239 Matching Results

Search Results

Advanced search parameters have been applied.

Absolute Decay Rate from K<sub>2</sub><sup>0</sup>→π<sup>+</sup> + π<sup>-</sup> + π<sup>0</sup> and the barDELTA I over→bar = 1/2 Rule

Description: In this letter the author describes a measurement of the absolute decay rate {Gamma}{sub 2}({+-}0) {approx_equal} {Gamma}(K{sub 2}{sup 0} {yields} {pi}{sup +}{pi}{sup -}{pi}{sup 0}). The result is based on 16 events of the type {pi}{sup -} p {yields} {Lambda}K{sup 0} followed by {Lambda} {yields} p{pi}{sup -} and K{sub 2}{sup 0} {yields} {pi}{sup +}{pi}{sup -}{pi}{sup 0}, and 2608 double-vec events {pi}{sup -} p {yields} {Lambda}K{sup 0} with {Lambda} {yields} p{pi}{sup -} and K{sub 1}{sup 0} {yields} {pi}{sup +}{pi}{sup -}.
Date: February 4, 1964
Creator: Stern, Donald; Binford, Thomas O.; Lind, V. Gordon; Anderson, Jared A.; Crawford, Jr, Frank S. & Golden, Robert L.
Partner: UNT Libraries Government Documents Department

Proposed Emulsion Experiment Search for Short Lived Particles at High Energies

Description: It is proposed to conduct an experiment at the National Accelerator Laboratory concerned with the search for new particles having lifetimes between 10{sup -17} and 10{sup -12} second. The experiment will be conducted with an emulsion chamber arranqement and will explore for particles with lifetimes too short to be observed directly with other instruments. Two sidelines of the experiment will be concerned with an improved measurement of the lifetime of the neutral pion and the search for gamma ray bundles arising from higher mass resonances which cannot decay by pion emission.
Date: April 19, 1972
Creator: Kotzer, Peter; Lord, J.J. & U., /Washinton
Partner: UNT Libraries Government Documents Department

QCD Calculations of Pion Electromagnetic and Transition Form Factors

Description: Summarizing both the perturbative and nonperturbative aspects of the Q{sup 2} dependence of the {gamma}{gamma}* {r_arrow} {pi}{sup 0} form factor and of the pion electromagnetic form factor are rather well understood in quantum chromodynamics. however, new experimental data at higher Q{sup 2} would be extremely helpful for detailed tests of the transition to the regime where the pQCD hard contribution plays the dominant role.
Date: April 1, 2001
Creator: Radyushkin, A.V.
Partner: UNT Libraries Government Documents Department

The decay pi{sup 0} {yields} gamma gamma to next to leading order in Chiral Perturbation Theory

Description: The pi{sup 0} {yields} gamma gamma decay width is analyzed within the combined framework of Chiral Perturbation Theory and the 1/N{sub c} expansion up to order(p{sup 6}) and order(p{sup 4} x 1/N{sub c}) in the decay amplitude. The eta' is explicitly included in the analysis. It is found that the decay width is enhanced by about 4% due to the isospin-breaking induced mixing of the pure U(3) states. This effect, which is of leading order in the low energy expansion, is shown to persist nearly unchanged at next to leading order. The chief prediction Gamma{sub pi}0{sub {yields}gamma gamma} = 8.10 eV is estimated to have an uncertainty of less than 1%. Observations on the eta and eta' can also be made, especially about their mixing, which is shown to be significantly affected by next to leading order corrections.
Date: May 1, 2002
Creator: Goity, J.L.; Bernstein, A.M.; Donoghue, J.F. & Holstein, B.R.
Partner: UNT Libraries Government Documents Department

Effects of relativistic dynamics in pp {r_arrow} pp{pi}{sup 0} near threshold

Description: The cross-section for threshold {pi}{sup 0} production in proton-proton collisions is evaluated in the framework of the covariant spectator description. The negative energy intermediate states are included non-perturbatively and seen to yield a considerably smaller contribution, when compared to perturbative treatments. A family of OBE-models with different off-shell scalar coupling is considered.
Date: February 1, 1997
Creator: J. Adam, Jr.; Stadler, Alfred; Pena, M.T. & Gross, Franz
Partner: UNT Libraries Government Documents Department

QCD sum rule calculation of {gamma}{gamma}{sup *} {r_arrow} {pi}{sup 0} transition form factor

Description: The authors develop a QCD sum rule analysis of the form factor F{sub {gamma}{sup *}{gamma}{sup *}{pi}{sup 0}}(q{sup 2},Q{sup 2}) in the region where virtuality of one of the spacelike photons is small q{sup 2} {much_lt} 1 GeV{sup 2} while another is large: Q{sup 2} {approx_gt} 1 GeV{sup 2}. They construct the operator product expansion suitable for this kinematic situation and obtain a QCD sum rule for F{sub {gamma}{sup *}{gamma}{sup *}{pi}{sup 0}}(0, Q{sup 2}). Their results confirm expectation that the momentum transfer dependence of F{sub {gamma}{sup *}{gamma}{sup *}{pi}{sup 0}}(0,Q{sup 2}) is close to interpolation between its Q{sup 2}=0 value fixed by the axial anomaly and Q{sup {minus}2} pQCD behavior for large Q{sup 2}. Their approach, in contrast to pQCD, does not require additional assumptions about the shape of the pion distribution amplitude {var_phi}{sub {pi}}(x). The absolute value of the 1/Q{sup 2} term obtained in this paper favors {var_phi}{sub {pi}}(x) close to the asymptotic form {var_phi}{sub {pi}}{sup as}(x) = 6f{sub {pi}}x(1{minus}x).
Date: November 1, 1995
Creator: A.V.Radyushkin & R.T.Ruskov
Partner: UNT Libraries Government Documents Department

Recent Results from KTeV

Description: Recent results are presented for (1) the charge asymmetry in semielectronic kaon decay; (2) the charge radius of the neutral kaon; (3) the decay K{sub L}{sup 0} {r_arrow} {pi}{sup 0}{pi}{sup 0}e{sup +}e{sup {minus}}; (4) constraints on {rho}{sub CKM} from kaon decays; (5) lepton flavor violation. A few words about future kaon physics work at Fermilab are included.
Date: August 2, 2001
Creator: al., Leo Bellantoni et
Partner: UNT Libraries Government Documents Department

Transverse momentum and Sudakov effects in exclusive QCD processes: {gamma}{sup *}{gamma}{pi}{sup 0} form factor

Description: The authors analyze effects due to transverse degrees of freedom in QCD calculations of the fundamental hard exclusive amplitude of {gamma}{sup *}{gamma}{r_arrow}{pi}{sup 0} transition. A detailed discussion is given of the relation between the modified factorization approach (MFA) of Sterman et al. and standard factorization (SFA). Working in Feynman gauge, they construct basic building blocks of MFA from the one-loop coefficient function of the SFA, demonstrating that Sudakov effects are distinctly different from higher-twist corrections. They show also that the handbag-type diagram, contrary to naive expectations, does not contain an infinite chain of (M{sup 2}/Q{sup 2}){sup n} corrections: they come only from diagrams with transverse gluons emitted from the hard propagator. A simpler picture emerges within the QCD sum rule approach: the sum over soft {anti q}G ... Gq Fock components is dual to {anti q}q states generated by the local axial current. They combine the results based on QCD sum rules with pQCD radiative correct ions and observe that the gap between their curves for the asymptotic and CZ distribution amplitudes is sufficiently large for an experimental discrimination between them.
Date: February 1, 1997
Creator: Musatov, I.
Partner: UNT Libraries Government Documents Department

Measurements of the Branching Fraction and Time-Dependent CP Asymmetries of B0 to J/Psi pi0 Decays

Description: We present measurements of the branching fraction and time-dependent CP asymmetries in B{sup 0} {yields} J/{psi}{pi}{sup 0} decays based on (231.8 {+-} 2.6) x 10{sup 6} {Upsilon}(4S) {yields} B{bar B} decays collected with the BABAR detector at the SLAC PEP-II asymmetric-energy B factory. We obtain a branching fraction {Beta}(B{sup 0} {yields} J/{psi}{pi}{sup 0}) = (1.94 {+-} 0.22 (stat) {+-} 0.17 (syst)) x 10{sup -5}. We also measure the CP asymmetry parameters C = -0.21 {+-} 0.26 (stat) {+-} 0.06 (syst) and S = -0.68 {+-} 0.30 (stat) {+-} 0.04 (syst).
Date: March 10, 2006
Creator: George, K
Partner: UNT Libraries Government Documents Department

A Search for Neutrino Induced Coherent NC($\pi^{0}$) Production in the MINOS Near Detector

Description: The production of single, highly forward {pi}{sup 0} mesons by NC coherent neutrino-nucleus interactions ({nu}{sub {mu}} + N {yields} {nu}{sub {mu}} + N + {pi}{sup 0}) is a process which probes fundamental aspects of the weak interaction. This reaction may also pose as a limiting background for long baseline searches for {nu}{sub {mu}} {yields} {nu}{sub e} oscillations if the neutrino mixing angle {theta}{sub 13} is very small. The high-statistics sample of neutrino interactions recorded by the MINOS Near Detector provides an opportunity to measure the cross section of this coherent reaction on a relatively large-A nucleus at an average E{sub {nu}} = 4.9 GeV. A major challenge for this measurement is the isolation of forward-going electromagnetic (EM) showers produced by the relatively rare coherent NC({pi}{sup 0}) process amidst an abundant rate of incoherently produced EM showers. The backgrounds arise from single {pi}{sup 0} dominated NC events and also from quasi-elastic-like CC scattering of electron neutrinos. In this Thesis the theory of coherent interactions is summarized, and previous measurements of the coherent NC({pi}{sup 0}) cross section are reviewed. Then, methods for selecting a sample of coherent NC({pi}{sup 0}) like events, extracting the coherent NC({pi}{sup 0}) event rate from that sample, estimating the analysis uncertainties, and calculating a cross section, are presented. A signal for neutrino-induced NC({pi}{sup 0}) production is observed in the relevant kinematic regime as an excess of events of three standard deviations above background. The reaction cross sections, averaged over an energy window of 2.5 {&lt;=} E{sub {nu}} {&lt;=} 9.0 GeV is determined to be (31.6{+-}10.5) x 10{sup -40} cm{sup 2}/nucleus. The result is the first evidence obtained for neutrino-nucleus coherent NC({pi}{sup 0}) scattering on iron, and is the first measurement on an average nuclear target above A = 30. The cross section measurement is in agreement with NEUGEN3 ...
Date: November 1, 2010
Creator: Cherdack, Daniel David & U., /Tufts
Partner: UNT Libraries Government Documents Department

Preliminary Measurement of B(tau- ---> K- pi0 nu/tau) Using the BaBar Detector

Description: A preliminary measurement of the branching fraction {Beta}({tau}{sup -} {yields} K{sup -}{pi}{sup 0}{nu}{sub {tau}}) is made using 124.4 fb{sup -1} of e{sup +}e{sup -} collision data provided by the PEP-II accelerator, operating primarily at {radical}s = 10.58 GeV, and recorded using the BABAR detector. They measure: {Beta}({tau}{sup -} {yields} K{sup -} {pi}{sup 0}{nu}{sub {tau}}) = (0.438 {+-} 0.004(stat) {+-} 0.022(syst))%. This result is the world's most precise measurement of this branching fraction to date and is consistent with the world average.
Date: July 8, 2005
Creator: Salvatore, F.; /Royal Holloway, U. of London; Lyon, A.J. & U., /Manchester
Partner: UNT Libraries Government Documents Department

Search for Second-Class Currents in tau- -> omega.pi-.nu_tau

Description: We report an analysis of {tau}{sup -} decaying into {omega}{pi}{sup -} {nu}{sub {tau}} with {omega} {yields} {pi}{sup +}{pi}{sup -}{pi}{sup 0} using a data sample containing nearly 320 million {tau} pairs collected with the BABAR detector at the PEP-II B-Factory. We find no evidence for second-class currents and we set an upper limit of 0.69% at 90% confidence level for the fraction of second-class currents in this decay mode.
Date: April 22, 2009
Creator: Aubert, B.
Partner: UNT Libraries Government Documents Department

Measurement of the Time-Dependent CP-Violating Asymmetry in $B^0 \to K^{0}_s\pi^0\gamma$ Decays

Description: We present a measurement of the time-dependent CP-violating asymmetry in B{sup 0} {yields} K*{sup 0}{gamma} decays with K*{sup 0} {yields} K{sub S}{sup 0}{pi}{sup 0} based on 232 million {Upsilon}(4S) {yields} B{bar B} decays collected with the BABAR detector at the PEP-II asymmetric-energy e{sup +}e{sup -} collider at SLAC. In a sample containing 157 {+-} 16 signal decays, we measure S{sub K*{sup 0}{gamma}} = -0.21 {+-} 0.40 {+-} 0.05 and C{sub K*{sup 0}{gamma}} = -0.40 {+-} 0.23 {+-} 0.03, where the first error is statistical and the second systematic. We also explore B{sup 0} {yields} K{sub S}{sup 0}{pi}{sup 0}{gamma} decays with 1.1 &lt; m{sub K{sub S}{sup 0}{pi}{sup 0}} &lt; 1.8 GeV/c{sup 2} and find 59 {+-} 13 signal events with S{sub K{sub S}{sup 0}{pi}{sup 0}{gamma}} = 0.9 {+-} 1.0 {+-} 0.2 and C{sub K{sub S}{sup 0}{pi}{sup 0}{gamma}} = -1.0 {+-} 0.5 {+-} 0.2.
Date: July 12, 2005
Creator: Aubert, B.; Barate, R.; Boutigny, D.; Couderc, F.; Karyotakis, Y.; Lees, J. P. et al.
Partner: UNT Libraries Government Documents Department

Proposal to Study Multibody Final States in pp Collisions at 200 GeV/c Using the NAL 15-Foot Bubble Chamber

Description: We propose to expose the NAL 15-foot hydrogen bubble chamber to 200 GeV protons. We intend to take 20,000 pictures. Multiparticle final states will be studied by measuring the momenta of all charged final state particles with the exception of a few very fast tracks where at least the charge and the emission angle of the particle will be determined. Comparison with various models for high energy multiparticle production will be made. Additionally, K{sup o} and {Lambda} production will be studied as well as {pi}{sup o} production and the correlation between {pi}{sup o} and charged particles.
Date: October 27, 1972
Creator: Engelmann, R.; Lee-Franzini, J.; Moore, C.; Pratap, M. & /SUNY
Partner: UNT Libraries Government Documents Department

Gamma-Ray Emission From Crushed Clouds in Supernova Remnants

Description: It is shown that the radio and gamma-ray emission observed from newly-found 'GeV-bright' supernova remnants (SNRs) can be explained by a model, in which a shocked cloud and shock-accelerated cosmic rays (CRs) frozen in it are simultaneously compressed by the supernova blastwave as a result of formation of a radiative cloud shock. Simple reacceleration of pre-existing CRs is generally sufficient to power the observed gamma-ray emission through the decays of {pi}{sup 0}-mesons produced in hadronic interactions between high-energy protons (nuclei) and gas in the compressed-cloud layer. This model provides a natural account of the observed synchrotron radiation in SNRs W51C, W44 and IC 443 with flat radio spectral index, which can be ascribed to a combination of secondary and reaccelerated electrons and positrons.
Date: October 27, 2010
Creator: Uchiyama, Yasunobu; Blandford, Roger D.; Funk, Stefan; /SLAC; Tajima, Hiroyasu; /Nagoya U., Solar-Terrestrial Environ. Lab. et al.
Partner: UNT Libraries Government Documents Department

Observation of the decay B0bar -> LambdaC antiproton pi0

Description: In a sample of 467 million B{bar B} pairs collected with the BABAR detector at the PEP-II collider at SLAC we have observed the decay {bar B}{sup 0} {yields} {Lambda}{sub c}{sup +}{bar p}{pi}{sup 0} and measured the branching fraction to be (1.94 {+-} 0.17 {+-} 0.14 {+-} 0.50) x 10{sup -4}, where the uncertainties are statistical, systematic, and the uncertainty on the {Lambda}{sub c}{sup +} {yields} pK{sup -}{pi}{sup +} branching fraction, respectively. We determine an upper limit of 1.5 x 10{sup -6} at 90% C.L. for the product branching fraction {Beta}({bar B}{sup 0} {yields} {Sigma}{sub c}{sup +}(2455){bar p}) x {Beta}({Lambda}{sub c}{sup +} {yields} pK{sup -}{pi}{sup +}). Furthermore, we observe an enhancement at the threshold of the invariant mass of the baryon-antibaryon pair.
Date: August 26, 2010
Creator: Aubert, B.; Karyotakis, Y.; Lees, J.P.; Poireau, V.; Prencipe, E.; Prudent, X. et al.
Partner: UNT Libraries Government Documents Department

Measurement of the polarization parameter for the reaction $pi$$sup - $p$Yields$$pi$$sup 0$n between 1.03 and 1.79 GeV/c

Description: From 2nd international conference on elementary particles; Aixen- Provence, France (6 Sep 1973). Measurements of the polarization parameter for the reaction pi /sup -/p yields pi /sup o/n were made at the five momenta 1.03, 1.245, 1.44, 1.5 and 1.79 GeV/c. A polarized target was used, with polarizations achieved ranging from 48 to 57%. Salient features of the experiment were the use of neutron counters for time-of-flight measurements as well as angular information and the use of optical spark chambers, seven to eight radiation lengths thick, for the detection of the gamma rays from the decay of the pi /sup o/. The center-ofmass angular range covered by the 20 neutron counters was typically --.78 < cos THETA /sub c.m. <.87. For each momentum there are approximately 10,000 events which fit pi /sup -/p yields pi /sup o/ n with a confide nce level of at least 10%. (auth)
Date: September 1, 1973
Creator: Shannon, S.R.; Anderson, L.; Bridgewater, A.; Chaffee, R.; Chamberlain, O.; Dahl, O. et al.
Partner: UNT Libraries Government Documents Department