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171.
Tau lepton decays with open strangeness in the final state are measured with the OPAL detector at LEP to determine the strange hadronic spectral function of the
lepton. The decays
,
and
with final states consisting of neutral and charged kaons and pions have been studied. The invariant mass distributions of
of these final states have been experimentally determined. Monte Carlo simulations have been used for the remaining
and for the strange final states including
mesons. The reconstructed strange final states, corrected for resolution effects and detection efficiencies, yield the strange spectral function of the
lepton. The moments of the spectral function and the ratio of strange to non-strange moments, which are important input parameters for theoretical analyses, are determined. Furthermore, the branching fractions
and
have been measured.Received: 18 February 2004, Revised: 30 April 2004, Published online: 15 June 2004 相似文献
172.
W. Wittek M. Aderholz P. Allport N. Armenise J. P. Baton M. Berggren F. W. Bullock M. Calicchio E. F. Clayton T. Coghen A. M. Cooper-Sarkar O. Erriquez P. Fitch N. Giannakopoulos J. Guy E. Hoffmann P. O. Hulth G. T. Jones P. Kasper U. F. Katz J. Kern H. Klein P. Marage E. Matsinos D. R. O. Morrison M. Neveu M. A. Parker N. Schmitz E. Simopoulou K. Varvell A. Vayaki W. Venus H. Wachsmuth BEBC WA Collaboration 《Zeitschrift fur Physik C Particles and Fields》1988,40(2):231-251
The average multiplicities of charged hadrons and of π+, π? and π0 mesons, produced in \(\bar v\) Ne and νNe charged current interactions in the forward and backward hemispheres of theW ±-nucleon center of mass system, are studied with data from BEBC. The dependence of the multiplicities on the hadronic mass (W) and on the laboratory rapidity (y Lab) and the energy fraction (z) of the pion is also investigated. Special care is taken to determine the π0 multiplicity accurately. The ratio of average π multiplicities \(\frac{{2\left\langle {n_{\pi ^O } } \right\rangle }}{{[\left\langle {n_{\pi ^ + } } \right\rangle + \left\langle {n_{\pi ^ - } } \right\rangle ]}}\) is consistent with 1. In the backward hemisphere \(\left\langle {n_{\pi ^O } } \right\rangle \) is positively correlated with the charged multiplicity. This correlation, as well as differences in multiplicities between \(\mathop v\limits^{( - )} \) and \(\mathop v\limits^{( - )} \) , \(\mathop v\limits^{( - )} \) scattering, is attributed to reinteractions inside the neon nucleus of the hadrons produced in the initial \(\mathop v\limits^{( - )} \) interaction. 相似文献
173.
Final results from the DELPHI Collaboration on the lifetime of B + and B0 mesons and the mean b-hadron lifetime, are presented using the data collected at the Z0 peak in 1994 and 1995. Elaborate, inclusive, secondary vertexing methods have been employed to ensure a b-hadron reconstruction with good efficiency. To separate samples of B + and B0 mesons, high performance neural network techniques are used that achieve very high purity signals. The results obtained are:
and for the average b-hadron lifetime:
Received: 6 October 2003, Revised: 12 December 2003, Published online: 25 February 2004 相似文献
174.
W. Geithner K.M. Hilligsoe S. Kappertz G. Katko M. Keim S. Kloos G. Kotrotsios P. Lievens K. Marinova R. Neugart L. Vermeeren S. Wilbert the ISOLDE Collaboration 《Hyperfine Interactions》2000,127(1-4):117-120
We report on fast beam collinear laser spectroscopy measurements that demonstrate the feasibility of accurate isotope shift
measurements for short lived Ne isotopes including the proton halo candidate 17Ne. Ultra high sensitivity is achieved by the application of an efficient resonance detection scheme based on collisional
ionization and ion counting via the β decay. A direct measurement of the kinetic energy of the atomic Ne beam provides the
required high accuracy.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
175.
176.
R. Bailhache A. Andronic P. Braun-Munzinger for the ALICE Collaboration 《Indian Journal of Physics》2010,84(12):1695-1700
The possibility to detect the Z0 in the ALICE central barrel is studied via the electronic decay channel Z0 → e
+
e
−. The signal and the background are simulated with the leading order event generator PYTHIA 6. The total cross-sections are
taken from NLO calculations. Based on test beam data, the electron identification performance of the Transition Radiation
Detector is extrapolated to high momenta. The expected yields for minimumbias pp collisions at 14TeV are presented. An isolation cut on the single electron, together with a minimum transverse momentum cut,
allows to obtain a clear signal. The expected background is of the order of 1% with the main contribution coming from misidentified
pions from jets. 相似文献
177.
Bona M Ciuchini M Franco E Lubicz V Martinelli G Parodi F Pierini M Roudeau P Schiavi C Silvestrini L Stocchi A Vagnoni V;UTfit Collaboration 《Physical review letters》2006,97(15):151803
The status of the unitary triangle beyond the standard model including the most recent results on Deltam[s] on dilepton asymmetries and on width differences is presented. Even allowing for general new physics loop contributions the unitarity triangle must be very close to the standard model result. With the new measurements from the Fermilab Tevatron, we obtain for the first time a significant constraint on new physics in the Bs sector. We present the allowed ranges of new physics contributions to DeltaF=2 processes and of the time-dependent CP asymmetry in Bs-->J/psivarphi decays. 相似文献
178.
We present the final results obtained by the MACRO experiment in the search for GUT magnetic monopoles and nuclearites. Several searches were performed with different subdetectors, i.e. scintillation counters, limited streamer tubes and nuclear track detectors. No magnetic monopole or nuclearite candidates were found. The MACRO upper limit to the local flux of GUT magnetic monopoles is at the level of 1.4×10−16 cm−2 s−1 sr−1. 相似文献
179.
The OPAL Collaboration G. Abbiendi et al. 《The European Physical Journal C - Particles and Fields》2002,23(1):1-11
A search for first generation scalar and vector leptoquarks (LQ) as well as for squarks () in R-parity violating SUSY models with the direct decay of the into Standard Model particles has been performed using ee collisions collected with the OPAL detector at LEP at an ee centre-of-mass energy of 189 GeV. The data correspond to an integrated luminosity of about 160 pb. The dominant process for this search is , where a photon, which has been radiated by one of the beam electrons, serves as a source of quarks. The numbers of selected
events found in the two decay channels are in agreement with the expectations from Standard Model processes. This result allows
to set lower limits at the 95% confidence level on the mass of first generation scalar and vector leptoquarks, and of squarks
in R-parity violating SUSY models. For Yukawa couplings to fermions larger than , the mass limits range from 121 GeV to GeV ( GeV to GeV) depending on the branching ratio of the scalar (vector) leptoquark state. Furthermore, limits are set on the Yukawa couplings for leptoquarks and for squarks, and on as a function of the scalar leptoquark/squark mass.
Received: 22 May 2001 / Published online: 25 January 2002 相似文献
180.
B. Bassalleck P. Braun-Munzinger W. Cleland G. David A. Farooq M. Fatyga A. Gavron V. Greene J. Hall R. Heifetz M. Herman H. Kent D. Kraus D. Lissauer W. Llope T. Ludlam Z. Moroz E. O'Brien L. Olsen D. Sarantites T. Semkow B. Shivakumar J. E. Simon J. Stachel H. Takai T. Throwe L. Waters J. Wojtkowska K. Wolf D. Wolfe E Collaboration 《Zeitschrift fur Physik C Particles and Fields》1988,38(1):45-49
Transverse energy distributions have been measured for collisions of 10 GeV/nucleon Si with targets of Al, Cu and Pb using a combination of a NaI wall and a uranium based sampling calorimeter. The measured cross sectionsdσ/dE T anddE T /dη are consistent with full stopping and an increase, with increasing values ofE T , of energy flow into large angles. 相似文献