3,005 research outputs found
Charm Spectroscopy at BaBar
We present a mini-review on charm spectroscopy at the BaBar experiment. We
first report on the meson spectrum, and present precise measurements
of the meson as well as the properties of the many new states
discovered since 2003 (, , , and
mesons). We then discuss about charmed baryons observed recently
in the BaBar experiment: and baryons,
baryon and the baryons.Comment: 8 pages, to be published in the proceedings of the XII International
Conference on Hadron Spectroscopy held at INFN, Frascati, Italy between
October 8-13, 200
Measurement of the Branching Fractions of the Decays B -> Dbar^(*) D^(*) K
International audienceWe present a measurement of the branching fractions of the 22 decay channels B0 and B+ to Dbar^(*) D^(*) K, where Dbar^(*) and D^(*) are fully reconstructed. The B0 and B+ mesons are reconstructed in a sample of hadronic events for all the possible Dbar D K modes, namely B0 -> D^(*)- D^(*)0 K^+, D^(*)-D^(*)+ K^0, Dbar^(*)0 D^(*)0 K0 and B^+ -> Dbar^(*)0 D^(*)+ K0, Dbar^(*)0 D^(*)0 K+, D^(*)- D^(*)+ K+. The results are based on 423 fb-1 of data that contained 465 10^6 BBbar pairs collected at the Upsilon(4S) resonance with the BaBar detector at the PEP-II B factory
Search for supersymmetric particles assuming R-parity non-conservation in collisions at =192 to 208 GeV
A new look at the cosmic ray positron fraction
The positron fraction in cosmic rays was found to be a steadily increasing in
function of energy, above 10 GeV. This behaviour contradicts standard
astrophysical mechanisms, in which positrons are secondary particles, produced
in the interactions of primary cosmic rays during the propagation in the
interstellar medium. The observed anomaly in the positron fraction triggered a
lot of excitement, as it could be interpreted as an indirect signature of the
presence of dark matter species in the Galaxy. Alternatively, it could be
produced by nearby astrophysical sources, such as pulsars. Both hypotheses are
probed in this work in light of the latest AMS-02 positron fraction
measurements. The transport of the primary and secondary positrons in the
Galaxy is described using a semi-analytic two-zone model. MicrOMEGAs is used to
model the positron flux generated by dark matter species. The description of
the positron fraction from astrophysical sources is based on the pulsar
observations included in the ATNF catalogue. We find that the mass of the
favoured dark matter candidates is always larger than 500 GeV. The only dark
matter species that fulfils the numerous gamma ray and cosmic microwave
background bounds is a particle annihilating into four leptons through a light
scalar or vector mediator, with a mixture of tau (75%) and electron (25%)
channels, and a mass between 0.5 and 1 TeV. The positron anomaly can also be
explained by a single astrophysical source and a list of five pulsars from the
ATNF catalogue is given. Those results are obtained with the cosmic ray
transport parameters that best fit the B/C ratio. Uncertainties in the
propagation parameters turn out to be very significant. In the WIMP
annihilation cross section to mass plane for instance, they overshadow the
error contours derived from the positron data.Comment: 20 pages, 16 figures, accepted for publication in A&A, corresponds to
published versio
Observation of the Decay B^-→D_s^((*)+)K^-ℓ^-ν̅ _ℓ
We report the observation of the decay B^- → D_s^((*)+)K^-ℓ^-ν̅ _ℓ based on 342  fb^(-1) of data collected at the Υ(4S) resonance with the BABAR detector at the PEP-II e^+e^- storage rings at SLAC. A simultaneous fit to three D_s^+ decay chains is performed to extract the signal yield from measurements of the squared missing mass in the B meson decay. We observe the decay B^- → D_s^((*)+)K^-ℓ^-ν̅ _ℓ with a significance greater than 5 standard deviations (including systematic uncertainties) and measure its branching fraction to be B(B^- → D_s^((*)+)K^-ℓ^-ν̅ _ℓ)=[6.13_(-1.03)^(+1.04)(stat)±0.43(syst)±0.51(B(D_s))]×10^(-4), where the last error reflects the limited knowledge of the D_s branching fractions
Observation of the rare decay B+→K+π0π0 and measurement of the quasi-two-body contributions B+→K*(892)+π0, B+→f0(980)K+, and B+→χc0K+
We report an analysis of charmless hadronic decays of charged B mesons to the final state K+π0π0, using a data sample of (470.9±2.8)×106 BB̅ events collected with the BABAR detector at the Υ(4S) resonance. We observe an excess of signal events, with a significance above 10 standard deviations including systematic uncertainties, and measure the branching fraction and CP asymmetry to be B(B+→K+π0π0)=(16.2±1.2±1.5)×10-6 and ACP(B+→K+π0π0)=-0.06±0.06±0.04, where the uncertainties are statistical and systematic, respectively. Additionally, we study the contributions of the B+→K*(892)+π0, B+→f0(980)K+, and B+→χc0K+ quasi-two-body decays. We report the world’s best measurements of the branching fraction and CP asymmetry of the B+→K+π0π0 and B+→K*(892)+π0 channels
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