5890165
Measurement of the W boson mass with the Collider Detector at Fermilab
We present a measurement of the W boson mass using data collected with the CDF detector during the 1994-1995 collider run at the Fermilab Tevatron. A fit to the transverse mass spectrum of a sample of 30115 W --> ev events recorded in an integrated luminosity of 84 pb(-1) gives a mass M-W=80.473 +/-0.065(stat) +/-0.092(syst) GeV/c(2). A fit to the transverse mass spectrum of a sample of 14740 W --> muv events from 80 pb(-1) gives a mass M-W=80,465 +/-0.100(stat)+/-0.103(syst) Ge V/c(2) The dominant contributions to the systematic uncertainties are the uncertainties in the electron energy scale and the muon momentum scale, 0.075 GeV/c(2) and 0.085 GeV/c(2), respectively. The combined value for the electron and muon channel is M-W=80.470 +/-0.089-GeV/c(2). When combined with previously published CDF measurements, we obtain M-W=80.433 +/-0.079 GeV/c(2).
125998747
A Measurement of |V(cb)| using anti-B0 ---> D*+ lepton- anti-lepton-neutrino decays
48337486
A measurement of the average lifetime of b-flavoured baryons
Abstract The average lifetime of baryons containing a b quark has been measured with the OPAL detector using data collected between 1990 and 1992. Semileptonically decaying b-flavoured baryons which produce a Λ are identified through the charge correlation of the λ and lepton. The decay point of the baryon is estimated by the λ-lepton vertex, and the observed distribution of decay lengths is fitted to determine the average lifetime. In the data sample consisting of 261 right-sign and 104 wrong-sign λ-lepton charge combinations, the average b baryon lifetime is found to be τ = 1.05 +0.23 -0.20 ±0.08 ps, where the first error is statistical and the second systematic.
40056432
A study of four-fermion final states with high multiplicity at LEP
Abstract A search for l + l − q q (l = e, μ) four-fermion final states in high multiplicity events has been performed at s ≈m Z and above the Z peak at s =130 GeV and s =136 GeV. The data taken with OPAL correspond to an integrated luminosity of 132.4 pb−1 and 5.3 pb−1 at s ≈m Z and s =130−136 GeV, respectively. While at the Z resonance the data are in good agreement with the Standard Model predictions, we find more events than expected at s =130−136 GeV, especially in the μ + μ − q q channel, where 5 events remain after all cuts, with only 0.6 predicted by the Monte Carlo simulation. For all center-of-mass energies the observed shapes of the differential distributions are consistent with the predictions.
122711173
Search for neutral Higgs bosons in $Z^0$ decays using the OPAL detector at LEP
119808687
A search for doubly charged Higgs production in Z0 decays
Abstract A search for the decay of the Z 0 into doubly charged Higgs bosons (H ±± ) decaying to same-sign lepton pairs is presented using data collected with the OPAL detector at LEP, with an integrated luminosity of 6.8 pb − . Four-track final states from prompt decays, and events with at least one highly ionizing track from long-lived H ±± were sought. H ±± are excluded in the mass range from zero to 45.6 GeV/ c 2 and for a coupling constant range that extends down to zero.
7274949
A Chemical Abundance Study of One Red Giant Star in NGC 5694: A Globular Cluster with a Dwarf Spheroidal Chemical Signature?
We report an abundance analysis of one red giant branch star in the metal-poor outer halo globular cluster NGC 5694. We obtain [Fe/H] = -1.93 based on the ionized lines, and our metallicity measurement is in good agreement with previous estimates. We find that [Ca+Ti/2Fe] and [Cu/Fe] in NGC 5694 are about 0.3-0.4 dex lower than other globular clusters with similar metallicities, but similar to some LMC clusters and stars in some dwarf spheroidal galaxies. Differences persist, however, in the abundances of neutron-capture elements. The unique chemical abundance pattern and the large Galactocentric distance (30 kpc) and radial velocity (-138.6 ± 1.0 km s-1) indicate that NGC 5694 had an extragalactic origin.
15138730
Reconstructing the Higgs boson in dileptonic W decays at hadron colliders
We examine the prospect to measure the Higgs boson mass using the recently introduced kinematic variable, the ${M}_{T2}$-assisted on-shell (MAOS) momentum, that provides a systematic approximation to the invisible neutrino momenta in dileptonic decays of a $W$-boson pair. For this purpose, we introduce a modified version of the MAOS momentum that is applicable even when one or both of the $W$-bosons from the Higgs decay are in off shell. It is demonstrated that the MAOS Higgs mass distribution, constructed with the MAOS neutrino momenta, shows a clear peak at the true Higgs boson mass when an event cut selecting higher value of ${M}_{T2}$ is employed. We perform the likelihood analysis for this MAOS mass distribution to determine the Higgs boson mass, and find it can improve the accuracy of the Higgs mass measurement. Our results indicate that the MAOS Higgs mass can also be useful for the discovery or exclusion of the Higgs boson in certain mass range.
118544704
Measuring the Higgs boson mass with transverse mass variables
We provide a comparative study of the Higgs boson mass measurements based on two approaches to the dileptonic decay of W bosons produced by the Higgs boson decay, one using the kinematic variable M true T and the other using the M T2 -assisted on-shell reconstruction of the invisible neutrino momenta. We find that these two approaches can determine the Higgs boson mass with a similar accuracy for both of the two main production mechanisms of the SM Higgs boson at the LHC, i.e. the gluon-gluon fusion and the weak vector boson fusion. We also notice that the Higgs signal distribution for the gluon-gluon fusion becomes narrower under the M T2 cut, while the corresponding background distribution becomes flatter, indicating that one might be able to reduce the systematic uncertainties of mass measurement with an appropriate M T2 cut.
116621787
Polarization of prompt J/ in proton-proton collisions at RHIC
Within the framework of the nonrelativistic QCD (NRQCD) factorization approach, we compute the polarization of prompt J/{psi} produced at the Brookhaven's Relativistic Heavy-Ion Collider from proton-proton collisions at the center-of-momentum energy {radical}(s)=200 GeV. The perturbative contributions are computed at leading order in the strong coupling constant. The prediction reveals that the color-singlet contribution severely underestimates the PHENIX preliminary data for the differential cross section integrated over the rapidity range |y|<0.35 and its contribution is strongly transversely polarized, which disagrees with the PHENIX preliminary data. After including the color-octet contributions, we find that the NRQCD predictions for both the cross section and polarization over the transverse-momentum range 1.5 GeV<p{sub T}<5 GeV (1.5 GeV<p{sub T}<2 GeV) integrated over the rapidity range |y|<0.35 (1.2<|y|<2.2) agree with the data within errors.
119295378
Conformality Lost
Abstract We consider zero-temperature transitions from conformal to non-conformal phases in quantum theories. We argue that there are three generic mechanisms for the loss of conformality in any number of dimensions: (i) fixed point goes to zero coupling, (ii) fixed point runs off to infinite coupling, or (iii) an IR fixed point annihilates with a UV fixed point and they both disappear into the complex plane. We give both relativistic and non-relativistic examples of the last case in various dimensions and show that the critical behavior of the mass gap behaves similarly to the correlation length in the finite temperature Berezinskii-Kosterlitz-Thouless (BKT) phase transition in two dimensions, ξ ∼ exp(c/|T − Tc|). We speculate that the chiral phase transition in QCD at large number of fermion flavors belongs to this universality class, and attempt to identify the UV fixed point that annihilates with the Banks-Zaks fixed point at the lower end of the conformal window.