Showing papers by "Hal Evans published in 2002"
TL;DR: Observations of neutral-current nu interactions on deuterium in the Sudbury Neutrino Observatory are reported, providing strong evidence for solar nu(e) flavor transformation.
Abstract: Observations of neutral-current nu interactions on deuterium in the Sudbury Neutrino Observatory are reported. Using the neutral current (NC), elastic scattering, and charged current reactions and assuming the standard 8B shape, the nu(e) component of the 8B solar flux is phis(e) = 1.76(+0.05)(-0.05)(stat)(+0.09)(-0.09)(syst) x 10(6) cm(-2) s(-1) for a kinetic energy threshold of 5 MeV. The non-nu(e) component is phi(mu)(tau) = 3.41(+0.45)(-0.45)(stat)(+0.48)(-0.45)(syst) x 10(6) cm(-2) s(-1), 5.3sigma greater than zero, providing strong evidence for solar nu(e) flavor transformation. The total flux measured with the NC reaction is phi(NC) = 5.09(+0.44)(-0.43)(stat)(+0.46)(-0.43)(syst) x 10(6) cm(-2) s(-1), consistent with solar models.
2,732 citations
TL;DR: The Sudbury Neutrino Observatory (SNO) has measured day and night solar neutrino energy spectra and rates, and a global solar neutRino analysis in terms of matter-enhanced oscillations of two active flavors strongly favors the large mixing angle solution.
Abstract: The Sudbury Neutrino Observatory (SNO) has measured day and night solar neutrino energy spectra and rates. For charged current events, assuming an undistorted 8B spectrum, the night minus day rate is 14.0%+/-6.3%(+1.5%)(-1.4%) of the average rate. If the total flux of active neutrinos is additionally constrained to have no asymmetry, the nu(e) asymmetry is found to be 7.0%+/-4.9%(+1.3%)(-1.2%). A global solar neutrino analysis in terms of matter-enhanced oscillations of two active flavors strongly favors the large mixing angle solution.
865 citations
TL;DR: A search for charged Higgs bosons in decays of pair-produced top quarks in pp collisions at sqrt[s] = 1.8 TeV recorded by the D0 detector at the Fermilab Tevatron collider finds no evidence for signal.
Abstract: We present a search for charged Higgs bosons in decays of pair-produced top quarks in pp collisions at sqrt[s] = 1.8 TeV recorded by the D0 detector at the Fermilab Tevatron collider. With no evidence for signal, we exclude most regions of the ( M(H+/-),tan(beta)) parameter space where the decay t--> H(+)b has a branching fraction >0.36 and B(H+/--->tau(nu)(tau)) is large.
54 citations
TL;DR: The central inclusive jet cross section has been measured using a successive-combination algorithm for reconstruction of jets using 87.3 pb−1 of data collected with the DO detector at the Fermilab Tevatron Collider during 1994-1995.
30 citations
TL;DR: In this article, the W boson mass was measured using the DO detector and a data sample of 82 pb(-1) from the Fermilab Tevatron collider.
Abstract: We have measured the W boson mass using the DO detector and a data sample of 82 pb(-1) from the Fermilab Tevatron collider. This measurement uses W-->enu decays, where the electron is close to a boundary of a central electromagnetic calorimeter module. Such "edge" electrons have not been used in any previous DO analysis, and represent a 14% increase in the W boson sample size. For these electrons, new response and resolution parameters are determined, and revised backgrounds and underlying event energy flow measurements are made. When the current measurement is combined with previous DO W boson mass measurements, we obtain M-W=80.483+/-0.084 GeV. The 8% improvement from the previous DO measurement is primarily due to the improved determination of the response parameters for non-edge electrons using the sample of Z bosons with non-edge and edge electrons.
28 citations
TL;DR: In this paper, the D empty set detector was used to study events produced in (p) over barp collisions that contain large forward regions with very little energy deposition ("rapidity gaps") and concurrent jet production at center of mass energies of roots = 630 and 1800 GeV.
18 citations
TL;DR: In this paper, the transverse mass spectrum of the W boson Gamma(W) was determined from the W-->e+nu(e) decay channel and the decay width was found to be 2.23(-0.14)(+0.15)(stat)+/-0.10(syst) GeV, consistent with the expectation from the standard model.
Abstract: Based on 85 pb-1 data of p (p) over bar collisions at roots=1.8 TeV collected using the D empty set detector at Fermilab during the 1994-1995 run of the Tevatron, we present a direct measurement of the total decay width of the W boson Gamma(W). The width is determined from the transverse mass spectrum in the W-->e+nu(e) decay channel and found to be Gamma(W)=2.23(-0.14)(+0.15)(stat)+/-0.10(syst) GeV, consistent with the expectation from the standard model.
14 citations
TL;DR: In this article, the authors performed a search for scalar top quark pair production in the inclusive electron-muon-missing transverse energy final state, using a sample of p (p) over bar events corresponding to 108.3 pb (-1) of data collected with the D0 detector at Fermilab.
Abstract: We have performed a search for scalar top quark (stop) pair production in the inclusive electron-muon-missing transverse energy final state, using a sample of p (p) over bar events corresponding to 108.3 pb (-1) of data collected with the D0 detector at Fermilab. The search is done in the framework of the minimal supersymmetric standard model assuming that the sneutrino is the lightest supersymmetric particle. For the dominant decays of the lightest stop, (t) over tilde-->b (χ) over tilde (+)(1) and (t) over tilde-->bl (ν) over tilde , no evidence for signal is found. We derive cross-section limits as a function of stop ((t) over tilde), chargino ((χ) over tilde (+)(1)), and sneutrino ((ν) over tilde ) masses.
14 citations
TL;DR: The results of a search for leptoquark (LQ) pairs in (85.2+/-3.7) pb(-1) of pp* collider data collected by the D0 experiment at the Fermilab Tevatron were presented in this paper.
Abstract: We present the results of a search for leptoquark (LQ) pairs in (85.2+/-3.7) pb(-1) of pp* collider data collected by the D0 experiment at the Fermilab Tevatron. We observe no evidence for leptoquark production and set a limit on sigma(pp*-->LQLQ-->nunu+jets) as a function of the mass of the leptoquark (m(LQ)). Assuming the decay LQ-->nuq, we exclude scalar leptoquarks for m(LQ) < 98 GeV/c(2), and vector leptoquarks for m(LQ) < 200 GeV/c(2) and coupling which produces the minimum cross section, at a 95% confidence level.
12 citations
14 Nov 2002
TL;DR: The Sudbury Neutrino Observatory (SNO) is a 1,000 tonne heavy water Cerenkov-based neutrino detector situated 2,000 meters underground in INCO's Creighton Mine near Sudbury, Ontario, Canada.
Abstract: The Sudbury Neutrino Observatory (SNO) is a 1,000 tonne heavy water Cerenkov‐based neutrino detector situated 2,000 meters underground in INCO’s Creighton Mine near Sudbury, Ontario, Canada. For the neutrinos from 8B decay in the Sun SNO observes the Charged Current neutrino reaction sensitive only to electron neutrinos and others (Neutral Current and Elastic Scattering) sensitive to all active neutrino types and thereby can search for direct evidence of neutrino flavor change. Using these reactions and assuming the standard 8B shape, the ve component of the 8B solar flux is φe = 1.76−0.05+0.05(stat.)−0.09+0.09 (syst.) × 106 cm−2s−1 for a kinetic energy threshold of 5 MeV. The non‐ve component is φμτ = 3.41−0.45+0.45(stat.)−0.45+0.48 (syst.) × 106 cm−2s−1, 5.3σ greater than zero, providing strong evidence for solar ve flavor transformation. The total flux measured with the NC reaction is φNC = 5.09−0.43+0.44(stat.)−0.43+0.46 (syst.) × 106 cm−2s−1, consistent with solar models. For charged current events, ...
11 citations
TL;DR: In this article, a search for R-parity-violating decay of the neutralino chi_1^0, taken to be the Lightest Supersymmetric Particle, is presented.
Abstract: We present results of a search for R-parity-violating decay of the neutralino chi_1^0, taken to be the Lightest Supersymmetric Particle. It is assumed that this decay proceeds through one of the lepton-number violating couplings lambda-prime_2jk (j=1,2; k=1,2,3). This search is based on 77.5 pb-1 of data, collected by the D0 experiment at the Fermilab Tevatron in ppbar collisions at a center of mass energy of 1.8 TeV in 1992-1995.
TL;DR: The first search for supersymmetric particles via s-channel production and decay of smuons or muon sneutrinos at hadronic colliders was reported in this article.
Abstract: We report the first search for supersymmetric particles via s-channel production and decay of smuons or muon sneutrinos at hadronic colliders. The data for the two-muon and two-jets final states were collected by the D0 experiment and correspond to an integrated luminosity of 94+/-5 pb(-1). Assuming that R parity is violated via the single coupling lambda(211)('), the number of candidate events is in agreement with expectation from the standard model. Exclusion contours are given in the (m(0),m(1/2)) and (m((χ) over bar),m((ν) over bar)) planes for lambda(211)(')=0.09, 0.08, and 0.07.
TL;DR: In this article, a search for evidence of minimal supergravity (MSUGRA) in 92.7 pb(-1) of data collected with the D empty set detector at the Fermilab Tevatron p (p) over bar collider at roots=1.8 TeV was described.
Abstract: We describe a search for evidence of minimal supergravity (MSUGRA) in 92.7 pb(-1) of data collected with the D empty set detector at the Fermilab Tevatron p (p) over bar collider at roots=1.8 TeV. Events with a single electron, four or more jets, and large missing transverse energy were used in this search. The major backgrounds are from W+jets, misidentified multijet, t (t) over bar, and WW production. We observe no excess above the expected number of background events in our data. A new limit in terms of MSUGRA model parameters is obtained.
Posted Content•
TL;DR: In this article, the authors review the prospects for physics at the CDF and Dzero experiments and show results from the first data collected in Run II at the Fermilab Tevatron.
Abstract: With the start of Run II at the Fermilab Tevatron a host of new physics opportunities are opened. In this paper we will review the prospects for physics at the CDF and \Dzero experiments. Topics ranging from QCD, to electro-weak precision measurements, to top-quark physics, to searches for the Higgs boson and signals of physics beyond the Standard Model will be discussed. B-Physics at the Tevatron is covered in a separate contribution to these proceedings. We will outline how upgrades to the accelerator and the detectors make these studies possible with precisions higher than ever achieved previously and will show results from the first data collected in Run II. These results give us confidence in our ability to achieve ambitious physics goals, and point the way toward a bright future for the Tevatron.
01 Jan 2002
TL;DR: The Sudbury Neutrino Observatory (SNO) is a 1000-tonne heavy water Cherenkov detector as discussed by the authors, which allows simultaneous measurements of the νe flux from B decay in the Sun and the total flux of all active neutrino species through the charged-current and the neutralcurrent interactions on the deuterons.
Abstract: The Sudbury Neutrino Observatory (SNO) is a 1000-tonne heavy water Cherenkov detector. Its usage of D2O as target allows the simultaneous measurements of the νe flux from B decay in the Sun and the total flux of all active neutrino species through the charged-current and the neutralcurrent interactions on the deuterons. Assuming the standard B shape, the νe component of the B solar neutrino flux is measured to be φe= 1.76 −0.05(stat.) +0.09 −0.09 (syst.)× 10 cms for a kinetic energy threshold of 5 MeV. The non-νecomponent is found to be φμτ= 3.41 +0.45 −0.45(stat.) +0.48 −0.45 (syst.)× 10 cms. This 5.3σ difference provides strong evidence for νe flavor transformation in the solar neutrino sector. The total active neutrino flux is measured with the neutral-current reaction at a neutrino energy threshold of 2.2 MeV. This flux is determined to be φNC= 5.09 +0.44 −0.43(stat.) +0.46 −0.43 (syst.) × 10 cms, and is consistent with solar model predictions. Assuming an undistorted B spectrum, the night minus day rate is 14.0±6.3(stat.) −1.4(sys.)% of the average rate in the charged-current channel. If the total active neutrino flux is constrained to have no asymmetry, the night-day asymmetry in the νe flux is found to be 7.0±4.9(stat.) −1.2(sys.)%. A global analysis of all the available solar neutrino data in terms of matter-enhanced oscillations of two active flavors strongly favors the Large Mixing Angle (LMA) solution. TTH01 XXX SLAC Summer Institute (SSI2002), Stanford, CA, 5-16 August, 2002
01 Jan 2002
TL;DR: The Sudbury Neutrino Observatory (SNO) is a 1000-tonne heavy water Cherenkov detector as mentioned in this paper, which allows simultaneous measurements of the νe flux from B decay in the Sun and the total flux of all active neutrino species through the charged-current and the neutralcurrent interactions on the deuterons.
Abstract: The Sudbury Neutrino Observatory (SNO) is a 1000-tonne heavy water Cherenkov detector. Its usage of D2O as target allows the simultaneous measurements of the νe flux from B decay in the Sun and the total flux of all active neutrino species through the charged-current and the neutralcurrent interactions on the deuterons. Assuming the standard B shape, the νe component of the B solar neutrino flux is measured to be φe= 1.76 −0.05(stat.) +0.09 −0.09 (syst.)× 10 cms for a kinetic energy threshold of 5 MeV. The non-νecomponent is found to be φμτ= 3.41 +0.45 −0.45(stat.) +0.48 −0.45 (syst.)× 10 cms. This 5.3σ difference provides strong evidence for νe flavor transformation in the solar neutrino sector. The total active neutrino flux is measured with the neutral-current reaction at a neutrino energy threshold of 2.2 MeV. This flux is determined to be φNC= 5.09 +0.44 −0.43(stat.) +0.46 −0.43 (syst.) × 10 cms, and is consistent with solar model predictions. Assuming an undistorted B spectrum, the night minus day rate is 14.0±6.3(stat.) −1.4(sys.)% of the average rate in the charged-current channel. If the total active neutrino flux is constrained to have no asymmetry, the night-day asymmetry in the νe flux is found to be 7.0±4.9(stat.) −1.2(sys.)%. A global analysis of all the available solar neutrino data in terms of matter-enhanced oscillations of two active flavors strongly favors the Large Mixing Angle (LMA) solution. TTH01 XXX SLAC Summer Institute (SSI2002), Stanford, CA, 5-16 August, 2002
01 Nov 2002
TL;DR: In this article, the authors review the prospects for physics at the CDF and DO experiments and show results from the first data collected in Run II at the Fermilab Tevatron.
Abstract: With the start of Run II at the Fermilab Tevatron a host of new physics opportunities are opened. In this paper we will review the prospects for physics at the CDF and DO experiments. Topics ranging from QCD, to electro-weak precision measurements, to top-quark physics, to searches for the Higgs boson and signals of physics beyond the Standard Model will be discussed. B-Physics at the Tevatron is covered in a separate contribution to these proceedings. We will outline how upgrades to the accelerator and the detectors make these studies possible with precisions higher than ever achieved previously and will show results from the first data collected in Run II. These results give us confidence in our ability to achieve ambitious physics goals, and point the way toward a bright future for the Tevatron.