1,722,567 research outputs found
Measurement of the b baryon lifetime and branching fractions in Z decays
No full textUsing approximately 4 million hadronic Z decays recorded with the aleph detector from 1991 through 1995, the lifetime of the b baryon is measured with three independent methods. From the impact parameter distribution of candidate leptons in 1063 events with ` \Gamma combinations, the average b baryon lifetime is measured to be 1:20 \Sigma 0:08 \Sigma 0:06 ps. From a sample of 193 fully reconstructed + c candidates correlated with a lepton and a sample of 46 ` + ` \Gamma combinations, the b lifetime is measured to be 1:21 \Sigma 0:11 ps. The product branching fractions to these final states are Br(b ! b ) \Delta Br( b ! ` \Gamma X) = 0:326 \Sigma 0:016 \Sigma 0:039 % for the first sample and Br(b ! b ) \Delta Br( b ! + c ` \Gamma X) = 0:86 \Sigma 0:07 \Sigma 0:14 % for the second and third samples combined. (Submitted to Zeitschrift fur Physik) See the following pages for the list of authors. The ALEPH Collaboration R. Barate, D. Buskulic, D. Decamp, P. Ghez, C. Go..
Final results of the searches for neutral Higgs bosons in e+ e- collisions at s**(1/2) up to 209-GeV
Get PDFThe final results of the ALEPH search for the Standard Model Higgs boson at LEP, with data collected in the year 2000 at centre-of-mass energies up to 209 GeV, are presented. The changes with respect to the preceding publication are described and a complete study of systematic effects is reported. The findings of this final analysis confirm the preliminary results published in November 2000 shortly after the closing down of the LEP collider: a significant excess of events is observed, consistent with the production of a 115 \Gcs Standard Model Higgs boson. The final results of the searches for the neutral Higgs bosons of the MSSM are also reported, in terms of limits on \mh, \mA and \tanb. Limits are also set on \mh in the case of invisible decays
Searches for Scalar Top and Scalar Bottom Quarks at LEP2
No full textSearches for scalar top and bottom quarks have been performed with data collected by the ALEPH detector at LEP. The data sample consists of 21.7 pb \Gamma1 taken at p s = 161, 170, and 172 GeV and 5.7 pb \Gamma1 taken at p s = 130 and 136 GeV. No evidence for scalar top quarks or scalar bottom quarks was found in the channels ~ t ! cØ, ~ t ! b`~, and ~ b ! bØ. For the channel ~ t ! cØ a limit of 67 GeV=c 2 has been set on the scalar top quark mass, independent of the mixing angle between the supersymmetric partners of the left and right-handed states of the top quark. This limit assumes a mass difference between the ~ t and the Ø of at least 10 GeV=c 2 . For the channel ~ t ! b`~ the mixingangle independent scalar top limit is 70 GeV=c 2 , assuming a mass difference between the ~ t and the ~ of at least 10 GeV=c 2 . For the channel ~ b ! bØ, a limit of 73 GeV=c 2 has been set on the mass of the supersymmetric partner of the left-handed state of the bottom quark. Thi..
The Aleph and the Labyrinth
No full textIn “The Aleph and the Labyrinth” I begin by chronicling Borges’ early readings of Joyce’s Ulysses, which were a prologue to his lifelongfascination with this novel. In particular, Borges saw in Ulysses yet anotherattempt to write the “total book”: an attempt doomed to failure, perhaps, but nevertheless heroic. In the light of Ulysses, Borges explored this ambition in “Pierre Menard, Author of Don Quixote”, “The Library of Babel”, “Funes, His Memory” and particularly “El Aleph”; and offered his faulty and fragmentary reading of Joyce’s text as a metaphor for our equally – and fatally – faulty and fragmentary knowledge of the universe
Ada & Carter
No full textShort story, winner of The Aleph Writing Prize, 2020. Published as a handmade limited edition of 30: 10 with red binding, 20 with black binding. Each edition features a screen printed french fold cover, hand-sewn binding & numbered bellyband with a quote from the text: “It could start here, in this way, with this list of items stored in their loft between 1987 and 1997.” 18pp. 210x148mm
Production of Orbitally Excited Charm Mesons in Semileptonic B Decays
No full textA sample of 3.6 million hadronic Z decays recorded between 1991 and 1995 with the ALEPH detector at LEP is used to investigate semileptonic decays of B mesons into final states involving orbitally excited charm mesons. Topological vertex criteria are used to search for decays involving narrow D states as well as wide D resonances and non-resonant D () ß final states. The sum of the branching ratios for these processes is measured to be Br(B ! Dß` \Gamma ) + Br(B ! D ß` \Gamma ) = (2:26 \Sigma 0:29(stat) \Sigma 0:33(syst))%; which accounts for a significant fraction of the deficit between inclusive measurements and the sum of exclusive semileptonic B decay modes. (Submitted to Zeitschrift fur Physik) The ALEPH Collaboration D. Buskulic, I. De Bonis, D. Decamp, P. Ghez, C. Goy, J.-P. Lees, A. Lucotte, M.-N. Minard, J.-Y. Nief, P. Odier, B. Pietrzyk Laboratoire de Physique des Particules (LAPP), IN 2 P 3 -CNRS, 74019 Annecy-le-Vieux Cedex, France M.P. Casado, M. Ch..
Measurements of the b Baryon Lifetime
No full textUsing about 1.5 million hadronic Z decays recorded with the aleph detector, the lifetime of the b baryons has been measured using two independent data samples. From a maximum likelihood fit to the impact parameter distribution of leptons in 519 ` \Gamma combinations containing a b baryon sample of 290 decays, the measured b baryon lifetime is ø b\Gammabaryon = 1:05 +0:12 \Gamma0:11 (stat) \Sigma 0:09(syst) ps. The lifetime of the 0 b baryon from a maximum likelihood fit to the proper time distribution of 58 + c ` \Gamma candidates containing a 0 b sample of 44 decays, is ø 0 b = 1:02 +0:23 \Gamma0:18 (stat) \Sigma 0:06(syst) ps. The ALEPH Collaboration D. Buskulic, D. Casper, I. De Bonis, D. Decamp, P. Ghez, C. Goy, J.-P. Lees, M.-N. Minard, P. Odier, B. Pietrzyk Laboratoire de Physique des Particules (LAPP), IN 2 P 3 -CNRS, 74019 Annecy-le-Vieux Cedex, France F. Ariztizabal, M. Chmeissani, J.M. Crespo, I. Efthymiopoulos, E. Fernandez, M. Fernandez-Bosman, V...
Improved search for oscillations
No full textAn improved search for oscillations is performed in the ALEPH
data sample collected during the first phase of LEP, and reprocessed in 1998.
Three analyses based on complementary event selections are presented.
First, decays of mesons into hadronic flavour eigenstates are fully reconstructed.
This selection yields a small sample of candidates with excellent decay length and momentum resolution
and high average purity.
Semileptonic decays with a reconstructed meson provide a second sample with larger
statistics, high average purity, but a poorer momentum and decay length resolution
due to the partial decay reconstruction.
Finally, semileptonic b-hadron decays are inclusively selected and yield the data sample with the highest
sensitivity to oscillations, as
the much higher statistics
compensate for the low average purity and poorer time resolution.
A lower limit is set at
at , significantly lower than the expected
limit of
- …
