Search results for "annihilation"
showing 10 items of 1016 documents
A Study of Bose-Einstein Correlations In e+e- Annihilation At 91 Gev
1992
This paper describes a study of Bose-Einstein correlations made using the ALEPH detector at LEP. The correlations are found to enhance the two particle differential cross section for pairs of identical pions by a factor which can be roughly parametrized by R(Q) = 1 + lambda exp(-Q2-sigma(2)), where Q is the difference in the 3-momenta of the two pions in their centre of mass frame, lambda = 0.51 +/- 0.04 +/- 0.11 and sigma = 3.3 +/- 0.2 +/- 0.8 GeV-1, which corresponds to a source size of 0.65 +/- 0.04 +/- 0.16 fm. The large systematic errors on these results reflect their strong dependence on the choice of the reference sample used in the analysis. This problem is believed to occur primari…
Antiproton-proton annihilation at rest into two-body final states
1993
We report measurements of branching ratios for production of a series of two meson final states in $$\bar p$$ p annihilations at rest in liquid hydrogen. We find: $$\begin{gathered} BR(\bar pp \to \pi ^ + \pi ^ - ) = (3.07 \pm 0.13) \cdot 10^{ - 3} \hfill \\ BR(\bar pp \to K^ + K^ - ) = (0.99 \pm 0.05) \cdot 10^{ - 3} \hfill \\ BR(\bar pp \to \pi ^0 \pi ^0 ) = (6.93 \pm 0.43) \cdot 10^{ - 4} \hfill \\ BR(\bar pp \to \pi ^0 \eta ) = (2.12 \pm 0.12) \cdot 10^{ - 4} \hfill \\ BR(\bar pp \to \pi ^0 \omega ) = (5.73 \pm 0.47) \cdot 10^{ - 3} \hfill \\ BR(\bar pp \to \pi ^0 \eta ') = (1.23 \pm 0.13) \cdot 10^{ - 4} \hfill \\ BR(\bar pp \to \eta \eta ) = (1.64 \pm 0.10) \cdot 10^{ - 4} \hfill \\ B…
A study of tau decays involving eta and omega mesons
1997
The 132 pb(-1) of data collected by ALEPH from 1991 to 1994 have been used to analyze eta and omega production in 7 decays. The following branching fractions have been measured: B(tau(-) --> nu(tau)omega h(-)) = (1.91 +/- 0.07 +/- 0.06) x 10(-2), B(tau(-) --> nu(tau)omega h(-)pi(0)) = (4.3 +/- 0.6 +/- 0.5) x 10(-3), B(tau(-) --> nu(tau)eta K-) = (2.9(-1.2)(+1.3) +/- 0.7) x 10(-4), B(tau(-) --> nu(tau)eta(h)(-)pi(0)) = (1.8 +/- 0.4 +/- 0.2) x 10(-3) and the 95% C.L. limit B(tau(-) --> nu(tau)eta pi(-)) < 6.2 x 10(-4) has been obtained. The omega pi(-) and eta pi(-)pi(0) rates and dynamics are found in agreement with the predictions made from e(+)e(-) annihilation data with the help of isospi…
Antiproton-proton annihilation in-flight
1994
This is an overview of the preliminary results of\(\bar pp\) annihilation at incident\(\bar p\) momenta of 600, 1200 and 1940 MeV/c(*). The data was taken at LEAR with the Crystal Barrel Detector (E. Akeret al.:Nucl. Instrum. Methods A,321, 108 (1992)). In the two pseudoscalar final states seven different channels are observable and their angular distributions are measured. They are compared to older data, if existent, and are found to be equal within the experimental errors. In the three-meson final states, an overview of the already examined final states is given. Striking signals in the Dalitz plots and invariant-mass projections for a set of final states are observed. In the final state…
Search for a Low-Mass Higgs Boson inΥ(3S)→γA0,A0→τ+τ−atBABAR
2009
We search for a light Higgs boson, $A^0$, in the radiative decay $\Upsilon(3S)\to\gamma A^0$, $A^0\to\tau^+\tau^-$, $\tau^+\to e^+\nu_e \overline{\nu}_{\tau}$ or $\tau^+\to \mu^+ \nu_{\mu} \overline{\nu}_{\tau}$. The data sample contains 122 million $\Upsilon(3S)$ events recorded with the \babar detector. We find no evidence for a narrow structure in the studied $\tau^+\tau^-$ invariant mass region of $4.03(1.5-16)\times 10^{-5}$ across the $m_{\tau^+\tau^-}$ range. We also set a 90% C.L. upper limit on the $\tau^+\tau^-$-decay of the $\eta_b$ at ${\mathcal{B}}(\eta_b\to \tau^+\tau^-)<8%$.
Search forD0−D¯0Mixing and a Measurement of the Doubly Cabibbo-Suppressed Decay Rate inD0→KπDecays
2003
The authors present a search for D{sup 0}-{bar D}{sup 0} mixing using regions of phase space in which the rate of doubly Cabibbo-suppressed decays D{sup 0} {yields} K{sup +}{pi}{sup -}{pi}{sup 0} relative to Cabibbo-favored decays D{sup 0} {yields} K{sup -} {pi}{sup +}{pi}{sup 0} is reduced. They analyze 230.4 fb{sup -1} of data collected with the BABAR detector at the PEP-II e{sup +}e{sup -} collider at SLAC. They present results with and without the assumption of CP conservation. Assuming CP conservation, they measure the time-integrated mixing rate R{sub M} = (0.023{sub -0.014}{sup +0.018}(stat.) {+-} 0.004(syst.))%, and R{sub M} < 0.054% at the 95% confidence level. They find that the d…
Branching Fractions andCPAsymmetries inB0→π0π0,B+→π+π0, andB+→K+π0Decays and Isospin Analysis of theB→ππSystem
2005
We measure the branching fractions and CP asymmetries in the decays B0-->K(+)K(-)K(0)(S) and B+-->K(+)K(0)(S)K(0)(S) using a sample of approximately 122x10(6) BB pairs collected by the BABAR detector. From a time-dependent analysis of the K(+)K(-)K(0)(S) sample that excludes phiK(0)(S), the values of the CP-violation parameters are S=-0.56+/-0.25+/-0.04 and C=-0.10+/-0.19+/-0.10, where the first uncertainty is statistical and the second is systematic. We confirm that the final state is nearly purely CP even and extract the standard model parameter sin(2beta=0.57+/-0.26+/-0.04(+0.17)(-0) where the last error is due to uncertainty on the CP content. We present the first measurement of the CP-…
Evidence for the direct two-photon transition from ψ(3686) to J/ψ.
2012
The two-photon transition ψ(3686)→γγJ/ψ is studied in a sample of 1.06×10(8) ψ(3686) decays collected by the BESIII detector. The branching fraction is measured to be (3.1±0.6(stat)(-1.0)(+0.8)(syst))×10(-4) using J/ψ→e(+)e(-) and J/ψ→μ(+)μ(-) decays, and its upper limit is estimated to be 4.5×10(-4) at the 90% confidence level. This work represents the first measurement of a two-photon transition among charmonium states. The orientation of the ψ(3686) decay plane and the J/ψ polarization in this decay are also studied. In addition, the product branching fractions of sequential E1 transitions ψ(3686)→γχ(cJ) and χ(cJ)→γJ/ψ(J=0,1,2) are reported.
Study ofCPAsymmetry inB0−B¯0Mixing with Inclusive Dilepton Events
2015
We present a measurement of the asymmetry A_{CP} between same-sign inclusive dilepton samples l^{+}l^{+} and l^{-}l^{-} (l=e, μ) from semileptonic B decays in ϒ(4S)→BB[over ¯] events, using the complete data set recorded by the BABAR experiment near the ϒ(4S) resonance, corresponding to 471×10^{6} BB[over ¯] pairs. The asymmetry A_{CP} allows comparison between the mixing probabilities P(B[over ¯]^{0}→B^{0}) and P(B^{0}→B[over ¯]^{0}), and therefore probes CP and T violation. The result, A_{CP}=[-3.9±3.5(stat)±1.9(syst)]×10^{-3}, is consistent with the standard model expectation.
Production ofK 0 and Λ in hadronic Z decays
1994
Measurements of the inclusive cross-sections forK 0 and Λ production in hadronic decays of the Z are presented together with measurements of two-particle correlations within pairs of Λ andK 0. The results are compared with predictions from the hadronization models Jetset, based on string fragmentation, and Herwig, based on cluster decays. TheK 0 spectrum is found to be harder than predicted by both models, while the Λ spectrum is softer than predicted. The correlation measurements are all reproduced well by Jetset, while Herwig misses some of the qualitative features and overestimates the size of the $$\Lambda \bar \Lambda $$ correlation. Finally, the possibility of Bose-Einstein correlatio…