3,028 research outputs found
Search for B+ →μ+νμ and B+ →μ+N with inclusive tagging
We report the result for a search for the leptonic decay of B+→μ+νμ using the full Belle dataset of 711 fb-1 of integrated luminosity at the (4S) resonance. In the Standard Model leptonic B-meson decays are helicity and Cabibbo-Kobayashi-Maskawa suppressed. To maximize sensitivity an inclusive tagging approach is used to reconstruct the second B meson produced in the collision. The directional information from this second B meson is used to boost the observed μ into the signal B-meson rest frame, in which the μ has a monochromatic momentum spectrum. Though its momentum is smeared by the experimental resolution, this technique improves the analysis sensitivity considerably. Analyzing the μ momentum spectrum in this frame we find B(B+→μ+νμ)=(5.3±2.0±0.9)×10-7 with a one-sided significance of 2.8 standard deviations over the background-only hypothesis. This translates to a frequentist upper limit of B(B+→μ+νμ)<8.6×10-7 at 90% confidence level. The experimental spectrum is then used to search for a massive sterile neutrino, B+→μ+N, but no evidence is observed for a sterile neutrino with a mass in a range of 0-1.5 GeV. The determined B+→μ+νμ branching fraction limit is further used to constrain the mass and coupling space of the type II and type III two-Higgs-doublet models. © 2020 authors. Published by the American Physical Society
Les Houches 2013: Physics at TeV Colliders: Standard Model Working Group Report
This Report summarizes the proceedings of the 2013 Les Houches workshop on
Physics at TeV Colliders. Session 1 dealt primarily with (1) the techniques for
calculating standard model multi-leg NLO and NNLO QCD and NLO EW cross sections
and (2) the comparison of those cross sections with LHC data from Run 1, and
projections for future measurements in Run 2.Comment: Proceedings of the Standard Model Working Group of the 2013 Les
Houches Workshop, Physics at TeV Colliders, Les houches 3-21 June 2013. 200
page
Search for Axionlike Particles Produced in e+e- Collisions at Belle II
© 2020 authors. Published by the American Physical Society. Published by the American Physical Society under the terms of the https://creativecommons.org/licenses/by/4.0/ Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article\u27s title, journal citation, and DOI. Funded by SCOAP3. We present a search for the direct production of a light pseudoscalar a decaying into two photons with the Belle II detector at the SuperKEKB collider. We search for the process e+e-→γa, a→γγ in the mass range 0.
Measurement of the integrated luminosity of the Phase 2 data of the Belle II experiment
© 2019 Chinese Physical Society and the Institute of High Energy Physics of the Chinese Academy of Sciences and the Institute of Modern Physics of the Chinese Academy of Sciences and IOP Publishing Ltd. From April to July 2018, a data sample at the peak energy of the γ(4S) resonance was collected with the Belle II detector at the SuperKEKB electron-positron collider. This is the first data sample of the Belle II experiment. Using Bhabha and digamma events, we measure the integrated luminosity of the data sample to be (496.3 ± 0.3 ± 3.0) pb-1, where the first uncertainty is statistical and the second is systematic. This work provides a basis for future luminosity measurements at Belle II
Measurement of ISR-FSR interference in the processes e+ e- --> mu+ mu- gamma and e+ e- --> pi+ pi- gamma
Charge asymmetry in processes e+ e- --> mu+ mu- gamma and e+ e- --> pi+ pi-
gamma is measured using 232 fb-1 of data collected with the BABAR detector at
center-of-mass energies near 10.58 GeV. An observable is introduced and shown
to be very robust against detector asymmetries while keeping a large
sensitivity to the physical charge asymmetry that results from the interference
between initial and final state radiation. The asymmetry is determined as
afunction of the invariant mass of the final-state tracks from production
threshold to a few GeV/c2. It is compared to the expectation from QED for e+ e-
--> mu+ mu- gamma and from theoretical models for e+ e- --> pi+ pi- gamma. A
clear interference pattern is observed in e+ e- --> pi+ pi- gamma, particularly
in the vicinity of the f_2(1270) resonance. The inferred rate of lowest order
FSR production is consistent with the QED expectation for e+ e- --> mu+ mu-
gamma, and is negligibly small for e+ e- --> pi+ pi- gamma.Comment: 32 pages,29 figures, to be submitted to Phys. Rev.
Measurement of CP Asymmetries and Branching Fractions in Charmless Two-Body B-Meson Decays to Pions and Kaons
We present improved measurements of CP-violation parameters in the decays
, , and , and of
the branching fractions for and . The
results are obtained with the full data set collected at the
resonance by the BABAR experiment at the PEP-II asymmetric-energy factory
at the SLAC National Accelerator Laboratory, corresponding to
million pairs. We find the CP-violation parameter values and
branching fractions where in each case, the first uncertainties are statistical
and the second are systematic. We observe CP violation with a significance of
6.7 standard deviations for and 6.1 standard deviations for
, including systematic uncertainties. Constraints on the
Unitarity Triangle angle are determined from the isospin relations
among the rates and asymmetries. Considering only the solution
preferred by the Standard Model, we find to be in the range
at the 68% confidence level.Comment: 18 pages, 11 postscript figures, submitted to Phys. Rev.
B →Vℓ+ℓ− in the Standard Model from light-cone sum rules
We present , , , and
form factors from light-cone sum rules (LCSR) at
for twist-2 and 3 and for
twist-4 with updated hadronic input parameters. Three asymptotic light-cone
distribution amplitudes of twist- (and ) are determined, necessary for
the form factors to obey the equations of motion. It is argued that the latter
constrain the uncertainty of tensor-to-vector form factor ratios thereby
improving the prediction of zeros of helicity amplitudes of major importance
for angular observables. We provide easy-to-use fits to the
LCSR results, including the full error correlation matrix, in all modes at low
as well as combined fits to LCSR and lattice results covering the entire
kinematic range for , and . The error
correlation matrix avoids the problem of overestimating the uncertainty in
phenomenological applications. Using the new form factors and recent
computations of non-factorisable contributions we provide Standard Model
predictions for as well as and
at low dilepton invariant mass. Employing our form factor results we extract the CKM element
from the semileptonic decays and
find good agreement with other exclusive determinations.Comment: 64 pages, 7 figures, 15 tables. v3: Minor clarifications, numerics
unchanged. Matches version published in JHE
Recommended from our members
Measurement of B(B-->X_s {\gamma}), the B-->X_s {\gamma} photon energy spectrum, and the direct CP asymmetry in B-->X_{s+d} {\gamma} decays
The photon spectrum in B --> X_s {\gamma} decay, where X_s is any strange
hadronic state, is studied using a data sample of (382.8\pm 4.2) \times 10^6
e^+ e^- --> \Upsilon(4S) --> BBbar events collected by the BABAR experiment at
the PEP-II collider. The spectrum is used to measure the branching fraction B(B
--> X_s \gamma) = (3.21 \pm 0.15 \pm 0.29 \pm 0.08)\times 10^{-4} and the
first, second, and third moments = 2.267 \pm 0.019 \pm 0.032 \pm
0.003 GeV,, )^2> = 0.0484 \pm 0.0053 \pm 0.0077 \pm
0.0005 GeV^2, and )^3> = -0.0048 \pm 0.0011 \pm 0.0011
\pm 0.0004 GeV^3, for the range E_\gamma > 1.8 GeV, where E_{\gamma} is the
photon energy in the B-meson rest frame. Results are also presented for
narrower E_{\gamma} ranges. In addition, the direct CP asymmetry A_{CP}(B -->
X_{s+d} \gamma) is measured to be 0.057 \pm 0.063. The spectrum itself is also
unfolded to the B-meson rest frame; that is the frame in which theoretical
predictions for its shape are made.Comment: 37 pages, 19 postscript figures, submitted to Phys. Rev. D. No
analysis or results have changed from previous version. Some changes to
improve clarity based on interactions with Phys. Rev. D referees, including
one new Figure (Fig. 13), and some minor wording/punctuation/spelling
mistakes fixe
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Precise Measurement of the e+ e- --> pi+ pi- (gamma) Cross Section with the Initial-State Radiation Method at BABAR
A precise measurement of the cross section of the process
from threshold to an energy of 3GeV is obtained
with the initial-state radiation (ISR) method using 232fb of data
collected with the BaBar detector at center-of-mass energies near
10.6GeV. The ISR luminosity is determined from a study of the leptonic process
, which is found to agree with the
next-to-leading-order QED prediction to within 1.1%. The cross section for the
process is obtained with a systematic uncertainty
of 0.5% in the dominant resonance region. The leading-order hadronic
contribution to the muon magnetic anomaly calculated using the measured
cross section from threshold to 1.8GeV is .Comment: 58 pages, 56 figures, to be submitted to Phys. Rev.
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