229 research outputs found
Search for charginos in e+e- interactions at sqrt(s) = 189 GeV
An update of the searches for charginos and gravitinos is presented, based on
a data sample corresponding to the 158 pb^{-1} recorded by the DELPHI detector
in 1998, at a centre-of-mass energy of 189 GeV. No evidence for a signal was
found. The lower mass limits are 4-5 GeV/c^2 higher than those obtained at a
centre-of-mass energy of 183 GeV. The (\mu,M_2) MSSM domain excluded by
combining the chargino searches with neutralino searches at the Z resonance
implies a limit on the mass of the lightest neutralino which, for a heavy
sneutrino, is constrained to be above 31.0 GeV/c^2 for tan(beta) \geq 1.Comment: 22 pages, 8 figure
Hadronization properties of b quarks compared to light quarks in e+e- -> q qbar from 183 to 200 GeV
The DELPHI detector at LEP has collected 54 pb^{-1} of data at a
centre-of-mass energy around 183 GeV during 1997, 158 pb^{-1} around 189 GeV
during 1998, and 187 pb^{-1} between 192 and 200 GeV during 1999. These data
were used to measure the average charged particle multiplicity in e+e- -> b
bbar events, _{bb}, and the difference delta_{bl} between _{bb} and the
multiplicity, _{ll}, in generic light quark (u,d,s) events: delta_{bl}(183
GeV) = 4.55 +/- 1.31 (stat) +/- 0.73 (syst) delta_{bl}(189 GeV) = 4.43 +/- 0.85
(stat) +/- 0.61 (syst) delta_{bl}(200 GeV) = 3.39 +/- 0.89 (stat) +/- 1.01
(syst). This result is consistent with QCD predictions, while it is
inconsistent with calculations assuming that the multiplicity accompanying the
decay of a heavy quark is independent of the mass of the quark itself.Comment: 13 pages, 2 figure
Search for direct production of charginos and neutralinos in events with three leptons and missing transverse momentum in √s = 7 TeV pp collisions with the ATLAS detector
A search for the direct production of charginos and neutralinos in final states with three electrons or muons and missing transverse momentum is presented. The analysis is based on 4.7 fb−1 of proton–proton collision data delivered by the Large Hadron Collider and recorded with the ATLAS detector. Observations are consistent with Standard Model expectations in three signal regions that are either depleted or enriched in Z-boson decays. Upper limits at 95% confidence level are set in R-parity conserving phenomenological minimal supersymmetric models and in simplified models, significantly extending previous results
Jet size dependence of single jet suppression in lead-lead collisions at sqrt(s(NN)) = 2.76 TeV with the ATLAS detector at the LHC
Measurements of inclusive jet suppression in heavy ion collisions at the LHC
provide direct sensitivity to the physics of jet quenching. In a sample of
lead-lead collisions at sqrt(s) = 2.76 TeV corresponding to an integrated
luminosity of approximately 7 inverse microbarns, ATLAS has measured jets with
a calorimeter over the pseudorapidity interval |eta| < 2.1 and over the
transverse momentum range 38 < pT < 210 GeV. Jets were reconstructed using the
anti-kt algorithm with values for the distance parameter that determines the
nominal jet radius of R = 0.2, 0.3, 0.4 and 0.5. The centrality dependence of
the jet yield is characterized by the jet "central-to-peripheral ratio," Rcp.
Jet production is found to be suppressed by approximately a factor of two in
the 10% most central collisions relative to peripheral collisions. Rcp varies
smoothly with centrality as characterized by the number of participating
nucleons. The observed suppression is only weakly dependent on jet radius and
transverse momentum. These results provide the first direct measurement of
inclusive jet suppression in heavy ion collisions and complement previous
measurements of dijet transverse energy imbalance at the LHC.Comment: 15 pages plus author list (30 pages total), 8 figures, 2 tables,
submitted to Physics Letters B. All figures including auxiliary figures are
available at
http://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/HION-2011-02
Observation Of Very High Energy Cosmic-ray Families In Emulsion Chambers At High Mountain Altitudes (i)
Characteristics of cosmic-ray hadronic interactions in the 1015 - 1017 eV range are studied by observing a total of 429 cosmic-ray families of visible energy greater than 100 TeV found in emulsion chamber experiments at high mountain altitudes, Chacaltaya (5200 m above sea level) and the Pamirs (4300 m above sea level). Extensive comparisons were made with simulated families based on models so far proposed, concentrating on the relation between the observed family flux and the behaviour of high-energy showers in the families, hadronic and electromagnetic components. It is concluded that there must be global change in characteristics of hadronic interactions at around 1016 eV deviating from thise known in the accelerator energy range, specially in the forwardmost angular region of the collision. A detailed study of a new shower phenomenon of small-pT particle emissions, pT being of the order of 10 MeV/c, is carried out and its relation to the origin of huge "halo" phenomena associated with extremely high energy families is discussed as one of the possibilities. General characteristics of such super-families are surveyed. © 1992.3702365431Borisov, (1981) Nucl. Phys., 191 BBaybrina, (1984) Trudy FIAN 154, p. 1. , [in Russian], Nauka, MoscowLattes, Hadronic interactions of high energy cosmic-ray observed by emulsion chambers (1980) Physics Reports, 65, p. 151Hasegawa, ICR-Report-151-87-5 (1987) presented at FNAL CDF Seminar, , Inst. for Cosmic Ray Research, Univ. of TokyoCHACALTAYA Emulsion Chamber Experiment (1971) Progress of Theoretical Physics Supplement, 47, p. 1Yamashita, Ohsawa, Chinellato, (1984) Proc. 3rd Int. Symp. on Cosmic Rays and Particle Physics, p. 30. , Tokyo, 1984, Inst. for Cosmic Ray Research, Univ. of Tokyo(1984) Proc. 3rd Int. Symp. on Cosmic Rays and Particle Physics, p. 1. , Tokyo, 1984Baradzei, (1984) Proc. 3rd Int. Symp. on Cosmic Rays and Particle Physics, p. 136. , Tokyo, 1984Yamashita, (1985) J. Phys. Soc. Jpn., 54, p. 529Bolisov, (1984) Proc. 3rd Int. Symp. on Cosmic rays and Particle Physics, p. 248. , Tokyo, 1984, Inst. for Cosmic Ray Research, Univ. of TokyoTamada, Tomaszewski, (1988) Proc. 5th Int. Symp. on Very High Energy Cosmic-Ray Interactions, p. 324. , Lodz, 1988, Inst. for Cosmic Ray Research, Univ. of Tokyo, PolandHasegawa, (1989) ICR-Report-197-89-14, , Inst. for Cosmic Ray Research, Univ. of TokyoCHACALTAYA Emulsion Chamber Experiment (1971) Progress of Theoretical Physics Supplement, 47, p. 1Okamoto, Shibata, (1987) Nucl. Instrum. Methods, 257 A, p. 155Zhdanov, (1980) FIAN preprint no. 45, , Lebedev Physical Institute, MoscowSemba, Gross Features of Nuclear Interactions around 1015eV through Observation of Gamma Ray Families (1983) Progress of Theoretical Physics Supplement, 76, p. 111Nikolsky, (1975) Izv. Akad. Nauk. USSR Ser. Fis., 39, p. 1160Burner, Energy spectra of cosmic rays above 1 TeV per nucleon (1990) The Astrophysical Journal, 349, p. 25Takahashi, (1990) 6th Int. Symp. on Very High Energy Cosmic-ray Interactions, , Tarbes, FranceRen, (1988) Phys. Rev., 38 D, p. 1404Alner, The UA5 high energy simulation program (1987) Nuclear Physics B, 291 B, p. 445Bozzo, Measurement of the proton-antiproton total and elastic cross sections at the CERN SPS collider (1984) Physics Letters B, 147 B, p. 392Wrotniak, (1985) Proc. 19th Cosmic-Ray Conf. La Jolla, 1985, 6, p. 56. , NASA Conference Publication, Washington, D.CWrotniak, (1985) Proc. 19th Cosmic-Ray Conf. La Jolla, 1985, 6, p. 328. , NASA Conference Publication, Washington, D.CMukhamedshin, (1984) Trudy FIAN, 154, p. 142. , Nauka, Moscow, [in Russian]Dunaevsky, Pluta, Slavatinsky, (1988) Proc. 5th Int. Symp. on Very High Energy Cosmic-Ray Interactions, p. 143. , Lodz, 1988, Inst. of Physics, Univ. of Lodz, PolandKaidalov, Ter-Martirosyan, (1987) Proc. 20th Int. Cosmic-Ray Conf., Moscow, 1987, 5, p. 141. , Nauka, MoscowShabelsky, (1985) preprints LNPI-1113Shabelsky, (1986) preprints LNPI-1224, , Leningrad [in Russian]Hillas, (1979) Proc. 16th Int. Cosmic-Ray Conf., Kyoto, 6, p. 13. , Inst. for Cosmic Ray Research, Univ. of TokyoBorisov, (1987) Phys. Lett., 190 B, p. 226Hasegawa, Tamada, (1990) 6th Int. Symp. on Very High Energy Cosmic-Ray Interactions, , Tarbes, FranceSemba, Gross Features of Nuclear Interactions around 1015eV through Observation of Gamma Ray Families (1983) Progress of Theoretical Physics Supplement, p. 111Ren, (1988) Phys. Rev., 38 D, p. 1404Dynaevsky, Zimin, (1988) Proc. 5th Int. Symp. on Very High Energy Cosmic-Ray Interaction, p. 93. , Lodz, 1988, Inst. of Physics, Univ. of Lodz, PolandDynaevsky, (1990) Proc. 6th Int. Symp. on Very High Energy Cosmic-Ray Interactions, , Tarbes, France(1989) FIAN preprint no. 208, , Lebedev Physical Institute, Moscow(1990) Proc. 21st Int. Cosmic-Ray Conf., Adelaide, 8, p. 259. , Dept. Physics and Mathematical Physics, Univ. of Adelaide, AustraliaHasegawa, (1990) ICR-Report-216-90-9, , Inst. for Cosmic-Ray Research, Univ. of TokyoTamada, (1990) Proc. 21st Int. Cosmic-Ray Conf., Adelaide, 1990, 8. , Dept. Physics and Mathematical Physics, Univ. of Adelaide, AustraliaTamada, (1990) ICR-Report-216-90-9(1981) Proc. 17th Int. Cosmic-Ray Conf., Paris, 5, p. 291(1990) Proc. Int. Cosmic-Ray Conf., Adelaide, 1990, 8, p. 267. , Dept. Physics and Mathematical Physics, Univ. of Adelaide, Australia(1989) Inst. Nucl. Phys. 89-67/144, , preprint, Inst. Nucl. Phys., Moscow State UnivSmilnova, (1988) Proc. 5th Int. Sym. on Very High Energy Cosmic-Ray Interactions, p. 42. , Lodz, 1988, Inst. of Physics, Univ. of Lodz, PolandGoulianos, (1986) Proc. Workshop of Particle Simulation at High Energies, , University of Wisconsin, Madison, USAIvanenko, (1983) Proc. 18th Int. Cosmic-Ray Conf., Bangalore, 1983, 5, p. 274. , Tata Inst. Fundamental Research, Bombay, IndiaIvanenko, (1984) Proc. Int. Symp. on Cosmic-Rays and Particle Physics, p. 101. , Tokyo, 1984, Inst. for Cosmic Ray Research, Univ. of Tokyo(1988) 5th Int. Symp. on Very High Energy Cosmic-Ray Interactions, p. 180. , Lodz, 1988, Inst. of Physics, Univ. of Lodz, Poland(1990) Proc. 21st Int. Cosmic-Ray Conf., Adelaide, 1990, 8, p. 251. , Dept. Physics and Mathematical Physics, Univ. of Adelaide, Australia(1991) Izv. AN USSR No. 4, , to be publishedNikolsky, Shaulov, Cherdyntseva, (1990) FIAN preprint no. 140, , Lebedev Physical Institute, Moscow, [in Russian](1987) Proc. 20th Int. Cosmic-Ray Conf., Moscow, 1987, 5, p. 326. , Nauka, Mosco
Observation Of A High-energy Cosmic-ray Family Caused By A Centauro-type Nuclear Interaction In The Joint Emulsion Chamber Experiment At The Pamirs
An exotic cosmic-ray family event is observed in the large emulsion chamber exposed by the joint at the Pamirs (4360 m above sea level). The family is composed of 120γ-ray-induced showers and 37 hadron-induced showers with individual visible energy exceeding 1 TeV. The decisive feature of the event is the hadron dominance: ΣEγ, ΣE(γ) h, 〈Eγ, 〈E(γ) h〉, 〈Eγ·Rγ〉 and 〈E(γ)·Rh〉 being 298 TeV, 476 TeV, 2.5 TeV, 12.9 TeV, 28.6 GeV m and 173 GeV m, respectively. Most probably the event is due to a Centauro interaction, which occured in the atmosphere at ∼700 m above the chamber. The event will constitute the second beautiful candidate for a Centauro observed at the Pamirs. © 1987.1901-2226233Bayburina, (1981) Nucl. Phys. B, 191, p. 1Lattes, Fujimoto, Hasegawa, Hadronic interactions of high energy cosmic-ray observed by emulsion chambers (1980) Physics Reports, 65, p. 151(1984) Trudy FIAN, 154, p. 1Borisov, (1984) Proc. Intern. Symp. on Cosmic rays and particle physics, p. 3. , TokyoRen, (1985) 19th Intern. Cosmic ray Conf., 6, p. 317. , La JollaYamashita, (1985) 19th Intern. Cosmic ray Conf., 6, p. 364. , La JollaTamada, (1977) Nuovo Cimento, 41 B, p. 245T. Shibata et al., to be publishedHillas, (1979) 16th Intern. Cosmic ray Conf., 6, p. 13. , KyotoBattiston, Measurement of the proton-antiproton elastic and total cross section at a centre-of-mass energy of 540 GeV (1982) Physics Letters B, 117, p. 126UA5 Collab., G.J. Alner et al., preprint CERN-EP/85-62Taylor, (1976) Phys. Rev. D, 14, p. 1217Burnett, (1984) Proc. Intern. Symp. on Cosmic rays and particle physics, p. 468. , Toky
Updated precision measurement of the average lifetime of B hadrons
The measurement of the average lifetime of B hadrons using inclusively reconstructed secondary vertices has been updated using both an improved processing of previous data and additional statistics from new data. This has reduced the statistical and systematic uncertainties and gives \tau_{\mathrm{B}} = 1.582 \pm 0.011\ \mathrm{(stat.)} \pm 0.027\ \mathrm{(syst.)}\ \mathrm{ps.} Combining this result with the previous result based on charged particle impact parameter distributions yields \tau_{\mathrm{B}} = 1.575 \pm 0.010\ \mathrm{(stat.)} \pm 0.026\ \mathrm{(syst.)}\ \mathrm{ps.
Limits on the production of scalar leptoquarks from Z (0) decays at LEP
A search has been made for pairs and for single production of scalar leptoquarks of the first and second generations using a data sample of 392000 Z0 decays from the DELPHI detector at LEP 1. No signal was found and limits on the leptoquark mass, production cross section and branching ratio were set. A mass limit at 95% confidence level of 45.5 GeV/c2 was obtained for leptoquark pair production. The search for the production of a single leptoquark probed the mass region above this limit and its results exclude first and second generation leptoquarks D0 with masses below 65 GeV/c2 and 73 GeV/c2 respectively, at 95% confidence level, assuming that the D0lq Yukawa coupling alpha(lambda) is equal to the electromagnetic one. An upper limit is also given on the coupling alpha(lambda) as a function of the leptoquark mass m(D0)
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