Search results for "decay"
showing 10 items of 2087 documents
Measurement of branching fractions for D meson decaying into $ϕ$ meson and a pseudoscalar meson
2019
The four decay modes D0→ϕπ0, D0→ϕη, D+→ϕπ+, and D+→ϕK+ are studied by using a data sample taken at the centre-of-mass energy s=3.773 GeV with the BESIII detector, corresponding to an integrated luminosity of 2.93 fb$^{−1}$. The branching fractions of the first three decay modes are measured to be B(D0→ϕπ0)=(1.168±0.028±0.028)×10−3, B(D0→ϕη)=(1.81±0.46±0.06)×10−4, and B(D+→ϕπ+)=(5.70±0.05±0.13)×10−3, respectively, where the first uncertainties are statistical and the second are systematic. In addition, the upper limit of the branching fraction for D+→ϕK+ is given to be 2.1×10−5 at the 90% confidence level. The ratio of B(D0→ϕπ0) to B(D+→ϕπ+) is calculated to be (20.49±0.50±0.45)%, which is c…
Measurement of the radiative K-e3 branching ratio
2005
We present a measurement of the relative branching ratio of the decay KL -> pi e nu gamma (Ke3gamma) with respect to KL-> pi e nu (gamma) (Ke3+Ke3gamma) decay. The result is based on observation of 19 000 Ke3gamma and 5.6 x 10^6 Ke3 decays. The value of the branching ratio is Br(Ke3gamma, Egamma^*>30 MeV,theta(e,gamma)^*>20^o)/Br(Ke3)= (0.964+-0.008+0.011-0.009)%. This result agrees with theoretical predictions but is at variance with a recently published result.
Study of the electromagnetic background in the XENON100 experiment
2011
The XENON100 experiment, located at the Laboratori Nazionali del Gran Sasso (LNGS), aims to directly detect dark matter in the form of Weakly Interacting Massive Particles (WIMPs) via their elastic scattering off xenon nuclei. We present a comprehensive study of the predicted electronic recoil background coming from radioactive decays inside the detector and shield materials, and intrinsic contamination. Based on GEANT4 Monte Carlo simulations using a detailed geometry together with the measured radioactivity of all detector components, we predict an electronic recoil background in the WIMP-search energy range (0-100 keV) in the 30 kg fiducial mass of less than 10e-2 events/(kg-day-keV), co…
Search for the dark photon in π0 decays
2015
A sample of $1.69\times 10^7$ fully reconstructed $\pi^0\to\gamma e^+e^-$ decay candidates collected by the NA48/2 experiment at CERN in 2003--2004 is analysed to search for the dark photon ($A'$) production in the $\pi^0\to\gamma A'$ decay followed by the prompt $A'\to e^+e^-$ decay. No signal is observed, and an exclusion region in the plane of the dark photon mass $m_{A'}$ and mixing parameter $\varepsilon^2$ is established. The obtained upper limits on $\varepsilon^2$ are more stringent than the previous limits in the mass range $9~{\rm MeV}/c^2<m_{A'}<70~{\rm MeV}/c^2$. The NA48/2 sensitivity to the dark photon production in the $K^\pm\to\pi^\pm A'$ decay is also evaluated.
Observation of orbitally excited B mesons
1995
Experimental evidence for the existence of orbitally excited B meson states is presented in an analysis of the BÏ and B*Ï distribution of Q = m(B**) - m(B(*)) - m(Ï) using Z0decay data taken with the DELPHI detector at LEP. The mean Q-value of the decays B**â B(*)Ï is measured to be 284 ± 5 (stat.) ± 15 (syst.) MeV/c2, and the Gaussian width of the signal is 79 ± 5 (stat.) ± 8 (syst.) MeV/c2. This signal can be described as a single resonance of mass m = 5732 ± 5 (stat.) ± 20 (syst.) MeV/c2and full width Î = 145 ± 28 MeV/c2. The observed shape is also consistent with the production of several broad and narrow states as predicted by the quark model and partly observed in the D-…
Angular distributions in the decay B -> K*l(+)l(-)
2009
We use a sample of 384 million BBbar events collected with the Babar detector at the PEP-II e+e- collider to study angular distributions in the rare decays B -> K* l+l-, where l+l- is either e+e- or mu+mu-. For low dilepton invariant masses, m(l+l-)3.2$ GeV/c^2, we measure AFB=0.76 (+0.52,-0.32) +/- 0.07 FL=0.71 (+0.20,-0.22) +/- 0.04.
Partial wave analysis of ψ(2S)→ppˉη
2013
Using a sample of 1.06 x 10(8) psi(2) events collected with the BESIII detector at BEPCII, the decay psi(2S) -> p (p) over bar eta is studied. A partial wave analysis determines that the intermediate state N(1535) with a mass of 1524 +/- 5(-4)(+10) MeV/c(2) and a width of 130(-24-10)(+27+57) MeV/c(2) is dominant in the decay; the product branching fraction is determined to be B(psi(2S) -> N(1535)(p) over bar x B(N(1535) -> p eta + c.c. = 5.2 +/- 0.3(-1.2)(+3.2)) x 10(-5). Furthermore, the branching fraction of psi(2S) -> p (p) over bar eta is measured to be (6.4 +/- 0.2 +/- 0.6) x 10(-5). Here, the first error is statistical and the second is systematic.
Sizeable beta-strength in $^{31}$Ar (β3p) decay
2014
5 pags. ; 7 figs. ; Open Access funded by SCOAP3 - Sponsoring Consortium for Open Access Publishing in Particle Physics
Multiplicity fluctuations in hadronic final states from the decay of the Z0
1992
An analysis of the fluctuations in the phase space distribution of hadrons produced in the decay of 78829 Z0 has been carried out, using the method of factorial moments. The high statistics collected by the DELPHI experiment at LEP during 1990 allowed studies of the event sample both globally and in intervals of p(t) and multiplicity, and for different jet topologies and for single jets. A large contribution to the factorial moments of the one-dimensional data on rapidity with respect to the event axis comes from hard gluons. Details of factorial moments in two and three dimensions are presented. Influences of resonance decays have been studied by Monte Carlo simulation: one-dimensional fac…
Beta-decay of148,150,152Pr into levels of148,150,152Nd
1988
Theβ−-decay of148,150,152Pr into levels of148,150,152Nd has been studied byγ-singles,γγ-coincidence and for148Pr also byγγ-angular correlation measurements. The praseodymium activities have been obtained by thermal neutron-induced fission of235U followed by on-line mass separation with the helium-jet coupled mass separator HELIOS. Decay schemes for these heaviest praseodymium nuclides are proposed. From the angular correlation measurements spin values for the seven lowest levels of148Nd are deduced. Spin and parity assignments for the lower levels in150,152Nd have been extrapolated from level systematics.