish T.; Witzeling W.; Wotschack J.; Ajaltouni Z.; Bardadin-Otwinowska M.; Barres A.; Boyer C.; Falvard A.; Gay P.; Guicheney C.; Henrard P.; Jousset J.; Michel B.; Monteil S.; Montret J.; Pallin D.; Perret P.; Podlyski F.; Proriol J.; Rossignol J.; Saadi F.; Fearnley T.; Hansen J.; Hansen J.; Hansen J.; Hansen P.; Nilsson B.; Kyriakis A.; Simopoulou E.; Siotis I.; Vayaki A.; Zachariadou K.; Blondel A.; Bonneaud G.; Brient J.; Bourdon P.; Passalacqua L.; Rougé A.; Rumpf M.; Tanaka R.; Valassi A.; Verderi M.; Videau H.; Candlin D.; Parsons M.; Focardi E.; Parrini G.; Corden M.; Delfino M.; Georgiopoulos C.; Jaffe D.; Antonelli A.; Bencivenni G.; Bologna G.; Bossi F.; Campana P.; Capon G.; Cerutti F.; Chiarella V.; Felici G.; Laurelli P.; Mannocchi G.; Murtas F.; Murtas G.; Pepe-Altarelli M.; Dorris S.; Halley A.; ten Have I.; Knowles I.; Lynch J.; Morton W.; O'Shea V.; Raine C.; Reeves P.; Scarr J.; Smith K.; Smith M.; Thompson A.; Thomson F.; Thorn S.; Turnbull R.; Becker U.; Braun O.; Geweniger C.; Graefe G.; Hanke P.; Hepp V.; Kluge E.; Putzer A.; Rensch B.; Schmidt M.; Sommer J.; Stenzel H.; Tittel K.; Werner S.; Wunsch M.; Beuselinck R.; Binnie D.; Cameron W.; Colling D.; Dornan P.; Konstantinidis N.; Moneta L.; Moutoussi A.; Nash J.; San Martin G.; Sedgbeer J.; Stacey A.; Dissertori G.; Girtler P.; Kneringer E.; Kuhn D.; Rudolph G.; Bowdery C.; Brodbeck T.; Colrain P.; Crawford G.; Finch A.; Foster F.; Hughes G.; Sloan T.; Whelan E.; Williams M.; Galla A.; Greene A.; Kleinknecht K.; Quast G.; Raab J.; Renk B.; Sander H.; Wanke R.; Zeitnitz C.; Aubert J.; Bencheikh A.; Benchouk C.; Bonissent A.; Bujosa G.; Calvet D.; Carr J.; Diaconu C.; Etienne F.; Thulasidas M.; Nicod D.; Payre P.; Rousseau D.; Talby M.; Abt I.; Assmann R.; Bauer C.; Blum W.; Brown D.; Dietl H.; Dydak F.; Gotzhein C.; Jakobs K.; Kroha H.; Lütjens G.; Lutz G.; Männer W.; Moser H.; Richter R.; Rosado-Schlosser A.; Settles R.; Seywerd H.; Stierlin U.; Denis R.; Wolf G.; Alemany R.; Boucrot J.; Callot O.; Cordier A.; Courault F.; Davier M.; Duflot L.; Grivaz J.; Heusse P.; Jacquet M.; Kim D.; Le Diberder F.; Lefrançois J.; Lutz A.; Musolino G.; Nikolic I.; Park H.; Park I.; Schune M.; Simion S.; Veillet J.; Videau I.; Abbaneo D.; Azzurri P.; Bagliesi G.; Batignani G.; Bettarini S.; Bozzi C.; Calderini G.; Carpinelli M.; Ciocci M.; Ciulli V.; Dell'Orso R.; Fantechi R.; Ferrante I.; Foà L.; Forti F.; Giassi A.; Giorgi M.; Gregorio A.; Ligabue F.; Lusiani A.; Marrocchesi P.; Messineo A.; Rizzo G.; Sanguinetti G.; Sciabà A.; Spagnolo P.; Steinberger J.; Tenchini R.; Tonelli G.; Triggiani G.; Vannini C.; Verdini P.; Walsh J.; Betteridge A.; Blair G.; Bryant L.; Gao Y.; Green M.; Johnson D.; Medcalf T.; Mir L.; Strong J.; Bertin V.; Botterill D.; Clifft R.; Edgecock T.; Haywood S.; Edwards M.; Maley P.; Norton P.; Thompson J.; Bloch-Devaux B.; Colas P.; Duarte H.; Emery S.; Kozanecki W.; Lançon E.; Lemaire M.; Locci E.; Marx B.; Perez P.; Rander J.; Renardy J.; Rosowsky A.; Roussarie A.; Schuller J.; Schwindling J.; Si Mohand D.; Trabelsi A.; Vallage B.; Johnson R.; Kim H.; Litke A.; McNeil M.; Taylor G.; Beddall A.; Booth C.; Boswell R.; Cartwright S.; Combley F.; Dawson I.; Koksal A.; Letho M.; Newton W.; Rankin C.; Thompson L.; Böhrer A.; Brandt S.; Cowan G.; Feigl E.; Grupen C.; Lutters G.; Minguet-Rodriguez J.; Rivera F.; Saraiva P.; Smolik L.; Stephan F.; Bosisio L.; Della Marina R.; Ganis G.; Giannini G.; Gobbo B.; Pitis L.; Ragusa F.; Rothberg J.; Wasserbaech S.; Armstrong S.; Bellantoni L.; Elmer P.; Feng Z.; Ferguson D.; Gao Y.; González S.; Grahl J.; Harton J.; Hayes O.; Hu H.; McNamara P.; Nachtman J.; Orejudos W.; Pan Y.; Saadi Y.; Schmitt M.; Scott I.; Sharma V.; Turk J.; Walsh A.; Weber F.; Wu S.; Wu X.; Yamartino J.; Zheng M.; Zobernig G.; Buskulic D.; Casper D.; Zobernig G.; Buskulic D.</p