Several charmonium-like states above
D
D
¯
threshold have been discovered at the Belle and
BaBar B
-factories. Some are produced via Initial State Radiation (e.g.
Y
(
4260
)
and
Y
(
4350
)
), and ...some are observed in
B meson decays (e.g.
X
(
3872
)
,
Y
(
3940
)
, and
Z
(
4430
)
−
). The
Z
(
4430
)
−
state has generated a great deal of interest, having minimum quark content
(
c
c
¯
d
u
¯
)
and, thus, representing the unequivocal manifestation of a four-quark meson state. Here we summarize recent
BaBar
results on the
Y
(
4260
)
,
X
(
3872
)
,
Y
(
3940
)
, and on a search for the
Z
(
4430
)
−
.
The process e+e−→π+π−2π0γ is investigated by means of the initial-state radiation technique, where a photon is emitted from the incoming electron or positron. Using 454.3 fb−1 of data collected ...around a center-of-mass energy of s=10.58 GeV by the BABAR experiment at SLAC, approximately 150000 signal events are obtained. The corresponding nonradiative cross section is measured with a relative uncertainty of 3.6% in the energy region around 1.5 GeV, surpassing all existing measurements in precision. Using this new result, the channel’s contribution to the leading order hadronic vacuum polarization contribution to the anomalous magnetic moment of the muon is calculated as (gμπ+π−2π0−2)/2=(17.9±0.1stat±0.6syst)×10−10 in the energy range 0.85 GeV<ECM<1.8 GeV. In the same energy range, the impact on the running of the fine-structure constant at the Z0-pole is determined as Δαπ+π−2π0(MZ2)=(4.44±0.02stat±0.14syst)×10−4. Furthermore, intermediate resonances are studied and especially the cross section of the process e+e−→ωπ0→π+π−2π0 is measured.
The decay τ−→K−KSντ has been studied using 430×106 e+e−→τ+τ− events produced at a center-of-mass energy around 10.6 GeV at the PEP-II collider and studied with the BABAR detector. The mass spectrum ...of the K−KS system has been measured and the spectral function has been obtained. The measured branching fraction B(τ−→K−KSντ)=(0.739±0.011(stat)±0.020(syst))×10−3 is found to be in agreement with earlier measurements.
We present a search for nine lepton-number-violating and three lepton-flavor-violating neutral charm decays of the type D0→h′−h−ℓ′+ℓ+ and D0→h′−h+ℓ′±ℓ∓, where h and h′ represent a K or π meson and ℓ ...and ℓ′ an electron or muon. The analysis is based on 468 fb−1 of e+e− annihilation data collected at or close to the ϒ(4S) resonance with the BABAR detector at the SLAC National Accelerator Laboratory. No significant signal is observed for any of the twelve modes, and we establish 90% confidence level upper limits on the branching fractions in the range (1.0–30.6)×10−7. The limits are between 1 and 3 orders of magnitude more stringent than previous measurements.
A validated postal questionnaire has been used to establish the prevalence of dyspeptic symptoms in five geographical locations from the south coast of England to the north of Scotland. The six month ...period prevalence of dyspepsia in the 7428 respondents to the questionnaire is 41% and equal between the sexes, with similar prevalence rates in the centres studied. There is considerable overlap between upper abdominal symptoms and symptoms of heartburn; 56% of patients with dyspepsia experience both groups of symptoms. Symptom frequency falls progressively with age in men and women, but the proportion of people seeking medical advice for dyspepsia rises with age. One quarter of the dyspeptic patients studied have consulted a general practitioner about their symptoms. This study suggests that the prevalence of dyspepsia in the community has changed little over the last 30 years, despite evidence that the frequency of peptic ulcer disease is falling. Symptom prevalence is unrelated to social class, but this factor is associated with consultation behaviour, the consultation rate rising from 17% in social class 1 to 29% in social class 4. The use of investigations--barium meal and endoscopy--is similarly related to social class; the lowest rate for ulcer diagnosis (4.7%) is found in social class 1 and the highest (17.1%) in social class 5.
We report the observation of the rare charm decay D0→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/c2 of the electron-positron pair to be B(D0→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 D0→K−π+π+π− used as a normalization mode. The significance of the observation corresponds to 9.7 standard deviations including systematic uncertainties. This result is consistent with the recently reported D0→K−π+μ+μ− branching fraction, measured in the same invariant mass range, and with the value expected in the standard model. In a set of regions of m(e+e−), where long-distance effects are potentially small, we determine a 90% confidence level upper limit on the branching fraction B(D0→K−π+e+e−)<3.1×10−6.
We propose a simple explanation for the increase of approximately 3 MeV/c;{2} in the mass value of the X(3872) obtained from D(*0)D(0) decay relative to that obtained from decay to J/psipi(+)pi(-). ...If the total width of the X(3872) is 2-3 MeV, the peak position in the D(*0)D(0) invariant mass distribution is sensitive to the final state orbital angular momentum because of the proximity of the X(3872) to D(*0)D(0) threshold. We show that for total width 3 MeV and one unit of orbital angular momentum, a mass shift approximately 3 MeV/c(2) is obtained; experimental mass resolution should slightly increase this value. A consequence is that spin-parity 2(-) is favored for the X(3872).
We propose a simple explanation for the increase of approximately 3 MeV/c{sup 2} in the mass value of the X(3872) obtained from D*{sup 0}D{sup 0} decay relative to that obtained from decay to ...J/{psi}{pi}{sup +}{pi}{sup -}. If the total width of the X(3872) is 2-3 MeV, the peak position in the D*{sup 0}D{sup 0} invariant mass distribution is sensitive to the final state orbital angular momentum because of the proximity of the X(3872) to D*{sup 0}D{sup 0} threshold. We show that for total width 3 MeV and one unit of orbital angular momentum, a mass shift {approx}3 MeV/c{sup 2} is obtained; experimental mass resolution should slightly increase this value. A consequence is that spin-parity 2{sup -} is favored for the X(3872)
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