共查询到20条相似文献,搜索用时 15 毫秒
1.
A search for excited lepton production in e+e- collisions was performed using the data collected by the DELPHI detector at LEP at centre-of-mass energies ranging from 189 GeV
to 209 GeV, corresponding to an integrated luminosity of approximately 600 pb-1. No evidence for excited lepton production was found. In searches for pair-produced excited leptons, lower mass limits were
established in the range 94–103 GeV/c2, depending on the channel and model assumptions. In searches for singly-produced excited leptons, upper limits on the parameter
f/Λ were established as a function of the mass. 相似文献
2.
《Physics letters. [Part B]》2009,680(1):24-33
A search for supersymmetric partners of quarks is performed in the topology of multijet events accompanied by at least one tau lepton decaying hadronically and large missing transverse energy. Approximately 1 fb−1 of collision data from the Fermilab Tevatron Collider at a center of mass energy of 1.96 TeV recorded by the DØ detector is analyzed. Results are combined with the previously published DØ inclusive search for squarks and gluinos. No evidence of physics beyond the Standard Model is found and lower limits on the squark mass up to 410 GeV are derived in the framework of minimal supergravity with tanβ=15, A0=−2m0 and μ<0, in the region where decays to tau leptons dominate. Gaugino masses m1/2 are excluded up to 172 GeV. 相似文献
3.
Gerald Rosen 《International Journal of Theoretical Physics》1978,17(1):1-4
The electron mass valuem=9.093 × 10–28 g is shown to be obtainable from the QED self-energy formula amended to include gravitational selfenergy and restricted by the space-time equipartition lawm/n
0=4/3. Held together by gravity, the electron has a radiusr
e
=8Gm/9e
2
c=2.588 × 10–53 cm. An extension of the analysis yields the theoretical muon-electron mass ratio of 206.241 and predicts heavier charged leptons with mass values of 1.915 GeV, 15.67 GeV, and above. 相似文献
4.
Yu.B. Bushnin A.F. Dunaytzev S.V. Golovkin V.P. Kubarovsky L.G. Landsberg V.M. Leontyev T.I. Petrunina V.A. Senko A.M. Zaytzev 《Nuclear Physics B》1973,58(2):476-493
Negative results of a search for heavy quasistable charged leptons at the IHEP accelerator are reported. For the selection of heavy leptons a system of scintillation and gas ?erenkov counters was used. The upper limit estimations of the differential cross sections for heavy lepton production in pN collisions at Ep = 70 GeV are, for example, d2σ/dpω (p = 30 GeV/c, θ = 2 mrad, 1 ? Mλ ? 4.8 GeV) = 4.10?38 cm2/sr · GeV. The results of the present work, together with the data on muon pair production in nucleon-nucleon interactions, show that there are no heavy charged leptons with masses from 0.55 GeV (τλ > 7 · 10?10 sec) up to 4.5 GeV (τλ > 3 · 10?8 sec). 相似文献
5.
About ScienceDirect 《Physics letters. [Part B]》1990,240(3-4):213-600
We report on a measurement of the mass of the Z0 boson, its total width, and its partial decay widths into hadrons and leptons. On the basis of 25 801 hadronic decays and 1999 decays into electrons, muons or taus, selected over eleven energy points between 88.28 GeV and 95.04 GeV, we obtain from a combined fit to hadrons and leptons a mass of Mz=91.154±0.021 (exp)±0.030 (LEP) GeV, and a total width of Γz=2.536±0.045 GeV. The errors on Mz have been separated into the experimental error and the uncertainty due to the LEP beam energy. The measured leptonic partial widths are Γee=81.2±2.6 MeV, Γμμ=82.6± 5.8 MeV, and Γττ=85.7±7.1 MeV, consistent with lepton universality. From a fit assuming lepton universality we obtain Γℓ+ ℓ− = 81.9±2.0 MeV. The hadronic partial width is Γhad=1838±46 MeV. From the measured total and partial widths a model independent value for the invisible width is calculated to be Γinv=453±44 MeV. The errors quoted include both the statistical and the systematic uncertainties. 相似文献
6.
M. Steidl 《Nuclear Physics B - Proceedings Supplements》2001,100(1-3)
The neutrino experiment
sets the most stringent exclusion limits for
μ→
e oscillations. Analyzing the data set recorded from Feb.1997 up to March 2000 with the upgraded experimental configuration, the search of
e appearance via the p(
e, e+)n reaction yields no hints for neutrino oscillations. Applying a likelihood method to the measured event sample of 11 events (background expectation 12.3 events), we deduce an upper limit of sin2 (2Θ) < 1.3 · 10−3 for large Δm2 > 100 eV2 and Δm2 < 0.049 eV2 for sin2 (2Θ)=1. 相似文献
7.
M.L. Perl G.J. Feldman G.S. Abrams M.S. Alam A.M. Boyarski M. Breidenbach F. Bulos W. Chinowsky J. Dorfan C.E. Friedberg G. Goldhaber G. Hanson F.B. Heile J.A. Jaros J.A. Kadyk R.R. Larsen A.M. Litke D. Lüke J.E. Wiss 《Physics letters. [Part B]》1976,63(4):466-470
We present the properties of 105 events of the form e+ + e? → e+- + μ? + missing energy, in which no other charged particles or photons are detected. The simplesthypothesis compatible with all the data is that these events come from the production of a pair of heavy leptons, the mass of the lepton being in the range 1.6 to 2.0 GeV/c2 相似文献
8.
Franklin Potter 《International Journal of Theoretical Physics》1994,33(2):279-305
The robust character of the Standard Model is confirmed. Examination of its geometrical basis in three equivalent internal symmetry spaces-the unitary planeC
2, the quaternion spaceQ, and the real spaceR
4—as well as the real spaceR
3 uncovers mathematical properties that predict the physical properties of leptons and quarks. The finite rotational subgroups of the gauge groupSU(2)
L
×U(1)
Y
generate exactly three lepton families and four quark families and reveal how quarks and leptons are related. Among the physical properties explained are the mass ratios of the six leptons and eight quarks, the origin of the left-handed preference by the weak interaction, the geometrical source of color symmetry, and the zero neutrino masses. The (u, d) and (c, s) quark families team together to satisfy the triangle anomaly cancellation with the electron family, while the other families pair one-to-one for cancellation. The spontaneously broken symmetry is discrete and needs no Higgs mechanism. Predictions include all massless neutrinos, the top quark at 160 GeV/c
2, theb quark at 80 GeV/c
2, and thet quark at 2600 GeV/c
2. 相似文献
9.
TASSO Collaboration M. Althoff W. Braunschweig K. Gather F. J. Kirschfink K. Lübelsmeyer H. -U. Martyn G. Peise J. Rimkus P. Rosskamp H. G. Sander D. Schmitz H. Siebke W. Wallraff 《Physics letters. [Part B]》1983,130(6)
Exclusive production of proton-antiproton pairs by two photon scattering at CM energies between 2.0 GeV and 3.1 GeV has been measured with the TASSO detector at the e+e− storage ring PETRA. The angular distribution is flat within the accepted CM angular range |cos Θ*|0.7. The integrated cross section (|cos Θ*|0.6) drops from about 4 nb at 2 GeV to less than 0.5 nb above 3 GeV. For the two-photon production of the ηc(2984) and its subsequent decay into proton-antiproton the upper limit
(95% CL) is found. 相似文献
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10.
K. Hagiwara S. Komamiya D. Zeppenfeld 《Zeitschrift fur Physik C Particles and Fields》1985,29(1):115-122
General expressions for single and pair production cross sections of excited leptons (e *,µ*,v *) are presented. Specific results are shown for a realisticSU(2)×U(1) invariant model. Pair production ine + e ? annihilation can measure anomalous magnetic moments of excited leptons. Single production ofe * is dominated by thet-channel γ exchange contribution which makes its detection feasible up to masses just below thee + e ? c.m. energy. Due to this small |t| enhancement effect, contributions from elastic and resonance scattering inep production ofe * are substantial. Realistic estimates of the excited lepton production cross section at HERA are given 相似文献
11.
We investigate the phenomenological implication of the discrete symmetry S3 × P on flavor physics in SO(10) unified theory. We construct a minimal renormalizable model which reproduce all the masses and mixing angle of both quarks and leptons. As usually the SO(10) symmetry gives up to relations between the down sector and the charged lepton masses. The underlining discrete symmetry gives a contribution (from the charged lepton sector) to the PMNS mixing matrix which is bimaximal. This gives a strong correlation between the down quark and charged lepton masses, and the lepton mixing angles. We obtain that the small entries V
ub, V
cb, V
td, and V
ts in the CKM matrix are related to the small value of the ratio δ m2
solΔ m2
atm: they come from both the S3×P structure of our model and the small ratio of the other quark masses with respect to m
t. Wonderfully, with our model, we fit 17 experimental data %with only 13 free relevant combinations of vevs. 相似文献
12.
Measurements of e+e? → e+e? at 2.8 GeV are reported and interpreted in terms of limits for the mass and coupling of a possible scalar boson of the type introduced in recent renormalizable models of weak interactions. In particular, in the Georgi-Glashow scheme of leptons we find that the scalar boson mass must be larger than 10 GeV for an mW = 10 GeV (mW mass of the W-boson) and of 6.5 GeV for mW = 15 GeV. Alternatively its coupling is extremely weak. 相似文献
13.
M. Sajjad Athar S. Ahmad S. K. Singh 《The European Physical Journal A - Hadrons and Nuclei》2005,24(3):459-474
The charged current lepton production induced by neutrinos in 56Fe nuclei has been studied. The calculations have been done for the quasielastic as well as the inelastic reactions assuming Δ-dominance and take into account the effect of Pauli blocking, Fermi motion and the renormalization of weak transition strengths in the nuclear medium. The quasielastic production cross-sections for lepton production are found to be strongly reduced due to nuclear effects, while there is about 10% reduction in the inelastic cross-sections in the absence of the final-state interactions of the pions. The numerical results for the momentum and angular distributions of the leptons averaged over the various atmospheric-neutrino spectra at the Soudan and Gran Sasso sites have been presented. The effect of nuclear-model dependence and the atmospheric-flux dependence on the relative yield of μ to e has been studied and discussed. 相似文献
14.
Search for heavy charged particles and for particles with anomalous charge in e+e? collisions at LEP
R. Akers G. Alexander J. Allison K. Ametewee K. J. Anderson S. Arcelli S. Asai D. Axen G. Azuelos A. H. Ball et al. 《Zeitschrift fur Physik C Particles and Fields》1995,67(2):203-211
Using the OPAL data accumulated in 1991–1993 amounting to 74 pb–1 of integrated luminosity, corresponding to 1.64×106 selected multi-hadronic events, a search has been performed for charged particles with unusual mass or unusual charge. The mass was determined from a combination of momentum and ionization energy loss measurements. No isolation criteria were applied to the tracks examined, so that both isolated particles and particles produced in jets were valid candidates. For particles with chargeQ/e=–1, one candidate with a mass of approximately 4.2 GeV/c2 was found, which is compatible with the background rate expected according to a Monte Carlo simulation. The implications of this search for the mass limits of a conjectured stable or quasi-stable charged gluino composite
are discussed. Limits are also presented for the production of fractionally-charged particles withQ/e=±2/3 and ±4/3 as well as for particles withQ/e=±2. 相似文献
15.
16.
Hierarchy of interactions and mass relations in asymptotically free E6 model of unified interactions
The hierarchy of gauge interactions within the E6 model is proved, and the vector and spinor field masses are obtained. The mass spectrum of the charged W-bosons is found, and the mass scale is fixed so that the mass of the lightest of them is about 70 GeV. The lepton spectroscopy is studied and a new charged lepton, with mass of order 4–8 GeV is predicted. For the low-energy phenomenology, the model may be considered as a theory of 6 flavoured quarks and 4 charged leptons, each with its neutrino. Being 4-component the neutrinos are massive except for the νe (mνe = 0, exactly) and νμ (mνμ ≈ 0, approximately) particles. The problem of the “superfluous” particles which as a rule accompanies the asymptotic freedom in such theories is also briefly discussed. 相似文献
17.
The neutrino experiment KARMEN is situated at the beam stop neutrino source ISIS which provides νμ's, νe's and
from the π+−μ+-decay at rest. The oscillation channels νμ → νe and
are investigated with a 56 t liquid scintillation calorimeter. No evidence for oscillations could be found with KARMEN, resulting in 90% CL exclusion limits of sin2(2Θ) < 8.5 · 10−3 (
) and sin2(2Θ) < 4.0 · 10−2 (νμ → νe) for Δm2 > 100 eV2. In 1996, the
experiment has been upgraded by an additional veto counting system with a total coverage of 300 m2. The new system allows the identification of cosmic muons in the vicinity of the detector. Vetoing these muons suppresses energetic neutrons from deep inelastic scattering of muons as well as from μ-capture by a factor of 40. Up to 1996, these neutrons represented the main background for
oscillation search. The experimental sensitivity for
will be significantly enhanced towards sin2(2Θ) 1.0 · 10−3 after a further measuring period of 2–3 years. 相似文献
18.
《Physics letters. [Part B]》2009,680(1):34-43
We report the results of a search for associated production of charginos and neutralinos using a data set corresponding to an integrated luminosity of 2.3 fb−1 collected with the DØ experiment during Run II of the Tevatron proton–antiproton collider. Final states containing three charged leptons and missing transverse energy are probed for a signal from supersymmetry with four dedicated trilepton event selections. No evidence for a signal is observed, and we set limits on the product of production cross section and leptonic branching fraction. Within minimal supergravity, these limits translate into bounds on m0 and m1/2 that are well beyond existing limits. 相似文献
19.
《Physics letters. [Part B]》2002,530(1-4)
A search for the pseudoscalar meson ηb is performed in two-photon interactions at LEP 2 with an integrated luminosity of 699 pb−1 collected at e+e− centre-of-mass energies from 181 GeV to 209 GeV. One candidate event is found in the six-charged-particle final state and none in the four-charged-particle final state, in agreement with the total expected background of about one event. Upper limits of Γγγ(ηb)×BR(ηb→4 charged particles)<48 eV, Γγγ(ηb)×BR(ηb→6 charged particles)<132 eV are obtained at 95% confidence level, which correspond to upper limits of 9.0% and 25% on these branching ratios. 相似文献
20.
V. V. Ammosov S. V. Belikov A. P. Bugorsky S. N. Gurziev A. A. Ivanilov P. V. Ivanov V. I. Konyushko V. M. Korablev V. A. Korotkov A. I. Kurnosenko E. P. Kuznetsov V. V. Makeev A. I. Mukhin A. G. Myagkov A. Yu. Polyarush A. A. Sokolov Yu. M. Sviridov H. J. Grabosch H. H. Kaufmann R. Nahnhauer S. Nowak H. E. Roloff S. Schlenstedt SKAT-Collaboration 《Zeitschrift fur Physik C Particles and Fields》1988,40(4):487-491
In the SKAT neutrino bubble chamber experiment at the Serpukhov accelerator we observe 83 events with electrons and no further lepton in the final state. Comparing the ratio of electron to muon charged current events at energies 3<E v <30 GeV with that expected fromv e -beam background assuming lepton universality we find \(R = (N_{e^ - } /N_{\mu ^ - } )_{\exp } /(N_{e^ - } /N_{\mu ^ - } )_{calc} = 0.98 \pm 0.15\) . Furthermore we compare experimental observations and theoretical expectations for some differential distributions of the electron-neutrino charged current reaction. No significant deviation from lepton universality is found. Looking in the charged current reaction for oscillations of muon to electron type neutrinos we find no effect down to the 90% confidence limits Δm 2 =1.3 eV2 at sin22θ=1 and sin22θ=2.5·10?3 at Δm 2=60 eV2. 相似文献