Search results for "Invariant"
showing 10 items of 783 documents
Observation of the Decay D0→K−π+e+e−
2019
We report the observation of the rare charm decay D^{0}→K^{-}π^{+}e^{+}e^{-}, based on 468 fb^{-1} of e^{+}e^{-} annihilation data collected at or close to the center-of-mass energy of the ϒ(4S) resonance with the BABAR detector at the SLAC National Accelerator Laboratory. We find the branching fraction in the invariant mass range 0.675<m(e^{+}e^{-})<0.875 GeV/c^{2} of the electron-positron pair to be B(D^{0}→K^{-}π^{+}e^{+}e^{-})=(4.0±0.5±0.2±0.1)×10^{-6}, where the first uncertainty is statistical, the second systematic, and the third due to the uncertainty in the branching fraction of the decay D^{0}→K^{-}π^{+}π^{+}π^{-} used as a normalization mode. The significance of the observation…
Observation of a Narrow Meson State Decaying toDs+π0at a Mass of2.32 GeV/c2
2003
We have observed a narrow state near 2.32 GeV/c(2) in the inclusive D(+)(s)pi(0) invariant mass distribution from e(+)e(-) annihilation data at energies near 10.6 GeV. The observed width is consistent with the experimental resolution. The small intrinsic width and the quantum numbers of the final state indicate that the decay violates isospin conservation. The state has natural spin-parity and the low mass suggests a J(P)=0(+) assignment. The data sample corresponds to an integrated luminosity of 91 fb(-1) recorded by the BABAR detector at the SLAC PEP-II asymmetric-energy e(+)e(-) storage ring.
P̅P annihilation at rest: annihilation dynamics and meson spectroscopy
1990
Proton-antiproton annihilations provide an excellent tool to study the dynamics of quarks and gluons in the confinement region. Annihilations at rest into two mesons show selection rules which can be related to symmetries between SU(3) invariant amplitudes. In the annihilation process not only conventional (q\(\bar{\text{q}}\)) mesons are produced but also states which do not fit into the meson nonets. It is shown how knowledge of the atomic state of the pp system at annihilation can be used to restrict the possible quantum numbers of meson resonances.
The radiative return at small angles: virtual corrections
2002
Virtual corrections for electron--positron annihilation into one real and one off-shell photon of invariant mass Q^2 are evaluated. Special attention is paid to those configurations where the real photon is collinear with the beam direction. This calculation is an important ingredient of a Monte Carlo program, which simulates events with tagged photons from initial-state radiation, including NLO corrections.
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…
Electroweak baryogenesis and dark matter from a singlet Higgs
2012
If the Higgs boson H couples to a singlet scalar S via lambda_m |H|^2 S^2, a strong electroweak phase transition can be induced through a large potential barrier that exists already at zero temperature. In this case properties of the phase transition can be computed analytically. We show that electroweak baryogenesis can be achieved using CP violation from a dimension-6 operator that couples S to the top-quark mass, suppressed by a new physics scale that can be well above 1 TeV. Moreover the singlet is a dark matter candidate whose relic density is < 3% of the total dark matter density, but which nevertheless interacts strongly enough with nuclei (through Higgs exchange) to be just below…
Vusandmsfrom HadronicτDecays
2005
Recent experimental results on hadronic $\ensuremath{\tau}$ decays into strange particles by the OPAL Collaboration are employed to determine ${V}_{us}$ and ${m}_{s}$ from moments of the invariant mass distribution. Our results are ${V}_{us}=0.2208\ifmmode\pm\else\textpm\fi{}0.0034$ and ${m}_{s}(2\text{ }\text{ }\mathrm{G}\mathrm{e}\mathrm{V})=81\ifmmode\pm\else\textpm\fi{}22\text{ }\text{ }\mathrm{M}\mathrm{e}\mathrm{V}$. The error on ${V}_{us}$ is dominated by experiment and should be improvable in the future. Nevertheless, already now our result is competitive with the standard extraction of ${V}_{us}$ from ${K}_{e3}$ decays, and it is compatible with unitarity.
Simultaneous description of the e+e−→J/ψππ(KK¯) processes
2020
In this work, we provide a simultaneous and accurate description of the ${\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ and ${\ensuremath{\pi}}^{\ifmmode\pm\else\textpm\fi{}}J/\ensuremath{\psi}$ invariant mass distributions of the recent BESIII data on ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}J/\ensuremath{\psi}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$, together with the ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}J/\ensuremath{\psi}{K}^{+}{K}^{\ensuremath{-}}$ cross sections at ${e}^{+}{e}^{\ensuremath{-}}$ center-of-mass energies $q=4.23\text{ }\text{ }\mathrm{GeV}$ and $q=4.26\text{ }\text{ }\mathrm{GeV}$. The rescattering effects between p…
SU(2)×U(1)Gauge Invariance and the Shape of New Physics in RareBDecays
2014
New physics effects in B decays are routinely modeled through operators invariant under the strong and electromagnetic gauge symmetries. Assuming the scale for new physics is well above the electroweak scale, we further require invariance under the full standard model gauge symmetry group. Retaining up to dimension-six operators, we unveil new constraints between different new physics operators that are assumed to be independent in the standard phenomenological analyses. We illustrate this approach by analyzing the constraints on new physics from rare B(q) (semi-)leptonic decays.
Search fortbResonances in Proton-Proton Collisions ats=7 TeVwith the ATLAS Detector
2012
This Letter presents a search for tb resonances in 1.04 fb(-1) of LHC proton-proton collision data collected by the ATLAS detector at a center-of-mass energy of 7 TeV. Events with a lepton, missing transverse momentum, and two jets are selected and the invariant mass of the corresponding final state is reconstructed. The search exploits the shape of the tb invariant mass distribution compared to the expected standard model backgrounds. The model of a right-handed W(R)' with standard model-like couplings is chosen as the benchmark model for this search. No statistically significant excess of events is observed in the data, and upper limits on the cross section times the branching ratio of W(…