50 research outputs found
A search for the decay modes B+/- to h+/- tau l
We present a search for the lepton flavor violating decay modes B+/- to h+/-
tau l (h= K,pi; l= e,mu) using the BaBar data sample, which corresponds to 472
million BBbar pairs. The search uses events where one B meson is fully
reconstructed in one of several hadronic final states. Using the momenta of the
reconstructed B, h, and l candidates, we are able to fully determine the tau
four-momentum. The resulting tau candidate mass is our main discriminant
against combinatorial background. We see no evidence for B+/- to h+/- tau l
decays and set a 90% confidence level upper limit on each branching fraction at
the level of a few times 10^-5.Comment: 15 pages, 7 figures, submitted to Phys. Rev.
Evidence for an excess of B -> D(*) Tau Nu decays
Based on the full BaBar data sample, we report improved measurements of the
ratios R(D(*)) = B(B -> D(*) Tau Nu)/B(B -> D(*) l Nu), where l is either e or
mu. These ratios are sensitive to new physics contributions in the form of a
charged Higgs boson. We measure R(D) = 0.440 +- 0.058 +- 0.042 and R(D*) =
0.332 +- 0.024 +- 0.018, which exceed the Standard Model expectations by 2.0
sigma and 2.7 sigma, respectively. Taken together, our results disagree with
these expectations at the 3.4 sigma level. This excess cannot be explained by a
charged Higgs boson in the type II two-Higgs-doublet model. We also report the
observation of the decay B -> D Tau Nu, with a significance of 6.8 sigma.Comment: Expanded section on systematics, text corrections, improved the
format of Figure 2 and included the effect of the change of the Tau
polarization due to the charged Higg
Search for the decay modes D^0 → e^+e^-, D^0 → μ^+μ^-, and D^0 → e^±μ∓
We present searches for the rare decay modes D^0→e^+e^-, D^0→μ^+μ^-, and D^0→e^±μ^∓ in continuum e^+e^-→cc events recorded by the BABAR detector in a data sample that corresponds to an integrated luminosity of 468 fb^(-1). These decays are highly Glashow–Iliopoulos–Maiani suppressed but may be enhanced in several extensions of the standard model. Our observed event yields are consistent with the expected backgrounds. An excess is seen in the D^0→μ^+μ^- channel, although the observed yield is consistent with an upward background fluctuation at the 5% level. Using the Feldman–Cousins method, we set the following 90% confidence level intervals on the branching fractions: B(D^0→e^+e^-)<1.7×10^(-7), B(D^0→μ^+μ^-) within [0.6,8.1]×10^(-7), and B(D^0→e^±μ^∓)<3.3×10^(-7)
Study of the reaction e^{+}e^{-} -->J/psi\pi^{+}\pi^{-} via initial-state radiation at BaBar
We study the process with
initial-state-radiation events produced at the PEP-II asymmetric-energy
collider. The data were recorded with the BaBar detector at center-of-mass
energies 10.58 and 10.54 GeV, and correspond to an integrated luminosity of 454
. We investigate the mass
distribution in the region from 3.5 to 5.5 . Below 3.7
the signal dominates, and above 4
there is a significant peak due to the Y(4260). A fit to
the data in the range 3.74 -- 5.50 yields a mass value
(stat) (syst) and a width value (stat)(syst) for this state. We do not
confirm the report from the Belle collaboration of a broad structure at 4.01
. In addition, we investigate the system
which results from Y(4260) decay
Cracking the BAFF code.
The tumour necrosis factor (TNF) family members B cell activating factor (BAFF) and APRIL (a proliferation-inducing ligand) are crucial survival factors for peripheral B cells. An excess of BAFF leads to the development of autoimmune disorders in animal models, and high levels of BAFF have been detected in the serum of patients with various autoimmune conditions. In this Review, we consider the possibility that in mice autoimmunity induced by BAFF is linked to T cell-independent B cell activation rather than to a severe breakdown of B cell tolerance. We also outline the mechanisms of BAFF signalling, the impact of ligand oligomerization on receptor activation and the progress of BAFF-depleting agents in the clinical setting
Wnt signaling in triple-negative breast cancer
Wnt signaling regulates a variety of cellular processes, including cell fate, differentiation, proliferation and stem cell pluripotency. Aberrant Wnt signaling is a hallmark of many cancers. An aggressive subtype of breast cancer, known as triple-negative breast cancer (TNBC), demonstrates dysregulation in canonical and non-canonical Wnt signaling. In this review, we summarize regulators of canonical and non-canonical Wnt signaling, as well as Wnt signaling dysfunction that mediates the progression of TNBC. We review the complex molecular nature of TNBC and the emerging therapies that are currently under investigation for the treatment of this disease
Study of Bbar --> Xu l nubar decays in BBbar events tagged by a fully reconstructed B-meson decay and determination of |V_{ub}|
We report measurements of partial branching fractions for inclusive charmless
semileptonic B decays Bbar --> Xu l nubar, and the determination of the CKM
matrix element |V_{ub}|. The analysis is based on a sample of 467 million
Upsilon(4S) --> BBar decays recorded with the BaBar detector at the PEP-II e^+
e^- storage rings. We select events in which the decay of one of the B mesons
is fully reconstructed and an electron or a muon signals the semileptonic decay
of the other B meson. We measure partial branching fractions DeltaB in several
restricted regions of phase space and determine the CKM element |V_{ub}| based
on four different QCD predictions. For decays with a charged lepton momentum
p_l^* > 1.0 GeV in the B meson rest frame, we obtain DeltaB = (1.80 \pm 0.13
(stat.) \pm 0.15 (sys.) \pm 0.02 (theo.)) \times 10^{-3} from a fit to the
two-dimensional mX-q^2 distribution. Here, mX refers to the invariant mass of
the final state hadron X and q^2 is the invariant mass squared of the charged
lepton and neutrino. From this measurement we extract |V_{ub}| = (4.33\pm 0.24
(exp.) \pm 0.15 (theo.)) \times 10^{-3} as the arithmetic average of four
results obtained from four different QCD predictions of the partial rate. We
separately determine partial branching fractions for B^0 and B^- decays and
derive a limit on the isospin breaking in Bbar --> Xu l nubar decays.Comment: 26 pages, 9 postscript figures, 9 tables, accepted for publication in
PR
Search for the decay modes D0 -> e+e-, D0 -> mu+mu-, and D0 -> e mu
We present searches for the rare decay modes D0 to e+e-, D0 to mu+mu- and D0
to e mu in continuum e+e- to cbar c events recorded by the BABAR detector in a
data sample that corresponds to an integrated luminosity of 468 f^-1. These
decays are highly GIM suppressed but may be enhanced in several extensions of
the Standard Model. Our observed event yields are consistent with the expected
backgrounds. An excess is seen in the D0 to mu+mu- channel, although the
observed yield is consistent with an upward background fluctuation at the 5%
level. Using the Feldman-Cousins method, we set the following 90% confidence
level intervals on the branching fractions: B(D0 to e+e-)<1.7 x 10^-7, B(D0 to
mu+mu-) within [0.6, 8.1] x 10^-7, and B(D0 to e mu)<3.3 x 10^-7.Comment: 12 pages, 4 figures, submitted to PR
Search for the and states in and
We search for the and states, reported by the
Belle Collaboration, decaying to in the decays and where \chi_{c1} \to
\jpsi \gamma. The data were collected with the BaBar detector at the SLAC
PEP-II asymmetric-energy collider operating at center-of-mass energy
10.58 GeV, and correspond to an integrated luminosity of 429 fb. In this
analysis, we model the background-subtracted, efficiency-corrected
mass distribution using the mass distribution and the
corresponding normalized Legendre polynomial moments, and then test the
need for the inclusion of resonant structures in the description of the
mass distribution. No evidence is found for the
and resonances, and 90% confidence level upper limits on the
branching fractions are reported for the corresponding -meson decay modes.Comment: 15 pages, 12 postscript figures, to be published in Phys. Rev.